Affinage

GABBR2

Gamma-aminobutyric acid type B receptor subunit 2 · UniProt O75899

Length
941 aa
Mass
105.8 kDa
Annotated
2026-06-09
36 papers in source corpus 15 papers cited in narrative 15 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 5/5 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

GABBR2 encodes the GB2 subunit of the GABA-B receptor, a Gi/o-coupled GPCR that mediates inhibitory neurotransmission: it heterodimerizes with GABBR1/GB1 to form the functional receptor, and only co-expression of both subunits confers robust activation of GIRK-type potassium channels (PMID:9872315). Within the heterodimer GB2 provides the G protein coupling and effector functions—heteromeric assembly is required for baclofen-mediated, pertussis toxin-sensitive inhibition of voltage-gated Ca2+ channel currents in neurons (PMID:10751439), and the receptor negatively couples to adenylyl cyclase in response to GABA, baclofen and 3-aminopropyl(methyl)phosphinic acid, an effect blocked by GABA-B antagonists (PMID:10328880). Loss of GABBR2 in mice produces spontaneous epileptiform activity, hyperalgesia, impaired memory, abnormal neuronal architecture and premature death, establishing its essential role in CNS function (PMID:41397015). De novo GABBR2 missense variants cause neurodevelopmental disease spanning Rett-like syndrome and epileptic encephalopathy through a spectrum of functional consequences: loss of receptor activity, reduced agonist potency or surface expression, and gain-of-function constitutive activity (PMID:28856709, PMID:41803176); epileptic encephalopathy variants confer strong constitutive activity that, in a Gabbr2 knock-in mouse, drives adaptive downregulation of both receptor subunits and G protein signaling components, with positive allosteric modulators normalizing network activity (PMID:40994051). Beyond the nervous system, GABBR2 acts through PKA- and cAMP-dependent signaling in diverse contexts—central sensitization in chronic migraine via a GABBR2/PKA/SynCAM1 pathway (PMID:32931071), glycolysis-dependent post-ischemic angiogenesis (PMID:34422926), androgen receptor-driven cisplatin resistance in bladder cancer (PMID:37762034), and GnRH neuron apoptosis (PMID:41571204).

Mechanistic history

Synthesis pass · year-by-year structured walk · 8 steps
  1. 1998 High

    Established that GB2 is not an independent receptor but an obligate heterodimerization partner of GB1, resolving how the functional GABA-B receptor is assembled.

    Evidence Heterologous co-expression with GIRK channel electrophysiology and reciprocal immunoprecipitation

    PMID:9872315

    Open questions at the time
    • Stoichiometry and structural basis of the heterodimer not resolved
    • Did not assign which subunit performs G protein coupling versus ligand binding
  2. 1999 Medium

    Tested whether GB2 alone can signal, finding it could reach the surface and negatively couple to adenylyl cyclase—an observation that conflicts with the later consensus of obligate heterodimerization.

    Evidence Homomeric expression in COS/CHO cells with adenylyl cyclase assay and pharmacological antagonism

    PMID:10328880

    Open questions at the time
    • Contradicts later consensus that homomeric GABBR2 is non-functional
    • Possible endogenous GB1 contribution not excluded
  3. 2000 High

    Demonstrated in native neurons that heteromeric assembly is required for the receptor's inhibition of Ca2+ channel currents, linking the heterodimer to a physiological effector through Gi/o.

    Evidence Antisense knockdown of GABBR1 in sympathetic neurons with patch-clamp and pertussis toxin controls

    PMID:10751439

    Open questions at the time
    • Did not isolate the specific role of GB2 versus GB1 in the coupling
    • Specific Gi/o subtype not identified
  4. 2003 Medium

    Extended GABBR2 expression beyond brain, identifying a testis/sperm isoform with a truncated 3'UTR localized to the sperm acrosome, raising a non-neuronal role.

    Evidence RT-PCR, Northern/Western blot, RACE-PCR and immunofluorescence in rat testis and sperm

    PMID:14967916

    Open questions at the time
    • Functional role of acrosomal GABBR2 not established
    • No heterodimerization partner identified in sperm
  5. 2017 Medium

    Connected de novo GABBR2 variants to neurodevelopmental disease, showing EE-associated variants reduce receptor function more severely than RTT-like variants and respond to agonist rescue.

    Evidence Whole-exome sequencing with cell culture functional assays and Xenopus tropicalis in vivo agonist rescue

    PMID:28856709

    Open questions at the time
    • Did not capture gain-of-function/constitutive variants identified later
    • Mechanism linking reduced activity to phenotype severity not dissected
  6. 2026 High

    Resolved that disease variants act through gain-of-function constitutive activity, not only loss of function, and showed the network response involves compensatory receptor downregulation correctable by positive allosteric modulators.

    Evidence Luciferase reporter assays, CRISPR knock-in mouse, EEG and slice electrophysiology, proteomics and PAM pharmacology

    PMID:40994051 PMID:41803176

    Open questions at the time
    • Structural basis of constitutive activity not defined
    • Whether PAM correction translates to behavioral/clinical benefit not shown
  7. 2025 Medium

    Defined the consequences of total GABBR2 loss in vivo, confirming its essential role in neuronal survival, network excitability, nociception and memory.

    Evidence Conditional Cre-mediated knockout with EEG, behavioral, histological and immunohistochemical readouts

    PMID:41397015

    Open questions at the time
    • Cell-type-specific contributions to phenotypes not parsed
    • Molecular cause of neuronal death not identified
  8. 2026 Medium

    Implicated GABBR2 in non-neuronal disease contexts acting through canonical cAMP/PKA and metabolic effectors, broadening its functional scope beyond synaptic inhibition.

    Evidence In vivo and cell-model loss/gain-of-function across migraine PAG, ischemic angiogenesis, bladder cancer cisplatin resistance and GnRH neuron apoptosis

    PMID:32931071 PMID:34422926 PMID:37762034 PMID:41571204

    Open questions at the time
    • Whether GB1 heterodimerization is required in these peripheral contexts is unclear
    • Direct receptor-level mechanism not established in several systems

Open questions

Synthesis pass · forward-looking unresolved questions
  • How GABBR2 transcriptional regulation (AR, TAp73alpha/HDAC2/REST) and its reported modulation of APP processing integrate with its canonical heterodimeric signaling remains unresolved.
  • APP processing and Ca2+/ROS/apoptosis effects rest on single overexpression experiments without mechanistic dissection
  • Whether transcriptional control by AR or TAp73alpha operates in neurons is unknown

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0060089 molecular transducer activity 2 GO:0098772 molecular function regulator activity 2
Localization
GO:0005886 plasma membrane 1
Pathway
R-HSA-112316 Neuronal System 2 R-HSA-162582 Signal Transduction 2
Partners
GABBR1
Complex memberships
GABA-B receptor heterodimer (GB1/GB2)

Evidence

Reading pass · 15 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1998 GABBR2 (GABA(B)R2) forms a functional heterodimer with GABBR1 (GABA(B)R1); neither subunit alone activates GIRK-type potassium channels, but co-expression of both confers robust channel stimulation. Immunoprecipitation demonstrated physical association of the two polypeptides, likely as heterodimers. Heterologous co-expression in cells, GIRK channel electrophysiology, immunoprecipitation Nature High 9872315
1999 Human GABBR2, when expressed alone (without GABBR1) in CHO cells, localizes to the cell surface and negatively couples to adenylyl cyclase in response to GABA, baclofen, and 3-aminopropyl(methyl)phosphinic acid; this coupling is blocked by the antagonist 2-hydroxysaclofen. Heterologous expression in COS and CHO cells, adenylyl cyclase activity assay, pharmacological antagonism Molecular and cellular neurosciences Medium 10328880
2000 Heteromeric assembly of GABBR1 and GABBR2 is required for baclofen-mediated inhibition of Ca2+ channel currents in sympathetic neurons; knockdown of endogenous GABBR1 via antisense markedly reduced the inhibitory effect of baclofen, and the effect was pertussis toxin-sensitive and voltage-dependent. Nuclear microinjection of sense/antisense constructs into superior cervical ganglion neurons, patch-clamp recording, pertussis toxin treatment The Journal of neuroscience High 10751439
2017 De novo GABBR2 variants found in Rett-like and epileptic encephalopathy patients reduce receptor function; EE-associated variants cause a more profound reduction in receptor activity than RTT-like variants and show greater responsiveness to agonist rescue in a Xenopus tropicalis animal model. Whole-exome sequencing, cell culture functional assays, Xenopus tropicalis in vivo model, agonist rescue experiments Annals of neurology Medium 28856709
2020 GABBR2 mediates central sensitization in chronic migraine through a GABBR2/PKA/SynCAM1 signaling pathway in the periaqueductal gray; baclofen (GABABR agonist) and PKA inhibitor H89 alleviated hyperalgesia and reduced VGLUT2, glutamate, CGRP, and c-Fos, while antagonist CGP35348 and PKA agonist had opposing effects. Rat chronic migraine model, intraventricular injection of pharmacological agents, Western blot, ELISA, immunohistochemistry FASEB journal Medium 32931071
2021 GABBR2 regulates post-ischemic angiogenesis through the glycolysis pathway; GABBR2 knockdown in HUVECs suppressed hypoxia-induced proliferation, migration, and tube formation, and reduced expression of glycolytic enzymes HKII, PFKFB3, and PKM1; GABBR2 downregulation in mice reduced blood flow recovery after hindlimb ischemia. Lentiviral knockdown in HUVECs, tube formation/migration/proliferation assays, XF analyzer metabolic assay, hindlimb ischemia mouse model, adenoviral overexpression, Western blot Frontiers in cardiovascular medicine Medium 34422926
2023 Androgen receptor (AR) directly binds the GABBR2 promoter and drives its transcription; AR knockdown reduces GABBR2 expression, dihydrotestosterone treatment induces it, and antiandrogen hydroxyflutamide partially reverses induction. GABBR2 upregulation in cisplatin-resistant bladder cancer cells contributes to resistance, and GABBR2 knockdown or pharmacological antagonism (CGP46381) sensitizes AR-positive cells to cisplatin. Chromatin immunoprecipitation (ChIP), AR knockdown/DHT treatment, GABBR2 knockdown, GABABR antagonist treatment, cisplatin cytotoxicity assay International journal of molecular sciences Medium 37762034
2003 GABBR2 protein is expressed in rat testis and sperm with a shorter transcript than in brain (3.0 kb vs. 5.6 kb due to truncated 3'UTR); in sperm, GABBR2 protein is localized to the acrosome region of the sperm head. RT-PCR, Northern blot, Western blot, RACE-PCR, indirect immunofluorescence The Journal of reproduction and development Medium 14967916
2026 Disease-associated GABBR2 missense variants (p.A567T, p.S695I, p.I705N) associated with epileptic encephalopathy display strong constitutive activity (50-100% of maximal GABA-induced wild-type activity) as individual subunits or heterodimers. In Gabbr2I704N/+ knock-in mice, constitutive activity increases at both pre- and postsynaptic GBRs, but receptor responsiveness to agonists is reduced; adaptive downregulation of both GB1 and GB2 subunits and G protein signaling components occurs. Positive allosteric modulator treatment normalized network activity in these mice. Luciferase reporter assay in heterologous cells, CRISPR knock-in mouse, in vitro and in vivo electrophysiology (EEG, brain slice), proteomics, positive allosteric modulator pharmacology Brain High 40994051
2026 De novo missense variants in GABBR2 produce a range of gain- and loss-of-function alterations: (i) increased constitutive activity with decreased GABA efficacy, (ii) reduced GABA potency, or (iii) reduced surface expression with decreased GABA efficacy, as characterized by in vitro functional assays. In vitro functional characterization of variants in heterologous cells (luciferase reporter assay, surface expression assay) NPJ genomic medicine Medium 41803176
2025 TAp73α binds directly to HDAC2 and disassembles the HDAC2/REST repressor complex, thereby derepressing neuronal GABBR2 expression in melanoma cells; TAp73α-induced GABBR2 upregulation promotes EMT marker upregulation, cancer cell invasiveness and proliferation. Multi-omics (transcriptomics, proteomics, cistromics), 3D protein modeling, protein-protein interaction assays, functional invasion/proliferation assays Cancer letters Medium 40505831
2025 Global knockout of GABBR2 (via Cre-mediated conditional disruption of a floxed Gabbr2 allele) recapitulates the germline GABBR2 knockout phenotype, including spontaneous epileptiform activity, hyperlocomotor activity, hyperalgesia, impaired memory, abnormal neuronal architecture, increased neuronal cell death, and premature death. CRISPR loxP insertion, Cre-mediated conditional knockout (Actin-Cre), EEG, behavioral assays, histology, immunohistochemistry PloS one Medium 41397015
2026 Carbamazepine upregulates GABBR2 protein expression and activates it to suppress the AC/cAMP/PKA signaling pathway, triggering apoptosis of hypothalamic GnRH neurons; GABBR2 knockdown in GT1-7 cells attenuates CBZ-induced AC/cAMP/PKA inhibition, reduces apoptosis, and partially restores GnRH secretion. In vivo rat model (long-term CBZ dosing), GT1-7 cell line GABBR2 knockdown, Western blot, ELISA, cAMP/PKA pathway assays Biochemical pharmacology Medium 41571204
2024 GABBR2 overexpression in human neuroblastoma cells (SH-SY5Y, BE(2)-M17) increases intracellular Ca2+ concentration, reactive oxygen species production, mitochondrial permeability transition pore opening, and apoptosis. Expression plasmid transfection, intracellular Ca2+ measurement, ROS assay, mitochondrial permeability assay, apoptosis assay Biochemical genetics Low 39724481
2025 GABBR2 overexpression in N2a/APP cells increased ADAM10 expression and decreased BACE1 expression, leading to upregulation of sAPPα and downregulation of sAPPβ, suggesting GABBR2 modulates APP processing toward the non-amyloidogenic pathway. Expression plasmid transfection in N2a/APP cells, Western blot for ADAM10, BACE1, sAPPα, sAPPβ Biochemistry and biophysics reports Low 40927314

Source papers

Stage 0 corpus · 36 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
1998 GABA(B) receptors function as a heteromeric assembly of the subunits GABA(B)R1 and GABA(B)R2. Nature 856 9872315
2002 Expression and distribution of metabotropic GABA receptor subtypes GABABR1 and GABABR2 during rat neocortical development. The European journal of neuroscience 96 12081656
1999 Molecular identification of the human GABABR2: cell surface expression and coupling to adenylyl cyclase in the absence of GABABR1. Molecular and cellular neurosciences 94 10328880
2000 Heteromeric assembly of GABA(B)R1 and GABA(B)R2 receptor subunits inhibits Ca(2+) current in sympathetic neurons. The Journal of neuroscience : the official journal of the Society for Neuroscience 90 10751439
2017 GABBR2 mutations determine phenotype in rett syndrome and epileptic encephalopathy. Annals of neurology 71 28856709
2004 Comparative cellular distribution of GABAA and GABAB receptors in the human basal ganglia: immunohistochemical colocalization of the alpha 1 subunit of the GABAA receptor, and the GABABR1 and GABABR2 receptor subunits. The Journal of comparative neurology 69 14961561
2001 Differential expression of GABA(B)R1 and GABA(B)R2 receptor immunoreactivity in neurochemically identified neurons of the rat neostriatum. The Journal of comparative neurology 38 11304711
2001 Human GABA(B)R genomic structure: evidence for splice variants in GABA(B)R1 but not GABA(B)R2. Gene 38 11707323
2009 Association and interaction analyses of GABBR1 and GABBR2 with nicotine dependence in European- and African-American populations. PloS one 34 19763258
2003 Identification of GABABR2 in rat testis and sperm. The Journal of reproduction and development 17 14967916
2017 Genome-wide DNA Methylation Analysis Reveals GABBR2 as a Novel Epigenetic Target for EGFR 19 Deletion Lung Adenocarcinoma with Induction Erlotinib Treatment. Clinical cancer research : an official journal of the American Association for Cancer Research 16 28490462
2006 Regulation by nicotine of Gpr51 and Ntrk2 expression in various rat brain regions. Neuropsychopharmacology : official publication of the American College of Neuropsychopharmacology 16 16794563
2020 Deficiency in the function of inhibitory interneurons contributes to glutamate-associated central sensitization through GABABR2-SynCAM1 signaling in chronic migraine rats. FASEB journal : official publication of the Federation of American Societies for Experimental Biology 15 32931071
2011 The level and distribution of the GABA(B)R2 receptor subunit in the rat's central auditory system. Neuroscience 15 21371537
2006 GABA(B) receptors in the centromedian/parafascicular thalamic nuclear complex: an ultrastructural analysis of GABA(B)R1 and GABA(B)R2 in the monkey thalamus. The Journal of comparative neurology 15 16538684
2012 The level and distribution of the GABA(B)R1 and GABA(B)R2 receptor subunits in the rat's inferior colliculus. Frontiers in neural circuits 14 23189044
2023 Paeonol ameliorates hippocampal neuronal damage by inhibiting GRM5/GABBR2/β-arrestin2 and activating the cAMP-PKA signaling pathway in premenstrual irritability rats. Brain research bulletin 12 38036272
2021 Endothelial GABBR2 Regulates Post-ischemic Angiogenesis by Inhibiting the Glycolysis Pathway. Frontiers in cardiovascular medicine 11 34422926
2020 MicroRNA-330 Directs Downregulation of the GABABR2 in the Pathogenesis of Pancreatic Cancer Pain. Journal of molecular neuroscience : MN 11 32621101
2023 GABBR2 as a Downstream Effector of the Androgen Receptor Induces Cisplatin Resistance in Bladder Cancer. International journal of molecular sciences 10 37762034
2022 miR-31-3p functions as a tumor suppressor by directly targeting GABBR2 in prostate cancer. Frontiers in oncology 10 36059697
2024 Paeonol and glycyrrhizic acid in combination ameliorate the recurrent nitroglycerin-induced migraine-like phenotype in rats by regulating the GABBR2/TRPM8/PRKACA/TRPV1 pathway. Journal of ethnopharmacology 9 38908492
2001 Subpopulations of neurons in rat substantia nigra display GABA(B)R2 receptor immunoreactivity. Brain research 9 11716827
2016 A GABBR2 gene variant modifies pathophysiology in Huntington's disease. Neuroscience letters 7 27033668
2022 Paroxysmal limb dystonias associated with GABBR2 pathogenic variant: A case-based literature review. Brain & development 5 35414446
2021 Lactiplantibacillus plantarum HG20 attenuates II type collagen-induced rheumatoid arthritis in rats via anti-inflammatory and inhibition of apoptosis. Journal of applied microbiology 5 34689406
2023 HSV-1 latency-associated transcript miR-H3 and miR-H4 target STXBP1 and GABBR2 genes. Journal of neurovirology 3 37668872
2025 TAp73α drives cancer metastasis via PPI-mediated derepression of the neuronal HDAC2/REST-GABBR2 axis. Cancer letters 2 40505831
2024 Increased GABBR2 Expression on Cell Membranes Causes Increased Ca2 + Inward Flow, Associated with Cognitive Impairment in Early Alzheimer's Disease. Biochemical genetics 2 39724481
2026 Normalization of network activity in an epilepsy model with a constitutively active GABBR2 variant. Brain : a journal of neurology 1 40994051
2025 Identification of GABBR2 as a diagnostic marker and its association with Aβ in Alzheimer's disease. Biochemistry and biophysics reports 1 40927314
2024 Corrigendum: miR-31-3p functions as a tumor suppressor by directly targeting GABBR2 in prostate cancer. Frontiers in oncology 1 38562171
2022 Delayed Expression of Both GABABR1 and GABABR2 Subunits in Murine Hippocampal Dentate Gyrus After a Single Systemic Injection of Trimethyltin. Neurochemical research 1 35737203
2026 Carbamazepine disrupts the hypothalamic-pituitary-testicular axis and induces hormonal imbalances and sperm damage through activating GABBR2 to inhibit AC/cAMP/PKA pathway. Biochemical pharmacology 0 41571204
2026 Functional signatures of de novo GABBR1 and GABBR2 variants associated with neurodevelopmental disorders. NPJ genomic medicine 0 41803176
2025 Development of a floxed Gabbr2 gene allows for widespread conditional disruption of GABBR2 and recapitulates the phenotype of germline Gabbr2 knockout mice. PloS one 0 41397015

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