<i>Drosophila</i> aux orchestrates the phosphorylation-dependent assembly of the lysosomal V-ATPase in glia and contributes to SNCA/α-synuclein degradation

Glia contribute to the neuropathology of Parkinson disease (PD), but how they react opposingly to be beneficial or detrimental under pathological conditions, like promoting or eliminating SNCA/α-syn (synuclein alpha) inclusions, remains elusive. Here we present evidence that aux (auxilin), the <i>Drosophila</i> homolog of the PD risk factor GAK (cyclin G associated kinase), regulates the lysosomal degradation of SNCA/α-syn in glia. Lack of glial GAK/aux increases the lysosome number and size, regulates lysosomal acidification and hydrolase activity, and ultimately blocks the degradation of substrates including SNCA/α-syn. Whereas SNCA/α-syn accumulates prominently in lysosomes devoid of glial aux, levels of injected SNCA/α-syn preformed fibrils are further enhanced in the absence of microglial GAK. Mechanistically, aux mediates phosphorylation at the serine 543 of Vha44, the V₁ C subunit of the vacuolar-type H⁺-translocating ATPase (V-ATPase), and regulates its assembly to control proper acidification of the lysosomal milieu. Expression of Vha44, but not the Vha44 variant lacking S543 phosphorylation, restores lysosome acidity, locomotor deficits, and DA neurodegeneration upon glial aux depletion, linking this pathway to PD. Our findings identify a phosphorylation-dependent switch controlling V-ATPase assembly for lysosomal SNCA/α-syn degradation in glia. Targeting the clearance of glial SNCA/α-syn inclusions via this lysosomal pathway could potentially be a therapeutic approach to ameliorate the disease progression in PD. <b>Abbreviation</b>: aux: auxilin; GAK: cyclin G associated kinase; LTG: LysoTracker Green; LTR: LysoTracker Red; MR: Magic Red; PD: Parkinson disease; SNCA/a-syn: synuclein alpha; V-ATPase: vacuolar-type H⁺-translocating ATPase

胶质细胞（glia）参与帕金森病（Parkinson disease, PD）的神经病理进程，但在病理条件下，其如何发挥双向调控作用——既可以促进SNCA/α-突触核蛋白（synuclein alpha）包涵体的生成，又能清除这类包涵体，具体机制仍尚不明确。
本研究证实，aux（辅助蛋白，auxilin）——即帕金森病风险因子GAK（周期蛋白G相关激酶，cyclin G associated kinase）的果蝇（Drosophila）同源蛋白——可调控胶质细胞内SNCA/α-突触核蛋白的溶酶体降解过程。胶质细胞中GAK/aux的缺失会增加溶酶体的数量与体积，调控溶酶体酸化水平与水解酶活性，最终阻断包括SNCA/α-突触核蛋白在内的多种底物的降解。当胶质细胞缺乏aux时，SNCA/α-突触核蛋白会在溶酶体中大量蓄积；而在小胶质细胞GAK缺失的情况下，注射的SNCA/α-突触核蛋白预形成纤维的水平会进一步升高。
机制层面，aux可介导Vha44（液泡型H⁺-转运ATP酶（vacuolar-type H⁺-translocating ATPase, V-ATPase）的V₁ C亚基）的丝氨酸543位点磷酸化，并调控其组装以维持溶酶体微环境的正常酸化。恢复野生型Vha44的表达（而非缺失S543磷酸化位点的Vha44突变体），可逆转胶质细胞aux缺失导致的溶酶体酸化异常、运动功能障碍及多巴胺能神经元变性，将该信号通路与帕金森病的病理过程直接关联。
本研究揭示了一种依赖磷酸化的调控开关，可通过控制V-ATPase的组装来调控胶质细胞内SNCA/α-突触核蛋白的溶酶体降解。通过该溶酶体途径靶向清除胶质细胞中的SNCA/α-突触核蛋白包涵体，或可成为改善帕金森病疾病进展的潜在治疗策略。
**缩写说明**：aux：辅助蛋白（auxilin）；GAK：周期蛋白G相关激酶（cyclin G associated kinase）；LTG：LysoTracker Green；LTR：LysoTracker Red；MR：Magic Red；PD：帕金森病（Parkinson disease）；SNCA/α-syn：α-突触核蛋白（synuclein alpha）；V-ATPase：液泡型H⁺-转运ATP酶（vacuolar-type H⁺-translocating ATPase）

搜集汇总

背景与挑战

背景概述

该数据集研究了果蝇auxilin蛋白（GAK同源物）在神经胶质细胞中通过调控V-ATPase磷酸化依赖性组装，影响溶酶体酸化和SNCA/α-突触核蛋白降解的机制。研究揭示了auxilin缺失会导致溶酶体功能异常和SNCA积累，从而关联帕金森病的神经退行过程，为靶向溶酶体通路治疗帕金森病提供了潜在策略。