title: The NHERF2 sequence adjacent and upstream of the ERM-binding domain affects NHERF2-ezrin binding and dexamethasone stimulated NHE3 activity.
abstract: In the brush border of intestinal and kidney epithelial cells, scaffolding proteins ezrin, Na(+)-H(+) exchanger regulatory factor (NHERF)1 and NHERF2 play important roles in linking transmembrane proteins to the cytoskeleton and assembling signalling regulatory complexes. The last 30 carboxyl residues of NHERF1 and NHERF2 form the EBDs [ezrin, radixin and moesin (ERM)-binding domain]. The current study found that NHERF1/2 contain an ERM-binding regulatory sequence (EBRS), which facilitates the interaction between the EBD and ezrin. The EBRSs are located within 24 and 19 residues immediately upstream of EBDs for NHERF1 and NHERF2 respectively. In OK (opossum kidney) epithelial cells, EBRSs are necessary along with the EBD to distribute NHERF1 and NHERF2 exclusively to the apical domain. Furthermore, phosphorylation of Ser(303) located in the EBRS of NHERF2, decreases the binding affinity for ezrin, dislocates apical NHERF2 into the cytosol and increases the NHERF2 microvillar mobility rate. Moreover, increased phosphorylation of Ser(303) was functionally significant preventing acute stimulation of NHE3 (Na(+)-H(+) exchanger 3) activity by dexamethasone.
authors.affiliation: Departments of Medicine, Division of Gastroenterology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, U.S.A.
authors.forename: Jianbo
authors.initials: J
authors.lastname: Yang
authors.affiliation: Departments of Medicine, Division of Gastroenterology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, U.S.A.
authors.forename: Rafiquel
authors.initials: R
authors.lastname: Sarker
authors.affiliation: Departments of Medicine, Division of Gastroenterology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, U.S.A.
authors.forename: Varsha
authors.initials: V
authors.lastname: Singh
authors.affiliation: Departments of Medicine, Division of Gastroenterology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, U.S.A.
authors.forename: Prateeti
authors.initials: P
authors.lastname: Sarker
authors.affiliation: Departments of Medicine, Division of Gastroenterology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, U.S.A.
authors.forename: Jianyi
authors.initials: J
authors.lastname: Yin
authors.affiliation: Departments of Medicine, Division of Gastroenterology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, U.S.A.
authors.forename: Tian-E
authors.initials: TE
authors.lastname: Chen
authors.affiliation: Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, U.S.A.
authors.forename: Raghothama
authors.initials: R
authors.lastname: Chaerkady
authors.affiliation: Departments of Medicine, Division of Gastroenterology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, U.S.A.
authors.forename: Xuhang
authors.initials: X
authors.lastname: Li
authors.affiliation: Departments of Medicine, Division of Gastroenterology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, U.S.A.
authors.forename: C Ming
authors.initials: CM
authors.lastname: Tse
authors.affiliation: Departments of Medicine, Division of Gastroenterology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, U.S.A. Department of Physiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, U.S.A. mdonowit@jhmi.edu.
authors.forename: Mark
authors.initials: M
authors.lastname: Donowitz
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites / Q000187:drug effects / Q000502:physiology; D018938:Caco-2 Cells; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D003907:Dexamethasone / Q000494:pharmacology*; D057809:HEK293 Cells; D006801:Humans; D008969:Molecular Sequence Data; D009893:Opossums; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; C086680:ETV5 protein, human; D010750:Phosphoproteins; C000613385:SLC9A3 protein, human; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; D014157:Transcription Factors; C093376:sodium-hydrogen exchanger regulatory factor; D003907:Dexamethasone
keywords: NHE3; Na+-H+ exchanger regulatory factor (NHERF)1/2; epithelial cell; ezrin; microvillus; phosphorylation; radixin and moesin-binding regulatory sequence (EBRS)