【作者】 刘曦；

【导师】 王新泉；

【作者基本信息】 清华大学 ， 生物学， 2013， 博士

【摘要】 白细胞介素1（IL-1）是最早被发现和研究的细胞因子之一，对IL-1家族的研究已经有近40年的历史，目前为止，已发现的IL-1家族成员有11个，它们都在调节人体的先天免疫中起到了非常重要的作用。白细胞介素33（IL-33）是IL-1家族中的最新成员，拥有着调节人体先天性免疫和适应性免疫的多种功能。作为细胞因子的IL-33主要通过结合其特异性的受体ST2和共受体IL-1RAcP来向细胞内传递信号。ST2与IL-1RAcP都是IL-1受体家族的成员。IL-33作为配体介导的受体和共受体胞内TIR结构域的异源二聚化，可以有效地激活NF-kB与MAPK信号通路。IL-33不仅可以作为一种细胞因子对免疫系统进行调节，同时也可以作为一种转录调控因子参与到免疫反应当中。研究发现IL-33的成熟机制与其它IL-1家族成员有着很大的不同。这都使得IL-33在IL-1家族中的地位显得尤为特殊。IL-33与其受体的结构和功能研究都取得了一定的进展，但仍存在着很多需要解决的问题。IL-33与其受体的结构生物学研究不仅可以帮助我们了解IL-1家族识别受体的机制，也可以对治疗与IL-33相关的疾病起到帮助。本文通过解析分辨率为3.27的IL-33与ST2胞外域二元复合体的晶体结构，结合突变以及SPR等实验，揭示了ST2特异性识别IL-33的分子机制。同时通过小角度X射线散射（SAXS）的分析结果，验证了IL-33/ST2二元复合体招募IL-1RAcP所利用的机制是与已知的IL-1β/IL-1RII/IL-1RAcP以及IL-1β/IL-1RI/IL-1RAcP晶体结构所展示出相同的”左手”模型。SAXS的分析结果还显示ST2在溶液状态下比IL-1RAcP有着更大的柔性，二元复合体和三元复合体都拥有比较稳定的构象。根据上述的结果我们提出一个IL-1家族蛋白受体识别配体是利用结构域之间的构象变化的新机制，从而也解释了下游的信号通路必须有配体的存在才能被激活以及共受体IL-1RAcP不能单独识别配体的原因。更多还原

【Abstract】 Interleukin-1(IL-1) is the one of earliest discoverd cytokines with a history ofnearly40years. So far, IL-1family has got11members. They are all playingimportant roles in human innate immune.Interleukin33（IL-33） is the latest member of the IL-1family that haspleiotropic activities in innate and adaptive immune responses in immunity and disease.The signaling of IL-33depends on its binding to the primary receptor ST2andsubsequent recruitment of accessory receptor IL-1RAcP, both of which are members ofthe IL-1receptor family. The ligand-binding induced receptor hetero-dimerizationresults in the juxtaposition of the intracellular TIR domains of both receptors, which isnecessary and sufficient to activate NF-κB and MAPK pathways in the target cells.Studies showed that IL-33could not only fuction as a cytokine but also as atranscription factor involved in the immune response. The maturation mechanism ofIL-33is qutie different from the other members, making IL-33a very special one inIL-1family. Some progress has already be made in both functional and structuralstudies of IL-33,while a lot questions are still need to answer.Structural study of IL-33and its receptor could provide both great insight into mechanism of IL-1familycytokines recognition by their receptors and a lot of help to treatment withIL-33-related diseases.Here we present the crystal structure of IL-33in complex with the ectodomain ofST2at a resolution of3.27. With mutagenesis and SPR binding assay, it defines themolecular mechanism by which ST2specifically recognizes IL-33. Small-angle X-rayscattering （SAXS） analysis showed that the architecture of IL-33/ST2recruitingIL-1RAcP to form the ternary complex using a “left” model similar with previouslydetermined IL-1β-IL-1RII-IL-1RAcP and IL-1β-IL-1RI-IL-1RAcP crystal structures.SAXS data also revealed that ST2is much more flexible than IL-1RAcP between theD3domain and “D1D2” module in unbound state in solution. And binary and ternarycomplex in solution both maintain in a single stable comformer, which provides newinsights into domain-level conformational changes of IL-1primary receptors uponligand binding and the inability of IL-1RAcP to bind ligands directly. Our work also showed that why the ligand binding is nessasery for activing signaling through tworeceptors.更多还原