Abstract C150: CaMKKβ-mediated phosphorylation of Beclin 1 regulates autophagy and cell differentiation in neuroblastoma cells.

Autophagy is an evolutionarily conserved degradative pathway by which components of the cells are degraded in the lysosome in response to stress. Beclin 1 plays a central role in autophagy. Pioneering work has indicated that the increase in cytosolic Ca(2+) can induce autophagy via the CaMKKβ-mediated activation of AMPK. Here, we demonstrate a novel signaling pathway in which CaMKKβ regulates autophagy and differentiation. We found that Ca(2+) mobilizing agents (ionomycin and EB1089) induced phosphorylation of Beclin 1 and autophagy through CaMKKβ-dependent pathway. Using In vitro kinase assay we demonstrated that CaMKKβ directly phosphorylated Beclin 1 Ser90. Moreover, autophagy induced by ionomycin or EB1089 contributed to degradation of Id1 (inhibitor of differentiation). The inhibitors of autophagy including Bafilomycin A1 and chloroquine and RNA interference of autophagy-associated gene atg 5 markedly increased the protein levels of Id1 and abrogated neuroblastoma cell differentiation. Taken together, CaMKKβ promoted autophagy by directly phosphorylating Beclin 1 at Ser90, and thus induced cell differentiation in neuroblastoma cells. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr C150.