title: Molecular basis of decreased Kir4.1 function in SeSAME/EAST syndrome.
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 pH(i) 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.
authors.affiliation: Department of Medicine, Nephrology Division, University of Rochester, Rochester, New York 14642, USA.
authors.forename: David M
authors.initials: DM
authors.lastname: Williams
authors.forename: Coeli M B
authors.initials: CM
authors.lastname: Lopes
authors.forename: Avia
authors.initials: A
authors.lastname: Rosenhouse-Dantsker
authors.forename: Heather L
authors.initials: HL
authors.lastname: Connelly
authors.forename: Alessandra
authors.initials: A
authors.lastname: Matavel
authors.forename: Jin
authors.initials: J
authors.lastname: O-Uchi
authors.forename: Elena
authors.initials: E
authors.lastname: McBeath
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Gray
mesh_terms: D000471:Alkalosis / Q000235:genetics / Q000503:physiopathology; D000704:Analysis of Variance; D000818:Animals; D001259:Ataxia / Q000235:genetics / Q000503:physiopathology; D005455:Fluorescent Antibody Technique; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels / Q000235:genetics*; D020022:Genetic Predisposition to Disease; D057809:HEK293 Cells / Q000378:metabolism; D006319:Hearing Loss, Sensorineural / Q000235:genetics* / Q000503:physiopathology; D006801:Humans; D007008:Hypokalemia / Q000235:genetics / Q000503:physiopathology; D015151:Immunoblotting; D008607:Intellectual Disability / Q000235:genetics / Q000503:physiopathology; D051662:Kv1.1 Potassium Channel / Q000235:genetics*; D023421:Models, Animal; D008967:Molecular Biology; D009154:Mutation; D009865:Oocytes; D012640:Seizures / Q000235:genetics* / Q000503:physiopathology; D013577:Syndrome; D014982:Xenopus laevis
chemical_list: D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; D051662:Kv1.1 Potassium Channel