Cellular expression and subcellular localization of diacylglycerol kinase γ in rat brain

Gq protein-coupled receptors lead to activation of phospholipase C, which triggers phosphoinositide signaling. Diacylglycerol (DG) is one of the phosphoinositide metabolites and serves as a second messenger. Diacylglycerol kinase (DGK) phosphorylates DG to produce another second messenger phosphatidic acid. Of the DGK family, DGK gamma is predominantly expressed in the brain at the mRNA level. Recent studies have shown the expression of DGK gamma in vascular endothelial cells and adrenal medullary cells at the protein level, although its detailed cellular expression pattern and subcellular localization in the brain remain to be determined. In the present study, we addressed this point using specific DGK gamma antibody. DGK gamma was expressed in both projection neurons and interneurons in the cerebral cortex, hippocampal formation, and cerebellum. In cerebellar Purkinje cells, DGK gamma was distributed to the soma and dendrites. Fractionation study revealed that DGK gamma was enriched in the internal membranes containing the endoplasmic reticulum and Golgi complex. In immunoelectron microscopy, DGK gamma was localized throughout the smooth endoplasmic reticulum system. These findings suggest that DGK gamma shows unique cellular expression pattern in the brain and distinct subcellular localization different from other DGK isozymes.