The muscarinic acetylcholine receptor M1, also known as the cholinergic receptor, muscarinic 1, is a muscarinic receptor that in humans is encoded by the CHRM1 gene. It is localized to 11q13.
This receptor is found mediating slow EPSP at the ganglion in the postganglionic nerve, is common in exocrine glands and in the CNS.
It is predominantly found bound to G proteins of class Gq that use upregulation of phospholipase C and, therefore, inositol trisphosphate and intracellular calcium as a signalling pathway. A receptor so bound would not be susceptible to CTX or PTX. However, Gi (causing a downstream decrease in cAMP) and Gs (causing an increase in cAMP) have also been shown to be involved in interactions in certain tissues, and so would be susceptible to PTX and CTX respectively.
Occurrence in free living amoebae
A structural but not sequential homolog of the human M1 receptor has been reported in Acanthamoeba castellanii and Naegleria fowleri. Antagonists of human M1 receptors (e.g. atropine, diphenhydramine) have been shown to exert anti-proliferative effects on these pathogens.
It couples to Gq, and, to a small extent, Gi and Gs. This results in slow EPSP and decreased K+ conductance. It is preassembled to the Gq heterotrimer through a polybasic c-terminal domain.