BASIC FIBROBLAST GROWTH-FACTOR STIMULATES PHOSPHATIDYLCHOLINE-HYDROLYZING PHOSPHOLIPASE-D IN OSTEOBLAST-LIKE CELLS

We examined the effect of basic fibroblast growth factor (bFGF) on the activation of phosphatidylcholine-hydrolyzing phospholipase D in oste oblast-like MC3T3-E1 cells. bFGF stimulated both the formations of cho line (EC(50) was 30 ng/ml) and inositol phosphates (EC(50) was 10 ng/m l. Calphostin C, an inhibitor of protein kinase C (PKC), had little ef fect on the bFGF-induced formation of choline. bFGF stimulated the for mation of choline also in PKC down regulated cells. Genistein and meth yl 2,5-dihydroxycinnamate, inhibitors of protein tyrosine kinases, sig nificantly suppressed the bFGF-induced formation of choline. Sodium or thovanadate, an inhibitor of protein tyrosine phosphatases, enhanced t he bFGF-induced formation of choline. In vitro kinase assay for FGF re ceptors revealed that FGF receptor 1 and 2 were autophosphorylated aft er FGF stimulation. bFCF dose-dependently stimulated DNA synthesis of these cells. These results strongly suggest that bFGF activates phosph atidylcholine-hydrolyzing phospholipase D through the activation of ty rosine kinase, but independently of PKC activated by phosphoinositide hydrolysis in osteoblast-like cells. (C) 1996 Wiley-Liss, Inc.