Role of cyclic AMP in rat aortic microsomal phosphorylation and calcium uptake.
The role of adenosine 3',5'-monophosphate (cyclic AMP)-dependent membrane phosphorylation in the regulation of microsomal calcium transport in rat aortic smooth muscle was studied. Cyclic AMP-dependent protein kinase augmented the phosphorylation of serine residues in a microsomal protein component with a molecular weight of about 44,000 (determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis) and the majority of 32P incorporation was in serine residue(s). The phosphorylated protein had stability characteristics of a phosphoester. The phosphorylated substrate was not extracted from the trichloroacetic acid (TCA) precipitate with organic solvents or by suspension in hot TCA; and the demonstrated hydroxylamine insensitivity suggested that the substrate was not lipid or nucleic acid. Intrinsic phosphoprotein phosphatase cleaved the labeled phosphate from the cyclic AMP-stimulated microsomes in the first 5 min of incubation. Microsomes phosphorylated in the presence of 1 micron cyclic AMP or 1 micron cyclic AMP plus 0.1 mg/ml protein kinase exhibited enhanced calcium uptake. We suggest that reversible phosphorylation of microsomal membranes may play an important role in the regulation of aortic microsomal calcium transport by cyclic AMP.
D000818:Animals; D001011:Aorta / Q000378:metabolism / Q000648:ultrastructure; D002118:Calcium / Q000378:metabolism*; D000242:Cyclic AMP / Q000502:physiology*; D004591:Electrophoresis, Polyacrylamide Gel; D066298:In Vitro Techniques; D008297:Male; D008861:Microsomes / Q000378:metabolism*; D009130:Muscle, Smooth / Q000378:metabolism* / Q000648:ultrastructure; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D051381:Rats; D013997:Time Factors
D011506:Proteins; D000242:Cyclic AMP; D011494:Protein Kinases; D010749:Phosphoprotein Phosphatases; D002118:Calcium