Multiple affinity states of different cholecystokinin receptors

Huang, Shih-Che; Fortune, Kirk P.; Wank, Stephen A.; Kopin, Alan S.; Gardner, Jerry D.

doi:10.1016/s0021-9258(18)47167-0

Cited by 53 publications

(12 citation statements)

References 12 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This view is in line with structural and pharmacological data whereby binding affinity of agonists for 7TMR, including CCK receptors, is augmented by heterotrimeric G protein coupling, which, therefore, acts as allosteric regulators on the binding site. 9,58 It is worthy to note that changes in the position of some residues in the orthosteric binding site of CCK2R β state relative to CCK2R G state hinder binding of the non-peptide antagonist GV150013X whereas these changes less significantly affect CCK recognition. This observation is in line with data showing that a synthetic ligand can be sensitive to minor changes within the orthosteric binding site of a 7TMR whereas the natural agonist is not or is less sensitive to such changes.…”

Section: ■ Discussionmentioning

confidence: 99%

Distinct CCK-2 Receptor Conformations Associated with β-Arrestin-2 Recruitment or Phospholipase-C Activation Revealed by a Biased Antagonist

et al. 2013

View full text Add to dashboard Cite

Seven-transmembrane receptors (7TMRs), also termed G protein-coupled receptors (GPCRs), form the largest class of cell surface membrane receptors, involving several hundred members in the human genome. Nearly 30% of marketed pharmacological agents target 7TMRs. 7TMRs adopt multiple conformations upon agonist binding. Biased agonists, in contrast to non-biased agonists, are believed to stabilize conformations preferentially activating either G-protein- or β-arrestin-dependent signaling pathways. However, proof that cognate conformations of receptors display structural differences within their binding site where biased agonism initiates, are still lacking. Here, we show that a non-biased agonist, cholecystokinin (CCK) induces conformational states of the CCK2R activating Gq-protein-dependent pathway (CCK2R(G)) or recruiting β-arrestin2 (CCK2R(β)) that are pharmacologically and structurally distinct. Two structurally unrelated antagonists competitively inhibited both pathways. A third ligand (GV150013X) acted as a high affinity competitive antagonist on CCK2R(G) but was nearly inefficient as inhibitor of CCK2R(β). Several structural elements on both GV150013X and in CCK2R binding cavity, which hinder binding of GV150013X only to the CCK2R(β) were identified. At last, proximity between two conserved amino acids from transmembrane helices 3 and 7 interacting through sulfur-aromatic interaction was shown to be crucial for selective stabilization of the CCK2R(β) state. These data establish structural evidence for distinct conformations of a 7TMR associated with β-arrestin-2 recruitment or G-protein coupling and validate relevance of the design of biased ligands able to selectively target each functional conformation of 7TMRs.

show abstract

Section: ■ Discussionmentioning

confidence: 99%

Distinct CCK-2 Receptor Conformations Associated with β-Arrestin-2 Recruitment or Phospholipase-C Activation Revealed by a Biased Antagonist

et al. 2013

View full text Add to dashboard Cite

show abstract

“…A photoaffinity analogue of CCK incorporating two photolabile residues gave a covalent link between helices 1 and 7 of the same CCK receptor . However, the CCKA receptor has multiple affinity states, − only one of which may involve a dimer, and it is not clear which affinity state the photoaffinity probe detected. Indeed, the photoaffinity probe had a reported EC 50 value 4 orders of magnitude higher than that for wild-type CCK.…”

Section: Discussionmentioning

confidence: 99%

Dimerization of G-Protein-Coupled Receptors

et al. 2001

View full text Add to dashboard Cite

The evolutionary trace (ET) method, a data mining approach for determining significant levels of amino acid conservation, has been applied to over 700 aligned G-protein-coupled receptor (GPCR) sequences. The method predicted the occurrence of functionally important clusters of residues on the external faces of helices 5 and 6 for each family or subfamily of receptors; similar clusters were observed on helices 2 and 3. The probability that these clusters are not random was determined using Monte Carlo techniques. The cluster on helices 5 and 6 is consistent with both 5,6-contact and 5,6-domain swapped dimer formation; the possible equivalence of these two types of dimer is discussed because this relates to activation by homo- and heterodimers. The observation of a functionally important cluster of residues on helices 2 and 3 is novel, and some possible interpretations are given, including heterodimerization and oligomerization. The application of the evolutionary trace method to 113 aligned G-protein sequences resulted in the identification of two functional sites. One large, well-defined site is clearly identified with adenyl cyclase, beta/gamma and regulator of G-protein signaling (RGS) binding. The other G-protein functional site, which extends from the ras-like domain onto the helical domain, has the correct size and electrostatic properties for GPCR dimer binding. The implications of these results are discussed in terms of the conformational changes required in the G-protein for activation by a receptor dimer. Further, the implications of GPCR dimerization for medicinal chemistry are discussed in the context of these ET results.

show abstract

“…Benzodiazepines represent one group, comprising highly potent and selective CCK 1 and CCK 2 receptor antagonists. 16,18,19 Of particular interest, benzodiazepines have been shown to act at an allosteric site in the * To whom correspondence should be addressed. Phone: (480)301-6650.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and in Vitro Characterization of Radioiodinatable Benzodiazepines Selective for Type 1 and Type 2 Cholecystokinin Receptors

et al. 2009

View full text Add to dashboard Cite

Radiolabeled antagonists of specific peptide receptors identify a higher number of receptor binding sites than agonists and may thus be preferable for in vivo tumor targeting. In this study, two novel radioiodinated 1,4-benzodiazepines, (9), were developed. They were characterized in vitro as high affinity selective antagonists at cholecystokinin type 1 and 2 (CCK 1 and CCK 2 ) receptors using receptor binding, calcium mobilization, and internalization studies. Their binding to human tumor tissues was assessed with in vitro receptor autoradiography and compared with an established peptidic CCK agonist radioligand. The 125 I-labeled CCK 1 receptor-selective compound 9 often revealed a substantially higher amount of CCK 1 receptor binding sites in tumors than the agonist 125 I-CCK. Conversely, the radioiodinated CCK 2 receptor-selective compound 7 showed generally weaker tumor binding than 125 I-CCK. In conclusion, compound 9 is an excellent radioiodinated non-peptidic antagonist ligand for direct and selective labeling of CCK 1 receptors in vitro. Moreover, it represents a suitable candidate to test antagonist binding to CCK 1 receptorexpressing tumors in vivo.

show abstract

Multiple affinity states of different cholecystokinin receptors

Cited by 53 publications

References 12 publications

Distinct CCK-2 Receptor Conformations Associated with β-Arrestin-2 Recruitment or Phospholipase-C Activation Revealed by a Biased Antagonist

Distinct CCK-2 Receptor Conformations Associated with β-Arrestin-2 Recruitment or Phospholipase-C Activation Revealed by a Biased Antagonist

Dimerization of G-Protein-Coupled Receptors

Synthesis and in Vitro Characterization of Radioiodinatable Benzodiazepines Selective for Type 1 and Type 2 Cholecystokinin Receptors

Contact Info

Product

Resources

About