Insulin-Regulated Adenylyl Cyclase Signaling System in Cell Culture of Mouse Fibroblasts of L Line

In terms of the subsequent study of the earlier discovered adenylyl cyclase signaling mechanism of insulin action 1, 2], we studied participation in it of various isoforms of protein kinase C. As object of study, a culture of mouse fibroblast cells of the L line (LSM subline) was chosen. It has been shown that insulin and a non-hydrolyzed analog of GTP, GppNH]p, stimulate the adenylyl cyclase (AC) activity in these cells both individually and in combination. Activators of phorbol-sensitive isoforms of protein kinase C, diacylglycerol and phorbol ester (phorbol-12-myristate-13-acetate) at their concentrations of 1–100 nM stimulate basal activity of AC. In their presence, a significant decrease of stimulating effects of insulin and GppNH]p or their complete disappearance are observed. Calphostin C (1–100 nM), an inhibitor of both phorbol-sensitive and atypical, phorbol-insensitive isoforms of protein kinase C, somewhat increased the basal AC activity. However, the stimulating effects of insulin and GppNH]p in the presence of calphostin C decreased markedly. On the whole, the obtained data allow us to suggest participation of various isoforms of protein kinase C (sensitive and insensitive to the phorbol esters) in regulation of the process of the insulin signal transduction in mouse fibroblasts through the adenylyl cyclase signaling mechanism. Thus, mechanisms of functioning of the insulin-regulated AC-system in fibroblasts, representatives of connective tissue cells, are similar to those that we described earlier in muscle tissues of vertebrate and invertebrate animals. Taken together, these data indicate the absence of tissue- and species-specificity in functioning of the insulin-regulated AC system and its wide spread in tissues of different animals.