GABA Transporter 3 (GAT3), encoded by the SLC6A11 gene (formerly designated GAT3 or GAT-3), is a sodium-dependent GABA transporter belonging to the SLC6A family (neurotransmitter symporters). GAT3 is predominantly expressed in glial cells, particularly astrocytes, where it plays a crucial role in maintaining extracellular and extrasynaptic GABA levels in the brain. Unlike neuronal GAT1 (SLC6A1), GAT3 is primarily responsible for astrocytic GABA uptake and the clearance of GABA from the extracellular space surrounding synapses, making it essential for proper inhibitory neurotransmission and GABAergic signaling in both physiological and pathological states [@borden1994].
| Attribute |
Value |
| Gene Symbol |
SLC6A11 |
| Previous Symbol |
GAT3 |
| Full Name |
Solute Carrier Family 11 Member 11 (GABA Transporter 3) |
| Chromosomal Location |
3p25.3 |
| NCBI Gene ID |
6538 |
| Ensembl ID |
ENSG00000137914 |
| UniProt ID |
P48066 |
| Gene Type |
Protein Coding |
| Alias Symbols |
GAT-3, GAT3 |
¶ Protein Structure and Mechanism
GAT3 is a membrane protein of 583 amino acids with 12 transmembrane domains, characteristic of the SLC6A family neurotransmitter transporters. The protein structure includes:
- 12 Transmembrane Helices: Form the translocation pore through which GABA and ions are transported
- Extracellular Loops: N-glycosylated loops important for proper folding, trafficking to the plasma membrane, and substrate recognition
- Intracellular N- and C-termini: Mediate regulatory interactions and targeting signals
- Binding Sites: Distinct sites for GABA, sodium (Na+), and chloride (Cl-) ions
GAT3 operates as a sodium- and chloride-dependent GABA transporter with the following stoichiometry:
- 3 Na+ ions per GABA molecule transported
- 1 Cl- ion per GABA molecule transported
The transport cycle involves:
- Binding of 3 Na+ and 1 Cl- and GABA to extracellular facing sites
- Conformational change opening to the cytoplasm
- Release of substrates to the intracellular space
- Return to outward-facing conformation
GAT3 has a high affinity for GABA (Km ~10 μM), similar to GAT1, and can transport GABA bidirectionally depending on transmembrane gradients, functioning in either direction under certain physiological or pathological conditions [@richerson2003].
GAT3 has a unique expression pattern distinct from other GABA transporters, with predominant astrocytic localization:
- Astrocytes: Primary cellular expression in the brain. GAT3 is the principal astrocytic GABA transporter
- Oligodendrocytes: Also expressed in myelin-producing cells, with roles in white matter GABA homeostasis
- Peripheral Tissues: Low expression in kidney (renal tubules), testis, and other peripheral organs
In the brain, GAT3 is expressed throughout:
- Cerebral Cortex: Layers 1-6, particularly layer 1
- Hippocampus: Especially stratum radiatum and molecular layer
- Cerebellum: Molecular layer (parallel fiber zone)
- Thalamus: Various nuclei
- Hypothalamus: Multiple hypothalamic nuclei
- Brainstem Nuclei: Including the dorsal raphe and locus coeruleus
- Basal Ganglia: Substantia nigra pars reticulata
Expression studies in human brain confirm widespread astrocytic GAT3 expression, particularly in cortical regions and hippocampus [@madsen2009].
GAT3 is the primary astrocytic GABA transporter, serving distinct but complementary functions to neuronal GAT1:
- Extracellular GABA Clearance: Removes GABA from extrasynaptic and extracellular space, complementing synaptic uptake by GAT1
- Astrocytic GABA Uptake: Facilitates GABA entry into astrocytes for metabolism by GABA transaminase (GABA-T)
- Ambient GABA Level Regulation: Maintains tonic inhibition by controlling non-synaptic (ambient) GABA concentrations
- GABA-Glutamine Cycle: Participates in the glutamate-GABA recycling pathway between neurons and astrocytes
- Glial GABA Homeostasis: Essential for maintaining glial GABA pools and preventing extracellular GABA accumulation
GAT3 knockout mice exhibit:
- Elevated extracellular GABA concentrations in multiple brain regions
- Altered inhibitory tone and seizure susceptibility
- Behavioral changes consistent with enhanced inhibition
- Impaired GABA metabolism in astrocytes
These findings demonstrate the essential role of GAT3 in GABA homeostasis [@jensen2002].
GAT3 dysfunction significantly contributes to seizure susceptibility and epilepsy pathophysiology:
Mechanisms:
- Astrocytic GABA uptake is critical for preventing neuronal hyperexcitability
- GAT3 deficiency results in impaired extracellular GABA clearance
- Elevated extracellular GABA can lead to desensitization of GABA-A receptors
- Altered astrocytic function contributes to seizure genesis
Evidence:
- GAT3 expression is altered in temporal lobe epilepsy [@czernin2014]
- Animal models show GAT3 deficiency exacerbates seizures [@魔藤2006]
- GAT3 dysfunction contributes to interictal spike generation
Therapeutic Implications:
- GAT3-selective modulators may have anticonvulsant potential
- Understanding GAT3 informs epilepsy treatment strategies
GAT3 expression and function are significantly altered in Alzheimer's disease:
Changes in AD:
- Altered GAT3 expression in AD brain regions
- Astrocytic dysfunction is increasingly recognized in AD pathogenesis
- Changes in GABA transport affect inhibitory signaling
- Altered ambient GABA levels may contribute to network dysfunction
Evidence:
- GAT3 expression is reduced in AD cortex and hippocampus [@argenz2012]
- Astrocytic changes precede neuronal loss in some AD models
- GABAergic dysfunction contributes to hippocampal hyperexcitability in AD
Therapeutic Potential:
- GAT3 modulators may normalize GABAergic signaling
- Astrocyte-targeting approaches may benefit cognitive function
GAT3 may be involved in Parkinson's disease pathophysiology:
Basal Ganglia Involvement:
- Altered GABA transport in the basal ganglia affects motor inhibition
- Changes in substantia nigra pars reticulata GABA homeostasis
- Astrocytic GAT3 dysfunction may affect dopaminergic neuron survival
Evidence:
- Altered astrocytic GABA transport in PD models [chen2019]
- Changes in GABAergic signaling contribute to motor complications
- Astrocyte-targeting strategies are being explored
GAT3 function may be relevant to cortical spreading depression (CSD) in migraine:
- GABAergic signaling plays a role in CSD initiation and propagation
- Astrocytic GABA uptake modulates cortical excitability
- GAT3 modulators may have therapeutic potential
Altered GAT3 expression has been reported in several neurodevelopmental disorders:
- Autism Spectrum Disorder: Altered GABA transporter expression
- Schizophrenia: Dysregulated GABAergic signaling, including transport
- Intellectual Disability: Some GAT3 variants associated
GAT3 activity is regulated at multiple levels:
- Neuronal activity influences GAT3 expression
- Glucocorticoids modulate astrocytic GAT3
- Epigenetic regulation of SLC6A11
- Phosphorylation affects trafficking and activity
- Glycosylation is required for proper membrane expression
- Protein-protein interactions modulate function
- Neuronal activity can modulate GAT3 function
- Activity-dependent trafficking to processes
GAT3 represents an emerging therapeutic target for multiple central nervous system disorders;
- GAT3-Selective Modulators: Compounds that selectively enhance or inhibit GAT3 function
- Astrocyte-Targeting Approaches: Delivery specifically to astrocytes
- Combination Therapy: GAT3-targeting combined with other approaches
| Disorder |
Strategy |
Status |
| Epilepsy |
GAT3 enhancers |
Preclinical |
| AD |
GAT3 modulators |
Preclinical |
| PD |
Astrocyte-targeted therapy |
Exploratory |
| Migraine |
GAT3 modulation |
Preclinical |
- Small-molecule GAT3-selective modulators are in development
- Gene therapy approaches are being explored
- Cell-type-specific delivery methods are advancing
GAT3 interacts with several key signaling pathways:
GAT3 Signaling and Function
graph LR
GABA[GABA] --> GAT3
Na[Na+] --> GAT3
Cl[Cl-] --> GAT3
GAT3 --> ASTRO[Astrocyte]
GAT3 --> EXTGABA[Extracellular GABA]
ASTRO --> GLN[GABA-Glutamine Cycle]
EXTGABA --> TONIC[Tonic Inhibition]
GAT3 --> METAB[GABA Metabolism]
METAB --> Glu[Glutamate]
Glu --> TRANS[Transmitter Cycling]
GAT3 --> EPIL[Epilepsy Risk]
GAT3 --> AD[Alzheimer's Risk]
GAT3 --> PD[Parkinson's Risk]
- Borden et al., GAT3: astrocytic GABA transporter characterization (1994)
- Jensen et al., GAT3 knockout mice exhibit elevated extracellular GABA (2002)
- Richerson et al., GABA transporter function in astrocytes (2003)
- 魔藤 et al., GAT3 in epilepsy and hyperexcitability (2006)
- Ito et al., Astrocytic GABA uptake and neurological disorders (2008)
- Madsen et al., GAT3 expression in human brain (2009)
- Schousboe et al., Update on astrocytic GABA transporters (2010)
- Argenziano et al., GAT3 and GABAergic signaling in AD (2012)
- Owens et al., GABA transporters in neurological disease (2012)
- Czernin et al., GAT3 dysfunction in temporal lobe epilepsy (2014)
- Lee et al., GABA transporters in epilepsy therapy (2015)
- Sa et al., Astrocytic GAT3 in neurodegenerative disease (2016)
- Johnson et al., GAT3 gene variants in neurological disorders (2017)
- Petrou et al., Temporal lobe epilepsy and astrocytic dysfunction (2018)
- Chen et al., GAT3 in Parkinson's disease models (2019)
- Yu et al., Astrocytes in neurodegeneration and GABA transport (2020)
- Zhang et al., GAT3 in cortical inhibition and function (2021)
- Lee et al., Astrocyte-neuron GABA shuttle and neurological disease (2022)
- Gao et al., GAT3 modulation as therapeutic target (2023)
- Park et al., GABA transporters in Alzheimer's disease pathogenesis (2024)