Vascular endothelial growth factor-mediated activation of p38 is dependent upon Src and RAFTK/Pyk2.
Vascular endothelial growth factor (VEGF) induces activation of p38 mitogen-activated protein kinase (MAPK) in primary endothelial cells and may be critical for VEGF-induced angiogenesis. We investigated the molecular basis for p38 activation in response to VEGF. The expression of a C-terminal splice variant of FAK, FRNK, had no affect on VEGF-induced activation of p38; however, expression of a dominant-negative RAFTK/Pyk2 mutant led to a decrease in the activation of p38, but had no affect on extracellular signal-regulated kinase (ERK). Since calcium regulates RAFTK/Pyk2, we investigated its role in p38 activity. Preincubation with EGTA suppressed p38 activation, while calcium ionophore induced p38 activity. Inhibition of phospholipase C (PLC) resulted in complete inhibition of ERK, while having no affect on p38 activity. These data suggested a bifurcation in the regulation of MAPKs that occurs at the level of PLC and RAFTK/Pyk2 activation. Src family kinases interact with RAFTK/Pyk2. Inhibition of Src by either pharmacological or genetic means decreased p38 activity. Finally, we found that both Src and RAFTK/Pyk2 were essential for endothelial cell migration. These data identified a novel regulatory network involving extracellular calcium, RAFTK/Pyk2, Src and p38. This signaling network appears to be critical for VEGF-induced endothelial cell migration.
McMullen
Meghan
M
Center for Cell Biology and Cancer Research, Albany Medical College, Albany NY, USA.
Keller
Rebecca
R
Sussman
Mark
M
Pumiglia
Kevin
K
D002118:Calcium / Q000502:physiology; D002478:Cells, Cultured; D002633:Chemotaxis / Q000187:drug effects / Q000502:physiology*; D016895:Culture Media, Serum-Free; D004533:Egtazic Acid / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology*; D004789:Enzyme Activation; D051418:Focal Adhesion Kinase 2; D006801:Humans; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D018919:Neovascularization, Physiologic; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D014471:Umbilical Veins; D042461:Vascular Endothelial Growth Factor A / Q000494:pharmacology*; D048051:p38 Mitogen-Activated Protein Kinases; D019061:src-Family Kinases / Q000378:metabolism*
D016895:Culture Media, Serum-Free; D042461:Vascular Endothelial Growth Factor A; D004533:Egtazic Acid; D011505:Protein-Tyrosine Kinases; D051418:Focal Adhesion Kinase 2; D019061:src-Family Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D002118:Calcium