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  • Genetic basis of oxygen sensing in the carotid body: HIF2α and an isoform switch in cytochrome c oxidase subunit 4
    Sci. Signal. (IF 6.481) Pub Date : 2020-01-21
    Tammie Bishop, Peter J. Ratcliffe

    The mechanistic basis of the marked oxygen sensitivity of glomus cells in the carotid body has long puzzled physiologists. In this issue of Science Signaling, Moreno-Domínguez et al. show the critical importance of high levels of hypoxia-inducible factor, HIF2α/EPAS1, and the nuclear-encoded mitochondrial cytochrome c oxidase subunit, COX4I2, in glomus cell sensitivity to hypoxia.

    更新日期:2020-01-22
  • Spatial and temporal alterations in protein structure by EGF regulate cryptic cysteine oxidation
    Sci. Signal. (IF 6.481) Pub Date : 2020-01-21
    Jessica B. Behring, Sjoerd van der Post, Arshag D. Mooradian, Matthew J. Egan, Maxwell I. Zimmerman, Jenna L. Clements, Gregory R. Bowman, Jason M. Held

    Stimulation of plasma membrane receptor tyrosine kinases (RTKs), such as the epidermal growth factor receptor (EGFR), locally increases the abundance of reactive oxygen species (ROS). These ROS then oxidize cysteine residues in proteins to potentiate downstream signaling. Spatial confinement of ROS is an important regulatory mechanism of redox signaling that enables the stimulation of different RTKs to oxidize distinct sets of downstream proteins. To uncover additional mechanisms that specify cysteines that are redox regulated by EGF stimulation, we performed time-resolved quantification of the EGF-dependent oxidation of 4200 cysteine sites in A431 cells. Fifty-one percent of cysteines were statistically significantly oxidized by EGF stimulation. Furthermore, EGF induced three distinct spatiotemporal patterns of cysteine oxidation in functionally organized protein networks, consistent with the spatial confinement model. Unexpectedly, protein crystal structure analysis and molecular dynamics simulations indicated widespread redox regulation of cryptic cysteine residues that are solvent exposed only upon changes in protein conformation. Phosphorylation and increased flux of nucleotide substrates served as two distinct modes by which EGF specified the cryptic cysteine residues that became solvent exposed and redox regulated. Because proteins that are structurally regulated by different RTKs or cellular perturbations are largely unique, these findings suggest that solvent exposure and redox regulation of cryptic cysteine residues contextually delineate redox signaling networks.

    更新日期:2020-01-22
  • Ca2+ waves coordinate purinergic receptor–evoked integrin activation and polarization
    Sci. Signal. (IF 6.481) Pub Date : 2020-01-21
    Alexander P. Bye, Jonathan M. Gibbins, Martyn P. Mahaut-Smith

    Cells sense extracellular nucleotides through the P2Y class of purinergic G protein–coupled receptors (GPCRs), which stimulate integrin activation through signaling events, including intracellular Ca2+ mobilization. We investigated the relationship between P2Y-stimulated repetitive Ca2+ waves and fibrinogen binding to the platelet integrin αIIbβ3 (GPIIb/IIIa) through confocal fluorescence imaging of primary rat megakaryocytes. Costimulation of the receptors P2Y1 and P2Y12 generated a series of Ca2+ transients that each induced a rapid, discrete increase in fibrinogen binding. The peak and net increase of individual fibrinogen binding events correlated with the Ca2+ transient amplitude and frequency, respectively. Using BAPTA loading and selective receptor antagonists, we found that Ca2+ mobilization downstream of P2Y1 was essential for ADP-evoked fibrinogen binding, whereas P2Y12 and the kinase PI3K were also required for αIIbβ3 activation and enhanced the number of Ca2+ transients. ADP-evoked fibrinogen binding was initially uniform over the cell periphery but subsequently redistributed with a polarity that correlated with the direction of the Ca2+ waves. Polarization of αIIbβ3 may be mediated by the actin cytoskeleton, because surface-bound fibrinogen is highly immobile, and its motility was enhanced by cytoskeletal disruption. In conclusion, spatial and temporal patterns of Ca2+ increase enable fine control of αIIbβ3 activation after cellular stimulation. P2Y1-stimulated Ca2+ transients coupled to αIIbβ3 activation only in the context of P2Y12 coactivation, thereby providing an additional temporal mechanism of synergy between these Gq- and Gi-coupled GPCRs.

    更新日期:2020-01-22
  • Too much stretching is bad for the lungs
    Sci. Signal. (IF 6.481) Pub Date : 2020-01-21
    Wei Wong

    Excessive mechanical strain on alveolar stem cells induces TGF-β signaling and progressive lung fibrosis.

    更新日期:2020-01-22
  • Acute O2 sensing through HIF2α-dependent expression of atypical cytochrome oxidase subunits in arterial chemoreceptors
    Sci. Signal. (IF 6.481) Pub Date : 2020-01-21
    Alejandro Moreno-Domínguez, Patricia Ortega-Sáenz, Lin Gao, Olalla Colinas, Paula García-Flores, Victoria Bonilla-Henao, Julián Aragonés, Maik Hüttemann, Lawrence I. Grossman, Norbert Weissmann, Natascha Sommer, José López-Barneo

    Acute cardiorespiratory responses to O2 deficiency are essential for physiological homeostasis. The prototypical acute O2-sensing organ is the carotid body, which contains glomus cells expressing K+ channels whose inhibition by hypoxia leads to transmitter release and activation of nerve fibers terminating in the brainstem respiratory center. The mechanism by which changes in O2 tension modulate ion channels has remained elusive. Glomus cells express genes encoding HIF2α (Epas1) and atypical mitochondrial subunits at high levels, and mitochondrial NADH and reactive oxygen species (ROS) accumulation during hypoxia provides the signal that regulates ion channels. We report that inactivation of Epas1 in adult mice resulted in selective abolition of glomus cell responsiveness to acute hypoxia and the hypoxic ventilatory response. Epas1 deficiency led to the decreased expression of atypical mitochondrial subunits in the carotid body, and genetic deletion of Cox4i2 mimicked the defective hypoxic responses of Epas1-null mice. These findings provide a mechanistic explanation for the acute O2 regulation of breathing, reveal an unanticipated role of HIF2α, and link acute and chronic adaptive responses to hypoxia.

    更新日期:2020-01-22
  • Single-molecule imaging reveals the oligomeric state of functional TNFα-induced plasma membrane TNFR1 clusters in cells
    Sci. Signal. (IF 6.481) Pub Date : 2020-01-14
    Christos Karathanasis, Juliane Medler, Franziska Fricke, Sonja Smith, Sebastian Malkusch, Darius Widera, Simone Fulda, Harald Wajant, Sjoerd J. L. van Wijk, Ivan Dikic, Mike Heilemann

    Ligand-induced tumor necrosis factor receptor 1 (TNFR1) activation controls nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) signaling, cell proliferation, programmed cell death, and survival and is crucially involved in inflammation, autoimmune disorders, and cancer progression. Despite the relevance of TNFR1 clustering for signaling, oligomerization of ligand-free and ligand-activated TNFR1 remains controversial. At present, models range from ligand-independent receptor predimerization to ligand-induced oligomerization. Here, we used quantitative, single-molecule superresolution microscopy to study TNFR1 assembly directly in native cellular settings and at physiological cell surface abundance. In the absence of its ligand TNFα, TNFR1 assembled into monomeric and dimeric receptor units. Upon binding of TNFα, TNFR1 clustered predominantly not only into trimers but also into higher-order oligomers. A functional mutation in the preligand assembly domain of TNFR1 resulted in only monomeric TNFR1, which exhibited impaired ligand binding. In contrast, a form of TNFR1 with a mutation in the ligand-binding CRD2 subdomain retained the monomer-to-dimer ratio of the unliganded wild-type TNFR1 but exhibited no ligand binding. These results underscore the importance of ligand-independent TNFR1 dimerization in NF-κB signaling.

    更新日期:2020-01-15
  • Predicting resistance to KRAS inhibitors
    Sci. Signal. (IF 6.481) Pub Date : 2020-01-14
    Leslie K. Ferrarelli

    Studies identify common targets for preventing resistance to KRAS inhibitors.

    更新日期:2020-01-15
  • The Vibrio cholerae MARTX toxin silences the inflammatory response to cytoskeletal damage before inducing actin cytoskeleton collapse
    Sci. Signal. (IF 6.481) Pub Date : 2020-01-14
    Patrick J. Woida, Karla J. F. Satchell

    Multifunctional autoprocessing repeats-in-toxin (MARTX) toxins are pore-forming bacterial toxins that translocate multiple functionally independent effector domains into a target eukaryotic cell. Vibrio cholerae colonizes intestinal epithelial cells (IECs) and uses a MARTX toxin with three effector domains—an actin cross-linking domain (ACD), a Rho inactivation domain (RID), and an α/β hydrolase domain (ABH)—to suppress innate immunity and enhance colonization. We investigated whether these multiple catalytic enzymes delivered from a single toxin functioned in a coordinated manner to suppress intestinal innate immunity. Using cultured human IECs, we demonstrated that ACD-induced cytoskeletal collapse activated extracellular signal–regulated kinase, p38, and c-Jun amino-terminal kinase mitogen-activated protein kinase (MAPK) signaling to elicit a robust proinflammatory response characterized by the secretion of interleukin-8 (IL-8; also called CXCL8) and the expression of CXCL8, tumor necrosis factor (TNF), and other proinflammatory genes. However, RID and ABH, which are naturally delivered together with ACD, blocked MAPK activation through Rac1 and thus prevented ACD-induced inflammation. RID also abolished IL-8 secretion induced by heat-killed bacteria, TNF, or latrunculin A. Thus, MARTX toxins use enzymatic multifunctionality to silence the host response to bacterial factors and to the damage caused by the toxins. Furthermore, these data show how V. cholerae MARTX toxin suppresses intestinal inflammation and contributes to cholera being classically defined as a noninflammatory diarrheal disease.

    更新日期:2020-01-15
  • Cracking the context-specific PI3K signaling code
    Sci. Signal. (IF 6.481) Pub Date : 2020-01-07
    Ralitsa R. Madsen, Bart Vanhaesebroeck

    Specificity in signal transduction is determined by the ability of cells to “encode” and subsequently “decode” different environmental signals. Akin to computer software, this “signaling code” governs context-dependent execution of cellular programs through modulation of signaling dynamics and can be corrupted by disease-causing mutations. Class IA phosphoinositide 3-kinase (PI3K) signaling is critical for normal growth and development and is dysregulated in human disorders such as benign overgrowth syndromes, cancer, primary immune deficiency, and metabolic syndrome. Despite decades of PI3K research, understanding of context-dependent regulation of the PI3K pathway and of the underlying signaling code remains rudimentary. Here, we review current knowledge on context-specific PI3K signaling and how technological advances now make it possible to move from a qualitative to quantitative understanding of this pathway. Insight into how cellular PI3K signaling is encoded or decoded may open new avenues for rational pharmacological targeting of PI3K-associated diseases. The principles of PI3K context-dependent signal encoding and decoding described here are likely applicable to most, if not all, major cell signaling pathways.

    更新日期:2020-01-07
  • The GPCR accessory protein MRAP2 regulates both biased signaling and constitutive activity of the ghrelin receptor GHSR1a
    Sci. Signal. (IF 6.481) Pub Date : 2020-01-07
    Alix A. J. Rouault, Luciana K. Rosselli-Murai, Ciria C. Hernandez, Luis E. Gimenez, Gregory G. Tall, Julien A. Sebag

    Ghrelin is a hormone secreted by the stomach during fasting periods and acts through its receptor, the growth hormone secretagogue 1a (GHSR1a), to promote food intake and prevent hypoglycemia. As such, GHSR1a is an important regulator of energy and glucose homeostasis and a target for the treatment of obesity. Here, we showed that the accessory protein MRAP2 altered GHSR1a signaling by inhibiting its constitutive activity, as well as by enhancing its G protein–dependent signaling and blocking the recruitment and signaling of β-arrestin in response to ghrelin. In addition, the effects of MRAP2 on the Gαq and β-arrestin pathways were independent and involved distinct regions of MRAP2. These findings may have implications for the regulation of ghrelin function in vivo and the role of MRAP2 in energy homeostasis. They also show that accessory proteins can bias signaling downstream of GPCRs in response to their endogenous agonist.

    更新日期:2020-01-07
  • Hereditary spastic paraplegia SPG8 mutations impair CAV1-dependent, integrin-mediated cell adhesion
    Sci. Signal. (IF 6.481) Pub Date : 2020-01-07
    Seongju Lee, Hyungsun Park, Peng-Peng Zhu, Soon-Young Jung, Craig Blackstone, Jaerak Chang

    Mutations in WASHC5 (also known as KIAA0196) cause autosomal dominant hereditary spastic paraplegia (HSP) type SPG8. WASHC5, commonly called strumpellin, is a core component of the Wiskott-Aldrich syndrome protein and SCAR homolog (WASH) complex that activates actin nucleation at endosomes. Although various other cellular roles for strumpellin have also been described, none account for how SPG8-associated mutations lead to HSP. Here, we identified protein interactors of the WASH complex by immunoprecipitation and mass spectrometry and assessed the functions of strumpellin in cultured cells using both overexpression and RNA interference along with cell-spreading assays to investigate cell adhesion. We uncovered a decrease in CAV1 protein abundance as well as endosomal fission defects resulting from pathogenic SPG8 mutations. CAV1, a key component of caveolae, interacted with strumpellin in cells, and strumpellin inhibited the lysosomal degradation of CAV1. SPG8-associated missense mutations in strumpellin did not rescue endosomal tubulation defects, reduction in CAV1 protein abundance, or integrin-mediated cell adhesion in strumpellin-deficient cells. Mechanistically, we demonstrated that the WASH complex maintained CAV1 and integrin protein amounts by inhibiting their lysosomal degradation through its endosomal actin nucleation activity. In addition, the interaction of strumpellin with CAV1 stimulated integrin recycling, thereby promoting cell adhesion. These findings provide a molecular link between WASHC5 mutations and impairment of CAV1- and integrin-mediated cell adhesion, providing insights into the cellular pathogenesis of SPG8.

    更新日期:2020-01-07
  • Hexokinase 2 couples glycolysis with the profibrotic actions of TGF-β
    Sci. Signal. (IF 6.481) Pub Date : 2019-12-17
    Xueqian Yin, Malay Choudhury, Jeong-Han Kang, Kyle J. Schaefbauer, Mi-Yeon Jung, Mahefatiana Andrianifahanana, Danielle M. Hernandez, Edward B. Leof

    Metabolic dysregulation in fibroblasts is implicated in the profibrotic actions of transforming growth factor–β (TGF-β). Here, we present evidence that hexokinase 2 (HK2) is important for mediating the fibroproliferative activity of TGF-β both in vitro and in vivo. Both Smad-dependent and Smad-independent TGF-β signaling induced HK2 accumulation in murine and human lung fibroblasts through induction of the transcription factor c-Myc. Knockdown of HK2 or pharmacological inhibition of HK2 activity with Lonidamine decreased TGF-β–stimulated fibrogenic processes, including profibrotic gene expression, cell migration, colony formation, and activation of the transcription factors YAP and TAZ, with no apparent effect on cellular viability. Fibroblasts from patients with idiopathic pulmonary fibrosis (IPF) exhibited an increased abundance of HK2. In a mouse model of bleomycin-induced lung fibrosis, Lonidamine reduced the expression of genes encoding profibrotic markers (collagenΙα1, EDA-fibronectin, α smooth muscle actin, and connective tissue growth factor) and stabilized or improved lung function as assessed by measurement of peripheral blood oxygenation. These findings provide evidence of how metabolic dysregulation through HK2 can be integrated within the context of profibrotic TGF-β signaling.

    更新日期:2019-12-18
  • Distinguishing friend from foe
    Sci. Signal. (IF 6.481) Pub Date : 2019-12-17
    Annalisa M. VanHook

    Toxin-stimulated immune signaling helps neonatal mice distinguish between harmless skin colonizers and potential pathogens.

    更新日期:2019-12-18
  • Signaling from mTOR to eIF2α mediates cell migration in response to the chemotherapeutic doxorubicin
    Sci. Signal. (IF 6.481) Pub Date : 2019-12-17
    Robert F. Harvey, Tuija A. A. Pöyry, Mark Stoneley, Anne E. Willis

    After exposure to cytotoxic chemotherapeutics, tumor cells alter their translatome to promote cell survival programs through the regulation of eukaryotic initiation factor 4F (eIF4F) and ternary complex. Compounds that block mTOR signaling and eIF4F complex formation, such as rapamycin and its analogs, have been used in combination therapies to enhance cell killing, although their success has been limited. This is likely because the cross-talk between signaling pathways that coordinate eIF4F regulation with ternary complex formation after treatment with genotoxic therapeutics has not been fully explored. Here, we described a regulatory pathway downstream of p53 in which inhibition of mTOR after DNA damage promoted cross-talk signaling and led to eIF2α phosphorylation. We showed that eIF2α phosphorylation did not inhibit protein synthesis but was instead required for cell migration and that pharmacologically blocking this pathway with either ISRIB or trazodone limited cell migration. These results support the notion that therapeutic targeting of eIF2α signaling could restrict tumor cell metastasis and invasion and could be beneficial to subsets of patients with cancer.

    更新日期:2019-12-18
  • Genetic diversity affects the nanoscale membrane organization and signaling of natural killer cell receptors
    Sci. Signal. (IF 6.481) Pub Date : 2019-12-17
    Philippa R. Kennedy, Charlotte Barthen, David J. Williamson, William T. E. Pitkeathly, Khodor S. Hazime, Joshua Cumming, Kevin B. Stacey, Hugo G. Hilton, Mary Carrington, Peter Parham, Daniel M. Davis

    Genetic diversity in human natural killer (NK) cell receptors is linked to resistance and susceptibility to many diseases. Here, we tested the effect of this diversity on the nanoscale organization of killer cell immunoglobulin-like receptors (KIRs). Using superresolution microscopy, we found that inhibitory KIRs encoded by different genes and alleles were organized differently at the surface of primary human NK cells. KIRs that were found at low abundance assembled into smaller clusters than those formed by KIRs that were more highly abundant, and at low abundance, there was a greater proportion of KIRs in clusters. Upon receptor triggering, a structured interface called the immune synapse assembles, which facilitates signal integration and controls NK cell responses. Here, triggering of low-abundance receptors resulted in less phosphorylation of the downstream phosphatase SHP-1 but more phosphorylation of the adaptor protein Crk than did triggering of high-abundance receptors. In cells with greater KIR abundance, SHP-1 dephosphorylated Crk, which potentiated NK cell spreading during activation. Thus, genetic variation modulates both the abundance and nanoscale organization of inhibitory KIRs. That is, as well as the number of receptors at the cell surface varying with genotype, the way in which these receptors are organized in the membrane also varies. Essentially, a change in the average surface abundance of a protein at the cell surface is a coarse descriptor entwined with changes in local nanoscale clustering. Together, our data indicate that genetic diversity in inhibitory KIRs affects membrane-proximal signaling and, unexpectedly, the formation of activating immune synapses.

    更新日期:2019-12-18
  • Mutations that TANK a kinase
    Sci. Signal. (IF 6.481) Pub Date : 2019-12-10
    John F. Foley

    ALS-associated mutations in the kinase TBK1 with the same pathological outcome affect distinct signaling pathways.

    更新日期:2019-12-11
  • A direct heterotypic interaction between the DIX domains of Dishevelled and Axin mediates signaling to β-catenin
    Sci. Signal. (IF 6.481) Pub Date : 2019-12-10
    Kumpei Yamanishi, Marc Fiedler, Shin-ichi Terawaki, Yoshiki Higuchi, Mariann Bienz, Naoki Shibata

    The Wnt–β-catenin signaling pathway regulates embryonic development and tissue homeostasis throughout the animal kingdom. Signaling through this pathway crucially depends on the opposing activities of two cytoplasmic multiprotein complexes: the Axin destruction complex, which destabilizes the downstream effector β-catenin, and the Dishevelled signalosome, which inactivates the Axin complex and thus enables β-catenin to accumulate and operate a transcriptional switch in the nucleus. These complexes are assembled by dynamic head-to-tail polymerization of the DIX domains of Axin or Dishevelled, respectively, which increases their avidity for signaling effectors. Axin also binds to Dishevelled through its DIX domain. Here, we report the crystal structure of the heterodimeric complex between the two DIX domains of Axin and Dishevelled. This heterotypic interface resembles the interfaces observed in the individual homopolymers, albeit exhibiting a slight rearrangement of electrostatic interactions and hydrogen bonds, consistent with the heterotypic interaction being favored over the homotypic Axin DIX interaction. Last, cell-based signaling assays showed that heterologous polymerizing domains functionally substituted for the DIX domain of Dishevelled provided that these Dishevelled chimeras retained a DIX head or tail surface capable of binding to Axin. These findings indicate that the interaction between Dishevelled and Axin through their DIX domains is crucial for signaling to β-catenin.

    更新日期:2019-12-11
  • Metabolic rewiring of the hypertensive kidney
    Sci. Signal. (IF 6.481) Pub Date : 2019-12-10
    Markus M. Rinschen, Oleg Palygin, Carlos Guijas, Amelia Palermo, Nicolas Palacio-Escat, Xavier Domingo-Almenara, Rafael Montenegro-Burke, Julio Saez-Rodriguez, Alexander Staruschenko, Gary Siuzdak

    Hypertension is a persistent epidemic across the developed world that is closely associated with kidney disease. Here, we applied a metabolomic, phosphoproteomic, and proteomic strategy to analyze the effect of hypertensive insults on kidneys. Our data revealed the metabolic aspects of hypertension-induced glomerular sclerosis, including lipid breakdown at early disease stages and activation of anaplerotic pathways to regenerate energy equivalents to counter stress. For example, branched-chain amino acids and proline, required for collagen synthesis, were depleted in glomeruli at early time points. Furthermore, indicators of metabolic stress were reflected by low amounts of ATP and NADH and an increased abundance of oxidized lipids derived from lipid breakdown. These processes were specific to kidney glomeruli where metabolic signaling occurred through mTOR and AMPK signaling. Quantitative phosphoproteomics combined with computational modeling suggested that these processes controlled key molecules in glomeruli and specifically podocytes, including cytoskeletal components and GTP-binding proteins, which would be expected to compete for decreasing amounts of GTP at early time points. As a result, glomeruli showed increased expression of metabolic enzymes of central carbon metabolism, amino acid degradation, and lipid oxidation, findings observed in previously published studies from other disease models and patients with glomerular damage. Overall, multilayered omics provides an overview of hypertensive kidney damage and suggests that metabolic or dietary interventions could prevent and treat glomerular disease and hypertension-induced nephropathy.

    更新日期:2019-12-11
  • Hypusine biosynthesis in β cells links polyamine metabolism to facultative cellular proliferation to maintain glucose homeostasis
    Sci. Signal. (IF 6.481) Pub Date : 2019-12-03
    Esther M. Levasseur, Kentaro Yamada, Annie R. Piñeros, Wenting Wu, Farooq Syed, Kara S. Orr, Emily Anderson-Baucum, Teresa L. Mastracci, Bernhard Maier, Amber L. Mosley, Yunlong Liu, Ernesto Bernal-Mizrachi, Laura C. Alonso, Donald Scott, Adolfo Garcia-Ocaña, Sarah A. Tersey, Raghavendra G. Mirmira

    Deoxyhypusine synthase (DHPS) uses the polyamine spermidine to catalyze the hypusine modification of the mRNA translation factor eIF5A and promotes oncogenesis through poorly defined mechanisms. Because germline deletion of Dhps is embryonically lethal, its role in normal postnatal cellular function in vivo remains unknown. We generated a mouse model that enabled the inducible, postnatal deletion of Dhps specifically in postnatal islet β cells, which function to maintain glucose homeostasis. Removal of Dhps did not have an effect under normal physiologic conditions. However, upon development of insulin resistance, which induces β cell proliferation, Dhps deletion caused alterations in proteins required for mRNA translation and protein secretion, reduced production of the cell cycle molecule cyclin D2, impaired β cell proliferation, and induced overt diabetes. We found that hypusine biosynthesis was downstream of protein kinase C-ζ and was required for c-Myc–induced proliferation. Our studies reveal a requirement for DHPS in β cells to link polyamines to mRNA translation to effect facultative cellular proliferation and glucose homeostasis.

    更新日期:2019-12-04
  • Biased M1 receptor–positive allosteric modulators reveal role of phospholipase D in M1-dependent rodent cortical plasticity
    Sci. Signal. (IF 6.481) Pub Date : 2019-12-03
    Sean P. Moran, Zixiu Xiang, Catherine A. Doyle, James Maksymetz, Xiaohui Lv, Sehr Faltin, Nicole M. Fisher, Colleen M. Niswender, Jerri M. Rook, Craig W. Lindsley, P. Jeffrey Conn

    Highly selective, positive allosteric modulators (PAMs) of the M1 subtype of muscarinic acetylcholine receptor have emerged as an exciting new approach to potentially improve cognitive function in patients suffering from Alzheimer’s disease and schizophrenia. Discovery programs have produced a structurally diverse range of M1 receptor PAMs with distinct pharmacological properties, including different extents of agonist activity and differences in signal bias. This includes biased M1 receptor PAMs that can potentiate coupling of the receptor to activation of phospholipase C (PLC) but not phospholipase D (PLD). However, little is known about the role of PLD in M1 receptor signaling in native systems, and it is not clear whether biased M1 PAMs display differences in modulating M1-mediated responses in native tissue. Using PLD inhibitors and PLD knockout mice, we showed that PLD was necessary for the induction of M1-dependent long-term depression (LTD) in the prefrontal cortex (PFC). Furthermore, biased M1 PAMs that did not couple to PLD not only failed to potentiate orthosteric agonist–induced LTD but also blocked M1-dependent LTD in the PFC. In contrast, biased and nonbiased M1 PAMs acted similarly in potentiating M1-dependent electrophysiological responses that were PLD independent. These findings demonstrate that PLD plays a critical role in the ability of M1 PAMs to modulate certain central nervous system (CNS) functions and that biased M1 PAMs function differently in brain regions implicated in cognition.

    更新日期:2019-12-04
  • The long and short of antiviral activity
    Sci. Signal. (IF 6.481) Pub Date : 2019-12-03
    Erin R. Williams

    Only short isoforms of the pseudoenzyme PARP13 inhibit interferon responses.

    更新日期:2019-12-04
  • The interaction of ceramide 1-phosphate with group IVA cytosolic phospholipase A2 coordinates acute wound healing and repair
    Sci. Signal. (IF 6.481) Pub Date : 2019-12-03
    H. Patrick MacKnight, Daniel J. Stephenson, L. Alexis Hoeferlin, Savannah D. Benusa, James T. DeLigio, Kenneth D. Maus, Anika N. Ali, Jennifer S. Wayne, Margaret A. Park, Edward H. Hinchcliffe, Rhoderick E. Brown, John J. Ryan, Robert F. Diegelmann, Charles E. Chalfant

    The sphingolipid ceramide 1-phosphate (C1P) directly binds to and activates group IVA cytosolic phospholipase A2 (cPLA2α) to stimulate the production of eicosanoids. Because eicosanoids are important in wound healing, we examined the repair of skin wounds in knockout (KO) mice lacking cPLA2α and in knock-in (KI) mice in which endogenous cPLA2α was replaced with a mutant form having an ablated C1P interaction site. Wound closure rate was not affected in the KO or KI mice, but wound maturation was enhanced in the KI mice compared to that in wild-type controls. Wounds in KI mice displayed increased infiltration of dermal fibroblasts into the wound environment, increased wound tensile strength, and a higher ratio of type I:type III collagen. In vitro, primary dermal fibroblasts (pDFs) from KI mice showed substantially increased collagen deposition and migration velocity compared to pDFs from wild-type and KO mice. KI mice also showed an altered eicosanoid profile of reduced proinflammatory prostaglandins (PGE2 and TXB2) and an increased abundance of certain hydroxyeicosatetraenoic acid (HETE) species. Specifically, an increase in 5-HETE enhanced dermal fibroblast migration and collagen deposition. This gain-of-function role for the mutant cPLA2α was also linked to the relocalization of cPLA2α and 5-HETE biosynthetic enzymes to the cytoplasm and cytoplasmic vesicles. These findings demonstrate the regulation of key wound-healing mechanisms in vivo by a defined protein-lipid interaction and provide insights into the roles that cPLA2α and eicosanoids play in orchestrating wound repair.

    更新日期:2019-12-04
  • The human secretome
    Sci. Signal. (IF 6.481) Pub Date : 2019-11-26
    Mathias Uhlén, Max J. Karlsson, Andreas Hober, Anne-Sophie Svensson, Julia Scheffel, David Kotol, Wen Zhong, Abdellah Tebani, Linnéa Strandberg, Fredrik Edfors, Evelina Sjöstedt, Jan Mulder, Adil Mardinoglu, Anna Berling, Siri Ekblad, Melanie Dannemeyer, Sara Kanje, Johan Rockberg, Magnus Lundqvist, Magdalena Malm, Anna-Luisa Volk, Peter Nilsson, Anna Månberg, Tea Dodig-Crnkovic, Elisa Pin, Martin Zwahlen, Per Oksvold, Kalle von Feilitzen, Ragna S. Häussler, Mun-Gwan Hong, Cecilia Lindskog, Fredrik Ponten, Borbala Katona, Jimmy Vuu, Emil Lindström, Jens Nielsen, Jonathan Robinson, Burcu Ayoglu, Diana Mahdessian, Devin Sullivan, Peter Thul, Frida Danielsson, Charlotte Stadler, Emma Lundberg, Göran Bergström, Anders Gummesson, Bjørn G. Voldborg, Hanna Tegel, Sophia Hober, Björn Forsström, Jochen M. Schwenk, Linn Fagerberg, Åsa Sivertsson

    The proteins secreted by human cells (collectively referred to as the secretome) are important not only for the basic understanding of human biology but also for the identification of potential targets for future diagnostics and therapies. Here, we present a comprehensive analysis of proteins predicted to be secreted in human cells, which provides information about their final localization in the human body, including the proteins actively secreted to peripheral blood. The analysis suggests that a large number of the proteins of the secretome are not secreted out of the cell, but instead are retained intracellularly, whereas another large group of proteins were identified that are predicted to be retained locally at the tissue of expression and not secreted into the blood. Proteins detected in the human blood by mass spectrometry–based proteomics and antibody-based immunoassays are also presented with estimates of their concentrations in the blood. The results are presented in an updated version 19 of the Human Protein Atlas in which each gene encoding a secretome protein is annotated to provide an open-access knowledge resource of the human secretome, including body-wide expression data, spatial localization data down to the single-cell and subcellular levels, and data about the presence of proteins that are detectable in the blood.

    更新日期:2019-11-27
  • Trauma promotes resilience
    Sci. Signal. (IF 6.481) Pub Date : 2019-11-26
    Annalisa M. VanHook

    Wounding induces cytoprotective mechanisms that make cells more resistant to oxidative damage.

    更新日期:2019-11-27
  • Thiol-based direct threat sensing by the stress-activated protein kinase Hog1
    Sci. Signal. (IF 6.481) Pub Date : 2019-11-26
    Angel Guerra-Moreno, Miguel A. Prado, Jessie Ang, Helena M. Schnell, Yagmur Micoogullari, Joao A. Paulo, Daniel Finley, Steven P. Gygi, John Hanna

    The yeast stress-activated protein kinase Hog1 is best known for its role in mediating the response to osmotic stress, but it is also activated by various mechanistically distinct environmental stressors, including heat shock, endoplasmic reticulum stress, and arsenic. In the osmotic stress response, the signal is sensed upstream and relayed to Hog1 through a kinase cascade. Here, we identified a mode of Hog1 function whereby Hog1 senses arsenic through a direct physical interaction that requires three conserved cysteine residues located adjacent to the catalytic loop. These residues were essential for Hog1-mediated protection against arsenic, were dispensable for the response to osmotic stress, and promoted the nuclear localization of Hog1 upon exposure of cells to arsenic. Hog1 promoted arsenic detoxification by stimulating phosphorylation of the transcription factor Yap8, promoting Yap8 nuclear localization, and stimulating the transcription of the only known Yap8 targets, ARR2 and ARR3, both of which encode proteins that promote arsenic efflux. The related human kinases ERK1 and ERK2 also bound to arsenic in vitro, suggesting that this may be a conserved feature of some members of the mitogen-activated protein kinase (MAPK) family. These data provide a mechanistic basis for understanding how stress-activated kinases can sense distinct threats and perform highly specific adaptive responses.

    更新日期:2019-11-27
  • PKR-dependent cytosolic cGAS foci are necessary for intracellular DNA sensing
    Sci. Signal. (IF 6.481) Pub Date : 2019-11-26
    Siqi Hu, Hong Sun, Lijuan Yin, Jian Li, Shan Mei, Fengwen Xu, Chao Wu, Xiaoman Liu, Fei Zhao, Di Zhang, Yu Huang, Lili Ren, Shan Cen, Jianwei Wang, Chen Liang, Fei Guo

    Cyclic GMP-AMP synthase (cGAS) is a major sensor of cytosolic DNA from invading pathogens and damaged cellular organelles. Activation of cGAS promotes liquid-like phase separation and formation of membraneless cytoplasmic structures. Here, we found that cGAS bound G3BP1, a double-stranded nucleic acid helicase involved in the formation of stress granules. Loss of G3BP1 blocked subcellular cGAS condensation and suppressed the interferon response to intracellular DNA and DNA virus particles in cells. Furthermore, an RNA-dependent association with PKR promoted G3BP1 foci formation and cGAS-dependent interferon responses. Together, these results indicate that PKR promotes the formation of G3BP1-dependent, membraneless cytoplasmic structures necessary for the DNA-sensing function of cGAS in human cells. These data suggest that there is a previously unappreciated link between nucleic acid sensing pathways, which requires the formation of specialized subcellular structures.

    更新日期:2019-11-27
  • Metabolic adaption through regulated proteolysis
    Sci. Signal. (IF 6.481) Pub Date : 2019-11-19
    Wei Wong

    Induced mitochondrial protein turnover enables cells to metabolically adapt to oxygen and nutrient deprivation.

    更新日期:2019-11-20
  • Sequential activation of STIM1 links Ca2+ with luminal domain unfolding
    Sci. Signal. (IF 6.481) Pub Date : 2019-11-19
    Romana Schober, Daniel Bonhenry, Victoria Lunz, Jinhui Zhu, Adela Krizova, Irene Frischauf, Marc Fahrner, MengQi Zhang, Linda Waldherr, Tony Schmidt, Isabella Derler, Peter B. Stathopulos, Christoph Romanin, Rüdiger H. Ettrich, Rainer Schindl

    The stromal interaction molecule 1 (STIM1) has two important functions, Ca2+ sensing within the endoplasmic reticulum and activation of the store-operated Ca2+ channel Orai1, enabling plasma-membrane Ca2+ influx. We combined molecular dynamics (MD) simulations with live-cell recordings and determined the sequential Ca2+-dependent conformations of the luminal STIM1 domain upon activation. Furthermore, we identified the residues within the canonical and noncanonical EF-hand domains that can bind to multiple Ca2+ ions. In MD simulations, a single Ca2+ ion was sufficient to stabilize the luminal STIM1 complex. Ca2+ store depletion destabilized the two EF hands, triggering disassembly of the hydrophobic cleft that they form together with the stable SAM domain. Point mutations associated with tubular aggregate myopathy or cancer that targeted the canonical EF hand, and the hydrophobic cleft yielded constitutively clustered STIM1, which was associated with activation of Ca2+ entry through Orai1 channels. On the basis of our results, we present a model of STIM1 Ca2+ binding and refine the currently known initial steps of STIM1 activation on a molecular level.

    更新日期:2019-11-20
  • Dynamic palmitoylation controls the microdomain localization of the DKK1 receptors CKAP4 and LRP6
    Sci. Signal. (IF 6.481) Pub Date : 2019-11-19
    Ryota Sada, Hirokazu Kimura, Yuko Fukata, Masaki Fukata, Hideki Yamamoto, Akira Kikuchi

    Dickkopf1 (DKK1) was originally identified as an antagonist of Wnt signaling that binds to and induces the clathrin-mediated endocytosis of the Wnt coreceptors low-density lipoprotein receptor–related proteins 5 and 6 (LRP5/6). DKK1 also binds to cytoskeleton-associated protein 4 (CKAP4), which was originally identified as an endoplasmic reticulum (ER) protein but also functions at the plasma membrane as a receptor for various ligands. The DKK1-CKAP4 pathway is activated in several human cancers and promotes cell proliferation by activating signaling through the kinases PI3K and AKT. We found that both CKAP4 and LRP6 primarily localized to detergent-resistant membrane (DRM) fractions of the plasma membrane in a palmitoylation-dependent manner and that palmitoylation of CKAP4 was required for it to promote cell proliferation. DKK1 induced the depalmitoylation of both CKAP4 and LRP6 by acylprotein thioesterases (APTs), resulting in their translocation to the non-DRM fractions. Moreover, DKK1-dependent depalmitoylation of both receptors required activation of the PI3K-AKT pathway. DKK1 simultaneously bound CKAP4 and LRP6, resulting in the formation of a ternary complex. LRP5/6 knockdown decreased DKK1-dependent AKT activation and cancer cell proliferation through CKAP4, whereas CKAP4 knockdown did not affect DKK1-dependent inhibition of Wnt signaling through LRP5/6. These results indicate that the palmitoylation states of CKAP4 and LRP6 play important roles in their signaling and that LRP5/6 enhance DKK1-CKAP4 signaling.

    更新日期:2019-11-20
  • Taking care of the orphans
    Sci. Signal. (IF 6.481) Pub Date : 2019-11-12
    John F. Foley

    Comparative genomics, bioinformatics, and biochemical assays enable the pairing of endogenous peptides with orphan GPCRs.

    更新日期:2019-11-13
  • Translocation of TRPV4-PI3Kγ complexes to the plasma membrane drives myofibroblast transdifferentiation
    Sci. Signal. (IF 6.481) Pub Date : 2019-11-12
    Lisa M. Grove, Maradumane L. Mohan, Susamma Abraham, Rachel G. Scheraga, Brian D. Southern, James F. Crish, Sathyamangla V. Naga Prasad, Mitchell A. Olman

    Myofibroblasts are key contributors to pathological fibrotic conditions of several major organs. The transdifferentiation of fibroblasts into myofibroblasts requires both a mechanical signal and transforming growth factor–β (TGF-β) signaling. The cation channel transient receptor potential vanilloid 4 (TRPV4) is a critical mediator of myofibroblast transdifferentiation and in vivo fibrosis through its mechanosensitivity to extracellular matrix stiffness. Here, we showed that TRPV4 promoted the transdifferentiation of human and mouse lung fibroblasts through its interaction with phosphoinositide 3-kinase γ (PI3Kγ), forming nanomolar-affinity, intracellular TRPV4-PI3Kγ complexes. TGF-β induced the recruitment of TRPV4-PI3Kγ complexes to the plasma membrane and increased the activities of both TRPV4 and PI3Kγ. Using gain- and loss-of-function approaches, we showed that both TRPV4 and PI3Kγ were required for myofibroblast transdifferentiation as assessed by the increased production of α-smooth muscle actin and its incorporation into stress fibers, cytoskeletal changes, collagen-1 production, and contractile force. Expression of various mutant forms of the PI3Kγ catalytic subunit (p110γ) in cells lacking PI3Kγ revealed that only the noncatalytic, amino-terminal domain of p110γ was necessary and sufficient for TGF-β–induced TRPV4 plasma membrane recruitment and myofibroblast transdifferentiation. These data suggest that TGF-β stimulates a noncanonical scaffolding action of PI3Kγ, which recruits TRPV4-PI3Kγ complexes to the plasma membrane, thereby increasing myofibroblast transdifferentiation. Given that both TRPV4 and PI3Kγ have pleiotropic actions, targeting the interaction between them could provide a specific therapeutic approach for inhibiting myofibroblast transdifferentiation.

    更新日期:2019-11-13
  • The ALK-1/SMAD/ATOH8 axis attenuates hypoxic responses and protects against the development of pulmonary arterial hypertension
    Sci. Signal. (IF 6.481) Pub Date : 2019-11-12
    Masato Morikawa, Yoshihide Mitani, Katarina Holmborn, Taichi Kato, Daizo Koinuma, Junko Maruyama, Eleftheria Vasilaki, Hirofumi Sawada, Mai Kobayashi, Takayuki Ozawa, Yasuyuki Morishita, Yasumasa Bessho, Shingo Maeda, Johan Ledin, Hiroyuki Aburatani, Ryoichiro Kageyama, Kazuo Maruyama, Carl-Henrik Heldin, Kohei Miyazono

    Dysregulated bone morphogenetic protein (BMP) signaling in endothelial cells (ECs) is implicated in vascular diseases such as pulmonary arterial hypertension (PAH). Here, we showed that the transcription factor ATOH8 was a direct target of SMAD1/5 and was induced in a manner dependent on BMP but independent of Notch, another critical signaling pathway in ECs. In zebrafish and mice, inactivation of Atoh8 did not cause an arteriovenous malformation–like phenotype, which may arise because of dysregulated Notch signaling. In contrast, Atoh8-deficient mice exhibited a phenotype mimicking PAH, which included increased pulmonary arterial pressure and right ventricular hypertrophy. Moreover, ATOH8 expression was decreased in PAH patient lungs. We showed that in cells, ATOH8 interacted with hypoxia-inducible factor 2α (HIF-2α) and decreased its abundance, leading to reduced induction of HIF-2α target genes in response to hypoxia. Together, these findings suggest that the BMP receptor type II/ALK-1/SMAD/ATOH8 axis may attenuate hypoxic responses in ECs in the pulmonary circulation and may help prevent the development of PAH.

    更新日期:2019-11-13
  • Amino acid starvation enhances vaccine efficacy by augmenting neutralizing antibody production
    Sci. Signal. (IF 6.481) Pub Date : 2019-11-12
    Sumbul Afroz, Shama, Srikanth Battu, Shaikh Matin, Sabrina Solouki, Jessica P. Elmore, Gillipsie Minhas, Weishan Huang, Avery August, Nooruddin Khan

    Specific reduction in the intake of proteins or amino acids (AAs) offers enormous health benefits, including increased life span, protection against age-associated disorders, and improved metabolic fitness and immunity. Cells respond to conditions of AA starvation by activating the amino acid starvation response (AAR). Here, we showed that mimicking AAR with halofuginone (HF) enhanced the magnitude and affinity of neutralizing, antigen-specific antibody responses in mice immunized with dengue virus envelope domain III protein (DENVrEDIII), a potent vaccine candidate against DENV. HF enhanced the formation of germinal centers (GCs) and increased the production of the cytokine IL-10 in the secondary lymphoid organs of vaccinated mice. Furthermore, HF promoted the transcription of genes associated with memory B cell formation and maintenance and maturation of GCs in the draining lymph nodes of vaccinated mice. The increased abundance of IL-10 in HF-preconditioned mice correlated with enhanced GC responses and may promote the establishment of long-lived plasma cells that secrete antigen-specific, high-affinity antibodies. Thus, these data suggest that mimetics of AA starvation could provide an alternative strategy to augment the efficacy of vaccines against dengue and other infectious diseases.

    更新日期:2019-11-13
  • Lactylation drives resolution
    Sci. Signal. (IF 6.481) Pub Date : 2019-11-05
    Erin R. Williams

    Histone modifications derived from the metabolite lactate promote transcription of genes necessary for the resolution of inflammation.

    更新日期:2019-11-06
  • TFEB drives PGC-1α expression in adipocytes to protect against diet-induced metabolic dysfunction
    Sci. Signal. (IF 6.481) Pub Date : 2019-11-05
    Trent D. Evans, Xiangyu Zhang, Se-Jin Jeong, Anyuan He, Eric Song, Somashubhra Bhattacharya, Karyn B. Holloway, Irfan J. Lodhi, Babak Razani

    TFEB is a basic helix-loop-helix transcription factor that confers protection against metabolic diseases such as atherosclerosis by targeting a network of genes involved in autophagy-lysosomal biogenesis and lipid catabolism. In this study, we sought to characterize the role of TFEB in adipocyte and adipose tissue physiology and evaluate the therapeutic potential of adipocyte-specific TFEB overexpression in obesity. We demonstrated that mice with adipocyte-specific TFEB overexpression (Adipo-TFEB) were protected from diet-induced obesity, insulin resistance, and metabolic sequelae. Adipo-TFEB mice were lean primarily through increased metabolic rate, suggesting a role for adipose tissue browning and enhanced nonshivering thermogenesis in fat. Transcriptional characterization revealed that TFEB targeted genes involved in adipose tissue browning rather than those involved in autophagy. One such gene encoded PGC-1α, an established target of TFEB that promotes adipocyte browning. To dissect the role of PGC-1α in mediating the downstream effects of TFEB overexpression, we generated mice with adipocyte-specific PGC-1α deficiency and TFEB overexpression. Without PGC-1α, the ability of TFEB overexpression to brown adipose tissue and to elicit beneficial metabolic effects was blunted. Overall, these data implicate TFEB as a PGC-1α–dependent regulator of adipocyte browning and suggest its therapeutic potential in treating metabolic disease.

    更新日期:2019-11-06
  • Extension of the Notch intracellular domain ankyrin repeat stack by NRARP promotes feedback inhibition of Notch signaling
    Sci. Signal. (IF 6.481) Pub Date : 2019-11-05
    Sanchez M. Jarrett, Tom C. M. Seegar, Mark Andrews, Guillaume Adelmant, Jarrod A. Marto, Jon C. Aster, Stephen C. Blacklow

    Canonical Notch signaling relies on regulated proteolysis of the receptor Notch to generate a nuclear effector that induces the transcription of Notch-responsive genes. In higher organisms, one Notch-responsive gene that is activated in many different cell types encodes the Notch-regulated ankyrin repeat protein (NRARP), which acts as a negative feedback regulator of Notch responses. Here, we showed that NRARP inhibited the growth of Notch-dependent T cell acute lymphoblastic leukemia (T-ALL) cell lines and bound directly to the core Notch transcriptional activation complex (NTC), requiring both the transcription factor RBPJ and the Notch intracellular domain (NICD), but not Mastermind-like proteins or DNA. The crystal structure of an NRARP-NICD1-RBPJ-DNA complex, determined to 3.75 Å resolution, revealed that the assembly of NRARP-NICD1-RBPJ complexes relied on simultaneous engagement of RBPJ and NICD1, with the three ankyrin repeats of NRARP extending the Notch1 ankyrin repeat stack. Mutations at the NRARP-NICD1 interface disrupted entry of the proteins into NTCs and abrogated feedback inhibition in Notch signaling assays in cultured cells. Forced expression of NRARP reduced the abundance of NICD in cells, suggesting that NRARP may promote the degradation of NICD. These studies establish the structural basis for NTC engagement by NRARP and provide insights into a critical negative feedback mechanism that regulates Notch signaling.

    更新日期:2019-11-06
  • Nucleotide exchange–dependent and nucleotide exchange–independent functions of plant heterotrimeric GTP-binding proteins
    Sci. Signal. (IF 6.481) Pub Date : 2019-11-05
    Natsumi Maruta, Yuri Trusov, David Chakravorty, Daisuke Urano, Sarah M. Assmann, Jose R. Botella

    Heterotrimeric guanine nucleotide–binding proteins (G proteins), which are composed of α, β, and γ subunits, are versatile, guanine nucleotide–dependent, molecular on-off switches. In animals and fungi, the exchange of GDP for GTP on Gα controls G protein activation and is crucial for normal cellular responses to diverse extracellular signals. The model plant Arabidopsis thaliana has a single canonical Gα subunit, AtGPA1. We found that, in planta, the constitutively active, GTP-bound AtGPA1(Q222L) mutant and the nucleotide-free AtGPA1(S52C) mutant interacted with Gβγ1 and Gβγ2 dimers with similar affinities, suggesting that G protein heterotrimer formation occurred independently of nucleotide exchange. In contrast, AtGPA1(Q222L) had a greater affinity than that of AtGPA1(S52C) for Gβγ3, suggesting that the GTP-bound conformation of AtGPA1(Q222L) is distinct and tightly associated with Gβγ3. Functional analysis of transgenic lines expressing either AtGPA1(S52C) or AtGPA1(Q222L) in the gpa1-null mutant background revealed various mutant phenotypes that were complemented by either AtGPA1(S52C) or AtGPA1(Q222L). We conclude that, in addition to the canonical GDP-GTP exchange–dependent mechanism, plant G proteins can function independently of nucleotide exchange.

    更新日期:2019-11-06
  • The structure of the TLR5-flagellin complex: a new mode of pathogen detection, conserved receptor dimerization for signaling.
    Sci. Signal. (IF 6.481) Pub Date : 2012-06-23
    Jinghua Lu,Peter D Sun

    Knowledge about how Toll-like receptors (TLRs) recognize pathogenic ligands is critical to understanding how these receptors are activated and to designing therapeutic compounds that target this family of receptors for inflammatory diseases. The crystal structure of TLR5 in complex with its bacterial ligand flagellin revealed that the ligand-binding mode for TLR5 is distinct from that of previously characterized TLRs. Nevertheless, like other TLRs, TLR5 forms a dimer in response to ligand binding. This work contributes to our current knowledge of TLR function and further demonstrates the ability of TLRs to couple versatile ligand recognition to a conserved receptor signaling mechanism.

    更新日期:2019-11-01
  • Inferring signaling pathway topologies from multiple perturbation measurements of specific biochemical species.
    Sci. Signal. (IF 6.481) Pub Date : 2010-08-25
    Tian-Rui Xu,Vladislav Vyshemirsky,Amélie Gormand,Alex von Kriegsheim,Mark Girolami,George S Baillie,Dominic Ketley,Allan J Dunlop,Graeme Milligan,Miles D Houslay,Walter Kolch

    The specification of biological decisions by signaling pathways is encoded by the interplay between activation dynamics and network topologies. Although we can describe complex networks, we cannot easily determine which topology the cell actually uses to transduce a specific signal. Experimental testing of all plausible topologies is infeasible because of the combinatorially large number of experiments required to explore the complete hypothesis space. Here, we demonstrate that Bayesian inference-based modeling provides an approach to explore and constrain this hypothesis space,permitting the rational ranking of pathway models. Our approach can use measurements of a limited number of biochemical species when combined with multiple perturbations. As proof of concept, we examined the activation of the extracellular signal-regulated kinase (ERK) pathway by epidermal growth factor. The predicted and experimentally validated model shows that both Raf-1 and, unexpectedly,B-Raf are needed to fully activate ERK in two different cell lines. Thus, our formal methodology rationally infers evidentially supported pathway topologies even when a limited number of biochemical and kinetic measurements are available.

    更新日期:2019-11-01
  • Intracellular signaling and the origins of the sensations of itch and pain.
    Sci. Signal. (IF 6.481) Pub Date : 2011-10-07
    Sang-Kyou Han,Melvin I Simon

    The skin is the largest sensory organ of the body. It is innervated by a diverse array of primary sensory neurons, including a heterogeneous subset of unmyelinated afferents called C fibers. C fibers, sometimes classified as nociceptors, can detect various painful stimuli, including temperature extremes. However, it is increasingly evident that these afferents respond to various pruritic stimuli and transmit information to the brain that is perceived as itch; this can subsequently drive scratching behavior. Although itch and pain are distinct sensations, they are closely related and can, under certain circumstances, antagonize each other. However, it is not clear precisely when, where, and how the processes generating these two sensations originate and how they are dissociated. Clues have come from the analysis of the activities of specific ligands and their receptors. New data indicate that specific pruritic ligands carrying both itch and pain information are selectively recognized by different G protein–coupled receptors (GPCRs), and this information may be transduced through different intracellular circuits in the same neuron. These findings raise questions about the intracellular mechanisms that preprocess and perhaps encode GPCR-mediated signals.

    更新日期:2019-11-01
  • iRhom2 and TNF: Partners or enemies?
    Sci. Signal. (IF 6.481) Pub Date : 2019-10-29
    Marina Badenes, Colin Adrain

    iRhom2 is an essential cofactor for ADAM17, the metalloprotease that sheds both the proinflammatory cytokine tumor necrosis factor–α (TNF-α) and TNF receptors (TNFRs) from the cell surface. In this issue of Science Signaling, Sundaram et al. demonstrate a protective role for iRhom2 in promoting ADAM17-mediated shedding of TNFRs in hepatic stellate cells, which reduces TNFR signaling and liver fibrosis in response to injury.

    更新日期:2019-10-29
  • iRhom2 inhibits bile duct obstruction–induced liver fibrosis
    Sci. Signal. (IF 6.481) Pub Date : 2019-10-29
    Balamurugan Sundaram, Kristina Behnke, Andrea Belancic, Mazin A. Al-Salihi, Yasser Thabet, Robin Polz, Rossella Pellegrino, Yuan Zhuang, Prashant V. Shinde, Haifeng C. Xu, Jelena Vasilevska, Thomas Longerich, Diran Herebian, Ertan Mayatepek, Hans H. Bock, Petra May, Claus Kordes, Nima Aghaeepour, Tak W. Mak, Verena Keitel, Dieter Häussinger, Jürgen Scheller, Aleksandra A. Pandyra, Karl S. Lang, Philipp A. Lang

    Chronic liver disease can induce prolonged activation of hepatic stellate cells, which may result in liver fibrosis. Inactive rhomboid protein 2 (iRhom2) is required for the maturation of A disintegrin and metalloprotease 17 (ADAM17, also called TACE), which is responsible for the cleavage of membrane-bound tumor necrosis factor–α (TNF-α) and its receptors (TNFRs). Here, using the murine bile duct ligation (BDL) model, we showed that the abundance of iRhom2 and activation of ADAM17 increased during liver fibrosis. Consistent with this, concentrations of ADAM17 substrates were increased in plasma samples from mice after BDL and in patients suffering from liver cirrhosis. We observed increased liver fibrosis, accelerated disease progression, and an increase in activated stellate cells after BDL in mice lacking iRhom2 (Rhbdf2−/−) compared to that in controls. In vitro primary mouse hepatic stellate cells exhibited iRhom2-dependent shedding of the ADAM17 substrates TNFR1 and TNFR2. In vivo TNFR shedding after BDL also depended on iRhom2. Treatment of Rhbdf2−/− mice with the TNF-α inhibitor etanercept reduced the presence of activated stellate cells and alleviated liver fibrosis after BDL. Together, these data suggest that iRhom2-mediated inhibition of TNFR signaling protects against liver fibrosis.

    更新日期:2019-10-29
  • TLR7 and TLR8 activate distinct pathways in monocytes during RNA virus infection
    Sci. Signal. (IF 6.481) Pub Date : 2019-10-29
    Marine de Marcken, Khushwant Dhaliwal, Ann Caroline Danielsen, Anne Sophie Gautron, Margarita Dominguez-Villar

    Human blood CD14+ monocytes are bone marrow–derived white blood cells that sense and respond to pathogens. Although innate immune activation by RNA viruses preferentially occurs through intracellular RIG-I–like receptors, other nucleic acid recognition receptors, such as Toll-like receptors (TLRs), play a role in finely programming the final outcome of virus infection. Here, we dissected how human monocytes respond to infection with either Coxsackie (CV), encephalomyocarditis (EMCV), influenza A (IAV), measles (MV), Sendai (SV), or vesicular stomatitis (VSV) virus. We found that in monocytes, type I interferon (IFN) and cytokine responses to infection were RNA virus specific and differentially involved TLR7 and TLR8, which sense single-stranded RNA. These TLRs activated distinct signaling cascades in monocytes, which correlated with differences in the production of cytokines involved in the polarization of CD4+ T helper cells. Furthermore, we found that TLR7 signaling specifically increased expression of the transcription factor FOSL1, which reduced IL-27 and TNFα production by monocytes. TLR7, but not TLR8, activation of monocytes also stimulated Ca2+ flux that prevented type I IFN responses. Our work demonstrates that in human monocytes, TLR7 and TLR8 triggered different signaling pathways that contribute to distinct phenotypes during RNA virus infection. In addition, we defined individual targets within these pathways that promoted specific T helper and antiviral responses.

    更新日期:2019-10-29
  • Inflammation induces stem cell quiescence
    Sci. Signal. (IF 6.481) Pub Date : 2019-10-29
    Annalisa M. VanHook

    Chronic inflammation causes olfactory stem cells to become quiescent and secrete immunomodulatory cytokines.

    更新日期:2019-10-29
  • An engineered pathway for N-hydroxy-pipecolic acid synthesis enhances systemic acquired resistance in tomato
    Sci. Signal. (IF 6.481) Pub Date : 2019-10-22
    Eric C. Holmes, Yun-Chu Chen, Elizabeth S. Sattely, Mary Beth Mudgett

    Systemic acquired resistance (SAR) is a powerful immune response that triggers broad-spectrum disease resistance throughout a plant. In the model plant Arabidopsis thaliana, long-distance signaling and SAR activation in uninfected tissues occur without circulating immune cells and instead rely on the metabolite N-hydroxy-pipecolic acid (NHP). Engineering SAR in crop plants would enable external control of a plant’s ability to mount a global defense response upon sudden changes in the environment. Such a metabolite-engineering approach would require the molecular machinery for producing and responding to NHP in the crop plant. Here, we used heterologous expression in Nicotiana benthamiana leaves to identify a minimal set of Arabidopsis genes necessary for the biosynthesis of NHP. Local expression of these genes in tomato leaves triggered SAR in distal tissues in the absence of a pathogen, suggesting that the SAR trait can be engineered to enhance a plant’s endogenous ability to respond to pathogens. We also showed tomato produces endogenous NHP in response to a bacterial pathogen and that NHP is present across the plant kingdom, raising the possibility that an engineering strategy to enhance NHP-induced defenses could be possible in many crop plants.

    更新日期:2019-10-23
  • Induction of metabolic quiescence defines the transitional to follicular B cell switch
    Sci. Signal. (IF 6.481) Pub Date : 2019-10-22
    Jocelyn R. Farmer, Hugues Allard-Chamard, Na Sun, Maimuna Ahmad, Alice Bertocchi, Vinay S. Mahajan, Toby Aicher, Johan Arnold, Mark D. Benson, Jordan Morningstar, Sara Barmettler, Grace Yuen, Samuel J. H. Murphy, Jolan E. Walter, Musie Ghebremichael, Alex K. Shalek, Facundo Batista, Robert Gerszten, Shiv Pillai

    Transitional B cells must actively undergo selection for self-tolerance before maturing into their resting follicular B cell successors. We found that metabolic quiescence was acquired at the follicular B cell stage in both humans and mice. In follicular B cells, the expression of genes involved in ribosome biogenesis, aerobic respiration, and mammalian target of rapamycin complex 1 (mTORC1) signaling was reduced when compared to that in transitional B cells. Functional metabolism studies, profiling of whole-cell metabolites, and analysis of cell surface proteins in human B cells suggested that this transition was also associated with increased extracellular adenosine salvage. Follicular B cells increased the abundance of the cell surface ectonucleotidase CD73, which coincided with adenosine 5′-monophosphate–activated protein kinase (AMPK) activation. Differentiation to the follicular B cell stage in vitro correlated with surface acquisition of CD73 on human transitional B cells and was augmented with the AMPK agonist, AICAR. Last, individuals with gain-of-function PIK3CD (PI3Kδ) mutations and increased pS6 activation exhibited a near absence of circulating follicular B cells. Together, our data suggest that mTORC1 attenuation may be necessary for human follicular B cell development. These data identify a distinct metabolic switch during human B cell development at the transitional to follicular stages, which is characterized by an induction of extracellular adenosine salvage, AMPK activation, and the acquisition of metabolic quiescence.

    更新日期:2019-10-23
  • CD45 functions as a signaling gatekeeper in T cells
    Sci. Signal. (IF 6.481) Pub Date : 2019-10-22
    Adam H. Courtney, Alexey A. Shvets, Wen Lu, Gloria Griffante, Marianne Mollenauer, Veronika Horkova, Wan-Lin Lo, Steven Yu, Ondrej Stepanek, Arup K. Chakraborty, Arthur Weiss

    T cells require the protein tyrosine phosphatase CD45 to detect and respond to antigen because it activates the Src family kinase Lck, which phosphorylates the T cell antigen receptor (TCR) complex. CD45 activates Lck by opposing the negative regulatory kinase Csk. Paradoxically, CD45 has also been implicated in suppressing TCR signaling by dephosphorylating the same signaling motifs within the TCR complex upon which Lck acts. We sought to reconcile these observations using chemical and genetic perturbations of the Csk/CD45 regulatory axis incorporated with computational analyses. Specifically, we titrated the activities of Csk and CD45 and assessed their influence on Lck activation, TCR-associated ζ-chain phosphorylation, and more downstream signaling events. Acute inhibition of Csk revealed that CD45 suppressed ζ-chain phosphorylation and was necessary for a regulatable pool of active Lck, thereby interconnecting the activating and suppressive roles of CD45 that tune antigen discrimination. CD45 suppressed signaling events that were antigen independent or induced by low-affinity antigen but not those initiated by high-affinity antigen. Together, our findings reveal that CD45 acts as a signaling “gatekeeper,” enabling graded signaling outputs while filtering weak or spurious signaling events.

    更新日期:2019-10-23
  • A smoky path to diabetes
    Sci. Signal. (IF 6.481) Pub Date : 2019-10-22
    Wei Wong

    A nicotine-activated brain-pancreas circuit could explain why smokers are more likely to develop type 2 diabetes.

    更新日期:2019-10-23
  • Impaired regulation of KCC2 phosphorylation leads to neuronal network dysfunction and neurodevelopmental pathology
    Sci. Signal. (IF 6.481) Pub Date : 2019-10-15
    Lucie I. Pisella, Jean-Luc Gaiarsa, Diabé Diabira, Jinwei Zhang, Ilgam Khalilov, JingJing Duan, Kristopher T. Kahle, Igor Medina

    KCC2 is a vital neuronal K+/Cl− cotransporter that is implicated in the etiology of numerous neurological diseases. In normal cells, KCC2 undergoes developmental dephosphorylation at Thr906 and Thr1007. We engineered mice with heterozygous phosphomimetic mutations T906E and T1007E (KCC2E/+) to prevent the normal developmental dephosphorylation of these sites. Immature (postnatal day 15) but not juvenile (postnatal day 30) KCC2E/+ mice exhibited altered GABAergic inhibition, an increased glutamate/GABA synaptic ratio, and greater susceptibility to seizure. KCC2E/+ mice also had abnormal ultrasonic vocalizations at postnatal days 10 to 12 and impaired social behavior at postnatal day 60. Postnatal bumetanide treatment restored network activity by postnatal day 15 but failed to restore social behavior by postnatal day 60. Our data indicate that posttranslational KCC2 regulation controls the GABAergic developmental sequence in vivo, indicating that deregulation of KCC2 could be a risk factor for the emergence of neurological pathology.

    更新日期:2019-10-16
  • The new cartography
    Sci. Signal. (IF 6.481) Pub Date : 2019-10-15
    Erin R. Williams

    Quantitative proteomics maps previously unappreciated interactions stimulated by T cell activation.

    更新日期:2019-10-16
  • Tuning the regulator: Phosphorylation of KCC2 at two specific sites is critical for neurodevelopment
    Sci. Signal. (IF 6.481) Pub Date : 2019-10-15
    Gerald W. Zamponi

    The K+/Cl− cotransporter KCC2 is a molecular switch between excitatory and inhibitory effects of GABAergic inputs into neurons. In a pair of exciting studies, Watanabe et al. and Pisella et al. elucidate the role of KCC2 dephosphorylation in this process and reveal its consequences for neurodevelopment and nervous system pathology.

    更新日期:2019-10-16
  • Developmentally regulated KCC2 phosphorylation is essential for dynamic GABA-mediated inhibition and survival
    Sci. Signal. (IF 6.481) Pub Date : 2019-10-15
    Miho Watanabe, Jinwei Zhang, M. Shahid Mansuri, Jingjing Duan, Jason K. Karimy, Eric Delpire, Seth L. Alper, Richard P. Lifton, Atsuo Fukuda, Kristopher T. Kahle

    Despite its importance for γ-aminobutyric acid (GABA) inhibition and involvement in neurodevelopmental disease, the regulatory mechanisms of the K+/Cl− cotransporter KCC2 (encoded by SLC12A5) during maturation of the central nervous system (CNS) are not entirely understood. Here, we applied quantitative phosphoproteomics to systematically map sites of KCC2 phosphorylation during CNS development in the mouse. KCC2 phosphorylation at Thr906 and Thr1007, which inhibits KCC2 activity, underwent dephosphorylation in parallel with the GABA excitatory-inhibitory sequence in vivo. Knockin mice expressing the homozygous phosphomimetic KCC2 mutations T906E/T1007E (Kcc2E/E), which prevented the normal developmentally regulated dephosphorylation of these sites, exhibited early postnatal death from respiratory arrest and a marked absence of cervical spinal neuron respiratory discharges. Kcc2E/E mice also displayed disrupted lumbar spinal neuron locomotor rhythmogenesis and touch-evoked status epilepticus associated with markedly impaired KCC2-dependent Cl− extrusion. These data identify a previously unknown phosphorylation-dependent KCC2 regulatory mechanism during CNS development that is essential for dynamic GABA-mediated inhibition and survival.

    更新日期:2019-10-16
  • The Ca2+ export pump PMCA clears near-membrane Ca2+ to facilitate store-operated Ca2+ entry and NFAT activation
    Sci. Signal. (IF 6.481) Pub Date : 2019-10-08
    Christina K. Go, Robert Hooper, Matthew R. Aronson, Bryant Schultz, Taha Cangoz, Neeharika Nemani, Yi Zhang, Muniswamy Madesh, Jonathan Soboloff

    Ca2+ signals, which facilitate pluripotent changes in cell fate, reflect the balance between cation entry and export. We found that overexpression of either isoform of the Ca2+-extruding plasma membrane calcium ATPase 4 (PMCA4) pump in Jurkat T cells unexpectedly increased activation of the Ca2+-dependent transcription factor nuclear factor of activated T cells (NFAT). Coexpression of the endoplasmic reticulum–resident Ca2+ sensor stromal interaction molecule 1 (STIM1) with the PMCA4b splice variant further enhanced NFAT activity; however, coexpression with PMCA4a depressed NFAT. No PMCA4 splice variant dependence in STIM1 association was observed, whereas partner of STIM1 (POST) preferentially associated with PMCA4b over PMCA4a, which enhanced, rather than inhibited, PMCA4 function. A comparison of global and near-membrane cytosolic Ca2+ abundances during store-operated Ca2+ entry revealed that PMCA4 markedly depressed near-membrane Ca2+ concentrations, particularly when PMCA4b was coexpressed with STIM1. PMCA4b closely associated with both POST and the store-operated Ca2+ channel Orai1. Furthermore, POST knockdown increased the near-membrane Ca2+ concentration, inhibiting the global cytosolic Ca2+ increase. These observations reveal an unexpected role for POST in coupling PMCA4 to Orai1 to promote Ca2+ entry during T cell activation through Ca2+ disinhibition.

    更新日期:2019-10-10
  • CARD9 mediates dendritic cell–induced development of Lyn deficiency–associated autoimmune and inflammatory diseases
    Sci. Signal. (IF 6.481) Pub Date : 2019-10-08
    Jun Ma, Clare L. Abram, Yongmei Hu, Clifford A. Lowell

    CARD9 is an immune adaptor protein in myeloid cells that is involved in C-type lectin signaling and antifungal immunity. CARD9 is implicated in autoimmune and inflammatory-related diseases, such as rheumatoid arthritis, IgA nephropathy, ankylosing spondylitis, and inflammatory bowel disease (IBD). Given that Lyn-deficient (Lyn−/−) mice are susceptible to both autoimmunity and IBD, we investigated the immunological role of CARD9 in the development of these diseases using the Lyn−/− mouse model. We found that genetic deletion of CARD9 was sufficient to reduce the development of both spontaneous autoimmune disease as well as DSS- or IL-10 deficiency–associated colitis in Lyn−/− mice. Mechanistically, CARD9 was a vital component of the Lyn-mediated regulation of Toll-like receptor (TLR2 and TLR4) signaling in dendritic cells, but not in macrophages. In the absence of Lyn, signaling through a CD11b-Syk-PKCδ-CARD9 pathway was amplified, leading to increased TLR-induced production of inflammatory cytokines. Dendritic cell–specific deletion of CARD9 reversed the development of autoimmune and experimental colitis observed in dendritic cell–specific, Lyn-deficient mice. These findings suggest that targeting CARD9 may suppress the development of colitis and autoimmunity by reducing dendritic cell–driven inflammation.

    更新日期:2019-10-10
  • T cell–derived soluble glycoprotein GPIbα mediates PGE2 production in human monocytes activated with the vaccine adjuvant MDP
    Sci. Signal. (IF 6.481) Pub Date : 2019-10-08
    Fengjie Liu, Yukinori Endo, Tatiana Romantseva, Wells W. Wu, Adovi Akue, Rong-Fong Shen, Hana Golding, Marina Zaitseva

    Vaccine adjuvants containing analogs of microbial products activate pattern recognition receptors (PRRs) on antigen-presenting cells, including monocytes and macrophages, which can cause prostaglandin E2 (PGE2) release and consequently undesired inflammatory responses and fever in vaccine recipients. Here, we studied the mechanism of PGE2 production by human monocytes activated with muramyl dipeptide (MDP) adjuvant, which activates cytosolic nucleotide-binding oligomerization domain 2 (NOD2). In rabbits, administration of MDP elicited an early increase in PGE2 followed by fever. In human monocytes, MDP alone did not induce PGE2 production. However, high amounts of PGE2 and the proinflammatory cytokines IL-1β and IL-6 were secreted by monocytes activated with MDP in the presence of conditioned medium obtained from CD3 bead–isolated T cells (Tc CM) but not from those isolated without CD3 beads. Mass spectrometry and immunoblotting revealed that the costimulatory factor in Tc CM was glycoprotein Ib α (GPIbα). Antibody-mediated blockade of GPIbα or of its receptor, Mac-1 integrin, inhibited the secretion of PGE2, IL-1β, and IL-6 in MDP + Tc CM–activated monocytes, whereas recombinant GPIbα protein increased PGE2 production by MDP-treated monocytes. In vivo, COX2 mRNA abundance was reduced in the liver and spleen of Mac-1 KO mice after administration of MDP compared with that of treated wild-type mice. Our findings suggest that the production of PGE2 and proinflammatory cytokines by MDP-activated monocytes is mediated by cooperation between two signaling pathways: one delivered by MDP through NOD2 and a second through activation of Mac-1 by T cell–derived GPIbα.

    更新日期:2019-10-10
  • PAF and the inflammasome
    Sci. Signal. (IF 6.481) Pub Date : 2019-10-08
    John F. Foley

    The phospholipid PAF stimulates NLRP3 inflammasome activation and inflammatory cytokine production independently of its GPCR.

    更新日期:2019-10-10
  • HIF-independent synthetic lethality between CDK4/6 inhibition and VHL loss across species
    Sci. Signal. (IF 6.481) Pub Date : 2019-10-01
    Hilary E. Nicholson, Zeshan Tariq, Benjamin E. Housden, Rebecca B. Jennings, Laura A. Stransky, Norbert Perrimon, Sabina Signoretti, William G. Kaelin

    Inactivation of the VHL tumor suppressor gene is the signature initiating event in clear cell renal cell carcinoma (ccRCC), the most common form of kidney cancer, and causes the accumulation of hypoxia-inducible factor 2α (HIF-2α). HIF-2α inhibitors are effective in some ccRCC cases, but both de novo and acquired resistance have been observed in the laboratory and in the clinic. Here, we identified synthetic lethality between decreased activity of cyclin-dependent kinases 4 and 6 (CDK4/6) and VHL inactivation in two species (human and Drosophila) and across diverse human ccRCC cell lines in culture and xenografts. Although HIF-2α transcriptionally induced the CDK4/6 partner cyclin D1, HIF-2α was not required for the increased CDK4/6 requirement of VHL−/− ccRCC cells. Accordingly, the antiproliferative effects of CDK4/6 inhibition were synergistic with HIF-2α inhibition in HIF-2α–dependent VHL−/− ccRCC cells and not antagonistic with HIF-2α inhibition in HIF-2α–independent cells. These findings support testing CDK4/6 inhibitors as treatments for ccRCC, alone and in combination with HIF-2α inhibitors.

    更新日期:2019-10-02
  • LGP2 binds to PACT to regulate RIG-I– and MDA5-mediated antiviral responses
    Sci. Signal. (IF 6.481) Pub Date : 2019-10-01
    Raul Y. Sanchez David, Chantal Combredet, Valérie Najburg, Gael A. Millot, Guillaume Beauclair, Benno Schwikowski, Thibaut Léger, Jean-Michel Camadro, Yves Jacob, Jacques Bellalou, Nolwenn Jouvenet, Frédéric Tangy, Anastassia V. Komarova

    The retinoic acid–inducible gene I (RIG-I)–like receptors (RLRs) RIG-I, MDA5, and LGP2 stimulate inflammatory and antiviral responses by sensing nonself RNA molecules produced during viral replication. Here, we investigated how LGP2 regulates the RIG-I– and MDA5-dependent induction of type I interferon (IFN) signaling and showed that LGP2 interacted with different components of the RNA-silencing machinery. We identified a direct protein-protein interaction between LGP2 and the IFN-inducible, double-stranded RNA binding protein PACT. The LGP2-PACT interaction was mediated by the regulatory C-terminal domain of LGP2 and was necessary for inhibiting RIG-I–dependent responses and for amplifying MDA5-dependent responses. We described a point mutation within LGP2 that disrupted the LGP2-PACT interaction and led to the loss of LGP2-mediated regulation of RIG-I and MDA5 signaling. These results suggest a model in which the LGP2-PACT interaction regulates the inflammatory responses mediated by RIG-I and MDA5 and enables the cellular RNA-silencing machinery to coordinate with the innate immune response.

    更新日期:2019-10-02
  • Stress, age, and cancer
    Sci. Signal. (IF 6.481) Pub Date : 2019-10-01
    Leslie K. Ferrarelli

    Stress and advanced age suppress interferon-mediated antitumor immune surveillance and therapy.

    更新日期:2019-10-02
  • Brain-derived neurotrophic factor stimulation of T-type Ca2+ channels in sensory neurons contributes to increased peripheral pain sensitivity
    Sci. Signal. (IF 6.481) Pub Date : 2019-09-24
    Hua Wang, Yuan Wei, Yichen Pu, Dongsheng Jiang, Xinghong Jiang, Yuan Zhang, Jin Tao

    Although brain-derived neurotrophic factor (BDNF) is implicated in the nociceptive signaling of peripheral sensory neurons, the underlying mechanisms remain largely unknown. Here, we elucidated the effects of BDNF on the neuronal excitability of trigeminal ganglion (TG) neurons and the pain sensitivity of rats mediated by T-type Ca2+ channels. BDNF reversibly and dose-dependently enhanced T-type channel currents through the activation of tropomyosin receptor kinase B (TrkB). Antagonism of phosphatidylinositol 3-kinase (PI3K) but not of its downstream target, the kinase AKT, abolished the BDNF-induced T-type channel response. BDNF application activated p38 mitogen-activated protein kinase (MAPK), and this effect was prevented by inhibition of PI3K but not of protein kinase A (PKA). Antagonism of either PI3K or p38 MAPK prevented the BDNF-induced stimulation of PKA activity, whereas PKA inhibition blocked the BDNF-mediated increase in T-type currents. BDNF increased the rate of action potential firing in TG neurons and enhanced the pain sensitivity of rats to mechanical stimuli. Moreover, inhibition of TrkB signaling abolished the increased mechanical sensitivity in a rat model of chronic inflammatory pain, and this effect was attenuated by either T-type channel blockade or knockdown of the channel Cav3.2. Together, our findings indicate that BDNF enhances T-type currents through the stimulation of TrkB coupled to PI3K-p38-PKA signaling, thereby inducing neuronal hyperexcitability of TG neurons and pain hypersensitivity in rats.

    更新日期:2019-09-25
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