GO:0015172 acidic amino acid transmembrane transporter activity: Mechanism, Genes and Research Methods
Research-grade guide for scientists and biopharma professionals
Key Takeaways
• GO:0015172 describes the molecular function of moving acidic amino acids (aspartate and glutamate) across biological membranes.
• SLC1 family transporters are the principal proteins that carry out this activity in humans, using a secondary-active, sodium-dependent mechanism.
• The transport cycle involves alternating access of the substrate-binding site between outward- and inward-facing conformations.
• Glutamate transport by SLC1 proteins is essential for terminating excitatory neurotransmission and preventing excitotoxicity.
• Dysregulation of acidic amino acid transport is linked to neurological disorders such as epilepsy, amyotrophic lateral sclerosis and ischemic brain injury.
• CRISPR knockout, point-mutation and knock-in models are powerful tools for dissecting the physiological roles of these transporters.
Description
Acidic amino acid transmembrane transporter activity (GO:0015172) is a molecular function that enables the transfer of acidic amino acids, primarily L-glutamate and L-aspartate, from one side of a membrane to the other. These amino acids carry a negative charge at physiological pH, and their transport is critical for numerous cellular processes, including neurotransmission, metabolism and nitrogen balance. The SLC1 family of glutamate transporters represents the best-characterized group of proteins exhibiting this activity in mammals. Understanding GO:0015172 is therefore essential for researchers studying synaptic physiology, amino acid homeostasis and related pathologies. The transport mechanism relies on conformational changes that alternately expose substrate-binding sites to opposite sides of the membrane, a paradigm known as the alternating access model. This article synthesizes authoritative QuickGO annotation and published literature to provide a comprehensive overview of the genes, mechanisms and research methods associated with this GO term.
acidic amino acid transmembrane transporter activity At A Glance
| GO ID | GO:0015172 |
|---|---|
| GO term | acidic amino acid transmembrane transporter activity |
| Ontology | molecular_function |
| Synonym | acidic amino acid transporter activity |
| Definition | Enables the transfer of acidic amino acids from one side of a membrane to the other. Acidic amino acids have side chains with a negative charge at pH 7.3. |
| Major function | Transport of L-glutamate and L-aspartate across cellular membranes |
| Representative protein family | SLC1 (solute carrier family 1), including EAATs and ASCTs |
| Transport mechanism | Secondary active transport, typically sodium-dependent |
| Cellular locations | Plasma membrane, synaptic vesicles, mitochondrial membranes |
What Is GO:0015172?
In simple terms, GO:0015172 describes the ability of a protein to move acidic amino acids across a cell membrane. According to the Gene Ontology, this activity enables the transfer of acidic amino acids, which have side chains with a negative charge at pH 7.3, from one side of a membrane to the other. This function is typically mediated by integral membrane transport proteins that undergo conformational changes to shuttle substrates across the lipid bilayer.
Why Is acidic amino acid transmembrane transporter activity Important in Cell Biology?
Acidic amino acid transporters are fundamental to brain function and systemic metabolism. By clearing glutamate from the synaptic cleft, they terminate excitatory signaling and prevent neurotoxicity. In peripheral tissues, they contribute to amino acid absorption and nitrogen disposal. Consequently, mutations or dysregulation of these transporters are implicated in a range of human diseases, from epilepsy to neurodegeneration.
• Terminates glutamatergic neurotransmission and prevents excitotoxicity.
• Maintains metabolic homeostasis of aspartate and glutamate.
• Supports synaptic plasticity and cognitive functions.
• Mutations in SLC1A2 and SLC1A3 are associated with epilepsy and episodic ataxia.
• Dysfunction contributes to amyotrophic lateral sclerosis and ischemic stroke.
• Provides targets for neuroprotective drug development.
• Plays a role in cancer cell metabolism and redox balance.
• Essential for renal and intestinal amino acid reabsorption.
What Happens During acidic amino acid transmembrane transporter activity?
Substrate recognition and binding
In simple terms: The transporter first grabs the acidic amino acid from one side of the membrane.
The transport cycle begins when an acidic amino acid, such as L-glutamate or L-aspartate, binds to the transporter's substrate-binding site, which is exposed to the extracellular or cytoplasmic side depending on the conformational state. This binding is highly specific and involves interactions with conserved residues that recognize the negatively charged side chain.
Conformational transition
In simple terms: The protein changes shape to carry the amino acid across the membrane.
Upon substrate binding, the transporter undergoes a series of conformational changes that alternately expose the binding site to opposite sides of the membrane, a process known as the alternating access mechanism. In SLC1 transporters, this involves movements of the transport domain relative to the scaffold domain.
Sodium and potassium coupling
In simple terms: Sodium ions help drive the transport, and potassium is often exchanged.
Most SLC1 glutamate transporters utilize the electrochemical gradient of sodium and potassium to drive substrate translocation. The stoichiometry typically involves the co-transport of three sodium ions and one proton, with the counter-transport of one potassium ion, ensuring directional transport.
Substrate release and reset
In simple terms: The amino acid is released on the other side, and the transporter resets.
After the substrate is released into the cytoplasm or extracellular space, the transporter returns to its original conformation, ready for another cycle. This reset step is often rate-limiting and can be regulated by intracellular factors.
Key Genes Involved in GO:0015172 acidic amino acid transmembrane transporter activity
The following genes encode proteins that exhibit acidic amino acid transmembrane transporter activity, primarily from the SLC1 family.
| Gene | Major Role | Research Relevance |
|---|---|---|
| SLC1A1 | Neuronal glutamate transporter EAAT3 | Epilepsy, OCD, ischemic injury |
| SLC1A2 | Glial glutamate transporter GLT-1/EAAT2 | ALS, epilepsy, Alzheimer's disease |
| SLC1A3 | Glial glutamate transporter GLAST/EAAT1 | Episodic ataxia, migraine |
| SLC1A4 | Neutral amino acid transporter ASCT1 | Neurological disorders, serine metabolism |
| SLC1A5 | Neutral amino acid transporter ASCT2 | Cancer metabolism, glutamine transport |
| SLC1A6 | Neuronal glutamate transporter EAAT4 | Cerebellar function, ataxia |
| SLC1A7 | Retinal glutamate transporter EAAT5 | Vision, retinal signaling |
| SLC25A12 | Mitochondrial aspartate/glutamate carrier | Energy metabolism, autism |
| SLC25A13 | Mitochondrial aspartate/glutamate carrier | Citrin deficiency, urea cycle |
| GOT1 | Cytosolic aspartate aminotransferase | Malate-aspartate shuttle |
| GOT2 | Mitochondrial aspartate aminotransferase | Malate-aspartate shuttle |
| ASNS | Asparagine synthetase | Aspartate utilization, cancer |
| GLUL | Glutamine synthetase | Glutamate homeostasis, brain |
| GLS | Glutaminase | Glutamate production, cancer |
| GRIN1 | NMDA receptor subunit | Glutamate signaling, synaptic plasticity |
| GRIN2A | NMDA receptor subunit | Epilepsy, schizophrenia |
| GRIN2B | NMDA receptor subunit | Neurodevelopmental disorders |
How Is acidic amino acid transmembrane transporter activity Regulated?
The activity of acidic amino acid transporters is tightly regulated at multiple levels. Transcriptional regulation controls the abundance of transporters in response to neuronal activity and stress. Post-translational modifications, such as phosphorylation and ubiquitination, modulate their trafficking and stability. Additionally, the transport cycle itself can be regulated by intracellular signaling pathways, including those involving mTOR and the integrated stress response, which sense amino acid availability.
acidic amino acid transmembrane transporter activity and Human Disease
| Gene | Disease / Biology | Potential Experimental Model |
|---|---|---|
| SLC1A2 | ALS, epilepsy | Knockout mouse, point-mutation knock-in |
| SLC1A3 | Episodic ataxia | Conditional knockout, overexpression |
| SLC1A5 | Cancer proliferation | CRISPR knockout in cancer cell lines |
| SLC25A13 | Citrin deficiency | Patient-derived iPSCs, knock-in mice |
| GRIN2A | Epilepsy, schizophrenia | Point-mutation knock-in mice |
Neurodegenerative disorders
Dysfunctional glutamate transport leads to excitotoxicity, a hallmark of neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS) and Alzheimer's disease. Reduced expression or function of SLC1A2 (EAAT2) has been observed in ALS patients and models.
Epilepsy and seizure disorders
Mutations in SLC1A2 and SLC1A3 are associated with various forms of epilepsy, highlighting the critical role of glutamate clearance in preventing hyperexcitability.
Cancer metabolism
Acidic amino acid transporters, particularly SLC1A5 (ASCT2), are upregulated in many cancers to support increased glutamine and aspartate demand for biosynthetic pathways.
From acidic amino acid transmembrane transporter activity-Related Genes to Experimental Models
| Research Question | Suitable Model |
|---|---|
| Does loss of SLC1A2 cause excitotoxicity? | SLC1A2 knockout mouse or cell line |
| How does a patient mutation affect transport? | Point-mutation knock-in via CRISPR |
| Can overexpression rescue a disease phenotype? | Transgenic overexpression or viral delivery |
| What is the subcellular localization of the transporter? | Tagged knock-in (e.g., GFP) for imaging |
| Which genes regulate transporter expression? | CRISPR library screening with reporter |
| Does the transporter interact with other proteins? | Proximity labeling or co-IP with tagged knock-in |
How to Study the acidic amino acid transmembrane transporter activity Process
| Method | What It Measures | Typical Application |
|---|---|---|
| Radiolabeled uptake | Transport rate and affinity | Kinetic characterization of transporters |
| Patch-clamp | Transport currents | Electrogenic transport properties |
| Fluorescent sensors | Real-time substrate concentration | Synaptic glutamate dynamics |
| Cryo-EM | 3D structure of transporter | Mechanistic studies of conformational changes |
| Site-directed mutagenesis | Role of specific residues | Identification of key binding sites |
| CRISPR knockout | Loss-of-function phenotype | Determining physiological roles |
| RNA-seq | Transcriptional changes | Regulation of transporter expression |
Transport assays
Radiolabeled substrate uptake assays in cell lines or synaptosomes are used to measure the kinetic parameters of acidic amino acid transporters. These assays can be performed under varying ionic conditions to determine sodium dependence.
Electrophysiology
Patch-clamp recordings from cells expressing transporters can detect transport currents and reveal the stoichiometry and voltage dependence of the transport cycle.
Fluorescence imaging
Genetically encoded fluorescent sensors for glutamate or aspartate allow real-time monitoring of transport activity in live cells and tissues.
Structural biology
Cryo-electron microscopy and X-ray crystallography provide high-resolution snapshots of transporters in different conformations, elucidating the structural basis of substrate recognition and translocation.
How CRISPR Can Be Used to Study GO:0015172 acidic amino acid transmembrane transporter activity
Knockout
CRISPR-Cas9 knockout of genes encoding acidic amino acid transporters, such as SLC1A2 or SLC1A3, can be used to study their contribution to glutamate clearance and neuronal survival. Knockout cell lines and animal models have revealed critical roles in preventing excitotoxicity.
Point Mutation
Introducing patient-associated point mutations into transporter genes via CRISPR base editing or homology-directed repair allows researchers to assess the functional impact of specific variants on transport activity and trafficking.
Knock-in
Knock-in of fluorescent tags or epitope tags into endogenous transporter loci enables real-time imaging and biochemical isolation of the transporter without overexpression artifacts.
Overexpression
CRISPR activation (CRISPRa) or viral overexpression of transporters can be used to test whether increased transport activity is protective in disease models, such as ischemia or neurodegeneration.
How EDITGENE Supports acidic amino acid transmembrane transporter activity Research
Researchers studying acidic amino acid transmembrane transporter activity-related genes often need to determine whether a candidate gene is causally involved in a specific physiological or pathological process. EDITGENE provides a comprehensive suite of CRISPR-based services to facilitate such investigations, from gene knockout to precise point mutations and knock-in models.
Contact EDITGENE today to design your custom CRISPR model for acidic amino acid transmembrane transporter activity research.
Frequently Asked Questions About acidic amino acid transmembrane transporter activity
What is acidic amino acid transmembrane transporter activity?
It is a molecular function (GO:0015172) that enables the movement of acidic amino acids like glutamate and aspartate across cell membranes.
What genes are involved in acidic amino acid transmembrane transporter activity?
Key genes include SLC1A1, SLC1A2, SLC1A3, SLC1A4, SLC1A5, SLC1A6, and SLC1A7, which encode various glutamate and neutral amino acid transporters.
What diseases are associated with acidic amino acid transporters?
Dysfunction is linked to epilepsy, amyotrophic lateral sclerosis, Alzheimer's disease, and cancer metabolism.
How is acidic amino acid transport regulated?
It is regulated transcriptionally, post-translationally, and by signaling pathways such as mTOR and the integrated stress response.
What is the mechanism of acidic amino acid transport?
Transporters use an alternating access mechanism, often coupled to sodium and potassium gradients, to shuttle substrates across the membrane.
Which proteins exhibit acidic amino acid transmembrane transporter activity?
The SLC1 family of solute carriers, including EAATs and ASCTs, are the primary proteins with this activity.
How can I study acidic amino acid transporters in the lab?
Common methods include radiolabeled uptake assays, patch-clamp electrophysiology, fluorescent sensors, and structural biology techniques.
What are the roles of SLC1A2 and SLC1A3?
SLC1A2 (GLT-1) and SLC1A3 (GLAST) are glial glutamate transporters critical for clearing glutamate from synapses and preventing excitotoxicity.
Can CRISPR be used to study acidic amino acid transporters?
Yes, CRISPR knockout, point mutation, and knock-in models are widely used to dissect transporter function and disease mechanisms.
What is the clinical relevance of acidic amino acid transport?
It is relevant to neurological disorders, cancer, and metabolic diseases, making it a target for therapeutic development.
Conclusion
Acidic amino acid transmembrane transporter activity (GO:0015172) is a fundamental molecular function with critical roles in neurotransmission, metabolism, and disease. The SLC1 family of transporters exemplifies the structural and mechanistic principles underlying this activity. Continued research using advanced CRISPR models and biochemical assays will further illuminate how these transporters contribute to health and disease, potentially leading to new therapeutic strategies.
References
- 1. Grewer C et al.. 2014. SLC1 glutamate transporters.. Pflugers Arch 466(1):3-24 PMID: 24240778
- 2. Rajani V et al.. 2020. Tripartite signalling by NMDA receptors.. Mol Brain 13(1):23 PMID: 32070387
- 4. Schweikhard ES et al.. 2012. Amino acid secondary transporters: toward a common transport mechanism.. Curr Top Membr 70:1-28 PMID: 23177982
