Department of Biochemistry, Institute of Post-Graduate Medical Education and Research (IPGMER), Kolkata, India.
Department of Geriatric Medicine, Institute of Medical Sciences (IMS), Banaras Hindu University (BHU), Varanasi, India.
Biochem J. 2020 Mar 27;477(6):1109-1122. doi: 10.1042/BCJ20190676.
The toxicity of accumulated α-synuclein plays a key role in the neurodegeneration of Parkinson's disease (PD). This study has demonstrated that iron in varying concentrations (up to 400 µM) causes an increase in α-synuclein content in SH-SY5Y cells associated with mitochondrial depolarization, decreased cellular ATP content and loss of cell viability during incubation up to 96 h. Knocking-down α-synuclein expression prevents cytotoxic actions of iron, which can also be prevented by cyclosporine A (a blocker of mitochondrial permeability transition pore). These results indicate that iron cytotoxicity is mediated by α-synuclein acting on mitochondria. Likewise siRNA mediated knock-down of Parkin causes an accumulation of α-synuclein accompanied by mitochondrial dysfunction and cell death during 48 h incubation under basal conditions, but these changes are not further aggravated by co-incubation with iron (400 µM). We have also analyzed mitochondrial dysfunction and cell viability in SH-SY5Y cells under double knock-down (α-synuclein and Parkin concurrently) conditions during incubation for 48 h with or without iron. Our results tend to suggest that iron inactivates Parkin in SH-SY5Y cells and thereby inhibits the proteasomal degradation of α-synuclein, and the accumulated α-synuclein causes mitochondrial dysfunction and cell death. These results have implications in the pathogenesis of sporadic PD and also familial type with Parkin mutations.
α-突触核蛋白的毒性在帕金森病 (PD) 的神经退行性变中起关键作用。本研究表明，不同浓度的铁（高达 400μM）会导致 SH-SY5Y 细胞中α-突触核蛋白含量增加，与线粒体去极化、细胞内 ATP 含量减少和细胞活力丧失有关，孵育时间长达 96 小时。敲低α-突触核蛋白表达可防止铁的细胞毒性作用，而环孢菌素 A（线粒体通透性转换孔的阻断剂）也可防止铁的细胞毒性作用。这些结果表明，铁的细胞毒性是由作用于线粒体的α-突触核蛋白介导的。同样，在基础条件下孵育 48 小时时，Parkin 的 siRNA 介导敲低会导致α-突触核蛋白积累，伴随着线粒体功能障碍和细胞死亡，但在与铁（400μM）共孵育时，这些变化不会进一步加重。我们还分析了在铁存在或不存在的情况下，SH-SY5Y 细胞在双重敲低（α-突触核蛋白和 Parkin 同时敲低）条件下孵育 48 小时时的线粒体功能障碍和细胞活力。我们的结果表明，铁在 SH-SY5Y 细胞中使 Parkin 失活，从而抑制α-突触核蛋白的蛋白酶体降解，而积累的α-突触核蛋白导致线粒体功能障碍和细胞死亡。这些结果对散发性 PD 以及伴有 Parkin 突变的家族性 PD 的发病机制具有重要意义。
