Molecular pharmacology of the human prostaglandin D₂ receptor, CRTH2

Abstract

1 The recombinant human prostaglandin D 2 (PGD 2 ) receptor, hCRTH2, has been expressed in HEK293(EBNA) and characterized with respect to radioligand binding and signal transduction properties. High and low anity binding sites for PGD 2 were identi®ed in the CRTH2 receptor population by saturation analysis with respective equilibrium dissociation constants (K D ) of 2.5 and 109 nM. This revealed that the anity of PGD 2 for CRTH2 is eight times less than its anity for the DP receptor. 2 Equilibrium competition binding assays revealed that of the compounds tested, only PGD 2 and several related metabolites bound with high anity to CRTH2 (K i values ranging from 2.4 to 34.0 nM) with the following rank order of potency: PGD 2 413,14-dihydro-15-keto PGD 2 415-deoxy-D 3 Functional studies demonstrated that PGD 2 activation of recombinant CRTH2 results in decrease of intracellular cAMP in a pertussis toxin-sensitive manner. Therefore, we showed that CRTH2 can functionally couple to the G-protein G ai/o . PGD 2 and related metabolites were tested and their rank order of potency followed the results of the membrane binding assay. 4 By Northern blot analysis, we showed that, besides haemopoietic cells, CRTH2 is expressed in many other tissues such as brain, heart, thymus, spleen and various tissues of the digestive system. In addition, in situ hybridization studies revealed that CRTH2 mRNA is expressed in human eosinophils. Finally, radioligand binding studies demonstrated that two eosinophilic cell lines, butyric acid-dierentiated HL-60 and AML 14.3D10, also endogenously express CRTH2.

Antagonism of the prostaglandin D 2 receptor 1 suppresses nicotinic acid-induced vasodilation in mice and humans

“…Although the vasodilatory effect induced by 2 and 4 mg͞kg BW245C was less than that induced by the same dose of PGD 2 , these results are consistent with the binding affinities of PGD 2 and BW245C at mouse DP1 (21 vs. 250 nM) reported in the literature (27). By contrast, DK-PGD 2 (13,14-dihydro-15-keto-PGD 2 ), which is a DP2-selective agonist in humans (25) and has a K i value of 20 nM on mouse DP2 (26), had no effect on cutaneous vascular response at a dose of 2 mg͞kg (data not shown). These data suggest that PGD 2 causes cutaneous vasodilation in the mouse by acting through DP1, not DP2.…”

“…Because the magnitude of the reported PGD 2 increase far exceeds those reported for PGI 2 and TXA 2 , we focused on the potential role that PGD 2 might play in NA-induced vasodilation and examined whether one or both of the two PGD 2 receptors, DP1 and DP2, might play a role in vasodilation through use of specific receptor agonists. Administration of BW245C, a high-affinity agonist of human and mouse DP1 that is inactive at DP2 (25,26), caused a dosedependent increase of perfusion in the mouse ear (data not shown). Although the vasodilatory effect induced by 2 and 4 mg͞kg BW245C was less than that induced by the same dose of PGD 2 , these results are consistent with the binding affinities of PGD 2 and BW245C at mouse DP1 (21 vs. 250 nM) reported in the literature (27).…”

“…Activation of DP1 by PGD 2 leads to the stimulation of adenylate cyclase activity and increased intracellular cAMP levels (22). By contrast, activation of DP2 by PGD 2 results in intracellular calcium mobilization (23) and a decrease of intracellular cAMP (25). Thus, in addition to the ambiguity as to whether PGD 2 is the key driver of NA-induced flushing, the identity of the relevant PGD 2 receptor, DP1, DP2, or both, has not been explored.…”

The Extracellular Signal-regulated Kinase Mitogen-activated Protein Kinase/Ribosomal S6 Protein Kinase 1 Cascade Phosphorylates cAMP Response Element-binding Protein to Induce MUC5B Gene Expression via d-Prostanoid Receptor Signaling

“…One of them, prostaglandin D 2 (PGD 2 ), is thought to be involved in allergic reactions (18), and its actions are mediated via specific cell surface receptors coupled to G proteins, D prostanoid receptor 1 (DP1), and chemoattractant receptor homologous molecules expressed on Th2 cells (CRTH2/DP2) (19). Activation of DP receptor leads to a G smediated increase in intracellular cAMP and agonist-induced Ca 2ϩ flux (20). Moreover, PGD 2 signaling through CRTH2 coupled with the G i -type G protein leads to a decrease in cAMP, which subsequently stimulates intracellular Ca 2ϩ in various cell types (21).…”

Prostaglandin D2 DP1 receptor is beneficial in ischemic stroke and in acute exicitotoxicity in young and old mice

“…The DP1 receptor is coupled to G s protein and stimulates adenylyl cyclase, leading to increased levels of cyclic adenosine monophosphate (cAMP; Hata and Breyer 2004). A second type of DP receptor [DP2, also referred to as chemoattractant receptor-homologous molecule expressed on T helper cells (CRTH2)] has also been reported, but it has no significant homology with DP1 and has different biological functions and cellular distribution (Hirai et al 2001;Sawyer et al 2002), and some of its signaling is thought to be independent of PGD 2 levels. Furthermore, it has been documented that its activation decreases cAMP and increases intracellular calcium levels (Bohm et al 2004;Sandig et al 2006).…”