GO:0140924 L-kynurenine transmembrane transport: Transport Pathway, Genes, Functions and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0140924 (L-kynurenine transmembrane transport) is a biological_process defined as the directed movement of L-kynurenine across a membrane.
• L-kynurenine is a central intermediate of tryptophan catabolism, and its transport determines whether it is converted to neuroactive kynurenic acid, quinolinic acid, or acts as an AhR ligand.
• SLC7A5 (LAT1) is a major transporter that carries L-kynurenine and links tryptophan metabolism to the Kyn/XANA-AhR axis in cancer.
• In polarized epithelia, L-kynurenine transport is coupled to apical tryptophan depletion and local immune regulation.
• Dysregulated L-kynurenine transport is associated with colorectal cancer liver metastasis, chronic kidney disease, cystic fibrosis lung biology, and systemic lupus erythematosus.
• CRISPR knockout, knock-in, overexpression, and library screening in EDITGENE cell models enable causal testing of transporter genes in L-kynurenine transmembrane transport.
Description
GO:0140924, L-kynurenine transmembrane transport, is a Gene Ontology biological_process term that describes the directed movement of L-kynurenine across a membrane. L-kynurenine is the first stable metabolite of the kynurenine pathway of tryptophan degradation, and its distribution between tissues and cellular compartments determines whether it is further metabolized into neuroactive or immunomodulatory products. Because L-kynurenine is charged and polar at physiological pH, it requires dedicated membrane transporters rather than simple diffusion, making this GO term a focal point for understanding how tryptophan catabolism is spatially organized. Mechanistically, L-kynurenine transport is best understood as a facilitated process mediated by amino acid transporters such as SLC7A5, which can carry large neutral amino acids and kynurenine across the plasma membrane. In polarized human bronchial epithelium, apical tryptophan depletion involves coordinated transport activities that influence local kynurenine availability and downstream immune signaling. This transport step is therefore not a passive bystander but a regulated checkpoint that shapes kynurenine concentrations in the cytoplasm, extracellular space, and immune microenvironment. For researchers, GO:0140924 matters because it connects transporter biochemistry to disease-relevant phenotypes. SLC7A5-dependent kynurenine transport has been shown to reprogram tryptophan metabolism through the Kyn/XANA-AhR axis and reshape the immune microenvironment in colorectal cancer liver metastasis. Plasma metabolite studies in autosomal dominant tubulointerstitial kidney disease have associated kynurenine-related metabolites with chronic kidney disease stage, and kynurenine pathway biology is also discussed in cystic fibrosis and systemic lupus erythematosus contexts. These findings position L-kynurenine transmembrane transport as a tractable process for CRISPR-based functional genomics.
L-kynurenine transmembrane transport At A Glance
| GO ID | GO:0140924 |
|---|---|
| GO term | L-kynurenine transmembrane transport |
| Ontology | biological_process |
| Synonym | None listed |
| Definition | The directed movement of L-kynurenine across a membrane. |
| Major function | Membrane-mediated transfer of L-kynurenine between compartments, influencing kynurenine pathway flux and downstream signaling. |
| Representative transporters | SLC7A5 (LAT1) and related large neutral amino acid transporters. |
| Associated biology | Tryptophan catabolism, AhR signaling, immune microenvironment remodeling, epithelial amino acid handling. |
| Disease relevance | Colorectal cancer liver metastasis, chronic kidney disease, cystic fibrosis, systemic lupus erythematosus. |
What Is GO:0140924?
In this article, GO:0140924 (L-kynurenine transmembrane transport) is defined as the directed movement of L-kynurenine across a membrane. This includes transport across the plasma membrane and, where relevant, across intracellular membranes, and it is mediated by membrane proteins rather than by free diffusion. The term is a biological_process in the Gene Ontology and has no listed synonyms in the QuickGO record.
Why Is L-kynurenine transmembrane transport Important in Cell Biology?
L-kynurenine transmembrane transport is important because it controls the availability of a metabolite that sits at the branch point between neuroprotective and neurotoxic kynurenine pathway products and between immune activation and tolerance. When transporters such as SLC7A5 move L-kynurenine across membranes, they can feed the Kyn/XANA-AhR axis and reshape the immune microenvironment in tumors. In polarized epithelia, transport-coupled tryptophan depletion affects local immune signaling. Consequently, this GO term provides a mechanistic handle for understanding how metabolic transporters influence cancer progression, kidney disease, cystic fibrosis lung biology, and autoimmune conditions such as systemic lupus erythematosus.
• Defines a rate-controlling step in tryptophan catabolism by determining cellular and extracellular L-kynurenine levels.
• Links amino acid transporter activity to AhR-dependent transcriptional programs and immune microenvironment remodeling.
• Contributes to colorectal cancer liver metastasis through SLC7A5-dependent tryptophan metabolism reprogramming.
• Shapes epithelial immune regulation, as shown by apical tryptophan depletion in polarized human bronchial epithelium.
• Associates with chronic kidney disease stage through plasma kynurenine-related metabolites in autosomal dominant tubulointerstitial kidney disease.
• Relevant to cystic fibrosis lung biology and extrapulmonary effects discussed in therapeutic studies.
• Provides a metabolic rationale for N-acetylcysteine and redox-related interventions in systemic lupus erythematosus.
• Offers a target for CRISPR knockout, knock-in, and overexpression studies of transporter genes in disease models.
• Supports biomarker discovery through plasma metabolite profiling in kidney and metabolic disease.
• Connects evolutionary kynurenine biology, including impaired kynurenine formation and lifespan in Drosophila mutants, to conserved transport principles.
What Happens During L-kynurenine transmembrane transport?
Substrate recognition at the membrane
In simple terms: The transporter must first recognize L-kynurenine as a cargo to carry.
L-kynurenine is a large neutral amino acid-like metabolite, and transporters such as SLC7A5 can recognize it alongside other large neutral amino acids. This recognition step determines whether L-kynurenine competes with other substrates and whether transport is coupled to downstream metabolic enzymes. In polarized epithelium, apical transport activities contribute to tryptophan depletion and influence local kynurenine availability.
Translocation across the lipid bilayer
In simple terms: Once recognized, L-kynurenine is moved through the membrane from one side to the other.
The directed movement of L-kynurenine across a membrane is the defining event of GO:0140924. SLC7A5-dependent transport has been implicated in moving kynurenine in a way that supports the Kyn/XANA-AhR axis in colorectal cancer liver metastasis. This translocation step is distinct from passive diffusion and depends on membrane protein function.
Coupling to downstream kynurenine pathway flux
In simple terms: After transport, L-kynurenine becomes available for conversion into other metabolites.
Transported L-kynurenine can be converted to kynurenic acid, quinolinic acid, or xanthurenic acid, and can act as an AhR ligand depending on cellular context. In this way, transport is coupled to the metabolic fate of kynurenine and to transcriptional responses. Studies of tryptophan metabolism reprogramming highlight that transporter-mediated kynurenine availability can reshape the immune microenvironment.
Integration with epithelial and immune signaling
In simple terms: Transport changes the local environment and can alter immune cell behavior.
In polarized human bronchial epithelium, apical tryptophan depletion is a double mechanism that affects local metabolism and immune signaling. This illustrates how L-kynurenine transmembrane transport can be integrated with epithelial barrier function and immune regulation. Related kynurenine pathway biology has been discussed in cystic fibrosis and systemic lupus erythematosus contexts.
Systemic consequences and disease association
In simple terms: When transport goes wrong, metabolite levels change and disease can follow.
Plasma metabolites associated with chronic kidney disease stage in autosomal dominant tubulointerstitial kidney disease include kynurenine-related analytes, suggesting systemic consequences of altered kynurenine handling. In cancer, SLC7A5-mediated kynurenine transport promotes liver metastasis and immune microenvironment remodeling. These observations link GO:0140924 to clinically relevant outcomes.
Key Genes Involved in GO:0140924 L-kynurenine transmembrane transport
The following genes and proteins have been implicated in L-kynurenine transmembrane transport or in the kynurenine pathway biology that depends on this process, based on the verified literature.
| Gene | Major Role | Research Relevance |
|---|---|---|
| SLC7A5 | Large neutral amino acid transporter that can carry L-kynurenine across membranes | Central to Kyn/XANA-AhR axis and colorectal cancer liver metastasis |
| SLC3A2 | Heavy chain partner that can form heteromeric amino acid transporters with SLC7A5 | Supports transporter complex function in kynurenine handling |
| AHR | Aryl hydrocarbon receptor that responds to kynurenine pathway ligands | Links transport to transcriptional immune microenvironment remodeling |
| IDO1 | Enzyme that produces L-kynurenine from tryptophan | Upstream of transport-dependent kynurenine availability |
| IDO2 | Tryptophan-catabolizing enzyme related to kynurenine production | Context-dependent role in kynurenine pathway flux |
| TDO2 | Tryptophan 2,3-dioxygenase that generates L-kynurenine | Alternative source of kynurenine for transport studies |
| KYNU | Kynureninase that consumes L-kynurenine downstream | Determines metabolic fate after transport |
| KMO | Kynurenine 3-monooxygenase that metabolizes L-kynurenine | Shapes neuroactive metabolite balance after transport |
| CCBL1 | Kynurenine aminotransferase-related enzyme producing kynurenic acid | Downstream branch of transported kynurenine |
| CCBL2 | Kynurenine aminotransferase-related enzyme producing kynurenic acid | Downstream branch of transported kynurenine |
| SLC7A8 | Large neutral amino acid transporter family member | Potential alternative kynurenine transport route |
| SLC7A11 | Cystine/glutamate transporter family member | Related transporter biology in metabolic reprogramming |
| SLC1A5 | Neutral amino acid transporter family member | Candidate contributor to amino acid-linked kynurenine handling |
| SLC6A19 | Neutral amino acid transporter family member | Candidate transporter for kynurenine-related amino acid flux |
| SLC16A10 | Aromatic amino acid transporter family member | Potential aromatic amino acid transport route |
| SLC43A1 | Large neutral amino acid transporter family member | Candidate contributor to kynurenine transport |
| SLC43A2 | Large neutral amino acid transporter family member | Candidate contributor to kynurenine transport |
How Is L-kynurenine transmembrane transport Regulated?
L-kynurenine transmembrane transport is regulated at multiple levels. Transporter expression, including SLC7A5, can be modulated in cancer cells to support tryptophan metabolism reprogramming and Kyn/XANA-AhR signaling. Substrate availability from upstream enzymes such as IDO1 and TDO2 influences the amount of L-kynurenine available for transport. In epithelial contexts, apical transport activity and tryptophan depletion are coordinated with local immune signaling. Systemic metabolic states, such as those associated with chronic kidney disease stage, are also reflected in plasma kynurenine-related metabolite profiles. In addition, redox and inflammatory conditions relevant to systemic lupus erythematosus may influence kynurenine pathway activity and transport-dependent metabolite distribution.
L-kynurenine transmembrane transport and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| SLC7A5 | Colorectal cancer liver metastasis | SLC7A5 knockout and overexpression in colorectal cancer cell lines |
| AHR | Kyn/XANA-AhR axis and immune microenvironment | AHR knockout and reporter knock-in in cancer cells |
| IDO1 | Tryptophan catabolism and kynurenine production | IDO1 knockout and point-mutation models |
| KYNU | Downstream kynurenine metabolism | KYNU knockout to test metabolic fate after transport |
| SLC7A5 | Chronic kidney disease metabolite associations | Kidney epithelial cell models with transporter knockout |
Colorectal cancer liver metastasis
SLC7A5 promotes colorectal cancer liver metastasis by reprogramming tryptophan metabolism through the Kyn/XANA-AhR axis and reshaping the immune microenvironment. This directly implicates L-kynurenine transmembrane transport in metastatic progression and suggests that transporter inhibition or knockout could alter metastatic phenotypes.
Chronic kidney disease
Plasma metabolites associated with CKD stage in autosomal dominant tubulointerstitial kidney disease include kynurenine-related analytes, indicating that systemic kynurenine handling and transport may be altered in kidney disease. These findings support the use of metabolite profiling to link GO:0140924 to kidney disease progression.
Cystic fibrosis lung biology
Cystic fibrosis lung microbiome and extrapulmonary effects have been studied in relation to tryptophan and kynurenine pathway biology. Although direct transport mechanisms require further study, these papers provide context for how L-kynurenine transmembrane transport may contribute to airway and systemic phenotypes.
Systemic lupus erythematosus
Principles behind SLE treatment with N-acetylcysteine include redox and metabolic considerations that intersect with kynurenine pathway biology. This provides a rationale for investigating L-kynurenine transmembrane transport in autoimmune disease models.
From L-kynurenine transmembrane transport-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Is SLC7A5 required for L-kynurenine transmembrane transport? | SLC7A5 knockout cell line |
| Does a transporter point mutation alter substrate specificity? | Point-mutation knock-in of SLC7A5 |
| Can transporter overexpression increase kynurenine uptake? | SLC7A5 overexpression cell model |
| Where is the transporter localized in polarized cells? | Tagged knock-in with fluorescent tag |
| Which genes modify kynurenine transport phenotypes? | CRISPR library screening in cancer cell lines |
| How does transport affect AhR target genes? | AHR reporter knock-in combined with transporter knockout |
How to Study the L-kynurenine transmembrane transport Process
| Method | What It Measures | Typical Application |
|---|---|---|
| LC-MS metabolomics | Kynurenine and related metabolite levels | Plasma and cell culture metabolite profiling |
| RNA-seq | Transcriptional changes after transporter perturbation | Pathway and immune signature analysis |
| CRISPR knockout | Loss-of-function effects on transport | Causal testing of transporter genes |
| Overexpression | Gain-of-function effects on kynurenine uptake | Testing sufficiency of transporters |
| Tagged knock-in | Protein localization and trafficking | Polarized epithelial transport studies |
| CRISPR library screening | Genome-wide modifiers of transport phenotypes | Discovery of novel transport regulators |
| AhR reporter assay | AhR activation by kynurenine pathway ligands | Linking transport to transcriptional output |
Metabolite profiling and transport assays
L-kynurenine transmembrane transport can be studied by measuring kynurenine uptake or efflux using mass spectrometry-based metabolite profiling. Plasma metabolite studies in kidney disease illustrate how kynurenine-related analytes can be quantified in clinical samples. Such assays can be combined with transporter knockout or overexpression to establish causality.
Transcriptomics and pathway analysis
RNA-seq can reveal how transporter perturbation alters tryptophan metabolism and AhR target gene expression. SLC7A5-dependent reprogramming of tryptophan metabolism through the Kyn/XANA-AhR axis provides a template for such analyses. Pathway enrichment can connect transport changes to immune microenvironment signatures.
Imaging and localization
Fluorescent tagging of transporters enables visualization of membrane localization and trafficking. Polarized epithelial models, such as human bronchial epithelium, are useful for studying apical versus basolateral transport. Tagged knock-in cell lines can be used to track transporter dynamics.
Functional genomics and CRISPR screening
CRISPR knockout and library screening can identify genes that modify L-kynurenine transport and downstream phenotypes. This approach is well suited to cancer cell models where SLC7A5-dependent transport promotes metastasis. Screening can also uncover metabolic dependencies linked to kynurenine pathway flux.
How CRISPR Can Be Used to Study GO:0140924 L-kynurenine transmembrane transport
Knockout
CRISPR knockout of SLC7A5 or related transporters can test whether L-kynurenine transmembrane transport is required for downstream phenotypes such as AhR activation or metastasis. Knockout cell lines provide a clean background for rescue experiments with wild-type or mutant transporters.
Point Mutation
Point-mutation knock-in can dissect substrate recognition and transport mechanism by altering specific residues in transporter genes. Such models help determine whether a mutation affects kynurenine transport specifically or general amino acid transport.
Knock-in
Tagged knock-in of transporter genes enables localization and interaction studies in physiologically relevant cells. Knock-in of reporter cassettes downstream of AhR targets can link transport to transcriptional responses.
Overexpression
Overexpression of SLC7A5 or candidate transporters can test sufficiency for increased L-kynurenine transport and downstream metabolic reprogramming. Overexpression models are useful for validating transport-dependent phenotypes in cancer and epithelial cells.
How EDITGENE Supports L-kynurenine transmembrane transport Research
Researchers studying L-kynurenine transmembrane transport-related genes often need to determine whether a candidate gene is causally involved in kynurenine uptake, downstream AhR signaling, or disease phenotypes. EDITGENE provides CRISPR-based cell model services that enable such causal testing in a controlled and reproducible manner.
Contact EDITGENE today to design your custom CRISPR model for L-kynurenine transmembrane transport research.
Frequently Asked Questions About L-kynurenine transmembrane transport
What is L-kynurenine transmembrane transport?
It is the directed movement of L-kynurenine across a membrane, defined by GO:0140924 as a biological_process.
What genes are involved in L-kynurenine transmembrane transport?
SLC7A5 is a major transporter implicated in kynurenine transport, and related amino acid transporters may also contribute.
Why is L-kynurenine transport important in cancer?
SLC7A5 promotes colorectal cancer liver metastasis by reprogramming tryptophan metabolism through the Kyn/XANA-AhR axis.
How is L-kynurenine transmembrane transport studied?
It can be studied with metabolite profiling, RNA-seq, CRISPR knockout, overexpression, and imaging methods.
Is L-kynurenine transport linked to kidney disease?
Plasma metabolites associated with CKD stage in autosomal dominant tubulointerstitial kidney disease include kynurenine-related analytes.
What is the role of AhR in kynurenine transport?
AhR responds to kynurenine pathway ligands and links transport to transcriptional immune microenvironment remodeling.
Can CRISPR knockout be used to study kynurenine transporters?
Yes, CRISPR knockout of SLC7A5 or related genes can test whether transport is required for downstream phenotypes.
What cell models are suitable for kynurenine transport research?
Cancer cell lines, polarized epithelial cells, and kidney epithelial models are suitable depending on the research question.
Does kynurenine transport relate to cystic fibrosis?
Cystic fibrosis lung and extrapulmonary biology have been studied in relation to tryptophan and kynurenine pathways.
What GO ID represents L-kynurenine transmembrane transport?
The GO ID is GO:0140924, a biological_process term.
Conclusion
GO:0140924 (L-kynurenine transmembrane transport) defines a critical metabolic checkpoint that controls the distribution and downstream fate of L-kynurenine. Through transporters such as SLC7A5, this process influences AhR signaling, immune microenvironment remodeling, and disease phenotypes including colorectal cancer liver metastasis and kidney disease. Understanding its mechanism requires integrating transporter biochemistry with metabolic and transcriptional readouts. CRISPR-based cell models provide a powerful way to test causality for genes involved in L-kynurenine transmembrane transport. By combining knockout, point-mutation, knock-in, overexpression, and library screening approaches, researchers can dissect how specific transporters and pathway enzymes shape kynurenine biology in health and disease.
References
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- 3. Luo Y et al.. 2026. SLC7A5 promotes colorectal cancer liver metastasis by reprogramming tryptophan metabolism through the Kyn/XANA‒AhR axis and reshaping the immune microenvironment.. Clin Transl Med 16(8):e70766 PMID: 42563490
- 4. Zegarra-Moran O et al.. 2004. Double mechanism for apical tryptophan depletion in polarized human bronchial epithelium.. J Immunol 173(1):542-9 PMID: 15210815
- 5. Sosinski LM et al.. 2022. A restructuring of microbiome niche space is associated with Elexacaftor-Tezacaftor-Ivacaftor therapy in the cystic fibrosis lung.. J Cyst Fibros 21(6):996-1005 PMID: 34824018
- 6. Bellet MM et al.. 2021. Thymosin alpha 1 exerts beneficial extrapulmonary effects in cystic fibrosis.. Eur J Med Chem 209:112921 PMID: 33071052
- 7. Mušálková D et al.. 2026. Plasma Metabolites Associated with CKD Stage in Autosomal Dominant Tubulointerstitial Kidney Disease.. Kidney360 7(2):321-334 PMID: 41746789
- 8. Oxenkrug GF. 2010. The extended life span of Drosophila melanogaster eye-color (white and vermilion) mutants with impaired formation of kynurenine.. J Neural Transm (Vienna) 117(1):23-6 PMID: 19941150
