Transient PKCα shuttling to the immunological synapse is governed by DGKζ and regulates L-selectin shedding

Considerable evidence indicates that diacylglycerol (DAG) generation at the immunological synapse (IS) determines T cell functions by regulating the duration and amplitude of Ras/ERK signals. The exact mechanism by which DAG regulates Ras/ERK activation downstream of the T cell receptor (TCR) nonetheless remains poorly understood. Here we characterize PKC alpha as a previously unrecognized component of the machinery that translates cell receptor occupancy into Ras/ERK-propagated signals. We show transient translocation of PKC alpha to the IS, mediated by DAG generation at the contact area. Diacylglycerol kinase (DGK)zeta negatively regulated PKC alpha translocation kinetics, whereas PKC alpha activity limited its own persistence at the IS. Coordinated activation of DGK zeta and PKC alpha in response to antigen recognition regulated the amplitude and duration of Ras/ERK activation; this in turn mediated early processes of T cell surface proteolysis such as L-selectin shedding. Analysis of DGK zeta-deficient mice further showed that increased DAG signaling is translated to downstream elements of this pathway, as reflected by enhanced PKC alpha-dependent L-selectin shedding. We propose that early activation of a DAG-PKC alpha axis contributes to the mechanisms by which antigen affinity translates into TCR biological responses.