Muscarinic acetylcholine receptor M3 and Beta2-adrenoceptor (M3R/ADRB2)

The Muscarinic acetylcholine receptor M3 (CHRM3) and the Beta2-adrenoceptor (ADRB2) are two distinct G protein-coupled receptors (GPCRs) that serve as the primary regulatory nodes for airway smooth muscle tone. The M3 receptor is primarily coupled to the Gq signaling pathway, where its activation by acetylcholine leads to phospholipase C activation, calcium mobilization, and subsequent bronchoconstriction [UniProt P20309]. Conversely, the Beta2-adrenoceptor is coupled to the Gs pathway, which activates adenylyl cyclase to increase intracellular cAMP, leading to smooth muscle relaxation and bronchodilation [UniProt P07550]. In the context of respiratory pharmacology, these two receptors are targeted simultaneously using a combination of Long-Acting Muscarinic Antagonists (LAMAs) and Long-Acting Beta-Agonists (LABAs), or via single-molecule bifunctional compounds known as Muscarinic Antagonist-Beta2 Agonists (MABAs) like batefenterol [PubMed PMID: 25024339]. This dual-target approach provides superior clinical outcomes in Chronic Obstructive Pulmonary Disease (COPD) and asthma by inhibiting the parasympathetic constrictor drive while actively promoting sympathetic dilatory pathways [PubMed PMID: 30171515]. Clinically, drugs targeting this combination improve lung function, as measured by Forced Expiratory Volume in 1 second (FEV1), and reduce the frequency of disease exacerbations [StatPearls: COPD]. The synergy between M3 antagonism and Beta2 agonism allows for lower doses of individual components, potentially minimizing side effects while maximizing therapeutic efficacy.

Other names

Muscarinic M3 and Beta-2 adrenergic receptorsCHRM3 and ADRB2LAMA/LABA targetM3R/Beta2-AR

The mechanism involves a dual pharmacological approach: antagonism of the M3 muscarinic receptor to block the Gq-mediated phospholipase C pathway that causes bronchoconstriction, and agonism of the Beta2-adrenoceptor to activate the Gs-mediated adenylyl cyclase pathway that promotes bronchodilation [PubMed PMID: 30171515].