slc25a20

slc25a20

Overview

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">slc25a20</th>
</tr>
<tr>
<td class="label">Tissue</td>
<td>Expression Level</td>
</tr>
<tr>
<td class="label">Heart</td>
<td>Very High</td>
</tr>
<tr>
<td class="label">Skeletal Muscle</td>
<td>High</td>
</tr>
<tr>
<td class="label">Liver</td>
<td>High</td>
</tr>
<tr>
<td class="label">Kidney</td>
<td>Moderate</td>
</tr>
<tr>
<td class="label">Brain</td>
<td>Low</td>
</tr>
<tr>
<td class="label">Lung</td>
<td>Low</td>
</tr>
<tr>
<td class="label">Pathway</td>
<td>Connection</td>
</tr>
<tr>
<td class="label">Fatty Acid β-Oxidation</td>
<td>Substrate transport</td>
</tr>
<tr>
<td class="label">Ketogenesis</td>
<td>Acetyl-CoA supply</td>
</tr>
<tr>
<td class="label">TCA Cycle</td>
<td>Final oxidation</td>
</tr>
<tr>
<td class="label">Electron Transport Chain</td>
<td>NADH/FADH2 generation</td>
</tr>
<tr>
<td class="label">Carnitine Metabolism</td>
<td>Core component</td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>

slc25a20

Overview

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">slc25a20</th>
</tr>
<tr>
<td class="label">Tissue</td>
<td>Expression Level</td>
</tr>
<tr>
<td class="label">Heart</td>
<td>Very High</td>
</tr>
<tr>
<td class="label">Skeletal Muscle</td>
<td>High</td>
</tr>
<tr>
<td class="label">Liver</td>
<td>High</td>
</tr>
<tr>
<td class="label">Kidney</td>
<td>Moderate</td>
</tr>
<tr>
<td class="label">Brain</td>
<td>Low</td>
</tr>
<tr>
<td class="label">Lung</td>
<td>Low</td>
</tr>
<tr>
<td class="label">Pathway</td>
<td>Connection</td>
</tr>
<tr>
<td class="label">Fatty Acid β-Oxidation</td>
<td>Substrate transport</td>
</tr>
<tr>
<td class="label">Ketogenesis</td>
<td>Acetyl-CoA supply</td>
</tr>
<tr>
<td class="label">TCA Cycle</td>
<td>Final oxidation</td>
</tr>
<tr>
<td class="label">Electron Transport Chain</td>
<td>NADH/FADH2 generation</td>
</tr>
<tr>
<td class="label">Carnitine Metabolism</td>
<td>Core component</td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>

SLC25A20 (Carnitine-Acylcarnitine Translocase, also known as CACT) is a critical mitochondrial carrier protein that mediates the transport of acylcarnitine esters across the inner mitochondrial membrane in exchange for free carnitine. This transport system is essential for fatty acid oxidation (FAO), particularly in tissues with high metabolic demand such as the heart, skeletal muscle, and liver. The SLC25A20 gene (ENSG00000102737) is located on chromosome 3p21.31 and encodes a protein of 301 amino acids that belongs to the mitochondrial carrier family [1](https://pubmed.ncbi.nlm.nih.gov/18371060/).

The carnitine shuttle system is crucial for enabling fatty acids to enter the mitochondrial matrix for β-oxidation, as the inner mitochondrial membrane is impermeable to fatty acyl-CoA esters. By converting these esters to acylcarnitine derivatives that can be transported by SLC25A20, the cell enables efficient energy production from lipid substrates. This process is especially critical in heart and skeletal muscle, which rely heavily on fatty acid oxidation for ATP production during rest and exercise [2](https://pubmed.ncbi.nlm.nih.gov/21807060/).

Molecular Biology and Structure

Gene Organization

The SLC25A20 gene spans approximately 8 kb of genomic DNA and comprises 9 exons. It encodes a protein of 301 amino acids with a molecular weight of approximately 33 kDa. The protein is expressed in all tissues requiring fatty acid oxidation, with highest levels in heart, skeletal muscle, and liver.

Protein Structure

SLC25A20 belongs to the mitochondrial carrier (SLC25) family, characterized by:

• Six transmembrane α-helices forming a barrel-like structure
• Three signature motifs: P-X-D-E-X-X-A-K/R (or variations)
• Carrier-specific substrate-binding pocket
• Dimerization capability for functional transport

Transport Mechanism

SLC25A20 operates as a strict antiporter:

This exchange is essential for the carnitine shuttle system, which involves multiple enzymes:

• CPT1 (Carnitine Palmitoyltransferase 1): Outer membrane, converts acyl-CoA to acylcarnitine
• SLC25A20 (CACT): Inner membrane, exchanges acylcarnitine and carnitine
• CPT2 (Carnitine Palmitoyltransferase 2): Inner membrane, converts acylcarnitine back to acyl-CoA

Function in Cellular Physiology

Fatty Acid Oxidation

The primary function of SLC25A20 is to enable fatty acid β-oxidation in the mitochondrial matrix. This process provides ATP through:

• Acetyl-CoA production for the Krebs cycle
• NADH and FADH2 for the electron transport chain
• Direct ATP generation via substrate-level phosphorylation

Carnitine Homeostasis

SLC25A20 is essential for maintaining cellular carnitine homeostasis:

• Recycling of free carnitine from acylcarnitine exports
• Prevention of acylcarnitine accumulation (toxic)
• Buffering of mitochondrial acyl-CoA/CoA ratio

• Removal of excess acyl groups
• Stabilization of the mitochondrial membrane potential
• Protection against acyl-CoA accumulation

Neuronal Energy Metabolism

While the brain primarily uses glucose, fatty acid oxidation becomes important in:

• Astrocytes: Supporting neuronal metabolism
• Myelin maintenance: Lipid synthesis requires fatty acids
• Stress conditions: Alternative energy during hypoglycemia
• Developmental stages: Higher reliance on fatty acids

• Myelin lipid synthesis and turnover
• Mitochondrial function in high-energy-demand states
• Protection against metabolic stress

Disease Associations

Carnitine-Acylcarnitine Translocase Deficiency (CACT Deficiency)

SLC25A20 mutations cause autosomal recessive CACT deficiency, a life-threatening metabolic disorder characterized by:

Clinical presentation:

• Severe neonatal onset (typically within first 48 hours)
• Hypoglycemia with elevated acylcarnitines
• Cardiomyopathy (often hypertrophic)
• Liver dysfunction
• Seizures
• Developmental delay
• Sudden infant death (in severe cases)

• Elevated plasma C14-C18 acylcarnitines
• Low free carnitine
• Metabolic acidosis
• Hyperammonemia

• Low-fat diet with medium-chain triglycerides (MCT)
• Carnitine supplementation
• Avoidance of fasting
• Emergency protocol for metabolic crises

Cardiomyopathy

SLC25A20 dysfunction causes dilated and hypertrophic cardiomyopathy:

• Fatty acid oxidation cannot meet cardiac energy demands
• Lipid accumulation in cardiomyocytes
• Progressive heart failure

Neurodegeneration

While primary CACT deficiency presents in infancy, mitochondrial fatty acid oxidation defects contribute to neurodegeneration through:

Mechanisms:

• Impaired ATP production in high-energy neurons
• Increased oxidative stress
• Disrupted lipid metabolism in myelin
• Altered calcium homeostasis
• Apoptotic pathway activation

• Altered fatty acid metabolism in AD brains
• Reduced carnitine levels in AD patients
• Possible contribution to amyloid pathology

• Mitochondrial dysfunction is central to PD pathogenesis
• Fatty acid oxidation defects may contribute to dopaminergic neuron loss
• Carnitine supplementation shows neuroprotective potential [5](https://pubmed.ncbi.nlm.nih.gov/24713240/)

Metabolic Syndrome

SLC25A20 variants may contribute to:

• Insulin resistance
• Type 2 diabetes
• Obesity
• Dyslipidemia

Expression Pattern

Tissue Distribution

Brain Expression

In the brain, SLC25A20 is expressed in:

• Astrocytes: Primary site of fatty acid metabolism
• Oligodendrocytes: Myelin production
• Neurons: Lower, stress-responsive expression
• Choroid plexus: Carnitine transport

• Cerebral cortex
• White matter tracts
• [Cerebellum](/brain-regions/cerebellum)
• Brainstem

Therapeutic Implications

Current Treatments

• Carnitine supplementation: 50-100 mg/kg/day
• MCT oil: Bypasses CPT1 requirement
• Low-fat diet: Reduces substrate load
• Emergency protocols: IV glucose for crises

Emerging Therapies

Neurodegeneration Research

Carnitine and fatty acid metabolism modulators are being investigated for:

• Alzheimer's disease: L-carnitine, acetyl-L-carnitine
• Parkinson's disease: Carnitine shuttle enhancers
• Amyotrophic lateral sclerosis: Metabolic support
• Multiple sclerosis: Myelin repair support

Interactions and Pathways

Metabolic Pathways

SLC25A20 connects to several critical metabolic pathways:

Protein Interactions

• CPT1A/B: Upstream acylcarnitine synthesis
• CPT2: Downstream acyl-CoA regeneration
• SLC22A5 (OCTN2): Plasma membrane carnitine transporter
• CRAT: Carnitine acetyltransferase
• SLC25A family: Other mitochondrial carriers

Regulatory Mechanisms

SLC25A20 is regulated by:

• PPARα: Transcriptional activation during fasting
• PGC-1α: Mitochondrial biogenesis coactivator
• AMPK: Energy stress response
• SIRT1: Metabolic regulation via deacetylation

Cross-Links

• [Mitochondrial Fatty Acid Oxidation](/mechanisms/mitochondrial-fatty-acid-oxidation)
• [Oxidative Phosphorylation](/mechanisms/oxidative-stress-neurodegeneration)
• [Mitochondrial Carriers](/mechanisms/mitochondrial-carrier-family)
• [Carnitine Metabolism](/mechanisms/carnitine-metabolism)
• [Cardiomyopathy](/diseases/cardiomyopathy)
• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Parkinson's Disease](/diseases/parkinsons-disease)
• [Metabolic Syndrome](/mechanisms/metabolic-syndrome-neurodegeneration)

See Also

• [Mitochondrial Fatty Acid Oxidation](/mechanisms/mitochondrial-fatty-acid-oxidation)
• [Oxidative Phosphorylation](/mechanisms/oxidative-stress-neurodegeneration)
• [Cardiomyopathy](/diseases/cardiomyopathy)
• [Metabolic Disease](/diseases/mitochondrial-metabolic-disorders)

External Links

• [NCBI Gene: SLC25A20](https://www.ncbi.nlm.nih.gov/gene/788)
• [UniProt: Q9H0U4](https://www.uniprot.org/uniprot/Q9H0U4)
• [Ensembl: ENSG00000102737](https://ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000102737)
• [OMIM: 613344](https://www.omim.org/entry/613344)
• [GeneCards: SLC25A20](https://www.genecards.org/cgi-bin/carddisp.pl?gene=SLC25A20)

References