PHOSPHATIDYLCHOLINE-SPECIFIC PHOSPHOLIPASE INHIBITOR D609 DIFFERENTIALLY AFFECTS MAP KINASES AND IMMEDIATE-EARLY GENES IN PC12 CELLS

The effects of tricyclodecan-9-yl xanthogenate (D609), an inhibitor of phosphatidylcholine-specific phospholipases, on PC12 cells were inves tigated. D609 repressed nerve growth factor (NGF)-mediated induction o f c-fos mRNA with an IC50 approximate to 50 mu g/ml. Interestingly, ma ximal c-fos-suppressing doses of D609 did not affect activity of extra cellular signal-regulated kinases. Surprisingly, D609 enhanced the ext racellular acidification rate of PC12 cells, even in the absence of NG F. D609 alone induced c-jun mRNA with the same potency as it repressed the NGF-induced expression of c-Jos. Like NGF, D609 alone induced c-j un even in the presence of dominant-negative Ras. Immediate-early indu ction of c-jun mRNA by NGF and D609 was abrogated by pretreatment with the kinase inhibitor olomoucine. Jun kinase, which is inhibited by ol omoucine, was found to be activated by D609. Thus, D609 might induce c -jun in PC12 cells as a consequence of Jun kinase activation through a Ras-independent pathway. Under the same conditions, D609 repressed NG F-mediated induction of c-fos mRNA. (C) 1998 Elsevier Science Inc.