Molecular basis of SLC19A1-mediated folate and cyclic dinucleotide transport
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Updated: May 17, 2025

Author Spotlight: Expression and Purification of Human Solute Carrier Transporters Using Codon-Optimized Genes
Published on: September 29, 2023
Qixiang Zhang1, Xuyuan Zhang2, Kexin Liu2,3
1Key Laboratory of Molecular Medicine and Biotherapy, Aerospace Center Hospital, School of Life Science, Beijing Institute of Technology, Beijing, China.
Abstract:
The solute carrier protein SLC19A1 is crucial for transporting folate nutrients, antifolate chemotherapeutics, and more recently cyclic dinucleotides (CDNs) immune transmitters, influencing various physiological and pathological processes. While the inward-open state of human SLC19A1 (hSLC19A1) has been previously described, key aspects regarding its conformational dynamics, substrate selectivity, and precise mechanisms underlying CDNs transport remain elusive. Using an antibody-facilitated conformation screening strategy, we present cryo-electron microscopy structures of hSLC19A1 in its outward-open state with and without bound substrates, revealing detailed mechanisms of substrate recognition and conformational changes during transport. We identify both general and specific features for folate/antifolate recognition, including an SLC19A1-specific pocket for accommodating γ-carboxylate-modified antifolates. Intriguingly, CDNs bind as monomers within the canonical pocket of outward-open hSLC19A1, contrasting with dimeric binding in inward-open structures. Together with functional assays, these findings provide a framework for developing antifolate drugs and CDN-targeted therapies, advancing our understanding of SLC19A1's physiological and therapeutic functions.
Insights
The solute carrier protein SLC19A1
Area of Science:
- Structural Biology
- Molecular Transport
- Drug Discovery
Background:
- Solute carrier protein SLC19A1 transports vital nutrients and drugs.
- Understanding SLC19A1's conformational dynamics and substrate transport is crucial.
- Previous studies focused on the inward-open state, leaving outward-open mechanisms unclear.
Purpose of the Study:
- To elucidate the outward-open state structures of human SLC19A1 (hSLC19A1).
- To reveal mechanisms of substrate recognition and conformational changes during transport.
- To understand the binding of cyclic dinucleotides (CDNs) and antifolates.
Main Methods:
- Antibody-facilitated conformation screening.
- Cryo-electron microscopy (cryo-EM) of hSLC19A1.
- Functional assays to validate structural findings.
Main Results:
- Determined cryo-EM structures of hSLC19A1 in the outward-open state.
- Identified specific binding pockets for folates, antifolates, and CDNs.
- Observed monomeric binding of CDNs in the outward-open state, differing from inward-open states.
Conclusions:
- Provided detailed insights into hSLC19A1 substrate recognition and transport mechanisms.
- Revealed distinct binding modes for CDNs in different conformational states.
- Established a framework for developing novel antifolate drugs and CDN-based therapies.
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