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. GPR25 (G protein-coupled receptor 25) is a 361 amino acid multi-pass membrane protein that belongs to the G protein-coupled receptor family and functions as an orphan receptor, possibly playing a role in signal transduction throughout the cell. The gene encoding GPR25 maps to human chromosome 1, which spans 260 million base pairs, contains over 3,000 genes and comprises nearly 8% of the human genome.