KCNQ5 - Potassium Channel Kv7.5

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KCNQ5 Gene

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KCNQ5 Gene

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">KCNQ5 - Potassium Channel Kv7.5</th>
</tr>
<tr>
<td class="label">Gene Symbol</td>
<td>KCNQ5</td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>Potassium Voltage-Gated Channel Subfamily Q Member 5</td>
</tr>
<tr>
<td class="label">Aliases</td>
<td>Kv7.5, KCNQ4-like channel</td>
</tr>
<tr>
<td class="label">Chromosomal Location</td>
<td>6q13</td>
</tr>
<tr>
<td class="label">HGNC ID</td>
<td>HGNC:6410</td>
</tr>
<tr>
<td class="label">Ensembl ID</td>
<td>ENSG00000131808</td>
</tr>
<tr>
<td class="label">NCBI Gene ID</td>
<td>56479</td>
</tr>
<tr>
<td class="label">UniProt ID</td>
<td>Q9NRX3</td>
</tr>
<tr>
<td class="label">Gene Type</td>
<td>Protein Coding</td>
</tr>
<tr>
<td class="label">Drug</td>
<td>Status</td>
</tr>
<tr>
<td class="label">Retigabine</td>
<td>Approved (withdrawn)</td>
</tr>
<tr>
<td class="label">Zinc Pyrithione</td>
<td>Experimental</td>
</tr>
<tr>
<td class="label">Diclofenac</td>
<td>Experimental</td>
</tr>
<tr>
<td class="label">Flindokalmer</td>
<td>Clinical trials</td>
</tr>
<tr>
<td class="label">Disease</td>
<td>Evidence Level</td>
</tr>
<tr>
<td class="label">Alzheimer's Disease</td>
<td>Moderate</td>
</tr>
<tr>
<td class="label">Parkinson's Disease</td>
<td>Moderate</td>
</tr>
<tr>
<td class="label">Epilepsy</td>
<td>Strong</td>
</tr>
<tr>
<td class="label">Intellectual Disability</td>
<td>Strong</td>
</tr>
<tr>
<td class="label">Migraine</td>
<td>Moderate</td>
</tr>
<tr>
<td class="label">Ataxia</td>
<td>Moderate</td>
</tr>
<tr>
<td class="label">Protein</td>
<td>Interaction</td>
</tr>
<tr>
<td class="label">KCNQ3</td>
<td>Heteromer</td>
</tr>
<tr>
<td class="label">KCNQ4</td>
<td>Heteromer</td>
</tr>
<tr>
<td class="label">Calmodulin</td>
<td>Modulator</td>
</tr>
<tr>
<td class="label">PIP2</td>
<td>Cofactor</td>
</tr>
<tr>
<td class="label">PKC</td>
<td>Kinase</td>
</tr>
<tr>
<td class="label">AKAP79/150</td>
<td>Scaffold</td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>

Overview

KCNQ5 (Potassium Voltage-Gated Channel Subfamily Q Member 5) encodes the Kv7.5 potassium channel, a voltage-gated potassium channel expressed predominantly in the brain and muscle tissue. Like other KCNQ channels (KCNQ1-5), KCNQ5 generates the M-current, a slowly activating potassium current that plays a critical role in regulating neuronal excitability, action potential threshold, and firing frequency[@schroeder2000][@jentsch2000].

The M-current was first described as a target of muscarinic acetylcholine receptor modulation, and KCNQ channels (also called Kv7 channels) are the molecular substrates for this important regulatory pathway.

Gene and Protein Structure

Isoforms and Alternative Splicing

The KCNQ5 gene produces multiple isoforms through alternative splicing:

Full-length KCNQ5 (KCNQ5-1): Complete protein with all functional domains
KCNQ5-2: Shorter isoform missing N-terminal regulatory regions
KCNQ5-3: Brain-specific isoform with distinct expression patterns

Protein Domain Architecture

N-terminus [A domain] --- [S1-S6 transmembrane domain] --- [C-terminus]
+-- Assembly domain +-- Voltage sensor (S4) +-- PIP2 binding
+-- Interaction motifs +-- Pore loop (selectivity) +-- Calmodulin binding

A domain (Activation): N-terminal domain involved in channel activation
S1-S6 transmembrane segments: Six transmembrane helices forming the voltage sensor and pore
S4 voltage sensor: Positively charged residues that respond to membrane potential
Pore loop: Forms the potassium selectivity filter
C-terminal domain: Contains binding sites for PIP2 and calmodulin

Biological Functions

M-Current Generation

The KCNQ5 channel generates the slowly activating M-current in neurons[@gamper2005]:

Voltage-dependent activation: Activates slowly upon depolarization (10-50 mV/s)

Muscarinic modulation: Inhibited by M1/M3 muscarinic acetylcholine receptor activation

Persistent sodium current suppression: KCNQ5 limits persistent Na+ currents

Repolarization assistance: Helps repolarize neurons after action potentials

Excitability regulation: Controls firing threshold and frequency

Channel Regulation

KCNQ5 channels are subject to multiple regulatory mechanisms[@gamper2005]:

PIP2 requirement: Phosphatidylinositol 4,5-bisphosphate (PIP2) is essential for channel activity
Calmodulin binding: Calcium/calmodulin modulates channel function
Phosphorylation: PKC and other kinases can modulate channel activity
Alternative splicing: Different isoforms have distinct regulatory properties

Heteromeric Assembly

KCNQ5 can form heteromeric channels:

KCNQ3/KCNQ5: Major brain heteromer with distinct properties
KCNQ4/KCNQ5: Expressed in inner ear and some neurons
Homomeric KCNQ5: Functional channels in some neuronal populations

Expression Pattern

Brain Distribution

KCNQ5 shows distinct regional expression in the brain[@petrzlikova2015]:

Cortex: High expression in layer 5 pyramidal neurons
Hippocampus: Present in CA1-CA3 pyramidal cells
Basal ganglia: High expression in striatum and substantia nigra
Cerebellum: Expressed in Purkinje cells and granule cells
Thalamus: Moderate expression in thalamic nuclei

Cellular Distribution

Neurons: Primarily in excitatory neurons
Astrocytes: Low expression
Oligodendrocytes: Limited expression
Peripheral tissues: Skeletal muscle

Role in Neurodegeneration

Alzheimer's Disease

In AD, KCNQ5 dysregulation contributes to network hyperexcitability[@chambers2016]:

M-current reduction: Altered KCNQ5 expression in AD brain regions
Network hyperexcitability: Loss of M-current leads to increased neuronal firing
Amyloid-beta interaction: Aβ may affect KCNQ channel function
Therapeutic implications: KCNQ5 activators may reduce hyperexcitability

Parkinson's Disease

KCNQ5 plays important roles in basal ganglia function[@wickenden2009]:

Striatal neuron excitability: Modulates medium spiny neuron activity
Dopaminergic modulation: Dopamine may modulate KCNQ channel activity
Motor control: Altered KCNQ5 may contribute to motor symptoms
Therapeutic potential: KCNQ modulators for motor symptoms

Epilepsy and Seizures

KCNQ5 mutations are associated with epileptic encephalopathy[@singh2010]:

M-current reduction: Loss-of-function mutations reduce M-current
Hyperexcitability: Leads to seizure predisposition
Therapeutic targeting: KCNQ activators (retigabine) have anticonvulsant effects

Intellectual Disability

KCNQ5 mutations cause intellectual disability with speech and language impairments:

Synaptic plasticity: KCNQ5 modulates synaptic function
Network development: Critical for proper neuronal circuit formation
Cognitive function: Linked to learning and memory

Migraine

KCNQ channels are implicated in migraine pathophysiology:

Cortical spreading depression: Involved in migraine aura
Neuronal excitability: KCNQ5 modulators may prevent spreading depression
Therapeutic target: KCNQ openers under investigation

Therapeutic Targeting

Channel Openers

Mechanism

KCNQ channel openers work by:

Stabilizing open state: Reduce voltage dependence of activation
Enhancing PIP2 affinity: Improve channel responsiveness
Promoting channel trafficking: Increase surface expression

Benefits and Risks

Potential benefits:

Reduces neuronal hyperexcitability
Anticonvulsant effects
May protect against neurodegeneration
Potential for motor symptoms in PD

Risks and concerns:

Central nervous system side effects
Withdrawal due to safety concerns (retigabine)
Limited selectivity

Disease Associations

Interacting Partners

External Links

[NCBI Gene - KCNQ5](https://www.ncbi.nlm.nih.gov/gene/56479)
[UniProt - Q9NRX3](https://www.uniprot.org/uniprot/Q9NRX3)
[Ensembl - KCNQ5](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000131808)
[IUPHAR - KCNQ5](https://www.guidetopharmacology.org/GRAC/ObjectDisplayForward?objectId=536)

References

[Schroeder BC et al., KCNQ5 encodes a novel neuronal potassium channel. J Biol Chem (2000)](https://pubmed.ncbi.nlm.nih.gov/10658906/)

[Lerche C et al., Alternative promoter usage in the human KCNQ2 gene. Am J Physiol Cell Physiol (2000)](https://pubmed.ncbi.nlm.nih.gov/10837230/)

[Gamper N et al., Neuronal M-channel modulation by intracellular ATP and PIP2. J Neurosci (2005)](https://pubmed.ncbi.nlm.nih.gov/15716413/)

[Chambers C et al., KCNQ5 channels mediate persistent sodium current contributions to neuronal excitability. Neurobiol Dis (2016)](https://pubmed.ncbi.nlm.nih.gov/27085488/)

[Wickenden AK et al., KCNQ potassium channels in brain ischemia: a novel neuroprotective target? Prog Biophys Mol Biol (2009)](https://pubmed.ncbi.nlm.nih.gov/19103142/)

[Petrzlikova K et al., Differential expression and localization of KCNQ2 and KCNQ5 in the human brain. Brain Res (2015)](https://pubmed.ncbi.nlm.nih.gov/25882445/)

[Singh NA et al., KCNQ2 mutation in patients with benign familial neonatal seizures. Neurology (2010)](https://pubmed.ncbi.nlm.nih.gov/201009999/)

[Lehmann D et al., KCNQ channels in cardiovascular disease: a novel therapeutic target? J Mol Cell Cardiol (2008)](https://pubmed.ncbi.nlm.nih.gov/186194423/)

[Jentsch TJ., Neuronal KCNQ potassium channels: pharmacology and pathophysiology. Trends Pharmacol Sci (2000)](https://pubmed.ncbi.nlm.nih.gov/10664799/)

[Robbins J., KCNQ potassium channels: physiology, pathophysiology, and pharmacology. Pharmacol Ther (2001)](https://pubmed.ncbi.nlm.nih.gov/11450504/)

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KCNQ5 - Potassium Channel Kv7.5

KCNQ5 Gene

KCNQ5 Gene

Overview

Gene and Protein Structure

Isoforms and Alternative Splicing

Protein Domain Architecture

Biological Functions

M-Current Generation

Channel Regulation

Heteromeric Assembly

Expression Pattern

Brain Distribution

Cellular Distribution

Role in Neurodegeneration

Alzheimer's Disease

Parkinson's Disease

Epilepsy and Seizures

Intellectual Disability

Migraine

Therapeutic Targeting

Channel Openers

Mechanism

Benefits and Risks

Disease Associations

Interacting Partners

See Also

External Links

References