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Cryo-EM Structure of Saccharomyces cerevisiae Target of Rapamycin Complex 2Cryo-EM Structure of Saccharomyces cerevisiae Target of Rapamycin Complex 2
Structural highlights
Function[AVO2_YEAST] Component of TORC2, which regulates cell cycle-dependent polarization of the actin-cytoskeleton and cell wall integrity. TORC2 controls polarity of the actin cytoskeleton, which is required for orienting the secretory pathway toward discrete growth sites, via the RHO1/PKC1/MAPK cell integrity pathway. [TOR2_YEAST] Phosphatidylinositol 3-kinase homolog, component of both TORC1 and TORC2. TORC1 regulates multiple cellular processes to control cell growth in response to environmental signals. Nutrient limitation and environmental stress signals cause inactivation of TORC1. Active TORC1 positively controls ribosome biogenesis via control of rRNA, ribosomal protein and tRNA gene expression, and rRNA processing. TORC1 positively controls protein biosynthesis by regulation of mRNA stability, translation initiation factor activity, and high-affinity amino acid permeases that serve to provide amino acids for use by the translation machinery. TORC1 also promotes growth by sequestering a number of nutrient and general stress-responsive transcription factors in the cytoplasm. TORC1 negatively controls macroautophagy, a process to recycle surplus cytoplasmic mass under nutrient starvation conditions. TORC1 controls many of these processes via TIP41-TAP42-mediated inhibition of the type 2A-related phosphatases PP2A and SIT4 (PubMed:10198052, PubMed:10329624, PubMed:10604478, PubMed:11741537, PubMed:15620355, PubMed:7606777, PubMed:8741837, PubMed:9539725, PubMed:9843498). In nutrient rich conditions, responsible for the phosphorylation of AGC S6 kinase (S6K) YPK3, activating YPK3 kinase activity and promoting phosphorylation of ribosomal protein S6 (PubMed:25767889). Phosphorylates kinase SCH9 at 6 amino acids in the C-terminus, activating SCH9 kinase activity to properly regulate ribosome biogenesis, translation initiation, and entry into stationary phase (PubMed:17560372). TORC2 regulates cell cycle-dependent polarization of the actin-cytoskeleton, cell wall integrity, and receptor endocytosis. TORC2 controls polarity of the actin cytoskeleton, which is required for orienting the secretory pathway toward discrete growth sites, via the RHO1/PKC1/MAPK cell integrity pathway by activating the RHO1 guanine nucleotide exchange factor ROM2. TORC2 phosphorylates the AGC kinase YPK2, an upstream effector of the cell integrity pathway. TORC2 negatively regulates calcineurin-dependent stress signaling via phosphorylation of its effector SLM1-SLM2 (PubMed:14593073, PubMed:15372071, PubMed:16055732, PubMed:16959779, PubMed:8846782, PubMed:8943012).[1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [LST8_YEAST] Essential component of both TORC1 and TORC2. TORC1 regulates multiple cellular processes to control cell growth in response to environmental signals. Nutrient limitation and environmental stress signals cause inactivation of TORC1. Active TORC1 positively controls ribosome biogenesis via control of rRNA, ribosomal protein and tRNA gene expression, and rRNA processing. TORC1 positively controls protein biosynthesis by regulation of mRNA stability, translation initiation factor activity, and high-affinity amino acid permeases that serve to provide amino acids for use by the translation machinery. TORC1 also promotes growth by sequestering a number of nutrient and general stress-responsive transcription factors in the cytoplasm. TORC1 negatively controls macroautophagy, a process to recycle surplus cytoplasmic mass under nutrient starvation conditions. LST8 is involved in the negative regulation of transcription factors GLN3 and RTG1-RTG3, limiting the synthesis of alpha-ketoglutarate, glutamate and glutamine. LST8 is required for targeting of amino acid permeases (AAPs) to the plasma membrane. TORC2 regulates cell cycle-dependent polarization of the actin-cytoskeleton, cell wall integrity, and receptor endocytosis. TORC2 controls polarity of the actin cytoskeleton, which is required for orienting the secretory pathway toward discrete growth sites, via the RHO1/PKC1/MAPK cell integrity pathway. LST8 is involved in maintenance of cell wall integrity. LST8 modulates TOR2 kinase activity.[18] [19] [20] [AVO1_YEAST] Component of TORC2, which regulates cell cycle-dependent polarization of the actin-cytoskeleton and cell wall integrity. TORC2 controls polarity of the actin cytoskeleton, which is required for orienting the secretory pathway toward discrete growth sites, via the RHO1/PKC1/MAPK cell integrity pathway. Publication Abstract from PubMedThe target of rapamycin (TOR) kinase assembles into two distinct multiprotein complexes, conserved across eukaryote evolution. In contrast to TOR complex 1 (TORC1), TORC2 kinase activity is not inhibited by the macrolide rapamycin. Here, we present the structure of Saccharomyces cerevisiae TORC2 determined by electron cryo-microscopy. TORC2 contains six subunits assembling into a 1.4 MDa rhombohedron. Tor2 and Lst8 form the common core of both TOR complexes. Avo3/Rictor is unique to TORC2, but interacts with the same HEAT repeats of Tor2 that are engaged by Kog1/Raptor in mammalian TORC1, explaining the mutual exclusivity of these two proteins. Density, which we conclude is Avo3, occludes the FKBP12-rapamycin-binding site of Tor2's FRB domain rendering TORC2 rapamycin insensitive and recessing the kinase active site. Although mobile, Avo1/hSin1 further restricts access to the active site as its conserved-region-in-the-middle (CRIM) domain is positioned along an edge of the TORC2 active-site-cleft, consistent with a role for CRIM in substrate recruitment. Cryo-EM structure of Saccharomyces cerevisiae target of rapamycin complex 2.,Karuppasamy M, Kusmider B, Oliveira TM, Gaubitz C, Prouteau M, Loewith R, Schaffitzel C Nat Commun. 2017 Nov 23;8(1):1729. doi: 10.1038/s41467-017-01862-0. PMID:29170376[21] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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