beta2adrenerga

Beta2adrenerga refers to the beta-2 adrenergic receptor (β2-AR), a G protein-coupled receptor that binds catecholamines such as epinephrine and norepinephrine. In humans, the receptor is encoded by the ADRB2 gene and is expressed in various tissues, with high levels in bronchial and vascular smooth muscle, as well as in the uterus, skeletal muscle, and certain immune and metabolic cells.

Function and signaling: upon activation, β2-AR couples to the stimulatory G protein (Gs), stimulating adenylyl cyclase and increasing intracellular cyclic AMP (cAMP). The rise in cAMP activates protein kinase A (PKA), leading to smooth muscle relaxation, notably bronchodilation in the airways, and effects on metabolism such as glycogenolysis and lipolysis. In addition to direct bronchodilation, β2-AR signaling can modulate vascular tone and inflammatory cell activity, contributing to the receptor’s role in physiological and pathological responses.

Pharmacology and clinical relevance: selective β2-adrenergic agonists, including salbutamol (albuterol), formoterol, and salmeterol, are widely used as bronchodilators in asthma and chronic obstructive pulmonary disease (COPD). Non-selective beta blockers can antagonize β2-AR activity, which may provoke bronchoconstriction in susceptible individuals. Adverse effects of β2-agonists can include tremor, tachycardia, and hypokalemia, particularly with systemic or high-dose use.

Genetics and variability: common polymorphisms in ADRB2, such as Arg16Gly and Gln27Glu, have been studied for associations with receptor downregulation and variable clinical responses to β2-agonists, though findings are mixed and context-dependent.