PT  - JOURNAL ARTICLE
AU  - Gemma E. White
AU  - Eileen McNeill
AU  - Ivy Christou
AU  - Keith M. Channon
AU  - David R. Greaves
TI  - Site-Directed Mutagenesis of the CC Chemokine Binding Protein 35K-Fc Reveals Residues Essential for Activity and Mutations That Increase the Potency of CC Chemokine Blockade
AID  - 10.1124/mol.111.071985
DP  - 2011 Aug 01
TA  - Molecular Pharmacology
PG  - 328--336
VI  - 80
IP  - 2
4099  - http://molpharm.aspetjournals.org/content/80/2/328.short
4100  - http://molpharm.aspetjournals.org/content/80/2/328.full
SO  - Mol Pharmacol2011 Aug 01; 80
AB  - Chemokines of the CC class are key mediators of monocyte recruitment and macrophage differentiation and have a well documented role in many inflammatory diseases. Blockade of chemokine activity is therefore an attractive target for anti-inflammatory therapy. 35K (vCCI) is a high-affinity chemokine binding protein expressed by poxviruses, which binds all human and murine CC chemokines, preventing their interaction with chemokine receptors. We developed an Fc-fusion protein of 35K with a modified human IgG1 Fc domain and expressed this construct in human embryonic kidney 293T cells. Purified 35K-Fc is capable of inhibiting CC chemokine-induced calcium flux, chemotaxis, and β-arrestin recruitment in primary macrophages and transfected cells. To elucidate the residues involved in chemokine neutralization, we performed site-directed mutagenesis of six key amino acids in 35K and expressed the mutant Fc-fusion proteins in vitro. We screened the mutants for their ability to block chemokine-induced β-arrestin recruitment in transfected cells and to inhibit primary macrophage signaling in an electric cell substrate impedance sensing assay. Using a sterile model of acute inflammation, zymosan-induced peritonitis, we confirmed that wild-type 35K-Fc can reduce monocyte recruitment, whereas one mutant (R89A) showed a more pronounced blockade of monocyte influx and another mutant (E143K) showed total loss of function. We believe that 35K-Fc will be a useful tool for exploring the role of CC chemokines in chronic inflammatory pathologies, and we have identified a higher potency form of the molecule that may have potential therapeutic applications in chronic inflammatory disease.