Howard Hughes Medical Institute, Harvard Institute of Chemistry and Cell Biology, and Department of Chemistry and Chemical Biology, Harvard University, Cambridge, MA 02138, USA- jinghuang@mednet-ucla-edu
Abstract: The TOR -target of rapamycin- proteins play important roles in nutrient signaling in eukaryotic cells- Rapamycin treatment induces a state reminiscent of the nutrient starvation response, often resulting in growth inhibition- Using a chemical genetic modifier screen, we identified two classes of small molecules, small-molecule inhibitors of rapamycin -SMIRs- and small-molecule enhancers of rapamycin -SMERs-, that suppress and augment, respectively, rapamycin's effect in the yeast Saccharomyces cerevisiae- Probing proteome chips with biotinylated SMIRs revealed putative intracellular target proteins, including Tep1p, a homolog of the mammalian PTEN -phosphatase and tensin homologue deleted on chromosome 10- tumor suppressor, and Ybr077cp -Nir1p-, a protein of previously unknown function that we show to be a component of the TOR signaling network- Both SMIR target proteins are associated with PI-3,4-P2, suggesting a mechanism of regulation of the TOR pathway involving phosphatidylinositides- Our results illustrate the combined use of chemical genetics and proteomics in biological discovery and map a path for creating useful therapeutics for treating human diseases involving the TOR pathway, such as diabetes and cancer-