Platelet-derived growth factor-BB (PDGF-BB) regulation of migration and focal adhesion kinase phosphorylation in rabbit aortic vascular smooth muscle cells: roles of phosphatidylinositol 3-kinase and mitogen-activated protein kinases.
OBJECTIVE
Phosphatidylinositol 3'-kinase (PI3-kinase) is implicated in cell migration and focal adhesion kinase (FAK) phosphorylation. In contrast, it has been proposed that mitogen-activated protein (MAP) kinases are essential for proliferation but may be dissociated from chemotactic signalling. We investigated the roles of PI3-kinase and p42/p44 MAP kinases in cell migration and FAK tyrosine phosphorylation induced by platelet-derived growth factor-BB (PDGF-BB) in rabbit aortic vascular smooth muscle cells (VSMCs). The roles of PI3-kinase and MAP kinase pathways in the chemotactic response to insulin-like growth factor-I (IGF-I) were also examined.


METHODS
The roles of PI3-kinase and p42/p44 MAP kinases were assessed using the PI3-kinase inhibitors, wortmannin and LY294002, and an inhibitor of MAP kinase kinase, PD98059. PI3-kinase activity was measured by phosphatidylinositol phosphorylation in anti-phosphotyrosine immunoprecipitates and by thin layer chromatography of phosphorylated products. Phosphorylation was assessed by immunoprecipitation with anti-phosphotyrosine antibodies and Western blotting with FAK-specific antibody. Migration was evaluated in a chemotaxis chamber using polycarbonate filters with an 8-mm pore size.


RESULTS
Neither wortmannin nor LY294002 significantly reduced PDGF-BB stimulation of FAK tyrosine phosphorylation, chemotaxis or immunofluorescent staining of focal adhesions in VSMCs. PD98059, a specific inhibitor of MAP kinase activation, did not inhibit FAK tyrosine phosphorylation but markedly inhibited the migratory response of VSMCs to PDGF-BB. IGF-I also stimulated migration of VSMCs, and, relative to the effect of PDGF-BB, induced smaller increases in PI3-kinase and MAP kinase activities. Both wortmannin and PD98059 partially inhibited the migratory response to IGF-I.


CONCLUSIONS
PDGF-BB stimulation of both FAK tyrosine phosphorylation and migration in VSMCs are not dependent on activation of PI3-kinase. While PDGF-BB stimulation of FAK tyrosine phosphorylation is not dependent on p42/p44 MAP kinase activation, PDGF-BB and IGF-I both stimulate p42/p44 MAP kinase activity and the chemotactic response to these factors is partially dependent on MAP kinase activation.
Cospedal
R
R
Wolfson Institute for Biomedical Research, University College London, UK.
Abedi
H
H
Zachary
I
I
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D001011:Aorta; D000077214:Becaplermin; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D002448:Cell Adhesion / Q000187:drug effects; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D002465:Cell Movement / Q000187:drug effects; D002478:Cells, Cultured; D002867:Chromones / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D051416:Focal Adhesion Protein-Tyrosine Kinases; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology; D009025:Morpholines / Q000494:pharmacology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D020574:Proto-Oncogene Proteins c-sis; D011817:Rabbits; D013268:Stimulation, Chemical; D000077191:Wortmannin
D000730:Androstadienes; D000077214:Becaplermin; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D015815:Cell Adhesion Molecules; D002867:Chromones; D004791:Enzyme Inhibitors; D005419:Flavonoids; D051416:Focal Adhesion Protein-Tyrosine Kinases; D007334:Insulin-Like Growth Factor I; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010982:Platelet-Derived Growth Factor; D011505:Protein-Tyrosine Kinases; D020574:Proto-Oncogene Proteins c-sis; D000077191:Wortmannin; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one