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

Abstract

Methylglyoxal, a toxic metabolite synthesized in vivo during glycolysis, inhibits cell growth. One of the mechanisms protecting eukaryotic cells against its toxicity is the glyoxalase system, composed of glyoxalase I and II (glo1 and glo2), which converts methylglyoxal into D-lactic acid in the presence of glutathione. Here we have shown that the two principal oxidative stress response pathways of Schizosaccharomyces pombe, Sty1 and Pap1, are involved in the response to methylglyoxal toxicity. The mitogen-activated protein kinase Sty1 is phosphorylated and accumulates in the nucleus following methylglyoxal treatment. Moreover, glo2 expression is induced by methylglyoxal and environmental stresses in a Sty1-dependent manner. The transcription factor Pap1 also accumulates in the nucleus, activating the expression of its target genes following methylglyoxal treatment. Our studies showed that the C-terminal cysteine-rich domain of Pap1 is sufficient for methylglyoxal sensing. Furthermore, the redox status of Pap1 is not changed by methylglyoxal. We propose that methylglyoxal treatment triggers Pap1 and Sty1 nuclear accumulation, and we describe the molecular basis of such activation mechanisms. In addition, we discuss the potential physiological significance of these responses to a natural toxic metabolite.

Cells Lacking Pfh1, a Fission Yeast Homolog of Mammalian Frataxin Protein, Display Constitutive Activation of the Iron Starvation Response

“…Yeast cells were grown in anaerobic liquid cultures in bottles filled to the top (50 ml) with YE5S until exponential phase and to the A 600 indicated for each method. We used wild-type strains 972 (h Ϫ ) and 975 (h ϩ ) (24) and AV18 (h Ϫ sty1::kanMX6) (25). To construct S. pombe strains with specific loci deleted, we transformed wild-type strain 972 with linear fragments containing ORFs fused to kanMX6 or natMX6, obtained by PCR amplification using ORF-specific primers and plasmids pFA6a-kanMX6 (26) or pFA6a-natMX6 (27) as templates, and we obtained strains NG60 (h Ϫ pfh1::natMX6) and NG40 (h Ϫ php4::kanMX6) by transforming as described previously (28).…”

New roles of the fission yeast eIF2α kinases Hri1 and Gcn2 in response to nutritional stress

“…Hri1 is activated at the onset of stationary phase Phosphorylation, as well as nuclear accumulation, of Sty1 and Sty1-dependent gene expression at the transition between exponential and stationary growth was previously reported (Zuin et al, 2010;Zuin et al, 2005). We wanted to investigate the possible contribution of the eIF2a kinase pathway when the culture reached high density and reduced growth.…”

“…These findings represent what is to our knowledge the first example of Hri1 function in fission yeast. Previous reports showed that during transition to the stationary phase, Sty1 also becomes activated and triggers a transcriptional stress programme (Zuin et al, 2010;Zuin et al, 2005). Moreover, Sty1 is required for, and can be activated by different stress conditions, including hydrogen peroxide and glucose or nitrogen starvation (Vivancos et al, 2006).…”

“…It was reported earlier that Sty1 was required for the arrest of cell growth under the stress conditions produced by nitrogen starvation (Shiozaki and Russell, 1996) and activated at the onset of stationary phase (Zuin et al, 2005). In addition, we have previously determined that the activated MAPK Sty1 negatively regulates Gcn2 and Hri2 activities under oxidative stress (Berlanga et al, 2010).…”

“…Thus, during transition to stationary phase in glucose-limiting conditions, Sty1 becomes activated and triggers a transcriptional stress programme, whereas such activation does not occur under glucose-rich conditions (Zuin et al, 2010;Zuin et al, 2005). Then, the Sty1 activation at the onset of stationary phase is required for both stress-resistance acquisition and lifespan extension under calorie restriction (Zuin et al, 2010).…”