Identification of indole derivatives exclusively interfering with a G protein-independent signaling pathway of the prostaglandin D2 receptor CRTH2.

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Mathiesen JM, Ulven T, Martini L, Gerlach LO, Heinemann A, Kostenis E

Identification of indole derivatives exclusively interfering with a G protein-independent signaling pathway of the prostaglandin D2 receptor CRTH2.

Mol Pharmacol. 2005 Aug;68(2):393-402. Epub 2005 May 3.

PubMed ID

15870392 [ View in PubMed

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Abstract

The anti-inflammatory drugs indomethacin and ramatroban, the latter showing clinical efficacy in treating allergic asthma, have been shown to act as a classic agonist and antagonist, respectively, of the G protein-coupled chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2 receptor). Here, we report the identification of two indole derivatives 1-(4-ethoxyphenyl)-5-methoxy-2-methylindole-3-carboxylic acid and N(alpha)-tosyltryptophan (hereafter referred to as 1 and 2, respectively), which are structurally related to indomethacin and ramatroban but which selectively interfere with a specific G protein-independent signaling pathway of CRTH2. In whole-cell saturation-binding assays, 1 and 2 both increase the number of [(3)H]prostaglandin D2 (PGD2)-recognizing CRTH2 sites and the affinity of PGD2 for CRTH2. Enzyme-linked immunosorbent assays show that they do not alter the total number of CRTH2 receptors on the cell surface. Analysis of their binding mode indicates that unlike indomethacin or ramatroban, 1 and 2 can occupy CRTH2 simultaneously with PGD2. On a functional level, however, 1 and 2 do not interfere with PGD2-mediated activation of heterotrimeric G proteins by CRTH2. In contrast, both compounds inhibit PGD2-mediated arrestin translocation via a G protein-independent mechanism. In human eosinophils endogenously expressing CRTH2, 1 selectively decreases the efficacy but not the potency of PGD2-induced shape change, unlike ramatroban, which displays competitive antagonistic behavior. These data show for the first time that "antagonists" can cause markedly dissimilar degrees of inhibition for different effector pathways and suggest that it may be possible to develop novel classes of specific signal-inhibiting drugs distinct from conventional antagonists.

DrugBank Data that Cites this Article

Drug Targets

Drug	Target	Kind	Organism	Pharmacological Action	Actions
Indomethacin	Prostaglandin D2 receptor 2	Protein	Humans	Unknown	Other/unknown	Details