title: TOR mutations confer rapamycin resistance by preventing interaction with FKBP12-rapamycin.
abstract: The antifungal, immunosuppressive compound rapamycin arrests the cell cycle in G1 in both yeast cells and T-lymphocytes. Previous genetic studies in yeast identified mutations in three genes, FPR1 (FKBP12), TOR1, and TOR2, which confer rapamycin resistance, and genetic findings implicated the TOR proteins as direct targets of FKBP12-rapamycin. Consistent with this model, we find that modulating TOR1 and TOR2 expression alters rapamycin sensitivity. We describe several TOR2 mutations that confer rapamycin resistance. These mutations prevent FKBP12-rapamycin binding to TOR2, as assayed with the two-hybrid system. We find that TOR1 and the mammalian TOR homologue (mTOR) also bind FKBP12-rapamycin, and mutations corresponding to those in TOR2 similarly block FKBP12-rapamycin binding. We demonstrate that FKBP12 prolyl isomerase activity is not required for FKBP12-rapamycin binding to TOR and that a composite protein-drug surface contacts the TOR proteins. These studies confirm that the TOR proteins are direct targets of FKBP12-rapamycin, reveal that drug-resistant mutations prevent this association, and define structural features of these complexes.
mesh_terms: D000483:Alleles; D000935:Antifungal Agents / Q000378:metabolism* / Q000494:pharmacology; D001483:Base Sequence; D002352:Carrier Proteins / Q000378:metabolism*; D018797:Cell Cycle Proteins; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004352:Drug Resistance, Microbial / Q000235:genetics*; D005656:Fungal Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D005800:Genes, Fungal; D006360:Heat-Shock Proteins / Q000378:metabolism*; D007700:Kinetics; D008969:Molecular Sequence Data; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D011090:Polyenes / Q000378:metabolism* / Q000494:pharmacology*; D016133:Polymerase Chain Reaction; D011485:Protein Binding; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D020123:Sirolimus; D022021:Tacrolimus Binding Proteins
chemical_list: D000935:Antifungal Agents; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D017931:DNA Primers; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D006360:Heat-Shock Proteins; D019869:Phosphatidylinositol 3-Kinases; D017853:Phosphotransferases (Alcohol Group Acceptor); D011090:Polyenes; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; D020123:Sirolimus; D022021:Tacrolimus Binding Proteins; C083324:TOR1 protein, S cerevisiae; C081135:TOR2 protein, S cerevisiae