Efficient Tor signaling requires a functional class C Vps protein complex in Saccharomyces cerevisiae.
The Tor kinases regulate responses to nutrients and control cell growth. Unlike most organisms that only contain one Tor protein, Saccharomyces cerevisiae expresses two, Tor1 and Tor2, which are thought to share all of the rapamycin-sensitive functions attributable to Tor signaling. Here we conducted a genetic screen that defined the global TOR1 synthetic fitness or lethal interaction gene network. This screen identified mutations in distinctive functional categories that impaired vacuolar function, including components of the EGO/Gse and PAS complexes that reduce fitness. In addition, tor1 is lethal in combination with mutations in class C Vps complex components. We find that Tor1 does not regulate the known function of the class C Vps complex in protein sorting. Instead class C vps mutants fail to recover from rapamycin-induced growth arrest or to survive nitrogen starvation and have low levels of amino acids. Remarkably, addition of glutamate or glutamine restores viability to a tor1 pep3 mutant strain. We conclude that Tor1 is more effective than Tor2 at providing rapamycin-sensitive Tor signaling under conditions of amino acid limitation, and that an intact class C Vps complex is required to mediate intracellular amino acid homeostasis for efficient Tor signaling.
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Related Subject Headings
- Vesicular Transport Proteins
- Signal Transduction
- Saccharomyces cerevisiae Proteins
- Saccharomyces cerevisiae
- Protein Serine-Threonine Kinases
- Phosphotransferases (Alcohol Group Acceptor)
- Phosphatidylinositol 3-Kinases
- Mutation
- Multiprotein Complexes
- Membrane Proteins
Citation
Published In
DOI
ISSN
Publication Date
Volume
Issue
Start / End Page
Location
Related Subject Headings
- Vesicular Transport Proteins
- Signal Transduction
- Saccharomyces cerevisiae Proteins
- Saccharomyces cerevisiae
- Protein Serine-Threonine Kinases
- Phosphotransferases (Alcohol Group Acceptor)
- Phosphatidylinositol 3-Kinases
- Mutation
- Multiprotein Complexes
- Membrane Proteins