Molecular regulation of TRPC1 on the toxicity mediated by α-synuclein in multiple system atrophy

Multiple system atrophy (MSA) is a progressive neuron degenerative disease characterized by glial cytoplasmic inclusions containing insoluble α-synuclein and autonomic failure associated with either poorly levodopa-responsive TRPC1-sonism or cerebellar ataxia or both. Studies have shown that α-synuclein plays very important role in the pathogenesis of MSA, but the molecular mechanism of the toxicity is still unclear. On the basis of many previous studies about calcium dyshomeostasis caused by the intracellular oxidative stress conditions, we put forward a new hypothesis of Bergmann glia death which is closely related to the oxidative stress during the progress of MSA. In order to compare the difference between α-synuclein overexpressed U251 cells with or without TRPC1 RNA interference in response to free iron, we investigated the cell apoptosis by Western-blot and measuring activated caspase activity. The interrelations of autophagy and neuron death were studied by assessing the level of LC-3 protein and autophagosomes; and then the cell survival was measured by cell count and MTT assay. In this study, we gave a deep analysis of the molecular mechanism of neuron death in α-synuclein overexpressed U251 cells in some respects of cell apoptosis, autophagy and calcium ion channels and so on. Firstly, we analysed the relation of α-synuclein and overexpressed TRPC1. Our results indicated that α-synuclein overexpression in U251 cells could inhibit cell growth and increase the level of oxidative stress. And then, the expression of some important proteins such as calcium channels protein TRPC1, autophagy related protein LC-3B and death receptor DR5 were increased obviously. Meanwhile, with the downregulation of TRPC1, we investigated the change of cell death and the oxidative level of α-synuclein overexpression U251 cells during the progress, and we can see the cell toxicity of U251 cells with α-synuclein overexpression was effectively changed. All results demonstrated that α-synuclein overexpression can destroy cell calcium homeostasis by increasing the level of membranous calcium channels protein TRPC1. Besides, it can increase the level of apoptosis and autophagy, and the level of oxidative stress which might be the reason of MSA. We tried to give a reasonable explanation and provide a clue for the prevention and treatment of MSA.