GPI-LU亚家族蛋白的结构研究

Ly-6/uPAR（LU）结构域家族成员是二硫键保守的三指状蛋白。含GPI锚的GPI-LU亚家族成员主要在细胞黏连和信号传导方面起作用，与人类疾病紧密相关。由于蛋白后翻译修饰的复杂性及结构的灵活性，这类蛋白的X射线结构测定比较困难，目前关于这类蛋白的结构研究尚少。作为无胞内结构域的蛋白，它们如何通过二聚体介导胞外信号的传导？它们如何与配体相互作用、这种相互作用是否诱导GPI-LU的构象变化？这些问题都有待结构信息进行解决。本申请拟研究这类蛋白中C4.4A、LYPD4、TEX101、Haldisin和CD177的原子水平结构、CD59和uPAR的同源二聚体结构，及CD177与配体的复合物结构。本申请将有助于深入了解这类蛋白发挥功能的分子基础，为以这类蛋白为靶点的药物设计提供理论支持。目前，我们已解析了uPAR二聚体的晶体结构，并获得了C4.4A的晶体，以上工作为本项目的顺利完成奠定了基础。

Ly-6/uPAR (LU) domain is also named three-fingered domain based on its topology and is highly conserved in its disulfide bonding pattern. Glycophosphatidylinositol (GPI)-anchored LU domain-containing cell receptors play important roles in cell adhesion and signaling. The structural information of this family is scarce due to the protein complexity from post-translational modifications and the structural flexibility, which poses challenges for structural biology study. It is not fully understood how do the LU-domains connect to each other, how the receptors mediate signaling through their dimerization, and how do the receptors interact with their ligands. This application proposes to determine the structures of a number of GPI-LU ectodomains: C4.4A, LYPD4, TEX101 and CD177, the complex between CD177 and its ligand, and the homodimers of CD59 and uPAR. As the preliminary results, the applicant has determined the structure of uPAR dimer and obtained the crystals of C4.4A, laying out a foundation for the success of this proposal.