title: Evolutionary acquisition of cysteines determines FOXO paralog-specific redox signaling.
abstract: Reduction-oxidation (redox) signaling, the translation of an oxidative intracellular environment into a cellular response, is mediated by the reversible oxidation of specific cysteine thiols. The latter can result in disulfide formation between protein hetero- or homodimers that alter protein function until the local cellular redox environment has returned to the basal state. We have previously shown that this mechanism promotes the nuclear localization and activity of the Forkhead Box O4 (FOXO4) transcription factor.
  
  
  OBJECTIVE
  In this study, we sought to investigate whether redox signaling differentially controls the human FOXO3 and FOXO4 paralogs.
  
  
  RESULTS
  We present evidence that FOXO3 and FOXO4 have acquired paralog-specific cysteines throughout vertebrate evolution. Using a proteome-wide screen, we identified previously unknown redox-dependent FOXO3 interaction partners. The nuclear import receptors Importin-7 (IPO7) and Importin-8 (IPO8) form a disulfide-dependent heterodimer with FOXO3, which is required for its reactive oxygen species-induced nuclear translocation. FOXO4 does not interact with IPO7 or IPO8.
  
  
  CONCLUSIONS
  IPO7 and IPO8 control the nuclear import of FOXO3, but not FOXO4, in a redox-sensitive and disulfide-dependent manner. Our findings suggest that evolutionary acquisition of cysteines has contributed to regulatory divergence of FOXO paralogs, and that phylogenetic analysis can aid in the identification of cysteines involved in redox signaling.
authors: 1 Molecular Cancer Research, Center for Molecular Medicine, University Medical Center Utrecht , Utrecht, The Netherlands .
authors: Marrit
authors: M
authors: Putker
authors: Harmjan R
authors: HR
authors: Vos
authors: Kim
authors: K
authors: van Dorenmalen
authors: Hesther
authors: H
authors: de Ruiter
authors: Ana G
authors: AG
authors: Duran
authors: Berend
authors: B
authors: Snel
authors: Boudewijn M T
authors: BM
authors: Burgering
authors: Michiel
authors: M
authors: Vermeulen
authors: Tobias B
authors: TB
authors: Dansen
mesh_terms: D015153:Blotting, Western; D018797:Cell Cycle Proteins; D045744:Cell Line, Tumor; D003545:Cysteine / Q000378:metabolism; D051858:Forkhead Transcription Factors; D006801:Humans; D028884:Karyopherins / Q000378:metabolism*; D010084:Oxidation-Reduction; D017382:Reactive Oxygen Species / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D053719:Tandem Mass Spectrometry; D014157:Transcription Factors / Q000378:metabolism*; D028961:beta Karyopherins / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; C108803:FOXO4 protein, human; D051858:Forkhead Transcription Factors; C466996:IPO7 protein, human; C107282:IPO8 protein, human; D028884:Karyopherins; D017382:Reactive Oxygen Species; D018160:Receptors, Cytoplasmic and Nuclear; D014157:Transcription Factors; D028961:beta Karyopherins; D003545:Cysteine