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 factor (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 the possibility that the expression of a specific isoform of adenylyl cyclase (AC) was necessary to observe EGF-elicited stimulation of cAMP accumulation, 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 isoforms of G(s alpha) (45 and 52 kDa) were altered, Similarly, EGF-elicited phosphorylation of cellular proteins on tyrosine residues in various transfectants was unaltered. However, EGF increased AC activity and elevated cAMP accumulation only in cells expressing the rat and canine ACV, EGF did not alter either AC activity or cAMP accumulation in cells overexpressing types I, II, and VI isozymes, As assessed by the ability of an anti-G(s alpha) antibody to obliterate the effect, stimulation of AC activity in AC V transfectants involved the participation of G(s alpha), a finding consistent with previous data concerning EGF effects 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 EGF to stimulate AC activity.