Protein Domain : Muscarinic acetylcholine receptor M2 IPR001065

Type	Family
Description	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 [ , ]. There are five muscarinic acetylcholine receptor subtypes, designated M1-5 [ , , , , ]. 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 [, ], 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 [, , ].All subtypes seem to serve as autoreceptors [ ], and knockout mice reveal the important neuromodulatory role played by this receptor family [, , ].Muscarinic acetylcholine receptor M2 is highly expressed in the heart and has a profound role in the control of myocyte contraction [ , , ]. The release of acetylcholine from vagal parasympathetic neurones reduces the heart beating frequency by acting almost exclusively at M2 muscarinic receptors [, , ]. The M2 receptor is found at much lower levels in the CNS, where it has limited distribution []. It is co-expressed with the M3 muscarinic receptors in smooth muscle [] and it appears to play a much smaller role in the smooth muscle contractile response []. M2 receptors are also expressed in the thermo-regulatory centres of the hypothalamus and are likely to be involved in the regulation of body temperature [].
Short Name	Musac_Ach_M2_rcpt