title: Ubiquitin-specific peptidase 9, X-linked (USP9X) modulates activity of mammalian target of rapamycin (mTOR).
abstract: The mammalian target of rapamycin (mTOR) is an atypical serine/threonine kinase that responds to extracellular environment to regulate a number of cellular processes. These include cell growth, proliferation, and differentiation. Although both kinase-dependent and -independent functions of mTOR are known to be critical modulators of muscle cell differentiation and regeneration, the signaling mechanisms regulating mTOR activity during differentiation are still unclear. In this study we identify a novel mTOR interacting protein, the ubiquitin-specific protease USP9X, which acts as a negative regulator of mTOR activity and muscle differentiation. USP9X can co-immunoprecipitate mTOR with both Raptor and Rictor, components of mTOR complexes 1 and 2 (mTORC1 and -2), respectively, suggesting that it is present in both mTOR complexes. Knockdown of USP9X leads to increased mTORC1 activity in response to growth factor stimulation. Interestingly, upon initiation of differentiation of C2C12 mouse skeletal myoblasts, knockdown of USP9X increases mTORC2 activity. This increase in mTORC2 activity is accompanied by accelerated differentiation of myoblasts into myotubes. Taken together, our data describe the identification of the deubiquitinase USP9X as a novel mTORC1 and -2 binding partner that negatively regulates mTOR activity and skeletal muscle differentiation.
authors.affiliation: Buck Institute for Research on Aging, Novato, California 94945, USA.
authors.forename: Pooja
authors.initials: P
authors.lastname: Agrawal
authors.forename: Yu-Ting
authors.initials: YT
authors.lastname: Chen
authors.forename: Birgit
authors.initials: B
authors.lastname: Schilling
authors.forename: Bradford W
authors.initials: BW
authors.lastname: Gibson
authors.forename: Robert E
authors.initials: RE
authors.lastname: Hughes
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism; D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002454:Cell Differentiation / Q000502:physiology*; D010450:Endopeptidases / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D000076222:Mechanistic Target of Rapamycin Complex 1; D051379:Mice; D046912:Multiprotein Complexes; D024510:Muscle Development / Q000502:physiology*; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism*; D032448:Myoblasts, Skeletal / Q000166:cytology / Q000378:metabolism*; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D000076226:Rapamycin-Insensitive Companion of mTOR Protein; D000076223:Regulatory-Associated Protein of mTOR; D058570:TOR Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D043222:Ubiquitin Thiolesterase / Q000235:genetics / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C493245:CRTC2 protein, human; D002352:Carrier Proteins; C504923:Crtc2 protein, mouse; D046912:Multiprotein Complexes; D009124:Muscle Proteins; D011506:Proteins; C492571:RICTOR protein, human; C463659:RPTOR protein, human; D000076226:Rapamycin-Insensitive Companion of mTOR Protein; D000076223:Regulatory-Associated Protein of mTOR; C540162:Rptor protein, mouse; D015534:Trans-Activators; D014157:Transcription Factors; C506234:USP9X protein, human; C525637:rictor protein, mouse; C546842:MTOR protein, human; C546843:mTOR protein, mouse; D000076222:Mechanistic Target of Rapamycin Complex 1; D058570:TOR Serine-Threonine Kinases; D010450:Endopeptidases; D043222:Ubiquitin Thiolesterase; C404328:Usp9x protein, mouse