Prostaglandin F receptor (FP) is a receptor belonging to the prostaglandin (PG) group of receptors. FP binds to and mediates the biological actions of Prostaglandin F2α (PGF2α). It is encoded in humans by the PTGFR gene. Gene The PTGFR gene is located on human chromosome 1 at position p31.1 (i.e. 1p31.1), contains 7 exons, and codes for a G protein coupled receptor (GPCR) of the rhodopsin-like receptor family, Subfamily A14 (see rhodopsin-like receptors#Subfamily A14). PTGFR is expressed as two alternatively spliced transcript variants encoding different isoforms, FPA and FPB, which have different C-terminal lengths. MicroRNA miR-590-3p binds to the Three prime untranslated region of the FP gene to repress its translation. miR-590-3p thus appears to be a negative regulator of FP expression in various cell types. Expression In humans, FP mRNA and/or protein is highly expressed in the uterine myometrium; throughout the eye (endothelium and smooth muscle cells of blood vessels of the iris), ciliary body and choroid plexus; ciliary muscle (circular muscle, collagenous connective tissues; sclera; and ovarian (follicles and corpus luteum). Studies in mice indicate that FP mRNA and/or protein is expressed in diverse tissues including the kidney (distal tubules), uterus, and ovary (Luteal cells of corpus luteum. Ligands Activating ligands The FP receptor is the least selective of the prostenoid receptors in that it is responsive to PGD2 and to a lesser extent PGE2 at concentrations close to those of PGF2α. Standard prostanoids have the following relative efficacies as receptor ligands in binding to and activating FP: PGF2α>PGD2>PGE2>PGI2=TXA2. In typical binding studies, PGF2α has one-half maximal binding and cell stimulating actions at ~1 nanomolar whereas PGD2 and PGE2 are ~5- to 10-fold and 10-100-fold weaker than this. The synthetic analogs that like PGF2α act as selective receptor agonists of FP viz., cloprostenol, flupostenol, latanoprost, and tafluprost (acid form) have FP binding affinities and stimulating potencies similar to PGF2α while others as enprostil, sulprostone, U46619, carbacyclin, and iloprost are considerably weaker FP agonists. Fluprostenol is a widely used clinically as a selective FP receptor agonist; latanoprost is a suitable substitute. Inhibiting ligands Currently, there are no selective receptor antagonists for FP. Mechanism of cell activation FP is classified as a contractile type of prostenoid receptor based on its ability, upon activation, to contract certain smooth muscle preparations and smooth muscle-containing tissues such as those of the uterus. When bound to PGF2α or other of its agonists, FP mobilizes