HCN4 — Hyperpolarization-Activated Cyclic Nucleotide-Gated Channel 4

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HCN4 — Hyperpolarization-Activated Cyclic Nucleotide-Gated Channel 4

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HCN4 Gene - Hyperpolarization-Activated Cyclic Nucleotide-Gated Channel 4

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">HCN4 — Hyperpolarization-Activated Cyclic Nucleotide-Gated Channel 4</th>
</tr>
<tr>
<td class="label">Gene Symbol</td>
<td>HCN4</td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>Hyperpolarization-Activated Cyclic Nucleotide-Gated Channel 4</td>
</tr>
<tr>
<td class="label">Chromosomal Location</td>
<td>15q24.1</td>
</tr>
<tr>
<td class="label">Genomic Coordinates</td>
<td>Chr15:73,257,977-73,314,655 (GRCh38)</td>
</tr>
<tr>
<td class="label">NCBI Gene ID</td>
<td>80216</td>
</tr>
<tr>
<td class="label">OMIM ID</td>
<td>607272</td>
</tr>
<tr>
<td class="label">Ensembl ID</td>
<td>ENSG00000138668</td>
</tr>
<tr>
<td class="label">UniProt ID</td>
<td>Q9Y3X5</td>
</tr>
<tr>
<td class="label">RefSeq mRNA</td>
<td>NM_001194</td>
</tr>
<tr>
<td class="label">Protein Length</td>
<td>919 amino acids</td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td>Sinus Bradycardia, Brugada Syndrome, Alzheimer's Disease, Epilepsy</td>
</tr>
<tr>
<td class="label">Disease</td>
<td>Mutation Type</td>
</tr>
<tr>
<td class="label">Sinus Bradycardia</td>
<td>Loss-of-function</td>
</tr>
<tr>
<td class="label">Brugada Syndrome</td>
<td>Mixed</td>
</tr>
<tr>
<td class="label">Sick Sinus Syndrome</td>
<td>Loss-

...

HCN4 Gene - Hyperpolarization-Activated Cyclic Nucleotide-Gated Channel 4

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">HCN4 — Hyperpolarization-Activated Cyclic Nucleotide-Gated Channel 4</th>
</tr>
<tr>
<td class="label">Gene Symbol</td>
<td>HCN4</td>
</tr>
<tr>
<td class="label">Full Name</td>
<td>Hyperpolarization-Activated Cyclic Nucleotide-Gated Channel 4</td>
</tr>
<tr>
<td class="label">Chromosomal Location</td>
<td>15q24.1</td>
</tr>
<tr>
<td class="label">Genomic Coordinates</td>
<td>Chr15:73,257,977-73,314,655 (GRCh38)</td>
</tr>
<tr>
<td class="label">NCBI Gene ID</td>
<td>80216</td>
</tr>
<tr>
<td class="label">OMIM ID</td>
<td>607272</td>
</tr>
<tr>
<td class="label">Ensembl ID</td>
<td>ENSG00000138668</td>
</tr>
<tr>
<td class="label">UniProt ID</td>
<td>Q9Y3X5</td>
</tr>
<tr>
<td class="label">RefSeq mRNA</td>
<td>NM_001194</td>
</tr>
<tr>
<td class="label">Protein Length</td>
<td>919 amino acids</td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td>Sinus Bradycardia, Brugada Syndrome, Alzheimer's Disease, Epilepsy</td>
</tr>
<tr>
<td class="label">Disease</td>
<td>Mutation Type</td>
</tr>
<tr>
<td class="label">Sinus Bradycardia</td>
<td>Loss-of-function</td>
</tr>
<tr>
<td class="label">Brugada Syndrome</td>
<td>Mixed</td>
</tr>
<tr>
<td class="label">Sick Sinus Syndrome</td>
<td>Loss-of-function</td>
</tr>
<tr>
<td class="label">Atrial Fibrillation</td>
<td>Mixed</td>
</tr>
<tr>
<td class="label">Condition</td>
<td>Evidence</td>
</tr>
<tr>
<td class="label">Epilepsy</td>
<td>Moderate</td>
</tr>
<tr>
<td class="label">Alzheimer's Disease</td>
<td>Moderate</td>
</tr>
<tr>
<td class="label">Autism Spectrum Disorder</td>
<td>Limited</td>
</tr>
<tr>
<td class="label">Compound</td>
<td>Target</td>
</tr>
<tr>
<td class="label">Ivabradine</td>
<td>HCN (If)</td>
</tr>
<tr>
<td class="label">Zatebradine</td>
<td>HCN</td>
</tr>
<tr>
<td class="label">AL-208</td>
<td>HCN</td>
</tr>
</table>

Overview

Mermaid diagram (expand to render)

The HCN4 gene encodes Hyperpolarization-Activated Cyclic Nucleotide-Gated Channel 4 (HCN4), a member of the hyperpolarization-activated cyclic nucleotide-gated (HCN) channel family. HCN channels are voltage-gated ion channels that generate the "funny current" (If), characterized by activation upon membrane hyperpolarization and modulation by cyclic nucleotides (cAMP). While HCN4 is best known for its critical role in cardiac pacemaker activity in the sinoatrial node, it is also expressed in various brain regions where it contributes to neuronal excitability, rhythmic activity, and synaptic integration. This page provides comprehensive information about the HCN4 gene, its protein structure, function, and relevance to neurodegenerative diseases and epilepsy. [@biel2010]

Introduction

The HCN channel family consists of four members (HCN1-4) in mammals, each with distinct biophysical properties, expression patterns, and physiological functions. HCN4 is the isoform with the slowest activation kinetics and highest cAMP sensitivity, making it particularly important for setting the rate of rhythmic firing in pacemaker cells. In the brain, HCN4 is expressed in several regions including the thalamus, [hippocampus](/brain-regions/hippocampus), [cortex](/brain-regions/cortex), and cerebellum, where it participates in neuronal network oscillations and sensory processing. [@difrancesco2013]

The importance of HCN4 in both cardiac and neuronal function makes it a key player in understanding how ion channel dysfunction contributes to disease. HCN4 mutations are associated with cardiac arrhythmias (sinus bradycardia, Brugada syndrome), while altered HCN channel function has been implicated in epilepsy, Alzheimer's disease, and other neurological conditions. [@notomi2010]

Gene Overview

Protein Structure

HCN4 is a transmembrane protein that forms homotetrameric ion channels. Each subunit contains:

Transmembrane Architecture

Six transmembrane segments (S1-S6): Common to voltage-gated ion channels
S4 segment: Voltage sensor containing positively charged residues
S5-S6 pore region: Forms the ion conduction pathway
Cyclic nucleotide-binding domain (CNBD): Located at the C-terminus

Domain Features

Voltage Sensor Domain (VSD)

S1-S4 segments form the voltage-sensing domain
S4 contains positively charged arginine residues that move upon hyperpolarization
Gating charge movement couples membrane voltage changes to channel opening

Pore Domain

S5-S6 segments form the pore
P-loop between S5 and S6 contains the selectivity filter
HCN channels are permeable to both Na+ and K+ (non-selective)

Cyclic Nucleotide-Binding Domain (CNBD)

Located at the C-terminus
Binds cAMP and cGMP
Binding accelerates channel activation (positive shift in voltage dependence)
HCN4 has the highest cAMP sensitivity among HCN isoforms

Quaternary Structure

Functional channels are tetramers of HCN4 subunits
Each subunit can form homomers or heteromers with other HCN isoforms
Heteromeric channels combine properties of constituent subunits

Normal Function

Biophysical Properties

Gating Kinetics

Activation: Slow activation upon hyperpolarization (time constant ~100-300 ms)
Deactivation: Slow deactivation upon depolarization
Voltage range: Activates around -50 to -90 mV
Reversal potential: Around -30 to -40 mV (due to mixed Na+/K+ permeability)

Ion Permeation

Permeable to Na+ and K+ (PNa/PK ≈ 0.2-0.4)
Conduction is relatively poor compared to other voltage-gated channels
Single channel conductance: ~1 pS for HCN4

Modulation

Cyclic Nucleotides

cAMP: Accelerates activation, shifts activation curve positive by ~10-15 mV
cGMP: Similar but weaker effect
Protein kinase A (PKA) phosphorylation can modulate channel activity

Other Modulators

Phosphatidylinositol 4,5-bisphosphate (PIP2): Required for channel activity
Voltage: Direct voltage-dependent gating
Temperature: Q10 ≈ 3-4 (strong temperature dependence)

Physiological Roles

Cardiac Pacemaker (Primary Role)

Generates If current in sinoatrial node cells
Sets the intrinsic heart rate
Critical for automaticity in cardiac conduction system

Neuronal Function

Thalamic oscillations: Contributes to burst firing in thalamocortical [neurons](/entities/neurons)
Hippocampal rhythm: Modulates pyramidal neuron excitability
Cerebellar function: Involved in cerebellar oscillations
Synaptic integration: Influences dendritic integration of synaptic inputs

Role in Neurodegeneration

Alzheimer's Disease

HCN Channel Dysfunction in AD

HCN channel expression and function are altered in AD brain
If current is reduced in cortical neurons from AD models
Contributes to neuronal hyperexcitability observed in AD

Mechanisms

[Aβ](/proteins/amyloid-beta) accumulation affects HCN channel trafficking and function
[Tau](/proteins/tau) pathology disrupts HCN channel localization
Altered cAMP signaling affects HCN modulation

Neuronal Network Effects

Impaired HCN function disrupts neuronal network oscillations
Contributes to cognitive deficits and epileptiform activity
May explain increased epilepsy risk in AD patients

Epilepsy

HCN Dysfunction in Epilepsy

HCN1 and HCN4 expression altered in epileptic tissue
Reduced HCN current contributes to neuronal hyperexcitability
Mutations in HCN4 associated with some forms of epilepsy

Therapeutic Implications

HCN channel modulators are being investigated as antiepileptic drugs
Drugs that enhance HCN current may reduce seizure frequency
Specific targeting of HCN4 in the brain is challenging

Parkinson's Disease

Basal Ganglia Function

HCN channels modulate striatal neuron excitability
Altered HCN function may contribute to basal ganglia dysfunction
Deep brain stimulation affects HCN channel activity

Potential Role

Some studies suggest HCN modulators may have therapeutic potential
More research needed on HCN4 specifically

Other Neurological Conditions

Migraine

HCN channels implicated in cortical spreading depression
HCN4 may be involved in trigeminal nociception

Neuropathic Pain

HCN channel blockers can reduce pain in animal models
Different HCN isoforms have different roles in pain pathways

Disease Associations

Cardiac Diseases

Neurological Associations

Therapeutic Targeting

Drug Development

Challenges

[Blood-brain barrier](/entities/blood-brain-barrier) penetration
Isoform selectivity (HCN1 vs HCN4)
Cardiac side effects

Key Publications

[Identification and functional characterization of HCN4, a novel member of the HCN channel family. J Biol Chem. 2000](https://pubmed.ncbi.nlm.nih.gov/10625657/)

[HCN channels: From genes to function in the heart. Prog Biophys Mol Biol. 2002](https://pubmed.ncbi.nlm.nih.gov/11997277/)

[HCN channels in neurons: analysis, regulation, and role in synaptic integration. Nat Rev Neurosci. 2010](https://pubmed.ncbi.nlm.nih.gov/20869440/)

[HCN4 and cardiac arrhythmia. J Am Coll Cardiol. 2018](https://pubmed.ncbi.nlm.nih.gov/29471939/)

[HCN channel dysfunction in Alzheimer's disease. J Neurosci. 2019](https://pubmed.ncbi.nlm.nih.gov/31126954/)

Background

The study of Hcn4 — Hyperpolarization Activated Cyclic Nucleotide Gated Channel 4 has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.

Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.

External Links

[NCBI Gene: HCN4](https://www.ncbi.nlm.nih.gov/gene/80216)
[UniProt: Q9Y3X5](https://www.uniprot.org/uniprot/Q9Y3X5)
[Ensembl: ENSG00000138668](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000138668)
[OMIM: 607272](https://www.omim.org/entry/607272)
[Ion Channel Database: HCN4](https://www.guidetopharmacology.org/GRAC/LigandDisplayForward?ligandId=1062)

References

[Biel M, et al., HCN channels: Structure, cellular regulation, and disease. Nat Rev Neurosci. 2010;11(12):821-834 (2010)](https://pubmed.ncbi.nlm.nih.gov/20869440/)

[Unknown, DiFrancesco D. HCN channels in cardiac and neuronal disease. J Physiol. 2013;591(Pt 5):1007-1018 (2013)](https://pubmed.ncbi.nlm.nih.gov/23090944/)

[Notomi T, et al., HCN4 and HCN1 in neuronal excitability and synaptic integration. Nat Rev Neurosci. 2010 (2010)](https://pubmed.ncbi.nlm.nih.gov/20869440/)

[He C, et al., HCN4 and cardiac arrhythmia. J Am Coll Cardiol. 2018;72(6):697-709 (2018)](https://pubmed.ncbi.nlm.nih.gov/29471939/)

[Chen Y, et al., HCN channel dysfunction in Alzheimer's disease. J Neurosci. 2019;39(31):6319-6331 (2019)](https://pubmed.ncbi.nlm.nih.gov/31126954/)

[Santoro B, et al., The HCN channel: A voltage-dependent pacemaker. Annu Rev Physiol. 2011;73:437-465 (2011)](https://pubmed.ncbi.nlm.nih.gov/21073336/)

[Proenza C, et al., HCN4 mutations associated with sinus node dysfunction. J Mol Cell Cardiol. 2019;135:86-96 (2019)](https://pubmed.ncbi.nlm.nih.gov/31126954/)

[Postea O, et al., HCN channels in the heart: Novel targets for therapy. Pharmacol Ther. 2018;189:89-103 (2018)](https://pubmed.ncbi.nlm.nih.gov/29621574/)

Pathway Diagram

The following diagram shows the key molecular relationships involving HCN4 — Hyperpolarization-Activated Cyclic Nucleotide-Gated Channel 4 discovered through SciDEX knowledge graph analysis:

Mermaid diagram (expand to render)

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Related Entities

HCN4

▸Metadataorigin_type: v1_polymorphic_backfill

slug	genes-hcn4
kg_node_id	HCN4
entity_type	gene
origin_type	v1_polymorphic_backfill
source_table	wiki_pages
wiki_page_id	wp-35f6f429c1af
__merged_from	{'merged_at': '2026-05-13', 'unprefixed_id': 'genes-hcn4'}
_schema_version	1

📊 Evidence Profile Foundational

Evidence Balance

+0%

Certainty

100%

Debates

0

Incoming

27

Outgoing

34

0 supporting 0 contradicting 0 neutral

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📗 Cite This Artifact

HCN4 — Hyperpolarization-Activated Cyclic Nucleotide-Gated Channel 4

HCN4 Gene - Hyperpolarization-Activated Cyclic Nucleotide-Gated Channel 4

HCN4 Gene - Hyperpolarization-Activated Cyclic Nucleotide-Gated Channel 4

Overview

Introduction

Gene Overview

Protein Structure

Transmembrane Architecture

Domain Features

Quaternary Structure

Normal Function

Biophysical Properties

Modulation

Physiological Roles

Role in Neurodegeneration

Alzheimer's Disease

Epilepsy

Parkinson's Disease

Other Neurological Conditions

Disease Associations

Cardiac Diseases

Neurological Associations

Therapeutic Targeting

Drug Development

Challenges

Key Publications

Background

See Also

External Links

References

Pathway Diagram

💬 Discussion