Identification and functional characterization of chemokine receptor interacting proteins
Final Report Abstract
CCR5 and CXCR4 served as model proteins for the analysis of chemokine and G protein coupled receptor trafficking and signaling, in general. In the first part of this project, we established a method for the analysis of receptor internalization and recycling based on specific Bir A-mediated biotinylation of an acceptor peptide coupled to the receptor. This approach allows a more detailed analysis of receptor trafficking compared to classical antibody-based detection methods. Studies on constitutive internalization of the chemokine receptors CXCR4 and CCR5 revealed modulation of these processes by inverse or partial agonists. These results suggest an actively driven internalization process. Site-specific biotinylation may be applicable to studies on trafficking of transmembrane proteins, in general. In the second project we took advantage of an inducible heterodimerization system in order to better dissect ß-arrestin from classical G-protein-dependent effects of chemokine receptor signaling. Ligand-independent translocation of ß-arrestin to CXCR4 or CCR5 resulted in significantly attenuated G protein-mediated calcium release. Internalization studies revealed dimerizer-induced internalization levels for CXCR4 and CCR5 which was comparable to ligand-induced internalization, and this effect was further enhanced by translocation of a constitutively active ß-arrestin variant. Dimerizer-induced recruitment of ß-arrestin to the receptor was sufficient to mimic the specific ligand-induced intracellular receptor distribution of either CXCR4 or CCR5. Our data further provided evidence for direct ß-arrestin-mediated activation of downstream signaling via MAP kinases ERK 1/2. Overall this work clearly shows a prominent role for ß-arrestins in chemokine receptor trafficking and signaling which is independent from G protein-mediated effects.
Publications
- Analysis of Chemokine Receptor Trafficking by Site-Specific Biotinylation. PLoS One, Vol. 11. 2016, Issue 6: e0157502.
Liebick M, Schläger C, Oppermann M.
(See online at https://doi.org/10.1371/journal.pone.0157502) - Functional consequences of chemically-induced β-arrestin binding to chemokine receptors CXCR4 and CCR5 in the absence of ligand stimulation. Cellular Signalling, Vol. 38. 2017, pp. 201-211.
Liebick M., Henze S., Vogt V., Oppermann M.
(See online at https://doi.org/10.1016/j.cellsig.2017.07.010)
