ACTIVATION OF CYTOSOLIC PHOSPHOLIPASE A(2) BY BASIC FIBROBLAST GROWTH-FACTOR VIA A P42 MITOGEN-ACTIVATED PROTEIN KINASE-DEPENDENT PHOSPHORYLATION PATHWAY IN ENDOTHELIAL-CELLS

Basic fibroblast growth factor (FGF) stimulates the proliferation, dif ferentiation, and motility of multiple cell types, Signal transduction by FGF is mediated by high affinity FGF receptors that have autophosp horylating tyrosine kinase activity and also elicit the release of low molecular weight signaling molecules, including inositol 1,4,5-trisph osphate, diacylglycerol, and arachidonate. We have shown previously th at basic FGF-stimulated, phospholipase A(2) (PLA(2))-mediated arachido nate release regulates endothelial cell (EC) motility (Sa, G., and Fox , P. L. (1994) J. Biol. Chem, 269, 3219-3225). Here we identify the ph ospholipase responsible for basic FGF-mediated arachidonate release as cytosolic PLA(2) (cPLA(2)) by demonstrating in EC lysates a requireme nt for micromolar Ca2+, dithiothreitol insensitivity, and inactivation by anti-cPLA(2), antiserum, The role of cPLA(2) is also indicated by the observed mechanisms of activation which show a requirement for p42 mitogen-activated protein kinase activity, cPLA(2) phosphorylation, a nd cPLA(2) translocation from cytosol to membranes, Phosphorylation of cPLA(2), arachidonate release from prelabeled intact cells, and cell motility all have similar concentration dependencies on basic FGF, Sin ce arachidonate release is required for basic FGF-stimulated motility of EC, our results show that p42 mitogen-activated protein kinase acti vation of cPLA, may be a regulatory event in stimulation of cellular r elease of this important eicosanoid precursor during cellular response s to basic FGF.