title: Hyperactivation of mammalian target of rapamycin (mTOR) signaling by a gain-of-function mutant of the Rheb GTPase.
abstract: Gain-of-function mutants of Ras and Rho family small GTPases have proven to be important tools in analyzing signaling downstream of these small GTPases. The Ras-related GTPase Rheb has emerged as a key player downstream of TSC1-2 in activating signaling to mammalian target of rapamycin (mTOR) effectors of cell growth such as S6K and 4E-BP1. The TSC1-2 tumor suppressor complex has been shown to act as a RhebGAP, converting Rheb from a GTP-bound to a GDP-bound form. Here we report the identification of a mutant Rheb (S16HRheb) that exhibits gain-of-function properties. At endogenous levels of expression S16HRheb exhibits increased GTP loading in vivo and is resistant to TSC1-2 GAP in vitro. Compared with wild-type Rheb, S16HRheb is more active at promoting the phosphorylation of the mTOR effectors S6K1 and 4E-BP1. Thus S16HRheb will help to identify proximal signaling events downstream of Rheb and allow potential Rheb-independent functions downstream of TSC1-2 to be investigated.
authors.affiliation: Institute of Cancer Research, Cancer Research UK Centre of Cell and Molecular Biology, London SW7 6JB, UK.
authors.forename: Lijun
authors.initials: L
authors.lastname: Yan
authors.forename: Greg M
authors.initials: GM
authors.lastname: Findlay
authors.forename: Rebecca
authors.initials: R
authors.lastname: Jones
authors.forename: Julia
authors.initials: J
authors.lastname: Procter
authors.forename: Yunhong
authors.initials: Y
authors.lastname: Cao
authors.forename: Richard F
authors.initials: RF
authors.lastname: Lamb
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D017124:Conserved Sequence; D004789:Enzyme Activation; D020558:GTP Phosphohydrolases / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D007668:Kidney; D008969:Molecular Sequence Data; D020559:Monomeric GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics; D009154:Mutation; D009479:Neuropeptides / Q000737:chemistry / Q000235:genetics; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011494:Protein Kinases / Q000378:metabolism*; D000076205:Ras Homolog Enriched in Brain Protein; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases; D020741:rho GTP-Binding Proteins / Q000235:genetics* / Q000378:metabolism*
chemical_list: D020558:GTP Phosphohydrolases; D006160:Guanosine Triphosphate; D020559:Monomeric GTP-Binding Proteins; D009479:Neuropeptides; D019869:Phosphatidylinositol 3-Kinases; D011494:Protein Kinases; D000076205:Ras Homolog Enriched in Brain Protein; D058570:TOR Serine-Threonine Kinases; D020741:rho GTP-Binding Proteins; C490211:RHEB protein, human; C546842:MTOR protein, human