PT  - JOURNAL ARTICLE
AU  - Michaël R. Paillasse
AU  - Céline Deraeve
AU  - Philippe de Medina
AU  - Loubna Mhamdi
AU  - Gilles Favre
AU  - Marc Poirot
AU  - Sandrine Silvente-Poirot
TI  - Insights into the Cholecystokinin 2 Receptor Binding Site and Processes of Activation
AID  - 10.1124/mol.106.029967
DP  - 2006 Dec 01
TA  - Molecular Pharmacology
PG  - 1935--1945
VI  - 70
IP  - 6
4099  - http://molpharm.aspetjournals.org/content/70/6/1935.short
4100  - http://molpharm.aspetjournals.org/content/70/6/1935.full
SO  - Mol Pharmacol2006 Dec 01; 70
AB  - The cholecystokinin (CCK) 2 receptor (CCK2R) appears as a pharmacological target for the treatment of many major diseases. To complete the mapping of the CCK2R binding site and its activation processes, we have looked for the receptor residues that interact with Trp6, an essential residue for CCK binding and activity. In our molecular model of the CCK-occupied CCK2R, the indole group of Trp6 stacked with the phenyl ring of Phe120 (ECL1) and interacted with the imidazole group of His381(H7.39) and the phenyl ring of Tyr385(H7.43). Mutagenesis and pharmacological studies validated these interactions. It is noteworthy that the mutation of Phe120 to Trp conferred constitutive activity to the CCK2R. Molecular modeling and experimental works identified the residues involved in the activation cascade initiated by Trp6 and revealed that the constitutively active F120W mutation mimics the conformational changes induced by Trp6 resulting in: 1) the exposure of Glu151(E3.49) of the conserved E/DRY motif 2) the formation of an amphiphatic pocket involving protonated Glu151(E3.49) and Leu330 (ICL3), and 3) the opening of the intracellular loops 2 and 3 and the release of Arg158 (ICL2). The R158A mutation was shown to affect inositol phosphate production, whereas the E151A and L330E mutations induced constitutive inositol phosphate production. Given that a constitutively active variant of the CCK2R has been identified in different cancers and the fact that the E151A mutant has been reported to induce tumors, these studies should help in the development of potent inverse agonists to inhibit the constitutive activation of the CCK2R. The American Society for Pharmacology and Experimental Therapeutics