title: Integrin alpha 2 beta 1 promotes activation of protein phosphatase 2A and dephosphorylation of Akt and glycogen synthase kinase 3 beta.
abstract: Serine/threonine kinase Akt is a downstream effector protein of phosphatidylinositol-3-kinase (PI-3K). Many integrins can function as positive modulators of the PI-3K/Akt pathway. Integrin alpha 2 beta 1 is a collagen receptor that has been shown to induce specific signals distinct from those activated by other integrins. Here, we found that, in contrast what was found for cells adherent to fibronectin, alpha 2 beta 1-mediated cell adhesion to collagen leads to dephosphorylation of Akt and glycogen synthase kinase 3 beta (GSK3 beta) and concomitantly to the induction of protein serine/threonine phosphatase 2A (PP2A) activity. PP2A activation can be inhibited by mutation in the alpha 2 cytoplasmic domain and by a function-blocking anti-alpha 2 antibody. Akt can be coprecipitated with PP2A, and coexpression of Akt with PP2Ac (catalytic subunit) inhibits Akt kinase activity. Integrin alpha 2 beta 1-related activation of PP2A is dependent on Cdc42. These results indicate that cell adhesion to collagen modulates Akt activity via the alpha 2 beta 1-induced activation of PP2A.
authors.affiliation: MediCity and Department of Medical Biochemistry,University of Turku, FIN-20520 Turku, Finland.
authors.forename: Johanna
authors.initials: J
authors.lastname: Ivaska
authors.forename: Liisa
authors.initials: L
authors.lastname: Nissinen
authors.forename: Nina
authors.initials: N
authors.lastname: Immonen
authors.forename: John E
authors.initials: JE
authors.lastname: Eriksson
authors.forename: Veli-Matti
authors.initials: VM
authors.lastname: Kähäri
authors.forename: Jyrki
authors.initials: J
authors.lastname: Heino
mesh_terms: D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002448:Cell Adhesion; D002478:Cells, Cultured; D003094:Collagen; D004789:Enzyme Activation; D038362:Glycogen Synthase Kinase 3; D038341:Glycogen Synthase Kinases; D006801:Humans; D016023:Integrins / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D010749:Phosphoprotein Phosphatases / Q000378:metabolism*; D011485:Protein Binding; D054648:Protein Phosphatase 2; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D038981:Receptors, Collagen; D015398:Signal Transduction; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D016023:Integrins; D011518:Proto-Oncogene Proteins; D038981:Receptors, Collagen; D003094:Collagen; D038341:Glycogen Synthase Kinases; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D038362:Glycogen Synthase Kinase 3; D010749:Phosphoprotein Phosphatases; D054648:Protein Phosphatase 2; D020764:cdc42 GTP-Binding Protein