Modulation by 1,25(OH)2-vitamin D3 of the adenylyl cyclase/cyclic AMP pathway in rat and chick myoblasts.
We have previously reported that the calciotropic hormone 1,25(OH)2-vitamin D3 stimulates influx of Ca2+ into cultured rat and embryonic chick myoblasts via voltage sensitive Ca(2+)-channels. In the present study, we show that this effect of 1,25(OH)2D3 requires the mediation of the adenylylcyclase signalling system since the hormone-dependent Ca2+ influx is abolished by specific inhibitors of adenylylcyclase and protein kinase A and mimicked by forskolin and dibutyryl cAMP. 1,25(OH)2D3-stimulated elevations in cellular cAMP paralleled increases in Ca2+ uptake, further suggesting a coupling of adenylylcyclase activation and calcium influx. Fluoride and GTP gamma S mimicked 1,25(OH)2D3-stimulation of calcium influx while GDP beta S suppressed the effect of the hormone. Cholera toxin and Bordetella pertussis toxin both increased 45Ca2+ uptake in rat and chick myoblasts. The hormone further increased cholera toxin actions, but was unable to modify pertussis toxin-induced 45Ca2+ uptake, suggesting a similar target of action for pertussis toxin and 1,25(OH)2D3. Incubation of microsomal membranes with the sterol (10 nM, 2 min) markedly displaces (-32%) [35S]GTP gamma S binding to the membranes. ADP-ribosylation of the pertussis toxin-sensitive 41 kDa substrate was significantly increased (+40%) in 1,25(OH)2D3-pretreated cells. These results suggest that 1,25(OH)2D3-stimulated influx of Ca2+ into rat and embryonic chick cultured myoblasts sequentially requires inhibition of a pertussis toxin-sensitive G protein, accumulation of cAMP and activation of dihydropyridine-sensitive Ca(2+)-channels through PKA-mediated phosphorylation events.
Vazquez
G
G
Depto. Biologia y Bioquímica, Universidad Nacional del Sur, Bahia Blanca, Argentina.
Boland
R
R
de Boland
A R
AR
D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D002117:Calcitriol / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D002478:Cells, Cultured; D002642:Chick Embryo; D000242:Cyclic AMP / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism; D009132:Muscles / Q000378:metabolism*; D051381:Rats; D015290:Second Messenger Systems / Q000187:drug effects
D015220:Calcium Channels; D000242:Cyclic AMP; D019204:GTP-Binding Proteins; D000262:Adenylyl Cyclases; D002117:Calcitriol; D002118:Calcium