Oxidative stress in Schizosaccharomyces pombe: different H2O2 levels, different response pathways.
Schizosaccharomyces pombe triggers different signalling pathways depending on the severity of the oxidative stress exerted, the main ones being the Pap1 and the Sty1 pathways. The Pap1 transcription factor is more sensitive to hydrogen peroxide (H(2)O(2)) than the MAP kinase Sty1 pathway, and is designed to induce adaptation, rather than survival, responses. The peroxiredoxin Tpx1 acts as a H(2)O(2) sensor and the upstream activator of the Pap1 pathway. Therefore, sensitivity to H(2)O(2) depends on this thioredoxin peroxidase. In order to achieve maximal activation of the MAP kinase pathway, the concentration of H(2)O(2) needs to be at least fivefold higher than that to fully activate Pap1. Tpx1 is a H(2)O(2) scavenger, thus its peroxidase activity is essential for aerobic growth. As described for other eukaryotic peroxiredoxins, high doses of H(2)O(2) temporarily inactivate Tpx1 and delay Pap1 activation, whereas the Sty1 pathway remains fully functional under these conditions. As part of the Sty1-dependent transcriptional response, the expression of Srx1 is induced and this reductase re-activates the over-oxidised Tpx1. Therefore, the antioxidant pathways of the fission yeast are perfectly designed so that the transcriptional programs triggered by the different signalling pathways never overlap.
Vivancos
Ana P
AP
Cell Signalling Unit, Departament de Ciències Experimentals i de la Salut, Universitat Pompeu Fabra, C/Dr. Aiguader 80, Barcelona, 08003, Spain.
Jara
Mónica
M
Zuin
Alice
A
Sansó
Miriam
M
Hidalgo
Elena
E
D026905:Amino Acid Transport Systems / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D018384:Oxidative Stress / Q000502:physiology*; D000073718:Pancreatitis-Associated Proteins; D010544:Peroxidases / Q000378:metabolism*; D054464:Peroxiredoxins; D012568:Schizosaccharomyces / Q000502:physiology*; D029702:Schizosaccharomyces pombe Proteins / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*
D026905:Amino Acid Transport Systems; D000073718:Pancreatitis-Associated Proteins; C000612141:REG3A protein, human; D029702:Schizosaccharomyces pombe Proteins; C515985:Tpx1 protein, S pombe; D006861:Hydrogen Peroxide; D010544:Peroxidases; D054464:Peroxiredoxins; D020928:Mitogen-Activated Protein Kinases; C095409:sty1 protein, S pombe