Adenovirus-mediated expression of an olfactory cyclic nucleotide-gated channel regulates the endogenous Ca2+-inhibitable adenylyl cyclase in C6-2B glioma cells

Previous studies have established that Ca2+-sensitive adenylyl cyclases, wh ether endogenously or heterologously expressed, are preferentially regulate d by capacitative Ca2+ entry, compared with other means of elevating cytoso lic Ca2+ (Chiono, M,, Mahey, R,, Tate, G,, and Cooper, D, Ni. F. (1995) J. Biol. Chem, 270, 1149-1155; Fagan, K, A, Mahey, R,, and Cooper, D, M. F, (1 996) J, Biol, Chem, 271, 12438-12444; Fagan, K, A., Mons, N,, and Cooper, D , M. F, (1998) J. Biol. Chem. 273, 9297-9305), These findings led to the su ggestion that adenylyl cyclases and capacitative Ca2+ entry channels were l ocalized in the same functional domain of the plasma membrane, In the prese nt study, we have asked whether a heterologously expressed Ca2+-permeable c hannel could regulate the Ca2+-inhibitable adenylyl cyclase of C6-2B glioma cells. The cDNA coding for the rat olfactory cyclic nucleotide-gated chann el was inserted into an adenovirus construct to achieve high levels of expr ession. Electrophysiological measurements confirmed the preservation of the properties of the expressed olfactory channel. Stimulation of the channel with cGMP analogs yielded a robust elevation in cytosolic Ca2+, which was a ssociated with an inhibition of cAMP accumulation, comparable with that eli cited by capacitative Ca2+ entry. These findings not only extend the means whereby Ca2+-sensitive adenylyl cyclases may be regulated, they also sugges t that in tissues where they co-exist, cyclic nucleotidegated channels and Ca2+ sensitive adenylyl cyclases may reciprocally modulate each other's act ivity.