A novel KCNQ4 pore-region mutation (p.G296S) causes deafness by impairing cell-surface channel expression.
Mutations in the potassium channel gene KCNQ4 underlie DFNA2, a subtype of autosomal dominant progressive, high-frequency hearing loss. Based on a phenotype-guided mutational screening we have identified a novel mutation c.886G>A, leading to the p.G296S substitution in the pore region of KCNQ4 channel. The possible impact of this mutation on total KCNQ4 protein expression, relative surface expression and channel function was investigated. When the G296S mutant was expressed in Xenopus oocytes, electrophysiological recordings did not show voltage-activated K(+) currents. The p.G296S mutation impaired KCNQ4 channel activity in two manners. It greatly reduced surface expression and, secondarily, abolished channel function. The deficient expression at the cell surface membrane was further confirmed in non-permeabilized NIH-3T3 cells transfected with the mutant KCNQ4 tagged with the hemagglutinin epitope in the extracellular S1-S2 linker. Co-expression of mutant and wild type KCNQ4 in oocytes was performed to mimic the heterozygous condition of the p.G296S mutation in the patients. The results showed that the G296S mutant exerts a strong dominant-negative effect on potassium currents by reducing the wild type KCNQ4 channel expression at the cell surface. This is the first study to identify a trafficking-dependent dominant mechanism for the loss of KCNQ4 channel function in DFNA2.
Mencía
Angeles
A
Unidad de Genética Molecular, Hospital Ramón y Cajal, Carretera de Colmenar Km 9, 28034, Madrid, Spain.
González-Nieto
Daniel
D
Modamio-Høybjør
Silvia
S
Etxeberría
Ainhoa
A
Aránguez
Gracia
G
Salvador
Nieves
N
Del Castillo
Ignacio
I
Villarroel
Alvaro
A
Moreno
Felipe
F
Barrio
Luis
L
Moreno-Pelayo
Miguel Angel
MA
D016475:3T3 Cells; D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism; D003638:Deafness / Q000235:genetics*; D005260:Female; D006801:Humans; D015640:Ion Channel Gating; D051656:KCNQ Potassium Channels / Q000235:genetics*; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D018408:Patch-Clamp Techniques; D010375:Pedigree; D017386:Sequence Homology, Amino Acid; D014982:Xenopus laevis
D051656:KCNQ Potassium Channels; C117367:KCNQ4 protein, human