Mas-related G-protein-coupled Receptor (MRGPR) 

Mas-related G-protein-coupled Receptor (MRGPR) is a novel family of sensory nerve specific orphan G protein coupled receptors (GPCRs). This family was characterized more than 30 years ago with the description of the Mas gene encoding for oncogene-like MAS receptors. The MRGPR family that now gathers more than 50 members in rodents and humans. On the basis of sequence homology, the family of MRGPRs can be divided into several subfamilies, namely, MRGPRA to MRGPRG and MRGPRX. Of these, the subfamilies MRGPR-A, MRGPR-B, and MRGPR-C are uniquely conserved in rodents, whereas the subfamily MRGPRX is characteristic among primates and humans. In humans, 4 MRGPRX genes, MRGPRX1, MRGPRX2, MRGPRX3, and MRGPRX4, have been described.

MRGPRs were first identified on specialized sensory neurons that encode itch (pruriceptors) and pain (nociceptors). Importantly, activation of Mrgprs expressed at the surface of sensory neurons has been shown to induce both itch and pain sensations. Most MRGPRs are associated with nociception and itch transmission, through their binding to various itch-inducing or painassociated substances: such as β–alanine, chloroquine (CQ), or substance P (SP).