Author: Jun Jin

Publisher:

Published: 2016

Total Pages: 418

ISBN-13:

CCR5 (c-c chemokine receptor type 5), a seven-transmembrane receptor, exhibits multiple conformations at the cell surface based on interactions with ligands, heterotrimeric G proteins, B-arrestins, neighboring gpcrs and membrane lipids, and also based on the location and trafficking of the receptor. These conformations play an important role in receptor functions including ligand binding, cell signaling and trafficking. CCR5 also serves as a co-receptor for r5-tropic human immunodeficiency virus, type 1 (HIV-1) entry. The native chemokines ccl3, ccl4, and ccl5 can compete with HIV-1 gp120 for binding CCR5, and are supposed to form a natural barrier against HIV-1. However, their antiviral activity is limited by a pool of CCR5 adopting conformations that have low-chemokine affinity at the cell surface. We demonetrated that this pool of CCR5 that is not stabilized by chemokines could represent a target for inhibiting HIV-1 infection. We exploited the characteristics of the chemokine analog psc-rantes, which displays potent anti-HIV-1 activity. We show that native chemokines fail to prevent high-affinity binding of psc-rantes, analog-mediated calcium release (in desensitization assays), and analog-mediated CCR5 internalization. These results indicate that this pool of spare CCR5 may bind psc-rantes but not native chemokines. Improved recognition of CCR5 by psc-rantes may explain why the analog promotes higher amounts of b-arrestin2/ccr5 complexes, thereby increasing CCR5 down-regulation and HIV- 1 inhibition. Together, these results highlight that spare CCR5, which might permit HIV-1 to escape from chemokines, should be targeted for efficient viral blockade. numerous studies also showed that gpcr form dimers or larger oligomers, a process that is involved in gpcr conformational changes. The molecular and functional relevance as well as the interaction interfaces of this organization are still poorly understood. To this aim, by using the HIV-1 coreceptor CCR5, we defined by chemical cross-link and molecular modeling two non-exclusive dimer interfaces, and a third one stabilized by the inverse agonist maraviroc, which indicates that CCR5 could also exhibit multiple conformations through homo-dimerization. We then showed, by site directed mutagenesis combined with saturation time-resolved fluorescence resonance energy transfer and a novel export assay, the essential role of dimerization in receptor transport to the cell surface. These results produce a consensual picture of the interfaces between protomers of class a dimers and reveal the impact of dimerization during biogenesis. They also provide new features of the marketed drug maraviroc highlighting both pharmacological chaperone and allosteric inhibitor activities. Overall, distinguishing multiple CCR5 conformations and their corresponding receptor functions has implications for understanding the selective use of CCR5 by HIV-1 and the development of improved strategies to block CCR5 use by HIV-1 .