Muscarinic acetylcholine receptor M3 (IPR001183)
Short name: Musac_Ach_M3_rcpt
Overlapping homologous superfamilies
Muscarinic acetylcholine receptors are members of rhodopsin-like G-protein coupled receptor family. They play several important roles; they mediate many of the effects of acetylcholine in the central and peripheral nervous system and modulate a variety of physiological functions, such as airway, eye and intestinal smooth muscle contraction, heart rate and glandular secretions. The receptors have a widespread tissue distribution and are a major drug target in human disease. They may be effective therapeutic targets in Alzheimer's disease, schizophrenia, Parkinson's disease and chronic obstructive pulmonary disease [PMID: 15850824, PMID: 17762886].
There are five muscarinic acetylcholine receptor subtypes, designated M1-5 [PMID: 3443095, PMID: 3272174, PMID: 3037705, PMID: 9647869, PMID: 2470172]. The family can be further divided into two broad groups based on their primary coupling to G-proteins. M2 and M4 receptors couple to the pertussis-toxin sensitive Gi proteins, whereas M1, M3 and M5 receptors couple to Gq proteins [PMID: 9647869, PMID: 8853955], which activate phospholipase C. The different subtypes can also couple to a wide range of diverse signalling pathways, some of which are G protein-independent [PMID: 10841527, PMID: 14641022, PMID: 12725869]. All subtypes seem to serve as autoreceptors [PMID: 11714883], and knockout mice reveal the important neuromodulatory role played by this receptor family [PMID: 14744253, PMID: 15474550, PMID: 17762886].
Muscarinic acetylcholine M3 receptors are located in smooth muscles, endocrine glands, exocrine glands, lungs, pancreas and the brain [PMID: 11082420, PMID: 9149041, PMID: 8164520, PMID: 1723953, PMID: 16733808]. They are found in high levels in neuronal cells of the CNS, their distribution largely overlapping with that of M1 and M4 receptor subtypes. The primary role of M3 muscarinic receptors is contraction of smooth muscle, particularly of airway, ileum, iris and bladder [PMID: 22358844, PMID: 7504306, PMID: 8981565]. The receptors are also expressed on pancreatic beta-cells and in areas of the brain where they influence insulin secretion [PMID: 16753580, PMID: 16753580, PMID: 21982116], indicating that M3 receptors might be an important target for understanding the mechanisms of type 2 diabetes mellitus. M3 receptors are also involved in exocrine secretion, particularly of saliva [PMID: 15266016, PMID: 10944224].
GO:0016907 G protein-coupled acetylcholine receptor activity
GO:0005887 integral component of plasma membrane