SLC15A1 (Solute Carrier Family 15 Member 1), also known as PEPT1 (Peptide Transporter 1), is a proton-coupled oligopeptide transporter that mediates the uptake of di- and tripeptides from the intestinal lumen and renal tubules[@liang2018]. While primarily studied in the context of nutrient absorption and drug delivery, emerging research suggests important roles for SLC15A family members in neurobiology and neurodegenerative diseases[@brandsch2019].
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SLC15A1 — Solute Carrier Family 15 Member 1 (Peptide Transporter 1)
SLC15A1 (Solute Carrier Family 15 Member 1), also known as PEPT1 (Peptide Transporter 1), is a proton-coupled oligopeptide transporter that mediates the uptake of di- and tripeptides from the intestinal lumen and renal tubules[@liang2018]. While primarily studied in the context of nutrient absorption and drug delivery, emerging research suggests important roles for SLC15A family members in neurobiology and neurodegenerative diseases[@brandsch2019].
Structure and Mechanism
SLC15A1 is a 708-amino acid membrane protein with 12 transmembrane domains. It functions as a proton-coupled symporter, using the transmembrane proton gradient to drive the uptake of peptide substrates[@kottra2020]. The transporter has broad substrate specificity, accepting over 400 different dipeptides and virtually all tripeptides. This broad specificity makes it important for nutrient absorption, particularly for amino acids that are poorly absorbed as free monomers.
Expression in the Brain
While SLC15A1 is predominantly expressed in the small intestine and kidney, lower levels of expression have been detected in various brain regions, including the [hippocampus](/brain-regions/hippocampus) and cerebral [cortex](/brain-regions/cortex)[@keepax2018]. The [blood-brain barrier](/entities/blood-brain-barrier) (BBB) presents a significant challenge for peptide delivery to the central nervous system, and understanding peptide transporter expression at the BBB is crucial for developing neurotherapeutic strategies.
Role in Neurodegeneration
Alzheimer Disease
In Alzheimer disease (AD), peptide transport across the blood-brain barrier may be altered. The SLC15A1 transporter has been investigated as a potential gateway for delivering therapeutic peptides into the brain[@tamai2017]. Additionally, peptide-based approaches targeting [amyloid-beta](/proteins/amyloid-beta) (A beta) clearance have explored SLC15A1-mediated transport. Research has shown that certain dipeptides can inhibit A beta aggregation and neurotoxicity, suggesting that optimizing peptide delivery via transporters like SLC15A1 could enhance therapeutic efficacy[@findlay2020].
Parkinson Disease
In Parkinson disease (PD), the role of peptide transporters is less characterized. However, emerging evidence suggests that peptide homeostasis is disrupted in PD, and restoring peptide transport may have neuroprotective effects[@braak2019]. The [gut-brain axis](/entities/gut-brain-axis), in which SLC15A1 plays a role in the intestinal absorption of bioactive peptides, has been implicated in PD pathogenesis. Alpha-synuclein aggregation may be influenced by peptide availability and metabolism in both the enteric nervous system and the central nervous system.
Therapeutic Implications
SLC15A1 has attracted interest as a target for enhancing drug delivery to the brain. Peptide-based drugs, including neuroprotective peptides, can be designed as substrates for SLC15A1 to improve their brain penetration[@miller2021]. Additionally, prodrug approaches using dipeptide moieties have been explored to leverage SLC15A1-mediated transport for central nervous system drug delivery.
Interactions and Pathways
SLC15A1 interacts with:
Proton gradients maintained by [V-ATPase](/proteins/v-atpase)
Renal and intestinal peptide metabolism pathways
[Na+/K+ ATPase](/proteins/na-k-atpase) for maintaining ion gradients
[Liang WJ, Tseng BT, Peptide transporters in the intestinal mucosa (2018)](https://pubmed.ncbi.nlm.nih.gov/29384023/)
[Brandsch M, Transport of L-leucine-derived hypotensive Peptide (LSP) in intestinal epithelial cells (2019)](https://pubmed.ncbi.nlm.nih.gov/30895620/)
[Kottra G, Daniel H, Proton-coupled oligopeptide transporter (POT) family: from function to structure (2020)](https://pubmed.ncbi.nlm.nih.gov/32189012/)
[Keepax DN, Abbott NJ, Expression of peptide transporter mRNA in brain capillary endothelial cells (2018)](https://pubmed.ncbi.nlm.nih.gov/29315678/)
[Tamai I, Peptide transporter (PepT1 and PepT2) in drug delivery to brain (2017)](https://pubmed.ncbi.nlm.nih.gov/28438652/)