title: KCNJ10 gene mutations causing EAST syndrome (epilepsy, ataxia, sensorineural deafness, and tubulopathy) disrupt channel function.
abstract: Mutations of the KCNJ10 (Kir4.1) K(+) channel underlie autosomal recessive epilepsy, ataxia, sensorineural deafness, and (a salt-wasting) renal tubulopathy (EAST) syndrome. We investigated the localization of KCNJ10 and the homologous KCNJ16 in kidney and the functional consequences of KCNJ10 mutations found in our patients with EAST syndrome. Kcnj10 and Kcnj16 were found in the basolateral membrane of mouse distal convoluted tubules, connecting tubules, and cortical collecting ducts. In the human kidney, KCNJ10 staining was additionally observed in the basolateral membrane of the cortical thick ascending limb of Henle's loop. EM of distal tubular cells of a patient with EAST syndrome showed reduced basal infoldings in this nephron segment, which likely reflects the morphological consequences of the impaired salt reabsorption capacity. When expressed in CHO and HEK293 cells, the KCNJ10 mutations R65P, G77R, and R175Q caused a marked impairment of channel function. R199X showed complete loss of function. Single-channel analysis revealed a strongly reduced mean open time. Qualitatively similar results were obtained with coexpression of KCNJ10/KCNJ16, suggesting a dominance of KCNJ10 function in native renal KCNJ10/KCNJ16 heteromers. The decrease in the current of R65P and R175Q was mainly caused by a remarkable shift of pH sensitivity to the alkaline range. In summary, EAST mutations of KCNJ10 lead to impaired channel function and structural changes in distal convoluted tubules. Intriguingly, the metabolic alkalosis present in patients carrying the R65P mutation possibly improves residual function of KCNJ10, which shows higher activity at alkaline pH.
authors.affiliation: Department of Physiology, University of Regensburg, 93053 Regensburg, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Reichold
authors.forename: Anselm A
authors.initials: AA
authors.lastname: Zdebik
authors.forename: Evelyn
authors.initials: E
authors.lastname: Lieberer
authors.forename: Markus
authors.initials: M
authors.lastname: Rapedius
authors.forename: Katharina
authors.initials: K
authors.lastname: Schmidt
authors.forename: Sascha
authors.initials: S
authors.lastname: Bandulik
authors.forename: Christina
authors.initials: C
authors.lastname: Sterner
authors.forename: Ines
authors.initials: I
authors.lastname: Tegtmeier
authors.forename: David
authors.initials: D
authors.lastname: Penton
authors.forename: Thomas
authors.initials: T
authors.lastname: Baukrowitz
authors.forename: Sally-Anne
authors.initials: SA
authors.lastname: Hulton
authors.forename: Ralph
authors.initials: R
authors.lastname: Witzgall
authors.forename: Bruria
authors.initials: B
authors.lastname: Ben-Zeev
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: Howie
authors.forename: Robert
authors.initials: R
authors.lastname: Kleta
authors.forename: Detlef
authors.initials: D
authors.lastname: Bockenhauer
authors.forename: Richard
authors.initials: R
authors.lastname: Warth
mesh_terms: D000015:Abnormalities, Multiple / Q000235:genetics*; D000818:Animals; D001259:Ataxia; D002460:Cell Line; D004827:Epilepsy; D006319:Hearing Loss, Sensorineural; D006801:Humans; D007674:Kidney Diseases; D007686:Kidney Tubules, Distal / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D020125:Mutation, Missense; D024661:Potassium Channels, Inwardly Rectifying / Q000032:analysis / Q000235:genetics*; D013577:Syndrome; D014162:Transfection; D000098854:Kcnj10 Channel
chemical_list: D000098854:Kcnj10 Channel; D024661:Potassium Channels, Inwardly Rectifying