Alpha-2B adrenergic receptor

Receptor

α2-adrenergic receptors include 3 highly homologous subtypes: α2A, α2B, and α2C. These receptors have a critical role in regulating neurotransmitter release from sympathetic nerves and from adrenergic neurons in the central nervous system.

Clinical significance

This gene encodes the α2B subtype, which was observed to associate with eIF-2B, a guanine nucleotide exchange protein that functions in regulation of translation. A polymorphic variant of the α2B subtype, which lacks 3 glutamic acids from a glutamic acid repeat element, was identified to have decreased G protein-coupled receptor kinase-mediated phosphorylation and desensitization; this polymorphic form is also associated with reduced basal metabolic rate in obese subjects and may therefore contribute to the pathogenesis of obesity. This gene contains no introns in either its coding or untranslated sequences.

A deletion variant of the α2B adrenergic receptor has been shown to be related to emotional memory in Europeans and Africans. This variant also predisposed people who had it to focus more on negative aspects of a situation.

• This predisposition remained present in people with the variant gene who took a single dose of the noradrenergic antidepressant reboxetine, but was weakened in people without the variant.

Evolution

The ADRA2B gene (sometimes referenced as A2AB) is used in animals as a nuclear DNA phylogenetic marker. This intronless gene has first been used to explore the phylogeny of the major groups of mammals, and contributed to reveal that placental orders are distributed into four major clades: Xenarthra, Afrotheria, Laurasiatheria, and Euarchontoglires. Comparative analysis of the primary protein sequence of ADRA2B across placentals also showed the high conservation of residues thought to be involved in agonist binding and in G protein–coupling. However, great variations are observed in the very long, third intracellular loop, with a polyglutamyl domain displaying pervasive length differences.

Ligands

Agonists

• (−)-Dibromophakellin

Antagonists

• ADRIANA – highly selective
• Imiloxan
• Yohimbine

References

References

1. (October 2018). ["OrthoMaM phylogenetic marker: ADRA2B coding sequence"](http://www.orthomam.univ-montp2.fr/orthomam/data/cds/detailMarkers/ENSG00000222040_ADRA2B.xml }}{{Dead link).
2. "Entrez Gene: ADRA2B adrenergic, alpha-2B-, receptor".
3. (Sep 2007). "A deletion variant of the alpha2b-adrenoceptor is related to emotional memory in Europeans and Africans". Nature Neuroscience.
4. (Feb 2001). "Parallel adaptive radiations in two major clades of placental mammals". Nature.
5. (Dec 2002). "Molecular evolution of the mammalian alpha 2B adrenergic receptor". Molecular Biology and Evolution.
6. (Mar 2009). "(-)-Dibromophakellin: an alpha2B adrenoceptor agonist isolated from the Australian marine sponge, Acanthella costata". Bioorganic & Medicinal Chemistry.