The B1-Subunit of the H+ATPase Is Required for Maximal Urinary Acidification

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 102; no. 38; pp. 13616 - 13621
• Main Authors: Finberg, Karin E., Wagner, Carsten A., Bailey, Matthew A., Păunescu, Teodor G., Breton, Sylvie, Brown, Dennis, Giebisch, Gerhard, Geibel, John P., Lifton, Richard P.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 20-09-2005; National Acad Sciences
• Subjects: Acidification; Acidosis; Acidosis, Renal Tubular - enzymology; Acidosis, Renal Tubular - genetics; Acidosis, Renal Tubular - urine; Acids - administration & dosage; Acids - urine; Adenosine triphosphatase; Adenosine triphosphatases; Animals; Biological Sciences; Cell Membrane - enzymology; Cell membranes; Humans; Hydrogen-Ion Concentration; Kidney Medulla - enzymology; Kidney Tubules, Collecting - enzymology; Kidneys; Mice; Mice, Knockout; Mutation; Protein Subunits - genetics; Protein Subunits - metabolism; Protons; Secretion; Urine; Vacuolar Proton-Translocating ATPases - deficiency; Vacuolar Proton-Translocating ATPases - metabolism
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0506769102

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.