Anti-M4R antibodies enable researchers to detect and measure the M4R antigen in biological samples. This target is a reported synonym of the CHRM4 gene, which encodes cholinergic receptor muscarinic 4. This protein is known to function in receptor-mediated signaling pathways and chemical synaptic transmission, among other biological roles. The human version of M4R has a canonical amino acid length of 479 residues and a protein mass of 53 kilodaltons. It is reported to be localized in the cell membrane of cells and notably expressed in the stomach, small intestine, duodenum, and cerebral cortex. M4R is a member of the G-protein coupled receptor 1 protein family.