PP2Ac甲基化在锰暴露诱导神经细胞自噬障碍中的作用研究

亮氨酸甲基转移酶(leucine carboxyl methyltransferase-1,LCMT-1 )催化PP2Ac甲基化对PP2A发挥去磷酸化功能具有重要作用，ULK1去磷酸化是自噬启动的关键事件。甲基化的PP2A通过调控mTORC1/ULK1而调控自噬。锰诱导神经细胞退行性变与抑制自噬有关。前期研究提示锰暴露诱导PP2Ac去甲基化。根据前期结果及文献推测锰通过氧化应激诱导PP2Ac去甲基化，PP2A活性下降，mTORC1磷酸化活化而对ULK1抑制增强，抑制细胞自噬，从而发生退行性改变。本研究拟通过细胞实验与动物实验相结合，研究锰对神经细胞自噬的影响，探讨补充ABL-1、抗氧化剂（NAC）及转染过表达LCMT-1质粒调控PP2A-C甲基化后UKL1去磷酸状态及神经细胞自噬的变化。本研究为深入理解锰神经毒性，改善锰诱导的神经退行性疾病，提供防治方法的新思路。

The methylation of C- terminal leucine residue of PP2A catalytic subunit is important for PP2A executing its dephosphorylation function, methylated by leucine carboxyl methyltransferase-1,LCMT-1. Dephosphorylatoin of ULK1 (Unc-51 like kinase-1) is a key event to initiate autophagy. Neurodegenerative change due to excessive Mn exposure is associated to abnormal autophagy. Our previous studies showed PP2Ac methylation decreased upon manganese exposure. In view of other literatures and our own results, we speculate that autophagy impaired by manganese might due to PP2A catalytic subunit demethylation and its catalytic activity loss, ULK1 dephosphorylation following mammalian target of rapamycin complex 1(mTORC1) activation through manganese disruption ROS generation. The present study is designed to investigate the impact of high level Mn exposure on autophagy in vivo and vitro. We also discuss the pathways of PP2A-C methylation regulated by Protein Phosphatase Methyl-Esterase inhibitor (ABL-127), antioxidant (N-acetyl-L-cysteine, NAC) and transfection LCMT-1 overexpression into SK-N-SH neurons and their effects on ULK1 dephosphorylation and autophagy. This study will help to insight to manganese neurotoxicity and to provide some new strategies for prevention and treatment of neurodegenerative diseases upon elevated manganese exposure.