The prostaglandin D2 receptor is a member of the G-protein-coupled receptor (GPCR) family (subfamily: prostanoid). It has been shown to function as a prostanoid DP receptor. Its activity 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 this receptor, prostaglandin D2 (PGD2), functions as a mast cell-derived mediator to trigger asthmatic responses. Prostaglandin D2 receptor has been reported to be expressed in human small intestine, colon (goblet cells), eye, and eosinophils. ESTs have been isolated from human brain libraries.