Prostanoid receptors: Structures, properties, and functions

Prostanoids are the cyclooxygenase metabolites of arachidonic acid and incl ude prostaglandin (PG) D-2, PGE(2), PGF(2 alpha), PGI(2), and thromboxne A( 2). They are synthesized and released upon cell stimulation and act on cell s in the vicinity of their synthesis to exert their actions. Receptors medi ating the actions of prostanoids were recently identified and cloned. They are G protein-coupled receptors with seven transmembrane domains. There are eight types and subtypes of prostanoid receptors that are encoded by diffe rent genes but as a whole constitute a subfamily in the superfamily of the rhodopsin-type receptors. Each of the receptors was expressed in cultured c ells, and its ligand-binding properties and signal transduction pathways we re characterized. Moreover, domains and amino acid residues conferring the specificities of ligand binding and signal transduction are being clarified . Information also is accumulating as to the distribution of these receptor s in the body. It is also becoming clear for some types of receptors how ex pression of their genes is regulated. Furthermore, the gene for each of the eight types of prostanoid receptor has been disrupted, and mice deficient in each type of receptor are being examined to identify and assess the role s played by each receptor under various physiological and pathophysiologica l conditions. In this article, we summarize these findings and attempt to g ive an overview of the current status of research on the prostanoid recepto rs.