Parkin Regulates Mitophagic Cell Death in Adult Hippocampal Neural Stem Cells Following Insulin Withdrawal

Abstract

Insulin is a key factor in the hippocampal function, and proliferation of hippocampal neural stem (HCN) cells is dependent on insulin signaling. We have previously demonstrated that adult rat HCN cells undergo autophagic cell death (ACD) following insulin withdrawal despite their intact apoptotic capability. Here, we show that insulin-deprived HCN cells undergo ACD through Parkin-dependent mitophagy. Mitophagy is one of the selective forms of autophagy to maintain healthy mitochondria by degradation of defective or damaged mitochondria in various stress condition. However, excessive mitophagy may also lead to mitophagic cell death. Insulin withdrawal increased the amount of depolarized mitochondria and induced LC3-II translocation from the cytosol to depolarized mitochondria in HCN cells. Interestingly, insulin withdrawal up-regulated both mRNA and protein levels of Parkin in c-Jun-dependent manner. CRISPR/Cas9-mediated knockout of the Parkin gene reduced mitophagy level and ACD. Taken together, these results indicated that Parkin is required for the induction of mitophagic cell death in HCN cells following insulin withdrawal.