Finding new components of the target of rapamycin (TOR) signaling network through chemical genetics and proteome chips.
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.
Huang
Jing
J
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
Zhu
Heng
H
Haggarty
Stephen J
SJ
Spring
David R
DR
Hwang
Heejun
H
Jin
Fulai
F
Snyder
Michael
M
Schreiber
Stuart L
SL
D006801:Humans; D019169:Jurkat Cells; D008954:Models, Biological; D040081:Protein Array Analysis; D011494:Protein Kinases / Q000235:genetics* / Q000378:metabolism*; D040901:Proteomics; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism*; D015398:Signal Transduction; D020123:Sirolimus / Q000494:pharmacology*; D058570:TOR Serine-Threonine Kinases
D029701:Saccharomyces cerevisiae Proteins; D011494:Protein Kinases; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases; D020123:Sirolimus