Receptor for prostaglandin D2 (PGD2). Coupled to the G(i)-protein. Receptor activation may result in pertussis toxin-sensitive decreases in cAMP levels and Ca(2+) mobilization. PI3K signaling is also implicated in mediating PTGDR2 effects. PGD2 induced receptor internalization. CRTH2 internalization can be regulated by diverse kinases such as, PKC, PKA, GRK2, GPRK5/GRK5 and GRK6. Receptor activation is responsible, at least in part, in immune regulation and allergic/inflammation responses. Internalized receptors colocalized with RAB11A. Widespread expression. High expression in stomach, small intestine, heart and thymus. Intermediate expression in colon, spinal cord and peripheral blood and low expression in brain, skeletal muscle and spleen. Expressed also on Th2- and Tc2- type cells, eosinophils and basophils. The 330-DSEL-333 motif is involved in the recycling of PTGDR2 to the cell surface after agonist-induced internalization. This motif seems to be required for GRK2 and GPRK5/GRK5 to promote agonist-induced internalization. Thr-347 is a major site for PKC-induced internalization of the receptor. Phosphorylated. Belongs to the G-protein coupled receptor 1 family. Extended N-terminus.