Alpha 1A adrenoceptor (IPR001004)

Short name: ADRA1A_rcpt

Overlapping homologous superfamilies


Family relationships


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.

Alpha 1 adrenoceptors have the following subtypes: 1A, 1B and 1D. They are found in both the central and peripheral nervous system. In the CNS, they are found mostly postsynaptically and have an excitatory function. Peripherally, they are responsible for contraction and are situated on vascular and non-vascular smooth muscle [PMID: 2887122] and veins [PMID: 9280371]. In the liver, they cause hepatic glycogenolysis and potassium release. Alpha 1 adrenoceptors are coupled to Gq/11, which activates phospholipase C and produces inositol triphosphate (IP3), and diacylglycerol (DAG). These second messengers and cause release of calcium from intracellular stores in the sarcoplasmic reticulum and activation of protein kinase C, respectively. Alpha 1 adrenoceptors have been implicated in other signalling pathways, including arachadonic acid release.

This entry represents alpha 1A adrenoceptor (previously known as the alpha 1C adrenergic receptor). It has been detected in the human brain, with the highest levels being found in the olfactory system, hypothalamic nuclei and in regions of the brainstem and spinal cord related to motor function [PMID: 9285356]. The receptor also found in the liver, prostate and urethra and the human heart [PMID: 8114668, PMID: 9915474].

GO terms

Biological Process

GO:0007186 G protein-coupled receptor signaling pathway
GO:0055117 regulation of cardiac muscle contraction
GO:0006937 regulation of muscle contraction
GO:0019229 regulation of vasoconstriction

Molecular Function

GO:0004937 alpha1-adrenergic receptor activity

Cellular Component

GO:0016021 integral component of membrane

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.