Distinct Structural Requirements for Interleukin-4 (IL-4) and IL-13 Binding to the Shared IL-13 Receptor Facilitate Cellular Tuning of Cytokine Responsiveness
Distinct Structural Requirements for Interleukin-4 (IL-4) and IL-13 Binding to the Shared IL-13 Receptor Facilitate Cellular Tuning of Cytokine Responsiveness
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DOI：
10.1074/jbc.m109.007286
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发表时间：
2009-09-04
影响因子：
4.8
通讯作者：
Izuhara, Kenji
中科院分区：
文献类型：
--
作者：
Ito, Takachika;Suzuki, Shoichi;Izuhara, Kenji
白介素4(IL-4)和白介素13(IL-13)都可以与由IL-4受体α链和IL-13受体α1链(IL-13Rα1)组成的共同受体结合，但这些配体与受体链结合的机制不同，导致这些配体的主要功能也不同。我们先前已经证明，IL-13Rα1中的N-末端Ig样结构域，称为D1结构域，是IL-13特异和关键的结合单位。然而，目前还不清楚哪些氨基酸与IL-13有特异的结合能力，以及为什么D1结构域是IL-13的结合部位，而不是IL-4的结合部位。为了解决这些问题，在本研究中，我们对D1结构域进行了突变分析，结合结构数据来确定与IL-13结合的关键氨基酸。晶体结构与IL-13相互作用的c‘链上的Lys-76、Lys-77或Ile-78以及邻近相互作用部位的Trp-65和Ala-79突变导致IL-13结合的显著损伤，表明这些氨基酸产生了结合部位。此外，N-末端β链上的Val-35、Leu-38或Val-42的突变也导致IL-13结合的丢失，可能是由于结构稳定性降低。这里使用的突变都没有影响IL-4的结合。这些结果表明，IL-13Rα1的D1域通过直接的细胞因子相互作用起到亲和力转换的作用，允许共享的受体对IL-4和IL-13做出不同的反应。
Both interleukin-4 (IL-4) and IL-13 can bind to the shared receptor composed of the IL-4 receptor alpha chain and the IL-13 receptor alpha 1 chain (IL-13R alpha 1); however, the mechanisms by which these ligands bind to the receptor chains are different, enabling the principal functions of these ligands to be different. We have previously shown that the N-terminal Ig-like domain in IL-13R alpha 1, called the D1 domain, is the specific and critical binding unit for IL-13. However, it has still remained obscure which amino acid has specific binding capacity to IL-13 and why the D1 domain acts as the binding site for IL-13, but not IL-4. To address these questions, in this study we performed mutational analyses for the D1 domain, combining the structural data to identify the amino acids critical for binding to IL-13. Mutations of Lys-76, Lys-77, or Ile-78 in c' strand in which the crystal structure showed interaction with IL-13, and those of Trp-65 and Ala-79 adjacent to the interacting site, resulted in significant impairment of IL-13 binding, demonstrating that these amino acids generate the binding site. Furthermore, mutations of Val-35, Leu-38, or Val-42 at the N-terminal beta-strand also resulted in loss of IL-13 binding, probably from decreased structural stability. None of the mutations employed here affected IL-4 binding. These results demonstrate that the D1 domain of IL-13R alpha 1 acts as an affinity converter, through direct cytokine interactions, that allows the shared receptor to respond differentially to IL-4 and IL-13.