2npu
The solution structure of the rapamycin-binding domain of mTOR (FRB)
Structural highlights
FunctionMTOR_HUMAN Serine/threonine protein kinase which is a central regulator of cellular metabolism, growth and survival in response to hormones, growth factors, nutrients, energy and stress signals. Functions as part of 2 structurally and functionally distinct signaling complexes mTORC1 and mTORC2 (mTOR complex 1 and 2). Activated mTORC1 up-regulates protein synthesis by phosphorylating key regulators of mRNA translation and ribosome synthesis. This includes phosphorylation of EIF4EBP1 and release of its inhibition toward the elongation initiation factor 4E (eiF4E). Moreover, phosphorylates and activates RPS6KB1 and RPS6KB2 that promote protein synthesis by modulating the activity of their downstream targets including ribosomal protein S6, eukaryotic translation initiation factor EIF4B and the inhibitor of translation initiation PDCD4. Regulates ribosome synthesis by activating RNA polymerase III-dependent transcription through phosphorylation and inhibition of MAF1 a RNA polymerase III-repressor. In parallel to protein synthesis, also regulates lipid synthesis through SREBF1/SREBP1 and LPIN1. To maintain energy homeostasis mTORC1 may also regulate mitochondrial biogenesis through regulation of PPARGC1A. mTORC1 also negatively regulates autophagy through phosphorylation of ULK1. Under nutrient sufficiency, phosphorylates ULK1 at 'Ser-758', disrupting the interaction with AMPK and preventing activation of ULK1. Also prevents autophagy through phosphorylation of the autophagy inhibitor DAP. mTORC1 exerts a feedback control on upstream growth factor signaling that includes phosphorylation and activation of GRB10 a INSR-dependent signaling suppressor. Among other potential targets mTORC1 may phosphorylate CLIP1 and regulate microtubules. As part of the mTORC2 complex MTOR may regulate other cellular processes including survival and organization of the cytoskeleton. Plays a critical role in the phosphorylation at 'Ser-473' of AKT1, a pro-survival effector of phosphoinositide 3-kinase, facilitating its activation by PDK1. mTORC2 may regulate the actin cytoskeleton, through phosphorylation of PRKCA, PXN and activation of the Rho-type guanine nucleotide exchange factors RHOA and RAC1A or RAC1B. mTORC2 also regulates the phosphorylation of SGK1 at 'Ser-422'.[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe mammalian target of rapamycin (mTOR) is a large, multidomain protein kinase, which plays a central role in the regulation of cell growth and has recently emerged as an essential target of survival signals in many types of human cancer cells. Here, we report the solution structures of complexes formed between the FKBP12-rapamycin binding (FRB) domain of mTOR and phosphatidic acid, an important cellular activator of the kinase, and between the FRB domain and a novel inhibitor (HTS-1). The overall structure of the FRB domain is very similar to that seen in the ternary complex formed with FKBP12 and the immunosuppressive drug rapamycin; however, there are significant changes within the rapamycin-binding site with important consequences for rational drug design. The surface of the FRB domain contains a number of distinctive features that have previously escaped attention, including a potential new regulatory site on the opposite face to that involved in the binding of rapamycin, which displays the features expected for a specific binding site for a small molecule. The interaction sites for phosphatidic acid and HTS-1 were found to closely match the site responsible for rapamycin binding. In addition, the structures determined for the FRB-phosphatidic acid and FRB-HTS-1 complexes revealed a striking similarity between the conformations of buried portions of the ligands and that seen for the rapamycin backbone in contact with the domain. Our findings further highlight the importance of the FRB domain in small molecule-mediated regulation of mTOR, demonstrate the ability to identify novel inhibitors of mTOR that bind tightly to the rapamycin-binding site in the absence of FKBP12, and identify a potential new regulatory site that may be exploited in the design of new anticancer drugs. Structural characterization of the interaction of mTOR with phosphatidic acid and a novel class of inhibitor: compelling evidence for a central role of the FRB domain in small molecule-mediated regulation of mTOR.,Veverka V, Crabbe T, Bird I, Lennie G, Muskett FW, Taylor RJ, Carr MD Oncogene. 2008 Jan 24;27(5):585-95. Epub 2007 Aug 6. PMID:17684489[17] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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