Youn B S, Yu K Y, Alkhatib G, Kwon B S
Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, Indiana, 46202
Biochem Biophys Res Commun. 2001 Mar 2;281(3):627-33. doi: 10.1006/bbrc.2001.4393.
CC chemokine receptor 5 (CCR5) is a high-affinity receptor for macrophage inflammatory protein (MIP)-1beta and functions as the major coreceptor for entry of macrophage-tropic (M-tropic) human immunodeficiency virus type 1 (HIV-1). To evaluate the role of transmembrane domains (TM) in the receptor function of CCR5, the seventh transmembrane domain (TM7) was examined in a series of chimeric receptor constructs including CCR5TM (CCR5 backbone/CCR5 TM7 replaced with CCR1 TM7) and mutants of CCR5TM. The CCR5TM chimera exhibited a dramatic reduction in receptor activation, as well as little or no MIP-1beta binding. Further mutational analysis revealed that Met 287 in TM7 of CCR5 is a critical molecular determinant for both MIP-1beta binding and receptor activation. Interestingly, all of the chimeric/mutated receptors were biologically active in an HIV-1 coreceptor fusion assay, demonstrating that chemokine binding is independent of HIV-1 coreceptor activity.
C-C趋化因子受体5（CCR5）是巨噬细胞炎性蛋白（MIP）-1β的高亲和力受体，并且作为嗜巨噬细胞性1型人类免疫缺陷病毒（HIV-1）进入的主要共受体发挥作用。为了评估跨膜结构域（TM）在CCR5受体功能中的作用，在一系列嵌合受体构建体中检测了第七个跨膜结构域（TM7），这些构建体包括CCR5TM（CCR5骨架/用CCR1 TM7替换CCR5 TM7）和CCR5TM的突变体。CCR5TM嵌合体在受体激活方面表现出显著降低，并且MIP-1β结合很少或没有。进一步的突变分析表明，CCR5的TM7中的甲硫氨酸287是MIP-1β结合和受体激活的关键分子决定因素。有趣的是，所有嵌合/突变受体在HIV-1共受体融合试验中均具有生物学活性，表明趋化因子结合与HIV-1共受体活性无关。
