A cascade of protein kinase C isozymes promotes cytoskeletal polarization in T cells

Polarization of the T cell microtubule-organizing center (MTOC) toward the antigen-presenting cell (APC) is driven by the accumulation of diacylglycerol (DAG) at the immunological synapse (IS). The mechanisms that couple DAG to the MTOC are not known. By single-cell photoactivation of the T cell antigen receptor (TCR), we found that three distinct isoforms of protein kinase C (PKC) were recruited by DAG to the IS in two steps. PKC-epsilon and PKC-eta accumulated first in a broad region of membrane, whereas PKC-theta arrived later in a smaller zone. Functional experiments indicated that PKC-theta was required for MTOC reorientation and that PKC-epsilon and PKC-eta operated redundantly to promote the recruitment of PKC-theta and subsequent polarization responses. Our results establish a previously uncharacterized role for PKC proteins in T cell polarity.