Oxidant resistance in a yeast mutant deficient in the Sit4 phosphatase.
Resistance to thiol oxidation can arise from mutations altering redox homeostasis. A Saccharomyces cerevisiae sit4-110 mutant is here described, which was isolated as resistant to the thiol-specific oxidant dipyridyl disulfide (DPS) and which contains a single-residue substitution in the SIT4 gene. Sit4p is a protein phosphatase with multiple roles in signal transduction through the target-of-rapamycin (TOR) pathway. We found that sit4-110 elevates the levels of glutathione. However, this cannot be the (only) cause for the DPS-resistance, since sit4-110 also conferred DPS/H2O2-resistance in a glutathione-deficient strain. Of the known Sit4p substrates, only Tip41p is involved in DPS-resistance; both Delta tip41 deletion and overexpression of the Tip41p target Tap42p resulted in increased DPS-resistance. Thus, the role of Sit4p in DPS-tolerance differs from its role during TOR-inactivation and salt stress. In view of Tap42p's known involvement in actin homeostasis, sit4-110 could compensate for putative actin-related defects caused by DPS. However, sit4-110 has pronounced actin polarization defects under both absence and presence of DPS. A relation between actin homeostasis and DPS resistance of sit4-110 cannot be ruled out, but our results suggest that unknown pathways might be involved in DPS resistance through mechanisms involving the Sit4p and/or Tap42p function(s).
López-Mirabal
H Reynaldo
HR
Carlsberg Laboratory, Gamle Carlsberg Vej 10, 2500 Copenhagen Valby, Denmark.
Winther
Jakob R
JR
Kielland-Brandt
Morten C
MC
D000199:Actins / Q000378:metabolism; D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D003681:Dehydration / Q000235:genetics; D004220:Disulfides / Q000494:pharmacology; D025141:Drug Resistance, Fungal / Q000235:genetics*; D005978:Glutathione / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000502:physiology; D008969:Molecular Sequence Data; D009154:Mutation; D009584:Nitrogen / Q000378:metabolism; D016877:Oxidants / Q000494:pharmacology; D018384:Oxidative Stress / Q000235:genetics; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics; D054648:Protein Phosphatase 2 / Q000235:genetics*; D011725:Pyridines / Q000494:pharmacology; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000502:physiology; D012492:Salts / Q000378:metabolism; D017386:Sequence Homology, Amino Acid
D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; D004220:Disulfides; D047908:Intracellular Signaling Peptides and Proteins; D016877:Oxidants; D011725:Pyridines; D029701:Saccharomyces cerevisiae Proteins; D012492:Salts; C100984:TAP42 protein, S cerevisiae; C444301:TIP41 protein, S cerevisiae; C007542:4,4'-dipyridyl disulfide; D054648:Protein Phosphatase 2; C104343:SIT4 protein, S cerevisiae; D010744:Phosphoric Monoester Hydrolases; D005978:Glutathione; D009584:Nitrogen