Atg1-mediated myosin II activation regulates autophagosome formation during starvation-induced autophagy

Abstract

Autophagy is a membrane‐mediated degradation process of macromolecule recycling. Although the formation of double‐membrane degradation vesicles (autophagosomes) is known to have a central role in autophagy, the mechanism underlying this process remains elusive. The serine/threonine kinase Atg1 has a key role in the induction of autophagy. In this study, we show that overexpression of Drosophila Atg1 promotes the phosphorylation‐dependent activation of the actin‐associated motor protein myosin II. A novel myosin light chain kinase (MLCK)‐like protein, Spaghetti‐squash activator (Sqa), was identified as a link between Atg1 and actomyosin activation. Sqa interacts with Atg1 through its kinase domain and is a substrate of Atg1. Significantly, myosin II inhibition or depletion of Sqa compromised the formation of autophagosomes under starvation conditions. In mammalian cells, we found that the Sqa mammalian homologue zipper‐interacting protein kinase (ZIPK) and myosin II had a critical role in the regulation of starvation‐induced autophagy and mammalian Atg9 (mAtg9) trafficking when cells were deprived of nutrients. Our findings provide evidence of a link between Atg1 and the control of Atg9‐mediated autophagosome formation through the myosin II motor protein. There is a [Have you seen?][1] (February 2011) associated with this Article. [1]: http://dx.doi.org/10.1038/emboj.2011.8