TOR Complexes and the Maintenance of Cellular Homeostasis. Issue 2 (February 2016)

• Record Type: Journal Article
• Authors: Eltschinger, Sandra; Loewith, Robbie
• Is Part Of: Trends in cell biology. Volume 26:Issue 2(2016)
• Page Start: 148
• Page End: 159
• Publication Date: 2016-02
• Subjects: Target Of Rapamycin (TOR) -- growth -- homeostasis -- osmotic control -- sphingolipid -- eisosome -- membrane tension; Cytology -- Periodicals; Cytology -- Research -- Periodicals; 571.6
• DOI: 10.1016/j.tcb.2015.10.003
• Languages: English
• ISSNs: 0962-8924

Abstract

Abstract : The Target of Rapamycin (TOR) is a conserved serine/threonine (ser/thr) kinase that functions in two, distinct, multiprotein complexes called TORC1 and TORC2. Each complex regulates different aspects of eukaryote growth: TORC1 regulates cell volume and/or mass by influencing protein synthesis and turnover, while TORC2, as detailed in this review, regulates cell surface area by influencing lipid production and intracellular turgor. TOR complexes function in feedback loops, implying that downstream effectors are also likely to be involved in upstream regulation. In this regard, the notion that TORCs function primarily as mediators of cellular and organismal homeostasis is fundamentally different from the current, predominate view of TOR as a direct transducer of extracellular biotic and abiotic signals. Trends: The Target of Rapamycin (TOR) is an atypical ser/thr protein kinase that functions in distinct multiprotein complexes named TORC1 and TORC2. These complexes are widely conserved and regulate various aspects of growth in response to a plethora of environmental cues. However, recent reports demonstrate that TORC effectors can also function as upstream regulators, suggesting that these complexes function in homeostatic feedback loops. Yeast and mammalian TORC1 function upstream and downstream of protein synthesis and turnover to maintain homeostasis of cell volume. Yeast TORC2 functions upstream and downstream of membrane tension to maintain homeostasis of cell surface area. This signaling architecture implies that additional TORC regulators will be found among newly identified TORC effectors.