Prostaglandin F2α activates phospholipase D independently from activation of protein kinase C in osteoblast‐like cells

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Abstract
We previously reported that prostaglandin F2α (PGF2α) receptor is coupled to pertussis toxin (PTX)–sensitive GTP‐binding protein (G protein) in osteoblast‐like MC3T3‐E1 cells [Miwa et al. (1990): Biochem Biophys Res Commun 171:1229–1235]. In the present study, we examined the effect of PGF2α on the activation of phosphatidylcholine‐hydrolyzing phospholipase D in MC3T3‐E1 cells. PGF2α stimulated the formation of choline in a dose‐dependent manner in the range between 10 nM and 10 μM. The formation of choline was stimulated by 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA), a protein kinase C (PKC)–activating phorbol ester. 4α‐Phorbol 12,13‐didecanoate, a PKC‐nonactivating phorbol ester, had little effect on choline formation. The formation of choline stimulated by a combination of PGF2α and TPA was additive. Staurosporine, an inhibitor for protein kinases, which inhibited the effect of TPA on choline formation, dose‐dependently enhanced the formation of choline induced by PGF2α. NaF, an activator of G protein, stimulated the formation of choline. The formation of choline stimulated by a combination of PGF2α and NaF was not additive. NaF‐induced formation of choline was dose‐dependently enhanced by staurosporine. PTX dose‐dependently inhibited the PGF2α‐induced formation of choline. These results strongly suggest that PGF2α activates phospholipase D independently from the activation of PKC in osteoblast‐like cells and PTX‐sensitive G protein is involved in the PGF2α‐induced phospholipase D activation.