Functional characterization of a partial loss-of-function mutation of the epithelial sodium channel (ENaC) associated with atypical cystic fibrosis

Regina Huber, Bettina Krueger, Alexei Diakov, Judit Korbmacher, Silke Haerteis, Jürgen Einsiedel, Peter Gmeiner, Abul Azad, Harry Cuppens, Jean Jaques Cassiman, Christoph Korbmacher, Robert Rauh

Research output: Contribution to journalArticlepeer-review

21 Scopus citations

Abstract

Loss-of-function mutations of the epithelial sodium channel (ENaC) may contribute to pulmonary symptoms resembling those of patients with atypical cystic fibrosis (CF). Recently, we identified a loss-of-function mutation in the α-subunit of ENaC (αF61L) in an atypical CF patient without mutations in CFTR. To investigate the functional effect of this mutation, we expressed human wild-type αβγ-ENaC or mutant α F61L βγ-ENaC in Xenopus laevis oocytes. The αF61L mutation reduced the ENaC mediated whole-cell currents by ñ90%. In contrast, the mutation decreased channel surface expression only by ñ40% and did not alter the single-channel conductance. These findings indicate that the major effect of the mutation is a reduction of the average channel open probability (P o ). This was confirmed by experiments using the βS520C mutant ENaC which can be converted to a channel with a P o of nearly one, and by experiments using chymotrypsin to proteolytically activate the channel. These experiments revealed that the mutation reduced the average P o of ENaC by ñ75%. Na + self inhibition of the mutant channel was significantly enhanced, but the observed effect was too small to account for the large reduction in average channel P o . The ENaC-activator S3969 partially rescued the loss-of-function phenotype of the αF61L mutation. We conclude that the αF61L mutation may contribute to respiratory symptoms in atypical CF patients.

Original languageEnglish (US)
Pages (from-to)145-158
Number of pages14
JournalCellular Physiology and Biochemistry
Volume25
Issue number1
DOIs
StatePublished - 2010
Externally publishedYes

Keywords

  • Electrophysiology
  • Heterologous expression
  • Ion channel
  • Xenopus laevis oocytes

ASJC Scopus subject areas

  • Physiology

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