title: Cell-extracellular matrix interactions stimulate the AP-1 transcription factor in an integrin-linked kinase- and glycogen synthase kinase 3-dependent manner.
abstract: Integrin-mediated interactions of cells with components of the extracellular matrix regulate cell survival, cell proliferation, cell differentiation, and cell migration. Some of these physiological responses are regulated via activation of transcription factors such as activator protein 1 (AP-1). Integrin-linked kinase (ILK) is an ankyrin repeat containing serine-threonine protein kinase whose activity is rapidly and transiently stimulated by cell-fibronectin interactions as well as by insulin stimulation. ILK activates protein kinase B and inhibits the glycogen synthase kinase 3 (GSK-3) activity in a phosphatidylinositol-3-kinase (PI 3-kinase)-dependent manner. We now show that cell adhesion to fibronectin results in a rapid and transient stimulation of AP-1 activity. At the same time, the kinase activity of ILK is stimulated whereas that of GSK-3 is inhibited. This fibronectin-dependent activation of AP-1 activity is inhibited in a dose-dependent manner if the cells are transfected with wild-type GSK-3, and also by inhibitors of PI 3-kinase. Stable or transient overexpression of ILK results in a stimulation of AP-1 activity which is inhibited by cotransfection with wild-type GSK-3 and kinase-deficient ILK. Transient transfection of ILK in HEK-293 cells stimulates complex formation between an AP-1 consensus oligonucleotide and nuclear proteins containing c-jun. The formation of this complex is inhibited by cotransfection with active GSK-3 or kinase-deficient ILK, suggesting that ILK may regulate AP-1 activation by inhibiting GSK-3, which has previously been shown to be a negative regulator of AP-1. In the presence of serum, ILK has no effect on the phosphorylation of Ser-73 in the N-terminal transactivation domain of c-jun. These results demonstrate a novel signaling pathway for the adhesion-mediated stimulation of AP-1 transcriptional activity involving ILK and GSK-3 and the subsequent regulation of the c-jun-DNA interaction.
authors.affiliation: BC Cancer Agency and Vancouver Hospital, Jack Bell Research Centre, Vancouver, British Columbia V6H 3Z6.
authors.forename: A A
authors.initials: AA
authors.lastname: Troussard
authors.forename: C
authors.initials: C
authors.lastname: Tan
authors.forename: T N
authors.initials: TN
authors.lastname: Yoganathan
authors.forename: S
authors.initials: S
authors.lastname: Dedhar
mesh_terms: D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002448:Cell Adhesion / Q000502:physiology*; D002478:Cells, Cultured; D005109:Extracellular Matrix / Q000378:metabolism*; D005353:Fibronectins / Q000378:metabolism*; D005786:Gene Expression Regulation; D038362:Glycogen Synthase Kinase 3; D038341:Glycogen Synthase Kinases; D009687:Nuclear Proteins / Q000378:metabolism; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D020218:Response Elements; D015398:Signal Transduction; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D000099200:Scaffold Protein ILK
chemical_list: D017871:Calcium-Calmodulin-Dependent Protein Kinases; D005353:Fibronectins; D038362:Glycogen Synthase Kinase 3; D038341:Glycogen Synthase Kinases; D009687:Nuclear Proteins; D017346:Protein Serine-Threonine Kinases; D016755:Proto-Oncogene Proteins c-jun; D011994:Recombinant Proteins; D018808:Transcription Factor AP-1; D000099200:Scaffold Protein ILK