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 DGK inhibits PKCalpha activity and that DGK activity is required for this inhibition. We also show that DGKzeta directly interacts with PKCalpha in a signaling complex and that the binding site in DGKzeta is located within the catalytic domain. Because PKCalpha can phosphorylate the myristoylated alanine-rich C-kinase substrate (MARCKS) motif of DGK, we tested whether this modification could affect their interaction. Phosphorylation of this motif significantly attenuated coimmuno-precipitation of DGK and PKCa, and abolished their colocalization in cells, indicating that it negatively regulates binding. Expression of a phosphorylation-mimicking DGKzeta mutant that was unable to bind PKCalpha did not inhibit PKCalpha activity. Together, our results suggest that DGK spatially regulates PKCalpha activity by attenuating local accumulation of signaling DAG. This regulation is impaired by PKCalpha-mediated DGKzeta phosphorylation.