Studies suggesting the participation of protein kinase A in 1, 25(OH)2-vitamin D3-dependent protein phosphorylation in cardiac muscle.
We have previously established that the secosteroid hormone 1alpha, 25-dihydroxy-vitamin D3 [1,25(OH)2D 3] rapidly stimulates dihydropyridine-sensitive calcium channel-mediated Ca2+ influx in chick cardiac muscle by a non-genomic action which is accompanied by phosphorylation of microsomal proteins. In the present study, we investigated the participation of the cyclic AMP/protein kinase A (PKA) signalling pathway in hormone-induced changes on protein phosphorylation in chick heart tissue. A major increase in the phosphorylation of a microsomal protein of 45 kDa, and, to a lesser extent, of a protein of 70 kDa, was observed after incubation with [gamma-32P]ATP of membranes isolated from heart thin slices (HTS) pretreated for 1-5 min with 1,25(OH)2D3. This effect was dose- and time-dependent, reaching a maximum after 3 min and at the physiological concentrations of 10(-10) and 10(-11) M. 1,25(OH)2D3 steadily increased cellular cAMP levels as a function of the dose (10( -12)-10(-9) M). The specific agonist of PKA, Sp-cAMPS and the PKA catalytic subunit stimulated the phosphorylation of the same membrane proteins as the hormone. The 1alpha,25-dihydroxy-vitamin D3-dependent changes in microsomal protein phosphorylation were diminished by the specific PKA inhibitor, Rp-cAMPS. In addition, the PKA activity ratio (-cAMP/+cAMP) increased 60% above the control after treatment of HTS with 10(-11) M 1,25(OH)2D3. The data obtained clearly indicate that activation of the cAMP/PKA signalling pathway mediates the stimulation of protein phosphorylation by 1alpha, 25-dihydroxy-vitamin D3 in chick cardiac muscle.
Santillán
G E
GE
Departamento de Biología, Bioquímica y Farmacia, Universidad Nacional del Sur, (8000) Bahía Blanca, Argentina.
Boland
R L
RL
D000818:Animals; D002117:Calcitriol / Q000378:metabolism* / Q000494:pharmacology; D002645:Chickens; D000242:Cyclic AMP / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism*; D006321:Heart / Q000187:drug effects; D066298:In Vitro Techniques; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism; D009124:Muscle Proteins / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism*; D010766:Phosphorylation; D015398:Signal Transduction
D009124:Muscle Proteins; D000242:Cyclic AMP; D017868:Cyclic AMP-Dependent Protein Kinases; D002117:Calcitriol