CLONING OF CDP-DIACYLGLYCEROL SYNTHASE FROM A HUMAN NEURONAL CELL-LINE

A critical step in the supply of substrate for the phosphoinositide si gnal transduction pathway is the formation of the liponucleotide inter mediate, CDP-diacylglycerol, catalyzed by CDP-diacylglycerol synthase. Further insight into the regulation of phosphoinositide biosynthesis was sought by cloning of the gene for the vertebrate enzyme. Sequence of the corresponding gene from Drosophila was used to prepare a probe for screening of a human neuronal cell cDNA library. A cDNA was isolat ed with a predicted open reading frame of 1,332 bases, encoding a prot ein of 51 kDa. The amino acid sequence showed 50% identity (75% simila rity) to that of Drosophila eye CDP-diacylglycerol synthase and substa ntial similarity to the Saccharomyces cerevisiae and Escherichia coli homologues. Northern blot analysis, with human cDNA riboprobes, sugges ted that the corresponding mRNA was expressed in all human tissues exa mined. Expression of the human cDNA in COS cells resulted in a more th an fourfold increase in CDP-diacylglycerol synthase activity. Knowledg e of the sequence of vertebrate CDP-diacylglycerol synthase should fac ilitate further investigations into its regulation and the possible ex istence of distinct isoforms.