Abstract
The chemokine receptor CCR2, which has been implicated in a variety of inflammatory, autoimmune, and cardiovascular conditions, binds several natural chemokine ligands. Here, we assessed the recruitment of β-arrestin to CCR2 in response to these ligands using bioluminescence resonance energy transfer technology. Compared with CCL2, which was considered as a full agonist, other CCR2 ligands were partial agonists with reduced efficacy and potency. Agonist potencies were not a function of their affinity for CCR2. Efficacy of arrestin recruitment matched that of agonist-induced CCR2 internalization. Although the potency and efficacy rank orders of the ligands in arrestin recruitment were similar to those observed for Gαi1 activation, arrestin recruitment was at least in part resistant to Gαi/o-inactivating pertussis toxin, suggesting partial independence from Gαi/o. The degree of pertussis toxin resistance of arrestin recruitment was different between the chemokines. Moreover, qualitative differences between the arrestin responses to the different ligands were identified in the stability of the response: although CCL7-induced arrestin recruitment had a half-life of less than 15 min, CCL8 and CCL13 induced stable CCR2-arrestin interactions. Finally, the ligands stabilized different conformations of the CCR2 homodimer. Our results support the validity of models for receptor-ligand interactions in which different ligands stabilize different receptor conformations also for endogenous receptor ligands, with corresponding implications for drug development targeting CCR2.
Footnotes
This study was supported by the Canadian Institutes of Health Research (CIHR) [Grant HOP-79210]; a CIHR fellowship; and a Fondation de l'Hôpital Sainte-Justine fellowship. N.H. is a CIHR New Investigator.
Article, publication date, and citation information can be found at http://molpharm.aspetjournals.org.
doi:10.1124/mol.110.068486.
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ABBREVIATIONS:
- CCR
- CC chemokine receptor
- CCL
- CC chemokine ligand
- MCP
- monocyte chemotactic protein
- GPCR
- G-protein-coupled receptor
- BRET
- bioluminescence resonance energy transfer
- HEK
- human embryonic kidney
- PTX
- pertussis toxin
- YFP
- yellow fluorescent protein
- RLuc
- Renilla reniformis luciferase
- ANOVA
- analysis of variance.
- Received August 30, 2010.
- Accepted November 18, 2010.
- Copyright © 2011 The American Society for Pharmacology and Experimental Therapeutics
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