Prostaglandin D2 (PGD2) is an acidic lipid mediator that is derived from arachidonic acid by the sequential action of cyclooxygenase(s) (COX) and PGD2 synthase(s). Arachidonic acid is converted by COX-1 and COX-2 in a two-step process to first PGG2 and then PGH2. These unstable endoperoxide intermediates are converted to PGD2 by either the haematopoietic or lipocalin PGD2 synthase. PGD2 is produced in the brain where it might be involved in the regulation of sleep and other central nervous system (CNS) activities, including pain perception. In peripheral tissues, the richest cellular source of PGD2 is the mast cell[1]. The CRTH2 receptor is an important mediator of the inflammatory effects of PGD2. Strikingly, as a member of the subfamily of GPCR-A14, it has low homology to the rest of the prostaglandin receptors, but high sequence homology to chemoattractant receptors such as the N-formyl peptide receptors and cysteinyl leukotriene receptors. The receptor is expressed on TH2 cells, but not on TH1 cells, and hence the name chemoattractant receptor-homologous molecule expressed on TH2 cells (CRTH2)[2].

Prostanoid receptor subtypes listed: CRTH2, PGD2 (DP1), PGE2 (EP1), PGE2 (EP2), PGE2 (EP3), Thromboxane A2