| Macroautophagy is a cellular process that sequesters cytoplasmic content into autophagosomes for subsequent degradation. Precise regulation of macroautophagy ensures cell survival, with either excessive or insufficient level of macroautophagy leading to cell death. In addition, deregulation of macroautophagy has been implicated in the pathophysiology of various neurodegenerative disorders. Nonetheless, the mechanism by which macroautophagy deregulation contributes to neuronal death in these disorders remains largely unclear. Cdk5 is a serine/threonine kinase that is aberrantly activated in a number of neurodegenerative disorders, including Parkinson's disease. While basal Cdk5 activity is important for neuronal survival, aberrant activation of Cdk5 triggers neuronal death. The present study reveals a novel role of Cdk5 in regulating macroautophagy induction in neurons. Cdk5 phosphorylates endophilin B1 at Thr145 to mediate macroautophagy induction in starved neurons. Moreover, Thr145 phosphorylation of endophilin B1 by Cdk5 promotes endophilin B1 dimerization and recruitment of macroautophagy proteins UVRAG and Beclin 1, whereas this phosphorylation does not alter endophilin B1's lipid binding property or facilitate its localization to pre-autophagosomal membranes. Importantly, macroautophagy induction is essential for neuronal death in two Parkinson's disease models involving either MPTP toxicity or mutant A53T alpha-synuclein expression. Furthermore, Cdk5-mediated Thr145 endophilin B1 phosphorylation is required for macroautophagy induction and neuronal death in these Parkinson's disease models. This study thus reveals an unanticipated role of Cdk5 and endophilin B1 in the pathogenesis of Parkinson's disease through the regulation of macroautophagy. |
