A Redox-Sensitive Thiol in Wis1 Modulates the Fission Yeast Mitogen-Activated Protein Kinase Response to H₂O₂ and Is the Target of a Small Molecule

Abstract

Oxidation of a highly conserved cysteine (Cys) residue located in the kinase activation loop of mitogen-activated protein kinase kinases (MAPKK) inactivates mammalian MKK6. This residue is conserved in the fission yeast <i>Schizosaccharomyces pombe</i> MAPKK Wis1, which belongs to the H₂O₂-responsive MAPK Sty1 pathway. Here, we show that H₂O₂ reversibly inactivates Wis1 through this residue (C458) <i>in vitro</i> We found that C458 is oxidized <i>in vivo</i> and that serine replacement of this residue significantly enhances Wis1 activation upon addition of H₂O₂ The allosteric MAPKK inhibitor INR119, which binds in a pocket next to the activation loop and C458, prevented the inhibition of Wis1 by H₂O₂<i>in vitro</i> and significantly increased Wis1 activation by low levels of H₂O₂<i>in vivo</i> We propose that oxidation of C458 inhibits Wis1 and that INR119 cancels out this inhibitory effect by binding close to this residue. Kinase inhibition through the oxidation of a conserved Cys residue in MKK6 (C196) is thus conserved in the <i>S. pombe</i> MAPKK Wis1.