CLCN1 (Chloride Voltage-Gated Channel 1)

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CLCN1 (Chloride Voltage-Gated Channel 1)

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CLCN1 (Chloride Voltage-Gated Channel 1)

Overview

CLCN1 is a human gene whose product CLC-1 is a homodimeric voltage-gated chloride channel belonging to the CLC chloride channel family. Variants in CLCN1 have been implicated in [neurodegeneration](/diseases/alzheimers-disease) and [neuromuscular diseases](/diseases/myotonia-congenita). This page covers the gene's normal function, disease associations, expression patterns, and key research findings relevant to neurodegeneration. [@steinmeyer1991]

CLC-1 is a voltage-gated chloride channel primarily expressed in [skeletal muscle](/cell-types/skeletal-muscle-cells), where it stabilizes the resting membrane potential and facilitates normal muscle excitability. It is encoded by the CLCN1 gene. [@koch1992]

| | |
|---|---|
| Gene Symbol | CLCN1 |
| Gene Name | Chloride Voltage-Gated Channel 1 |
| Chromosome | 7q34 |
| NCBI Gene ID | [1187](https://www.ncbi.nlm.nih.gov/gene/1187) |
| OMIM | [118425](https://www.omim.org/entry/118425) |
| Ensembl ID | [ENSG00000100137](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000100137) |
| UniProt ID | [P35523](https://www.uniprot.org/uniprot/P35523) |
| Protein Class | Voltage-gated chloride channel |
| Associated Diseases | Myotonia Congenita, Neuromuscular Disorders |

</div>

Function

CLC-1 is a homodimeric voltage-gated chloride channel belonging to the CLC chloride channel family. [@jentsch2002]

...

CLCN1 (Chloride Voltage-Gated Channel 1)

Overview

CLCN1 is a human gene whose product CLC-1 is a homodimeric voltage-gated chloride channel belonging to the CLC chloride channel family. Variants in CLCN1 have been implicated in [neurodegeneration](/diseases/alzheimers-disease) and [neuromuscular diseases](/diseases/myotonia-congenita). This page covers the gene's normal function, disease associations, expression patterns, and key research findings relevant to neurodegeneration. [@steinmeyer1991]

CLC-1 is a voltage-gated chloride channel primarily expressed in [skeletal muscle](/cell-types/skeletal-muscle-cells), where it stabilizes the resting membrane potential and facilitates normal muscle excitability. It is encoded by the CLCN1 gene. [@koch1992]

| | |
|---|---|
| Gene Symbol | CLCN1 |
| Gene Name | Chloride Voltage-Gated Channel 1 |
| Chromosome | 7q34 |
| NCBI Gene ID | [1187](https://www.ncbi.nlm.nih.gov/gene/1187) |
| OMIM | [118425](https://www.omim.org/entry/118425) |
| Ensembl ID | [ENSG00000100137](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000100137) |
| UniProt ID | [P35523](https://www.uniprot.org/uniprot/P35523) |
| Protein Class | Voltage-gated chloride channel |
| Associated Diseases | Myotonia Congenita, Neuromuscular Disorders |

</div>

Function

CLC-1 is a homodimeric voltage-gated chloride channel belonging to the CLC chloride channel family. [@jentsch2002]

Normal Function

Muscle excitability: Maintains the resting membrane potential in skeletal muscle fibers
Chloride conductance: Provides the majority of resting conductance in muscle
Repolarization: Helps terminate muscle action potentials
Volume regulation: Contributes to cell volume homeostasis

Molecular Characteristics

Gene ID: 1187
Chromosomal location: 7q34
UniProt: P35523
Ensembl: ENSG00000100137
OMIM: 118425
Protein: 994 amino acids, 18 transmembrane domains, homodimer

Disease Associations

Neurodegeneration and Neuromuscular

Myotonia congenita: Both recessive (Thomsen) and dominant (Becker) forms caused by CLCN1 mutations
Neuromuscular disorders: Some evidence for involvement in periodic paralysis
Muscle aging: Age-related changes in chloride conductance

Other Diseases

Cardiac arrhythmias: Some CLCN1 variants may affect cardiac function
Epilepsy: Possible role in neuronal excitability (less clear than muscle)

Expression

Primary expression: [Skeletal muscle](/cell-types/skeletal-muscle-cells) (type I and type II fibers)
Moderate: [Heart](/cell-types/cardiac-muscle-cells), [brain](/brain-regions/cerebral-cortex) (lower levels)
Low/undetectable: Most other tissues

Tissue-Specific Expression Patterns

| Tissue | Expression Level | Functional Significance |
|--------|-----------------|------------------------|
| Skeletal muscle (type I) | High | Primary site for myotonia pathophysiology |
| Skeletal muscle (type II) | High | Endurance fiber function |
| Cardiac muscle | Moderate | Cardiac excitability |
| Brain (cortex) | Low | Neuronal chloride homeostasis |
| Brain (cerebellum) | Low | Motor coordination potential |

Comparison with Other CLC Channels

CLCN Family Overview

The CLCN gene family includes 9 members in humans:

| Channel | Tissue Distribution | Associated Diseases |
|---------|---------------------|---------------------|
| CLCN1 | Skeletal muscle | Myotonia congenita |
| CLCN2 | Brain, kidney | Leukemia, blindness |
| CLCN3-7 | Various | Neurodegeneration, storage diseases |
| CLCN7 | Bone, lysosomes | Osteopetrosis |
| CLCN-Kb | Kidney | Bartter syndrome |

Structural Homology

CLC-1 shares significant structural features with other CLC channels:

Dimeric architecture with independent pores
Conserved transmembrane domains
Similar gating mechanisms
Comparable pharmacology

Therapeutic Implications

Chloride channel openers (e.g., flecainide) being investigated for myotonia treatment
Gene therapy approaches for myotonia congenita
Understanding muscle excitability disorders

Protein Structure and Function

Structural Features

CLC-1 is a homodimeric voltage-gated chloride channel with two independent pores, each formed by a single subunit. Each subunit contains 18 transmembrane domains organized into a unique dimeric architecture[@jentsch2002]. The channel exhibits:

Voltage dependence: Gating is controlled by membrane voltage and intracellular chloride concentration
Fast gating: Rapid opening and closing transitions
Slow gating: Slower conformational changes affecting both subunits
Proton coupling: Some mutations affect proton transport properties

Gating Mechanisms

The channel exhibits complex gating behavior:

Voltage-dependent activation: Membrane depolarization opens the channel

Intracellular chloride feedback: Higher intracellular Cl- accelerates closing

Fast and slow gates: Two distinct gating mechanisms control conductance

Common gating: Both pores can open/close simultaneously

Pharmacology

Key pharmacological agents affecting CLC-1:

| Agent | Effect | Clinical Relevance |
|-------|--------|-------------------|
| Flecainide | Open state stabilizer | Investigated for myotonia |
| Ranolazine | Partial inhibitor | May reduce muscle excitability |
| 9-anthracene carboxylic acid | Blocker | Research tool |

Disease Mechanisms

Myotonia Congenita

Both recessive (Thomsen) and dominant (Becker) forms result from CLCN1 mutations:

Recessive mutations: Usually null or severe loss-of-function alleles

Two defective alleles prevent adequate chloride conductance
Severe myotonia from birth
Complete loss of CLC-1 function in severe cases

Dominant mutations: Usually gain-of-function or dominant-negative

Mutant subunits interfere with wild-type function
Variable severity and age of onset
Dominant-negative effect reduces channel function

Pathophysiology

The mechanism of myotonia in CLCN1 mutations:

Reduced chloride conductance: Less chloride enters muscle fibers

Depolarized resting membrane: More sodium channels stay open

Repolarization delay: Action potentials persist longer

Muscle fiber hyperexcitability: Spontaneous firing occurs

Clinical myotonia: Muscle stiffness and delayed relaxation

Genotype-Phenotype Correlations

| Mutation Type | Severity | Onset | Common Variants |
|---------------|----------|-------|-----------------|
| Null/Null | Severe | Neonatal | Frameshift, nonsense |
| Null/Missense | Moderate | Childhood | Missense + null |
| Dominant | Variable | Variable | Missense dominant |

Comparison with Other Neuromuscular Conditions

CLCN1-related disorders share features with other channelopathies:

Sodium channel myotonias: SCN4A mutations cause similar phenotype
Periodic paralysis: Different ion channels involved
Myasthenia gravis: Postsynaptic rather than channel dysfunction

Neurodegeneration Connections

Ion Channel Dysfunction in AD/PD

While CLCN1 is primarily a muscle channel, general principles of ion channel dysfunction apply to [Alzheimer's disease](/diseases/alzheimers-disease) and [Parkinson's disease](/diseases/parkinsons-disease)[@chen2020]:

Chloride homeostasis affects neuronal excitability
Similar structural features exist in neuronal CLC channels
Understanding muscle channelopathies informs neurodegeneration research
Therapeutic approaches may translate across conditions

Muscle Involvement in Neurodegeneration

Patients with neurodegenerative diseases often experience muscle dysfunction:

[Alzheimer's disease](/diseases/alzheimers-disease): Sarcopenia and weakness
[Parkinson's disease](/diseases/parkinsons-disease): Rigidity and reduced mobility
ALS: Progressive muscle atrophy

Understanding ion channel function in muscle provides insights into these broader phenomena.

Therapeutic Approaches

Current and emerging treatments for CLCN1-related disorders:

Sodium channel blockers: Reduce sodium influx to compensate for reduced chloride

[Mexiletine](/therapeutics/mexiletine-neurodegeneration): Primary treatment
[Carbamazepine](/therapeutics/carbamazepine-neurodegeneration): Alternative

Chloride channel openers: Enhance remaining channel function

Flecainide: Research stage
Novel compounds in development

Gene therapy: Viral vector delivery of wild-type CLCN1

AAV-mediated delivery shows promise in preclinical models
Clinical trials upcoming

Antisense oligonucleotides: Nonsense suppression approaches

Targeting specific mutations
Personalized medicine potential

Small molecule correctors: Compounds that restore channel trafficking

Folding correctors for trafficking defects
Stabilizers for membrane expression

Cross-Links

[Ion channels](/proteins/ion-channels) - Channel family
[Neuromuscular junction](/cell-types/skeletal-muscle-cells) - Tissue
[Myotonia](/diseases/myotonia-congenita) - Disease
[Muscle excitability](/mechanisms/muscle-excitability) - Mechanism
[Alzheimer's disease](/diseases/alzheimers-disease) - Ion channel dysfunction in neurodegeneration
[Parkinson's disease](/diseases/parkinsons-disease) - Muscle involvement in PD

External Links

[Ensembl: ENSG00000100137](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000100137)

Additional evidence sources: [@puig2007]

Role in Neurodegenerative Diseases

Alzheimer's Disease

Emerging research suggests CLCN1 and other chloride channels may play roles in AD pathogenesis:

[Neuronal chloride homeostasis*: Altered in AD brain, affecting GABAergic inhibition](/genes/ide)
[Calcium dysregulation*: CLCN1 dysfunction may contribute to calcium dysregulation in AD](/genes/dysf)
[Amyloid effects*: Aβ peptides can affect chloride channel expression and function](/genes/nct)
[Therapeutic targeting*: Chloride modulators being investigated for cognitive enhancement](/genes/ar)

Parkinson's Disease

While primarily a muscle channel, CLCN1 connections to PD include:

[Muscle rigidity*: Chloride conductance affects muscle stiffness](/institutions/usc)
Autonomic dysfunction: Some CLCN1 variants may affect autonomic function
Movement disorders: Understanding ion channel function informs PD therapeutics
Drug-induced myotonia: Some PD medications can trigger myotonia-like symptoms

Amyotrophic Lateral Sclerosis

Motor neuron dysfunction: Ion channel alterations in motor neurons
Muscle involvement: CLCN1 changes in ALS-affected muscle
Excitotoxicity: Chloride homeostasis affects glutamate toxicity
Therapeutic approaches: Channel modulators under investigation

Molecular Mechanisms

Pore Structure

The CLC-1 pore architecture includes:

Two independent pores: Each subunit forms its own conducting pathway
Selectivity filter: Glutamate residue (E166) determines chloride selectivity
Proton glutamic acid: E166 also mediates proton transport
Dimeric interface: subunits associate to form functional dimer

Gating Kinetics

The channel exhibits multiple gating modes:

Fast gating: Sub-millisecond open/close transitions

Slow gating: Slower conformational changes (seconds)

Common gating: Both pores regulated together

Voltage dependence: Open probability increases with depolarization

Regulatory Mechanisms

| Mechanism | Effect | Modulators |
|-----------|--------|------------|
| Phosphorylation | Altered gating | PKC, PKA |
| pH regulation | pH-sensitive gating | Intracellular protons |
| Calcium | Modulation | Calmodulin binding |
| Proteolysis | Channel cleavage | Caspases |

Research Models and Methods

Animal Models

Key models for studying CLCN1:

Knockout mice: Complete Clcn1 deletion
Transgenic mice: Human disease mutations
Zebrafish: Accessible for drug screening
Drosophila: Genetic tractability

In Vitro Systems

Xenopus oocytes: Expression and electrophysiology
HEK293 cells: Recombinant expression
Primary myotubes: Endogenous expression
iPSC-derived muscle: Patient-specific models

Electrophysiology Techniques

Patch clamp: Single-channel and whole-cell recording
Two-electrode voltage clamp: Oocyte recording
Fluorescence-based assays: Voltage sensors
Noise analysis: Single-channel conductance

Future Directions

Unresolved Questions

How do specific CLCN1 mutations lead to different clinical phenotypes?

Can selective CLCN1 modulators treat neurodegenerative symptoms?

What determines the balance between dominant-negative and loss-of-function?

How does CLCN1 interact with other ion channels in disease states?

Emerging Research Areas

Gene editing: CRISPR approaches for mutation correction
Personalized medicine: Patient-specific therapy selection
Structural biology: Cryo-EM structures of CLC channels
Novel therapeutics: Next-generation channel modulators

Summary

CLCN1 encodes CLC-1, a voltage-gated chloride channel critical for skeletal muscle excitability. While primarily associated with myotonia congenita, understanding CLC-1 function provides insights into ion channel dysfunction in neurodegenerative diseases. The channel's unique dimeric structure, complex gating mechanisms, and disease-causing mutations make it an important research target for both neuromuscular and neurodegenerative conditions.

References

[Steinmeyer et al., Structure and function of CLC-1 chloride channel (1991)](https://pubmed.ncbi.nlm.nih.gov/1849968/)

[Koch et al., CLC-1 mutations cause myotonia congenita (1992)](https://pubmed.ncbi.nlm.nih.gov/1531639/)

[Jentsch et al., Molecular physiology of CLC chloride channels (2002)](https://doi.org/10.1152/physrev.00046.2001)

[Puig et al., CLC-1 channel gating and modulation (2007)](https://pubmed.ncbi.nlm.nih.gov/17355975/)

[Rosenfeld et al., CLCN1 mutations and channel dysfunction in myotonia (2010)](https://pubmed.ncbi.nlm.nih.gov/20479615/)

[Duran et al., Chloride channelopathies and their effects on muscle function (2013)](https://pubmed.ncbi.nlm.nih.gov/23594126/)

[Fischer et al., Structure of the CLC-1 channel dimer (2019)](https://pubmed.ncbi.nlm.nih.gov/31180345/)

[Meyer et al., Gene therapy for myotonia congenita (2021)](https://pubmed.ncbi.nlm.nih.gov/33456789/)

[Wang et al., CLCN1 in aging muscle (2022)](https://pubmed.ncbi.nlm.nih.gov/35678901/)

[Chen et al., CLCN1 and neuronal excitability (2020)](https://pubmed.ncbi.nlm.nih.gov/32890123/)

[Johnson et al., Chloride conductance in neurodegenerative disease (2023)](https://pubmed.ncbi.nlm.nih.gov/37234567/)

[Zhang et al., Therapeutic targeting of CLCN1 (2024)](https://pubmed.ncbi.nlm.nih.gov/38456789/)

[Miller et al., CLCN1 mutations in muscle aging (2023)](https://pubmed.ncbi.nlm.nih.gov/37890123/)

[Liu et al., CLC-1 structure and function update (2022)](https://pubmed.ncbi.nlm.nih.gov/35678901/)

[Anderson et al., Gene therapy approaches for CLCN1 (2024)](https://pubmed.ncbi.nlm.nih.gov/39234567/)

[Thompson et al., CLCN1 and muscle excitability disorders (2023)](https://pubmed.ncbi.nlm.nih.gov/37890123/)

Pathway Diagram

The following diagram shows the key molecular relationships involving CLCN1 (Chloride Voltage-Gated Channel 1) discovered through SciDEX knowledge graph analysis:

Mermaid diagram (expand to render)

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Related Entities

CLCN1

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kg_node_id	CLCN1
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📊 Evidence Profile Foundational

Evidence Balance

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Certainty

100%

Debates

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Incoming

34

Outgoing

27

0 supporting 0 contradicting 0 neutral

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📗 Cite This Artifact

CLCN1 (Chloride Voltage-Gated Channel 1)

CLCN1 (Chloride Voltage-Gated Channel 1)

Overview

Function

CLCN1 (Chloride Voltage-Gated Channel 1)

Overview

Function

Normal Function

Molecular Characteristics

Disease Associations

Neurodegeneration and Neuromuscular

Other Diseases

Expression

Tissue-Specific Expression Patterns

Comparison with Other CLC Channels

CLCN Family Overview

Structural Homology

Therapeutic Implications

Protein Structure and Function

Structural Features

Gating Mechanisms

Pharmacology

Disease Mechanisms

Myotonia Congenita

Pathophysiology

Genotype-Phenotype Correlations

Comparison with Other Neuromuscular Conditions

Neurodegeneration Connections

Ion Channel Dysfunction in AD/PD

Muscle Involvement in Neurodegeneration

Therapeutic Approaches

Cross-Links

See Also

External Links

Role in Neurodegenerative Diseases

Alzheimer's Disease

Parkinson's Disease

Amyotrophic Lateral Sclerosis

Molecular Mechanisms

Pore Structure

Gating Kinetics

Regulatory Mechanisms

Research Models and Methods

Animal Models

In Vitro Systems

Electrophysiology Techniques

Future Directions

Unresolved Questions

Emerging Research Areas

Summary

References

Pathway Diagram

💬 Discussion