BACKGROUND Neuroinflammation, typified by elevated levels of interleukin-1 (IL-1) α and β, and deficits in proteostasis, characterized by accumulation of polyubiquitinated proteins and other aggregates, are associated with neurodegenerative disease independently and through interactions of the two phenomena. We investigated the influence of IL-1β on ubiquitination via its impact on activation of the E3 ligase parkin by either phosphorylated ubiquitin (P-Ub) or NEDD8. METHODS Immunohistochemistry and Proximity Ligation Assay were used to assess colocalization of parkin with P-tau or NEDD8 in hippocampus from Alzheimer patients (AD) and controls. IL-1β effects on PINK1, P-Ub, parkin, P-parkin, and GSK3β-as well as phosphorylation of parkin by GSK3β-were assessed in cell cultures by western immunoblot, using two inhibitors and siRNA knockdown to suppress GSK3β. Computer modeling characterized the binding and the effects of P-Ub and NEDD8 on parkin. IL-1α, IL-1β, and parkin gene expression was assessed by RT-PCR in brains of 2- and 17-month-old PD-APP mice and wild-type littermates. RESULTS IL-1α, IL-1β, and parkin mRNA levels were higher in PD-APP mice compared with wild-type littermates, and IL-1α-laden glia surrounded parkin- and P-tau-laden neurons in human AD. Such neurons showed a nuclear-to-cytoplasmic translocation of NEDD8 that was mimicked in IL-1β-treated primary neuronal cultures. These cultures also showed higher parkin levels and GSK3β-induced parkin phosphorylation; PINK1 levels were suppressed. In silico simulation predicted that binding of either P-Ub or NEDD8 at a singular position on parkin opens the UBL domain, exposing Ser65 for parkin activation. CONCLUSIONS The promotion of parkin- and NEDD8-mediated ubiquitination by IL-1β is consistent with an acute neuroprotective role. However, accumulations of P-tau and P-Ub and other elements of proteostasis, such as translocated NEDD8, in AD and in response to IL-1β suggest either over-stimulation or a proteostatic failure that may result from chronic IL-1β elevation, easily envisioned considering its early induction in Down's syndrome and mild cognitive impairment. The findings further link autophagy and neuroinflammation, two important aspects of AD pathogenesis, which have previously been only loosely related.

中文翻译：

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白介素-1β驱动NEDD8核转至细胞质，通过NEDD8与P-泛素激活位点结合促进帕金激活。

背景技术以白细胞介素-1（IL-1）α和β水平升高为代表的神经发炎，以及以多聚泛素化蛋白和其他聚集体的积累为特征的蛋白变性不足，均与神经退行性疾病相关，并通过两种现象的相互作用而发生。我们研究了IL-1β通过其对磷酸化泛素（P-Ub）或NEDD8对E3连接酶Parkin活化的影响而对泛素化的影响。方法采用免疫组织化学和邻近结扎法评估帕金蛋白与P-tau或NEDD8在阿尔茨海默病患者和对照组海马中的共定位。通过Western免疫印迹评估了IL-1β对PINK1，P-Ub，Parkin，P-parkin和GSK3β的影响以及GSK3β对Parkin磷酸化的影响，使用两种抑制剂和siRNA抑制来抑制GSK3β。计算机建模表征了P-Ub和NEDD8对Parkin的结合以及其作用。通过RT-PCR在2和17个月大的PD-APP小鼠和野生型同窝幼仔的大脑中评估IL-1α，IL-1β和parkin基因的表达。结果与野生型同窝幼仔相比，PD-APP小鼠的IL-1α，IL-1β和Parkin mRNA水平更高，并且在人AD中，IL-1α负载的神经胶质细胞包围了帕金蛋白和P-tau负载的神经元。此类神经元显示出NEDD8的核转胞质易位，在IL-1β处理的原代神经元培养物中被模仿。这些培养物还显示出较高的帕金水平和GSK3β诱导的帕金磷酸化。PINK1水平受到抑制。在计算机模拟中预测，P-Ub或NEDD8在Parkin的单个位置上的结合会打开UBL结构域，暴露Ser65进行Parkin激活。结论IL-1β促进Parkin和NEDD8介导的泛素化与急性神经保护作用一致。但是，AD中和响应IL-1β时，P-tau和P-Ub以及其他蛋白变形的元素（例如易位NEDD8）的蓄积表明，过度刺激或由于长期IL-1β升高而引起的蛋白稳定失败，考虑到其在唐氏综合征中的早期诱导和轻度认知障碍，很容易想到。这些发现进一步将自噬和神经炎症联系在一起，这是AD发病机理的两个重要方面，以前仅是松散相关。很容易想到，AD中P-tau和P-Ub以及其他蛋白质变形的元素（例如易位的NEDD8）的积累以及对IL-1β的反应提示过度刺激或可能由于慢性IL-1β升高而引起的蛋白修复失败。考虑其在唐氏综合症和轻度认知障碍中的早期诱导作用。这些发现进一步将自噬和神经炎症联系在一起，这是AD发病机理的两个重要方面，以前仅是松散相关。很容易想到，AD中P-tau和P-Ub以及其他蛋白质变形的元素（例如易位的NEDD8）的积累以及对IL-1β的反应提示过度刺激或可能由于慢性IL-1β升高而引起的蛋白修复失败。考虑其在唐氏综合症和轻度认知障碍中的早期诱导作用。这些发现进一步将自噬和神经炎症联系在一起，这是AD发病机理的两个重要方面，以前仅是松散相关。