Diacylglycerol kinase γ regulates antigen-induced mast cell degranulation by mediating Ca(2+) influxes

Diacylglycerol (DAG) is an important lipid that acts as a signaling messenger during mast cell degranulation after allergen cross-linking of immunoglobulin (Ig) E-bound FcεRI receptors. In this study, we determined the role of diacylglycerol kinase (DGK), which negatively regulates DAG-dependent signaling by converting DAG to phosphatidic acid (PA), in the regulation of mast cell degranulation. Treating RBL (rat basophilic leukemia)-2H3 mast cells with a type I DGK inhibitor significantly reduced antigen-induced degranulation and PA production. Among type I DGK isoforms, we observed that DGKα and DGKγ mRNAs were expressed in RBL-2H3 mast cells using reverse transcription polymerase chain reaction. DGKγ knockdown, but not DGKα, by isoform-specific short hairpin RNAs reduced mast cell degranulation and Ca(2+) influxes from the extracellular environment. These results suggest that DGKγ regulates mast cell degranulation after FcεRI cross-linking through mobilization of intracellular Ca(2+) through Ca(2+) influxes.