Benzodiazepine and beta-adrenergic receptor ligands independently stimulate phospholipid methylation
Strittmatter, W.J.; Hirata, F.; Axelrod, J.; Mallorga, P.; Tallman, J.F.; Henneberry, R.C.
Nature 282(5741): 857-859
1979
ISSN/ISBN: 0028-0836 PMID: 42020 Document Number: 149229
The stepwise methylation of phosphatidylethanolamine by two methyltransferase synthesises phosphatidylcholine in membranes1. Although the CDP-choline pathway is the major route for phosphatidylcholine synthesis, recent work in our laboratory has found that the methylation pathway is metabolically highly active. The phospholipid methyltransferases, their substrates and their products are asymmetrically distributed in the cell membrane. Methyltransferase I, located on the cytoplasmic side of the membrane, transfers a methyl group from S-adenosylmethionine to phosphatidylethanolamine to form phosphatidyl-N-monomethylethanolamine. Methyltransferase II, on the exterior surface of the bilayer, catalyses two additional N-methylations to form phosphatidylcholine. The asymmetric distribution of methyltransferases results in the synthesis and translocation of phosphatidylcholine to the exterior bilayer surface2. The synthesis and translocation of methylated phos-pholipid affects many membrane events, such as fluidity3, coupling of the β-adrenergic receptor with adenylate cyclase4, the number of β-adrenergic receptors5, Ca2+-ATPase activity6, leukocyte chemotaxis7, mast cell histamine secretion8 and lymphocyte mitogenesis9. We now report that stimulation of a benzodiazepine receptor with anti-anxiety benzodiazepines, and stimulation of the β-adrenergic receptor with β-agonists, increase phospholipid methylation in C6 astrocytoma cells. Furthermore, simultaneous addition of benzodiazepine and β-adrenergic agonists increases methylation in an additive manner.