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 (HOG)-mitogen-activated protein (MAP) kinase-dependent manner in Saccharomyces cerevisiae. Here we show that MG activates the HOG-MAP kinase cascade. Two osmosensors, Sln1 and Sho1, have been identified to function upstream of the HOG-MAP kinase cascade, and we reveal that MG initiates the signal transduction to this MAP kinase cascade through the Sln1 branch. We also demonstrate that MG activates the Msn2 transcription factor. Moreover, MG activated the uptake of Ca(2+) in yeast cells, thereby stimulating the calcineurin/Crz1-mediated Ca(2+) signaling pathway. We propose that MG functions as a signal initiator in yeast.
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ABSTRACT: The accumulation of protein adducts caused by carbonyl stress (CS) is a hallmark of cellular aging and other diseases, yet the detailed cellular effects of this universal phenomena are poorly understood. An understanding of the global effects of CS will provide insight into disease mechanisms and can guide the development of therapeutics and lifestyle changes to ameliorate their effects. To identify cellular functions important for the response to carbonyl stress, multiple genome-wide genetic screens were performed using two known inducers of CS. We found that different cellular functions were required for resistance to stress induced by methylglyoxal (MG) and glyoxal (GLY). Specifically, we demonstrate the importance of macromolecule catabolism processes for resistance to MG, confirming and extending known mechanisms of MG toxicity, including modification of DNA, RNA, and proteins. Combining our results with related studies that examined the effects of ROS allowed a comprehensive view of the diverse range of cellular functions affected by both oxidative and carbonyl stress. To understand how these diverse cellular functions interact, we performed a quantitative epistasis analysis by creating multimutant strains from those individual genes required for glyoxal resistance. This analysis allowed us to define novel glyoxal-dependent genetic interactions. In summary, using multiple genome-wide approaches provides an effective approach to dissect the poorly understood effects of glyoxal in vivo. These data, observations, and comprehensive dataset provide 1) a comprehensive view of carbonyl stress, 2) a resource for future studies in other cell types, and 3) a demonstration of how inexpensive cell-based assays can identify complex gene-environment toxicities.G3-Genes Genomes Genetics 08/2011; 1(3):219-31. DOI:10.1534/g3.111.000505 · 2.51 Impact Factor
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ABSTRACT: Stress tolerance is currently one of the major research topics in plant biology because of the challenges posed by changing climate and increasing demand to grow crop plants in marginal soils. Increased Zn tolerance and accumulation has been reported in tobacco expressing the glyoxalase 1-encoding gene from Brassica juncea. Previous studies in our laboratory showed some Zn tolerance-correlated differences in the levels of glyoxalase 1-like protein among accessions of Zn hyperaccumulator Thlaspi caerulescens. We have now isolated the corresponding gene (named here TcGLX1), including ca. 570bp of core and proximal promoter region. The predicted protein contains three glyoxalase 1 motifs and several putative sites for post-translational modification. In silico analysis predicted a number of cis-acting elements related to stress. The expression of TcGLX1 was not responsive to Zn. There was no correlation between the levels of TcGLX1 expression and the degrees of Zn tolerance or accumulation among T. caerulescens accessions nor was there co-segregation of TcGLX1 expression with Zn tolerance or Zn accumulation among F3 lines derived from crosses between plants from accessions with contrasting phenotypes for these properties. No phenotype was observed in an A. thaliana T-DNA insertion line for the closest A. thaliana homolog of TcGLX1, ATGLX1. These results suggest that glyoxalase 1 or at least the particular isoform studied here is not a major determinant of Zn tolerance in the Zn hyperaccumulator plant T. caerulescens. In addition, ATGLX1 is not essential for normal Zn tolerance in the non-tolerant, non-accumulator plant A. thaliana. Possible explanations for the apparent discrepancy between this and previous studies are discussed. KeywordsGlyoxalase 1–In silico analysis–Promoter– Thlaspi –Tolerance–ZnPlanta 06/2011; 233(6):1173-1184. DOI:10.1007/s00425-011-1370-7 · 3.38 Impact Factor
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ABSTRACT: In yeast, external signals such as high osmolarity or oxidant conditions activate the high osmolarity glycerol (HOG) mitogen-activated protein kinase (MAPK) cascade pathway, which consists of two upstream branches, i.e. Sho1p and Sln1p and common downstream elements, including the Pbs2p MAPK kinase and the Hog1p MAPK. We recently showed that the Candida lusitaniae SLN1 gene, potentially encoding a histidine kinase receptor, is crucial for oxidative stress adaptation when the fungus grows as budding yeast and during the early steps of pseudohyphal development. In the current study, we characterized the SHO1 gene of this opportunistic fungus. Complete loss of SHO1 function causes profound defects in pseudohyphal differentiation, especially in high osmolarity and oxidative stress conditions, suggesting a crucial role of SHO1 in the pseudohyphae morphogenetic transitions. Moreover, when grown as budding yeast, the sho1Delta mutant revealed a sensitivity to compounds that interfere with the cell wall assembly, pointing to a potential role of Sho1p in cell wall biogenesis. However, the sho1Delta mutant does not display evident cell-wall architecture modifications, such as aggregation phenotypes. Although not hypersusceptible to antifungals of clinical relevance, the sho1Delta mutants are susceptible to the filamentous fungi-specific antifungals dicarboximides and phenylpyrroles. Finally, our findings highlight some significant phenotypic differences when the C. lusitaniae sho1Delta mutant is compared with the corresponding mutants described in Saccharomyces cerevisiae, Candida albicans and Aspergillus fumigatus.Yeast 11/2008; 25(11):849-59. DOI:10.1002/yea.1636 · 1.74 Impact Factor