The B1-subunit of the H(+) ATPase is required for maximal urinary acidification

Proc Natl Acad Sci U S A. 2005 Sep 20;102(38):13616-21. doi: 10.1073/pnas.0506769102. Epub 2005 Sep 8.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acidosis, Renal Tubular / enzymology*
  • Acidosis, Renal Tubular / genetics
  • Acidosis, Renal Tubular / urine
  • Acids / administration & dosage
  • Acids / urine*
  • Animals
  • Cell Membrane / enzymology*
  • Humans
  • Hydrogen-Ion Concentration
  • Kidney Medulla / enzymology
  • Kidney Tubules, Collecting / enzymology*
  • Mice
  • Mice, Knockout
  • Protein Subunits / genetics
  • Protein Subunits / metabolism
  • Protons
  • Vacuolar Proton-Translocating ATPases / deficiency
  • Vacuolar Proton-Translocating ATPases / metabolism*

Substances

  • Acids
  • Protein Subunits
  • Protons
  • Atp6v1b1 protein, mouse
  • Vacuolar Proton-Translocating ATPases