GPR55 is an orphan G protein-coupled receptor with a typical seven-transmembrane domain structure. It is expressed in various tissues including the brain, spleen, intestines, and bones, regulating pain perception, skeletal growth, metabolism, and immune response. GPR55 activates multiple signaling pathways such as ERK, AKT, and intracellular calcium ion concentration increase, in response to endogenous and exogenous ligands, such as certain endocannabinoids and plant cannabinoids. Its specific expression pattern and functions indicate its potential role in disease development, with gene mutations or expression changes associated with inflammation, pain, cancer, and osteoporosis, among other conditions.