Regulation of membrane cholecystokinin-2 receptor by agonists enables classification of partial agonists as biased agonists.

Given the importance of G-protein-coupled receptors as pharmacological targets in medicine, efforts directed at understanding the molecular mechanism by which pharmacological compounds regulate their presence at the cell surface is of paramount importance. In this context, using confocal microscopy and bioluminescence resonance energy transfer, we have investigated internalization and intracellular trafficking of the cholecystokinin-2 receptor (CCK2R) in response to both natural and synthetic ligands with different pharmacological features. We found that CCK and gastrin, which are full agonists on CCK2R-induced inositol phosphate production, rapidly and abundantly stimulate internalization.

Linking non-peptide ligand binding mode to activity at the human cholecystokinin-2 receptor.

Given the importance of G-protein-coupled receptors as pharmacological targets in medicine, efforts directed at the understanding the molecular mechanism by which pharmacological compounds regulate their activity is of paramount importance. Here, we investigated at an atomic level the mechanism of inverse agonism and partial agonism of two high affinity, high selectivity very similar non-peptide ligands of the cholecystokinin-2 receptor (CCK2R) which differ by the absence or presence of a methyl group on their indole moiety. Using in silico, site-directed mutagenesis and pharmacological experiments, we demonstrated that these functionally different activities are due to differing anchoring modes of the two compounds to a residue of helix II (Thr-2.

Insights into the binding and activation sites of the receptors for cholecystokinin and gastrin.

CCK receptors represent potential targets in a number of diseases. Knowledge of CCK receptor binding sites is a prerequisite for the understanding of the molecular basis for their ligand recognition, partial agonism, ligand-induced trafficking of signalling. In the current paper, we report studies from our laboratory and others which have provided new data on the molecular basis of the pharmacology and functioning of CCK1 and CCK2 receptors.

Mechanism of activation of a G protein-coupled receptor, the human cholecystokinin-2 receptor.

G protein-coupled receptors (GPCRs) represent a major focus in functional genomics programs and drug development research, but their important potential as drug targets contrasts with the still limited data available concerning their activation mechanism. Here, we investigated the activation mechanism of the cholecystokinin-2 receptor (CCK2R). The three-dimensional structure of inactive CCK2R was homology-modeled on the basis of crystal coordinates of inactive rhodopsin.

Validated ligand binding sites in CCK receptors. next step: computer-aided design of novel CCK ligands.

Computer-aided drug design becomes an important part of G-protein coupled receptors (GPCR) drug discovery process that is applied for improving the efficiency of derivation and optimization of novel ligands. It represents the combination of methods that use structural information of a receptor binding site of known ligands to design new ligands. In this report, we give a brief description of ligand binding sites in cholecystokinin and gastrin receptors (CCK1R and CCK2R) which were delineated using experimental and computational methods, and then, we show how the validated ligand binding sites can be used to design and improve novel ligands.

Partial agonism, neutral antagonism, and inverse agonism at the human wild-type and constitutively active cholecystokinin-2 receptors.

Cholecystokinin receptor-2 (CCK2R) is a G protein receptor that regulates a number of physiological functions. Activation of CCK2R and/or expression of a constitutively active CCK2R variant may contribute to human diseases, including digestive cancers. Search for antagonists of the CCK2R has been an important challenge during the last few years, leading to discovery of a set of chemically distinct compounds.

5-(tryptophylamino)-1,3-dioxoperhydropyrido[1,2-c]pyrimidine-based cholecystokinin receptor antagonists: reversal of CCK1 receptor subtype selectivity toward CCK2 receptors.

With the aim of reversing selectivity or antagonist/agonist functionality in the 5-(tryptophylamino)-1,3-dioxoperhydropyrido[1,2-c]pyrimidine-derived potent and highly selective CCK(1) antagonists, a series of 4-benzyl and 4-methyl derivatives have been synthesized. Whereas the introduction of the benzyl group led, in all cases, to complete loss of the binding affinity, the incorporation of the methyl group gave a different result depending on the stereochemistry of the 1,3-dioxoperhydropyrido[1,2-c]pyrimidine scaffold. Thus, the introduction of the methyl group into the (4aS,5R)-diastereoisomers, giving a (4S)-configuration, produced a 3-fold increase in the CCK(1) binding potency and selectivity.