Methamphetamine-induced neurotoxicity linked to ubiquitin-proteasome system dysfunction and autophagy-related changes that can be modulated by protein kinase C delta in dopaminergic neuronal cells

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• 作者：M. Lin^a ; P. Chandramani-Shivalingappa^a ; H. Jin^a ; A. Ghosh^a ; V. Anantharam^a ; S. Ali^b ; A.G. Kanthasamy^a ; A. Kanthasamy^a ; ^{arthik@iastate.edu}
• 关键词：PKC未 ; autophagy ; methamphetamine ; apoptosis ; LC3 ; dopaminergic neuronal cells
• 刊名：Neuroscience
• 出版年：2012
• 期刊代码：50_03064522
• 类别：neu
• 出版时间：17 May, 2012
• 卷：210
• 期：Complete
• 页码：308-332
• 文件大小：6933 K

摘要

A compromised protein degradation machinery has been implicated in methamphetamine (MA)-induced neurodegeneration. However, the signaling mechanisms that induce autophagy and ubiquitin-proteasome system (UPS) dysfunction are not well understood. The present study investigates the contributions of protein kinase C delta (PKC未)-mediated signaling events in MA-induced autophagy, UPS dysfunction, and cell death. Using an in vitro mesencephalic dopaminergic cell culture model, we demonstrate that MA-induced early induction of autophagy is associated with reduction in proteasomal function and concomitant dissipation of mitochondrial membrane potential (MMP), followed by significantly increased PKC未 activation, caspase-3 activation, accumulation of ubiquitin-positive aggregates and microtubule-associated light chain-3 (LC3-II) levels. Interestingly, siRNA-mediated knockdown of PKC未 or overexpression of cleavage-resistant mutant of PKC未 dramatically reduced MA-induced autophagy, proteasomal function, and associated accumulation of ubiquitinated protein aggregates, which closely paralleled cell survival. Importantly, when autophagy was inhibited either pharmacologically (3-MA) or genetically (siRNA-mediated silencing of LC3), the dopaminergic cells became sensitized to MA-induced apoptosis through caspase-3 activation. Conversely, overexpression of LC3 partially protected against MA-induced apoptotic cell death, suggesting a neuroprotective role for autophagy in MA-induced neurotoxicity. Notably, rat striatal tissue isolated from MA-treated rats also exhibited elevated LC3-II, ubiquitinated protein levels, and PKC未 cleavage. Taken together, our data demonstrate that MA-induced autophagy serves as an adaptive strategy for inhibiting mitochondria-mediated apoptotic cell death and degradation of aggregated proteins. Our results also suggest that the sustained activation of PKC未 leads to UPS dysfunction, resulting in the activation of caspase-3-mediated apoptotic cell death in the nigrostriatal dopaminergic system.