G protein-coupled receptors (GPRs), also known as seven transmembrane receptors, heptahelical receptors or 7TM receptors, comprise a superfamily of proteins that play a role in many different stimulus-response pathways. G protein-coupled receptors translate extracellular signals into intracellular signals (G protein-activation) and they respond to a variety of signaling molecules, such as hormones and neurotransmitters. GPR15 (G protein-coupled receptor 15) is a 360 amino acid multi-pass membrane protein belonging to the G protein-coupled receptor 1 family. GPR15 is thought to function as a chemokine receptor and is encoded by a gene that maps to murine chromosome 16 C1.2.