Chromatin-Bound Oxidized α-Synuclein Causes Strand Breaks in Neuronal Genomes in in vitro Models of Parkinson's Disease.
Chromatin-Bound Oxidized α-Synuclein Causes Strand Breaks in Neuronal Genomes in in vitro Models of Parkinson's Disease.
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DOI：
10.3233/jad-170342
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
Hegde ML
中科院分区：
文献类型：
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作者：
Vasquez V;Mitra J;Hegde PM;Pandey A;Sengupta S;Mitra S;Rao KS;Hegde ML
α-突触核蛋白（α-Syn）在退行性多巴胺能神经元中的过表达和错误折叠/聚集长期以来与帕金森病（PD）有关。α-Syn的神经毒性被铁（Fe）和其他促氧化金属增强，导致PD脑内活性氧的产生。虽然α-Syn主要定位于突触前神经末梢，但也有一小部分存在于神经元核中。然而，核α-Syn的功能和/或病理作用尚不清楚。在我们之前报道α-Syn在体外直接结合DNA的基础上，我们利用邻近连接和染色质免疫沉淀分析证实了α-Syn在神经元中的核定位和染色质关联。诱导多能人干细胞（iPSCs）或分化的SHSY-5Y细胞衍生的神经系祖细胞(NPC) α-Syn表达适度（~2倍）增加，导致核基因组DNA链断裂，铁盐进一步协同增强α-Syn表达。此外，α-Syn需要核定位才能诱导基因组损伤，这一点通过细胞核对细胞质特异性突变体的影响得到了证实。氧化和错误折叠/寡聚α-Syn对DNA损伤的增强表明，DNA缺口活性是由错误折叠α-Syn中氧化肽段的化学核酸酶活性介导的。与这一发现一致的是，在PD患者衍生的iPSC细胞系中观察到铁依赖性DNA断裂的显著增加，该细胞系含有三倍的SNCA基因。α-Syn联合Fe可显著促进神经元细胞死亡。总之，这些发现为α-Syn在诱导神经元基因组损伤中的直接作用提供了新的分子视角，这可能有助于PD的神经退行性变。
Alpha-synuclein (α-Syn) overexpression and misfolding/aggregation in degenerating dopaminergic neurons have long been implicated in Parkinson’s disease (PD). The neurotoxicity of α-Syn is enhanced by iron (Fe) and other pro-oxidant metals, leading to generation of reactive oxygen species in PD brain. Although α-Syn is predominantly localized in presynaptic nerve terminals, a small fraction exists in neuronal nuclei. However, the functional and/or pathological role of nuclear α-Syn is unclear. Following up on our earlier report that α-Syn directly binds DNA in vitro, here we confirm the nuclear localization and chromatin association of α-Syn in neurons using proximity ligation and chromatin immunoprecipitation analysis. Moderate (~2-fold) increase in α-Syn expression in neural lineage progenitor cells (NPC) derived from induced pluripotent human stem cells (iPSCs) or differentiated SHSY-5Y cells caused DNA strand breaks in the nuclear genome, which was further enhanced synergistically by Fe salts. Furthermore, α-Syn required nuclear localization for inducing genome damage as revealed by the effect of nucleus versus cytosol-specific mutants. Enhanced DNA damage by oxidized and misfolded/oligomeric α-Syn suggests that DNA nicking activity is mediated by the chemical nuclease activity of an oxidized peptide segment in the misfolded α-Syn. Consistent with this finding, a marked increase in Fe-dependent DNA breaks was observed in NPCs from a PD patient-derived iPSC line harboring triplication of the SNCA gene. Finally, α-Syn combined with Fe significantly promoted neuronal cell death. Together, these findings provide a novel molecular insight into the direct role of α-Syn in inducing neuronal genome damage, which could possibly contribute to neurodegeneration in PD.