TI - Ceramide -induced apoptosis by translocation , phosphorylation , and activation of protein kinase Cdelta in the Golgi complex . AB - Protein kinase C ( PKC ) , a Ca(2+)/phospholipid -dependent protein kinase , is known as a key enzyme in various cellular responses , including apoptosis . However , the functional role of PKC in apoptosis has not been clarified . In this study , we focused on the involvement of PKCdelta in ceramide -induced apoptosis in HeLa cells and examined the importance of spatiotemporal activation of the specific PKC subtype in apoptotic events . Ceramide -induced apoptosis was inhibited by the PKCdelta-specific inhibitor rottlerin and also was blocked by knockdown of endogenous PKCdelta expression using small interfering RNA . Ceramide induced the translocation of PKCdelta to the Golgi complex and the concomitant activation of PKCdelta via phosphorylation of Tyr(311) and Tyr(332) in the hinge region of the enzyme . Unphosphorylatable PKCdelta ( mutants Y311F and Y332F ) could translocate to the Golgi complex in response to ceramide , suggesting that tyrosine phosphorylation is not necessary for translocation . However , ceramide failed to activate PKCdelta lacking the C1B domain , which did not translocate to the Golgi complex , but could be activated by tyrosine phosphorylation . These findings suggest that ceramide translocates PKCdelta to the Golgi complex and that PKCdelta is activated by tyrosine phosphorylation in the compartment . Furthermore , we utilized species-specific knockdown of PKCdelta by small interfering RNA to study the significance of phosphorylation of Tyr(311) and Tyr(332) in PKCdelta for ceramide -induced apoptosis and found that phosphorylation of Tyr(311) and Tyr(332) is indispensable for ceramide -induced apoptosis . We demonstrate here that the targeting mechanism of PKCdelta , dual regulation of both its activation and translocation to the Golgi complex , is critical for the ceramide -induced apoptotic event .