Prostaglandin E2 receptor 4 (EP4) is a prostaglandin receptor for prostaglandin E2 (PGE2) encoded by the PTGER4 gene in humans; it is one of four identified EP receptors, the others being EP1, EP2, and EP3, all of which bind with and mediate cellular responses to PGE2 and also, but generally with lesser affinity and responsiveness, certain other prostanoids (see Prostaglandin receptors). EP4 has been implicated in various physiological and pathological responses in animal models and humans.