title: Molecular basis of the acceleration of the GDP-GTP exchange of human ras homolog enriched in brain by human translationally controlled tumor protein.
abstract: Ras homolog enriched in brain (Rheb), a small GTPase, positively regulates the mTORC1 pathway. The GDP-GTP exchange of Rheb has been suggested to be facilitated by translationally controlled tumor protein (TCTP). Here we demonstrate that human TCTP (hTCTP) interacts with human Rheb (hRheb) and accelerates its GDP release in vitro and that hTCTP activates the mTORC1 pathway in vivo. To investigate the underlying mechanism, we built structure models of GDP- and GTP-bound hRheb in complexes with hTCTP and performed molecular dynamics simulations of the models, which predict key residues involved in the interactions and region of hRheb undergoing conformational change during the GDP-GTP exchange. These results are verified with site-directed mutagenesis and in vitro biochemical and in vivo cell biological analyses. Furthermore, a crystal structure of the E12V mutant hTCTP, which lacks the guanine nucleotide exchange factor activity, shows that the deficiency appears to be caused by loss of a salt-bridging interaction with Lys-45 of hRheb. These data collectively provide insights into the molecular mechanisms of how hTCTP interacts with hRheb and activates the mTORC1 pathway.
authors: State Key Laboratory of Molecular Biology and Research Center for Structural Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, China.
authors: Xianchi
authors: X
authors: Dong
authors: Bei
authors: B
authors: Yang
authors: Yingjie
authors: Y
authors: Li
authors: Chen
authors: C
authors: Zhong
authors: Jianping
authors: J
authors: Ding
mesh_terms: D001665:Binding Sites; D014408:Biomarkers, Tumor / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D006153:Guanosine Diphosphate / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism*; D006801:Humans; D000076222:Mechanistic Target of Rapamycin Complex 1; D008968:Molecular Conformation; D020559:Monomeric GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D046912:Multiprotein Complexes; D009479:Neuropeptides / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D017433:Protein Structure, Secondary; D011506:Proteins; D000076205:Ras Homolog Enriched in Brain Protein; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D000090324:Tumor Protein, Translationally-Controlled 1
chemical_list: D014408:Biomarkers, Tumor; D046912:Multiprotein Complexes; D009479:Neuropeptides; D011506:Proteins; C490211:RHEB protein, human; D000076205:Ras Homolog Enriched in Brain Protein; C000715647:TPT1 protein, human; D014157:Transcription Factors; D000090324:Tumor Protein, Translationally-Controlled 1; D006153:Guanosine Diphosphate; D006160:Guanosine Triphosphate; D000076222:Mechanistic Target of Rapamycin Complex 1; D058570:TOR Serine-Threonine Kinases; D020559:Monomeric GTP-Binding Proteins