The Critical Role Of Kapl In LBH589 Induced Autophagosome Formation In MCF-7 Cells

Autophagy, a cellular catabolic pathway, is evolutionary conserved from yeast to mammals. Central to this process is the formation of autophagosomes, double-membrane vesicles responsible for delivering long-lived proteins and excess or damaged organelle into the lysosome for degradation and utility of the resulting macromolecules. Activity of Vacuolar protein sorting 34 (Vps34), the class Ⅲ PtdIns3 kinase, which specifically phosphorylate the D3 position of PtdIns to produce phosphatidylinositol (3)-phosphate (PtdIns(3)P) at the PAS for the recruitment of other Atg proteins is essential for AV formation in autophagy. However, the exact mechanisms for autophagy-inducing stress to regulate Vps34 activity has not yet been fully elucidated.Our findings demonstrated that LBH589, a highly potent HDAC inhibitor, increases either the intracellular levels of acetylated inducible heat shock protein (hsp) 70 or the levels and cytoplasmic accumulation of KRAB-ZFP-associated protein 1 (KAP)1. Acetylated Hsp70 binds to and stabilize the Beclin-1-Vps34 complex through the recruitment of KAP1, which has E3-like activity for sumolyation, resulting the SUMOylation of VPS34, subsequently increase Vps34 lipid kinase activity and its ability bound to Beclinl. Knockdown of Hsp70 abolished the Beclinl-Vps34 complex formation, as well as ability of KAP1 binding to Vps34 and AV formation. Our findings provide new insights into a regulatory mechanism of Vps34 activity, which involves acetylated hsp70 and KAP1-dependent SUMOylation of Vps34 in VPS34-Beclinl complex during autophagosome formation.