NIH-3T3 cells transformed with a ras oncogene exhibit a protein kinase C-mediated inhibition of agonist-stimulated Ca2+ inflow.
1. The ability of bombesin or platelet-derived growth factor (PDGF) to stimulate Ca2+ inflow (assessed by measuring changes in the intracellular free Ca2+ concentration in cells loaded with fura-2) in NIH-3T3 cells transformed with the EJ/T24-Ha-ras-1 oncogene is inhibited when compared with the action of the agonists on wild-type cells. 2. The effects of transformation with the ras oncogene are associated with complete inhibition of the ability of bombesin to release Ca2+ from intracellular stores, a substantial decrease in the number of bombesin receptors, no change in the ability of foetal calf serum or ionomycin to release Ca2+ from intracellular stores and the activation of protein kinase C. 3. The effects of transformation with the H-ras oncogene on the ability of bombesin or PDGF to stimulate Ca2+ inflow were mimicked by a 30 min exposure of wild-type cells to phorbol dibutyrate. This action of phorbol dibutyrate was completely blocked by prior treatment of wild-type cells for 24 h with the phorbol ester. 4. It is concluded that one of the actions of the H-ras oncogene in fibroblasts is to inhibit agonist-stimulated Ca2+ inflow by a mechanism which involves the activation of protein kinase C.
Polverino
A J
AJ
Department of Medical Biochemistry, Flinders University School of Medicine, Bedford Park, South Australia.
Hughes
B P
BP
Barritt
G J
GJ
D000818:Animals; D001839:Bombesin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002461:Cell Line, Transformed; D002471:Cell Transformation, Neoplastic; D004533:Egtazic Acid / Q000494:pharmacology; D004789:Enzyme Activation; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism*; D019886:Gastrin-Releasing Peptide; D011905:Genes, ras; D051379:Mice; D010455:Peptides / Q000378:metabolism; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism*; D018004:Receptors, Bombesin; D017981:Receptors, Neurotransmitter / Q000378:metabolism
D010455:Peptides; D010982:Platelet-Derived Growth Factor; D018004:Receptors, Bombesin; D017981:Receptors, Neurotransmitter; D015240:Phorbol 12,13-Dibutyrate; D004533:Egtazic Acid; D019886:Gastrin-Releasing Peptide; D011493:Protein Kinase C; D001839:Bombesin; D002118:Calcium