| Abstract: | Pulmonary artery smooth muscle cell (PASMC)adhesion, spreading, and migration depend on matrix-stimulatedreorganization of focal adhesions. Platelet-derived growth factor(PDGF) activates intracellular signal transduction cascades that alsoregulate adhesion, spreading, and migration, but the signalingmolecules involved in these events are poorly defined. We hypothesizedthat phosphatidylinositol (PI) 3-kinases and Src tyrosine kinasestranslate matrix and PDGF-initiated signals into cell motility. Inexperiments with cultured canine PASMCs, inhibition of PI 3-kinaseswith wortmannin (0.3 µM) and LY-294002 (50 µM) and of Src kinasewith PP1 (30 µM) did not decrease spontaneous (nonstimulated) orPDGF-stimulated (10 ng/ml) adhesion onto collagen. PI 3-kinase and Srckinase activities, however, were necessary for cell spreading: PP1inhibited cell spreading and Src Tyr-418 phosphorylation in aconcentration-dependent manner. Inhibition of PI 3-kinase and Srcpartially reduced cell migration, while at 10 and 30 µM, PP1eliminated migration, likely due to inhibition of PDGF receptors. Inconclusion, both PI 3-kinases and Src tyrosine kinases are componentsof pathways that mediate spreading and migration of cultured PASMCs on collagen. |
