Muscarinic acetylcholine receptor (subtype-specific: M1, M2, M3, M4, or M5) (mAChR (subtype-specific: M1, M2, M3, M4, M5))

Muscarinic acetylcholine receptors are a family of five G protein-coupled receptor subtypes (M1, M2, M3, M4, M5) that mediate the effects of the neurotransmitter acetylcholine in the central and peripheral nervous systems and in various tissues. M1, M3, and M5 primarily couple to Gq/11 proteins to activate phospholipase C, increasing intracellular calcium and protein kinase C activity, leading to excitatory cellular responses. M2 and M4 primarily couple to Gi/o proteins that inhibit adenylyl cyclase and decrease cAMP, producing inhibitory effects. They play essential roles in modulating heart rate, smooth muscle tone, glandular secretion, cognitive processes, and are therapeutic targets in numerous disorders including neurodegenerative diseases, cardiovascular and respiratory diseases, and overactive bladder[1][4][5][6].

Other names

Muscarinic receptorCholinergic receptor, muscarinicmAChR (with relevant subtype)Acetylcholine receptor, muscarinic

Agonists increase receptor-mediated signal transduction via G proteins (Gq/11 for M1/M3/M5; Gi/o for M2/M4). Antagonists inhibit receptor-mediated downstream signaling. Inverse agonists stabilize inactive receptor states, reducing constitutive activity. Allosteric modulators alter receptor affinity or efficacy for endogenous agonists.