title: Dissociation of mitogen-activated protein kinase activation from p125 focal adhesion kinase tyrosine phosphorylation in Swiss 3T3 cells stimulated by bombesin, lysophosphatidic acid, and platelet-derived growth factor.
abstract: The experiments presented here were designed to examine the contribution of p125 focal adhesion kinase (p125FAK) tyrosine phosphorylation to the activation of the mitogen-activated protein kinase cascade induced by bombesin, lysophosphatidic acid (LPA), and platelet-derived growth factor (PDGF) in Swiss 3T3 cells. We found that tyrosine phosphorylation of p125FAK in response to these growth factors is completely abolished in cells treated with cytochalasin D or in cells that were suspended in serum-free medium for 30 min. In marked contrast, the activation of p42mapk by these factors was independent of the integrity of the actin cytoskeleton and of the interaction of the cells with the extracellular matrix. The protein kinase C inhibitor GF 109203X and down-regulation of protein kinase C by prolonged pretreatment of cells with phorbol esters blocked bombesin-stimulated activation of p42mapk, p90rsk, and MAPK kinase-1 but did not prevent bombesin-induced tyrosine phosphorylation of p125FAK. Furthermore, LPA-induced p42mapk activation involved a pertussis toxin-sensitive guanylate nucleotide-binding protein, whereas tyrosine phosphorylation of p125FAK in response to LPA was not prevented by pretreatment with pertussis toxin. Finally, PDGF induced maximum p42mapk activation at concentrations (30 ng/ml) that failed to induce tyrosine phosphorylation of p125FAK. Thus, our results demonstrate that p42mapk activation in response to bombesin, LPA, and PDGF can be dissociated from p125FAK tyrosine phosphorylation in Swiss 3T3 cells.
authors.affiliation: Imperial Cancer Research Fund, London, United Kingdom.
authors.forename: T
authors.initials: T
authors.lastname: Seufferlein
authors.forename: D J
authors.initials: DJ
authors.lastname: Withers
authors.forename: D
authors.initials: D
authors.lastname: Mann
authors.forename: E
authors.initials: E
authors.lastname: Rozengurt
mesh_terms: D016475:3T3 Cells; D000818:Animals; D001839:Bombesin / Q000494:pharmacology; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D018797:Cell Cycle Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D016213:Cyclins / Q000378:metabolism; D015638:Cytochalasin D / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D008246:Lysophospholipids / Q000494:pharmacology; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D019950:Mitogen-Activated Protein Kinase 1; D010766:Phosphorylation; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D016160:Retinoblastoma Protein / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D025521:Tumor Suppressor Proteins; D014443:Tyrosine / Q000378:metabolism*
chemical_list: C493961:Cdkn1b protein, mouse; D015815:Cell Adhesion Molecules; D018797:Cell Cycle Proteins; D016213:Cyclins; D008246:Lysophospholipids; D008869:Microtubule-Associated Proteins; D010982:Platelet-Derived Growth Factor; D016160:Retinoblastoma Protein; D025521:Tumor Suppressor Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D015638:Cytochalasin D; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496051:Ptk2 protein, mouse; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D001839:Bombesin