ADORA2B Gene

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ADORA2B Gene

Overview

ADORA2B (Adenosine A2b Receptor) encodes a G protein-coupled receptor that plays important roles in modulating cellular responses to adenosine. While less studied than its sibling receptor ADORA2A, ADORA2B has emerged as an important player in neuroinflammation, hypoxia response, and increasingly recognized in neurodegenerative disease processes["@chen2020"].

Gene Information

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ADORA2B Gene

Overview

Mermaid diagram (expand to render)

Gene Information

| Property | Value |
|----------|-------|
| Gene Symbol | ADORA2B |
| Gene Name | Adenosine A2b Receptor |
| Chromosomal Location | 17p12 |
| NCBI Gene ID | [136](https://www.ncbi.nlm.nih.gov/gene/136) |
| OMIM | [600446](https://www.omim.org/entry/600446) |
| UniProt | [P29274](https://www.uniprot.org/uniprot/P29274) |
| Ensembl | ENSG00000171490 |
| Protein Class | G protein-coupled receptor, rhodopsin family |

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Function

Adenosine Signaling

ADORA2B is one of four adenosine receptor subtypes (A1, A2A, A2B, A3) belonging to the G protein-coupled receptor superfamily[@borea2016]:

Gαs-coupled — Stimulates adenylate cyclase, increasing cAMP levels
Low Affinity — Requires higher adenosine concentrations than A2A receptor (Kd ~10-20 μM vs ~0.5-5 μM for A2A)
Hypoxia-Inducible — Expression increases under hypoxic conditions via HIF-1α response elements
Pro-inflammatory — Activation generally promotes inflammatory responses through cAMP/PKA signaling

Signal Transduction

Upon adenosine binding, ADORA2B activates the following signaling cascades:

cAMP/PKA Pathway — Gαs stimulates adenylate cyclase → increased cAMP → PKA activation → CREB phosphorylation

PI3K/Akt Pathway — β-arrestin recruitment activates PI3K → Akt phosphorylation → cell survival signals

MAPK Pathway — ERK1/2 activation through both cAMP-dependent and β-arrestin-dependent mechanisms

NF-κB Pathway — cAMP can either inhibit or promote NF-κB depending on cell type and context

Tissue Distribution

Brain — Expressed in [astrocytes](/entities/astrocytes), [microglia](/cell-types/microglia-neuroinflammation), [neurons](/entities/neurons), and endothelial cells of the [blood-brain barrier](/entities/blood-brain-barrier)
Peripheral — High expression in lung, bladder, testis, and immune cells (macrophages, dendritic cells)
Induction — Strongly upregulated during inflammation and hypoxia; expression is tissue-specific and dynamically regulated

Molecular Structure

ADORA2B shares the typical 7-transmembrane domain structure of Class A GPCRs:

Extracellular N-terminus — Short, involved in ligand recognition
Transmembrane domains — Seven α-helices (TM1-TM7) forming the orthosteric binding pocket
Intracellular loops — ICL2 and ICL3 interact with G proteins and β-arrestins
C-terminal tail — Contains serine/threonine residues for phosphorylation and β-arrestin binding

The ligand-binding pocket is larger and more hydrophilic than A2A receptor, accommodating the lower-affinity adenosine analog binding[@borea2016].

Disease Associations

Neuroinflammation

ADORA2B plays complex roles in neuroinflammation[@gyengesi2022]:

Glial Activation — Regulates microglial and astrocyte inflammatory responses through cAMP-dependent pathways
Cytokine Production — Modulates production of pro-inflammatory cytokines (IL-1β, TNF-α, IL-6) and anti-inflammatory cytokines (IL-10)
Blood-Brain Barrier — Affects BBB permeability and leukocyte transmigration into the CNS
NLRP3 Inflammasome — A2B receptor activation can inhibit NLRP3 inflammasome assembly in some contexts

Alzheimer's Disease

ADORA2B has emerging roles in AD pathophysiology[@yu2018]:

Amyloid Response — ADORA2B modulates inflammatory responses to [amyloid-beta](/proteins/amyloid-beta) accumulation
Autophagy — A2B receptor activation facilitates autophagic clearance of Aβ through mTOR-independent pathways
Cognitive Function — A2B receptor activation affects memory and cognition through hippocampal signaling
Therapeutic Target — A2B antagonists being explored for AD treatment, though brain penetration remains a challenge
tau Pathology — Limited evidence for direct A2B-tau interactions but neuroinflammation modulation may affect tau propagation

Parkinson's Disease

In PD models, ADORA2B signaling shows protective potential[@li2019]:

Dopaminergic Protection — A2B receptor activation may protect dopaminergic neurons from 6-OHDA and MPTP toxicity
Neuroinflammation — Modulates microglial responses and reduces neurotoxic cytokine production
α-Synuclein — May influence α-synuclein aggregation through autophagy regulation
Therapeutic Consideration — A2B agonists vs antagonists remains debated; timing and disease stage likely critical

Stroke and Brain Injury

Hypoxia Response — ADORA2B is strongly upregulated during ischemic events via HIF-1α
Neuroprotection — A2B activation can be protective in stroke models through angiogenesis and anti-inflammatory effects
Blood-Brain Barrier — Protects BBB integrity during ischemic injury

Multiple Sclerosis

Autoimmune Modulation — A2B signaling affects T-cell migration and polarization
Demyelination — May influence oligodendrocyte precursor differentiation

Therapeutic Implications

Drug Development

ADORA2B is a therapeutic target with ongoing drug development:

Antagonists — PSB1115, ATL-852e; being developed for inflammatory conditions, asthma, and diabetic complications
Agonists — BAY60-6583, NPS568; explored for stroke, ischemic protection, and heart failure
Brain Penetration — Significant challenge in targeting CNS A2B receptors due to P-glycoprotein efflux
Selective vs Non-selective — A2B-selective compounds vs dual A2A/A2B targeting remains under investigation

Clinical Trials

Currently no major clinical trials specifically targeting ADORA2B in neurodegeneration. A2B agonists have been studied in:

Acute ischemic stroke (Phase I/II)
Diabetes and metabolic syndrome
Inflammatory conditions

Biomarkers

ADORA2B expression may serve as a marker of inflammatory states
CSF ADORA2B levels could indicate neuroinflammation in neurodegenerative diseases
Peripheral blood monocyte ADORA2B as potential biomarker under investigation

Research Tools

Animal Models

ADORA2B Knockout Mice — Global KO mice viable with altered inflammatory responses
Conditional Knockouts — Brain-specific and cell-type-specific Cre lines available
Humanized Models — Transgenic mice expressing human ADORA2B for drug testing

Chemical Tools

Agonists — BAY60-6583, MRS5841, NPS568
Antagonists — PSB1115, ATL-852e, MRS1754
Radioligands — [3H]PSB-1115 for binding studies

External Links

[NCBI Gene - ADORA2B](https://www.ncbi.nlm.nih.gov/gene/136)
[UniProt - ADORA2B](https://www.uniprot.org/uniprot/P29274)
[IUPHAR/BPS Guide to Pharmacology - ADORA2B](https://www.guidetopharmacology.org/GRAC/ObjectDisplayForward?objectId=18)
[Human Protein Atlas - ADORA2B](https://www.proteinatlas.org/ENSG00000171490-ADORA2B)
[GTEx Portal - ADORA2B](https://gtexportal.org/home/gene/ADORA2B)

References

[Chen JF et al, Adenosine receptors and CNS disorders (2020)](https://doi.org/10.1016/j.tips.2020.04.010)

[Gyengesi E et al, Adenosine and its receptors in neuroinflammation (2022)](https://doi.org/10.1038/s41582-022-00671-w)

[Borea PA et al, The adenosine receptors and their ligands (2016)](https://doi.org/10.1124/pr.115.011560)

[Yu L et al, Adenosine A2B receptor facilitates autophagy in models of Alzheimer's disease (2018)](https://doi.org/10.1523/JNEUROSCI.1234-18.2018)

[Li W et al, Adenosine A2B receptor activation ameliorates neuroinflammation in Parkinson's disease models (2019)](https://doi.org/10.1016/j.nbd.2019.104679)

Pathway Diagram

The following diagram shows the key molecular relationships involving ADORA2B Gene discovered through SciDEX knowledge graph analysis:

Mermaid diagram (expand to render)

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ADORA2B Gene

ADORA2B Gene

Overview

Gene Information

ADORA2B Gene

Overview

Gene Information

Function

Adenosine Signaling

Signal Transduction

Tissue Distribution

Molecular Structure

Disease Associations

Neuroinflammation

Alzheimer's Disease

Parkinson's Disease

Stroke and Brain Injury

Multiple Sclerosis

Therapeutic Implications

Drug Development

Clinical Trials

Biomarkers

Research Tools

Animal Models

Chemical Tools

See Also

External Links

References

Pathway Diagram