MOLECULAR-CLONING AND CHARACTERIZATION OF THE TYPE-VII ISOFORM OF MAMMALIAN ADENYLYL-CYCLASE EXPRESSED WIDELY IN MOUSE-TISSUES AND IN S49 MOUSE LYMPHOMA-CELLS

We have isolated a 5199-nucleotide cDNA from a mouse library containin g an open reading frame encoding the 1099 amino acid type VII adenylyl cyclase protein. The type VII protein is most closely related in prim ary structure to an unpublished human adenylyl cyclase clone (GenBank( TM) accession no. D25538) and type II adenylyl cyclase. Northern blot analysis demonstrates that the type VII mRNA is most abundant in mouse heart, spleen, and lung. cAMP content rises rapidly in HEK 293 cells overexpressing type VII adenylyl cyclase following treatment with phor bol ester, peaking by 4 min, while cells expressing the type II adenyl yl cyclase reach peak accumulation only after 20 min. Increases in int racellular calcium through treatment of type VII-293 cells with either ATP or A23187 alone failed to increase intracellular cAMP content. Ph orbol ester treatment acted synergistically with beta-adrenergic stimu lation to increase cAMP content in type VII-transformed cells. Pretrea tment of type VII-transformed cells with pertussis toxin fails to prev ent phorbol ester potentiation of isoproterenol stimulation. Thus the ability of phorbol ester to increase basal and isoproterenol-stimulate d type VII activity appears to be a direct effect on this adenylyl cyc lase isoform and not the result of modification of the inhibitory G pr otein, G(i).