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[@hall2022][@yoshida2022].
Gene Overview
Protein Structure and Function
Structure
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SLC22A4 — Solute Carrier Family 22 Member 4 (OCTN1)
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[@hall2022][@yoshida2022].
Gene Overview
Protein Structure and Function
Structure
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.
Function
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)[@hall2022]
Carnitine Transport: Transports L-carnitine, important for fatty acid metabolism
Drug Transport: Mediates uptake of various organic cations including certain medications
Role in Neurodegeneration
Neuroprotection via Ergothioneine Transport
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
Alzheimer's Disease
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](/proteins/amyloid-beta) to reduce its toxicity
Blood-Brain Barrier: OCTN1 expression at the BBB determines ergothioneine brain uptake
Parkinson's Disease
OCTN1 and ergothioneine show potential relevance in PD:
[Ishiwata K et al., Physiological Roles of Carnitine/Organic Cation Transporter OCTN1/SLC22A4 in Neural Cells (2017)](https://pubmed.ncbi.nlm.nih.gov/28768995/)
[Nakamichi N et al., Functional expression of carnitine/organic cation transporter OCTN1 in mouse brain neurons (2012)](https://pubmed.ncbi.nlm.nih.gov/22944603/)
[Bito T et al., Carnitine/Organic Cation Transporter OCTN1 Negatively Regulates Activation in Murine Cultured Microglial Cells (2018)](https://pubmed.ncbi.nlm.nih.gov/28688036/)
[Hall SC et al., Ergothioneine in the Brain (2022)](https://pubmed.ncbi.nlm.nih.gov/34978075/)
[Yoshida K et al., Ergothioneine and central nervous system diseases (2022)](https://pubmed.ncbi.nlm.nih.gov/35788879/)
[Yamaguchi S et al., Functional Expression of Carnitine/Organic Cation Transporter 1 in Murine Choroid Plexus (2024)](https://pubmed.ncbi.nlm.nih.gov/39231688/)
[Castellano P et al., Targeting ergothioneine in neurodegenerative diseases (2023)](https://pubmed.ncbi.nlm.nih.gov/37642612/)