Diacylglycerol kinase alpha activity promotes survival of CD4+ 8+ double positive cells during thymocyte development.

The diacylglycerol kinases (DGK) form a family of isoenzymes that catalyse the conversion of diacylglycerol (DAG) to phosphatidic acid (PA), both powerful second messengers in the cell. DGKalpha is expressed in brain, peripheral T cells and thymocytes and has been shown to translocate to the nuclear matrix upon T-cell receptor (TCR) engagement. Here, we show that high level expression of DGKalpha is induced following a signal transmitted through the pre-TCR and the protein tyrosine kinase, lck. Activity of DGKalpha contributes to survival in CD4+ 8+ (DP) thymocytes as pharmacological inhibition of DGK activity results in death of this cell population both in cell suspension and thymic explants. DGKalpha promotes survival in these thymocytes through a Bcl-regulated pathway. A consequence of inhibition of DGKalpha is the specific down-regulation of Bcl-xl, whereas in transgenic mice that over-express Bcl-2, death induced by the inhibitor is partially blocked. Thus we report a novel activity of DGKalpha in survival of thymocytes immediately after entry into the DP stage in development.