title: Rapamycin activates Tap42-associated phosphatases by abrogating their association with Tor complex 1.
abstract: In Saccharomyces cerevisiae, the Tap42-phosphatase complexes are major targets of the Tor kinases in the rapamycin-sensitive signaling pathway. The immunosuppressive agent, rapamycin, induces a prompt activation of the Tap42-associated phosphatases, which is vitally important in Tor-mediated transcriptional regulation. However, the mechanism for the rapid phosphatase activation is poorly understood. In this study, we show that the Tap42-phosphatase complexes exist mainly on membrane structures through their association with Tor complex 1 (TORC1). Rapamycin abrogates this association and releases the Tap42-phosphatase complexes into the cytosol. Disassembly of the Tap42-phosphatase complexes occurs subsequently, following the release but at a much slower rate, presumably caused by Tap42 dephosphorylation. Release of the Tap42-phosphatase complexes from membrane structures also occurs when cells are deprived of nutrient. These findings suggest that the association of the Tap42-phosphatase complexes with TORC1 represents an important mechanism by which nutrient controls Tor signaling activity. In addition, our data support a model in which rapamycin acts not by inhibiting the kinase activity of Tor but by disrupting its interaction with downstream targets.
authors.affiliation: Department of Pharmacology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA.
authors.forename: Gonghong
authors.initials: G
authors.lastname: Yan
authors.forename: Xiaoyun
authors.initials: X
authors.lastname: Shen
authors.forename: Yu
authors.initials: Y
authors.lastname: Jiang
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D002462:Cell Membrane / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D047468:Immunoprecipitation; D008954:Models, Biological; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects; D020123:Sirolimus / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D019869:Phosphatidylinositol 3-Kinases; D010744:Phosphoric Monoester Hydrolases; D017853:Phosphotransferases (Alcohol Group Acceptor); D029701:Saccharomyces cerevisiae Proteins; D020123:Sirolimus; C100984:TAP42 protein, S cerevisiae; C083324:TOR1 protein, S cerevisiae