The functional antagonist Met-RANTES: a modified agonist that induces differential CCR5 trafficking.
CC chemokine receptor 5 (CCR5) is a pro-inflammatory chemokine receptor that is expressed on cells of the immune system, and specializes in cell migration in response to inflammation and tissue damage. Due to its key role in cell communication and migration, this receptor is involved in various inflammatory and autoimmune diseases, in addition to HIV infection. Met-RANTES is a modified CCR5 ligand that has previously been shown to antagonize CCR5 activation and function in response to its natural ligands in vitro. In vivo, Met-RANTES is able to reduce inflammation in models of induced inflammatory and autoimmune diseases. However, due to the fact that Met-RANTES is also capable of partial agonist activity regarding receptor signaling and internalization, it is clear that Met-RANTES does not function as a conventional receptor antagonist. To further elucidate the effect of Met-RANTES on CCR5, receptor trafficking was investigated in a CHO-CCR5-GFP cell line using the Opera confocal plate reader. The internalization response of CCR5 was quantified, and showed that Met-RANTES internalized CCR5 in a slower, less potent manner than the agonists CCL3 and CCL5. Fluorescent organelle labeling and live cell imaging showed CCL3 and CCL5 caused CCR5 to traffic through sorting endosomes, recycling endosomes and the Golgi apparatus. In contrast, Met-RANTES caused CCR5 to traffic through sorting endosomes and the Golgi apparatus in a manner that was independent of recycling endosomes. As receptor trafficking impacts on cell surface expression and the ability of the receptor to respond to more ligand, this information may indicate an alternative regulation of CCR5 by Met-RANTES that allows the modified ligand to reduce inflammation through stimulation of a pro-inflammatory receptor.
Kiss
Debra L
DL
Discovery Biology, Eskitis Institute for Cell and Molecular Therapies, Brisbane Innovation Park, Griffith University, Don Young Road, Nathan, QLD, 4111, Australia.
Longden
James
J
Fechner
Gregory A
GA
Avery
Vicky M
VM
D000818:Animals; D065100:CCR5 Receptor Antagonists; D016466:CHO Cells; D002518:Ceramides / Q000378:metabolism; D054405:Chemokine CCL3 / Q000494:pharmacology; D018946:Chemokine CCL5 / Q000494:pharmacology*; D006224:Cricetinae; D003412:Cricetulus; D011992:Endosomes / Q000187:drug effects / Q000378:metabolism; D006056:Golgi Apparatus / Q000378:metabolism; D006801:Humans; D008024:Ligands; D021381:Protein Transport; D019713:Receptors, CCR5 / Q000819:agonists / Q000235:genetics / Q000378:metabolism*
D065100:CCR5 Receptor Antagonists; D002518:Ceramides; D054405:Chemokine CCL3; D018946:Chemokine CCL5; D008024:Ligands; C108335:RANTES, Met-; D019713:Receptors, CCR5