title: Kidney Na+,K(+)-ATPase is associated with moesin.
abstract: Na+,K(+)-ATPase is a ubiquitous plasmalemmal membrane protein essential for generation and maintenance of transmembrane Na+ and K+ gradients in virtually all animal cell types. Activity and polarized distribution of renal Na+,(+)-ATPase appears to depend on connection of ankyrin to the spectrin-based membrane cytoskeleton as well as on association with actin filaments. In a previous study we showed copurification and codistribution of renal Na+,K(+)-ATPase not only with ankyrin, spectrin and actin, but also with two further peripheral membrane proteins, pasin 1 and pasin 2. In this paper we show by sequence analysis through mass spectrometry as well as by immunoblotting that pasin 2 is identical to moesin, a member of the FERM (protein 4.1, ezrin, radixin, moesin) protein family, all members of which have been shown to serve as cytoskeletal adaptor molecules. Moreover, we show that recombinant full-length moesin as well as its FERM domain bind to Na+,K(+)-ATPase and that this binding can be inhibited by an antibody specific for the ATPase activity-containing cytoplasmic loop (domain 3) of the Na+,K(+)-ATPase alpha-subunit. This loop has been previously shown to be a site essential for ankyrin binding. These observations indicate that moesin might not only serve as direct linker molecule of Na+,K(+)-ATPase to actin filaments but also modify ankyrin binding at domain 3 of Na+,K(+)-ATPase in a way similar to protein 4.1 modifying the binding of ankyrin to the cytoplasmic domain of the erythrocyte anion exchanger (AE1).
authors.affiliation: Medizinische Poliklinik, University of Würzburg, Würzburg, Germany. d.kraemer@medizin.uni-wuerzburg.de
authors.forename: Doris M
authors.initials: DM
authors.lastname: Kraemer
authors.forename: Brigitte
authors.initials: B
authors.lastname: Strizek
authors.forename: Helmuth E
authors.initials: HE
authors.lastname: Meyer
authors.forename: Katrin
authors.initials: K
authors.lastname: Marcus
authors.forename: Detlev
authors.initials: D
authors.lastname: Drenckhahn
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015151:Immunoblotting; D007150:Immunohistochemistry; D007668:Kidney / Q000201:enzymology* / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D008840:Microfilament Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D011485:Protein Binding; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods; D013552:Swine
chemical_list: D008565:Membrane Proteins; D008840:Microfilament Proteins; C071058:moesin; D000254:Sodium-Potassium-Exchanging ATPase