TarGETing CCR2 and CCR5 chemokine REceptors DImers: towards a better regulation of inflammation – GET-REDI

The chemokine receptors CCR2 and CCR5 belong to the G protein-coupled receptor family composed of 7 transmembrane domains. They mediate acute inflammation by driving leukocytes migration, and contribute to chronic inflammation and malignancy. They represent key therapy targets for the treatment of various inflammatory diseases.
To date, no antagonist targeting CCR2 has been approved. The CCR5 inhibitor, maraviroc, approved for the treatment of HIV infection, is being studied for its ability to modulate the inflammatory response.
Recent data by us and others have identified that different conformational populations of CCR2 and CCR5 exist at the cell surface and differ in their ligand binding and functional properties. This opens up new therapeutic opportunities, by targeting a given conformation.
Receptor oligomerization is one of the mechanisms that modulate the diversity of receptor conformational state. CCR2 and CCR5 can form homo- and hetero-dimers (CCR2/CCR5). We recently identified three homo-dimeric organizations of CCR5 and showed that (i) CCR5 dimerization is required for the receptor targeting to the cell surface, (ii) regulates its mobility at the cell surface, and (iii) impact ligand binding. This suggests that receptor dimerization influence drug selectivity. However, no therapeutic strategy aimed at modulating the dimerization of these receptors has been proposed.
In this project, we propose to study CCR2 homo- and hetero-dimers with the goal to develop molecules targeting a specific state of the receptor. Our objectives are: (1) to characterize CCR2 homo- and hetero-dimers by in silico modelling and experimental validations; (2) to study the functional consequences of dimerization; and (3) to search for modulators of CCR2, CCR5, and the heterodimer trough two advanced screening strategies.
To detect dimers, we will use, in addition to classical approaches of covalent bridging and energy transfer, two innovative techniques based on the RUSH system and on TIRF microscopy. Simultaneous use of two complementary screening strategies to identify new modulators targeting CCR2 and/or CCR5 will increase our chances of success. The first strategy, based on recent studies showing that ligands differently alter dimer interfaces, has never been proposed before. The second strategy, we recently set up, is based on the RUSH system, and proved its efficacy to identify receptor trafficking modulators. After in vitro validation, we will evaluate the effect of the best hits on inflammatory responses in two animal models.
The strength and innovative nature of this project is based on the multiplicity and the complementarity of the methods and expertise combining in silico modeling, biochemistry, biophysics, cell biology, live cell imaging, and animal model. For its success, we will reunite 4 teams with expertise in the fields of GPCRs pharmacology (A. Brelot, Institut Pasteur, Paris); drug design (E. Kellenberger, Strasbourg university), image analysis (T. Lagache, Institut Pasteur, Paris), and inflammatory pathologies (C. Combadière, CIMI, Paris). This 48 months project requires to hire 4 persons (2 postdocs, 1 PhD student, 1 engineer). We are in a unique position to obtain candidates possessing allosteric properties with the potential to modulate homo- and hetero-dimers. They will serve as tools to study oligomers functions in vitro and in vivo. They will also represent potential inhibitors of inflammatory responses.