ISSN 2415-3060 (print), ISSN 2522-4972 (online)
  • 28 of 42
JMBS 2017, 2(4): 155–160

Involvement of the TOR signaling pathway in metabolism regulation of Saccharomyces cerevisiae grown under carbohydrate-limited conditions

Valiskhevich B.V.

The lack of nutrients and energy in the cell is tightly connected with periods of their low or high levels. This forces the switch from anabolism to catabolism and vise versa. One important protein that regulates this switch is a protein kinase TOR (target of rapamycin). TOR signaling pathway is a highly conservative controller of many functions, including the intensity of metabolism and stress resistance in a variety of organisms from yeast to humans. It is known that atypical kinase TOR is a component of a complex signaling system, which normally regulates growth and proliferation of cells. Identification of TOR, as an integral component of РІЗК/АКТ pathway and existence of cross anticancer action between p53 and TOR signaling pathways demonstrate the unique role of TOR kinase during cell growth. In fact, various aspects of TOR kinase regulation are examined. As an example, TOR kinase interaction with the basic cellular signaling cascades makes it a useful target for treatment of cancer, diabetes and obesity. It is known that TOR is a nutrient sensor in the cell, which participates in the regulation of signal transduction in response to nutrients (e.g. proteins and amino acids). However, interplay between substances like carbohydrates, that are a major source of energy and carbon for cell, and TOR-signaling pathway remains poorly studied. Metabolic activity is an indicator of intensity of redox processes in the cell. Since the intracellular redox balance depends on the total metabolic activity of cells, we have studied the metabolic activity in the presence of low concentrations of carbohydrates. In the presence of 0.1% carbohydrates in the yeast cultivation medium, fructose-grown parental strain and single mutants demonstrated metabolic activities lower than respective glucose-grown. It can serve as a confirmation of our assumptions about pre-adaptations of fructose-grown yeast cells to carbonyl/oxidative stress. Also, in most cases this parameter was higher in mutant cells compared with the parental strain. Glucose-6-phosphate dehydrogenase is a key enzyme of pentose phosphate pathway and plays an important role in maintaining proper intracellular pool of reduced coenzyme NADPH. Changes in the enzyme activity can be used as a potential biomarker of carbonyl/oxidative stress. It should also be noted that in most cases cells grown in the medium with fructose had lower activity of the enzyme than those in the presence of glucose. Interestingly, the activity of glucose-6-phosphate in mutant strains was lower compared to the parental strain. That can be explained by the redirection of carbohydrates towards non-enzymatic transformations. Thus, under starvation conditions with fructose all studied strains grew faster than those in the presence of glucose. It can be suggested that fructose as compared to glucose accelerates aging by higher metabolism intensity, generation of reactive oxygen and carbonyl species. The above suggestion is in a good agreement with the fact that the activity of G6PDH was lower in the presence of fructose, resulting in acceleration of non-enzymatic reactions. Calorie restriction (0.1% carbohydrates in the medium) inhibits TOR signaling pathway. Metabolic activity is higher, and the activity of glucose-6-phosphate dehydrogenase is lower in the mutant cells compared with the parental strain. This suggests activating of compensatory mechanisms, including protein Snf1p/AMP, Sch9, PKA, MAP that in some way compensates the lack of TOR signaling pathway.

Keywords: Saccharomyces cerevisiae, glucose, fructose, TOR signaling pathway, carbonyl/oxidative stress

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  1. Homza B, Vasylkovska R, Semchyshyn H. Defekty rehulyatornykh kompleksiv TOR spovilnyuyut starinnya ta rozvytok karbonilnoho/oksydatyvnoho stresu v drizhdzhiv. Sassharomyces cerevisiae. Ukrainskyi biokhimichnyi zhurnal. 2014; 86 (1): 85-92. [Ukrainian].
  2. Lozinska LM, Semchyshyn HM. Biolohichni aspekty neenzymatychnoho hlikozylyuvannya. Ukrainskyi biokhimichnyi zhurnal. 2012; 84 (5): 16–37. [Ukrainian].
  3. Lozinska LM, Semchyshyn HM. Fruktoza yak faktor rozvytku karb1onilnoho i oksydatyvnoho stresiv ta pryskorenoho starinnya drizhdzhiv Saccharomyces cerevisiae. Ukrainskyi biokhimichnyi zhurnal. 2011; 83 (4): 67–76. [Ukrainian].
  4. Lushchak VI, Bahnyukova TV, Lushchak OV. Pokaznyky oksydatyvnoho stresu. 1. Tiobarbituratatyvni produkty i karbonilni hrupy bilkiv. Ukrainskyi biokhimichnyi zhurnal. 2004; 76 (3): 136–41. [Ukrainian].
  5. Beck T, Hall MN. The TOR signalling pathway controls nuclear localization of nutrient-regulated transcription factors. Nature. 1999; 402: 689–92.
  6. Bisson LF, Fraenkel DG. Involvement of kinases in glucose and fructose uptake by Saccharomyces cerevisiae. Proc Natl Acad Sci USA. 1983; 1730–4.
  7. Wanke V., Cameroni E., Uotila A, Piccolis M, Urban J, Loewith R, De Virgilio C. Caffeine extends yeast lifespan by targeting TORC1. Mol Microbiol. 2008 Jul; 69 (1): 277–85.
  8. Kliegman JI, Fiedler D, Ryan CJ, Xu Yi-Fan, Su Xiao-yang, Thomas D, Caccese MC, et al. Chemical genetics of rapamycin-insensitive TORC2 in S. cerevisiae. Cell Rep. 2013; 5 (6): 1725-36.
  9. Lushchak V, Semchyshyn H, Lushchak O, Mandryk S. Diethyldithiocarbamate inhibits in vivo Cu,Zn-superoxide dismutase and perturbs free radical processes in the yeast Saccharomyces cerevisiae cells. Biochem Biophys Res Commun. 2005; 338: 1739–44.
  10. Valishkevych BV, Vasylkovska RA, Lozinska LM, Semchyshyn HM. Fructose-Induced Carbonyl/Oxidative Stress in S. cerevisiae: Involvement of TOR. Biochem Res Int. 2016; 2016: Article ID 8917270, 10 pages.
  11. Weinberger M, Mesquita A, Caroll T, Marks L, Yang H, Zhang Z, Ludovico P, Burhans WiC. Growth signaling promotes chronological aging in budding yeast by inducing superoxide anions that inhibit quiescence. Aging (Albany NY). 2010; 2 (10): 709–26.
  12. Heitman J, Movva NN, Hall MN. Targets for cell cycle arrest by the immunosuppressant rapamycin in yeast. Science. 1991; 253: 905–9.
  13. Mao Y, van Hoef V, Zhang X, Wennerberg E, Lorent J, Witt K, Masvidal L, Liang Sh, Murray Sh, Larsson O, Kiessling R, Andreas Lundqvist. IL-15 activates mTOR and primes stress-activated gene expression leading to prolonged antitumor capacity of NK cells. Blood. 2016 Sep 15; 128 (11): 1475–89.
  14. Gidlöf O, Johnstone AL, Bader K, Khomtchouk BB, O'Reilly JJ, Celik S, Van Booven DJ, et al. Ischemic Preconditioning Confers Epigenetic Repression of Mtor and Induction of Autophagy Through G9a-Dependent H3K9 Dimethylation. J Am Heart Assoc. 2016 Dec 22; 5 (12): e004076.
  15. Lushchak VI. Budding yeast Saccharomyces cerevisiae as a model to study oxidative modification of proteins in eukaryotes. Acta Biochim Pol. 2006; 53 (4): 679–84.
  16. Conconi A, Jager-Vottero P, Zhang X, Beard BC, Smerdon MJ. Mitotic viability and metabolic competence in UVirradiated yeast cells,” Mutation Research. Mutation Research. 2000 Feb 16; 459 (1): 55-64.
  17. Kittipongdaja W, Wu X, Garner J, Liu X, Komas SM, Hwang ST, Schieke SM. Rapamycin Suppresses Tumor Growth and Alters the Metabolic Phenotype in T-Cell Lymphoma. J Invest Dermatol. 2015 Sep; 135 (9): 2301–8.
  18. Sofer A, Lei K, Johannessen CM, Ellisen LW. Regulation of mTOR and cell growth in response to energy stress by REDD1. Mol Cell Biol. 2005 Jul; 25 (14): 5834–45.
  19. Sabatini DM, Laplante M. mTOR signaling in growth control and disease. Cell. 2012; 149 (2): 274–93.
  20. Semchyshyn H. Hydrogen peroxide-induced response in E. coli and S. cerevisiae: different stages of the flow of the genetic information. Cent Eur J Biol. 2009; 4 (2): 142–53.
  21. Semchyshyn HM, Bayliak MM, Lushchak VI. In book: Biology of Starvation in Humans and Other Organisms, Editor: TC Merkin. 2011. p. 103–50.
  22. Sharma PK, Agrawal V, Roy N. Mitochondria-mediated hormetic response in life span extension of calorie-restricted Saccharomyces cerevisiae. Age (Dordr). 2011; 33 (2): 143–54.
  23. Wei Y, Zheng XF. Sch9 partially mediates TORC1 signaling to control ribosomal RNA synthesis. Cell Cycle. 2009 Dec 15; 8 (24): 4085–90.
  24. Xiong Y, Sheen J. Moving beyond translation: Glucose-TOR signaling in the transcriptional control of cell cycle. Cell Cycle. 2013; 12 (13): 1989–90.