PTGDR is a G protein-coupled receptor that has been shown to function as a prostanoid DP receptor. PTGDR is expressed in retinal choroid, ciliary epithelium, longitudinal and circular ciliary muscles, iris, small intestine and platelet membranes. The activity of this receptor is mainly mediated by G-S proteins that stimulate adenylate cyclase resulting in an elevation of intracellular cAMP and Ca2+. Knockout studies in mice suggest that the ligand of PTGDR, prostaglandin D2 (PGD2), functions as a mast cell-derived mediator to trigger asthmatic responses. Genetic variations in PTGDR are associated with susceptibility to asthma-related traits type 1 (ASRT1). Asthma-related traits include clinical symptoms of asthma, such as coughing, wheezing and dyspnea.