Molecular basis of decreased Kir4.1 function in SeSAME/EAST syndrome

David M. Williams, Coeli M.B. Lopes, Avia Rosenhouse-Dantsker, Heather L. Connelly, Alessandra Matavel, Jin O-Uchi, Elena McBeath, Daniel A. Gray

Research output: Contribution to journalArticlepeer-review

45 Scopus citations

Abstract

SeSAME/EAST syndrome is a channelopathy consisting of a hypokalemic, hypomagnesemic, metabolic alkalosis associated with seizures, sensorineural deafness, ataxia, and developmental abnormalities. This disease links to autosomal recessive mutations in KCNJ10, which encodes the Kir4.1 potassium channel, but the functional consequences of these mutations are not well understood. In Xenopus oocytes, all of the disease-associated mutant channels (R65P, R65P/R199X, G77R, C140R, T164I, and A167V/R297C) had decreased K + current (0 to 23% of wild-type levels). Immunofluorescence demonstrated decreased surface expression of G77R, C140R, and A167V expressed in HEK293 cells. When we coexpressed mutant and wild-type subunits to mimic the heterozygous state, R199X, C140R, and G77R currents decreased to 55, 40, and 20% of wild-type levels, respectively, suggesting that carriers of these mutations may present with an abnormal phenotype. Because Kir4.1 subunits can form heteromeric channels with Kir5.1, we coexpressed the aforementioned mutants with Kir5.1 and found that currents were reduced at least as much as observed when we expressed mutants alone. Reduction of pHi from approximately 7.4 to 6.8 significantly decreased currents of all mutants except R199X but did not affect wild-type channels. In conclusion, perturbed pH gating may underlie the loss of channel function for the disease-associated mutant Kir4.1 channels and may have important physiologic consequences.

Original languageEnglish (US)
Pages (from-to)2117-2129
Number of pages13
JournalJournal of the American Society of Nephrology
Volume21
Issue number12
DOIs
StatePublished - Dec 2010
Externally publishedYes

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