Cell-specific properties of type V and type IX adenylyl cyclase isozymes in 293T cells and embryonic chick ventricular myocytes

The cDNAs for types V and IX adenylyl cyclases were cloned from a chicken heart library and expressed in 293T cells (plasmid transfection) and in embryonic chick ventricular myocytes (adenovirus infection). Expression of type V or IX cyclases in 293T cells resulted in increases in basal and isoproterenol (ISO)-stimulated cAMP levels, whereas the expression of type V, but not type IX, cyclase increased forskolin (FK)-stimulated cAMP levels. Expression of type V cyclase in cardiac myocytes increased basal and FK-stimulated cAMP levels, variably increased ISO-stimulated cAMP levels, and decreased the content of beta-adrenergic receptors (betaARs). The expression of type IX cyclase in cardiac myocytes increased basal and ISO-elevated cAMP levels and, surprisingly, increased the cAMP-elevating effect of FK. The finding that FK responses are increased in cardiac myocytes but not in 293T cells expressing the type IX cyclase suggests that the host cell influences the properties of the type IX isozyme.