In silico modeling of the pore region of a KCNQ4 missense mutant from a patient with hearing loss

Abstract

BackgroundMutation of the voltage-gated potassium channel KCNQ4 causes DFNA2-type nonsyndromic autosomal dominant sensorineural hearing loss. KCNQ4 is expressed predominantly in the auditory sensory outer hair cells, which are critical for sound amplification.ResultsWe sequenced KCNQ4 from Japanese patients with sensorineural hearing loss, and identified a novel missense mutation encoding a Tyr270His located at the N-terminus of the highly conserved pore helix sequence. As this patient was not accessible to us and information about them was limited, we used molecular modeling to investigate whether this novel mutation is hypothetically pathogenic. A careful examination of an in silico structural model of the KCNQ4 pore region revealed that the Tyr270His mutation caused an alteration in the electrostatic surface potential of the pore helix.ConclusionWe propose two possible means by which the Tyr270His mutation causes hearing loss: a positively charged His270 side chain might enhance the helix dipole moment of the pore helix, thereby destabilizing the helix and/or the pore region, or it might disturb transport of K+ through the channel by electrostatic repulsion.

Molecular Modelling-Based Investigations of a Mutant Protein in Patients with Hearing Loss

“…Since patients with KCNQ4 mutations show progressive hearing loss, the development of a drug to improve the function of the KCNQ4 channel might attenuate the symptoms. We identified two disease-associated mutations of KCNQ4: in one, a tyrosine residue (Tyr270) is replaced with histidine (His); and in the other, there is a deletion, c.806_808delCCT, leading to a p.Ser260del located between S5 and the pore helix (PH) in the gene product of KCNQ4 [23,24]. We then generated a computational structural model of the KCNQ4 channel by referring to the crystal structure of the Shaker family K + channel, Kv1.2 [23,24].…”

“…We identified two disease-associated mutations of KCNQ4: in one, a tyrosine residue (Tyr270) is replaced with histidine (His); and in the other, there is a deletion, c.806_808delCCT, leading to a p.Ser260del located between S5 and the pore helix (PH) in the gene product of KCNQ4 [23,24]. We then generated a computational structural model of the KCNQ4 channel by referring to the crystal structure of the Shaker family K + channel, Kv1.2 [23,24]. In the following sections, we speculate about the molecular mechanism underlying hearing loss according to the basic quantum chemistry of a KCNQ4 channel formed with the Tyr270His (p.Y270H) and p.Ser260del (p.S269del) mutations and we discuss how two more severe mutationsp.Gly285Ser (p.G285S) [14] and p.Gly287Arg (p.G287R) [25]-might cause severe to profound hearing loss from a structural point of view.…”

“…Genomic DNA was extracted from blood samples via the Gentra Puregene Blood Kit (QIAGEN, Hamburg, Germany). PCR primers specific for KCNQ4 were designed in our laboratory [23].…”

Impaired surface expression and conductance of the KCNQ4 channel lead to sensorineural hearing loss

“…Over the last two decades, various pathogenic KCNQ4 mutations have been identified in DFNA2 patients (DFNA2 mutations) [7,15,[18][19][20][21][22][23][24][25][26][27][28][29][30][31]. Among them, the missense mutations L274H, W276S, L281S, G285C, G285S, G296S and G321S are loss-of-function mutations [7,19,29,32,33].…”

Distinct Roles of Molecular Chaperones HSP90α and HSP90β in the Biogenesis of KCNQ4 Channels

“…Mutations in the KCNQ4 gene cause progressive sensorineural hearing loss in the DFNA2 patients [2], [3], [6]. To date, more than fifteen pathogenic KCNQ4 mutations have been identified and the majority of these mutations lead to decreased cell surface expression and loss of KCNQ4 currents [3], [7]–[21]. Despite the significance of the KCNQ4 biogenesis, little is known about the molecular mechanisms that control the process, which hinders the development of strategies to prevent and treat hearing loss of DFNA2 patients.…”