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Protein kinase B phosphorylation of PIKfyve regulates the trafficking of GLUT4 vesicles

2004; The Company of Biologists; Volume: 117; Issue: 25 Linguagem: Inglês

10.1242/jcs.01517

1477-9137

Daniel C. Berwick, Ghislaine Dell, Gavin I. Welsh, Kate J. Heesom, Ingeborg Hers, Laura M. Fletcher, Frank T. Cooke, Jeremy M. Tavaré,

Protein Kinase Regulation and GTPase Signaling

Insulin-stimulated glucose uptake involves the recruitment of the glucose transporter 4 isoform (GLUT4) from an intracellular location to the plasma membrane of fat and muscle cells. Although the activation of the PI3-kinase/protein kinase B (PKB) pathway is central to this effect of insulin, the key substrates for PKB that are involved require identification. Here we report that serine318 on the FYVE domain-containing PtdIns3P 5-kinase (PIKfyve) is a novel substrate for PKB, and show that phosphorylation stimulates the PtdIns3P 5-kinase activity of the enzyme. We also demonstrate that PIKfyve is phosphorylated on serine318 in intact cells in response to insulin, in a PI3-kinase-dependent manner, and that PIKfyve colocalises with a highly motile subpopulation of insulin-regulated aminopeptidase (IRAP)/GLUT4 vesicles. Finally, we demonstrate that overexpression of a PIKfyve[S318A] mutant in 3T3-L1 adipocytes enhances insulin-stimulated IRAP/GLUT4 vesicle translocation to the plasma membrane suggesting a role for PKB-dependent phosphorylation of PIKfyve in insulin-regulated IRAP/GLUT4 trafficking. The phosphorylation and activation of PIKfyve by PKB provides a novel signalling paradigm that may link plasma membrane-localised PtdIns(3,4,5)P3 signals via a protein kinase cascade to regulated PtdIns(3,5)P2 production, and thereby to the control of trafficking of other membrane cargos.