Diacylglycerol kinase ζ limits the polarized recruitment of diacylglycerol-enriched organelles to the immune synapse in T cells

The antigen-induced formation of an immune synapse (IS) between T cells and antigen-presenting cells results in the rapid generation of the lipid second messenger diacylglycerol (DAG) in T cells. Diacylglycerol kinase zeta (DGK zeta) converts DAG into phosphatidic acid (PA). Cytotoxic T lymphocytes (CTLs) from mice deficient in DGK zeta have enhanced antiviral and antitumor activities, indicating that the amount of DAG controls the effectiveness of the T cell response. We characterized the second C1 domain of protein kinase C theta (PKC theta), a DAG-binding protein that is specifically recruited to the IS, as a biological sensor to observe the generation of a DAG gradient during IS formation. In experiments with transgenic mouse CTLs expressing the OT-I T cell receptor (TCR), we showed that both strong and weak interactions between antigen and the TCR led to the rapid generation of DAG, whereas only strong interactions induced the movement of DAG-enriched organelles toward the IS. In DGK zeta-deficient CTLs, antigen stimulation led to the enhanced accumulation of DAG-containing organelles at the IS; however, impaired activation of the PA effector PKC zeta resulted in lack of reorientation of the microtubule-organizing center toward the IS, a process needed for effective T cell activation. Together, these data suggest that the activation of DGK zeta downstream of antigen recognition provides a mechanism that ensures the activation of PA-dependent signaling as a direct result of the strength of TCR-dependent DAG mobilization.