GABBR1 (Gamma-Aminobutyric Acid Type B Receptor Subunit 1) encodes the GABA-B1 subunit of the metabotropic [GABA](/mechanisms/gabaergic-signaling-neurodegeneration) receptor. GABA-B receptors are the principal inhibitory G-protein coupled receptors in the central nervous system, mediating slow synaptic inhibition through activation of inwardly rectifying potassium channels and inhibition of voltage-gated calcium channels. The GABBR1 subunit contains the orthosteric ligand-binding domain that recognizes GABA and the drug [baclofen](/therapeutics/baclofen).
GABBR1 is obligately heterodimerized with [GABBR2](/genes/gabbr2) to form functional GABA-B receptors. The GABBR1 subunit contributes the ligand-binding venus flytrap domain while GABBR2 provides the G-protein coupling interface. Dysfunction of GABAergic inhibitory signaling through GABA-B receptors has been implicated in multiple neurodegenerative conditions, including [Alzheimer's disease](/diseases/alzheimers-disease) and [Parkinson's disease](/diseases/parkinsons-disease).
The protein encoded by GABBR1 is [GABA-B Receptor Subunit 1](/proteins/gabbr1-protein). See the protein page for detailed structural and functional information.
Function
Normal Gene Function
GABBR1 encodes a 960-amino acid transmembrane protein that serves as the ligand-binding subunit of the heterodimeric GABA-B receptor complex. Key functions include:
Ligand recognition: The N-terminal venus flytrap domain (VFT) binds GABA and pharmacological agonists (baclofen) with high affinity
Receptor assembly: The coiled-coil domain at the C-terminus mediates obligate heterodimerization with [GABBR2](/genes/gabbr2)
Synaptic localization: Contains an ER retention signal (RSRR) that is masked upon GABBR2 binding, enabling surface trafficking
Alternative splicing: Produces two major isoforms — GABBR1a (with two sushi domains for axonal targeting) and GABBR1b (predominantly somatodendritic)
Signaling Pathways
GABA-B receptors couple to Gi/o proteins to mediate:
Presynaptic inhibition: Inhibition of P/Q-type and N-type [calcium channels](/mechanisms/calcium-homeostasis), reducing neurotransmitter release
MAPK modulation: Regulation of ERK1/2 signaling pathways relevant to neuronal survival
Disease Associations
Alzheimer's Disease
GABAergic dysfunction is increasingly recognized in [Alzheimer's disease](/diseases/alzheimers-disease):
GABBR1 expression is reduced in the hippocampus and temporal cortex of AD patients
Loss of GABA-B receptor-mediated inhibition contributes to neuronal hyperexcitability, a feature observed in early AD
Amyloid-beta oligomers disrupt GABA-B receptor trafficking and surface expression
GABA-B receptor activation has shown neuroprotective effects against [amyloid-beta](/proteins/amyloid-beta) toxicity in experimental models
[APOE4](/proteins/apoe) carriers show accelerated decline in GABAergic interneuron function
Parkinson's Disease
In [Parkinson's disease](/diseases/parkinsons-disease), GABA-B receptors play roles in basal ganglia circuitry:
Altered GABBR1 expression in the striatum and globus pallidus of PD patients
GABA-B receptors on striatopallidal [neurons](/entities/neurons) modulate indirect pathway activity
Baclofen (GABA-B agonist) affects motor function through basal ganglia circuits
[Alpha-synuclein](/proteins/alpha-synuclein) pathology affects GABAergic interneurons in the substantia nigra
Epilepsy
GABBR1 variants (S867G, A204T) are associated with temporal lobe epilepsy and generalized epilepsy syndromes
GABBR1 knockout mice exhibit spontaneous epileptiform activity and seizures
Absence epilepsy models show altered GABA-B receptor function in thalamocortical circuits
Expression
GABBR1 is broadly expressed throughout the central nervous system with highest levels in:
Hippocampus: CA1 and CA3 pyramidal neurons, dentate gyrus granule cells
Cerebral cortex: Layers II/III and V, particularly in GABAergic interneurons
Cerebellum: Purkinje cells and granule cells
Thalamus: Relay neurons and reticular nucleus
Basal ganglia: Medium spiny neurons of the striatum, globus pallidus
Substantia nigra: Pars reticulata GABAergic neurons
Expression data from the [Allen Brain Atlas](https://human.brain-map.org/) confirms widespread distribution with regional variation in isoform ratios (GABBR1a vs GABBR1b).
[Bettler et al., Molecular structure and physiological functions of GABA-B receptors (2004) (2004)](https://doi.org/10.1152/physrev.00036.2003)
[Unknown, Pin & Bettler, Organization and functions of mGlu and GABA-B receptor complexes (2016) (2016)](https://doi.org/10.1038/nature17174)
[Dinamarca et al., Complex formation of APP with GABA-B receptors links axonal trafficking to amyloidogenic processing (2019) (2019)](https://doi.org/10.1038/s41467-019-09498-2)
[Vigot et al., Differential compartmentalization and distinct functions of GABA-B receptor variants (2006) (2006)](https://doi.org/10.1016/j.neuron.2006.04.013)
[Schuler et al., Epilepsy, hyperalgesia, impaired memory, and loss of pre- and postsynaptic GABA-B responses in mice lacking GABA-B1 (2001) (2001)](https://doi.org/10.1016/S0896-6273(01)
[Calver et al., The C-terminal domains of the GABA-B receptor subunits mediate intracellular trafficking but are not required for receptor signaling (2001) (2001)](https://doi.org/10.1523/JNEUROSCI.21-04-01203.2001)
[Li et al., GABAergic interneuron dysfunction impairs hippocampal neurogenesis in adult apolipoprotein E4 knockin mice (2009) (2009)](https://doi.org/10.1016/j.stem.2009.10.015)