KCNH5 Gene

KCNH5 Gene

Overview

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">KCNH5 Gene</th>
</tr>
<tr>
<td class="label">Symbol</td>
<td><strong>KCNH5</strong></td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>KCNH5</td>
</tr>
<tr>
<td class="label">Type</td>
<td>Gene</td>
</tr>
<tr>
<td class="label">NCBI</td>
<td><a href="https://www.ncbi.nlm.nih.gov/gene/?term=KCNH5" target="_blank">Search NCBI</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>

KCNH5 (Potassium Voltage-Gated Channel Subfamily H Member 5) encodes the voltage-gated potassium channel EAG2 (ether-à-go-go 2), also known as Kv10.2 or hERG2[@warmke1996][@saganich2017]. This channel belongs to the EAG (ether-à-go-go) family of potassium channels and plays important roles in neuronal excitability, synaptic function, and cellular proliferation. In the context of neurodegenerative diseases, KCNH5/EAG2 is relevant for its roles in regulating neuronal firing patterns, synaptic transmission, and its expression patterns in brain regions affected by [Alzheimer's disease](/diseases/alzheimers-disease), [Parkinson's disease](/diseases/parkinsons-disease), and [epilepsy](/diseases/epilepsy)—a common comorbidity in neurodegenerative disorders[@zhang2022][@liu2023].

Gene and Protein Structure

Gene Organization

KCNH5 Gene

Overview

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">KCNH5 Gene</th>
</tr>
<tr>
<td class="label">Symbol</td>
<td><strong>KCNH5</strong></td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>KCNH5</td>
</tr>
<tr>
<td class="label">Type</td>
<td>Gene</td>
</tr>
<tr>
<td class="label">NCBI</td>
<td><a href="https://www.ncbi.nlm.nih.gov/gene/?term=KCNH5" target="_blank">Search NCBI</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>

KCNH5 (Potassium Voltage-Gated Channel Subfamily H Member 5) encodes the voltage-gated potassium channel EAG2 (ether-à-go-go 2), also known as Kv10.2 or hERG2[@warmke1996][@saganich2017]. This channel belongs to the EAG (ether-à-go-go) family of potassium channels and plays important roles in neuronal excitability, synaptic function, and cellular proliferation. In the context of neurodegenerative diseases, KCNH5/EAG2 is relevant for its roles in regulating neuronal firing patterns, synaptic transmission, and its expression patterns in brain regions affected by [Alzheimer's disease](/diseases/alzheimers-disease), [Parkinson's disease](/diseases/parkinsons-disease), and [epilepsy](/diseases/epilepsy)—a common comorbidity in neurodegenerative disorders[@zhang2022][@liu2023].

Gene and Protein Structure

Gene Organization

The KCNH5 gene is located on chromosome 14q23.1 and consists of 16 exons spanning approximately 20 kb of genomic DNA[@warmke1996]. It encodes a protein of 989 amino acids forming the core alpha subunit of the EAG2 potassium channel.

Protein Architecture

EAG2 contains several critical structural domains[@warmke1996][@saganich2017]:

• N-terminal Per-Arnt-Sim (PAS) domain: Senses voltage and redox state
• Voltage sensor domain (VSD): Segments S1-S4 detect membrane potential changes
• Pore domain: Segments S5-S6 form the K+ selectivity filter
• C-terminal cyclic nucleotide-binding homology domain (cNBHD): Modulates channel activity
• Leucine zipper motif: Facilitates tetramerization

Channel Complex

EAG2 forms functional channels as:

• Tetrameric assembly: Four alpha subunits form the pore
• Auxiliary subunits: May associate with beta subunits
• Splice variants: Multiple isoforms with distinct properties

Biological Functions

Neuronal Excitability

EAG2 regulates neuronal firing in several ways[@saganich2017][@zhang2022]:

• Repolarization: Mediates outward K+ current to reset membrane potential
• Firing pattern: Influences action potential shape and frequency
• Resting membrane potential: Contributes to baseline conductance
• Dendritic integration: Affects synaptic integration

Brain Region Expression

EAG2 shows distinct expression patterns:

• [Hippocampus](/brain-regions/hippocampus): High expression in CA1 pyramidal [neurons](/entities/neurons)
• [Cortex](/brain-regions/cortex): Layer-specific expression in pyramidal neurons
• Cerebellum: Purkinje cell expression
• Thalamus: Moderate expression in relay neurons
• Substantia nigra: Expression in dopaminergic neurons

Synaptic Function

EAG2 modulates synaptic transmission:

• Presynaptic terminals: Regulates vesicle release probability
• Postsynaptic responses: Shapes excitatory/inhibitory balance
• Plasticity: Affects [long-term potentiation](/mechanisms/long-term-potentiation) and depression

Cell Cycle and Proliferation

Outside the nervous system, EAG2 affects:

• Cell cycle progression: Controls G1/S transition
• Cellular proliferation: Aberrant expression in tumors
• Migration: Affects cell motility

Role in Neurological Diseases

Epilepsy

KCNH5 variants have been implicated in epilepsy[@zhang2022][@liu2023]:

• Loss-of-function mutations: Cause epilepsy phenotypes
• Channel dysfunction: Leads to hyperexcitability
• Therapeutic targeting: EAG2 modulators as anticonvulsants

• Temporal lobe epilepsy
• Febrile seizures
• Absence seizures

Alzheimer's Disease

In [Alzheimer's disease](/diseases/alzheimers-disease), EAG2 may play several roles[@palop2016]:

Neuronal Excitability Changes

• AD neurons show altered firing patterns
• EAG2 dysregulation contributes to network dysfunction
• Potassium channels as therapeutic targets

• [Aβ](/proteins/amyloid-beta) affects neuronal potassium channel function
• EAG2 expression altered in AD brain
• Possible direct protein-protein interactions

• EAG2 modulates synaptic plasticity
• Altered in AD-relevant circuits
• Contributes to cognitive decline

Parkinson's Disease

In [Parkinson's disease](/diseases/parkinsons-disease)[@surmeier2020]:

Basal Ganglia Circuitry

• EAG2 expressed in striatal neurons
• Modulates direct/indirect pathway activity
• Dopamine regulates channel expression

• EAG2 in substantia nigra pars compacta
• May affect neuron survival
• Potential therapeutic target

Psychiatric Disorders

EAG2 has been studied in:

• Schizophrenia: Altered expression in prefrontal cortex
• Bipolar disorder: Channel dysfunction hypotheses
• Autism spectrum disorders: Genetic association studies

Channel Gating and Modulation

Voltage Dependence

EAG2 has unique gating properties[@warmke1996][@saganich2017]:

• Activation: Slow voltage-dependent opening
• Deactivation: Rapid closure upon repolarization
• Inactivation: Minimal inactivation during sustained depolarization

Regulatory Mechanisms

Multiple factors modulate EAG2:

• Phosphorylation: PKA, PKC affect channel function
• Redox state: Oxidative stress modulates gating
• Lipids: Membrane lipid composition matters
• Temperature: Thermal sensitivity relevant for seizures

Pharmacology

EAG2 is targeted by several compounds:

• Astemizole: H1 antagonist blocks EAG2
• Terfenadine: Histamine antagonist with EAG2 block
• Clozapine: Atypical antipsychotic affects EAG2
• Dozens of research compounds: Tool compounds available

Therapeutic Implications

Epilepsy Treatment

EAG2 modulators as anticonvulsants[@zhang2022][@liu2023]:

• AST-001: Novel EAG2 activator
• Existing drugs: Mechanism includes EAG2 effects
• Combination therapy: Synergistic approaches

Neurodegeneration

Potential therapeutic approaches[@palop2016][@surmeier2020]:

• Channel openers: Enhance EAG2 function
• Selective modulators: Targeted compounds
• Gene therapy: Viral vector delivery

Side Effect Considerations

EAG2-targeting drugs must consider:

• Cardiac effects: hERG1 (KCNH2) similarity
• CNS penetration: [Blood-brain barrier](/entities/blood-brain-barrier)
• On-target toxicity: Neuronal excitability

Genetic Studies

Variant Spectrum

KCNH5 variants include[@zhang2022][@liu2023]:

• Missense mutations: Most common pathogenic type
• Truncating mutations: Loss-of-function
• Splice variants: Aberrant processing

Population Genetics

• Carrier frequency: Rare in population
• Founder effects: Some populations show clusters
• De novo mutations: Important in sporadic cases

Research Methods

Electrophysiology

Key experimental approaches[@warmke1996][@saganich2017]:

• Patch clamp: Two-electrode, whole-cell, inside-out
• Voltage protocols: Activation, inactivation curves
• Single-channel: Gating kinetics

Molecular Biology

• cRNA injection: Xenopus oocyte expression
• CRISPR/Cas9: Genetic manipulation
• RNAi: Knockdown studies

Model Systems

Research models include:

• Xenopus oocytes: Expression system
• HEK293 cells: Mammalian expression
• Primary neurons: Native channel studies
• Transgenic mice: In vivo models

Interactions with Other Channels

Potassium Channel Family

EAG2 interacts with other K+ channels:

• EAG1 (KCNH1): Closely related paralog
• ERG1 (KCNH2): Cardiac relevance
• Other Kv channels: Redundancy, compensation

Ion Channel Networks

In neurons, EAG2 coordinates with:

• Sodium channels: Action potential repolarization
• Calcium channels: Excitable coupling
• Chloride channels: Inhibitory modulation

Clinical Considerations

Genetic Testing

KCNH5 testing relevant for:

• Epilepsy: Diagnostic testing available
• Family screening: At-risk relatives
• Prenatal testing: In severe cases

Patient Management

Clinical care considerations:

• Seizure control: Antiepileptic drug selection
• Monitoring: EEG, clinical assessment
• Multidisciplinary care: Neurology, genetics

See Also

• [Alzheimer's disease](/diseases/alzheimers-disease)
• [Parkinson's disease](/diseases/parkinsons-disease)
• [epilepsy](/diseases/epilepsy)

External Links

• [PubMed](https://pubmed.ncbi.nlm.nih.gov/)
• [KEGG Pathways](https://www.genome.jp/kegg/pathway.html)

References