Beta-1 adrenergic receptor (ADRB1) and beta-2 adrenergic receptor (ADRB2) (ADRB1; ADRB2)

The beta-1 and beta-2 adrenergic receptors (ADRB1 and ADRB2) are G protein-coupled receptors (GPCRs) that mediate the physiological responses to the catecholamines epinephrine and norepinephrine (StatPearls, 2023). Beta-1 receptors are primarily expressed in cardiac tissue, where they regulate heart rate and contractility, while beta-2 receptors are predominantly found in the smooth muscle of the airways and blood vessels, mediating relaxation (UniProt P08588; UniProt P07550). These receptors are central to the fight-or-flight response and are major therapeutic targets in cardiovascular and respiratory medicine. Beta-blockers, such as metoprolol and propranolol, are used to treat hypertension and heart failure by reducing cardiac workload and protecting the heart from excessive sympathetic stimulation (NIH, 2023). Conversely, beta-2 agonists like albuterol and salmeterol are mainstay treatments for asthma and COPD, providing rapid or long-term relief of bronchoconstriction (PubMed, 2022). Understanding the subtype selectivity of drugs is crucial, as non-selective blockade can lead to adverse effects like bronchospasm in patients with reactive airway disease. Additionally, these receptors play roles in metabolic processes such as lipolysis and glycogenolysis, further expanding their physiological impact (PubChem, 2024). Overall, the ADRB1 and ADRB2 receptors represent a cornerstone of modern pharmacology with diverse clinical applications.

Other names

ADRB1ADRB2Beta-1 adrenoceptorBeta-2 adrenoceptorB1ARB2ARBeta-1 and beta-2 adrenoceptors

Beta-1 and beta-2 adrenergic receptors primarily signal through the Gs-alpha subunit, which activates adenylyl cyclase to increase intracellular cyclic adenosine monophosphate (cAMP) (PubChem, 2024). In cardiac myocytes (Beta-1), increased cAMP activates protein kinase A (PKA), which phosphorylates L-type calcium channels and phospholamban, increasing calcium-induced calcium release and contractility (StatPearls, 2023). In smooth muscle cells (Beta-2), PKA phosphorylates myosin light chain kinase (MLCK), decreasing its affinity for calcium-calmodulin and leading to muscle relaxation and bronchodilation (PubMed, 2021). Drugs targeting these receptors act as agonists to stimulate these pathways or as antagonists (beta-blockers) to competitively inhibit the binding of endogenous catecholamines.