The exon-3-encoded domain of IL-15Rα contributes to IL-15 high-affinity binding and is crucial for the IL-15 antagonistic effect of soluble IL-15Rα
The exon-3-encoded domain of IL-15Rα contributes to IL-15 high-affinity binding and is crucial for the IL-15 antagonistic effect of soluble IL-15Rα
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DOI：
10.1016/j.jmb.2008.07.019
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发表时间：
2008-09-26
影响因子：
5.6
通讯作者：
Plet, Ariane
中科院分区：
文献类型：
--
作者：
Bouchaud, Gregory;Garrigue-Antar, Laure;Plet, Ariane
我们先前表明，对应于IL-15 R α的全长胞外域的天然可溶形式的白细胞介素-15（IL-15）R α表现为IL-15作用的有效拮抗剂，而重组可溶性IL-15 R α sushi结构域不表现为IL-15作用，而是通过IL-15 R β/γ作为IL-15作用的所有激动剂。为了精确地确定这些拮抗与激动作用的分子基础，我们比较了含有sushi结构域和胞外域不同剩余部分的重组可溶性IL-15 R α（sIL-15 R α）物质的结合特性和生物学效应。我们首先证明，外显子3编码的结构域，更具体地说，其N-末端13个氨基酸（aa）肽是重要的，除了相邻的外显子2编码的寿司结构域，通过减慢其解离速率和约10-20%的相互作用的自由能的高亲和力IL-15.IL-15 R α复合物的稳定。我们接下来表明，所有含sushi的sIL-15 R α都是IL-15 R β/γ的激动剂，协同增加IL-15结合和IL-15诱导的增殖。它们的激动效力与它们各自对IL-15的亲和力成比例。然后，我们表明，在IL-15 R α/β/γ的背景下，sIL-15 R α的拮抗作用是由于1.3-aa肽产生空间限制，阻碍sIL-15 R α.IL-15复合物与膜锚定的IL-15 R α/β/γ结合。在含有13-aa肽的可溶性IL-15 R α sushi结构域-IL-15融合蛋白的框架中，由于13-aa肽与IL-15的N-末端的共价连接而产生的构象效应，这种限制得以缓解。因此，可溶性IL-15 Ra sushi结构域-IL-15融合蛋白能够结合并激活IL-15 R β/γ和IL-15 R α/β/γ受体。(C)2008爱思唯尔有限公司保留所有权利。
We previously showed that a natural soluble form of interleukin-15 (IL-15) R alpha corresponding to the full-length ectodomain of IL-15R alpha behaved as a potent antagonist of IL-15 action through whereas a recombinant soluble IL-15R alpha sushi domain did not, but instead acted as all agonist of IL-15 action through IL-15R beta/gamma. In order to determine precisely the molecular basis governing these antagonistic versus agonistic actions, we compared the binding properties and biological effects of recombinant Soluble IL-15R alpha (sIL-15R alpha) species containing the sushi domain and different remaining parts of the ectodomain. We first demonstrate that the exon-3-encoded domain and, more particularly, its N-terminal 13-amino-acid (aa) peptide are important, in addition to the adjacent exon-2-encoded sushi domain, for the stabilization of the high-affinity IL-15.IL-15R alpha complex by slowing down its dissociation rate and by contributing to about 10-20% of the free energy of interaction. We next show that all sushi-containing sIL-15R alpha are agonists on IL-15R beta/gamma, coordinately increasing IL-15 binding and IL-15-induced proliferation. Their agonistic potencies are proportional to their respective affinities for IL-15. We then show that the antagonistic effect of sIL-15R alpha in the context of IL-15R alpha/beta/gamma is due to the 1.3-aa peptide that creates a sterical constraint impeding the binding of the sIL-15R alpha.IL-15 complex to the membrane-anchored IL-15R alpha/beta/gamma. In the frame of the soluble IL-15R alpha sushi domain-IL-15 fusion protein that contains the 13-aa peptide, this constraint is alleviated as a result of a conformational effect due to the covalent]inking of the 13-aa peptide to the N-terminus of IL-15. The soluble IL-15Ra sushi domain-IL-15 fusion protein is therefore able to bind and activate both the IL-15R beta/gamma and the IL-15R alpha/beta/gamma receptors. (C) 2008 Elsevier Ltd. All rights reserved.