The vacuolar-ATPase B1 subunit in distal tubular acidosis: Novel mutations and mechanisms for dysfunction

D. G. Fuster, J. Zhang, X. S. Xie, O. W. Moe

Research output: Contribution to journalArticle

24 Scopus citations

Abstract

Mutations in the B1 subunit of the multisubunit vacuolar ATPase cause autosomal-recessive distal renal tubular acidosis and sensorineural deafness. Here, we report a novel frameshift mutation that truncates the C-terminus of the human B1 subunit. This mutant protein failed to assemble with other subunits in the cytosol to form the complex that can be targeted to vesicular structures in mammalian cells. Loss of proton pump activity was demonstrated in a functional complementation assay in B-subunit null yeast. The mutation caused loss of a discreet C-terminal region critical for subunit interaction not related to the C-terminal PDZ motif. Co-expression studies failed to demonstrate dominant negative effects of this truncated mutant over wild-type B1. Analysis of 12 reported B1 subunit missense mutations showed one polymorphic allele had intact pump function, two point mutants had intact assembly but defective proton pumping, and the remaining nine had disrupted assembly with no pump function. One presumed polymorphic allele was actually an inactivating mutation. Our study shows that multiple mechanisms of pump dysfunction result from B1 subunit mutations with a common outcome being defective assembly. Polymorphisms of the B1 subunit in the general population may affect renal acidification and urinary chemistry.

Original languageEnglish (US)
Pages (from-to)1151-1158
Number of pages8
JournalKidney international
Volume73
Issue number10
DOIs
StatePublished - May 2008

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Keywords

  • Kidney stones
  • Mutation
  • Pump assembly
  • Renal tubular acidosis
  • Vacuolar type H-ATPase

ASJC Scopus subject areas

  • Nephrology

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