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 (By similarity). Internalized receptors colocalized with RAB11A. The 329-DSEL-332 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 (By similarity). Thr-351 is a major site for PKC-induced internalization of the receptor (By similarity). Phosphorylated. Belongs to the G-protein coupled receptor 1 family.