Regulation Of Autophagic Activity By 14-3-3 Zeta Proteins Associated With Class Iii Phosphatidylinositol-3-Kinase

14-3-3s are binding proteins with survival functions in cells by interaction with proteins involved in the regulation of cell fate. The role of 14-3-3 during autophagy was investigated, thus, a forced expression of 14-3-3 zeta reduces C2-ceramide-induced autophagy, whereas depletion of 14-3-3 zeta promotes autophagy. The 14-3-3 role in autophagyc-related proteins was also investigated. The human vacuolar protein sorting 34 (hVps34), the class III phosphatidylinositol-3-kinase mediates multiple vesicle-trafficking processes such as endocytosis and autophagy, its activation being a requirement for autophagy initiation. Using chromatography techniques, hVps34 were eluted from a 14-3-3 affinity column, showing also a direct interaction with 14-3-3 proteins under physiological condition. Further analysis suggests that hVps34/14-3-3 association is a phorbol-12-myristate-13-acetate-dependent phosphorylated mechanism promoting a strong inhibition of the hVps34 lipid kinase activity, proteins kinase C being the likely kinase involved in phosphorylation and 14-3-3 binding of hVps34 under physiological conditions. Meanwhile, stimulation of autophagy leads to the dissociation of the 14-3-3/hVps34 complex enhancing hVps34 lipid kinase activity. Forced expression of 14-3-3 zeta reduces hVps34 kinase activity and depletion of 14-3-3 zeta promotes upregulation of this activity. In this study, 14-3-3 zeta proteins are shown as a negative regulator of autophagy through regulation of a key component of early stages of the autophagy pathway, such as hVps34. Cell Death and Differentiation (2011) 18, 479-492; doi:10.1038/cdd.2010.118; published online 1 October 2010