Diacylglycerol kinase zeta regulates Ras activation by a novel mechanism.
Guanine nucleotide exchange factors (GEFs) activate Ras by facilitating its GTP binding. Ras guanyl nucleotide-releasing protein (GRP) was recently identified as a Ras GEF that has a diacylglycerol (DAG)-binding C1 domain. Its exchange factor activity is regulated by local availability of signaling DAG. DAG kinases (DGKs) metabolize DAG by converting it to phosphatidic acid. Because they can attenuate local accumulation of signaling DAG, DGKs may regulate RasGRP activity and, consequently, activation of Ras. DGK zeta, but not other DGKs, completely eliminated Ras activation induced by RasGRP, and DGK activity was required for this mechanism. DGK zeta also coimmunoprecipitated and colocalized with RasGRP, indicating that these proteins associate in a signaling complex. Coimmunoprecipitation of DGK zeta and RasGRP was enhanced in the presence of phorbol esters, which are DAG analogues that cannot be metabolized by DGKs, suggesting that DAG signaling can induce their interaction. Finally, overexpression of kinase-dead DGK zeta in Jurkat cells prolonged Ras activation after ligation of the T cell receptor. Thus, we have identified a novel way to regulate Ras activation: through DGK zeta, which controls local accumulation of DAG that would otherwise activate RasGRP.
Topham
M K
MK
The Huntsman Cancer Institute and Department of Internal Medicine, University of Utah, Salt Lake City, Utah 84112, USA.
Prescott
S M
SM
D000199:Actins / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019852:Diacylglycerol Kinase / Q000378:metabolism*; D004075:Diglycerides / Q000378:metabolism; D017930:Genes, Reporter; D011905:Genes, ras; D020662:Guanine Nucleotide Exchange Factors; D006801:Humans; D019169:Jurkat Cells; D008856:Microscopy, Fluorescence; D011233:Precipitin Tests; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014162:Transfection; D014407:Tumor Cells, Cultured; D018631:ras Proteins / Q000378:metabolism*
D000199:Actins; D004268:DNA-Binding Proteins; D004075:Diglycerides; D020662:Guanine Nucleotide Exchange Factors; C491790:RASGRP1 protein, human; D011993:Recombinant Fusion Proteins; D019852:Diacylglycerol Kinase; D011493:Protein Kinase C; D018631:ras Proteins; D013755:Tetradecanoylphorbol Acetate