1. ¹Center for Cell Biology and Cancer Research, Albany Medical College, Albany NY, USA
2. ²Center for Cardiovascular Sciences, Albany Medical College, Albany NY, USA
3. ³Division of Cardiology, Cinncinnati Children's Hospital, Cinncinnati, OH, USA

Correspondence: K Pumiglia, Center for Cell Biology and Cancer Research, Mail Code 165, Albany, Medical College, 47 New Scotland Ave., Albany, NY 12208, USA. E-mail: pumiglk@mail.amc.edu

Received 24 July 2003; Revised 23 September 2003; Accepted 23 September 2003; Published online 15 December 2003.

Abstract

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.