Multiple glycosaminoglycan-binding epitopes of monocyte chemoattractant protein-3/CCL7 enable it to function as a non-oligomerizing chemokine

Salanga, C. L., Dyer, D. P. , Kiselar, J. G., Gupta, S., Chance, M. R. and Handel, T. M. (2014) Multiple glycosaminoglycan-binding epitopes of monocyte chemoattractant protein-3/CCL7 enable it to function as a non-oligomerizing chemokine. Journal of Biological Chemistry, 289(21), pp. 14896-14912. (doi: 10.1074/jbc.M114.547737) (PMID:24727473) (PMCID:PMC4031540)

Abstract

The interaction of chemokines with glycosaminoglycans (GAGs) facilitates the formation of localized chemokine gradients that provide directional signals for migrating cells. In this study, we set out to understand the structural basis and impact of the differing oligomerization propensities of the chemokines monocyte chemoattractant protein (MCP)-1/CCL2 and MCP-3/CCL7 on their ability to bind GAGs. These chemokines provide a unique comparison set because CCL2 oligomerizes and oligomerization is required for its full in vivo activity, whereas CCL7 functions as a monomer. To identify the GAG-binding determinants of CCL7, an unbiased hydroxyl radical footprinting approach was employed, followed by a focused mutagenesis study. Compared with the size of the previously defined GAG-binding epitope of CCL2, CCL7 has a larger binding site, consisting of multiple epitopes distributed along its surface. Furthermore, surface plasmon resonance (SPR) studies indicate that CCL7 is able to bind GAGs with an affinity similar to CCL2 but higher than the non-oligomerizing variant, CCL2(P8A), suggesting that, in contrast to CCL2, the large cluster of GAG-binding residues in CCL7 renders oligomerization unnecessary for high affinity binding. However, the affinity of CCL7 is more sensitive than CCL2 to the density of heparan sulfate on the SPR surfaces; this is likely due to the inability of CCL7 to oligomerize because CCL2(P8A) also binds significantly less tightly to low than high density heparan sulfate surfaces compared with CCL2. Together, the data suggest that CCL7 and CCL2 are non-redundant chemokines and that GAG chain density may provide a mechanism for regulating the accumulation of chemokines on cell surfaces.

• Item Type: Articles
• Additional Information: This work was supported, in whole or in part, by National Institutes of Health Grants R01 AI37113 (to T.M.H.), R01 EB09998 and P30 EB09688 (to M. R. C.), a Ruth L. Kirschstein NIGMS MARC Predoctoral Fellowship (F31) (to C.L.S.), and National Institute for Biomedical Imaging and Bioengineering Grants P30-EB-09998 and R01-EB-09688 (to S.G.).
• Glasgow Author(s) Enlighten ID: Dyer, Dr Douglas
• Authors: Salanga, C. L., Dyer, D. P., Kiselar, J. G., Gupta, S., Chance, M. R., and Handel, T. M.
• College/School: College of Medical Veterinary and Life Sciences > School of Infection & Immunity
• Journal Name: Journal of Biological Chemistry
• Publisher: American Society for Biochemistry and Molecular Biology
• ISSN: 0021-9258
• ISSN (Online): 1083-351X