Transfection of insulin-producing cells with a transforming c-Ha-ras oncogene stimulates phospholipase C activity.
Pancreatic islet beta-cells and insulin-producing RINm5F cells were electroporated in the presence of the c-Ha-ras oncogene, to assess the possible involvement of the encoded product in coupling extracellular receptors to phospholipase C. After two days the c-Ha-ras-transfected cells increased their expression of c-Ha-ras mRNA. These cells were also found to contain more [3H]InsP3, suggesting an increased basal (non-ligand-activated) phospholipase C activity. In addition, the transfected cells were unable to respond to ligand (bombesin) activation of phospholipase C. The ras-transfected insulin-producing cells showed enhanced phosphorylation of a 200 kDa substrate crossreacting with an antibody to an 80 kDa protein kinase C substrate. The phorbol ester 12-O-tetradecanoyl 13-acetate and bombesin also induced phosphorylation of the 200 kDa substrate. All of these changes occurred without changes in the rates of [3H]thymidine incorporation. The results suggest that the mutated c-Ha-ras oncogene directly or indirectly stimulates the basal phospholipase C activity of these cells.
Berggren
P O
PO
Department of Medical Cell Biology, Uppsala University, Sweden.
Hallberg
A
A
Welsh
N
N
Arkahammar
P
P
Nilsson
T
T
Welsh
M
M
D000818:Animals; D001839:Bombesin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D011905:Genes, ras; D007515:Islets of Langerhans / Q000187:drug effects / Q000201:enzymology*; D051379:Mice; D010766:Phosphorylation; D011506:Proteins / Q000378:metabolism; D013755:Tetradecanoylphorbol Acetate; D014162:Transfection; D010738:Type C Phospholipases / Q000378:metabolism*
D011506:Proteins; D010738:Type C Phospholipases; D013755:Tetradecanoylphorbol Acetate; D001839:Bombesin; D002118:Calcium