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Regulation of autophagic activity by 14-3-3? 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 14-3-3? reduces C2-ceramide-induced autophagy, whereas depletion of 14-3-3? 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? reduces hVps34 kinase activity and depletion of 14-3-3? promotes upregulation of this activity. In this study, 14-3-3? 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.

SUBMITTER: Pozuelo-Rubio M

PROVIDER: S-EPMC3132006 | biostudies-literature | 2011 Mar

REPOSITORIES: biostudies-literature

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Regulation of autophagic activity by 14-3-3ζ proteins associated with class III phosphatidylinositol-3-kinase.

Pozuelo-Rubio M M

Cell death and differentiation 20101001 3

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-t ...[more]

PMID: 20885446

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Project description:ObjectiveMetabolic stress primes monocytes for accelerated chemokine-mediated adhesion, migration, and recruitment into vascular lesions by increasing actin remodeling. The mechanism linking metabolic stress to accelerated actin turnover and enhanced monocyte migration was not known. We tested the hypothesis that in metabolically primed monocytes, the acceleration of monocyte chemoattractant protein-1-induced chemotaxis is mediated by the hyperactivation of cofilin.Approach and resultsMetabolic priming was induced by exposing human THP-1 monocytes to diabetic conditions, that is, human native low-density lipoprotein plus high glucose concentrations. In healthy monocytes, monocyte chemoattractant protein-1 induced the phosphorylation and inactivation of cofilin. This response was completely blocked in metabolically primed monocytes but restored by overexpression of the thiol transferase, glutaredoxin 1. Cofilin kinase, LIM kinase 1, and cofilin phosphatase, Slingshot-1L, were not affected by metabolic stress. However, metabolic priming increased 3.8-fold the S-glutathionylation of the Slingshot-1L-binding protein 14-3-3ζ (zeta), resulting in its caspase-dependent degradation. Glutaredoxin 1 overexpression inhibited low-density lipoprotein plus high glucose-induced S-glutathionylation and degradation of 14-3-3ζ. The C25S mutant of 14-3-3ζ was resistant to both S-glutathionylation and degradation induced by low-density lipoprotein plus high glucose. Overexpression of the C25S mutant restored monocyte chemoattractant protein-1-induced cofilin phosphorylation and prevented accelerated migration of metabolically stressed monocytes, suggesting that loss of 14-3-3ζ increases the pool of free Slingshot-1L phosphatase, thereby preventing the phosphorylation and deactivation of cofilin in response to chemokine activation.ConclusionsBy preventing the inactivation of cofilin, metabolic stress-induced degradation of 14-3-3ζ promotes the conversion of blood monocytes into a hypermigratory, proatherogenic phenotype.

Dataset Information

Regulation of autophagic activity by 14-3-3? proteins associated with class III phosphatidylinositol-3-kinase.

Publications

Regulation of autophagic activity by 14-3-3ζ proteins associated with class III phosphatidylinositol-3-kinase.

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