Role of the first extracellular loop in the functional activation of CCR2 - The first extracellular loop contains distinct domains necessary for both agonist binding and transmembrane signaling
Role of the first extracellular loop in the functional activation of CCR2 - The first extracellular loop contains distinct domains necessary for both agonist binding and transmembrane signaling
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DOI：
10.1074/jbc.274.45.32055
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发表时间：
1999-11-05
影响因子：
4.8
通讯作者：
Quehenberger, O
中科院分区：
文献类型：
--
作者：
Han, KH;Green, SR;Quehenberger, O
对单核细胞趋化蛋白-1 (MCP-1) 的生理细胞反应是通过与 CCR2 的特异性结合介导的，单核白细胞的一种有效趋化和激活因子。本研究的目的是鉴定参与高亲和力激动剂结合和受体激活的受体微结构域。我们的功能研究的结果，其中我们利用了针对 CCR2 的中和抗血清 与其他人之前提出的多域绑定模型一致。第一个细胞外环特别令人感兴趣，因为除了配体结合域之外，它还包含受体激活的信息，这对于跨膜信号传导至关重要。用 CCR1 的相应区域替换 CCR2 的第一个胞外环，使 MCP-1 结合亲和力降低约 10 倍，并阻止跨膜信号传导。通过定点诱变进行的更详细的分析表明，该受体片段包含两个不同的微结构域。氨基酸残基 Asn(104) 和 Glu(105) 是。对于高亲和力激动剂结合至关重要，但不参与受体激活。相比之下，带电荷的氨基酸残基 His(100) 对配体结合没有贡献，但对于受体激活和跨膜信号传导至关重要；我们假设激动剂与该残基的相互作用启动构象转换，从而形成功能性 CCR2-G 蛋白复合物。
The physiological cellular responses to monocyte che moattractant protein-1 (MCP-1), a potent chemotactic and activating factor for mononuclear leukocytes, are mediated by specific binding to CCR2, The aim of this investigation is to identify receptor microdomains that are involved in high affinity agonist binding and receptor activation, The results from our functional studies in which we utilized neutralizing antisera against CCR2 are consistent with a multidomain binding model, previously proposed by others. The first extracellular loop was of particular interest, because in addition to a ligand-binding domain it contained also information for receptor activation, crucial for transmembrane signaling. Replacement of the first extracellular loop of CCR2 with the corresponding region of CCR1 decreased the MCP-1 binding affinity about 10-fold and prevented transmembrane signaling. A more detailed analysis by site directed mutagenesis revealed that this receptor segment contains two distinct microdomains. The amino acid residues Asn(104) and Glu(105) are. essential for high affinity agonist binding but are not involved in receptor activation. In contrast, the charged amino acid residue His(100) does not contribute to ligand binding but is vital for receptor activation and initiation of transmembrane signaling; We hypothesize that the interaction of agonist with this residue initiates the conformational switch that allows the formation of the functional CCR2-G protein complex.