title: Phosphoinositide-3-OH kinase-dependent regulation of glycogen synthase kinase 3 and protein kinase B/AKT by the integrin-linked kinase.
abstract: Integrin-linked kinase (ILK) is an ankyrin-repeat containing serine-threonine protein kinase capable of interacting with the cytoplasmic domains of integrin beta1, beta2, and beta3 subunits. Overexpression of ILK in epithelial cells disrupts cell-extracellular matrix as well as cell-cell interactions, suppresses suspension-induced apoptosis (also called Anoikis), and stimulates anchorage-independent cell cycle progression. In addition, ILK induces nuclear translocation of beta-catenin, where the latter associates with a T cell factor/lymphocyte enhancer-binding factor 1 (TCF/LEF-1) to form an activated transcription factor. We now demonstrate that ILK activity is rapidly, but transiently, stimulated upon attachment of cells to fibronectin, as well as by insulin, in a phosphoinositide-3-OH kinase [Pi(3)K]-dependent manner. Furthermore, phosphatidylinositol(3,4,5)trisphosphate specifically stimulates the activity of ILK in vitro, and in addition, membrane targetted constitutively active Pi(3)K activates ILK in vivo. We also demonstrate here that ILK is an upstream effector of the Pi(3)K-dependent regulation of both protein kinase B (PKB/AKT) and glycogen synthase kinase 3 (GSK-3). Specifically, ILK can directly phosphorylate GSK-3 in vitro and when stably, or transiently, overexpressed in cells can inhibit GSK-3 activity, whereas the overexpression of kinase-deficient ILK enhances GSK-3 activity. In addition, kinase-active ILK can phosphorylate PKB/AKT on serine-473, whereas kinase-deficient ILK severely inhibits endogenous phosphorylation of PKB/AKT on serine-473, demonstrating that ILK is involved in agonist stimulated, Pi(3)K-dependent, PKB/AKT activation. ILK is thus a receptor-proximal effector for the Pi(3)K-dependent, extracellular matrix and growth factor mediated, activation of PKB/AKT, and inhibition of GSK-3.
authors.affiliation: British Columbia Cancer Agency, Jack Bell Research Centre, 2660 Oak Street, Vancouver, British Columbia V6H 3Z6 Canada.
authors.forename: M
authors.initials: M
authors.lastname: Delcommenne
authors.forename: C
authors.initials: C
authors.lastname: Tan
authors.forename: V
authors.initials: V
authors.lastname: Gray
authors.forename: L
authors.initials: L
authors.lastname: Rue
authors.forename: J
authors.initials: J
authors.lastname: Woodgett
authors.forename: S
authors.initials: S
authors.lastname: Dedhar
mesh_terms: D000595:Amino Acid Sequence; D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002460:Cell Line; D004789:Enzyme Activation / Q000502:physiology; D005353:Fibronectins / Q000494:pharmacology; D038362:Glycogen Synthase Kinase 3; D038341:Glycogen Synthase Kinases; D007328:Insulin / Q000494:pharmacology; D008969:Molecular Sequence Data; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism / Q000494:pharmacology; D010750:Phosphoproteins / Q000032:analysis; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000502:physiology*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D016415:Sequence Alignment; D014162:Transfection / Q000235:genetics; D000077191:Wortmannin; D000099200:Scaffold Protein ILK
chemical_list: D000730:Androstadienes; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D005353:Fibronectins; D038362:Glycogen Synthase Kinase 3; D038341:Glycogen Synthase Kinases; D007328:Insulin; D019869:Phosphatidylinositol 3-Kinases; D018129:Phosphatidylinositol Phosphates; D010750:Phosphoproteins; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D011994:Recombinant Proteins; D000077191:Wortmannin; D000099200:Scaffold Protein ILK; C060974:phosphatidylinositol 3,4,5-triphosphate; C494920:Akt1 protein, rat