Methylglyoxal, a Metabolite Derived from Glycolysis, Functions as a Signal Initiator of the High Osmolarity Glycerol-Mitogen-activated Protein Kinase Cascade and Calcineurin/Crz1-mediated Pathway in Saccharomyces cerevisiae

Abstract

Methylglyoxal (MG) is a typical 2-oxoaldehyde derived from glycolysis, although it inhibits the growth of cells in all types of organism. Hence, it has been questioned why such a toxic metabolite is synthesized via the ubiquitous energy-generating pathway. We have previously reported that expression of GLO1, coding for the major enzyme detoxifying MG, was induced by osmotic stress in a high osmolarity glycerol ( Glycolysis is a ubiquitous energy-generating pathway in organisms. Triosephosphate isomerase is one of the enzymes involved in this anaerobic oxidation pathway for glucose. During the triosephosphate isomerase reaction, methylglyoxal (MG, 1 CH 3 COCHO) is synthesized by the ␤-elimination reaction from an enediolate phosphate intermediate (1, 2). Although MG is synthesized during normal metabolism of glucose, this aldehyde inhibits the growth of cells from microorganisms to higher eukaryotes, eventually killing them, and therefore, the raison d'etre of MG has been of considerable interest.By the systematic biochemical analysis of the metabolic fate of MG using the budding yeast Saccharomyces cerevisiae as a model organism, we revealed that MG is metabolized to lactic acid by two different routes (for reviews, see Refs. 3 and 4). One route is a glyoxalase system in which glyoxalase I and glyoxalase II are involved. In this route, MG is condensed with glutathione to give S-D-lactoylglutathione by the action of glyoxalase I, and the glutathione thiolester is then hydrolyzed to lactic acid and glutathione by glyoxalase II. The other route is a reduction/oxidation system consisting of methylglyoxal reductase and lactaldehyde dehydrogenase. MG is reduced to lactaldehyde by NADPH-dependent methylglyoxal reductase, and lactaldehyde is further oxidized to lactic acid by NAD ϩ -dependent lactaldehyde dehydrogenase. To evaluate the physiological importance of these enzymatic routes in vivo, we cloned the structural gene for glyoxalase I (GLO1) and demonstrated that a glo1⌬ mutant showed hypersensitivity to MG (5). Similarly, Bito et al. (6) reported that a mutant defective in glyoxalase II (glo2⌬) was also hypersensitive to MG. On the other hand, Chen et al. (7) recently reported that GRE2 is one of the genes encoding NADPH-dependent methylglyoxal reductase activity, although a gre2⌬ mutant did not exhibit sensitivity to MG as far as we discerned.2 Alternatively, the GRE3 gene encodes an aldose reductase, and the corresponding gene product is supposed to be involved in MG metabolism, although the disruption of GRE3 did not enhance susceptibility to MG (8). These results indicate that the glyoxalase system is the most important pathway for MG detoxification in S. cerevisiae. This was also the case in the fission yeast (9).To obtain a clue as to the cellular function of MG and its metabolic pathway, we have attempted to find the conditions that alter the intracellular MG level and/or MG-metabolizing enzyme activity in S. cerevisiae. We found that the expression of GLO1 is specifically induced by osmotic stress in a h...

ThHog1 controls the hyperosmotic stress response in Trichoderma harzianum

“…Therefore, this may be a different phenomenon from that described in yeasts and mammals using FK506 (Rodriguez-Hernandez et al, 2003;Sanchez-Perez et al, 2004). This result raises the possibility of the HOG and Ca 2+ pathways acting over common processes (Maeta et al, 2005), since only overexpression of hog1 F315S can restore, at least in . Mycoparasitic analysis of hog1 mutant strains.…”

Methylglyoxal Activates the Target of Rapamycin Complex 2-Protein Kinase C Signaling Pathway in Saccharomyces cerevisiae

“…Total protein extracts were prepared using the trichloroacetic acid extraction method (12). The protein concentrations of the samples were determined using an RC DC protein assay kit (Bio-Rad Laboratories).…”

“…For example, the exogenous addition of MG activated yeast AP-1-like transcription factors (Yap1 in Saccharomyces cerevisiae and Pap1 in Schizosaccharomyces pombe) through the reversible modification of their critical Cys residues within 45 min (10,11). MG was also found to enhance the influx of extracellular Ca 2ϩ into the cell, thereby activating the Ca 2ϩ /calcineurin system in S. cerevisiae (12). In the present study, we found that MG enhances the target of rapamycin (TOR) complex 2 (TORC2)-protein kinase C (Pkc1) signaling pathway in S. cerevisiae.…”

The Glycolytic Metabolite Methylglyoxal Activates Pap1 and Sty1 Stress Responses in Schizosaccharomyces pombe

“…For example, the YAP1 transcription factor, a homologue to Pap1 in S. pombe, is activated by MG (either by extracellular medium containing the natural metabolite or by increased intracellular MG in a ⌬glo1 strain) (12). Furthermore, MG can also trigger the Sty1 homologue HOG1 pathway (13). Despite similarities in the molecular components and sequence homologies of the various stress pathways between budding and fission yeasts, fundamental differences have been identified in recent years, prompting us to verify the universality of MG reactivity with stress pathways by characterizing the response of S. pombe to this metabolite.…”