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Nuclear translocation of Gln3 in response to nutrient signals requires Golgi-to-endosome trafficking in Saccharomyces cerevisiae
Sara A. Zurita-Martinez, and
Maria E. Cardenas*
Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710
Edited by Reed B. Wickner, National Institutes of Health, Bethesda, MD, and approved March 6, 2008
Received for publication February 2, 2008.
The yeast Saccharomyces cerevisiae has developed specializedmechanisms that enable growth on suboptimal nitrogen sources.Exposure of yeast cells to poor nitrogen sources or treatmentwith the Tor kinase inhibitor rapamycin elicits activation ofGln3 and transcription of nitrogen catabolite-repressed (NCR)genes whose products function in scavenging and metabolizingnitrogen. Here, we show that mutations in class C and D Vpscomponents, which mediate Golgi-to-endosome vesicle transport,impair nuclear translocation of Gln3, NCR gene activation, andgrowth in poor nitrogen sources. In nutrient-replete conditions,a significant fraction of Gln3 is peripherally associated withlight membranes and partially colocalizes with Vps10-containingfoci. These results reveal a role for Golgi-to-endosome vesiculartrafficking in TORC1-controlled nuclear translocation of Gln3and support a model in which Tor-mediated signaling in responseto nutrient cues occurs in these compartments. These findingshave important implications for nutrient sensing and growthcontrol via mTor pathways in metazoans.
Key Words: rapamycin action Tor signaling
Author contributions: R.P. and M.E.C. designed research; R.P.,S.A.Z.-M., and M.E.C. performed research; R.P. and S.A.Z.-M.contributed new reagents/analytic tools; R.P., S.A.Z.-M., andM.E.C. analyzed data; and R.P. and M.E.C. wrote the paper.