title: beta-Adrenergic receptor agonists increase phospholipid methylation, membrane fluidity, and beta-adrenergic receptor-adenylate cyclase coupling.
abstract: The beta-adrenergic agonist L-isoproterenol stimulated the enzymic synthesis of phosphatidyl-N-monomethylethanolamine and phosphatidylcholine in rat reticulocyte ghosts containing the methyl donor S-adenosyl-L-methionine. The stimulation was stereospecific, dose-dependent, and inhibited by the beta-adrenergic agonist propranolol. The addition of GTP inside the resealed ghosts shifted the dose-response of phospholipid methylation by L-isoproterenol to the left by 2 orders of magnitude. Direct stimulation of adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] with sodium fluoride or cholera toxin did not increase the methylation of phospholipids. At a concentration of S-adenosyl-L-methionine that stimulates synthesis of phosphatidyl-N-monomethylethanolamine, the activity of isoproterenol-sensitive adenylate cyclase was increased 2-fold without changes in the basal activity of adenylate cyclase and the number of beta-adrenergic receptors. The increase of phospholipid methylation by L-isoproterenol decreased membrane viscosity and increased translocation of methylated lipids. These findings indicate that enhancement of phospholipid methylation by L-isoproterenol decreases membrane microviscosity and thus increases lateral movement of the beta-adrenergic receptors and coupling with adenylate cyclase.
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism*; D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D008297:Male; D008560:Membrane Fluidity / Q000187:drug effects*; D008563:Membrane Lipids / Q000378:metabolism; D008745:Methylation; D010743:Phospholipids / Q000378:metabolism*; D011485:Protein Binding; D051381:Rats; D011941:Receptors, Adrenergic / Q000378:metabolism*; D011943:Receptors, Adrenergic, beta / Q000378:metabolism*; D012156:Reticulocytes / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D000318:Adrenergic beta-Agonists; D008563:Membrane Lipids; D010743:Phospholipids; D011941:Receptors, Adrenergic; D011943:Receptors, Adrenergic, beta; D000262:Adenylyl Cyclases