title: The B1-subunit of the H(+) ATPase is required for maximal urinary acidification.
abstract: The multisubunit vacuolar-type H(+)ATPases mediate acidification of various intracellular organelles and in some tissues mediate H(+) secretion across the plasma membrane. Mutations in the B1-subunit of the apical H(+)ATPase that secretes protons in the distal nephron cause distal renal tubular acidosis in humans, a condition characterized by metabolic acidosis with an inappropriately alkaline urine. To examine the detailed cellular and organismal physiology resulting from this mutation, we have generated mice deficient in the B1-subunit (Atp6v1b1(-/-) mice). Urine pH is more alkaline and metabolic acidosis is more severe in Atp6v1b1(-/-) mice after oral acid challenge, demonstrating a failure of normal urinary acidification. In Atp6v1b1(-/-) mice, the normal urinary acidification induced by a lumen-negative potential in response to furosemide infusion is abolished. After an acute intracellular acidification, Na(+)-independent pH recovery rates of individual Atp6v1b1(-/-) intercalated cells of the cortical collecting duct are markedly reduced and show no further decrease after treatment with the selective H(+)ATPase inhibitor concanamycin. Apical expression of the alternative B-subunit isoform, B2, is increased in Atp6v1b1(-/-) medulla and colocalizes with the H(+)ATPase E-subunit; however, the greater severity of metabolic acidosis in Atp6v1b1(-/-) mice after oral acid challenge indicates that the B2-subunit cannot fully functionally compensate for the loss of B1. Our results indicate that the B1 isoform is the major B-subunit isoform that incorporates into functional, plasma membrane H(+)ATPases in intercalated cells of the cortical collecting duct and is required for maximal urinary acidification.
authors.affiliation: Departments of Genetics, Cellular and Molecular Physiology, Surgery, and Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT 06510, USA.
authors.forename: Karin E
authors.initials: KE
authors.lastname: Finberg
authors.forename: Carsten A
authors.initials: CA
authors.lastname: Wagner
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Bailey
authors.forename: Teodor G
authors.initials: TG
authors.lastname: Paunescu
authors.forename: Sylvie
authors.initials: S
authors.lastname: Breton
authors.forename: Dennis
authors.initials: D
authors.lastname: Brown
authors.forename: Gerhard
authors.initials: G
authors.lastname: Giebisch
authors.forename: John P
authors.initials: JP
authors.lastname: Geibel
authors.forename: Richard P
authors.initials: RP
authors.lastname: Lifton
mesh_terms: D000141:Acidosis, Renal Tubular / Q000201:enzymology* / Q000235:genetics / Q000652:urine; D000143:Acids / Q000008:administration & dosage / Q000652:urine*; D000818:Animals; D002462:Cell Membrane / Q000201:enzymology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007679:Kidney Medulla / Q000201:enzymology; D007685:Kidney Tubules, Collecting / Q000201:enzymology*; D051379:Mice; D018345:Mice, Knockout; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism; D011522:Protons; D025262:Vacuolar Proton-Translocating ATPases / Q000172:deficiency / Q000378:metabolism*
chemical_list: D000143:Acids; D021122:Protein Subunits; D011522:Protons; C480628:Atp6v1b1 protein, mouse; D025262:Vacuolar Proton-Translocating ATPases