Evidence for a bifurcation of the mitogenic signaling pathway activated by Ras and phosphatidylcholine-hydrolyzing phospholipase C.

TitleEvidence for a bifurcation of the mitogenic signaling pathway activated by Ras and phosphatidylcholine-hydrolyzing phospholipase C.
Publication TypeJournal Article
Year of Publication1995
AuthorsBjørkøy G, Overvatn A, Diaz-Meco MT, Moscat J, Johansen T
JournalJ Biol Chem
Volume270
Issue36
Pagination21299-306
Date Published1995 Sep 08
ISSN0021-9258
Keywords3T3 Cells, Animals, Cell Transformation, Neoplastic, DNA Replication, Genes, Dominant, Hydrolysis, Mice, Mitogens, Mutation, Oncogene Protein p21(ras), Phenotype, Phorbol Esters, Phosphatidylcholines, Protein Kinases, Protein-Serine-Threonine Kinases, Proto-Oncogene Proteins, Proto-Oncogene Proteins c-raf, Signal Transduction, Type C Phospholipases
Abstract

NIH 3T3 cells stably transfected with the gene encoding phosphatidylcholine-hydrolyzing phospholipase C (PC-PLC) from Bacillus cereus display a chronic elevation of intracellular diacylglycerol levels and a transformed phenotype. We have used such PC-PLC-transformed cells to evaluate the roles of the cytoplasmic serine/threonine kinases Raf-1, zeta protein kinase C (zeta PKC) and protein kinase A (PKA) in oncogenesis and mitogenic signal transduction elicited by phosphatidylcholine hydrolysis. We demonstrate here that stable expression of dominant negative mutants of both zeta PKC and Raf-1 lead to reversion of PC-PLC-transformed cells. Interestingly, expression of kinase defective zeta PKC also reverted NIH 3T3 cells transformed by the v-Ha-ras oncogene. Activation of PKA in response to elevation of cAMP levels also lead to reversion of PC-PLC-induced transformation, implicating PKA as a negative regulator acting downstream of PC-PLC. On the other hand, inhibition or depletion of phorbol ester responsive PKCs attenuated but did not block the ability of PC-PLC-transformed cells to induce DNA synthesis in the absence of growth factors. These results clearly implicate both Raf-1 and zeta PKC as necessary downstream components for transduction of the mitogenic/oncogenic signal generated by PLC-mediated hydrolysis of phosphatidylcholine and suggest, together with other recent evidence, a bifurcation in the signaling pathway downstream of PC-PLC.

DOI10.1074/jbc.270.36.21299
Alternate JournalJ Biol Chem
PubMed ID7673165
Related Faculty: 
Jorge Moscat, Ph.D. Maria Diaz-Meco Conde, Ph.D.

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