Structural Mimicry of Receptor Interaction by Antagonistic Interleukin-6 (IL-6) Antibodies.
Structural Mimicry of Receptor Interaction by Antagonistic Interleukin-6 (IL-6) Antibodies.
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DOI：
10.1074/jbc.m115.695528
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发表时间：
2016-06-24
期刊：
影响因子：
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通讯作者：
de Haard H
中科院分区：
文献类型：
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作者：
Blanchetot C;De Jonge N;Desmyter A;Ongenae N;Hofman E;Klarenbeek A;Sadi A;Hultberg A;Kretz-Rommel A;Spinelli S;Loris R;Cambillau C;de Haard H
白细胞介素6在介导自身免疫性疾病和癌症中的炎症反应中起关键作用，其中它还参与转移和组织侵袭。针对IL-6及其受体的中和抗体已被批准用于治疗干预或处于临床开发的晚期阶段。在这里，我们描述了IL-6与两个Fab衍生自常规骆驼抗体，拮抗细胞因子和其受体之间的相互作用的复合物的晶体结构。这些复合物的X射线结构提供了对两种抗体的中和机制的见解，并解释了其中一种抗体的非常高的效力。它通过使用两个CDR残基的侧链填充IL-6的位点I空腔，从而模拟IL-6 R的Phe 229和Phe 279的相互作用，有效地与IL-6受体（IL-6 R）竞争结合细胞因子。在第一抗体中，HCDR 3色氨酸类似地结合热点残基Phe 279。该HCDR 3 Trp残基突变成除Tyr或Phe之外的任何其它残基显著削弱抗体与IL-6的结合，如对于Phe 279的IL-6 R突变体也观察到的。在第二种抗体中，HCDR 3缬氨酸的侧链与IL-6 R Phe 279一样连接到位点I，而LCDR 1酪氨酸侧链占据位点I内的第二个空腔并模拟IL-6 R Phe 229的相互作用。
Interleukin 6 plays a key role in mediating inflammatory reactions in autoimmune diseases and cancer, where it is also involved in metastasis and tissue invasion. Neutralizing antibodies against IL-6 and its receptor have been approved for therapeutic intervention or are in advanced stages of clinical development. Here we describe the crystal structures of the complexes of IL-6 with two Fabs derived from conventional camelid antibodies that antagonize the interaction between the cytokine and its receptor. The x-ray structures of these complexes provide insights into the mechanism of neutralization by the two antibodies and explain the very high potency of one of the antibodies. It effectively competes for binding to the cytokine with IL-6 receptor (IL-6R) by using side chains of two CDR residues filling the site I cavities of IL-6, thus mimicking the interactions of Phe229 and Phe279 of IL-6R. In the first antibody, a HCDR3 tryptophan binds similarly to hot spot residue Phe279. Mutation of this HCDR3 Trp residue into any other residue except Tyr or Phe significantly weakens binding of the antibody to IL-6, as was also observed for IL-6R mutants of Phe279. In the second antibody, the side chain of HCDR3 valine ties into site I like IL-6R Phe279, whereas a LCDR1 tyrosine side chain occupies a second cavity within site I and mimics the interactions of IL-6R Phe229.