Molecular Cloning and Functional Expression of a Novel CC Chemokine Receptor cDNA from a Human Basophilic Cell Line

Abstract

We report the cloning and characterization of a novel basophil CC chemokine receptor, K5-5, from the human immature basophilic cell line KU-812. The predicted protein sequence of K5-5 shows only 49% identity to the macrophage inflammatory protein-1α/RANTES receptor (CC CKR-1) and 47% identity to monocyte chemotactic protein-1 receptor (b form), suggesting that this cDNA encodes a novel member of the CC chemokine receptor family. Analysis of K5-5 mRNA expression indicates that it is restricted to leukocyte-rich tissues. In addition, we have shown significant levels of K5-5 mRNA in human basophils, which were up-regulated by treatment with interleukin-5. The CC chemokines, macrophage inflammatory protein-1α, RANTES, and monocyte chemotactic protein-1 were able to stimulate a Ca2+-activated chloride channel in Xenopus laevis oocytes injected with K5-5 cRNA, whereas no signal was detected in response to monocyte chemotactic protein-2, macrophage inflammatory protein-1β, or the CXC chemokine, interleukin-8. Taken together, these results indicate for the first time the presence of a CC chemokine receptor on basophils, which functions as a “shared” CC chemokine receptor and may therefore be implicated in the pathogenesis of basophil-mediated allergic diseases. We report the cloning and characterization of a novel basophil CC chemokine receptor, K5-5, from the human immature basophilic cell line KU-812. The predicted protein sequence of K5-5 shows only 49% identity to the macrophage inflammatory protein-1α/RANTES receptor (CC CKR-1) and 47% identity to monocyte chemotactic protein-1 receptor (b form), suggesting that this cDNA encodes a novel member of the CC chemokine receptor family. Analysis of K5-5 mRNA expression indicates that it is restricted to leukocyte-rich tissues. In addition, we have shown significant levels of K5-5 mRNA in human basophils, which were up-regulated by treatment with interleukin-5. The CC chemokines, macrophage inflammatory protein-1α, RANTES, and monocyte chemotactic protein-1 were able to stimulate a Ca2+-activated chloride channel in Xenopus laevis oocytes injected with K5-5 cRNA, whereas no signal was detected in response to monocyte chemotactic protein-2, macrophage inflammatory protein-1β, or the CXC chemokine, interleukin-8. Taken together, these results indicate for the first time the presence of a CC chemokine receptor on basophils, which functions as a “shared” CC chemokine receptor and may therefore be implicated in the pathogenesis of basophil-mediated allergic diseases.