{{DISPLAYTITLE:Prostaglandin EP2 receptor}} Prostaglandin E2 receptor 2, also known as EP2, is a prostaglandin receptor for prostaglandin E2 (PGE2) encoded by the human gene PTGER2: it is one of four identified EP receptors, the others being EP1, EP3, and EP4, which bind with and mediate cellular responses to PGE2 and also, but with lesser affinity and responsiveness, certain other prostanoids (see Prostaglandin receptors). EP has been implicated in various physiological and pathological responses. Gene The PTGER2 gene is located on human chromosome 14 at position p22.1 (i.e. 14q22.1), contains 2 introns and 3 exons, and codes for a G protein coupled receptor (GPCR) of the rhodopsin-like receptor family, Subfamily A14 (see rhodopsin-like receptors#Subfamily A14). Expression EP2 is widely distributed in humans. Its protein is expressed in human small intestine, lung, media of arteries and arterioles of the kidney, thymus, uterus, brain cerebral cortex, brain striatum, brain hippocampus, corneal epithelium, corneal choriocapillaries, Myometriuml cells, eosinophiles, sclera of the eye, articular cartilage, the corpus cavernosum of the penis, and airway smooth muscle cells; its mRNA is expressed in gingival fibroblasts, monocyte-derived dendritic cells, aorta, corpus cavernosum of the penis, articular cartilage, airway smooth muscle, and airway epithelial cells. In rats, the receptor protein and/or mRNA has been found in lung, spleen, intestine, skin, kidney, liver, long bones, and rather extensively throughout the brain and other parts of the central nervous system. EP2 expression in fibroblasts from the lungs of mice with bleomycin-induced pulmonary fibrosis and humans with Idiopathic pulmonary fibrosis is greatly reduced. In both instances, this reduced expression was associated with hypermethylation of CpG dinucleotide sites located in the first 420 base pairs upstream of the PTGER2 gene transcription start site of these fibroblasts. This suggests that EP2 expression is regulated by this methylation. Ligands Activating ligands The following standard prostaglandins have the following relative efficacies in binding to and activating EP2: PGE2>PGF2alpha>=PGI2>PGD2. The receptor binding affinity Dissociation constant Kd (i.e. ligand concentration needed to bind with 50% of available EP1 receptors) is ~13 nM for PGE2 and ~10 nM for PGE1 with the human receptor and ~12 nM for PGE2 with the mouse receptor. Because PGE2 activates multiple prostanoid receptors and has a short half-life in vivo due to its rapidly metabolism in cells by omega oxidation and beta oxidation, metabolically resistant EP2-selective activators are useful for the study of this receptor's function and could be clinically useful for the