Inhibition of serum- and ras-stimulated DNA synthesis by antibodies to phospholipase C.
Several immunologically distinct isozymes of inositol phospholipid-specific phospholipase C (PLC) have been purified from bovine brain. Murine NIH 3T3 fibroblasts were found to express PLC-gamma, but the expression of PLC-beta was barely detectable by radioimmunoassay or protein immunoblot. A mixture of monoclonal antibodies was identified that neutralizes the biological activity of both endogenous and injected purified PLC-gamma. When co-injected with oncogenic Ras protein or PLC-gamma, this mixture of antibodies inhibited the induction of DNA synthesis that characteristically results from the injection of these proteins into quiescent 3T3 cells. However, when oncogenic Ras protein or PLC-gamma was co-injected with a neutralizing monoclonal antibody to Ras, only the DNA synthesis induced by the Ras protein was inhibited--that induced by PLC was unaffected. These results suggest that the Ras protein is an upstream effector of PLC activity in phosphoinositide-specific signal transduction and that PLC-gamma activity is necessary for Ras-mediated induction of DNA synthesis.
Biological Carcinogenesis and Development Program, National Cancer Institute-Frederick Cancer Research Facility, MD 21701.
M R
MR
Smith
Y L
YL
Liu
H
H
Kim
S G
SG
Rhee
H F
HF
Kung
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D002460:Cell Line; D004247:DNA / Q000096:biosynthesis*; D005347:Fibroblasts; D006133:Growth Substances / Q000494:pharmacology; D006825:Hybridomas; D015151:Immunoblotting; D007399:Interphase; D007527:Isoenzymes / Q000276:immunology / Q000378:metabolism*; D008845:Microinjections; D015689:Oncogene Protein p21(ras) / Q000276:immunology / Q000494:pharmacology*; D011863:Radioimmunoassay; D015398:Signal Transduction; D010738:Type C Phospholipases / Q000276:immunology / Q000378:metabolism* / Q000494:pharmacology
D000911:Antibodies, Monoclonal; D006133:Growth Substances; D007527:Isoenzymes; D004247:DNA; D010738:Type C Phospholipases; D015689:Oncogene Protein p21(ras)