Predominant expression of type-VI adenylate cyclase in C6-2B rat glioma cells may account for inhibition of cyclic AMP accumulation by calcium.
In C6-2B cells, agonist-stimulated cyclic AMP accumulation is inhibited when the cytosolic Ca2+ concentration is increased. We now demonstrate that in C6-2B cells: (i) the early kinetics of the cyclic AMP inhibition by substance K (t1/2 = 35 s) and thapsigargin (t1/2 = 1.6 min) closely mimic the kinetics of the cytosolic Ca2+ increase evoked by either agent (t1/2 = 25 s and 1.5 min respectively); (ii) the Ca2+ rise and cyclic AMP inhibition by substance K or thapsigargin are similarly affected in EGTA-containing medium; (iii) PCR detects type-III and type-VI adenylate cyclase cDNAs, and RNAase protection assays show that the mRNA for type-VI adenylate cyclase, an isoform inhibitable by submicromolar Ca2+ concentrations, is the predominant species, strongly suggesting that type-VI adenylate cyclase is probably the target molecule for Ca(2+)-mediated inhibition of cyclic AMP accumulation.
Department of Biochemistry and Molecular Biology, Georgetown University School of Medicine, Washington, DC 20007.
M A
MA
Debernardi
R
R
Munshi
M
M
Yoshimura
D M
DM
Cooper
G
G
Brooker
D000262:Adenylyl Cyclases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001932:Brain Neoplasms / Q000201:enzymology*; D002118:Calcium / Q000378:metabolism*; D000242:Cyclic AMP / Q000037:antagonists & inhibitors / Q000378:metabolism*; D004247:DNA; D005910:Glioma / Q000201:enzymology*; D007700:Kinetics; D015288:Neurokinin A / Q000494:pharmacology; D051381:Rats; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin; D014407:Tumor Cells, Cultured
D013729:Terpenes; D019284:Thapsigargin; D015288:Neurokinin A; D004247:DNA; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D002118:Calcium