title: FXYD proteins: new tissue-specific regulators of the ubiquitous Na,K-ATPase.
abstract: Maintenance of the Na+ and K+ gradients between the intracellular and extracellular milieus of animal cells is a prerequisite for basic cellular homeostasis and for functions of specialized tissues. The Na,K-ATPase, an oligomeric P-type adenosine triphosphatase (ATPase), is composed of a catalytic alpha subunit and a regulatory beta subunit and is the main player that fulfils these tasks. A variety of regulatory mechanisms are necessary to guarantee appropriate Na,K-ATPase expression and activity adapted to changing physiological demands. Recently, a regulatory mechanism was defined that is mediated by interaction of Na,K-ATPase with small proteins of the FXYD family, which possess a single transmembrane domain and so far have been considered as channels or regulators of ion channels. The mammalian FXYD proteins FXYD1 through FXYD7 exhibit tissue-specific distribution. Phospholemman (FXYD1) in heart and skeletal muscle, the gamma subunit of Na,K-ATPase (FXYD2) and corticosteroid hormone-induced factor (FXYD4, also known as CHIF) in the kidney, and FXYD7 in the brain associate preferentially with the widely expressed Na,K-ATPase alpha1-beta1 isozyme and modulate its transport activity in a way that conforms to tissue-specific requirements. Thus, tissue- and isozyme-specific interaction of Na,K-ATPase with FXYD proteins contributes to proper handling of Na+ and K+ by the Na,K-ATPase, and ensures correct function in such processes as renal Na+-reabsorption, muscle contraction, and neuronal excitability.
authors.affiliation: Institute of Pharmacology and Toxicology, University of Lausanne, rue du Bugnon 27, CH-Lausanne, Switzerland.
authors.forename: Gilles
authors.initials: G
authors.lastname: Crambert
authors.forename: Käthi
authors.initials: K
authors.lastname: Geering
mesh_terms: D000818:Animals; D006801:Humans; D008562:Membrane Glycoproteins / Q000096:biosynthesis / Q000502:physiology*; D008565:Membrane Proteins / Q000096:biosynthesis / Q000502:physiology*; D009363:Neoplasm Proteins / Q000096:biosynthesis / Q000502:physiology*; D009419:Nerve Tissue Proteins / Q000096:biosynthesis / Q000502:physiology*; D009928:Organ Specificity / Q000502:physiology; D000254:Sodium-Potassium-Exchanging ATPase / Q000096:biosynthesis / Q000378:metabolism* / Q000502:physiology*
chemical_list: C091777:FXYD3 protein, human; C484265:Fxyd3 protein, mouse; C462940:Fxyd7 protein, mouse; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; C422209:corticosteroid hormone-induced factor; C416502:FXYD2 protein, human; D000254:Sodium-Potassium-Exchanging ATPase