GPR55 is a G protein-coupled receptor that has been identified as a novel cannabinoid receptor, although its exact role is still controversial. Previously central cannabinoid (CB1) and peripheral cannabinoid (CB2), two widely characterized receptors have been shown to bind THC the active component of cannabis and other endocannabinoids. Mounting evidence suggests that additional receptors play a role in CB-related signal transduction and GPR55 has been identified as one of them. This receptor is widely expressed in the brain, specifically found in large dorsal root ganglion neurons. Along with binding THC, it also shows high affinity to anandamide, methanandamide, JWH 015, and many other CB ligands. The human protein shows 75% and 78% overall sequence homology with the rat and murine proteins, respectively. GPR55 is composed of 319 amino acids and has an expected molecular weight of 37 kDa. Post-translational modifications such as glycosylation may retard receptor electrophoretic migration and thereby protein signal may be detected above 37 kDa.