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Akt-Mediated Regulation of Autophagy and Tumorigenesis Through Beclin 1 Phosphorylation

Science  16 Nov 2012:
Vol. 338, Issue 6109, pp. 956-959
DOI: 10.1126/science.1225967

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Getting Autophagy to Akt

The protein kinase Akt is often activated in human cancers and is thought to promote tumor formation. One way in which it may do so is to inhibit autophagy (a process by which the cell digests its own proteins or organelles, especially damaged ones). Wang et al. (p. 956, published online 25 October; see the Perspective by Koren and Kimchi) provide a direct molecular mechanism by which Akt regulates autophagy. Beclin, a component of the autophagy machinery, appears to be a direct target of phosphorylation by Akt. Such phosphorylation enhanced interaction of Beclin with intermediate filaments of the cyto skeleton and inhibited autophagy. Expression of a modified Beclin 1 molecule that could not be phosphorylated by Akt inhibited Akt-induced transformation of cells in culture and tumor formation in a mouse model.

Abstract

Aberrant signaling through the class I phosphatidylinositol 3-kinase (PI3K)–Akt axis is frequent in human cancer. Here, we show that Beclin 1, an essential autophagy and tumor suppressor protein, is a target of the protein kinase Akt. Expression of a Beclin 1 mutant resistant to Akt-mediated phosphorylation increased autophagy, reduced anchorage-independent growth, and inhibited Akt-driven tumorigenesis. Akt-mediated phosphorylation of Beclin 1 enhanced its interactions with 14-3-3 and vimentin intermediate filament proteins, and vimentin depletion increased autophagy and inhibited Akt-driven transformation. Thus, Akt-mediated phosphorylation of Beclin 1 functions in autophagy inhibition, oncogenesis, and the formation of an autophagy-inhibitory Beclin 1/14-3-3/vimentin intermediate filament complex. These findings have broad implications for understanding the role of Akt signaling and intermediate filament proteins in autophagy and cancer.

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