Perturbations in the p53/miR-34a/SIRT1 pathway in the R6/2 Huntington's disease model Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-12-28 Regina Hertfelder Reynolds, Maria Hvidberg Petersen, Cecilie Wennemoes Willert, Marie Heinrich, Nynne Nymann, Morten Dall, Jonas T. Treebak, Maria Björkqvist, Asli Silahtaroglu, Lis Hasholt, Anne Nørremølle
Epigenetic regulation in medulloblastoma Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-12-18 Jiaqing Yi, Jiang Wu
Medulloblastoma is the most common malignant childhood brain tumor. The heterogeneous tumors are classified into four subgroups based on transcription profiles. Recent developments in genome-wide sequencing techniques have rapidly advanced the understanding of these tumors. The high percentages of somatic alterations of genes encoding chromatin regulators in all subgroups suggest that epigenetic deregulation is a major driver of medulloblastoma. In this report, we review the current understanding of epigenetic regulation in medulloblastoma with a focus on the functional studies of chromatin regulators in the initiation and progression of specific subgroups of medulloblastoma. We also discuss the potential usage of epigenetic inhibitors for medulloblastoma treatment.
The role of ISWI chromatin remodeling complexes in brain development and neurodevelopmental disorders Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-12-15 Laura R. Goodwin, David J. Picketts
The mammalian ISWI (Imitation Switch) genes SMARCA1 and SMARCA5 encode the ATP-dependent chromatin remodeling proteins SNF2L and SNF2H. The ISWI proteins interact with BAZ (bromodomain adjacent to PHD zinc finger) domain containing proteins to generate eight distinct remodeling complexes. ISWI complex-mediated nucleosome positioning within genes and gene regulatory elements is proving important for the transition from a committed progenitor state to a differentiated cell state. Genetic studies have implicated the involvement of many ATP-dependent chromatin remodeling proteins in neurodevelopmental disorders (NDDs), including SMARCA1. Here we review the characterization of mice inactivated for ISWI and their interacting proteins, as it pertains to brain development and disease. A better understanding of chromatin dynamics during neural development is a prerequisite to understanding disease pathologies and the development of therapeutics for these complex disorders.
Epigenetic crosstalk: Pharmacological inhibition of HDACs can rescue defective synaptic morphology and neurotransmission phenotypes associated with loss of the chromatin reader Kismet Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-12-15 Nina K. Latcheva, Jennifer M. Viveiros, Edward A. Waddell, Phuong T.T. Nguyen, Faith L.W. Liebl, Daniel R. Marenda
We are beginning to appreciate the complex mechanisms by which epigenetic proteins control chromatin dynamics to tightly regulate normal development. However, the interaction between these proteins, particularly in the context of neuronal function, remains poorly understood. Here, we demonstrate that the activity of histone deacetylases (HDACs) opposes that of a chromatin remodeling enzyme at the Drosophila neuromuscular junction (NMJ). Pharmacological inhibition of HDAC function reverses loss of function phenotypes associated with Kismet, a chromodomain helicase DNA-binding (CHD) protein. Inhibition of HDACs suppresses motor deficits, overgrowth of the NMJ, and defective neurotransmission associated with loss of Kismet. We hypothesize that Kismet and HDACs may converge on a similar set of target genes in the nervous system. Our results provide further understanding into the complex interactions between epigenetic protein function in vivo.
Emerging themes in neuronal activity-dependent gene expression Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-12-15 Ram Madabhushi, Tae-Kyung Kim
In this review, we attempt to discuss emerging themes in the regulation of neuronal activity-regulated genes, focusing primarily on an important subset of immediate-early genes. We first discuss earlier studies that have illuminated the role of cis-acting elements within the promoters of immediate-early genes, the corresponding transcription factors that bind these elements, and the roles of major activity-regulated signaling pathways. However, our emphasis is on new studies that have revealed an important role for epigenetic and topological mechanisms, including enhancer-promoter interactions, enhancer RNAs (eRNAs), and activity-induced DNA breaks, that have emerged as important factors that govern the temporal dynamics of activity-induced gene transcription.
The histone demethylase Kdm6b regulates a mature gene expression program in differentiating cerebellar granule neurons Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-12-15 Ranjula Wijayatunge, Fang Liu, Karl B. Shpargel, Nicole J. Wayne, Urann Chan, Jane-Valeriane Boua, Terry Magnuson, Anne E. West
The histone H3 lysine 27 (H3K27) demethylase Kdm6b (Jmjd3) can promote cellular differentiation, however its physiological functions in neurons remain to be fully determined. We studied the expression and function of Kdm6b in differentiating granule neurons of the developing postnatal mouse cerebellum. At postnatal day 7, Kdm6b is expressed throughout the layers of the developing cerebellar cortex, but its expression is upregulated in newborn cerebellar granule neurons (CGNs). Atoh1-Cre mediated conditional knockout of Kdm6b in CGN precursors either alone or in combination with Kdm6a did not disturb the gross morphological development of the cerebellum. Furthermore, RNAi-mediated knockdown of Kdm6b in cultured CGN precursors did not alter the induced expression of early neuronal marker genes upon cell cycle exit. By contrast, knockdown of Kdm6b significantly impaired the induction of a mature neuronal gene expression program, which includes gene products required for functional synapse maturation. Loss of Kdm6b also impaired the ability of Brain-Derived Neurotrophic Factor (BDNF) to induce expression of Grin2c and Tiam1 in maturing CGNs. Taken together, these data reveal a previously unknown role for Kdm6b in the postmitotic stages of CGN maturation and suggest that Kdm6b may work, at least in part, by a transcriptional mechanism that promotes gene sensitivity to regulation by BDNF.
Chromatin remodeling and epigenetic regulation of oligodendrocyte myelination and myelin repair Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-12-15 Elijah Koreman, Xiaowei Sun, Q. Richard Lu
Oligodendrocytes are essential for the development, function, and health of the vertebrate central nervous system. These cells maintain axon myelination to ensure saltatory propagation of action potentials. Oligodendrocyte develops from neural progenitor cells, in a step-wise process that involves oligodendrocyte precursor specification, proliferation, and differentiation. The lineage progression requires coordination of transcriptional and epigenetic circuits to mediate the stage-specific intricacies of oligodendrocyte development. Epigenetic mechanisms involve DNA methylation, histone modifications, ATP-dependent chromatin remodeling, and non-coding RNA modulation that regulate the chromatin state over regulatory genes, which must be expressed or repressed to establish oligodendrocyte identity and lineage progression. In this review, we will focus on epigenetic programming associated with histone modification enzymes, chromatin remodeling, and non-coding RNAs that regulate oligodendrocyte lineage progression, and discuss how these mechanisms might be harnessed to induce myelin repair for treatment of demyelinating diseases such as multiple sclerosis.
Neuron-specific alternative splicing of transcriptional machineries: Implications for neurodevelopmental disorders Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-12-15 Robert S. Porter, Farris Jaamour, Shigeki Iwase
The brain has long been known to display the most complex pattern of alternative splicing, thereby producing diverse protein isoforms compared to other tissues. Recent evidence indicates that many alternative exons are neuron-specific, evolutionarily conserved, and found in regulators of transcription including DNA-binding protein and histone modifying enzymes. This raises a possibility that neurons adopt unique mechanisms of transcription. Given that transcriptional machineries are frequently mutated in neurodevelopmental disorders with cognitive dysfunction, it is important to understand how neuron-specific alternative splicing contributes to proper transcriptional regulation in the brain. In this review, we summarize current knowledge regarding how neuron-specific splicing events alter the function of transcriptional regulators and shape unique gene expression patterns in the brain and the implications of neuronal splicing to the pathophysiology of neurodevelopmental disorders.
Chromatin in nervous system development and disease Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-12-15 Shigeki Iwase, Donna M. Martin
Epigenetic regulation of gene expression is critical during development of the central nervous system. Pathogenic variants in genes encoding epigenetic factors have been found to cause a wide variety of neurodevelopmental disorders including Autism spectrum disorder, intellectual disability, and epilepsy. Cancers affecting neuronal and glial cells in the brain have also been shown to exhibit somatic mutations in epigenetic regulators, suggesting chromatin-based links between regulated and dysregulated cellular proliferation and differentiation. In this special issue, six articles review recent discoveries implicating epigenetic modifiers in normal and disease states affecting the nervous system, and the underlying mechanisms by which these modifiers function. Two articles present new information about roles for chromatin regulators in nervous system development and cancer. Together, these manuscripts provide a concise overview of this rapidly growing field. In this introduction, we briefly summarize themes presented in the issue, and pose questions for ongoing research and discovery.
Trans ε-viniferin is an amyloid-β disaggregating and anti-inflammatory drug in a mouse primary cellular model of Alzheimer's disease Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-12-07 Elodie Vion, Guylène Page, Eric Bourdeaud, Marc Paccalin, Jérôme Guillard, Agnès Rioux Bilan
Alzheimer's disease (AD) is marked by several cellular and molecular damage. Therefore, the therapeutic interest of multi-target molecules is increasingly justified. Polyphenols presenting multiple pharmacological effects would be more efficient. In this study, beneficial effects of trans ε-viniferin, a natural polyphenol were thus evaluated. This study reported that this stilbenoid (1) induced the disaggregation of amyloid β (Aβ) peptide and (2) rescued inflammation in murine primary neuronal cultures. These both effects are higher than those of resveratrol, and so, trans ε-viniferin could be a good therapeutic multi-target candidate.
Ca2+ mediates axotomy-induced necrosis and apoptosis of satellite glial cells remote from the transection site in the isolated crayfish mechanoreceptor Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-12-08 Andrey Khaitin, Mikhail Rudkovskii, Anatoly Uzdensky
Impaired neurogenesis and associated gliosis in mouse brain with PEX13 deficiency Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-12-02 Rani Sadia Rahim, James A. St John, Denis I. Crane, Adrian C.B. Meedeniya
Zellweger syndrome (ZS), a neonatal lethal disorder arising from defective peroxisome biogenesis, features profound neuroanatomical abnormalities and brain dysfunction. Here we used mice with brain-restricted inactivation of the peroxisome biogenesis gene PEX13 to model the pathophysiological features of ZS, and determine the impact of peroxisome dysfunction on neurogenesis and cell maturation in ZS. In the embryonic and postnatal PEX13 mutant brain, we demonstrate key regions with altered brain anatomy, including enlarged lateral ventricles and aberrant cortical, hippocampal and hypothalamic organization. To characterize the underlying mechanisms, we show a significant reduction in proliferation, migration, differentiation, and maturation of neural progenitors in embryonic E12.5 through to P3 animals. An increasing reactive gliosis in the PEX13 mutant brain started at E14.5 in association with the pathology. Together with impaired neurogenesis and associated gliosis, our data demonstrate increased cell death contributing to the hallmark brain anatomy of ZS. We provide unique data where impaired neurogenesis and migration are shown as critical events underlying the neuropathology and altered brain function of mice with peroxisome deficiency.
Age-related epigenetic changes in hippocampal subregions of four animal models of Alzheimer's disease Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-11-04 Roy Lardenoije, Daniël L.A. van den Hove, Monique Havermans, Anne van Casteren, Kevin X. Le, Roberta Palmour, Cynthia A. Lemere, Bart P.F. Rutten
Both aging and Alzheimer's disease (AD) are associated with widespread epigenetic changes, with most evidence suggesting global hypomethylation in AD. It is, however, unclear how these age-related epigenetic changes are linked to molecular aberrations as expressed in animal models of AD. Here, we investigated age-related changes of epigenetic markers of DNA methylation and hydroxymethylation in a range of animal models of AD, and their correlations with amyloid plaque load. Three transgenic mouse models, including the J20, APP/PS1dE9 and 3xTg-AD models, as well as Caribbean vervets (a non-transgenic non-human primate model of AD) were investigated. In the J20 mouse model, an age-related decrease in DNA methylation was found in the dentate gyrus (DG) and a decrease in the ratio between DNA methylation and hydroxymethylation was found in the DG and cornu ammonis (CA) 3. In the 3xTg-AD mice, an age-related increase in DNA methylation was found in the DG and CA1-2. No significant age-related alterations were found in the APP/PS1dE9 mice and non-human primate model. In the J20 model, hippocampal plaque load showed a significant negative correlation with DNA methylation in the DG, and with the ratio a negative correlation in the DG and CA3. For the APP/PS1dE9 model a negative correlation between the ratio and plaque load was observed in the CA3, as well as a negative correlation between DNA methyltransferase 3A (DNMT3A) levels and plaque load in the DG and CA3. Thus, only the J20 model showed an age-related reduction in global DNA methylation, while DNA hypermethylation was observed in the 3xTg-AD model. Given these differences between animal models, future studies are needed to further elucidate the contribution of different AD-related genetic variation to age-related epigenetic changes.
Comparing the different response of PNS and CNS injured neurons to mesenchymal stem cell treatment Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-11-06 Marianna Monfrini, Maddalena Ravasi, Daniele Maggioni, Elisabetta Donzelli, Giovanni Tredici, Guido Cavaletti, Arianna Scuteri
Mesenchymal stem cells (MSCs) are adult bone marrow-derived stem cells actually proposed indifferently for the therapy of neurological diseases of both the Central (CNS) and the Peripheral Nervous System (PNS), as a panacea able to treat so many different diseases by their immunomodulatory ability and supportive action on neuronal survival. However, the identification of the exact mechanism of MSC action in the different diseases, although mandatory to define their real and concrete utility, is still lacking. Moreover, CNS and PNS neurons present many different biological properties, and it is still unclear if they respond in the same manner not only to MSC treatment, but also to injuries. For these reasons, in this study we compared the susceptibility of cortical and sensory neurons both to toxic drug exposure and to MSC action, in order to verify if these two neuronal populations can respond differently. Our results demonstrated that Cisplatin (CDDP), Glutamate, and Paclitaxel-treated sensory neurons were protected by the co-culture with MSCs, in different manners: through direct contact able to block apoptosis for CDDP- and Glutamate-treated neurons, and by the release of trophic factors for Paclitaxel-treated ones. A possible key soluble factor for MSC protection was Glutathione, spontaneously released by these cells. On the contrary, cortical neurons resulted more sensitive than sensory ones to the toxic action of the drugs, and overall MSCs failed to protect them. All these data identified for the first time a different susceptibility of cortical and sensory neurons, and demonstrated a protective action of MSCs only against drugs in peripheral neurotoxicity.
Exercise decreases BACE and APP levels in the hippocampus of a rat model of Alzheimer's disease Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-11-09 Karim A. Alkadhi, An T. Dao
We investigated the effect of treadmill exercise training on the levels of Alzheimer's disease (AD)-related protein molecules in the DG and CA1 areas of a rat model of AD, i.c.v. infusion of Aβ1–42 peptide, 2 weeks (250 pmol/day). Aβ infusion markedly increased protein levels of amyloid precursor protein (APP), the secretase beta-site APP cleaving enzyme-1 (BACE-1) and Aβ in the CA1 and DG areas. The results also revealed that 4 weeks of treadmill exercise prevented the increase in the levels of APP, BACE-1 and Aβ proteins in both hippocampal areas. Exercise, however, did not affect the levels of these proteins in normal rats. We suggest that exercise might be changing the equilibrium of APP processing pathway towards the nonpathogenic pathway most probably via increasing BDNF levels in the brain of AD model.
A proteomic investigation into mechanisms underpinning corticosteroid effects on neural stem cells Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-11-09 Rawaa S. Al-Mayyahi, Luke D. Sterio, Joanne B. Connolly, Christopher F. Adams, Wa'il A. Al-Tumah, Jon Sen, Richard D. Emes, Sarah R. Hart, Divya M. Chari
Corticosteroids (CSs) are widely used clinically, for example in pediatric respiratory distress syndrome, and immunosuppression to prevent rejection of stem cell transplant populations in neural cell therapy. However, such treatment can be associated with adverse effects such as impaired neurogenesis and myelination, and increased risk of cerebral palsy. There is increasing evidence that CSs can adversely influence key biological properties of neural stem cells (NSCs) but the molecular mechanisms underpinning such effects are largely unknown. This is an important issue to address given the key roles NSCs play during brain development and as transplant cells for regenerative neurology. Here, we describe the use of label-free quantitative proteomics in conjunction with histological analyses to study CS effects on NSCs at the cellular and molecular levels, following treatment with methylprednisolone (MPRED). Immunocytochemical staining showed that both parent NSCs and newly generated daughter cells expressed the glucocorticoid receptor, with nuclear localisation of the receptor induced by MPRED treatment. MPRED markedly decreased NSC proliferation and neuronal differentiation while accelerating the maturation of oligodendrocytes, without concomitant effects on cell viability and apoptosis. Parallel proteomic analysis revealed that MPRED induced downregulation of growth associated protein 43 and matrix metallopeptidase 16 with upregulation of the cytochrome P450 family 51 subfamily A member 1. Our findings support the hypothesis that some neurological deficits associated with CS use may be mediated via effects on NSCs, and highlight putative target mechanisms underpinning such effects.
Age-related changes in STriatal-Enriched protein tyrosine Phosphatase levels: Regulation by BDNF Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-11-06 Silvia Cases, Ana Saavedra, Shiraz Tyebji, Albert Giralt, Jordi Alberch, Esther Pérez-Navarro
Recent results indicate that STriatal-Enriched protein tyrosine Phosphatase (STEP) levels are regulated by brain-derived neurotrophic factor (BDNF), whose expression changes during postnatal development and aging. Here, we studied STEP ontogeny in mouse brain and changes in STEP with age with emphasis on the possible regulation by BDNF. We found that STEP expression increased during the first weeks of life, reaching adult levels by 2–3 weeks of age in the striatum and cortex, and by postnatal day (P) 7 in the hippocampus. STEP protein levels were unaffected in BDNF+/− mice, but were significantly reduced in the striatum and cortex, but not in the hippocampus, of BDNF−/− mice at P7 and P14. In adult wild-type mice there were no changes in cortical and hippocampal STEP61 levels with age. Conversely, striatal STEP levels were reduced from 12 months of age, correlating with higher ubiquitination and increased BDNF content and signaling. Lower STEP levels in older mice were paralleled by increased phosphorylation of its substrates. Since altered STEP levels are involved in cellular malfunctioning events, its reduction in the striatum with increasing age should encourage future studies of how this imbalance might participate in the aging process.
miR-302/367-induced neurons reduce behavioral impairment in an experimental model of Alzheimer's disease Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-11-24 Maryam Ghasemi-Kasman, Amir Shojaei, Mohammad Gol, Ali Akbar Moghadamnia, Hossein Baharvand, Mohammad Javan
Heat shock protein 70 suppresses neuroinflammation induced by α-synuclein in astrocytes Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-11-26 Wen-Wen Yu, Sheng-Nan Cao, Cai-Xia Zang, Lu Wang, Han-Yu Yang, Xiu-Qi Bao, Dan Zhang
Neuroinflammation triggered by activation of glial cells plays an important role in the pathophysiology of several neurodegenerative diseases including Parkinson's disease (PD). Besides microglia, astrocytes are also critical in initiating and perpetuating inflammatory process associated with PD. Heat shock protein 70 (Hsp70) is originally described as intracellular chaperone, however, recent study revealed that it had anti-inflammatory effects as well. The present study is designed to investigate whether Hsp70 mediates neuroinflammation in astrocytes. By employing α-synuclein (α-Syn) (A53T) aggregates on primary cultured astrocytes of rats, we found that astrocytes were activated and neuroinflammatory response was triggered, as indicated by over-expression of glial fibrillary acidic protein (GFAP), cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS), increased production of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β). The data also showed that the neuroinflammatory response accompanied up-regulated Hsp70 expression. Moreover, over-expression of Hsp70 through transfection of Hsp70 cDNA plasmids could significantly reduce the production of TNF-α, IL-1β, and the expression of GFAP, COX-2 as well as iNOS. While inhibition of Hsp70 by VER155008 exacerbated neuroinflammatory response in astrocytes challenged by α-Syn aggregates. Further mechanistic study indicated that c-Jun N-terminal kinase (JNK) and nuclear factor-κB (NF-κB) signalings were responsible for the neuroinflammation, which was also regulated by Hsp70. These findings demonstrated that Hsp70 was an important modulator in astrocytes induced inflammation, and up-regulation of Hsp70 might be a potential regulating approach for neuroinflammation-related neurodegenerative diseases, such as PD.
Peroxisomes contribute to oxidative stress in neurons during doxorubicin-based chemotherapy Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-11-24 Jose F. Moruno-Manchon, Ndidi-Ese Uzor, Shelli R. Kesler, Jeffrey S. Wefel, Debra M. Townley, Archana Sidalaghatta Nagaraja, Sunila Pradeep, Lingegowda S. Mangala, Anil K. Sood, Andrey S. Tsvetkov
Doxorubicin, a commonly used anti-neoplastic agent, causes severe neurotoxicity. Doxorubicin promotes thinning of the brain cortex and accelerates brain aging, leading to cognitive impairment. Oxidative stress induced by doxorubicin contributes to cellular damage. In addition to mitochondria, peroxisomes also generate reactive oxygen species (ROS) and promote cell senescence. Here, we investigated if doxorubicin affects peroxisomal homeostasis in neurons. We demonstrate that the number of peroxisomes is increased in doxorubicin-treated neurons and in the brains of mice which underwent doxorubicin-based chemotherapy. Pexophagy, the specific autophagy of peroxisomes, is downregulated in neurons, and peroxisomes produce more ROS. 2-hydroxypropyl-β-cyclodextrin (HPβCD), an activator of the transcription factor TFEB, which regulates expression of genes involved in autophagy and lysosome function, mitigates damage of pexophagy and decreases ROS production induced by doxorubicin. We conclude that peroxisome-associated oxidative stress induced by doxorubicin may contribute to neurotoxicity, cognitive dysfunction, and accelerated brain aging in cancer patients and survivors. Peroxisomes might be a valuable new target for mitigating neuronal damage caused by chemotherapy drugs and for slowing down brain aging in general.
Depletion of transglutaminase 2 in neurons alters expression of extracellular matrix and signal transduction genes and compromises cell viability Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-11-29 Laura Yunes-Medina, Alex Paciorkowski, Yan Nuzbrokh, Gail V.W. Johnson
The protein transglutaminase 2 (TG2) has been implicated as a modulator of neuronal viability. TG2's role in mediating cell survival processes has been suggested to involve its ability to alter transcriptional events. The goal of this study was to examine the role of TG2 in neuronal survival and to begin to delineate the pathways it regulates. We show that depletion of TG2 significantly compromises the viability of neurons in the absence of any stressors. RNA sequencing revealed that depletion of TG2 dysregulated the expression of 86 genes with 59 of these being upregulated. The genes that were upregulated by TG2 knockdown were primarily involved in extracellular matrix function, cell signaling and cytoskeleton integrity pathways. Finally, depletion of TG2 significantly reduced neurite length. These findings suggest for the first time that TG2 plays a crucial role in mediating neuronal survival through its regulation of genes involved in neurite length and maintenance.
Aberrant subcellular localization of SQSTM1/p62 contributes to increased vulnerability to proteotoxic stress recovery in Huntington's disease Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-12-12 Ningjing Huang, Christine Erie, Michael L. Lu, Jianning Wei
Munc18-1 haploinsufficiency impairs learning and memory by reduced synaptic vesicular release in a model of Ohtahara syndrome Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-12-05 Albert Orock, Sreemathi Logan, Ferenc Deak
Ohtahara syndrome, also known as type 4 of Early Infantile Epileptic Encephalopathy with suppression bursts (EIEE-4) is currently an untreatable disorder that presents with seizures and impaired cognition. EIEE-4 patients have mutations most frequently in the STXBP1 gene encoding a Sec protein, munc18-1. The exact molecular mechanism of how these munc18-1 mutations cause impaired cognition, remains elusive. The leading haploinsufficiency hypothesis posits that mutations in munc18-1 render the protein unstable leading to its degradation. Expression driven by the healthy allele is not sufficient to maintain the physiological function resulting in haploinsufficiency. The aim of this study has been to understand how munc18-1 haploinsufficiency causes cognitive impairment seen in EIEE-4. Here we present results from behavioral to cellular effects from a mouse model of munc18-1 haploinsufficiency. Munc18-1 heterozygous knock-out mice showed impaired spatial learning and memory in behavior tests as well as reduced synaptic plasticity in hippocampal CA1 long-term potentiation. Cultured munc18-1 heterozygous hippocampal neurons had significantly slower rate of synaptic vesicle release and decreased readily releasable vesicle pool compared to wild-type control neurons in fluorescent FM dye assays. These results demonstrate that reduced munc18-1 levels are sufficient to impair learning and memory by reducing neurotransmitter release. Therefore, our study implicates munc18-1 haploinsufficiency as a primary cause of cognitive impairment seen in EIEE-4 patients.
Proteasome phosphorylation regulates cocaine-induced sensitization Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-12-05 Frankie R. Gonzales, Kristin K. Howell, Lara E. Dozier, Stephan G. Anagnostaras, Gentry N. Patrick
Alpha-synuclein ferrireductase activity is detectible in vivo, is altered in Parkinson's disease and increases the neurotoxicity of DOPAL Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-08-12 Jennifer S. McDowall, Ioanna Ntai, Kevin C. Honeychurch, John P. Hart, Philippe Colin, Bernard L. Schneider, David R. Brown
The normal cellular role of α-synuclein is of potential importance in understanding diseases in which an aggregated form of the protein has been implicated. A potential loss or change in the normal function of α-synuclein could play a role in the aetiology of diseases such as Parkinson's disease. Recently, it has been suggested that α-synuclein could cause the enzymatic reduction of iron and a cellular increase in Fe(II) levels. Experiments were carried out to determine if such activity could be measured in vivo. Experiments with rats overexpressing human α-synuclein in nigral dopaminergic neurons demonstrated a correlation between α-synuclein expression and ferrireductase activity. Furthermore, studies on tissue from Parkinson's disease patient brains showed a significant decrease in ferrireductase activity, possibly due to deposition of large amounts of inactive protein. Cellular studies suggest that increase ferrireductase activity results in increased levels of dopamine metabolites and increased sensitivity to the toxicity of DOPAL. These findings demonstrate that α-synuclein ferrireductase activity is present in vivo and its alteration may play a role in neuron loss in disease.
The actin binding protein scinderin acts in PC12 cells to tether dense-core vesicles prior to secretion Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-08-18 J. Wang, D.A. Richards
Mechanistic understanding of the control of vesicle motion from within a secretory cell to the site of exocytosis remains incomplete. In this work, we have used total internal reflection (TIRF) microscopy to examine the mobility of secretory vesicles at the plasma membrane. Under resting conditions, we found vesicles showed little lateral mobility. Anchoring of vesicles in this membrane proximal compartment could be disrupted with latrunculin A, indicating an apparent actin dependent process. A candidate intermediary between vesicles and the actin skeleton is the actin binding protein scinderin. Co-transfection of an shRNA construct against scinderin blocked secretion, and also increased the mobility of vesicles in the membrane-proximal section of the cell, indicating a dual role for scinderin in secretion; tethering vesicles to the cytoskeleton, as well as liberating them following stimulation through the previously described calcium dependent actin severing activity. Analysis of lipid dependence indicates that scinderin exhibits calcium dependent binding to phosphatidyl-inositol monophosphate, providing a possible mechanism for vesicle binding.
The expression of pluripotency and neuronal differentiation markers under the influence of electromagnetic field and nitric oxide Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-08-24 Nazanin Haghighat, Parviz Abdolmaleki, Javad Parnian, Mehrdad Behmanesh
Nitric oxide (NO) is a diatomic free radical compound that as a secondary messenger contributes to cell physiological functions and its variations influence proteins activity and triggering intracellular signaling cascades. Low frequency electromagnetic field (EMF) alters the cell biology such as cell differentiation by targeting the plasma membrane and entering force to the ions and small electrical ligands. The effect of these chemical (NO) and physical (EMF) factors on the expression of the stemness and neuronal differentiation markers in rat bone marrow mesenchymal stem cells (BMSC) was investigated. The cells were treated with low (50 micromolar) and high (1 mM) concentrations of Deta-NO as a NO donor molecule and 50 Hz low frequency EMF. The expression of pluripotency and neuronal differentiation genes and proteins was investigated using real time qPCR and Immunocytochemistry techniques. The simultaneous treatment of EMF with NO (1 mM) led to the down-regulation of stemness markers expression and up-regulation of neuronal differentiation markers expression. Cell proliferation decreased and cell morphology changed which caused the majority of cells obtains neuronal protein markers in their cytoplasm. The decrease in the expression of neuronal differentiation Nestin and DCX markers without any change in the expression of pluripotency Oct4 marker (treated with low concentration of NO) indicates protection of stemness state in these cells. Treatment with NO demonstrated a double behavior. NO low concentration helped the cells protect the stemness state but NO high concentration plus EMF pushed cells into differentiation pathway.
Cocaine modifies brain lipidome in mice Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-08-19 Yiyun Lin, Hui Gu, Linhong Jiang, Wei Xu, Chunqi Liu, Yan Li, Xinying Qian, Dandan Li, Zhuoling Li, Jing Hu, Huaqin Zhang, Wei Guo, Yinglan Zhao, Xiaobo Cen
Lipids are predominant components of the brain and key regulators for neural structure and function. The neuropsychopharmacological effect of cocaine has been intensively investigated; however, the impact of cocaine on brain lipid profiles is largely unknown. In this study, we used a LC-MS-based lipidomic approach to investigate the impact of cocaine on brain lipidome in two mouse models, cocaine-conditioned place preference (CPP) and hyperlocomotor models and the lipidome was profoundly modified in the nucleus accumbens (NAc) and striatum respectively. We comprehensively analyzed the lipids among 21 subclasses across 7 lipid classes and found that cocaine profoundly modified brain lipidome. Notably, the lipid metabolites significantly modified were sphingolipids and glycerophospholipids in the NAc, showing a decrease in ceramide and an increase in its up/downstream metabolites levels, and decrease lysophosphatidylcholine (LPC) and lysophosphoethanolamine (LPE) and increase phosphatidylcholine (PC) and phosphatidylethanolamines (PE) levels, respectively. Moreover, long and polyunsaturated fatty acid phospholipids were also markedly increased in the NAc. Our results show that cocaine can markedly modify brain lipidomic profiling. These findings reveal a link between the modified lipidome and psychopharmacological effect of cocaine, providing a new insight into the mechanism of cocaine addiction.
TGF-β1 enhances phagocytic removal of neuron debris and neuronal survival by olfactory ensheathing cells via integrin/MFG-E8 signaling pathway Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-08-30 Yijian Li, Ting Zou, Langyue Xue, Zheng Qin Yin, Shujia Huo, Haiwei Xu
Olfactory ensheathing cells (OECs) have been shown to be a leading candidate in cell therapies for central nervous system (CNS) injuries and neurodegenerative diseases. Rapid clearance of neuron debris can promote neuronal survival and axonal regeneration in CNS injuries and neurodegenerative diseases. The phagocytic removal of neuron debris by OECs has been shown to contribute to neuronal outgrowth. However, the precise molecular and cellular mechanisms of phagocytic removal of neuron debris by OECs have not been explored. In this study, we found that OECs secreted anti-inflammatory cytokine transforming growth factor β1 (TGF-β1) during the phagocytic removal of neuron debris. TGF-β1 enhanced phagocytic activity of OECs through regulating integrin/MFG-E8 signaling pathway. In addition, TGF-β1 shifted OECs towards a flattened shape with increased cellular area, which might also be involved in the enhancement of phagocytic activity of OECs. Furthermore, the removal of neuron debris by OECs affected neuronal survival and outgrowth. TGF-β1 enhanced the clearance of neuron debris by OECs and increased neuronal survival. These results reveal the role and mechanism of TGF-β1 in enhancing the phagocytic activity of OECs, which will update the understanding of phagocytosis of OECs and improve the therapeutic use of OECs in CNS injuries and neurodegenerative diseases.
NeuronRead, an open source semi-automated tool for morphometric analysis of phase contrast and fluorescence neuronal images Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-08-25 Roberto A. Dias, Bruno P. Gonçalves, Joana F. da Rocha, Odete A.B. da Cruz e Silva, Augusto M.F. da Silva, Sandra I. Vieira
Neurons are specialized cells of the Central Nervous System whose function is intricately related to the neuritic network they develop to transmit information. Morphological evaluation of this network and other neuronal structures is required to establish relationships between neuronal morphology and function, and may allow monitoring physiological and pathophysiologic alterations. Fluorescence-based microphotographs are the most widely used in cellular bioimaging, but phase contrast (PhC) microphotographs are easier to obtain, more affordable, and do not require invasive, complicated and disruptive techniques. Despite the various freeware tools available for fluorescence-based images analysis, few exist that can tackle the more elusive and harder-to-analyze PhC images. To surpass this, an interactive semi-automated image processing workflow was developed to easily extract relevant information (e.g. total neuritic length, average cell body area) from both PhC and fluorescence neuronal images. This workflow, named ‘NeuronRead’, was developed in the form of an ImageJ macro. Its robustness and adaptability were tested and validated on rat cortical primary neurons under control and differentiation inhibitory conditions. Validation included a comparison to manual determinations and to a golden standard freeware tool for fluorescence image analysis. NeuronRead was subsequently applied to PhC images of neurons at distinct differentiation days and exposed or not to DAPT, a pharmacological inhibitor of the γ-secretase enzyme, which cleaves the well-known Alzheimer's amyloid precursor protein (APP) and the Notch receptor. Data obtained confirms a neuritogenic regulatory role for γ-secretase products and validates NeuronRead as a time- and cost-effective useful monitoring tool.
A subpopulation of activated retinal macrophages selectively migrated to regions of cone photoreceptor stress, but had limited effect on cone death in a mouse model for type 2 Leber congenital amaurosis Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-09-08 Peter H. Tang, Mark J. Pierson, Neal D. Heuss, Dale S. Gregerson
Background Studies of antigen presentation in retina using mice that expressed green fluorescent protein (GFP) from a transgenic CD11c promoter found that retinal GFPhi cells possessed antigen presentation function. Subsequent studies found that these high GFPhi cells preferentially localized to sites of retinal injury, consistent with their APC function. Interest in the roles of macrophages in degenerative CNS diseases led us to study the GFPhi cells in a retinal model of neurodegeneration. We asked if apoptotic cone photoreceptor cell death in Rpe65−/− knockout mice induced the GFPhi cells, explored their relationship to resident microglia (MG), and tested their role in cone survival. Methods Rpe65−/− mice were bred to CD11cGFP mice on the B6/J background. CD11cGFPRpe65−/− mice were also backcrossed to CX3CR1YFP-creERROSADTA mice so that CX3CR1+ mononuclear cells could be depleted by Tamoxifen. Retinas were analyzed by immunohistochemistry, confocal microscopy, fluorescence fundoscopy and flow cytometry. Results Elevated numbers of GFPhi cells were concentrated in photoreceptor cell layers of CD11cGFPRpe65−/− mice coinciding with the peak of cone death at 2 to 4 weeks of age, and persisted for at least 14 months. After the initial wave of cone loss, a slow progressive loss of cones was found that continued to retain GFPhi cells in the outer retina. Sustained, four-week Tamoxifen depletions of the GFPhi cells and MG in Rpe65−/− mice from day 13 to day 41, and from day 390 to day 420 promoted a small increase in cone survival. We found no evidence that the GFPhi cells were recruited from the circulation; all data pointed to a MG origin. MG and GFPhi cells were well segregated in the dystrophic retina; GFPhi cells were foremost in the photoreceptor cell layer, while MG were concentrated in the inner retina. Conclusions The expression of GFP on a subset of retinal mononuclear cells in CD11cGFP mice identified a distinct population of cells performing functions previously attributed to MG. Although GFPhi cells dominated the macrophage response to cone death in the photoreceptor cell layer, their ablation led to only an incremental increase in cone survival. The ability to identify, ablate, and isolate these cells will facilitate analysis of this activated, antigen-presenting subset of MG.
Attentional deficits and altered neuronal activation in medial prefrontal and posterior parietal cortices in mice with reduced dopamine transporter levels Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-09-18 Anita Cybulska-Klosowicz, Marta Laczkowska, Renata Zakrzewska, Aleksandra Kaliszewska
The executive control function of attention is regulated by the dopaminergic (DA) system. Dopamine transporter (DAT) likely plays a role in controlling the influence of DA on cognitive processes. We examined the effects of DAT depletion on cognitive processes related to attention. Mice with the DAT gene genetically deleted (DAT +/− heterozygotes) were compared to wild type (WT) mice on the Attentional Set-Shifting Task (ASST). Changes in neuronal activity during the ASST were shown with early growth response genes 1 and 2 (egr-1 and egr-2) immunohistochemistry in the medial prefrontal cortex (mPFC) and in the posterior parietal cortex (PPC). Heterozygotes were impaired in tasks that tax reversal learning, attentional-set formation and set-shifting. Densities of egr-2 labeled cells in the mPFC were lower in mutant mice when compared with wild-types in intradimensional shift of attention (IDS), extradimensional shift of attention and extradimensional shift of attention-reversal phases of the ASST task, and in PPC in the IDS phase of the task. The results demonstrate impairments of the areas associated with attentional functions in DAT +/− mice and show that an imbalance of the dopaminergic system has an impact on the complex attention-related executive functions.
Chronic ethanol exposure increases inhibition of optically targeted phasic dopamine release in the nucleus accumbens core and medial shell ex vivo Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-09-20 James R. Melchior, Sara R. Jones
Dopamine signaling encodes reward learning and motivated behavior through modulation of synaptic signaling in the nucleus accumbens, and aberrations in these processes are thought to underlie obsessive behaviors associated with alcohol abuse. The nucleus accumbens is divided into core and shell sub-regions with overlapping but also divergent contributions to behavior. Here we optogenetically targeted dopamine projections to the accumbens allowing us to isolate stimulation of dopamine terminals ex vivo. We applied 5 pulse (phasic) light stimulations to probe intrinsic differences in dopamine release parameters across regions. Also, we exposed animals to 4 weeks of chronic intermittent ethanol vapor and measured phasic release. We found that initial release probability, uptake rate and autoreceptor inhibition were greater in the accumbens core compared to the shell, yet the shell showed greater phasic release ratios. Following chronic ethanol, uptake rates were increased in the core but not the shell, suggesting region-specific neuronal adaptations. Conversely, kappa opioid receptor function was upregulated in both regions to a similar extent, suggesting a local mechanism of kappa opioid receptor regulation that is generalized across the nucleus accumbens. These data suggest that dopamine axons in the nucleus accumbens core and shell display differences in intrinsic release parameters, and that ethanol-induced adaptations to dopamine neuron terminal fields may not be homogeneous. Also, chronic ethanol exposure induces an upregulation in kappa opioid receptor function, providing a mechanism for potential over-inhibition of accumbens dopamine signaling which may negatively impact downstream synaptic function and ultimately bias choice towards previously reinforced alcohol use behaviors.
Astrocytic expression of the CXCL12 receptor, CXCR7/ACKR3 is a hallmark of the diseased, but not developing CNS Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-09-08 Malte Puchert, Fabian Pelkner, Gregor Stein, Doychin N. Angelov, Johannes Boltze, Daniel-Christoph Wagner, Francesca Odoardi, Alexander Flügel, Wolfgang J. Streit, Jürgen Engele
Based on our previous demonstration of CXCR7 as the major mediator of CXCL12 signaling in cultured astrocytes, we have now compared astrocytic expression of the CXCL12 receptors, CXCR7 and CXCR4, during CNS development and disease. In addition, we asked whether disease-associated conditions/factors affect expression of CXCL12 receptors in astrocytes. In the late embryonic rat brain, CXCR7+/GFAP+ cells were restricted to the ventricular/subventricular zone while CXCR4 was widely absent from GFAP-positive cells. In the early postnatal and adult brain, CXCR7 and CXCR4 were almost exclusively expressed by GFAP-immunoreactive astrocytes forming the superficial glia limitans. Contrasting the situation in the intact CNS, a striking increase in astrocytic CXCR7 expression was detectable in the cortex of rats with experimental brain infarcts, in the spinal cord of rats with experimental autoimmune encephalomyelitis (EAE) and after mechanical compression, as well as in the in infarcted human cerebral cortex and in the hippocampus of Alzheimer's disease patients. None of these pathologies was associated with substantial increases in astrocytic CXCR4 expression. Screening of various disease-associated factors/conditions further revealed that CXCR7 expression of cultured cortical astrocytes increases with IFNγ as well as under hypoxic conditions whereas CXCR7 expression is attenuated following treatment with IFNβ. Again, none of the treatments affected CXCR4 expression in cultured astrocytes. Together, these findings support the hypothesis of a crucial role of astrocytic CXCR7 in the progression of various CNS pathologies.
Potential deficit from decreased cerebellar granule cell migration in serine racemase-deficient mice is reversed by increased expression of GluN2B and elevated levels of NMDAR agonists Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-09-20 He Zhang, Liping Song, Yuhua Chang, Mengjuan Wu, Xiuli Kuang, Haiyan Jiang, Shengzhou Wu
Inward migration of cerebellar granule cells (CGCs) after birth is critical for lamination in the cerebellar cortex. N-methyl-d-aspartate (NMDA) subtype of glutamate receptor (NMDAR) tethering CGCs into Bergmann glial fibers mediates the inward movement during the glial-dependent migratory phase. Activation of NMDAR depends on simultaneous binding of the GluN2 subunit by glutamate, and of the GluN1 subunit by d-serine or glycine; d-serine is believed to be an endogenous ligand of NMDAR. We hypothesized that lamination of the cerebellar cortex may be compromised in Srr (the gene for serine racemase (SR)) mutated mice (Srrnull) because of significantly low levels of d-serine per se. Indeed, the external germinal cell layer (EGL) in Srrnull was thicker than in sibling wild-type (WT) mice on postnatal day7 (P7), which accords with decreased CGC migration in Srrnull mice. However, the cerebellar laminar structure in Srrnull mice was normal on P12 and later. Feeding d-serine to pregnant mice abrogated the increased EGL thickness in Srrnull mice on P7. To determine the underlying mechanism of abnormal laminar structure during cerebellar development in Srrnull mice, we examined NMDAR subunits and their ligands. We found increased GluN2B on P10 and increased glycine during P7–12 in the cerebellar homogenates from Srrnull mice compared with the corresponding values from sibling WT mice. In summary, the study revealed how the potential defect in early cerebellar development caused by Srr mutation is circumvented by a compensatory mechanism. This knowledge advances understanding of the adaptation of cerebellar development under the condition of Srr mutation.
Ras-GRF2 regulates nestin-positive stem cell density and onset of differentiation during adult neurogenesis in the mouse dentate gyrus Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-09-28 Carmela Gómez, David Jimeno, Alberto Fernández-Medarde, Rósula García-Navas, Nuria Calzada, Eugenio Santos
Dual effect of serotonin on the dendritic growth of cultured hippocampal neurons: Involvement of 5-HT1A and 5-HT7 receptors Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-09-30 P.S. Rojas, F. Aguayo, D. Neira, M. Tejos, E. Aliaga, J.P. Muñoz, C.S. Parra, J.L. Fiedler
Serotonin acts through its receptors (5-HTRs) to shape brain networks during development and modulates essential functions in mature brain. The 5-HT1AR is mainly located at soma of hippocampal neurons early during brain development and its expression gradually shifts to dendrites during postnatal development. The 5-HT7R expressed early during hippocampus development, shows a progressive reduction in its expression postnatally. Considering these changes during development, we evaluated in cultured hippocampal neurons whether the 5-HT1AR and 5-HT7R change their expression, modulate dendritic growth, and activate signaling pathways such as ERK1/2, AKT/GSK3β and LIMK/cofilin, which may sustain dendrite outgrowth by controlling cytoskeleton dynamics. We show that mRNA levels of both receptors increase between 2 and 7 DIV; however only protein levels of 5-HT7R increase significantly at 7 DIV. The 5-HT1AR is preferentially distributed in the soma, while 5-HT7R displays a somato-dendritic localization at 7 DIV. Through stimulation with 5-HT at 7 DIV during 24 h and using specific antagonists, we determined that 5-HT1AR decreases the number of primary and secondary dendrites and restricts the growth of primary dendrites. The activation of 5-HT1AR and 5-HT7R promotes the growth of short secondary dendrites and triggers ERK1/2 and AKT phosphorylation through MEK and PI3K activation respectively; without changes in the phosphorylation of LIMK and cofilin. We conclude that 5-HT1AR restricts dendritogenesis and outgrowth of primary dendrites, but that both 5-HT1AR and 5-HT7R promote secondary dendrite outgrowth. These data support the role of 5-HT in neuronal outgrowth during development and provide insight into cellular basis of neurodevelopmental disorders.
CHI3L1 and CHI3L2 overexpression in motor cortex and spinal cord of sALS patients Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-10-06 C. Sanfilippo, A. Longo, F. Lazzara, D. Cambria, G. Distefano, M. Palumbo, A. Cantarella, L. Malaguarnera, M. Di Rosa
Background Amyotrophic Lateral Sclerosis (ALS) is a rapidly progressive neurodegenerative disease characterized by the degeneration and death of upper (UMN) and lower (LMN) motor neurons. In the last decade, it has been shown that Chitinases are an important prognostic indicator of neuro-inflammatory damage induced by microglia and astrocytes. Materials and methods We analyzed microarray datasets obtained from the Array Express in order to verify the expression levels of CHI3L1 and CHI3L2 in motor cortex biopsies of sALS patients with different survival times. We also divided the sALS patients into smokers and non-smokers. In order to extend our analysis, we explored two additional microarray datasets, GSE833 and GSE26927, of post-mortem spinal cord biopsies from sALS patients. Results The analysis showed that CHI3L1 and CHI3L2 expression levels were significantly upregulated in the motor cortex of sALS patients, compared to the healthy controls. Moreover, their expression levels were negatively correlated with survival time. Interesting results were obtained when we compared the expression levels of Chitinases among smokers. We showed that CHI3L1 and CHI3L2 were significantly upregulated in sALS smokers compared to non-smokers. Furthermore, we found that four genes belonging to the Chitinases network (SERPINA3, C1s, RRAD, HLA-DQA1) were significantly upregulated in the motor cortex of sALS patients and positively correlated with Chitinases expression levels. Similar results were obtained during the exploration of the two-microarray dataset. Conclusions This study suggests that CHI3L1 and CHI3L2 are associated with the progression of neurodegeneration in motor cortex and spinal cord of sALS patients.
Pituitary adenylate cyclase activating polypeptide induces long-term, transcription-dependent plasticity and remodeling at autonomic synapses Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-10-07 Eric R. Starr, Joseph F. Margiotta
Pituitary adenylate cyclase activating polypeptide (PACAP) is a multifunctional neuropeptide, widely expressed in the nervous system (Vaudry et al., 2009; Starr and Margiotta, 2016). At neuronal synapses where transmission is mediated by nicotinic acetylcholine receptors (nAChRs) transient PACAP exposure increases the frequency and amplitude (FS and AS) of spontaneous excitatory postsynaptic currents (sEPSCs) within minutes. This short-term (ST) plasticity requires high-affinity PACAP receptor (PAC1R) signaling via adenylate cyclase (AC), cyclic AMP (cAMP), Protein kinase A (PKA) and obligatory nAChR-dependent stimulation of nitric oxide (NO) synthesis to retrogradely increase presynaptic ACh release (Pugh et al., 2010; Jayakar et al., 2014). Remarkably, synaptic changes persist 48 h after transient PACAP exposure, featuring a similar increase in FS and an even larger increase in AS. Pharmacological studies reveal that this long-term (LT) plasticity requires PACAP/PAC1R signaling via AC and cAMP, but unlike ST plasticity, Phospholipase-C and new gene transcription are also necessary, whereas PKA, nAChR, impulse and NO synthase (NOS1) activities are dispensable. In accord with the increases in FS and AS characterizing LT plasticity, miniature EPSC (mEPSC) frequency, ACh release (quantal content), and mEPSC amplitude (quantal size) all increased in parallel. Consistent with these functional changes, imaging studies reveal that LT, but not ST, PACAP-induced plasticity is accompanied by increases in presynaptic terminal size, postsynaptic nAChR cluster size and density, and the size and density of co-localized pre- and post-synpatic sites. Thus PACAP/PAC1R signaling induces mechanistically distinct forms of synaptic plasticity, with a ST form arising from acute, membrane-delimited processes, and a LT form arising from transcription-dependent alterations in the function and structural arrangement of pre- and post-synaptic components.
Cocaine alters Homer1 natural antisense transcript in the nucleus accumbens Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-10-18 Gregory C. Sartor, Samuel K. Powell, Dmitry Velmeshev, David Y. Lin, Marco Magistri, Hannah J. Wiedner, Andrea M. Malvezzi, Nadja S. Andrade, Mohammad A. Faghihi, Claes Wahlestedt
Natural antisense transcripts (NATs) are an abundant class of long noncoding RNAs that have recently been shown to be key regulators of chromatin dynamics and gene expression in nervous system development and neurological disorders. However, it is currently unclear if NAT-based mechanisms also play a role in drug-induced neuroadaptations. Aberrant regulation of gene expression is one critical factor underlying the long-lasting behavioral abnormalities that characterize substance use disorder, and it is possible that some drug-induced transcriptional responses are mediated, in part, by perturbations in NAT activity. To test this hypothesis, we used an automated algorithm that mines the NCBI AceView transcriptomics database to identify NAT overlapping genes linked to addiction. We found that 22% of the genes examined contain NATs and that expression of Homer1 natural antisense transcript (Homer1-AS) was altered in the nucleus accumbens (NAc) of mice 2 h and 10 days following repeated cocaine administration. In in vitro studies, depletion of Homer1-AS lead to an increase in the corresponding sense gene expression, indicating a potential regulatory mechanisms of Homer1 expression by its corresponding antisense transcript. Future in vivo studies are needed to definitely determine a role for Homer1-AS in cocaine-induced behavioral and molecular adaptations.
Rem2 signaling affects neuronal structure and function in part by regulation of gene expression Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-10-21 Katelyn Kenny, Leandro Royer, Anna R. Moore, Xiao Chen, Michael T. Marr, Suzanne Paradis
The central nervous system has the remarkable ability to convert changes in the environment in the form of sensory experience into long-term alterations in synaptic connections and dendritic arborization, in part through changes in gene expression. Surprisingly, the molecular mechanisms that translate neuronal activity into changes in neuronal connectivity and morphology remain elusive. Rem2, a member of the Rad/Rem/Rem2/Gem/Kir (RGK) subfamily of small Ras-like GTPases, is a positive regulator of synapse formation and negative regulator of dendritic arborization. Here we identify that one output of Rem2 signaling is the regulation of gene expression. Specifically, we demonstrate that Rem2 signaling modulates the expression of genes required for a variety of cellular processes from neurite extension to synapse formation and synaptic function. Our results highlight Rem2 as a unique molecule that transduces changes in neuronal activity detected at the cell membrane to morphologically relevant changes in gene expression in the nucleus.
An immortalized microglial cell line (Mocha) derived from rat cochlea Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-11-03 G.M. Seigel, S. Manohar, Y.Y. Bai, D. Ding, R. Salvi
Microglia are glial-immune cells that are essential for the function and survival of the central nervous system. Microglia not only protect neural tissues from immunological insults, but also play a critical role in neural development and repair. However, little is known about the biology of microglia in the cochlea, the auditory portion of the inner ear. In this study, we detected TMEM119 +, CD11b +, CD45 + and Iba1 + populations of cells in the rat cochlea, particularly in Rosenthal's canal, inner sulcus and stria vascularis. Next, we isolated and enriched the population of CD11b + cells from the cochlea and immortalized these cells with the 12S E1A gene of adenovirus in a replication-incompetent retroviral vector to derive a novel microglial cell line, designated Mocha (microglia of the cochlea). The resulting Mocha cells express a number of markers consistent with microglia and respond to lipopolysaccharide (LPS) stimulation by upregulation of genes (Cox2, ICAM-1, Il6r, Ccl2, Il13Ra and Il15Ra) as well as releasing cytokines (IL-1beta, IL-12, IL-13 and RANTES). As evidence of microglial function, Mocha cells phagocytose fluorescent beads at 37 °C, but not at 4 °C. The expression pattern of microglial markers in Mocha cells suggests that immortalization leads to a more primitive phenotype, a common phenomenon in immortalized cell lines. In summary, Mocha cells display key characteristics of microglia and are now available as a useful model system for the study of cochlear microglial behavior, both in vitro and in vivo.
Low-dose γ-secretase inhibition increases secretion of Aβ peptides and intracellular oligomeric Aβ Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-11-03 Lotta Agholme, Marcus Clarin, Eleni Gkanatsiou, Petronella Kettunen, Jasmine Chebli, Gunnar Brinkmalm, Kaj Blennow, Petra Bergström, Erik Portelius, Henrik Zetterberg
γ-Secretase inhibitors have been considered promising drug candidates against Alzheimer's disease (AD) due to their ability to reduce amyloid-β (Aβ) production. However, clinical trials have been halted due to lack of clinical efficacy and/or side effects. Recent in vitro studies suggest that low doses of γ-secretase inhibitors may instead increase Aβ production. Using a stem cell-derived human model of cortical neurons and low doses of the γ-secretase inhibitor DAPT, the effects on a variety of Aβ peptides were studied using mass spectrometry. One major focus was to develop a novel method for specific detection of oligomeric Aβ (oAβ), and this was used to study the effects of low-dose γ-secretase inhibitor treatment on intracellular oAβ accumulation. Low-dose treatment (2 and 20 nM) with DAPT increased the secretion of several Aβ peptides, especially Aβx-42. Furthermore, using the novel method for oAβ detection, we found that 2 nM DAPT treatment of cortical neurons resulted in increased oAβ accumulation. Thus, low dose-treatment with DAPT causes both increased production of long, aggregation-prone Aβ peptides and accumulation of intracellular Aβ oligomers, both believed to contribute to AD pathology.
Study of the in vitro modulation exerted by the antidepressant drug escitalopram on the expression of candidate microRNAs and their target genes Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-10-25 Elisabetta Maffioletti, Alessandro Salvi, Isabel Conde, Carlo Maj, Massimo Gennarelli, Giuseppina De Petro, Luisella Bocchio-Chiavetto
Recent studies indicated a role of microRNAs (miRNAs, small non-coding RNAs which regulate the expression of target genes by acting on mRNAs) in several neural processes, in the pathogenetic mechanisms of neuropsychiatric diseases and in the action of psychotropic drugs. A modulation induced by the antidepressant drug escitalopram on the expression levels of 30 miRNAs was highlighted in the blood of patients suffering from major depressive disorder. With the aim to investigate the effects of escitalopram in an in vitro model, we performed an analysis of the effects produced by escitalopram on the profiles of the 6 miRNAs found to be more significantly modulated in the above-mentioned study (miR-130b, miR-26a and -26b, let-7f, miR-770-5p, miR-34c-5p) in human U87 glioblastoma cells. Cells were treated with the drug for 24, 48 and 72 h. The obtained results confirmed a significant increase of let-7f, both after 48 (p = 0.031) and 72 h (p = 0.022), and of miR-26a after 48 h (p = 0.032). On the same experimental model, a transcriptome analysis was conducted after 72 h, highlighting a drug-induced modulation of 1184 protein-coding genes, 207 of which represent let-7f targets. Particularly interesting was the downregulation of BCOR, CCND1 and ATR, validated let-7f targets, which play a key role in the mechanisms of neurogenesis, neuroplasticity and protection from oxidative stress in the brain, indicating that escitalopram could exert downstream effects on gene expression through the regulation of specific miRNAs.
Corticosteroid-induced dendrite loss and behavioral deficiencies can be blocked by activation of Abl2/Arg kinase Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-10-26 Lauren P. Shapiro, Mitchell H. Omar, Anthony J. Koleske, Shannon L. Gourley
Stressor exposure induces neuronal remodeling in specific brain regions. Given the persistence of stress-related illnesses, key next steps in determining the contributions of neural structure to mental health are to identify cell types that fail to recover from stressor exposure and to identify “trigger points” and molecular underpinnings of stress-related neural degeneration. We evaluated dendrite arbor structure on hippocampal CA1 pyramidal neurons before, during, and following prolonged exposure to one key mediator of the stress response – corticosterone (cortisol in humans). Basal dendrite arbors progressively simplified during a 3-week exposure period, and failed to recover when corticosterone was withdrawn. Corticosterone exposure decreased levels of the dendrite stabilization factor Abl2/Arg nonreceptor tyrosine kinase and phosphorylation of its substrates p190RhoGAP and cortactin within 11 days, suggesting that disruption of Arg-mediated signaling may trigger dendrite arbor atrophy and, potentially, behavioral abnormalities resulting from corticosterone exposure. To test this, we administered the novel, bioactive Arg kinase activator, 5-(1,3-diaryl-1H-pyrazol-4-yl)hydantoin, 5-[3-(4-fluorophenyl)-1-phenyl-1H-pyrazol-4-yl]-2,4-imidazolidinedione (DPH), in conjunction with corticosterone. We found that repeated treatment corrected CA1 arbor structure, otherwise simplified by corticosterone. DPH also corrected corticosterone-induced errors in a hippocampal-dependent reversal learning task and anhedonic-like behavior. Thus, pharmacological compounds that target cytoskeletal regulators, rather than classical neurotransmitter systems, may interfere with stress-associated cognitive decline and mental health concerns.
The C-terminal domain of zDHHC2 contains distinct sorting signals that regulate intracellular localisation in neurons and neuroendocrine cells Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-07-30 Christine Salaun, Louise Ritchie, Jennifer Greaves, Trevor J. Bushell, Luke H. Chamberlain
The S-acyltransferase zDHHC2 mediates dynamic S-acylation of PSD95 and AKAP79/150, which impacts synaptic targeting of AMPA receptors. zDHHC2 is responsive to synaptic activity and catalyses the increased S-acylation of PSD95 that occurs following action potential blockade or application of ionotropic glutamate receptor antagonists. These treatments have been proposed to increase plasma membrane delivery of zDHHC2 via an endosomal cycling pathway, enhancing substrate accessibility. To generate an improved understanding of zDHHC2 trafficking and how this might be regulated by neuronal activity, we searched for intramolecular signals that regulate enzyme localisation. Two signals were mapped to the C-terminal tail of zDHHC2: a non-canonical dileucine motif [SxxxLL] and a downstream NP motif. Mutation of these signals enhanced plasma membrane accumulation of zDHHC2 in both neuroendocrine PC12 cells and rat hippocampal neurons, consistent with reduced endocytic retrieval. Furthermore, mutation of these signals also increased accumulation of the enzyme in neurites. Interestingly, several threonine and serine residues are adjacent to these sorting motifs and analysis of phospho-mimetic mutants highlighted a potential role for phosphorylation in regulating the efficacy of these signals. This study offers new molecular insight into the signals that determine zDHHC2 localisation and highlights a potential mechanism to regulate these trafficking signals.
Nervous system development and disease: A focus on trithorax related proteins and chromatin remodelers Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-11-28 Amanda Moccia, Donna M. Martin
The nervous system comprises many different cell types including neurons, glia, macrophages, and immune cells, each of which is defined by specific patterns of gene expression, morphology, function, and anatomical location. Establishment of these complex and highly regulated cell fates requires spatial and temporal coordination of gene transcription. Open chromatin (euchromatin) allows transcription factors to interact with gene promoters and activate lineage specific genes, whereas closed chromatin (heterochromatin) remains inaccessible to transcriptional activation. Changes in the genome-wide distribution of euchromatin accompany transcriptional plasticity that allows the diversity of mature cell fates to be generated during development. In the past 20 years, many new genes and gene families have been identified to participate in regulation of chromatin accessibility. These genes include chromatin remodelers that interact with Trithorax group (TrxG) and Polycomb group (PcG) proteins to activate or repress transcription, respectively. Here we review the role of TrxG proteins in neurodevelopment and disease.
Actin-based growth cone motility and guidance Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-03-06 Omotola F. Omotade, Stephanie L. Pollitt, James Q. Zheng
Nerve growth cones, the dilated tip of developing axons, are equipped with exquisite abilities to sense environmental cues and to move rapidly through complex terrains of developing brain, leading the axons to their specific targets for precise neuronal wiring. The actin cytoskeleton is the major component of the growth cone that powers its directional motility. Past research has provided significant insights into the mechanisms by which growth cones translate extracellular signals into directional migration. In this review, we summarize the actin-based mechanisms underlying directional growth cone motility, examine novel findings, and discuss the outstanding questions concerning the actin-based growth cone behaviors.
Neuronal polarization: From spatiotemporal signaling to cytoskeletal dynamics Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-03-28 Max Schelski, Frank Bradke
Neuronal polarization establishes distinct molecular structures to generate a single axon and multiple dendrites. Studies over the past years indicate that this efficient separation is brought about by a network of feedback loops. Axonal growth seems to play a major role in fueling those feedback loops and thereby stabilizing neuronal polarity. Indeed, various effectors involved in feedback loops are pivotal for axonal growth by ultimately acting on the actin and microtubule cytoskeleton. These effectors have key roles in interconnecting actin and microtubule dynamics – a mechanism crucial to commanding the growth of axons. We propose a model connecting signaling with cytoskeletal dynamics and neurite growth to better describe the underlying processes involved in neuronal polarization. We will discuss the current views on feedback loops and highlight the current limits of our understanding.
How does calcium interact with the cytoskeleton to regulate growth cone motility during axon pathfinding? Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-07-29 Robert J. Gasperini, Macarena Pavez, Adrian C. Thompson, Camilla B. Mitchell, Holly Hardy, Kaylene M. Young, John K. Chilton, Lisa Foa
The precision with which neurons form connections is crucial for the normal development and function of the nervous system. The development of neuronal circuitry in the nervous system is accomplished by axon pathfinding: a process where growth cones guide axons through the embryonic environment to connect with their appropriate synaptic partners to form functional circuits. Despite intense efforts over many years to understand how this process is regulated, the complete repertoire of molecular mechanisms that govern the growth cone cytoskeleton and hence motility, remain unresolved. A central tenet in the axon guidance field is that calcium signals regulate growth cone behaviours such as extension, turning and pausing by regulating rearrangements of the growth cone cytoskeleton. Here, we provide evidence that not only the amplitude of a calcium signal is critical for growth cone motility but also the source of calcium mobilisation. We provide an example of this idea by demonstrating that manipulation of calcium signalling via L-type voltage gated calcium channels can perturb sensory neuron motility towards a source of netrin-1. Understanding how calcium signals can be transduced to initiate cytoskeletal changes represents a significant gap in our current knowledge of the mechanisms that govern axon guidance, and consequently the formation of functional neural circuits in the developing nervous system.
It takes a village to raise a branch: Cellular mechanisms of the initiation of axon collateral branches Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-03-27 Lorena Armijo-Weingart, Gianluca Gallo
The formation of axon collateral branches from the pre-existing shafts of axons is an important aspect of neurodevelopment and the response of the nervous system to injury. This article provides an overview of the role of the cytoskeleton and signaling mechanisms in the formation of axon collateral branches. Both the actin filament and microtubule components of the cytoskeleton are required for the formation of axon branches. Recent work has begun to shed light on how these two elements of the cytoskeleton are integrated by proteins that functionally or physically link the cytoskeleton. While a number of signaling pathways have been determined as having a role in the formation of axon branches, the complexity of the downstream mechanisms and links to specific signaling pathways remain to be fully determined. The regulation of intra-axonal protein synthesis and organelle function are also emerging as components of signal-induced axon branching. Although much has been learned in the last couple of decades about the mechanistic basis of axon branching we can look forward to continue elucidating this complex biological phenomenon with the aim of understanding how multiple signaling pathways, cytoskeletal regulators and organelles are coordinated locally along the axon to give rise to a branch.
Actin regulation by tropomodulin and tropomyosin in neuronal morphogenesis and function Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-04-19 Kevin T. Gray, Alla S. Kostyukova, Thomas Fath
Actin is a profoundly influential protein; it impacts, among other processes, membrane morphology, cellular motility, and vesicle transport. Actin can polymerize into long filaments that push on membranes and provide support for intracellular transport. Actin filaments have polar ends: the fast-growing (barbed) end and the slow-growing (pointed) end. Depolymerization from the pointed end supplies monomers for further polymerization at the barbed end. Tropomodulins (Tmods) cap pointed ends by binding onto actin and tropomyosins (Tpms). Tmods and Tpms have been shown to regulate many cellular processes; however, very few studies have investigated their joint role in the nervous system. Recent data directly indicate that they can modulate neuronal morphology. Additional studies suggest that Tmod and Tpm impact molecular processes influential in synaptic signaling. To facilitate future research regarding their joint role in actin regulation in the nervous system, we will comprehensively discuss Tpm and Tmod and their known functions within molecular systems that influence neuronal development.
Tubulins and brain development – The origins of functional specification Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-03-27 Martin W. Breuss, Ines Leca, Thomas Gstrein, Andi H. Hansen, David A. Keays
The development of the vertebrate central nervous system is reliant on a complex cascade of biological processes that include mitotic division, relocation of migrating neurons, and the extension of dendritic and axonal processes. Each of these cellular events requires the diverse functional repertoire of the microtubule cytoskeleton for the generation of forces, assembly of macromolecular complexes and transport of molecules and organelles. The tubulins are a multi-gene family that encode for the constituents of microtubules, and have been implicated in a spectrum of neurological disorders. Evidence is building that different tubulins tune the functional properties of the microtubule cytoskeleton dependent on the cell type, developmental profile and subcellular localisation. Here we review of the origins of the functional specification of the tubulin gene family in the developing brain at a transcriptional, translational, and post-transcriptional level. We remind the reader that tubulins are not just loading controls for your average Western blot.
The third wave: Intermediate filaments in the maturing nervous system Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-05-26 Matthew T.K. Kirkcaldie, Samuel T. Dwyer
Intermediate filaments are critical for the extreme structural specialisations of neurons, providing integrity in dynamic environments and efficient communication along axons a metre or more in length. As neurons mature, an initial expression of nestin and vimentin gives way to the neurofilament triplet proteins and α-internexin, substituted by peripherin in axons outside the CNS, which physically consolidate axons as they elongate and find their targets. Once connection is established, these proteins are transported, assembled, stabilised and modified, structurally transforming axons and dendrites as they acquire their full function. The interaction between these neurons and myelinating glial cells optimises the structure of axons for peak functional efficiency, a property retained across their lifespan. This finely calibrated structural regulation allows the nervous system to maintain timing precision and efficient control across large distances throughout somatic growth and, in maturity, as a plasticity mechanism allowing functional adaptation.
New waves in dendritic spine actin cytoskeleton: From branches and bundles to rings, from actin binding proteins to post-translational modifications Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-05-04 Enni Bertling, Pirta Hotulainen
Dendritic spines are small actin-rich protrusions from neuronal dendrites that form the postsynaptic part of most excitatory synapses. Changes in the number or strength of synapses are physiological mechanisms behind learning. The growth and maturation of dendritic spines and the activity-induced changes to their morphology are all based on changes to the actin cytoskeleton. In this review, we will discuss the regulation of the actin cytoskeleton in dendritic spine formation and maturation, as well as in synaptic strengthening. Concerning spine formation, we will focus on spine initiation, which has received less attention in the literature. We will also examine the recently revealed regulation of the actin cytoskeleton through post-translational modifications of actin monomers, in addition to the conventional regulation of actin via actin-binding proteins.
The role of drebrin in dendritic spines Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-02-01 Noriko Koganezawa, Kenji Hanamura, Yuko Sekino, Tomoaki Shirao
Dendritic spines form typical excitatory synapses in the brain and their shapes vary depending on synaptic inputs. It has been suggested that the morphological changes of dendritic spines play an important role in synaptic plasticity. Dendritic spines contain a high concentration of actin, which has a central role in supporting cell motility, and polymerization of actin filaments (F-actin) is most likely involved in spine shape changes. Drebrin is an actin-binding protein that forms stable F-actin and is highly accumulated within dendritic spines. Drebrin has two isoforms, embryonic-type drebrin E and adult-type drebrin A, that change during development from E to A. Inhibition of drebrin A expression results in a delay of synapse formation and inhibition of postsynaptic protein accumulation, suggesting that drebrin A has an important role in spine maturation. In mature synapses, glutamate stimulation induces rapid spine-head enlargement during long-term potentiation (LTP) formation. LTP stimulation induces Ca2 + entry through N-methyl-d-aspartate (NMDA) receptors, which causes drebrin exodus from dendritic spines. Once drebrin exits from dendritic spine heads, the dynamic actin pool increases in spine heads to facilitate F-actin polymerization. To maintain enlarged spine heads, drebrin-decorated F-actin is thought to reform within the spine heads. Thus, drebrin plays a pivotal role in spine plasticity through regulation of F-actin.
Membrane shaping by actin and myosin during regulated exocytosis Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-05-20 Andreas Papadopulos
The cortical actin network in neurosecretory cells is a dense mesh of actin filaments underlying the plasma membrane. Interaction of actomyosin with vesicular membranes or the plasma membrane is vital for tethering, retention, transport as well as fusion and fission of exo- and endocytic membrane structures. During regulated exocytosis the cortical actin network undergoes dramatic changes in morphology to accommodate vesicle docking, fusion and replenishment. Most of these processes involve plasma membrane Phosphoinositides (PIP) and investigating the interactions between the actin cortex and secretory structures has become a hotbed for research in recent years. Actin remodelling leads to filopodia outgrowth and the creation of new fusion sites in neurosecretory cells and actin, myosin and dynamin actively shape and maintain the fusion pore of secretory vesicles. Changes in viscoelastic properties of the actin cortex can facilitate vesicular transport and lead to docking and priming of vesicle at the plasma membrane. Small GTPase actin mediators control the state of the cortical actin network and influence vesicular access to their docking and fusion sites. These changes potentially affect membrane properties such as tension and fluidity as well as the mobility of embedded proteins and could influence the processes leading to both exo- and endocytosis. Here we discuss the multitudes of actin and membrane interactions that control successive steps underpinning regulated exocytosis.
ENA/VASP proteins regulate exocytosis by mediating myosin VI-dependent recruitment of secretory granules to the cortical actin network Mol. Cell. Neurosci. (IF 3.084) Pub Date : 2017-08-07 Vanesa M. Tomatis, Peter Josh, Andreas Papadopulos, Rachel S. Gormal, Vanessa Lanoue, Sally Martin, Frédéric A. Meunier
In neurosecretory cells, myosin VI associated with secretory granules (SGs) mediates their activity-dependent recruitment to the cortical actin network and is necessary to sustain exocytosis. The mechanism by which myosin VI interacts with SGs is unknown. Using a myosin VI pull-down assay and mass spectrometry we identified Mena, a member of the ENA/VASP family, as a myosin VI binding partner in PC12 cells, and confirmed that Mena colocalized with myosin VI on SGs. Using a knock-sideways approach to inactivate the ENA/VASP family members by mitochondrial relocation, we revealed a concomitant redistribution of myosin VI. This was ensued by a reduction in the association of myosin VI with SGs, a decreased SG mobility and density in proximity to the plasma membrane as well as decreased evoked exocytosis. These data demonstrate that ENA/VASP proteins regulate SG exocytosis through modulating the activity of myosin VI.
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