title: Vacuolar H+-ATPase d2 subunit: molecular characterization, developmental regulation, and localization to specialized proton pumps in kidney and bone.
abstract: The ubiquitous multisubunit vacuolar-type proton pump (H+- or V-ATPase) is essential for acidification of diverse intracellular compartments. It is also present in specialized forms at the plasma membrane of intercalated cells in the distal nephron, where it is required for urine acidification, and in osteoclasts, playing an important role in bone resorption by acid secretion across the ruffled border membrane. It was reported previously that, in human, several of the renal pump's constituent subunits are encoded by genes that are different from those that are ubiquitously expressed. These paralogous proteins may be important in differential functions, targeting or regulation of H+-ATPases. They include the d subunit, where d1 is ubiquitous whereas d2 has a limited tissue expression. This article reports on an investigation of d2. It was first confirmed that in mouse, as in human, kidney and bone are two of the main sites of d2 mRNA expression. d2 mRNA and protein appear later during nephrogenesis than does the ubiquitously expressed E1 subunit. Mouse nephron-segment reverse transcription-PCR revealed detectable mRNA in all segments except thin limb of Henle's loop and distal convoluted tubule. However, with the use of a novel d2-specific antibody, high-intensity d2 staining was observed only in intercalated cells of the collecting duct in fresh-frozen human kidney, where it co-localized with the a4 subunit in the characteristic plasma membrane-enhanced pattern. In human bone, d2 co-localized with the a3 subunit in osteoclasts. This different subunit association in different tissues emphasizes the possibility of the H+-ATPase as a future therapeutic target.
authors.affiliation: Department of Medical Genetics, University of Cambridge, United Kingdom.
authors.forename: Annabel N
authors.initials: AN
authors.lastname: Smith
authors.forename: François
authors.initials: F
authors.lastname: Jouret
authors.forename: Sharyn
authors.initials: S
authors.lastname: Bord
authors.forename: Katherine J
authors.initials: KJ
authors.lastname: Borthwick
authors.forename: Rafia S
authors.initials: RS
authors.lastname: Al-Lamki
authors.forename: Carsten A
authors.initials: CA
authors.lastname: Wagner
authors.forename: Deborah C
authors.initials: DC
authors.lastname: Ireland
authors.forename: Valerie
authors.initials: V
authors.lastname: Cormier-Daire
authors.forename: Annalisa
authors.initials: A
authors.lastname: Frattini
authors.forename: Anna
authors.initials: A
authors.lastname: Villa
authors.forename: Uwe
authors.initials: U
authors.lastname: Kornak
authors.forename: Olivier
authors.initials: O
authors.lastname: Devuyst
authors.forename: Fiona E
authors.initials: FE
authors.lastname: Karet
mesh_terms: D000328:Adult; D000818:Animals; D000918:Antibody Specificity; D005260:Female; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D007150:Immunohistochemistry; D007668:Kidney / Q000196:embryology / Q000502:physiology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009399:Nephrons / Q000196:embryology / Q000502:physiology; D010010:Osteoclasts / Q000502:physiology; D010022:Osteopetrosis / Q000235:genetics; D021122:Protein Subunits / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D017494:Proton Pumps / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012272:Ribs / Q000166:cytology / Q000196:embryology / Q000502:physiology*; D025262:Vacuolar Proton-Translocating ATPases / Q000235:genetics* / Q000276:immunology / Q000378:metabolism
chemical_list: D021122:Protein Subunits; D017494:Proton Pumps; D025262:Vacuolar Proton-Translocating ATPases