Farnesylthiosalicylic acid inhibits mammalian target of rapamycin (mTOR) activity both in cells and in vitro by promoting dissociation of the mTOR-raptor complex.
The mammalian target of rapamycin (mTOR) functions with raptor and mLST8 in a signaling complex that controls rates of cell growth and proliferation. Recent results indicate that an inhibitor of the Ras signaling pathway, farnesylthiosalicylic acid (FTS), decreased phosphorylation of the mTOR effectors, PHAS-I and S6K1, in breast cancer cells. Here we show that incubating 293T cells with FTS produced a stable change in mTOR activity that could be measured in immune complex kinase assays using purified PHAS-I as substrate. Similarly, FTS decreased the PHAS-I kinase activity of mTOR when added to cell extracts or to immune complexes containing mTOR. Incubating either cells or extracts with FTS also decreased the amount of raptor that coimmunoprecipitated with mTOR, although having relatively little effect on the amount of mLST8 that coimmunoprecipitated. The concentration effect curves of FTS for inhibition of mTOR activity and for dissociation of the raptor-mTOR complex were almost identical. Caffeine, wortmannin, LY294002, and rapamycin-FKBP12 also markedly inhibited mTOR activity in vitro, but unlike FTS, none of the other mTOR inhibitors appreciably changed the amount of raptor associated with mTOR. Thus, our findings indicate that FTS represents a new type of mTOR inhibitor, which acts by dissociating the functional mTOR-raptor signaling complex.
Department of Pharmacology, P.O. Box 800735, University of Virginia Health System, 1300 Jefferson Park Avenue, Charlottesville, Virginia 22908, USA.
Lloyd P
LP
McMahon
Wei
W
Yue
Richard J
RJ
Santen
John C
JC
Lawrence
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins; D002457:Cell Extracts; D002460:Cell Line; D005204:Farnesol / Q000031:analogs & derivatives* / Q000494:pharmacology*; D006801:Humans; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D000076223:Regulatory-Associated Protein of mTOR; D012459:Salicylates / Q000494:pharmacology*; D058570:TOR Serine-Threonine Kinases
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D002457:Cell Extracts; C087000:EIF4EBP1 protein, human; D010750:Phosphoproteins; D047428:Protein Kinase Inhibitors; D011506:Proteins; C463659:RPTOR protein, human; D000076223:Regulatory-Associated Protein of mTOR; D012459:Salicylates; C093323:farnesylthiosalicylic acid; D005204:Farnesol; D011494:Protein Kinases; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases