title: NaPi-IIa interacting proteins and regulation of renal reabsorption of phosphate.
abstract: Control of phosphate (P(i)) homeostasis is essential for many biologic functions and inappropriate low levels of P(i) in plasma have been suggested to associate with several pathological states, including renal stone formation and stone recurrence. P(i) homeostasis is achieved mainly by adjusting the renal reabsorption of P(i) to the body's requirements. This task is performed to a major extent by the Na/Pi cotransporter NaPi-IIa that is specifically expressed in the brush border membrane of renal proximal tubules. While the presence of tight junctions in epithelial cells prevents the diffusion and mixing of the apical and basolateral components, the location of a protein within a particular membrane subdomain (i.e., the presence of NaPi-IIa at the tip of the apical microvilli) often requires its association with scaffolding elements which directly or indirectly connect the protein with the underlying cellular cytoskeleton. NaPi-IIa interacts with the four members of the Na(+)/H(+) exchanger regulatory factor family as well as with the GABA(A)-receptor associated protein . Here we will discuss the most relevant findings regarding the role of these proteins on the expression and regulation of the cotransporter, as well as the impact that their absence has in P(i) homeostasis.
authors.affiliation: Institute of Physiology and Zurich Center for Integrative Human Physiology (ZIHP), University of Zurich, Winterthurerstr. 190, 8057 Zurich, Switzerland. nati.hernando@access.uzh.ch
authors.forename: Nati
authors.initials: N
authors.lastname: Hernando
authors.forename: Serge M
authors.initials: SM
authors.lastname: Gisler
authors.forename: Sonja C
authors.initials: SC
authors.lastname: Reining
authors.forename: Nadine
authors.initials: N
authors.lastname: Déliot
authors.forename: Paola
authors.initials: P
authors.lastname: Capuano
authors.forename: Jürg
authors.initials: J
authors.lastname: Biber
authors.forename: Heini
authors.initials: H
authors.lastname: Murer
mesh_terms: D000042:Absorption; D000818:Animals; D006706:Homeostasis; D007668:Kidney / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D008954:Models, Biological; D054731:PDZ Domains / Q000502:physiology; D010710:Phosphates / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism; D050613:Sodium-Phosphate Cotransporter Proteins, Type IIa / Q000502:physiology*
chemical_list: D008869:Microtubule-Associated Proteins; D010710:Phosphates; D010750:Phosphoproteins; D017923:Sodium-Hydrogen Exchangers; D050613:Sodium-Phosphate Cotransporter Proteins, Type IIa; C093376:sodium-hydrogen exchanger regulatory factor