Chemokine Receptor CCR3 Function Is Highly Dependent on Local pH and Ionic Strength

Volume 272, Number 45, Issue of November 7, 1997 pp. 28206-28209

COMMUNICATION:
Chemokine Receptor CCR3 Function Is Highly Dependent on Local pH and Ionic Strength

Daniel J. Dairaghi , Elizabeth R. Oldham , Kevin B. Bacon and Thomas J. Schall

 

The CC chemokine receptor 3 (CCR3) plays an important role in the regulation of the migration of eosinophils, a leukocyte population involved in many inflammatory pathologies including asthma. CCR3 binds to the CC chemokine eotaxin, a promigratory cytokine originally isolated as the key component in a model of eosinophil-induced airway inflammation. We show here that eotaxin/CCR3 binding interactions exhibit a marked sensitivity to relatively small changes in the extracellular environment. In particular, modest variations in the pH and the level of sodium chloride over a range of physiologic and near physiologic conditions had dramatic effects on eotaxin binding and CCR3-mediated cytoplasmic Ca²⁺ mobilization. These biochemical indices were reflected at the functional level as well; small changes in pH and salt also resulted in striking changes in the migration of primary human eosinophils in vitro. These results reveal that relatively small perturbations in extracellular buffer conditions can yield widely disparate interpretations of CCR3 ligand binding and affinities and suggest that modulation of the tissue microenvironment might be utilized to control the affinity and efficacy of chemokine-mediated cell migration.

---

INTRODUCTION

Eosinophils are involved in many inflammatory pathologies including asthma, urticaria, and hypereosinophilic syndrome (1-3). The CC chemokine receptor 3 (CCR3)¹ and its ligands, most notably eotaxin, have been shown to play a central role in controlling eosinophil migration (4-12). Eotaxin was originally isolated as a protein responsible for eosinophil chemoattraction in the bronchoalveolar fluid of allergen-sensitized guinea pigs (9). Subsequently, the human and mouse homologs were identified and also shown to be chemoattractants for eosinophils (10, 12). Eotaxin has been shown to be a primary ligand for the seven-transmembrane G protein-coupled receptor CCR3. The genes for CCR3 and the related receptors CCR1-CCR5 are encoded within a 130-kilobase region of human chromosome 3 (13) indicating recent gene duplication and divergence and perhaps explaining the partial overlap of chemokine ligand repertoires. CCR3 is highly expressed on primary human eosinophils (50,000-400,000 sites/cell) (5-7), consistent with the potent ability of eotaxin to selectively influence the migration of these cells.

The mechanisms by which specific cells are attracted by specific chemokines have been a topic of intense interest and clinical relevance. The question is complicated by the fact that a number of closely related chemokine receptors with overlapping specificities are expressed on many different classes of leukocytes. In addition, the affinity of a specific receptor/ligand interaction can vary depending upon the specific cell type expressing the chemokine receptor, perhaps due to posttranslational modification events or G protein coupling. Thus it appears that cells can modulate their responses to chemokines, but how this is done is not yet clear 

The CC chemokine receptor 3 (CCR3) plays an important role in the regulation of the migration of eosinophils, a leukocyte population involved in many inflammatory pathologies including asthma. CCR3 binds to the CC chemokine eotaxin, a promigratory cytokine originally isolated as the key component in a model of eosinophil-induced airway inflammation. We show here that eotaxin/CCR3 binding interactions exhibit a marked sensitivity to relatively small changes in the extracellular environment. In particular, modest variations in the pH and the level of sodium chloride over a range of physiologic and near physiologic conditions had dramatic effects on eotaxin binding and CCR3-mediated cytoplasmic Ca²⁺ mobilization. These biochemical indices were reflected at the functional level as well; small changes in pH and salt also resulted in striking changes in the migration of primary human eosinophils in vitro. These results reveal that relatively small perturbations in extracellular buffer conditions can yield widely disparate interpretations of CCR3 ligand binding and affinities and suggest that modulation of the tissue microenvironment might be utilized to control the affinity and efficacy of chemokine-mediated cell migration

Eosinophils are involved in many inflammatory pathologies including asthma, urticaria, and hypereosinophilic syndrome. The CC chemokine receptor 3 (CCR3) and its ligands, most notably eotaxin, have been shown to play a central role in controlling eosinophil migration . Eotaxin was originally isolated as a protein responsible for eosinophil chemoattraction in the bronchoalveolar fluid of allergen-sensitized guinea pigs . Subsequently, the human and mouse homologs were identified and also shown to be chemoattractants for eosinophils . Eotaxin has been shown to be a primary ligand for the seven-transmembrane G protein-coupled receptor CCR3. The genes for CCR3 and the related receptors CCR1-CCR5 are encoded within a 130-kilobase region of human chromosome 3  indicating recent gene duplication and divergence and perhaps explaining the partial overlap of chemokine ligand repertoires. CCR3 is highly expressed on primary human eosinophils (50,000-400,000 sites/cell) , consistent with the potent ability of eotaxin to selectively influence the migration of these cells.

The mechanisms by which specific cells are attracted by specific chemokines have been a topic of intense interest and clinical relevance. The question is complicated by the fact that a number of closely related chemokine receptors with overlapping specificities are expressed on many different classes of leukocytes. In addition, the affinity of a specific receptor/ligand interaction can vary depending upon the specific cell type expressing the chemokine receptor, perhaps due to posttranslational modification events or G protein coupling. Thus it appears that cells can modulate their responses to chemokines, but how this is done is not yet clear

 

REFERENCES

1. Bousquet, J. P., Chanez, P., Lacoste, J. Y., Barneon, G., Ghavanian, N., Enander, I., Venge, P., Ahlstedt, S., Simony-Lafontaine, J., Godard, P., and Michel, F.-B. (1990) N. Engl. J. Med. 323, 1033-1039 [Abstract]
2. Kay, A. B., and Corrigan, C. J. (1992) Br. Med. Bull. 48, 51-64 [Abstract/Free Full Text]
3. Butterfield, J. H., Leiferman, K. M., and Gleich, G. J. (1994) in Samter’s Immunologic Diseases (Frank, M. M., Austen, K. F., Claman, H. N., and Unanue, E. R., eds), pp. 501-527, Little Brown and Co., Boston, MA
4. Heath, H., Qin, S., Rao, P., Wu, L., LaRosa, G., Kassam, N., Ponath, P. D., and Mackay, C. R. (1997) J. Clin. Invest. 99, 178-184 [Abstract/Free Full Text]
5. Ponath, P. D., S., Qin, S., Post, T. W., Wang, J., Wu, L., Gerard, N. P., Neuman, W., Gerard, C., and Mackay, C. R. (1996) J. Exp. Med. 183, 2437-2488 [Abstract/Free Full Text]
6. Daugherty, B. L., Siciliano, S. J., DeMartino, J. A., Malkowitz, L., Sirotina, A., and Springer, M. S. (1996) J. Exp. Med. 183, 2349-2354 [Abstract/Free Full Text]
7. Kitaura, M., Nakajima, T., Imai, T., Harada, S., Combadiere, C., Tiffany, H. L., Murphy, P. M., and Yoshie, O. (1996) J. Biol. Chem. 271, 7725-7730 [Abstract/Free Full Text]
8. Post, T. W., Bozic, C. R., Rothenberg, M. E., Luster, A. D., Gerard, N. P., and Gerard, C. (1995) J. Immunol. 155, 5299-5305 [Abstract]
9. Jose, P. J., Griffiths-Johnson, D. A., Collins, P. D., Walsh, D. T., Moqbel, R., Totty, N. F., Truong, O., Hsuan, J. J., and Williams, T. J. (1994) J. Exp. Med. 179, 881-887 [Abstract/Free Full Text]
10. Ponath, P. D., Qin, S., Ringler, D. J., Clark-Lewis, I., Wang, J., Kassam, N., Smith, H., Shi, X., Gonzalo, J.-A., Newman, W., Guiterrez-Ramos, J.-C., and Mackay, C. R. (1996) J. Clin. Invest. 97, 604-612 [Abstract/Free Full Text]
11. Garcia-Zepeda, E. A., Rothenberg, M. E., Ownbey, R. T., Celestin, J., Leder, P., and Luster, A. D. (1996) Nat. Med. 2, 449-456 [CrossRef][Medline] [Order article via Infotrieve]
12. Rothenberg, M. E., Luster, A. D., and Leder, P. (1995) Proc. Natl. Acad. Sci. U. S. A. 92, 8960-8964 [Abstract/Free Full Text]
13. Samson, M., Soularue, P., Vassart, G., and Parmentier, M. (1996) Genomics 15, 522-526
14. Bosworth, N., and Towers, P. (1989) Nature 341, 167-168 [CrossRef][Medline] [Order article via Infotrieve]
15. Hansel, T. T., Pound, J. D., Pilling, D., Kitas, G. D., Salomon, M., Gentle, Lee, S. S., and Thompson, R. A. (1989) J. Immunol. Methods 122, 97-103 [CrossRef][Medline] [Order article via Infotrieve]
16. Bacon, K. B., Camp, R. D., Cunningham, F. M., and Woollard, P. (1988) Br. J. Pharmacol. 95, 966-974 [Medline] [Order article via Infotrieve]
17. Helmlinger, G., Yuan, F., Dellian, M., and Jain, R. K. (1997) Nat. Med. 3, 177-182 [CrossRef][Medline] [Order article via Infotrieve]
18. Gleich, G. J., Kita, H., and Adolphson, C. R. (1994) in Samter’s Immunologic Diseases (Frank, M. M., Austen, K. F., Claman, H. N., and Unanue, E. R., eds), pp. 205-245, Little Brown and Co., Boston, MA
19. Raghavan, M., Bonagura, V. R., Morrison, S. L., and Bjorkman, P. J. (1995) Biochemistry 34, 14649-14657 [CrossRef][Medline] [Order article via Infotrieve]
20. French, A. R., Tadaki, D. K., Niyogi, S. K., and Lauffenburger, D. (1995) J. Biol. Chem. 270, 4334-4340 [Abstract/Free Full Text]
21. Bangia, N., Ghumman, B., and Watts, T. H. (1994) Mol. Immunol. 31, 1303-1312 [CrossRef][Medline] [Order article via Infotrieve]
22. Williams, A. J., Michel, A. D., Feniuk, W., and Humphrey, P. P. (1997) Mol. Pharmacol. 51, 1060-1069 [Abstract/Free Full Text]