EXPRESSION OF TYPE-V ADENYLYL-CYCLASE IS REQUIRED FOR EPIDERMAL GROWTH FACTOR-MEDIATED STIMULATION OF CAMP ACCUMULATION

Previously, this laboratory has demonstrated that epidermal growth fac tor (EGF) increases adenylyl cyclase activity in cardiac membranes and elevates cAMP accumulation in hearts and cardiac myocytes. Since EGF does not increase cAMP accumulation in all tissues, we investigated th e possibility that the expression of a specific isoform of adenylyl cy clase (AC) was necessary to observe EGF-elicited stimulation of cAMP a ccumulation, HEK 293 cells were transfected with different isoforms of AC, and the ability of EGF to increase AC activity as well as elevate cAMP accumulation was determined, In cells transfected with AC I, II, V, and VI cDNAs, neither the expression nor the amount of the two iso forms of G(s alpha) (45 and 52 kDa) were altered, Similarly, EGF-elici ted phosphorylation of cellular proteins on tyrosine residues in vario us transfectants was unaltered. However, EGF increased AC activity and elevated cAMP accumulation only in cells expressing the rat and canin e ACV, EGF did not alter either AC activity or cAMP accumulation in ce lls overexpressing types I, II, and VI isozymes, As assessed by the ab ility of an anti-G(s alpha) antibody to obliterate the effect, stimula tion of AC activity in AC V transfectants involved the participation o f G(s alpha), a finding consistent with previous data concerning EGF e ffects on cardiac AC (Nair, B. G., Parikh, B., Milligan, G., and Patel , T. B. (1990) J. Biol. Chem. 265, 21317-21322), Thus we conclude that the expression of ACV isoform confers specificity to the ability of E GF to stimulate AC activity.