title: Endolysosomal membrane trafficking complexes drive nutrient-dependent TORC1 signaling to control cell growth in Saccharomyces cerevisiae.
abstract: The rapamycin-sensitive and endomembrane-associated TORC1 pathway controls cell growth in response to nutrients in eukaryotes. Mutations in class C Vps (Vps-C) complexes are synthetically lethal with tor1 mutations and confer rapamycin hypersensitivity in Saccharomyces cerevisiae, suggesting a role for these complexes in TORC1 signaling. Vps-C complexes are required for vesicular trafficking and fusion and comprise four distinct complexes: HOPS and CORVET and their minor intermediaries (i)-CORVET and i-HOPS. We show that at least one Vps-C complex is required to promote TORC1 activity, with the HOPS complex having the greatest input. The vps-c mutants fail to recover from rapamycin-induced growth arrest and show low levels of TORC1 activity. TORC1 promotes cell growth via Sch9, a p70(S6) kinase ortholog. Constitutively active SCH9 or hyperactive TOR1 alleles restored rapamycin recovery and TORC1 activity of vps-c mutants, supporting a role for the Vps-C complexes upstream of TORC1. The EGO GTPase complex Exit from G0 Complex (EGOC) and its homologous Rag-GTPase complex convey amino acid signals to TORC1 in yeast and mammals, respectively. Expression of the activated EGOC GTPase subunits Gtr1(GTP) and Gtr2(GDP) partially suppressed vps-c mutant rapamycin recovery defects, and this suppression was enhanced by increased amino acid concentrations. Moreover, vps-c mutations disrupted EGOC-TORC1 interactions. TORC1 defects were more severe for vps-c mutants than those observed in EGOC mutants. Taken together, our results support a model in which distinct endolysosomal trafficking Vps-C complexes promote rapamycin-sensitive TORC1 activity via multiple inputs, one of which involves maintenance of amino acid homeostasis that is sensed and transmitted to TORC1 via interactions with EGOC.
authors: Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina 27710.
authors: Joanne M
authors: JM
authors: Kingsbury
authors: Neelam D
authors: ND
authors: Sen
authors: Tatsuya
authors: T
authors: Maeda
authors: Joseph
authors: J
authors: Heitman
authors: Maria E
authors: ME
authors: Cardenas
mesh_terms: D000596:Amino Acids / Q000378:metabolism*; D000935:Antifungal Agents / Q000494:pharmacology; D049109:Cell Proliferation / Q000187:drug effects; D009154:Mutation; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000254:growth & development* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D020123:Sirolimus / Q000494:pharmacology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D000596:Amino Acids; D000935:Antifungal Agents; D029701:Saccharomyces cerevisiae Proteins; C561842:TORC1 protein complex, S cerevisiae; D014157:Transcription Factors; D033921:Vesicular Transport Proteins; D020123:Sirolimus
keywords: HOPS; TORC1; amino acid homeostasis; class C Vps complex; rapamycin