Mechanisms underlying extensive Ser129-phosphorylation in α-synuclein aggregates.
Mechanisms underlying extensive Ser129-phosphorylation in α-synuclein aggregates.
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DOI：
10.1186/s40478-017-0452-6
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发表时间：
2017-06-15
影响因子：
7.1
通讯作者：
Kato T
中科院分区：
文献类型：
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作者：
Arawaka S;Sato H;Sasaki A;Koyama S;Kato T
帕金森病(PD)的神经病理特征是纤维状α-突触核蛋白在细胞内聚集，称为路易小体(Lbs)。在帕金森病患者的脑中，大约90%的α-突触核蛋白以LBS的形式沉积，在Ser129位被磷酸化。相比之下，在正常人的大脑中，只有4%的α-突触核蛋白在Ser129位被磷酸化。帕金森病的病理过程中发生广泛的磷酸化的原因尚不清楚。为了解决这个问题，我们研究了Ser129-磷酸化在调节α-突触核蛋白积累中的机制和作用。在CHO细胞中，胞内和胞外的Ser129磷酸化的可溶性α-突触核蛋白的水平与总α-突触核蛋白的水平保持不变。在SH-SY5Y细胞和大鼠原代皮质神经元中，鱼藤酮或MPP+对线粒体的损伤通过增加细胞外钙离子内流来增强Ser129的磷酸化。这种升高是通过将Ser129磷酸化的α-突触核蛋白靶向蛋白酶体途径来抑制的。鱼藤酮诱导的不溶性α-突触核蛋白也被丝氨酸129-磷酸化作用靶向蛋白酶体途径。环氧米星和氯喹的实验表明，在溶酶体抑制下，不溶性Ser129磷酸化的α-突触核蛋白的蛋白酶体靶向性增强，并减少了不溶性总α-突触核蛋白的蓄积。然而，在腺病毒介导的α-突触核蛋白过度表达模型中，A53T突变体和A53T+S129A双突变体的α-突变体α-突变体的总α-突起数量没有差异，尽管表达A53T-突触核蛋白的大鼠α-突触核蛋白阳性聚集体增加。这些发现表明，在应激条件下，Ser129-磷酸化发生，从而增加细胞外钙离子的内流，并通过激发与溶酶体互补的蛋白酶体清除来防止不溶性α-突触核蛋白的积累。然而，Ser129-磷酸化可能为耐降解的聚集体提供无效的信号，导致聚集体中广泛的磷酸化。本文的在线版本(doi：10.1186/s40478-0170452-6)包含补充材料，授权用户可以使用。
Parkinson’s disease (PD) is characterized neuropathologically by intracellular aggregates of fibrillar α-synuclein, termed Lewy bodies (LBs). Approximately 90% of α-synuclein deposited as LBs is phosphorylated at Ser129 in brains with PD. In contrast, only 4% of total α-synuclein is phosphorylated at Ser129 in brains with normal individuals. It is unclear why extensive phosphorylation occurs in the pathological process of PD. To address this issue, we investigated a mechanism and role of Ser129-phosphorylation in regulating accumulation of α-synuclein. In CHO cells, the levels of Ser129-phosphorylated soluble α-synuclein were maintained constantly to those of total α-synuclein in intracellular and extracellular spaces. In SH-SY5Y cells and rat primary cortical neurons, mitochondrial impairment by rotenone or MPP+ enhanced Ser129-phosphorylation through increased influx of extracellular Ca2+. This elevation was suppressively controlled by targeting Ser129-phosphorylated α-synuclein to the proteasome pathway. Rotenone-induced insoluble α-synuclein was also targeted by Ser129-phosphoryation to the proteasome pathway. Experiments with epoxomicin and chloroquine showed that proteasomal targeting of insoluble Ser129-phosphorylated α-synuclein was enhanced under lysosome inhibition and it reduced accumulation of insoluble total α-synuclein. However, in a rat AAV-mediated α-synuclein overexpression model, there was no difference in the number of total α-synuclein aggregates between A53T mutant and A53T plus S129A double mutant α-synuclein, although Ser129-phosphorylated α-synuclein-positive aggregates were increased in rats expressing A53T α-synuclein. These findings suggest that Ser129-phosphorylation occurs against stress conditions, which increases influx of extracellular Ca2+, and it prevents accumulation of insoluble α-synuclein by evoking proteasomal clearance complementary to lysosomal one. However, Ser129-phosphorylation may provide an ineffective signal for degradation-resistant aggregates, causing extensive phosphorylation in aggregates. The online version of this article (doi:10.1186/s40478-017-0452-6) contains supplementary material, which is available to authorized users.