Structural determinants of MIF functions in CXCR2-mediated inflammatory and atherogenic leukocyte recruitment
Structural determinants of MIF functions in CXCR2-mediated inflammatory and atherogenic leukocyte recruitment
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DOI：
10.1073/pnas.0804017105
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发表时间：
2008-10-21
影响因子：
11.1
通讯作者：
Bernhagen, Juergen
中科院分区：
文献类型：
--
作者：
Weber, Christian;Kraemer, Sandra;Bernhagen, Juergen
我们最近发现了古老的细胞因子巨噬细胞移动抑制因子(MIF)，它是CXC趋化因子受体CXCR2和CXCR4在炎症和动脉粥样硬化细胞募集中的非典型配体。由于MIF对CXCR2的亲和力特别高，我们推测MIF可能具有典型CXCR2配体共有的结构动机，即保守的N-末端Glu-Leu-Arg(ELR)基序。序列比对和结构建模确实揭示了一个伪(E)LR基序(Asp-44-X-Arg-11)，该基序由相邻环中不相邻的残基组成，但平行间距与真正的ELR基序相同。结构-功能分析表明，R11、D44残基的突变保留了MIF的正确折叠和固有的催化特性，但严重损害了其与CXCR2的结合，并取消了MIF/CXCR2介导的趋化功能和血流条件下单核细胞对内皮的抑制作用。R11A-MIF和R11A/D44A-MIF双突变体在体外灌流和应用于腹膜炎模型时，在触发白细胞向早期动脉粥样硬化内皮细胞募集方面存在明显缺陷。代偿使用CXCR4后，D44A-MIF在腹膜白细胞募集中的作用得以保留。此外，我们的数据确定伪(E)LR基序是MIF作为非规范CXCR2配体活性的结构决定因素，这体现了趋化素样配体与趋化因子的结构相似，并使选择性靶向促炎MIF/CXCR2相互作用成为可能。
We have recently identified the archaic cytokine macrophage migration inhibitory factor (MIF) as a non-canonical ligand of the CXC chemokine receptors CXCR2 and CXCR4 in inflammatory and atherogenic cell recruitment. Because its affinity for CXCR2 was particularly high, we hypothesized that MIF may feature structural motives shared by canonical CXCR2 ligands, namely the conserved N-terminal Glu-Leu-Arg (ELR) motif. Sequence alignment and structural modeling indeed revealed a pseudo-(E)LR motif (Asp-44-X-Arg-11) constituted by non-adjacent residues in neighboring loops but with identical parallel spacing as in the authentic ELR motif. Structure-function analysis demonstrated that mutation of residues R11, D44, or both preserve proper folding and the intrinsic catalytic property of MIF but severely compromises its binding to CXCR2 and abrogates MIF/CXCR2-mediated functions in chemotaxis and arrest of monocytes on endothelium under flow conditions. R11A-MIF and the R11A/D44A-MIF double-mutant exhibited a pronounced defect in triggering leukocyte recruitment to early atherosclerotic endothelium in carotid arteries perfused ex vivo and upon application in a peritonitis model. The function of D44A-MIF in peritoneal leukocyte recruitment was preserved as a result of compensatory use of CXCR4. In conjunction, our data identify a pseudo-(E)LR motif as the structural determinant for MIF's activity as a non-canonical CXCR2 ligand, epitomizing the structural resemblance of chemokine-like ligands with chemokines and enabling selective targeting of pro-inflammatory MIF/CXCR2 interactions.