title: Role of serine 249 of ezrin in the regulation of sodium-dependent phosphate transporter NaPi-IIa activity in renal proximal tubular cells.
abstract: Type IIa sodium-dependent phosphate transporter (NaPi-IIa) is responsible for renal phosphate reabsorption and maintenance of systemic phosphate homeostasis in mammals. Macromolecular complex formation of NaPi-IIa with sodium-proton exchanger related factor-1 (NHERF-1) and ezrin is important for apical membrane localization in the proximal tubular cells. Here, we investigated the interactions of the ezrin phosphomimetic mutation of serine to aspartic acid at 249 with NHERF-1 and the inhibition of apical membrane localization of NaPi-IIa. In vitro phosphorylation analysis revealed that serine 249 of human ezrin serves as a phosphorylation site for protein kinase A. The N-terminal half of ezrin had a dominant negative effect on the phosphate transport activity and inhibited the apical localization of NaPi-IIa in renal proximal tubular cells. We found that the phosphomimetic S249D mutant interfered with the inhibitory effects of the dominant negative mutant on the transport and localization of NaPi-IIa. The S249D mutant also inhibited the interaction with NHERF-1. Therefore, serine 249 of ezrin can play important roles in the regulation of the complex formation and membrane localization of NaPi-IIa.
authors.affiliation: Department of Clinical Nutrition, Institute of Health Biosciences, the University of Tokushima Graduate School, Tokushima, Japan.
authors.forename: Fumiyo
authors.initials: F
authors.lastname: Yamada
authors.forename: Daisuke
authors.initials: D
authors.lastname: Horie
authors.forename: Asako
authors.initials: A
authors.lastname: Nakamura
authors.forename: Ayako
authors.initials: A
authors.lastname: Tanimura
authors.forename: Hironori
authors.initials: H
authors.lastname: Yamamoto
authors.forename: Hiroko
authors.initials: H
authors.lastname: Segawa
authors.forename: Mikiko
authors.initials: M
authors.lastname: Ito
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Miyamoto
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Taketani
authors.forename: Eiji
authors.initials: E
authors.lastname: Takeda
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D019556:COS Cells; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology; D003598:Cytoskeletal Proteins / Q000737:chemistry / Q000502:physiology*; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D012694:Serine; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism; D050613:Sodium-Phosphate Cotransporter Proteins, Type IIa / Q000502:physiology*; D000099149:Ezrin
chemical_list: D000199:Actins; D017868:Cyclic AMP-Dependent Protein Kinases; D003598:Cytoskeletal Proteins; D010750:Phosphoproteins; D012694:Serine; D017923:Sodium-Hydrogen Exchangers; D050613:Sodium-Phosphate Cotransporter Proteins, Type IIa; D000099149:Ezrin; C493554:SLC34A1 protein, human; C093376:sodium-hydrogen exchanger regulatory factor