Alpha 2B adrenoceptor (IPR000207)
Short name: ADRA2B_rcpt
Overlapping homologous superfamilies
The adrenoceptors (or adrenergic receptors) are rhodopsin-like G protein-coupled receptors that are targets of the catecholamines, especially norepinephrine (noradrenaline) and epinephrine (adrenaline). Many cells possess these receptors, and the binding of a catecholamine to the receptor will generally stimulate the sympathetic nervous system, effect blood pressure, myocardial contractile rate and force, airway reactivity, and a variety of metabolic and central nervous system functions. The clinical uses of adrenergic compounds are vast. Agonists and antagonists interacting with adrenoceptors have proved useful in the treatment of a variety of diseases, including hypertension, angina pectoris, congestive heart failure, asthma, depression, benign prostatic hypertrophy, and glaucoma. These drugs are also useful in several other therapeutic situations including shock, premature labour and opioid withdrawal, and as adjuncts to general anaesthetics.
There are three classes of adrenoceptors, based on their sequence similarity, receptor pharmacology and signalling mechanisms [PMID: 18882199]. These three classes are alpha 1 (a Gq coupled receptor), alpha 2 (a Gi coupled receptor) and beta (a Gs coupled receptor), and each can be further divided into subtypes [PMID: 2855960]. The different subtypes can coexist in some tissues, but one subtype normally predominates.
There are three subtpyes of alpha 2 adrenoceptors (2A-C). The receptors are usually found presynaptically, where they inhibit the release of noradrenaline, and thus serve as an important receptor in the negative feedback control of noradrenaline release [PMID: 15684247, PMID: 9605427, PMID: 9760042, PMID: 9824686]. Postsynaptic alpha 2 receptors are located on liver cells, platelets, and the smooth muscle of blood vessels. Activation of the receptors causes platelet aggregation [PMID: 2574568], blood vessel constriction [PMID: 2887122, PMID: 9280371] and constriction of vascular smooth muscle [PMID: 8670422]. Agonists of alpha 2 adrenergic receptors are frequently used in veterinary anaesthesia, where they affect sedation, muscle relaxation and analgesia through their effects on the CNS [PMID: 10215710]. Alpha 2 adrenoceptors are coupled through the Gi/Go mechanism, inhibiting adenylate cyclase activity and downregulating cAMP formation.
This entry represents the alpha 2B receptor. It is found in the kidney, brain, and spinal cord, along with the other alpha 2 subtypes. However, it is the only subtype to be found in the heart and liver. Peripheral tissues, predominantly express the alpha 2A and 2B subtypes, with little alpha 2C. This is in contrast to the CNS, where alpha 2A and 2C are predominantly expressed, with little alpha 2B [PMID: 7812219, PMID: 19912818].
GO:0004938 alpha2-adrenergic receptor activity
GO:0016021 integral component of membrane
- PR00559 (ADRENRGCA2BR)