Isolation and Expression of an Isoform of Human CDP-Diacylglycerol Synthase cDNA

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Abstract
Phosphatidic acid (PA) is a phospholipid involved in signal transduction and in glycerolipid biosynthesis. CDP-diacylglycerol synthase (CDS) or CTP:phosphatidate cytidylyltransferase (EC 2.7.7.41) catalyzes the conversion of PA to CDP-diacylglycerol (CDP-DAG), an important precursor for the synthesis of phosphatidylinositol, phosphatidylglycerol, and cardiolipin. We describe in this study the isolation and characterization of a human cDNA clone that encodes amino acid sequences homologous to Escherichia coli, yeast, and Drosophila CDS sequences. Expression of this human cDNA under the control of a GAL1 promoter in a null cds1 mutant yeast strain complements its growth defect and produces CDS activity when induced with galactose. Transfection of this cDNA into mammalian cells leads to increased CDS activity in cell-free extracts using an in vitro assay that measures the conversion of [alpha-32P]CTP to [32P]CDP-DAG. This increase in CDS activity also leads to increased secretion of tumor necrosis factor-alpha and interleukin-6 from endothelial ECV304 cells upon stimulation with interleukin-1beta, suggesting that CDS overexpression may amplify cellular signaling responses from cytokines.