SLC22A4 (Solute Carrier Family 22 Member 4), also known as OCTN1 (Organic Cation Transporter Novel 1), is a membrane transport protein that plays critical roles in neuronal function. It is the primary transporter for ergothioneine—a unique sulfur-containing amino acid with potent antioxidant properties—across the blood-brain barrier and into neural cells.
| Attribute |
Value |
| Gene Symbol |
SLC22A4 |
| Full Name |
Solute Carrier Family 22 Member 4 (OCTN1) |
| Chromosomal Location |
5q31.1 |
| NCBI Gene ID |
6582 |
| Ensembl ID |
ENSG00000145040 |
| UniProt ID |
Q9H001 |
¶ Protein Structure and Function
OCTN1 is a 553 amino acid integral membrane protein belonging to the organic cation transporter family. It contains 12 transmembrane domains and functions as a sodium-dependent symporter.
- Ergothioneine Transport: OCTN1 is the primary high-affinity transporter for ergothioneine, a potent antioxidant that cannot be synthesized by humans and must be obtained from diet (mushrooms, certain foods)
- Carnitine Transport: Transports L-carnitine, important for fatty acid metabolism
- Drug Transport: Mediates uptake of various organic cations including certain medications
OCTN1-mediated ergothioneine transport is critical for neuronal health:
- Antioxidant Defense: Ergothioneine scavenges reactive oxygen species (ROS) and prevents oxidative damage
- Mitochondrial Protection: Preserves mitochondrial function under stress
- Neuroinflammation Modulation: Reduces microglial activation and inflammatory cytokine production
In Alzheimer's disease, OCTN1 dysfunction may contribute to pathogenesis:
- Oxidative Stress: Impaired ergothioneine transport reduces antioxidant capacity
- Amyloid Interactions: Ergothioneine may interact with amyloid-beta to reduce its toxicity
- Blood-Brain Barrier: OCTN1 expression at the BBB determines ergothioneine brain uptake
OCTN1 and ergothioneine show potential relevance in PD:
- Dopaminergic Neuron Protection: Ergothioneine protects substantia nigra neurons
- Mitochondrial Toxins: May modulate sensitivity to MPTP and other mitochondrial toxins
- Alpha-Synuclein: Ergothioneine may reduce alpha-synuclein aggregation
OCTN1 negatively regulates microglial activation:
flowchart TD
A["OCTN1 Expression<br/>in Microglia"] --> B["Ergothioneine<br/>Accumulation"]
B --> C["Reduced ROS<br/>Production"]
C --> D["Lower Pro-inflammatory<br/>Cytokines"]
D --> E["Neuroprotective<br/>Phenotype"]
F["OCTN1 Deficiency"] --> G["Ergothioneine<br/>Depletion"]
G --> H["Microglial<br/>Activation"]
H --> I["Chronic<br/>Neuroinflammation"]
style A fill:#c8e6c9
style E fill:#c8e6c9
style F fill:#ffcdd2
style I fill:#ffcdd2
- Alzheimer's Disease: Reduced OCTN1 expression may contribute to oxidative stress
- Parkinson's Disease: Ergothioneine deficiency may increase dopaminergic neuron vulnerability
- Multiple Sclerosis: OCTN1 may influence neuroinflammatory processes
- Inflammatory Disorders: OCTN1 modulates immune responses
- Aging: Age-related decline in OCTN1 function may increase neurodegeneration risk
OCTN1 is expressed in:
- Brain: Neurons (cortex, hippocampus), microglia, astrocytes
- Choroid Plexus: At the blood-cerebrospinal fluid barrier
- Peripheral Tissues: Kidney, intestine, liver
OCTN1 is a target for neuroprotective strategies:
- Ergothioneine Supplementation: Exogenous ergothioneine is being explored for AD/PD
- OCTN1 Agonists: Compounds that enhance OCTN1 expression and activity
- Blood-Brain Barrier Targeting: Enhancing ergothioneine transport into the brain
- Ergothioneine analogs with improved brain penetration
- Small molecules that upregulate OCTN1 expression
- Combination therapies targeting oxidative stress and neuroinflammation