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J Biol Chem. 2018 Jun 8;293(23):8787-8801. doi: 10.1074/jbc.RA117.001067. Epub 2018 Apr 20.

Regulation of C-C chemokine receptor 5 (CCR5) stability by Lys197 and by transmembrane protein aptamers that target it for lysosomal degradation.

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From the Department of Genetics, Yale School of Medicine, New Haven, Connecticut 06520-8005.
From the Department of Genetics, Yale School of Medicine, New Haven, Connecticut 06520-8005,
the Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520-8024.
the Department of Therapeutic Radiology, Yale School of Medicine, New Haven, Connecticut 06520-8040, and.
the Yale Cancer Center, New Haven, Connecticut 06520-8028.


C-C motif chemokine receptor 5 (CCR5) is a cell surface-associated, immune-regulatory G protein-coupled receptor (GCPR) with seven transmembrane helices. We previously reported the isolation and initial characterization of short artificial transmembrane protein aptamers, named "traptamers," that specifically down-regulate CCR5 expression and inhibit infection of human T cells by HIV strains that use CCR5 as a co-receptor. Here, we investigated the mechanism of traptamer-mediated CCR5 down-regulation and show that most of the traptamers (designated class 1 traptamers) form a stable complex with CCR5 and target it for lysosome-mediated degradation. The ability of these traptamers to down-regulate CCR5 depended on Lys197 in the fifth transmembrane helix of CCR5. In the absence of traptamers, substitution of Lys197 to an uncharged amino acid increased CCR5 stability, and introduction of a lysine at the homologous position in CCR2b, a related chemokine receptor, decreased CCR2b levels. The prototypic class 2 traptamer BY6M4 also formed a complex with CCR5, but CCR5 down-regulation caused by class 2 traptamers did not depend on the lysosome or on Lys197 These results demonstrate that traptamers use diverse mechanisms to down-regulate CCR5 and identify a specific amino acid that plays a central role in controlling chemokine receptor stability. Further studies of these traptamers are likely to provide new insights into CCR5 metabolism and biology and may suggest new therapeutic approaches to modulate the levels of CCR5 and other GPCRs.


C-C chemokine receptor type 5 (CCR5); CCR2b; E5 protein; G protein-coupled receptor (GPCR); HIV co-receptor; chemokine; human immunodeficiency virus (HIV); lysosome; proximity ligation assay; transmembrane protein; traptamer

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