title: Physical interactions and functional coupling between Daxx and sodium hydrogen exchanger 1 in ischemic cell death.
abstract: Daxx, a death domain-associated protein, is implicated in ischemic cell death. To clarify the mechanism of cell death mediated by Daxx, a yeast two-hybrid assay was performed. Sodium hydrogen exchanger isoform 1 (NHE1) was identified as a Daxx-interacting protein. During ischemic stress, Daxx translocates from the nucleus to the cytoplasm, where it colocalizes with NHE1. Daxx binds to the ezrin/radixin/moesin-interacting domain of NHE1, in competition with ezrin. Consistent with this finding, transfection of the constitutively cytoplasmic mutant, Daxx(W621A), inhibited ezrin-mediated Akt-1 activation. Moreover, transfection of Daxx(W621A), but not the Daxx(S667A) mutant that is confined to the nucleus, accelerated pH(i) recovery from an acid load, indicating that the cytoplasmic protein activates NHE1. Based on the results, we propose that ischemic insult triggers the nucleocytoplasmic translocation of Daxx, following which cytoplasmic Daxx stimulates the NHE1 transporter activity and suppresses activation of the NHE1-ezrin-Akt-1 pathway. Our data support a novel molecular function of Daxx as an upstream regulator of NHE1 in ischemic cell death.
authors.affiliation: School of Bioscience & Biotechnology, Chungnam National University, 220 Gung-dong, Yuseong-gu, Daejeon 305-764, South Korea.
authors.forename: Yong-Sam
authors.initials: YS
authors.lastname: Jung
authors.forename: Hye-Young
authors.initials: HY
authors.lastname: Kim
authors.forename: Juno
authors.initials: J
authors.lastname: Kim
authors.forename: Min-Goo
authors.initials: MG
authors.lastname: Lee
authors.forename: Jacques
authors.initials: J
authors.lastname: Pouysségur
authors.forename: Eunhee
authors.initials: E
authors.lastname: Kim
mesh_terms: D021581:Active Transport, Cell Nucleus; D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000737:chemistry / Q000378:metabolism*; D016923:Cell Death / Q000502:physiology; D002467:Cell Nucleus / Q000378:metabolism; D056970:Co-Repressor Proteins; D006367:HeLa Cells; D006801:Humans; D007700:Kinetics; D018832:Molecular Chaperones; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers / Q000737:chemistry / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D027682:Cation Transport Proteins; D056970:Co-Repressor Proteins; C106985:DAXX protein, human; D018832:Molecular Chaperones; D009687:Nuclear Proteins; C490998:SLC9A1 protein, human; D000074082:Sodium-Hydrogen Exchanger 1; D017923:Sodium-Hydrogen Exchangers