GO:0005314 high-affinity L-glutamate transmembrane transporter activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0005314 defines high-affinity L-glutamate transmembrane transporter activity, a molecular function that moves glutamate across membranes even at very low concentrations.
• The transporters are sodium-dependent and belong to the SLC1 family, including GLAST-1 (EAAT1), EAAC1 (EAAT3), and EAAT4.
• High-affinity glutamate transport is essential for terminating glutamatergic neurotransmission and preventing excitotoxicity in the brain and retina.
• Key structural determinants include conserved aspartate residues and N-glycosylation sites that tune substrate affinity and sodium coupling.
• Dysfunction of these transporters is linked to neurodegeneration, epilepsy, and retinal degeneration, making them therapeutic targets.
• CRISPR-based knockout, point mutation, and knock-in models enable precise dissection of transporter function in vitro and in vivo.
Description
High-affinity L-glutamate transmembrane transporter activity (GO:0005314) is a molecular function that enables the transfer of glutamate across biological membranes even when the solute is present at very low concentrations. This activity is critical for maintaining low extracellular glutamate levels, thereby preventing excitotoxic neuronal damage and ensuring proper synaptic signaling. The transporters responsible for this function are sodium-dependent and belong to the solute carrier family SLC1, which includes GLAST-1 (EAAT1), GLT-1 (EAAT2), EAAC1 (EAAT3), and EAAT4. Researchers study these transporters to understand glutamate homeostasis, synaptic plasticity, and the pathophysiology of neurological disorders. The high-affinity nature of these transporters allows them to efficiently clear glutamate from the synaptic cleft, a process that is essential for normal brain function.
high-affinity L-glutamate transmembrane transporter activity At A Glance
| GO ID | GO:0005314 |
|---|---|
| GO term | high-affinity L-glutamate transmembrane transporter activity |
| Ontology | molecular_function |
| Synonym | high-affinity glutamate transmembrane transporter activity; high-affinity glutamate transporter activity |
| Major function | Sodium-dependent transport of L-glutamate across membranes at low substrate concentrations |
| Major genes | SLC1A1 (EAAC1), SLC1A2 (GLT-1), SLC1A3 (GLAST-1), SLC1A6 (EAAT4) |
| Cellular location | Plasma membrane of neurons and glial cells |
| Associated diseases | Neurodegeneration, epilepsy, retinal degeneration, excitotoxicity |
| Research methods | Site-directed mutagenesis, electrophysiology, uptake assays, CRISPR knockout |
What Is GO:0005314?
GO:0005314 describes the activity of a transporter protein that moves L-glutamate across a membrane against its concentration gradient or down its electrochemical gradient, with the ability to bind glutamate even at very low concentrations. This high-affinity binding is typically coupled to sodium ion transport, and the activity is distinct from low-affinity glutamate transporters or vesicular glutamate transporters.
Why Is high-affinity L-glutamate transmembrane transporter activity Important in Cell Biology?
High-affinity L-glutamate transporters are the primary mechanism for clearing glutamate from the synaptic cleft, and their dysfunction leads to excitotoxic neuronal death, which is implicated in stroke, epilepsy, and neurodegenerative diseases. Understanding their molecular function is essential for developing therapies that modulate glutamatergic signaling.
• Prevents excitotoxicity by maintaining low extracellular glutamate.
• Regulates synaptic plasticity and learning and memory.
• Mutations in SLC1A3 cause episodic ataxia and retinal degeneration.
• Dysfunction is linked to amyotrophic lateral sclerosis and epilepsy.
• Target for neuroprotective drugs and glutamate modulators.
• Essential for retinal glutamate clearance and vision.
• Involved in astrocyte-neuron metabolic coupling.
• Provides a model for studying sodium-coupled transport mechanisms.
• High-affinity transport is critical for low-concentration signaling.
• CRISPR models enable precise functional dissection.
What Happens During high-affinity L-glutamate transmembrane transporter activity?
Substrate Binding and Sodium Coupling
In simple terms: The transporter grabs glutamate and sodium ions from outside the cell.
High-affinity glutamate transporters bind L-glutamate with high affinity even at nanomolar concentrations, a process that is coupled to the binding of sodium ions. Conserved aspartate residues, such as aspartate 439 in EAAC1, are critical for high-affinity sodium binding and cooperate with the substrate to stabilize the transporter in a substrate-bound state. Site-directed mutagenesis of GLAST-1 has shown that specific residues are required for sodium-dependent glutamate transport.
Translocation and Counter-transport
In simple terms: The transporter moves glutamate into the cell while exchanging sodium and potassium ions.
After binding, the transporter undergoes conformational changes that translocate glutamate across the membrane, coupled to the inward movement of sodium and the outward movement of potassium. EAAT4 and EAATs 1-3 share a common uptake mechanism but exhibit dramatically different kinetics and voltage dependence, indicating that the translocation step is finely tuned. This counter-transport mechanism ensures efficient glutamate clearance.
Glutamate Clearance and Termination of Signaling
In simple terms: The transporter removes glutamate from the synapse to stop the signal.
In the retina, GLAST-1 plays a major role in transmitter clearance, and high-affinity glutamate transporters are essential for terminating glutamatergic neurotransmission. Astrocytes contribute to this process by maintaining and modulating glutamatergic and GABAergic neurotransmission through high-affinity uptake. This clearance prevents prolonged receptor activation and excitotoxicity.
Regulation by Glycosylation and Protein Interactions
In simple terms: Sugar molecules attached to the transporter affect its function.
N-glycosylation sites on GLAST-1 have been localized, and the carbohydrate units play a functional role in the transporter's activity. These post-translational modifications can influence transporter stability, trafficking, and affinity. Additionally, the conserved aspartate 439 and bound amino acid substrate are important for high-affinity sodium binding, linking structural features to regulation.
Key Genes Involved in GO:0005314 high-affinity L-glutamate transmembrane transporter activity
The following genes encode proteins that exhibit high-affinity L-glutamate transmembrane transporter activity or are directly involved in its regulation.
| Gene | Major Role | Research Relevance |
|---|---|---|
| SLC1A3 (GLAST-1) | Glial high-affinity glutamate transporter; clears glutamate in brain and retina | Site-directed mutagenesis, N-glycosylation studies, retinal clearance |
| SLC1A1 (EAAC1) | Neuronal high-affinity glutamate transporter; sodium-dependent uptake | Aspartate 439 and sodium binding studies |
| SLC1A2 (GLT-1) | Astrocytic high-affinity glutamate transporter; major clearance in forebrain | Astrocyte-neuron coupling, excitotoxicity models |
| SLC1A6 (EAAT4) | High-affinity glutamate transporter with distinct kinetics and voltage dependence | Kinetic and voltage-dependence studies |
| SLC1A7 (EAAT5) | Retinal high-affinity glutamate transporter | Retinal neurotransmission |
| SLC17A6 (VGLUT2) | Vesicular glutamate transporter (low-affinity, not GO:0005314) | Vesicular transport regulation |
| SLC17A7 (VGLUT1) | Vesicular glutamate transporter (low-affinity, not GO:0005314) | Vesicular transport regulation |
| SLC17A8 (VGLUT3) | Vesicular glutamate transporter (low-affinity, not GO:0005314) | Vesicular transport regulation |
| ATP1A1 | Na+/K+-ATPase subunit; maintains sodium gradient for transport | Energy transduction and sodium gradient |
| ATP1A2 | Na+/K+-ATPase subunit; supports sodium-coupled transport | Sodium gradient maintenance |
| ATP1A3 | Na+/K+-ATPase subunit; neuronal sodium homeostasis | Sodium gradient maintenance |
| ATP1B1 | Na+/K+-ATPase beta subunit; regulates pump activity | Energy transduction |
| ATP1B2 | Na+/K+-ATPase beta subunit; glial sodium regulation | Sodium gradient maintenance |
| ATP1B3 | Na+/K+-ATPase beta subunit; modulates transport capacity | Energy transduction |
| SLC25A12 | Mitochondrial aspartate-glutamate carrier; supports glutamate homeostasis | Metabolic coupling |
| SLC25A13 | Mitochondrial aspartate-glutamate carrier; involved in glutamate cycling | Metabolic coupling |
| GLS | Glutaminase; produces glutamate for transport | Glutamate synthesis and supply |
| GLUL | Glutamine synthetase; converts glutamate to glutamine in astrocytes | Glutamate recycling |
How Is high-affinity L-glutamate transmembrane transporter activity Regulated?
High-affinity L-glutamate transporter activity is regulated at multiple levels. Sodium and potassium gradients maintained by Na+/K+-ATPase provide the driving force for transport, and the structure-function relationships of Na,K-ATPase directly impact energy transduction for coupled transport. Post-translational modifications such as N-glycosylation on GLAST-1 modulate transporter function and stability. Additionally, the conserved aspartate 439 and bound substrate cooperate to regulate high-affinity sodium binding, influencing transport kinetics. Astrocytes dynamically modulate glutamatergic neurotransmission by regulating transporter expression and activity.
high-affinity L-glutamate transmembrane transporter activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| SLC1A3 (GLAST-1) | Retinal degeneration, episodic ataxia | Knockout mouse, point mutation knock-in |
| SLC1A1 (EAAC1) | Epilepsy, neurodegeneration | Conditional knockout, overexpression |
| SLC1A2 (GLT-1) | ALS, epilepsy, excitotoxicity | Astrocyte-specific knockout, knock-in |
| SLC1A6 (EAAT4) | Cerebellar dysfunction | Point mutation, electrophysiology |
| ATP1A1 | Neurological disorders due to sodium gradient failure | Knockout, point mutation |
Excitotoxicity and Neurodegeneration
Impaired high-affinity glutamate transport leads to elevated extracellular glutamate, causing excitotoxic neuronal death. This mechanism is implicated in amyotrophic lateral sclerosis, Alzheimer's disease, and epilepsy. GLAST-1 dysfunction in the retina results in glutamate accumulation and retinal degeneration.
Epilepsy and Seizure Susceptibility
Reduced glutamate transporter activity can cause hyperexcitability and seizures. Astrocytic glutamate transporters are critical for maintaining low synaptic glutamate, and their dysfunction is associated with epilepsy.
Retinal Degeneration
GLAST-1 is a major glutamate transporter in the retina, and its loss leads to impaired transmitter clearance and retinal damage. Mutations affecting transporter function can cause visual deficits.
Therapeutic Targeting
Modulating high-affinity glutamate transporters is a therapeutic strategy for neurological disorders. Pharmacological regulation of vesicular and plasma membrane transporters is an active area of research.
From high-affinity L-glutamate transmembrane transporter activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of GLAST-1 impair retinal glutamate clearance? | SLC1A3 knockout mouse or retinal organoids |
| How does aspartate 439 affect sodium binding? | EAAC1 point mutation (D439N) in cell lines |
| What is the effect of N-glycosylation on GLAST-1 function? | Site-directed mutagenesis of N-glycosylation sites |
| Can overexpression of GLT-1 rescue excitotoxicity? | Astrocyte-specific overexpression in vivo |
| What are the kinetic differences between EAAT4 and EAAT1-3? | Knock-in of EAAT4 into EAAT3 locus |
| How does Na+/K+-ATPase dysfunction affect transport? | ATP1A1 knockout or point mutation |
How to Study the high-affinity L-glutamate transmembrane transporter activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Radiolabeled glutamate uptake | Transport rate and affinity | Characterizing high-affinity transporters |
| Patch-clamp electrophysiology | Transport currents and voltage dependence | Kinetic analysis of EAATs |
| Site-directed mutagenesis | Role of specific residues in transport | Aspartate 439 and sodium binding |
| CRISPR knockout | Loss-of-function phenotypes | Retinal clearance studies |
| CRISPR knock-in | Disease variant effects | Point mutation models |
| Immunohistochemistry | Cellular localization | Retinal GLAST-1 localization |
| Western blot | Protein expression levels | N-glycosylation analysis |
| Na+/K+-ATPase activity assay | Sodium gradient maintenance | Energy transduction studies |
Electrophysiology and Uptake Assays
Patch-clamp recordings and radiolabeled glutamate uptake assays measure transport kinetics, voltage dependence, and affinity. These methods have been used to characterize EAAT4 and EAATs 1-3 and to study sodium coupling in EAAC1.
Site-Directed Mutagenesis
Mutating conserved residues such as aspartate 439 or N-glycosylation sites reveals their role in high-affinity transport. This approach was applied to GLAST-1 and EAAC1.
CRISPR-Cas9 Knockout and Knock-in
CRISPR enables generation of knockout cell lines and animals to study loss of transporter function, as well as knock-in of point mutations to mimic disease variants.
Immunohistochemistry and Imaging
Localization of transporters in retina and brain is achieved by immunohistochemistry, as shown for GLAST-1 in the rat retina. Live-cell imaging can track transporter trafficking.
How CRISPR Can Be Used to Study GO:0005314 high-affinity L-glutamate transmembrane transporter activity
Knockout
CRISPR knockout of SLC1A3 or SLC1A1 eliminates high-affinity glutamate transport, allowing researchers to study excitotoxicity and retinal degeneration. Knockout models are essential for validating the role of specific transporters in glutamate clearance.
Point Mutation
Introducing point mutations such as D439N in EAAC1 or mutations in N-glycosylation sites of GLAST-1 enables precise dissection of sodium coupling and substrate affinity. These models mimic human disease variants.
Knock-in
Knock-in of reporter tags or disease-associated alleles allows tracking of transporter localization and function in vivo. For example, tagging GLAST-1 with fluorescent proteins facilitates live imaging.
Overexpression
Overexpression of GLT-1 or GLAST-1 can rescue glutamate clearance deficits and protect against excitotoxicity. Overexpression models are useful for testing neuroprotective strategies.
How EDITGENE Supports high-affinity L-glutamate transmembrane transporter activity Research
Researchers studying high-affinity L-glutamate transmembrane transporter activity-related genes often need to determine whether a candidate gene is causally involved in glutamate clearance, excitotoxicity, or neurological disease. EDITGENE provides comprehensive CRISPR-based services to accelerate this research.
Contact EDITGENE today to design your custom CRISPR model for high-affinity L-glutamate transmembrane transporter activity research.
Related Products
| Product name | Cat.No. | Species | Gene ID | |
|---|---|---|---|---|
| SLC1A3 Knockout HEK293 Cell Line | EDJ-KQ2547 | Human | 6507 | Details Get a Quote |
| SLC1A2 Knockout HEK293 Cell Line | EDJ-KQ2658 | Human | 6506 | Details Get a Quote |
| SLC1A1 Knockout HEK293 Cell Line | EDJ-KQ5760 | Human | 6505 | Details Get a Quote |
| SLC1A6 Knockout HEK293 Cell Line | EDJ-KQ5761 | Human | 6511 | Details Get a Quote |
| SLC1A7 Knockout HEK293 Cell Line | EDJ-KQ5764 | Human | 6512 | Details Get a Quote |
| SLC1A1 Knockout A-549 Cell Line | EDJ-KQ29174 | Human | 6505 | Details Get a Quote |
| SLC1A1 Knockout HCT 116 Cell Line | EDJ-KQ29175 | Human | 6505 | Details Get a Quote |
| SLC1A1 Knockout HeLa Cell Line | EDJ-KQ29176 | Human | 6505 | Details Get a Quote |
| SLC1A3 Knockout HCT 116 Cell Line | EDJ-KQ24577 | Human | 6507 | Details Get a Quote |
| SLC1A3 Knockout HeLa Cell Line | EDJ-KQ24578 | Human | 6507 | Details Get a Quote |
| SLC1A2 Knockout HeLa Cell Line | EDJ-KQ54478 | Human | 6506 | Details Get a Quote |
| SLC1A6 Knockout HeLa Cell Line | EDJ-KQ54480 | Human | 6511 | Details Get a Quote |
| SLC1A7 Knockout HeLa Cell Line | EDJ-KQ54481 | Human | 6512 | Details Get a Quote |
| SLC1A2 Knockout A-549 Cell Line | EDJ-KQ62964 | Human | 6506 | Details Get a Quote |
| SLC1A3 Knockout A-549 Cell Line | EDJ-KQ62965 | Human | 6507 | Details Get a Quote |
Displaying Records 1 To 15 Of 20 Records
Frequently Asked Questions About high-affinity L-glutamate transmembrane transporter activity
What is high-affinity L-glutamate transmembrane transporter activity?
It is a molecular function (GO:0005314) that enables the transfer of glutamate across membranes even at very low concentrations, typically coupled to sodium transport.
What genes are involved in high-affinity L-glutamate transport?
Key genes include SLC1A1 (EAAC1), SLC1A2 (GLT-1), SLC1A3 (GLAST-1), and SLC1A6 (EAAT4).
How does high-affinity glutamate transport prevent excitotoxicity?
By rapidly clearing glutamate from the synaptic cleft, it prevents prolonged activation of glutamate receptors that can lead to neuronal death.
What diseases are associated with defective glutamate transporters?
Neurodegeneration, epilepsy, retinal degeneration, and amyotrophic lateral sclerosis have been linked to transporter dysfunction.
What is the role of GLAST-1 in the retina?
GLAST-1 is a major glial glutamate transporter in the retina that clears transmitter to protect against excitotoxicity.
How is sodium coupled to glutamate transport?
Sodium binding to conserved residues such as aspartate 439 is essential for high-affinity glutamate uptake.
What are the differences between EAAT4 and EAAT1-3?
EAAT4 and EAATs 1-3 share a common uptake mechanism but have dramatically different kinetics and voltage dependence.
How can CRISPR be used to study glutamate transporters?
CRISPR knockout, point mutation, and knock-in models allow precise manipulation of transporter genes to study function and disease.
What is the role of N-glycosylation in GLAST-1 function?
N-glycosylation sites on GLAST-1 are important for its functional activity and stability.
How does Na+/K+-ATPase support glutamate transport?
Na+/K+-ATPase maintains the sodium gradient that drives high-affinity glutamate transport.
Conclusion
High-affinity L-glutamate transmembrane transporter activity (GO:0005314) is a fundamental molecular function that safeguards the nervous system by clearing glutamate from synapses. The transporters responsible, including GLAST-1, EAAC1, GLT-1, and EAAT4, are critical for preventing excitotoxicity and maintaining normal neurotransmission. Dysregulation of these transporters is implicated in a range of neurological and retinal diseases, making them important therapeutic targets. Advances in CRISPR-based models and structural biology continue to unravel the molecular details of this essential transport activity.
References
- 1. Conradt M et al.. 1995. Functional analysis of the high affinity, Na(+)-dependent glutamate transporter GLAST-1 by site-directed mutagenesis.. J Biol Chem 270(42):25207-12 PMID: 7559657
- 2. Rauen T et al.. 1998. High-affinity glutamate transporters in the rat retina: a major role of the glial glutamate transporter GLAST-1 in transmitter clearance.. Cell Tissue Res 291(1):19-31 PMID: 9394040
- 3. Pietrancosta N et al.. 2020. Molecular, Structural, Functional, and Pharmacological Sites for Vesicular Glutamate Transporter Regulation.. Mol Neurobiol 57(7):3118-3142 PMID: 32474835
- 4. Tao Z et al.. 2007. Cooperation of the conserved aspartate 439 and bound amino acid substrate is important for high-affinity Na+ binding to the glutamate transporter EAAC1.. J Gen Physiol 129(4):331-44 PMID: 17389249
- 5. Mim C et al.. 2005. The glutamate transporter subtypes EAAT4 and EAATs 1-3 transport glutamate with dramatically different kinetics and voltage dependence but share a common uptake mechanism.. J Gen Physiol 126(6):571-89 PMID: 16316976
- 6. Schousboe A. 2003. Role of astrocytes in the maintenance and modulation of glutamatergic and GABAergic neurotransmission.. Neurochem Res 28(2):347-52 PMID: 12608708
- 7. Conradt M et al.. 1995. Localization of N-glycosylation sites and functional role of the carbohydrate units of GLAST-1, a cloned rat brain L-glutamate/L-aspartate transporter.. Eur J Biochem 229(3):682-7 PMID: 7758463
- 8. Jorgensen PL et al.. 2001. Structure-function relationships of Na(+), K(+), ATP, or Mg(2+) binding and energy transduction in Na,K-ATPase.. Biochim Biophys Acta 1505(1):57-74 PMID: 11248189
