PTGER1 (Prostaglandin E receptor EP1) is a member of the Prostanoid Receptor subfamily that mediates the diverse biological effects of prostaglandin E2 (PGE2). PGE2 has been implicated in regulation of the immune response, male erectile function, cervical and colorectal cancer, induction of labor, pain perception, blood pressure, bone resorption, and asthma. It is differentially expressed in the glandular epithelium of the endometrium across different phases of the menstrual cycle, and localizes to either the nucleus or apical membrane depending on the phase. In immunohistochemistry, PTGER1 has membranous positivity in the pituitary and on visceral epithelial cells of the kidney, Leydig cells in the testis, populations of epithelial cells in the lung and kidney, and it is expressed in the glandular epithelium of the endometrium. It is also found in a few other tissues and cell types including the pancreas, skin, stomach, intestinal neuroendocrine cells, the liver, ovarian oocytes and the heart. References: Mol Hum Reprod. 2011 Mar; 17(3): 182–192, PMID: 21112968; J Clin Invest. 2001;107(3):325-331, DOI:10.1172/JCI6749