mTOR phosphorylated at S2448 binds to raptor and rictor.
In mammalian cells, the mammalian target of rapamycin (mTOR) forms an enzyme complex with raptor (together with other proteins) named mTOR complex 1 (mTORC1), of which a major target is the p70 ribosomal protein S6 kinase (p70S6K). A second enzyme complex, mTOR complex 2 (mTORC2), contains mTOR and rictor and regulates the Akt kinase. Both mTORC1 and mTORC2 are regulated by phosphorylation, complex formation and localization. So far, the role of p70S6K-mediated mTOR S2448 phosphorylation has not been investigated in detail. Here, we report that endogenous mTOR phosphorylated at S2448 binds to both, raptor and rictor. Experiments with chemical inhibitors of the mTOR kinase and of the phosphatidylinositol-3-kinase revealed that downregulation of mTOR S2448 phosphorylation correlates with decreased mTORC1 activity but can occur decoupled of effects on mTORC2 activity. In addition, we found that the correlation of the mTOR S2448 phosphorylation status with mTORC1 activity is not a consequence of effects on the assembly of mTOR protein and raptor. Our data allow new insights into the role of mTOR phosphorylation for the regulation of its kinase activity.
Rosner
M
M
Medical Genetics, Medical University of Vienna, Währinger Gürtel 18-20, 1090, Vienna, Austria.
Siegel
N
N
Valli
A
A
Fuchs
C
C
Hengstschläger
M
M
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000076222:Mechanistic Target of Rapamycin Complex 1; D046912:Multiprotein Complexes; D010766:Phosphorylation; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D000076226:Rapamycin-Insensitive Companion of mTOR Protein; D000076223:Regulatory-Associated Protein of mTOR; D012694:Serine / Q000378:metabolism*; D058570:TOR Serine-Threonine Kinases; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; C493245:CRTC2 protein, human; D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D046912:Multiprotein Complexes; D011506:Proteins; C492571:RICTOR protein, human; C463659:RPTOR protein, human; D000076226:Rapamycin-Insensitive Companion of mTOR Protein; D000076223:Regulatory-Associated Protein of mTOR; D014157:Transcription Factors; D012694:Serine; C546842:MTOR protein, human; D000076222:Mechanistic Target of Rapamycin Complex 1; D017346:Protein Serine-Threonine Kinases; D058570:TOR Serine-Threonine Kinases