Regulation of T Cell Receptor-induced Activation of the Ras-ERK Pathway by Diacylglycerol Kinase Î

• Published in: The Journal of biological chemistry Vol. 277; no. 34; p. 31089
• Main Authors: Xiao-Ping Zhong, Ehmonie A. Hainey, Benjamin A. Olenchock, Haoran Zhao, Matthew K. Topham, Gary A. Koretzky
• Format: Journal Article
• Language: English
• Published: American Society for Biochemistry and Molecular Biology 23-08-2002
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M203818200

T cell development in the thymus and activation of mature T cells in the periphery depend on signals stimulated by engagement
of the T cell antigen receptor (TCR). Among the second messenger cascades initiated by TCR ligation include the phosphatidylinositol
pathway where the membrane phospholipid, phosphatidylinositol 4,5-bisphosphate, is hydrolyzed to inositol 1,4,5-trisphosphate
and diacylglycerol (DAG). Inositol 1,4,5-trisphosphate signals a rise in intracellular free calcium, leading to translocation
of nuclear factor of activated T cells into the nucleus. DAG activates RasGRP and protein kinase C θ. Because both RasGRP
and protein kinase C θ are essential for thymocyte and T cell function, it is critical to understand how DAG is regulated.
In this report, we demonstrate expression of DAG kinase ζ (DGKζ, the enzyme that catalyzes the conversion of DAG to phosphatidic
acid) in multiple lymphoid organs, with highest expression observed within the T cell compartment. Overexpression studies
in Jurkat T cells indicate that DGKζ interferes with TCR-induced Ras and ERK activation, AP-1 induction, and expression of
the activation marker CD69. In contrast, TCR-stimulated calcium influx is not altered. Mutational analysis indicates that
the kinase and DAG binding domains, but not the ankyrin repeats of DGKζ, are required for its inhibitory effects. Collectively
these studies demonstrate a potential role of DGKζ to function as a selective negative regulator of DAG signaling on T cell
activation and provide the first structure/function analysis of this enzyme in T cells.