Thiamine leads to oxidative stress resistance via regulation of the glucose metabolism

Thiamine diphosphate (ThDP) is an essential cofactor for important enzymes in carbohydrate, amino acid and lipid metabolisms. It is also known that thiamine plays an important role in stress response of some organisms. In this study, we focused on the effect of thiamine on stress responses triggered by various stress agents. For this purpose, firstly, viability of Schizosaccharomyces pombe cell cultures was examined under oxidative, osmotic and heat stresses. The highest tolerance observed in cell viability due to the presence of extracellular thiamine (1.5 mu M) was found only against oxidative stress. Then. enzyme activity of catalase and superoxide dismutase (SOD) involved in antioxidant defense mechanism and the expression analysis of genes encoding enzymes related to glucose metabolism and stress response pathways were investigated under oxidative stress. In this condition, it was not observed any difference in SOD and catalase activities, and their gene expressions due to the presence of thiamine, whereas the upregulation of pyruvate dehydrogenase (pdb1), transketolase (SPBC2G5.05). fructose-1,6-bisphosphatase (fbp1) and the downregulation of pyruvate decarboxylase (pdc201) were observed. In conclusion, these findings suggest that extracellular thiamine leading to oxidative stress resistance have an impact on the regulation of glucose metabolism by shifting the energy generation from fermentation to respiration

Hydrogen peroxide-induced oxidative stress upregulates ght5 gene belonging to hexose transporters in Schizosaccharomyces pombe

Hydrogen peroxide is an agent that triggers oxidative stress. Glucose, which is a source of carbon and energy has a regulatory role in many metabolic processes such as growth rate, fermentation capacity and stress response. Schizosaccharomyces pombe has eight hexose transporters with a different affinity for glucose and/or related monosaccharides. In S. pombe. Ght5 is a glucose transporter with high-affinity. We aimed to investigate the effects of H2O2-induced oxidative stress on hexose transporters using glucose repression-resistant mutant strains (ird5 and ird11) of S. pombe. We analyzed the percentage of glucose consumption in S. pombe wild-type and mutant cells under stressed and non-stressed conditions. Then we compared the expression levels of the genes encoding hexose transporters under the same conditions. We confirmed that the glucose consumption efficiencies of the mutants were slower than the wild-type as in earlier study under non-stressed condition. The percentage of glucose consumption reduced by approximately two-fold in ird11 and wild-type, but not change in ird5, under a stressed condition. There is no difference between cells shape and size of S. pombe strains under stressed and non-stressed conditions. Under stress-induced condition, the expression levels of ght3, ght4 genes in ird11 and wild-type, and ght4, ght6 genes in ird5 decreased, but that of ght5 gene remarkably increased in only wild-type. We suggested that oxidative stress caused by H2O2 leads to upregulation of the ght5 gene in S. pombe

LOSS OF GIT1 GENE IN FISSION YEAST PROVIDES RESISTANCE TO ENDOPLASMIC RETICULUM STRESS

Schizosaccharomyces pombe detects glucose G-protein coupled receptor and transmits signal transduction via a cAMP-dependent protein kinase A (PICA) pathway. Also, Git1 C2 domain protein is required for maintaining basal cAMP levels and for producing glucose-triggered cAMP response. Actually, Git1 is a member of the UNC-13/Munc13 protein family that are conserved in eukaryotes and functionally included in synaptic vesicle exocytosis. We aimed to investigate the impact of Git1 on the vesicular trafficking dependent on endoplasmic reticulum and on the oxidative stress response. In this study, we cloned the full-length (git1T) of S. pombe girl gene into pSGP572 plasmid, as a S. pombe expression vector carrying thiamine repressed promoter, nmt1 and C-terminal GFP. Then, we compared the viability of S. pombe strains (wild type, git Delta, pSGP572/git Delta, pG1T/git Delta) against to H2O2-induced oxidative stress and tunicamycin-induced ER stress to that of their control groups. We found that deletion of git1 gene brought S. pombe resistance to ER stress, but not oxidative stress in S. pombe cells

Role of Oxidative Stress Response and Trehalose Accumulation in the Longevity of Fission Yeast

Background: Glucose is the preferred carbon and energy source in most organisms and plays an active role in the regulation of many biological processes. However, an excess of glucose leads to such undesirable conditions as diabetes and age-related diseases. Since Schizosaccharomyces pombe homologous of many human genes, it offers several advantages for the investigation of the molecular mechanisms underlying human disease and aging studies. We have identified two glucose-repression-resistant mutants (ird5 and ird11) of S. pombe