Association of diacylglycerol kinase ζ with protein kinase C α : spatial regulation of diacylglycerol signaling

Activation of PKC depends on the availability of DAG, a signaling lipid that is tightly and dynamically regulated. DAG kinase (DGK) terminates DAG signaling by converting it to phosphatidic acid. Here, we demonstrate that DGKζ inhibits PKCα activity and that DGK activity is required for this inhibition. We also show that DGKζ directly interacts with PKCα in a signaling complex and that the binding site in DGKζ is located within the catalytic domain. Because PKCα can phosphorylate the myristoylated alanine-rich C-kinase substrate (MARCKS) motif of DGKζ, we tested whether this modification could affect their interaction. Phosphorylation of this motif significantly attenuated coimmunoprecipitation of DGKζ and PKCα and abolished their colocalization in cells, indicating that it negatively regulates binding. Expression of a phosphorylation-mimicking DGKζ mutant that was unable to bind PKCα did not inhibit PKCα activity. Together, our results suggest that DGKζ spatially regulates PKCα activity by attenuating local accumulation of signaling DAG. This regulation is impaired by PKCα-mediated DGKζ phosphorylation.