Lu Z H, Wang Z X, Horuk R, Hesselgesser J, Lou Y C, Hadley T J, Peiper S C
Department of Pathology, Henry Vogt Cancer Research Institute, University of Louisville, Kentucky 40292, USA.
J Biol Chem. 1995 Nov 3;270(44):26239-45. doi: 10.1074/jbc.270.44.26239.
The Duffy antigen (DARC) is a promiscuous chemokine receptor that also binds Plasmodium vivax. DARC belongs to a family of heptahelical chemokine receptors that includes specific (IL-8RA) and shared (IL-8RB) IL-8 receptors. Ligand binding specificity of IL-8 receptors was localized to the amino-terminal extracellular (E1) domain. To determine the basis for promiscuous chemokine binding by DARC, a chimeric receptor composed of the E1 domain of DARC and hydrophobic helices and loops from IL-8RB (DARCe1/IL-8RB) was constructed. Scatchard analysis of stable transfectants demonstrated that the DARCe1/IL-8RB chimeric receptor bound IL-8 and melanoma growth stimulating activity (MGSA) with KD values almost identical to the native receptors. The hybrid receptor also bound RANTES, MCP-1, and MGSA-E6A (which binds DARC, but not IL-8RB), but not MIP-1 alpha, similarly to DARC. Ligand binding to DARC transfectants was unaltered by anti-Fy3, but inhibited by Fy6, which binds an epitope in the E1 domain. The epitope recognized by Fy3 was localized to the third extracellular loop by analysis of insect cells expressing chimeric receptors composed of complementary portions of DARC and IL-8RB. These findings implicate the E1 domain of DARC in multispecific chemokine binding.
达菲抗原（DARC）是一种杂乱的趋化因子受体，它也能结合间日疟原虫。DARC属于七螺旋趋化因子受体家族，该家族包括特异性的（IL-8RA）和共享的（IL-8RB）IL-8受体。IL-8受体的配体结合特异性定位于氨基末端细胞外（E1）结构域。为了确定DARC杂乱结合趋化因子的基础，构建了一种嵌合受体，其由DARC的E1结构域以及来自IL-8RB的疏水螺旋和环组成（DARCe1/IL-8RB）。对稳定转染子的Scatchard分析表明，DARCe1/IL-8RB嵌合受体结合IL-8和黑色素瘤生长刺激活性（MGSA）的KD值与天然受体几乎相同。该杂合受体也结合RANTES、MCP-1和MGSA-E6A（其结合DARC，但不结合IL-8RB），但不结合MIP-1α，这与DARC类似。抗Fy3不改变配体与DARC转染子的结合，但Fy6可抑制这种结合，Fy6结合E1结构域中的一个表位。通过分析表达由DARC和IL-8RB的互补部分组成的嵌合受体的昆虫细胞，确定Fy3识别的表位定位于第三个细胞外环。这些发现表明DARC的E1结构域参与多特异性趋化因子结合。
