Expression of mRNAs for the diacylglycerol kinase family in immune cells during an inflammatory reaction

Abstract

Phosphoinositide metabolism is intimately involved in cellular signal transduction. In response to extracellular stimuli, it generates diacylglycerol (DG), which serves as a lipid second messenger molecule to activate various proteins in various organs under pathophysiological conditions. Diacylglycerol kinase (DGK) constitutes an enzyme family that catalyzes conversion of DG to phosphatidic acid. It is therefore regarded as a regulator of the DG signal. Previous studies have revealed the critical role of α and ζ types of DGK in T cell functions. Nevertheless, little is known about the expression patterns of the DGK family in immune cells of various kinds. After examination of the expression profile of DGK isozymes in immune cells that are isolated from human blood, we investigated whether their mRNA expression levels would be changed during an inflammatory reaction. Results showed that DGK isozyme mRNAs are widely expressed in immune cells, except for DGKβ and DGKι. During an inflammatory reaction, DGKε mRNA was increased transiently in the initial phase (20-40 min) of stimulation with both LPS and IL-2 in T cellderived HUT-102 cells and macrophage-derived RAW264 cells. At the organismal level, an intraperitoneal injection of LPS also induced upregulation of DGKε mRNA in the spleen in a similar, but not identical, manner. These results suggest that DGKε is involved in inflammatory processes of the cellular immune system.