Involvement of protein kinase C in 1,25(OH)2-vitamin D3 regulation of calcium uptake by cultured myocytes.
1,25-Dihydroxyvitamin D3 [1,25(OH)2D3] produces an acute stimulation of calcium influx in cultured chick embryo myocytes through activation of voltage-gated Ca2+ channels and involvement of cyclic AMP-dependent protein kinase A (PKA). To investigate the participation of protein kinase C (PKC) in this hormone-induced response, calcium uptake was measured in myocytes treated with PKC activators 12-O-tetradecanoyl phorbol 13-acetate (TPA, 50 nM) or 1,2-dioctanoyl-rac-glycerol (DOG, 50 microM). TPA and DOG decreased 45Ca2+ uptake 37% below control cultures. Contrarily, the PKC inhibitors H7 and staurosporine increase myocyte Ca2+ uptake 51% and 54%, respectively. In addition, PKC activity was augmented in cytosol (39%) and membranes (31%) of myocytes after 5 min of treatment with 0.1 nM 1,25(OH)2D3. Likewise, the hormone induced a fast biphasic formation of diacylglycerol, the natural PKC activator, peaking at 30 s (26%) and 3 min (39%). On the other hand, the stimulation of Ca2+ uptake induced by compound H7 as well as 1,25(OH)2D3 was completely abolished with a specific PKA inhibitor. H7 also produced an increase in cAMP levels (172%) and PKA activity (204%). These results suggest the participation of PKC in 1,25(OH)2D3 regulated calcium influx in heart cells and the operation of a cross-talk mechanism between the PKC and PKA pathways.
Marinissen
M J
MJ
Departamento de Biologia, Universidad Nacional del Sur, Bahia Blanca, Argentina.
Selles
J
J
Boland
R
R
D000818:Animals; D002117:Calcitriol / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D002642:Chick Embryo; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004075:Diglycerides / Q000494:pharmacology; D006321:Heart / Q000187:drug effects; D009206:Myocardium / Q000166:cytology* / Q000378:metabolism*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D015220:Calcium Channels; D004075:Diglycerides; C044295:1,2-dioctanoylglycerol; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D002117:Calcitriol; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium