Lysophosphatidylethanolamine acyltransferase activity is elevated during cardiac cell differentiation

Abstract

We examined if elevation in lysophosphatidylethanolamine acyltransferase activity was associated with elevation in phosphatidylethanolamine content during differentiation of P19 teratocarcinoma cells into cardiac myocytes. P19 cells were induced to undergo differentiation into cardiac myocytes by the addition of 1% dimethylsulfoxide to the medium. Immunofluorescence microscopy revealed the presence of striated myosin at 8 days post-dimethylsulfoxide addition confirming differentiation into cardiac cells. The content of phosphatidylethanolamine was increased 2.1-fold ( P<0.05) in differentiated cells compared to undifferentiated cells, whereas the content of phosphatidylcholine was reduced 29% ( P<0.05). There were no alterations in the pool sizes of other phospholipids, including cardiolipin. The relative abundance of fatty acids in phospholipids of P19 cells was 18:1>18:0>16:1=18:2>16:0=14:0>20:4 and differentiation did not affect the relative amounts of these fatty acids within individual phospholipids. When cells were incubated with [1,3- 3H]glycerol, radioactivity incorporated into phosphatidylethanolamine was elevated 5.8-fold, whereas radioactivity incorporated into phosphatidylcholine was unaltered. Ethanolaminephosphotransferase, cholinephosphotransferase and membrane CTP:phosphocholine cytidylyltransferase activities were elevated in differentiated cells compared to undifferentiated cells, whereas membrane and cytosolic phospholipase A 2 activities were unaltered. Lysophosphatidylethanolamine acyltransferase activities were elevated 2.4-fold ( P<0.05). Lysophosphatidylcholine acyltransferase, monolysocardiolipin acyltransferase, acyl-Coenzyme A synthetase and acyl-Coenzyme A hydrolase activities were unaltered in differentiated cells compared to undifferentiated cells. We postulate that during cardiac cell differentiation, the observed elevation in lysophosphatidylethanolamine acyltransferase activity accompanies the elevation in phosphatidylethanolamine mass, possibly to maintain the fatty acyl composition of this phospholipid within the membrane.