G protein-coupled receptors (GPRs or GPCRs), are members of the largest protein family and play a role in many different stimulus-response pathways. G-protein coupled receptors mediate extracellular signals into intracellular signals (G-protein activation). They respond to a great variety of signaling molecules, including hormones, neurotransmitters and other proteins and peptides. GPR173 is also known as super conserved receptor expressed in brain 3 (SREB3). It is an orphan receptor that is expressed primarily in brain and ovary tissues.