α-Synuclein (αSyn) aggregation in Lewy bodies and neurites defines both familial and ‘sporadic’ Parkinson’s disease. We previously identified α-helically folded αSyn tetramers, in addition to the long-known unfolded monomers, in normal cells. PD-causing αSyn mutations decrease the tetramer:monomer (T:M) ratio, associated with αSyn hyperphosphorylation and cytotoxicity in neurons and a motor syndrome of tremor and gait deficits in transgenic mice that responds in part to L-DOPA. Here, we asked whether LRRK2 mutations, the most common genetic cause of cases previously considered sporadic PD, also alter tetramer homeostasis. Patient neurons carrying G2019S, the most prevalent LRRK2 mutation, or R1441C each had decreased T:M ratios and pSer129 hyperphosphorylation of their endogenous αSyn along with increased phosphorylation of Rab10, a widely reported substrate of LRRK2 kinase activity. Two LRRK2 kinase inhibitors normalized the T:M ratio and the hyperphosphorylation in the G2019S and R1441C patient neurons. An inhibitor of stearoyl-CoA desaturase, the rate-limiting enzyme for monounsaturated fatty acid synthesis, also restored the αSyn T:M ratio and reversed pSer129 hyperphosphorylation in both mutants. Coupled with the recent discovery that PD-causing mutations of glucocerebrosidase in Gaucher’s neurons also decrease T:M ratios, our findings indicate that three dominant genetic forms of PD involve life-long destabilization of αSyn physiological tetramers as a common pathogenic mechanism that can occur upstream of progressive neuronal synucleinopathy. Based on αSyn’s finely-tuned interaction with certain vesicles, we hypothesize that the fatty acid composition and fluidity of membranes regulate αSyn’s correct binding to highly curved membranes and subsequent assembly into metastable tetramers.

路易体和神经突中的 α-突触核蛋白 (αSyn) 聚集定义了家族性和“散发性”帕金森病。我们之前在正常细胞中鉴定出了α螺旋折叠的αSyn四聚体，以及长期已知的未折叠单体。引起 PD 的 αSyn 突变降低了四聚体：单体 (T:M) 比率，与神经元中的 αSyn 过度磷酸化和细胞毒性以及对左旋多巴有部分反应的转基因小鼠中震颤和步态缺陷的运动综合征有关。在这里，我们询问 LRRK2 突变（之前被认为是散发性 PD 病例的最常见遗传原因）是否也会改变四聚体稳态。携带最常见的 LRRK2 突变 G2019S 或 R1441C 的患者神经元的 T:M 比率降低，内源 αSyn 的 pSer129 过度磷酸化，同时 Rab10（广泛报道的 LRRK2 激酶活性底物）磷酸化增加。两种 LRRK2 激酶抑制剂使 G2019S 和 R1441C 患者神经元中的 T:M 比率和过度磷酸化正常化。硬脂酰辅酶A去饱和酶（单不饱和脂肪酸合成的限速酶）的抑制剂也恢复了两个突变体中的αSyn T:M比率并逆转了pSer129过度磷酸化。再加上最近发现戈谢神经元中引起帕金森病的葡萄糖脑苷脂酶突变也会降低 T:M 比率，我们的研究结果表明帕金森病的三种显性遗传形式涉及 αSyn 生理四聚体的终生不稳定，这是一种可能发生在上游的常见致病机制进行性神经元突触核蛋白病。 基于 αSyn 与某些囊泡的微调相互作用，我们假设脂肪酸组成和膜的流动性调节 αSyn 与高度弯曲的膜的正确结合以及随后组装成亚稳态四聚体。