title: Regulation of autophagic activity by 14-3-3ζ proteins associated with class III phosphatidylinositol-3-kinase.
abstract: 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 14-3-3ζ reduces C2-ceramide-induced autophagy, whereas depletion of 14-3-3ζ 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 14-3-3ζ reduces hVps34 kinase activity and depletion of 14-3-3ζ promotes upregulation of this activity. In this study, 14-3-3ζ 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.
authors.affiliation: Centro Andaluz de Biología Molecular y Medicina Regenerativa, Consejo Superior de Investigaciones Científicas, Sevilla, Spain. merce_pozo@yahoo.es
authors.forename: M
authors.initials: M
authors.lastname: Pozuelo-Rubio
mesh_terms: D048948:14-3-3 Proteins / Q000378:metabolism*; D001343:Autophagy / Q000187:drug effects; D002457:Cell Extracts; D045744:Cell Line, Tumor; D002846:Chromatography, Affinity; D058546:Class III Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D015536:Down-Regulation / Q000187:drug effects; D004789:Enzyme Activation / Q000187:drug effects; D057809:HEK293 Cells; D006801:Humans; D010703:Phorbol Esters / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects; D034741:RNA, Small Interfering / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013110:Sphingosine / Q000031:analogs & derivatives / Q000494:pharmacology
chemical_list: D048948:14-3-3 Proteins; D002457:Cell Extracts; C064769:N-acetylsphingosine; D010703:Phorbol Esters; D034741:RNA, Small Interfering; C119222:phorbol-12-myristate; D058546:Class III Phosphatidylinositol 3-Kinases; D013110:Sphingosine