CHCHD5 — Coiled-Coil-Helix-Coiled-Coil-Helix Domain Containing 5

CHCHD5 — Coiled-Coil-Helix-Coiled-Coil-Helix Domain Containing 5

Introduction

CHCHD5 (Coiled-Coil-Helix-Coiled-Coil-Helix Domain Containing 5) is a small mitochondrial protein that plays essential roles in oxidative phosphorylation, cellular respiration, and neuronal survival[^chchd2012]. As a member of the CHCHD family of proteins, CHCHD5 contains the distinctive CHCH domain characterized by pairs of cysteine residues that form intramolecular disulfide bonds, enabling proper protein folding and mitochondrial localization[@chchd2014][^chchd2014].

While initially characterized in non-neural tissues, emerging research has revealed important functions for CHCHD5 in neurons and has identified altered expression patterns in neurodegenerative disease models, particularly in [Parkinson's disease](/diseases/parkinsons-disease) and [amyotrophic lateral sclerosis](/diseases/amyotrophic-lateral-sclerosis)[@altered2018][^altered2018][^dysregulation2022]. The protein's location in the mitochondrial inner membrane and intermembrane space positions it ideally to influence electron transport chain function and cellular energy metabolism—processes that are fundamentally disrupted in most neurodegenerative conditions.

<div class="infobox infobox-gene">

CHCHD5 — Coiled-Coil-Helix-Coiled-Coil-Helix Domain Containing 5

Introduction

CHCHD5 (Coiled-Coil-Helix-Coiled-Coil-Helix Domain Containing 5) is a small mitochondrial protein that plays essential roles in oxidative phosphorylation, cellular respiration, and neuronal survival[^chchd2012]. As a member of the CHCHD family of proteins, CHCHD5 contains the distinctive CHCH domain characterized by pairs of cysteine residues that form intramolecular disulfide bonds, enabling proper protein folding and mitochondrial localization[@chchd2014][^chchd2014].

While initially characterized in non-neural tissues, emerging research has revealed important functions for CHCHD5 in neurons and has identified altered expression patterns in neurodegenerative disease models, particularly in [Parkinson's disease](/diseases/parkinsons-disease) and [amyotrophic lateral sclerosis](/diseases/amyotrophic-lateral-sclerosis)[@altered2018][^altered2018][^dysregulation2022]. The protein's location in the mitochondrial inner membrane and intermembrane space positions it ideally to influence electron transport chain function and cellular energy metabolism—processes that are fundamentally disrupted in most neurodegenerative conditions.

<div class="infobox infobox-gene">

| Property | Value |
|----------|-------|
| Gene Symbol | CHCHD5 |
| Full Name | Coiled-Coil-Helix-Coiled-Coil-Helix Domain Containing 5 |
| Chromosomal Location | 2q31.1 |
| NCBI Gene ID | 130560 |
| OMIM ID | — |
| Ensembl ID | ENSG00000182809 |
| UniProt ID | Q8N5Z0 |
| Encoded Protein | CHCHD5 |
| Protein Length | 112 amino acids |
| Molecular Weight | ~12 kDa |
| Expression | Mitochondrial (inner membrane/IMS) |

</div>

Gene Structure and Protein Architecture

Gene Organization

The CHCHD5 gene is located on chromosome 2q31.1 and encodes a relatively small protein of 112 amino acids. The gene structure is simple, reflecting the compact nature of the encoded protein. Unlike larger mitochondrial proteins that often contain multiple functional domains, CHCHD5's function is primarily mediated through its distinctive CHCH domain architecture.

CHCH Domain Architecture

The defining feature of CHCHD5 is its CHCH domain, which characterizes a family of mitochondrial proteins including [CHCHD10](/genes/chchd10), CHCHD2, CHCHD3, CHCHD4, and CHCHD6[^chchd2014]. This domain structure consists of:

The disulfide bond formation between cysteine residues is critical for protein stability in the oxidizing environment of the mitochondrial intermembrane space. This structural feature distinguishes CHCHD proteins from other mitochondrial proteins and suggests specialized functions in redox regulation and protein complex assembly.

Structural Features and Post-translational Modifications

CHCHD5 contains several structural elements important for its function:

• Twin cysteine motifs: Cysteine pairs at positions 38-41 and 67-70 form disulfide bonds
• Hydrophobic patches: Facilitate membrane association within mitochondria
• Potential phosphorylation sites: Serine/threonine residues for regulatory modifications
• Protein interaction motifs: Coiled-coil regions for dimerization

Function and Cellular Roles

Mitochondrial Respiration

CHCHD5 plays a direct role in regulating mitochondrial oxidative phosphorylation[^chchd2012]:

Complex I Regulation:

• CHCHD5 directly interacts with mitochondrial complex I (NADH:ubiquinone oxidoreductase)
• Influences assembly and stability of the complex I machinery
• Regulates NADH oxidation and electron flow through the respiratory chain
• Loss of CHCHD5 leads to reduced complex I activity and impaired respiration

• Impaired CHCHD5 function reduces cellular ATP production
• Affects both basal and maximal respiratory capacity
• Particularly impactful in high-energy-demand cells like neurons

Mitochondrial Dynamics

Beyond electron transport, CHCHD5 influences mitochondrial dynamics[^mitochondrial2021]:

Cristae Structure:

• CHCHD5 contributes to maintenance of mitochondrial cristae organization
• Proper cristae structure is essential for efficient ATP synthesis
• Altered CHCHD5 leads to disrupted cristae architecture

• Influences mitochondrial fission and fusion balance
• Affects mitochondrial motility and distribution in cells
• Important for neuronal processes where mitochondria must be positioned strategically

Oxidative Stress Response

CHCHD5 participates in cellular antioxidant defenses[^chchd2020]:

• Protects against reactive oxygen species (ROS) accumulation
• Maintains mitochondrial redox balance
• Prevents ROS-induced damage to proteins, lipids, and DNA
• Loss of CHCHD5 increases susceptibility to oxidative stress

Neuronal Survival

In neurons specifically, CHCHD5 supports survival through:

• Maintaining mitochondrial function in high-energy-demand cells
• Protecting against oxidative damage common in neurodegeneration
• Supporting synaptic function through proper mitochondrial positioning
• Enabling proper calcium handling and mitochondrial calcium buffering

Expression Patterns

Tissue Distribution

CHCHD5 shows broad but specific expression patterns:

| Tissue | Expression Level | Notes |
|--------|-----------------|-------|
| Brain | High | Highest in cortex, hippocampus, cerebellum |
| Heart | High | Cardiac muscle high energy demands |
| Skeletal muscle | High | Metabolic tissue |
| Kidney | Moderate | Basal expression |
| Liver | Low-Moderate | Moderate metabolic activity |
| Lung | Low | Lower energy requirements |

Brain Regional Expression

Within the brain[^bioenergetics_2021]:

• Cerebral cortex: High expression in pyramidal neurons
• Hippocampus: Prominent in CA1-CA3 neurons and dentate gyrus
• Cerebellum: Expressed in Purkinje cells and granule cells
• Brainstem: Moderate expression in motor and sensory nuclei
• Substantia nigra: Present in dopaminergic neurons

Cellular Localization

CHCHD5 is predominantly localized to:

Expression increases during periods of high metabolic demand, such as in actively firing neurons or during cellular stress responses.

Role in Neurodegenerative Diseases

Parkinson's Disease

CHCHD5 has emerged as relevant to Parkinson's disease pathogenesis[^altered2018][^mitochondrial2023]:

1. Mitochondrial Dysfunction in PD:

• PD is characterized by profound mitochondrial deficits
• Complex I deficiency is a hallmark of sporadic and familial PD
• CHCHD5's role in complex I regulation connects it to this core pathology

• CHCHD5 is expressed in dopaminergic neurons of the substantia nigra
• These neurons have particularly high energy requirements
• Altered CHCHD5 expression may contribute to their selective vulnerability

• CHCHD5 may interact with the PINK1/Parkin mitophagy pathway
• This pathway is critically implicated in familial PD
• Proper mitophagy is essential for removing dysfunctional mitochondria

• Mitochondrial dysfunction can influence alpha-synuclein aggregation
• CHCHD5 alterations may create environment conducive to pathological aggregation
• Potential bidirectional relationship between mitochondrial function and protein aggregation

• Loss of CHCHD5 function reduces complex I activity
• Contributes to energy failure in dopaminergic neurons
• Increases oxidative stress in the substantia nigra
• May accelerate dopaminergic neuron death

Amyotrophic Lateral Sclerosis

CHCHD5 dysregulation has been identified in ALS models[^dysregulation2022]:

1. Motor Neuron Vulnerability:

• Motor neurons are highly dependent on mitochondrial function
• CHCHD5 expression is altered in ALS models
• Contributes to the energy deficits seen in ALS pathogenesis

• ALS is characterized by protein inclusions (TDP-43, SOD1, FUS)
• Mitochondrial dysfunction may promote protein aggregation
• CHCHD5 alterations may contribute to this process

• Motor neurons experience high oxidative stress in ALS
• CHCHD5 loss exacerbates oxidative damage
• Creates feed-forward loop of neurodegeneration

Alzheimer's Disease

While less directly studied, CHCHD5 may be relevant to AD[^bioenergetics_2021]:

• Mitochondrial dysfunction is an early feature of AD
• Complex I deficits have been reported in AD brain
• CHCHD5 alterations could contribute to these deficits
• Neuronal energy failure is a core pathological feature

Common Mechanism: Mitochondrial Failure

Across neurodegenerative diseases, CHCHD5 contributes through:

Interaction Network

CHCHD5 interacts with multiple proteins and pathways:

| Partner | Interaction Type | Functional Effect |
|---------|-----------------|-------------------|
| Complex I | Direct component | Electron transport |
| CHCHD10 | Homologous protein | Dimerization, complex formation |
| CHCHD2 | Homologous protein | Mitochondrial function |
| PINK1 | Pathway interaction | Mitophagy regulation |
| Parkin | Pathway interaction | Mitophagy regulation |
| MFN2[^mfn2_2020] | Network regulation | Mitochondrial dynamics |
| OPA1 | Network regulation | Inner membrane fusion |

Therapeutic Implications

Therapeutic Target Rationale

CHCHD5 represents a potential therapeutic target for neurodegenerative diseases[^mitochondrial2023][^mitochondrial2024]:

1. Mitochondrial Protection:

• Enhancing CHCHD5 function could protect complex I
• Preserve mitochondrial respiration in vulnerable neurons
• Reduce energy failure in neurodegeneration

• Supporting CHCHD5 function may reduce oxidative stress
• Enhance cellular antioxidant capacity
• Protect against ROS-induced damage

• CHCHD5 interactions with PINK1/Parkin suggest therapeutic potential
• Enhancing mitophagy could clear dysfunctional mitochondria
• Reduce accumulation of damaged mitochondria

Challenges

• Delivering therapeutic agents to neurons in the brain
• Ensuring proper mitochondrial localization of interventions
• Understanding context-dependent effects
• Potential for compensation by related proteins

Animal Models and Research Tools

Genetic Models

• Knockout mice: Embryonic or perinatal lethal in some backgrounds
• Conditional knockouts: Tissue-specific deletion for adult studies
• Transgenic overexpression: Wild-type and mutant constructs
• Humanized models: Expressing human CHCHD5 variants

Experimental Systems

• Cell lines: HEK293, SH-SY5Y neuroblastoma cells
• Primary neurons: Mouse and human iPSC-derived neurons
• Brain slices: Organotypic cultures for physiological studies
• In vivo models: Transgenic and knockout mouse models

Research Directions

Key questions remain about CHCHD5:

See Also

• [Mitochondrial Dysfunction Pathway](/mechanisms/mitochondrial-dysfunction-neurodegeneration)
• [Oxidative Stress Pathway](/mechanisms/oxidative-stress-neurodegeneration)
• [Parkinson's Disease](/diseases/parkinsons-disease)
• [Amyotrophic Lateral Sclerosis](/diseases/amyotrophic-lateral-sclerosis)
• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [CHCHD10 Gene](/genes/chchd10)
• [PINK1 Gene](/genes/pink1)
• [PARKIN Gene](/genes/parkin)
• [Complex I Deficiency](/mechanisms/complex-i-deficiency)

External Links

• [NCBI Gene - CHCHD5](https://www.ncbi.nlm.nih.gov/gene/130560)
• [UniProt - CHCHD5](https://www.uniprot.org/uniprot/Q8N5Z0)
• [Ensembl - CHCHD5](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000182809)
• [GeneCards - CHCHD5](https://www.genecards.org/cgi-bin/carddisp.pl?gene=CHCHD5)

Brain Atlas Resources

• [Allen Human Brain Atlas*: [Gene expression search](https://human.brain-map.org/microarray/search/show?search_term=CHCHD5)](/datasets/allen-human-brain-atlas)
• Allen Mouse Brain Atlas: [Gene search](https://mouse.brain-map.org/search/index.html?query=CHCHD5)
• Allen Cell Type Atlas: [Transcriptomic cell type reference](https://portal.brain-map.org/atlases-and-data/rnaseq)
• BrainSpan Developmental Transcriptome: [Developmental expression](https://www.brainspan.org/rnaseq/search/index.html?search_term=CHCHD5)

References

Mechanistic Pathway: CHCHD5 in Mitochondrial Function

See Also

• [Mitochondrial Dysfunction Pathway](/mechanisms/mitochondrial-dysfunction-neurodegeneration)
• [Oxidative Stress Pathway](/mechanisms/oxidative-stress-neurodegeneration)
• [Parkinson's Disease](/diseases/parkinsons-disease)
• [Amyotrophic Lateral Sclerosis](/diseases/amyotrophic-lateral-sclerosis)
• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [CHCHD10 Gene](/genes/chchd10)
• [PINK1 Gene](/genes/pink1)
• [PARKIN Gene](/genes/parkin)
• [Complex I Deficiency](/mechanisms/complex-i-deficiency)

External Links

• [NCBI Gene - CHCHD5](https://www.ncbi.nlm.nih.gov/gene/130560)
• [UniProt - CHCHD5](https://www.uniprot.org/uniprot/Q8N5Z0)
• [Ensembl - CHCHD5](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000182809)
• [GeneCards - CHCHD5](https://www.genecards.org/cgi-bin/carddisp.pl?gene=CHCHD5)

Disease Associations

Source: Open Targets Platform (opentargets.org)

| Disease | Association Score | Disease ID |
|--------|-------------------|------------|
| Chronic Obstructive Asthma | 0.1689 | EFO_0009759 |
| lower respiratory tract disease | 0.1549 | EFO_0009433 |
| lung cancer | 0.0739 | MONDO_0008903 |
| prostate carcinoma | 0.0532 | EFO_0001663 |
| placental retention | 0.0346 | EFO_0009578 |