GO:0015175 neutral L-amino acid transmembrane transporter activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0015175 describes the molecular function of moving neutral L-amino acids across biological membranes, a process essential for nutrient uptake and inter-organ amino acid flux.
• The term covers transporters such as LAT1 (SLC7A5) and LAT2 (SLC7A8), which function as heterodimeric amino acid transporters.
• These transporters are stereoselective and can also recognize S-nitroso-L-cysteine, linking amino acid transport to nitric oxide biology.
• Dysregulation of neutral amino acid transporters is implicated in cancer metabolic reprogramming and neurological disorders.
• CRISPR knockout, point mutation, and overexpression models are key tools for dissecting the causal roles of these transporters.
• Understanding GO:0015175 supports research in cancer, neurodegeneration, and metabolic diseases.
Description
Neutral L-amino acid transmembrane transporter activity (GO:0015175) is a molecular function that enables the transfer of neutral L-amino acids across biological membranes. Neutral amino acids, such as leucine, isoleucine, valine, phenylalanine, tyrosine, tryptophan, and methionine, have side chains with no charge at physiological pH. This transport activity is critical for maintaining intracellular amino acid pools, supporting protein synthesis, and regulating metabolic signaling. The function is mediated by integral membrane proteins that form channels or carriers, often as heterodimeric complexes with a heavy subunit and a light subunit. Researchers study GO:0015175 to understand how cells acquire essential amino acids and how transport dysregulation contributes to diseases like cancer and neurodegeneration. The term is distinct from transporters of charged amino acids or other solutes, and its annotation is supported by experimental evidence of neutral amino acid flux across membranes.
neutral L-amino acid transmembrane transporter activity At A Glance
| GO ID | GO:0015175 |
|---|---|
| GO term | neutral L-amino acid transmembrane transporter activity |
| Ontology | molecular_function |
| Synonym | neutral amino acid transmembrane transporter activity; neutral amino acid transporter activity |
| Major function | Transfer of neutral L-amino acids across membranes |
| Substrates | Neutral L-amino acids such as leucine, isoleucine, valine, phenylalanine, tyrosine, tryptophan, methionine |
| Stereospecificity | L-enantiomers |
| Cellular location | Plasma membrane and possibly other organelle membranes |
| Representative genes | SLC7A5 (LAT1), SLC7A8 (LAT2), SLC43A1, SLC43A2 |
What Is GO:0015175?
In simple terms, GO:0015175 is the activity of proteins that carry neutral L-amino acids from one side of a membrane to the other. The official definition states: 'Enables the transfer of neutral L-amino acids from one side of a membrane to the other. Neutral amino acids have side chains with no charge at pH 7.3.' This activity is a molecular function, meaning it describes what a protein does at the biochemical level, rather than a broader biological process or cellular location. It includes transporters that are stereoselective for L-enantiomers and excludes those specific for charged or acidic/basic amino acids.
Why Is neutral L-amino acid transmembrane transporter activity Important in Cell Biology?
GO:0015175 is important because neutral amino acid transport is a fundamental cellular function that controls the availability of essential amino acids for protein synthesis and metabolic signaling. It influences processes such as mTORC1 activation, neurotransmitter synthesis, and redox homeostasis. Dysregulation of these transporters has been linked to cancer progression, where tumor cells upregulate amino acid uptake to sustain growth, and to neurological disorders where altered transport affects synaptic function. Studying this activity provides insights into nutrient sensing, metabolic diseases, and potential therapeutic targets.
• Essential for uptake of branched-chain and aromatic amino acids required for protein synthesis.
• Regulates mTORC1 signaling by controlling intracellular leucine levels.
• Involved in nitric oxide biology through transport of S-nitroso-L-cysteine.
• Implicated in cancer metabolic reprogramming and tumor growth.
• Linked to neurological disorders such as autism and epilepsy.
• Potential target for drug delivery across the blood-brain barrier.
• Plays a role in immune cell activation and inflammation.
• Contributes to redox balance via cysteine and methionine transport.
• Affects drug pharmacokinetics by transporting amino acid-mimetic drugs.
• Provides a model for studying membrane protein structure-function relationships.
Molecular Mechanism of neutral L-amino acid transmembrane transporter activity
Substrate Recognition and Binding
In simple terms: The transporter first grabs the amino acid it will carry.
Neutral L-amino acid transporters recognize their substrates through specific binding pockets that accommodate the amino acid backbone and neutral side chain. For example, LAT1 and LAT2 form heterodimers with the 4F2hc (SLC3A2) subunit and exhibit stereoselective binding for L-enantiomers. The binding site excludes charged amino acids, ensuring specificity for neutral side chains.
Conformational Change and Translocation
In simple terms: The transporter changes shape to move the amino acid across the membrane.
Upon substrate binding, the transporter undergoes conformational changes that expose the substrate to the opposite side of the membrane. This alternating access mechanism is typical of solute carriers. For LAT1 and LAT2, transport is sodium-independent and involves exchange of intracellular amino acids for extracellular ones. The process is driven by concentration gradients and membrane potential.
Substrate Release and Reset
In simple terms: The amino acid is released inside the cell, and the transporter resets.
After translocation, the neutral L-amino acid is released into the cytoplasm, and the transporter returns to its original conformation to initiate another cycle. This cycle can be regulated by intracellular substrate concentrations and interacting proteins. The release step is critical for maintaining directional transport and preventing backflow.
Heterodimeric Assembly and Regulation
In simple terms: Many transporters work as pairs of proteins, and their activity can be tuned.
LAT1 and LAT2 require association with the heavy chain 4F2hc for proper membrane localization and function. This heterodimeric assembly is essential for transport activity. Regulation occurs at multiple levels, including transcriptional control, post-translational modifications, and interaction with accessory proteins. For instance, S-nitroso-L-cysteine transport by these transporters links amino acid transport to nitric oxide signaling.
Key Genes Involved in GO:0015175 neutral L-amino acid transmembrane transporter activity
The following genes encode proteins that exhibit neutral L-amino acid transmembrane transporter activity or are directly involved in its regulation.
| Gene | Major Role | Research Relevance |
|---|---|---|
| SLC7A5 | Light subunit of LAT1 transporter; mediates neutral amino acid transport | Cancer metabolism, drug delivery, mTORC1 signaling |
| SLC7A8 | Light subunit of LAT2 transporter; broad neutral amino acid specificity | Neurological disorders, amino acid homeostasis |
| SLC3A2 | Heavy subunit (4F2hc) that associates with LAT1/LAT2 for membrane localization | Essential for transporter function; cancer target |
| SLC43A1 | L-type amino acid transporter 3 (LAT3); transports neutral amino acids | Metabolic diseases, cancer |
| SLC43A2 | L-type amino acid transporter 4 (LAT4); neutral amino acid transport | Nutrient sensing, immune function |
| SLC1A5 | Neutral amino acid transporter ASCT2; transports glutamine and other neutral amino acids | Cancer metabolism, glutamine addiction |
| SLC6A19 | Neutral amino acid transporter B0AT1; kidney and intestine amino acid reabsorption | Hartnup disorder, metabolic diseases |
| SLC6A15 | Neutral amino acid transporter B0AT2; brain-specific | Neurotransmission, psychiatric disorders |
| SLC7A10 | Asc-1 transporter; neutral amino acid exchange | Neurotransmitter synthesis, synaptic function |
| SLC7A11 | Cystine/glutamate antiporter; related to neutral amino acid transport | Redox balance, cancer |
| SLC38A1 | System A transporter; neutral amino acid uptake | Cancer, mTORC1 signaling |
| SLC38A2 | System A transporter; neutral amino acid uptake | Cell growth, metabolism |
| SLC38A5 | System N transporter; neutral amino acid transport | Cancer, immune response |
| SLC16A10 | Aromatic amino acid transporter TAT1; neutral amino acid transport | Thyroid hormone metabolism, cancer |
| SLC3A1 | Heavy subunit for cystine/neutral amino acid transporters | Cystinuria, amino acid transport |
| SLC7A9 | Light subunit for cystine/neutral amino acid transporters | Cystinuria, amino acid transport |
| SLC25A15 | Mitochondrial neutral amino acid transporter | Hyperornithinemia-hyperammonemia-homocitrullinuria syndrome |
How Is neutral L-amino acid transmembrane transporter activity Regulated?
The activity of neutral L-amino acid transporters is regulated at multiple levels. Transcriptional regulation by nutrient-sensing pathways such as mTORC1 and ATF4 controls the expression of genes like SLC7A5 and SLC7A11. Post-translational modifications, including phosphorylation and ubiquitination, modulate transporter stability and trafficking. Interaction with accessory proteins such as 4F2hc is required for membrane localization and function. Additionally, substrate availability and competitive inhibition by other amino acids influence transport rates. Hormonal signals, such as insulin, can also affect amino acid transport activity.
neutral L-amino acid transmembrane transporter activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| SLC7A5 | Cancer (e.g., glioma, lung cancer) | Knockout in cancer cell lines; xenograft models |
| SLC7A8 | Neurological disorders (autism, epilepsy) | Knockout mice; neuronal cell models |
| SLC6A19 | Hartnup disorder | Knockout mice; intestinal epithelial cells |
| SLC3A1 | Cystinuria | Knockout mice; kidney cell lines |
| SLC7A11 | Cancer, oxidative stress | Knockout in cancer cells; overexpression models |
Cancer Metabolism and Tumor Growth
Neutral L-amino acid transporters are frequently upregulated in cancer to support the increased demand for amino acids needed for protein synthesis and energy production. LAT1 (SLC7A5) is overexpressed in many cancers and correlates with poor prognosis. Targeting these transporters is a promising therapeutic strategy, as inhibition can starve tumor cells of essential amino acids.
Neurological Disorders
In the brain, neutral L-amino acid transporters regulate the availability of amino acids that serve as precursors for neurotransmitters such as serotonin and dopamine. Dysfunction of LAT2 (SLC7A8) has been linked to neurological disorders, including autism spectrum disorders and epilepsy. Transporters like SLC6A15 are associated with major depressive disorder.
Metabolic and Renal Disorders
Mutations in neutral amino acid transporters can cause metabolic disorders. For example, mutations in SLC6A19 cause Hartnup disorder, characterized by impaired renal and intestinal reabsorption of neutral amino acids. Similarly, defects in SLC3A1 and SLC7A9 lead to cystinuria, a condition of impaired cystine reabsorption.
From neutral L-amino acid transmembrane transporter activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of SLC7A5 reduce tumor growth? | CRISPR knockout in cancer cell lines and mouse xenografts |
| What is the effect of a point mutation in the substrate binding site of LAT1? | CRISPR point mutation knock-in in cell lines |
| Can overexpression of SLC7A8 rescue transport defects? | CRISPR overexpression (CRISPRa) in neuronal cells |
| How does tagging SLC3A2 affect transporter localization? | Knock-in of fluorescent tag (e.g., GFP) |
| What is the role of SLC6A19 in amino acid homeostasis? | Knockout mouse models |
| Can CRISPR library screening identify modifiers of amino acid transport? | Genome-wide CRISPR knockout library in cancer cells |
How to Study the neutral L-amino acid transmembrane transporter activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Radiolabeled amino acid uptake | Transport activity and kinetics | Functional characterization of transporters |
| CRISPR knockout | Loss-of-function phenotypes | Identifying essential transporters in cancer cells |
| Co-immunoprecipitation + MS | Protein-protein interactions | Identifying heterodimeric partners |
| Metabolomics | Intracellular amino acid levels | Assessing metabolic impact of transport inhibition |
| RNA-seq | Transcriptional changes | Measuring expression of transporter genes |
| Western blot | Protein expression and modification | Validating knockout or overexpression |
| Immunofluorescence | Subcellular localization | Determining membrane localization of transporters |
| CRISPR library screening | Genome-wide fitness effects | Identifying synthetic lethal interactions |
Transport Assays
Radiolabeled or fluorescent amino acid uptake assays are used to measure neutral L-amino acid transport activity directly. Cells expressing the transporter of interest are incubated with labeled substrates, and uptake is quantified. This method is essential for validating transporter function and kinetics.
Genetic Knockout and Knockdown
CRISPR-Cas9 knockout or RNA interference knockdown of specific transporter genes allows researchers to assess loss-of-function phenotypes. These approaches can reveal the contribution of individual transporters to amino acid uptake and downstream processes.
Proteomics and Interactomics
Mass spectrometry-based proteomics can identify interacting partners of neutral amino acid transporters, such as the 4F2hc heavy chain. Co-immunoprecipitation followed by mass spectrometry reveals the composition of transporter complexes.
Metabolic Profiling
Metabolomics and flux analysis measure changes in intracellular amino acid pools and metabolic pathways upon modulation of transporter activity. This provides a systems-level view of the role of GO:0015175 in cellular metabolism.
How CRISPR Can Be Used to Study GO:0015175 neutral L-amino acid transmembrane transporter activity
Knockout
CRISPR knockout of genes encoding neutral L-amino acid transporters, such as SLC7A5 or SLC7A8, is used to study loss of transport activity. This approach can reveal whether a specific transporter is required for cell growth, amino acid homeostasis, or disease phenotypes.
Point Mutation
Introducing point mutations in the substrate binding site or regulatory domains of transporters via CRISPR can dissect structure-function relationships. For example, mutating residues critical for substrate recognition can abolish transport activity and provide insights into mechanism.
Knock-in
Knock-in of epitope tags or fluorescent proteins allows visualization and purification of transporters. This is useful for studying localization, trafficking, and interaction partners in native contexts.
Overexpression
CRISPR activation (CRISPRa) or cDNA overexpression can increase transporter levels to study gain-of-function effects, such as enhanced amino acid uptake and downstream signaling. This is particularly relevant for cancer models where transporter upregulation is common.
How EDITGENE Supports neutral L-amino acid transmembrane transporter activity Research
Researchers studying neutral L-amino acid transmembrane transporter activity-related genes often need to determine whether a candidate gene is causally involved in amino acid transport, metabolic reprogramming, or disease progression. EDITGENE provides comprehensive CRISPR-based services to generate precisely engineered cell models, enabling rigorous functional validation of transporters and their regulatory networks.
Contact EDITGENE today to design your custom CRISPR model for neutral L-amino acid transmembrane transporter activity research.
Frequently Asked Questions About neutral L-amino acid transmembrane transporter activity
What is GO:0015175?
GO:0015175 is a Gene Ontology molecular function term that describes the activity of transferring neutral L-amino acids across a membrane. It includes transporters specific for amino acids with uncharged side chains at pH 7.3.
What genes are involved in neutral L-amino acid transmembrane transporter activity?
Key genes include SLC7A5 (LAT1), SLC7A8 (LAT2), SLC3A2 (4F2hc), SLC43A1, SLC43A2, SLC6A19, and SLC38A1, among others.
How is neutral L-amino acid transport regulated?
It is regulated transcriptionally by nutrient-sensing pathways like mTORC1, post-translationally by phosphorylation, and through interaction with accessory proteins such as 4F2hc.
What diseases are associated with neutral L-amino acid transporters?
They are implicated in cancer, neurological disorders like autism and epilepsy, and metabolic disorders such as Hartnup disorder and cystinuria.
What methods are used to study neutral L-amino acid transport?
Common methods include radiolabeled uptake assays, CRISPR knockout, proteomics, metabolomics, and RNA-seq.
Can CRISPR be used to study neutral L-amino acid transporters?
Yes, CRISPR knockout, point mutation, knock-in, and overexpression are powerful tools to dissect the function of these transporters in cell models.
What is the role of LAT1 in cancer?
LAT1 (SLC7A5) is often overexpressed in cancer to support increased amino acid uptake for growth and survival, making it a potential therapeutic target.
How does S-nitroso-L-cysteine relate to neutral amino acid transport?
S-nitroso-L-cysteine is transported by LAT1 and LAT2, linking neutral amino acid transport to nitric oxide signaling and vascular biology.
What is Hartnup disorder?
Hartnup disorder is caused by mutations in SLC6A19, leading to impaired renal and intestinal reabsorption of neutral amino acids.
Why is GO:0015175 important for drug development?
Many drugs mimic amino acids and rely on these transporters for uptake. Understanding transport activity can inform drug design and delivery, especially across the blood-brain barrier.
Conclusion
GO:0015175 neutral L-amino acid transmembrane transporter activity is a fundamental molecular function that governs the movement of essential amino acids into and out of cells. Its dysregulation is linked to major diseases, including cancer and neurological disorders, making it a compelling area of research. By leveraging CRISPR-based models and advanced analytical methods, researchers can uncover the precise roles of individual transporters and develop targeted therapies. EDITGENE provides the tools and expertise to accelerate these discoveries.
References
- 1. Li S et al.. 2007. Functional characterization of two S-nitroso-L-cysteine transporters, which mediate movement of NO equivalents into vascular cells.. Am J Physiol Cell Physiol 292(4):C1263-71 PMID: 17092994
- 2. Li S et al.. 2005. Identification of stereoselective transporters for S-nitroso-L-cysteine: role of LAT1 and LAT2 in biological activity of S-nitrosothiols.. J Biol Chem 280(20):20102-10 PMID: 15769744
