KCNQ4 Membrane Protein Introduction

Introduction of KCNQ4

KCNQ4 is encoded by the KCNQ4 gene which is located on 1p34 in human. The molecular mass of KCNQ4 is about 77 kDa. It belongs to the potassium channel family, the members of which are wildly expressed ion channels. KCNQ4 is mainly expressed in the outer sensory hair cells of the cochlea, and it also can be slightly found in heart, brain and skeletal muscle. It has been proved that KCNQ4 can be phosphorylated at Thr552.

Function of KCNQ4 Membrane Protein

KCNQ4 is a potassium channel which was found in sensory outer hair cells in 1999. At the same time, it was revealed that the mutation of KCNQ4 is associated with a form of nonsyndromic dominant deafness, DFNA2, and the pathogenic mutation can cause trafficking deficiency and loss of KCNQ4 currents. Besides, KCNQ4 can regulate neuronal excitability, and plays an important role in regulating the excitability of sensory cells of the cochlea. KCNQ4 also owns delayed rectifier potassium channel activity and calmodulin binding activity. It can form heteromultimers with KCNQ3. On the other hand, KCNQ4 can be detected in the peripheral nerve endings of cutaneous Meissner corpuscle mechanoreceptors and rapidly adapts hair follicle. KCNQ4 becomes a specific molecular marker for hair follicle afferents. In addition, KCNQ4 is fund to express throughout the vasculature and regulate arterial contraction. MicroRNA-153 plays a role in vascular dysfunction in hypertension by targeting KCNQ4.

Fig.1 Model for the calcium-dependent interactions of neuronal KCNQ channels and CaM. (Xu, 2012)

Application of KCNQ4 Membrane Protein in Literature

1. Carr G., et al. MicroRNA-153 targeting of KCNQ4 contributes to vascular dysfunction in hypertension. Cardiovascular Research. 2016, 112(2):581-589. PubMed ID: 27389411
   
   

   In order to make clear the mechanism that KCNQ4 controls arterial contraction and is compromised in hypertension. Authors in this article investigate whether miRs regulate the expression of KCNQ4. At last, they find that miR153 contributes to the hypertensive state by targeting KCNQ4 in an animal model of hypertension.

2. Wang H., et al. Targeted high-throughput sequencing identifies pathogenic mutations in KCNQ4 in two large Chinese families with autosomal dominant hearing loss. PLoS One. 2014, 9(8): e103133. PubMed ID: 25116015
   
   

   Autosomal dominant non-syndromic hearing loss (ADNSHL) is a highly heterogeneous disease. KCNQ4 is one of its disease-causing genes. Through high-throughput sequencing, authors in this article find new mutations of KCNQ4 from two Chinese families who suffer from autosomal dominant hearing loss.

3. Heidenreich M., et al. KCNQ4 K⁺ channels tune mechanoreceptors for normal touch sensation in mouse and man. Nature Neuroscience. 2011, 15(1):138-145. PubMed ID: 22101641
   
   

   The article reveals that KCNQ4 can be detected in the peripheral nerve endings of cutaneous Meissner corpuscle mechanoreceptors and rapidly adapts hair follicle. And KCNQ4 become a specific molecular marker for rapidly adapting Meissner and a subset of hair follicle afferents.

4. Xu Q., et al. Structure of a Ca (2+)/CaM: Kv7.4 (KCNQ4) B-helix complex provides insight into M current modulation. J Mol Biol. 2012, 425(2):378-94. PubMed ID: 23178170
   
   

   Calmodulin (CaM) can regulate (KCNQx) voltage-gated potassium channels, but the structural details of the interaction are not very clear before this article. Authors in this article find that both apo-CaM and Ca²⁺/CaM bind to the C-terminal tail of KCNQ4. And they establish a model for modulation of neuronal Kv7 channels.

5. Hosseinzadeh Z., et al. Downregulation of KCNQ4 by Janus kinase 2. Journal of Membrane Biology. 2013, 246(4):335-341. PubMed ID: 23543186
   
   

   Janus kinase-2 (JAK2) is an important protein kinase in signal transduction. Authors in this article find that JAK2 downregulates KCNQ4 activity and thus counteracts K (+) exit, an effect which may contribute to cell volume regulation.

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Reference

1. Xu Q, et al. (2012). Structure of a Ca (2+)/CaM: Kv7.4 (KCNQ4) B-helix complex provides insight into M current modulation. Journal of molecular biology. 425(2): 378-94.

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