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Gpx2, one of three glutathione peroxidase homologs (Gpx1, Gpx2, and Gpx3) in Saccharomyces cerevisiae, is an atypical 2-Cys peroxiredoxin that prefers to use thioredoxin as a reducing agent in vitro. Despite Gpx2 being an antioxidant, no obvious phenotype of gpx2Δ mutant cells in terms of oxidative stress has yet been found. To gain a clue as to Gpx2's physiological function in vivo, here we identify its intracellular distribution. Gpx2 was found to exist in the cytoplasm and mitochondria. In mitochondria, Gpx2 was associated with the outer membrane of the cytoplasmic-side, as well as the inner membrane of the matrix-side. The redox state of the mitochondrial Gpx2 was regulated by Trx1 and Trx2 (cytoplasmic thioredoxin), and by Trx3 (mitochondrial matrix thioredoxin). In addition, we found that the disruption of GPX2 reduced the sporulation efficiency of diploid cells., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Since it seems quite difficult for frozen cells to repair the damage caused by freezing, the adequate responses appear to be induced during and/or after the thawing process to recover from the damage due to freezing. In this study, the cellular events happening upon the return from freezing at -30 degrees C to a growth temperature (28 degrees C) were investigated. Yap1p, an oxidative stress-responsive transcription factor, was not activated in the thawed cells, indicating that no serious oxidative stress was generated in the frozen-thawed cells. On the other hand, Msn2p and Msn4p, general stress-responsive transcription factors, were activated in the thawed cells and caused the increased expression of a number of Msn2p/Msn4p-target genes including SOD1, SOD2, and several HSP genes. Since almost no expression of Msn2p/Msn4p-target genes was induced before thawing, these results indicate that Msn2p and Msn4p play a role during the recovery process from freezing.