Diacylglycerol kinase gamma is one of the specific receptors of tumor-promoting phorbol esters

Diacylglycerol kinase (DGK) and protein kinase C (PKC) are two different en zyme families that interact with diacylglycerol. Both enzymes contain cyste ine-rich C1 domains with a zinc finger-like structure. Most of the C1 domai ns of PKCs show strong phorbol-12,13-dibutyrate (PDBu) binding with nanomol ar dissociation constants (K-d'S). However, there has been no experimental evidence that phorbol esters bind to the C1 domains of DGKs. We focused on DGK gamma because its C1A domain has a high degree of sequence homology to those of PKCs, and because DGK gamma translocates from the cytoplasm to the plasma membrane following 12-O-tetradecanoylphorbol-13-acetate treatment s imilar to PKCs. Two C1 domains of DGKy (DGK gamma -C1A and DGK gamma -C1B) were synthesized and tested for their PDBu binding along with whole DGK gam ma (Flag-DGK gamma) expressed in COS-7 cells. DGK gamma -C1A and Flag-DGK g amma showed strong PDBu binding affinity, while DGK gamma -C1B was complete ly inactive. Scatchard analysis of DGK gamma -C1A and Flag-DGK gamma gave K -d'S of 3.1 and 4.4 nM, respectively, indicating that the major PDBu bindin g site of DGKy is C1A. This is the first evidence that DGK gamma is a speci fic receptor of tumor-promoting phorbol esters. (C) 2001 Elsevier Science.