Modulation of the mammalian target of rapamycin pathway by diacylglycerol kinase-produced phosphatidic acid.
The protein known as mammalian target of rapamycin (mTOR) regulates cell growth by integrating different stimuli, such as available nutrients and mitogenic factors. The lipid messenger phosphatidic acid (PA) binds and positively regulates the mitogenic response of mTOR. PA generator enzymes are consequently potential regulators of mTOR. Here we explored the contribution to this pathway of the enzyme diacylglycerol kinase (DGK), which produces PA through phosphorylation of diacylglycerol. We found that overexpression of the DGKzeta, but not of the alpha isoform, in serum-deprived HEK293 cells induced mTOR-dependent phosphorylation of p70S6 kinase (p70S6K). After serum addition, p70S6K phosphorylation was higher and more resistant to rapamycin treatment in cells overexpressing DGKzeta. The effect of this DGK isoform on p70S6K hyperphosphorylation required the mTOR PA binding region. Down-regulation of endogenous DGKzeta by small interfering RNA in HEK293 cells diminished serum-induced p70S6K phosphorylation, highlighting the role of this isoform in the mTOR pathway. Our results confirm a role for PA in mTOR regulation and describe a novel pathway in which DGKzeta-derived PA acts as a mediator of mTOR signaling.
Avila-Flores
Antonia
A
Department of Immunology and Oncology, National Centre for Biotechnology, Consejo Superior de Investigaciones Científicas, Campus Cantoblanco, E-28049 Madrid, Spain.
Santos
Teresa
T
Rincón
Esther
E
Mérida
Isabel
I
D020816:Amino Acid Motifs; D015153:Blotting, Western; D002460:Cell Line; D019852:Diacylglycerol Kinase / Q000378:metabolism*; D015536:Down-Regulation; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006801:Humans; D000860:Hypoxia / Q000378:metabolism; D015151:Immunoblotting; D047908:Intracellular Signaling Peptides and Proteins / Q000378:metabolism; D019169:Jurkat Cells; D050356:Lipid Metabolism; D008565:Membrane Proteins / Q000378:metabolism; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D008954:Models, Biological; D000076250:Myristoylated Alanine-Rich C Kinase Substrate; D010712:Phosphatidic Acids / Q000378:metabolism*; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D020033:Protein Isoforms; D011494:Protein Kinases / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D034741:RNA, Small Interfering / Q000378:metabolism; D038762:Ribosomal Protein S6 Kinases, 70-kDa / Q000378:metabolism; D015398:Signal Transduction; D013347:Subcellular Fractions; D058570:TOR Serine-Threonine Kinases; D013912:Threonine / Q000737:chemistry
D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D010712:Phosphatidic Acids; D020033:Protein Isoforms; D034741:RNA, Small Interfering; D000076250:Myristoylated Alanine-Rich C Kinase Substrate; D049452:Green Fluorescent Proteins; D013912:Threonine; D011494:Protein Kinases; C546842:MTOR protein, human; D019852:Diacylglycerol Kinase; D038762:Ribosomal Protein S6 Kinases, 70-kDa; D058570:TOR Serine-Threonine Kinases