title: mTOR kinase domain phosphorylation promotes mTORC1 signaling, cell growth, and cell cycle progression.
abstract: The mammalian target of rapamycin complex 1 (mTORC1) functions as an environmental sensor to promote critical cellular processes such as protein synthesis, cell growth, and cell proliferation in response to growth factors and nutrients. While diverse stimuli regulate mTORC1 signaling, the direct molecular mechanisms by which mTORC1 senses and responds to these signals remain poorly defined. Here we investigated the role of mTOR phosphorylation in mTORC1 function. By employing mass spectrometry and phospho-specific antibodies, we demonstrated novel phosphorylation on S2159 and T2164 within the mTOR kinase domain. Mutational analysis of these phosphorylation sites indicates that dual S2159/T2164 phosphorylation cooperatively promotes mTORC1 signaling to S6K1 and 4EBP1. Mechanistically, S2159/T2164 phosphorylation modulates the mTOR-raptor and raptor-PRAS40 interactions and augments mTORC1-associated mTOR S2481 autophosphorylation. Moreover, mTOR S2159/T2164 phosphorylation promotes cell growth and cell cycle progression. We propose a model whereby mTOR kinase domain phosphorylation modulates the interaction of mTOR with regulatory partner proteins and augments intrinsic mTORC1 kinase activity to promote biochemical signaling, cell growth, and cell cycle progression.
authors.affiliation: Department of Cell and Developmental Biology, Division of Metabolism, Endocrinology, and Diabetes, 109 Zina Pitcher Place, University of Michigan Medical School, Ann Arbor, MI 48109-2200, USA.
authors.forename: Bilgen
authors.initials: B
authors.lastname: Ekim
authors.forename: Brian
authors.initials: B
authors.lastname: Magnuson
authors.forename: Hugo A
authors.initials: HA
authors.lastname: Acosta-Jaquez
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Keller
authors.forename: Edward P
authors.initials: EP
authors.lastname: Feener
authors.forename: Diane C
authors.initials: DC
authors.lastname: Fingar
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D045163:Antibodies, Phospho-Specific / Q000378:metabolism; D002453:Cell Cycle / Q000502:physiology*; D049109:Cell Proliferation; D057809:HEK293 Cells; D006801:Humans; D013058:Mass Spectrometry / Q000379:methods; D000076222:Mechanistic Target of Rapamycin Complex 1; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes; D016297:Mutagenesis, Site-Directed; D010766:Phosphorylation; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D000076223:Regulatory-Associated Protein of mTOR; D016415:Sequence Alignment; D015398:Signal Transduction / Q000502:physiology*; D058570:TOR Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D045163:Antibodies, Phospho-Specific; D046912:Multiprotein Complexes; D011506:Proteins; C463659:RPTOR protein, human; D000076223:Regulatory-Associated Protein of mTOR; C546842:MTOR protein, human; D000076222:Mechanistic Target of Rapamycin Complex 1; D058570:TOR Serine-Threonine Kinases