title: Interactions between cyclic AMP-dependent protein phosphorylation and lipid transmethylation reactions in isolated porcine cardiac sarcolemma.
abstract: Premethylation of purified porcine cardiac sarcolemma (SL) in the presence of 0.15, 10 and 150 microM S-adenosyl-L-methionine (AdoMet) did not change the phosphorylation of SL proteins catalyzed either by intrinsic cyclic AMP-dependent protein kinase (cAK) or by added catalytic (C) subunit of this enzyme. On the other hand, membrane exhibited increased lipid methyltransferase activity after preincubation with MgATP and C subunit. Prephosphorylation of membranes stimulated the total [3H]-methyl incorporation into SL lipids assayed at 0.15 microM [3H]AdoMet due to an enhancement of Vmax and without changes in the Km value for AdoMet. Analysis of the methylated lipid products revealed an increased methyl group incorporation into a nonpolar lipid fraction whereas phosphatidylethanolamine-N-methylation was not affected by phosphorylation. The results suggest that the cyclic AMP-mediated signal transduction at the level of cardiac SL is not affected by methylation-induced modifications of the membrane lipid microdomains. On the other hand, an intrinsic SL lipid methyltransferase activity is apparently not related to the N-methylation of phospholipids, is modulated by cyclic AMP-dependent protein phosphorylation.
authors.affiliation: Division of Cardiovascular Sciences, St. Boniface General Hospital Research Centre, Winnipeg, Canada.
authors.forename: R
authors.initials: R
authors.lastname: Vetter
authors.forename: J
authors.initials: J
authors.lastname: Dai
authors.forename: V
authors.initials: V
authors.lastname: Panagia
authors.forename: N S
authors.initials: NS
authors.lastname: Dhalla
mesh_terms: D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D007700:Kinetics; D050356:Lipid Metabolism; D008745:Methylation; D008780:Methyltransferases / Q000378:metabolism*; D009206:Myocardium / Q000201:enzymology*; D011494:Protein Kinases / Q000378:metabolism*; D012436:S-Adenosylmethionine / Q000378:metabolism; D012508:Sarcolemma / Q000201:enzymology* / Q000378:metabolism; D013552:Swine
chemical_list: D012436:S-Adenosylmethionine; D000255:Adenosine Triphosphate; D008780:Methyltransferases; D011494:Protein Kinases