title: Regulation of protein kinase B/Akt activity and Ser473 phosphorylation by protein kinase Calpha in endothelial cells.
abstract: Protein kinase Balpha (PKBalpha/Akt-1) is a key mediator of multiple signaling pathways involved in angiogenesis, cell proliferation and apoptosis among others. The unphosphorylated form of Akt-1 is virtually inactive and its full activation requires two phosphatidylinositol-3,4,5-triphosphate-dependent phosphorylation events, Thr308 by 3-phosphoinositide-dependent kinase-1 (PDK1) and Ser473 by an undefined kinase that has been termed PDK2. Recent studies have suggested that the Ser473 kinase is a plasma membrane raft-associated kinase. In this study we show that protein kinase Calpha (PKCalpha) translocates to the membrane rafts in response to insulin growth factor-1 (IGF-1) stimulation. Overexpression of PKCalpha increases Ser473 phosphorylation and Akt-1 activity, while inhibition of its activity or expression decreases IGF-1-dependent activation of Akt-1. Furthermore, in vitro, in the presence of phospholipids and calcium, PKCalpha directly phosphorylates Akt-1 at the Ser473 site. We conclude, therefore, that PKCalpha regulates Akt-1 activity via Ser473 phosphorylation and may function as PDK2 in endothelial cells.
authors.affiliation: Department of Medicine, Angiogenesis Research Center and Section of Cardiology, Dartmouth Medical School, Dartmouth-Hitchcock Medical Center, One Medical Center Drive, Lebanon, NH 03756, USA.
authors.forename: Chohreh
authors.initials: C
authors.lastname: Partovian
authors.forename: Michael
authors.initials: M
authors.lastname: Simons
mesh_terms: D064413:3-Phosphoinositide-Dependent Protein Kinases; D000818:Animals; D042783:Endothelial Cells / Q000201:enzymology*; D004789:Enzyme Activation; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D021962:Membrane Microdomains; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D051571:Protein Kinase C-alpha; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D012694:Serine / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D011518:Proto-Oncogene Proteins; D012694:Serine; D007334:Insulin-Like Growth Factor I; D064413:3-Phosphoinositide-Dependent Protein Kinases; C494920:Akt1 protein, rat; C578579:Pdpk1 protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D011493:Protein Kinase C; D051571:Protein Kinase C-alpha