Structural Studies of Leukocyte Integrin Interactions

项目总结(见说明)： 这项名为《白细胞整合素相互作用的结构研究》的提议旨在从原子分辨率上理解白细胞整合素Mac-1和axb2通过aI结构域与不同配体相互作用的机制。主要的焦点将是Mac-1如何结合非常不同类别的配体来执行其关键的生物学功能。在NIH基金的支持下，在与斯普林格博士的持续合作中，我们有 成功地确定了白细胞整合素LFA-1与ICAM家族相互作用的结构基础。我们现在将把精力转向Mac-1。尽管Mac-1属于同一个白细胞整合素家族，但在结构和功能上都不同于LFA-1。Mac-1表达在中性粒细胞和其他髓系细胞上，与非常不同的配体结合不仅以不同于LFA-1的方式介导白细胞的募集，而且 还能促进炎症过程中的吞噬作用和清除凋亡细胞。我们将研究Mac-1‘S与ICAM-1的相互作用，并将其与LFA-1/ICAM相互作用进行比较，以探讨它们与ICAM-1在白细胞募集中的顺序作用。我们将研究Mac-1(以及AX(32))与补体成分iC3b的相互作用，iC3b是促进中性粒细胞吞噬病原体的主要调理素。我们将研究Mac-1与内皮分泌的细胞外基质配体Del-1的相互作用，Del-1是建议的凋亡细胞和吞噬细胞之间的桥梁。我们将采用几个亲和力增强的Mac-1i域 这些配体的Mac-1结合域的结构研究的突变体。我们将检验这一假设，即与相对平坦的结合界面LFA-1相关者相比，Mac-1‘S配体可能有其突出的环来结合“颠簸”的Mac-1I结构域。我们将对与整合素结合的含有RGD的配体进行比较，其中有没有I结构域。对Mac-1表面杂乱结合能力的研究将为探索治疗许多相关疾病奠定良好的基础。

PROJECT SUMMARY (See instructions): This proposal, entitled "Structural studies of leukocyte integrin interactions", aims to understand, at atomic resolution, the mechanism by which leukocyte Integrins, Mac-1 and aXB2, interact with diverse ligands via the a I domains. The major focus will be how Mac-1 binds ligands of very different categories to perform its crucial biological functions. Supported by NIH funds, in a continuous collaboration with Dr. Springer, we have successfully defined the structural basis of leukocyte integrin LFA-1 interaction with the ICAM family. We now will turn our efforts to Mac-1. Despite belonging to the same leukocyte integrin family, structurally and functionally Mac-1 is distinct from LFA-1. Expressed on neutrophils and other myeloid cells, Mac-1 binding to very diverse ligands not only mediates the leukocytes recruitment in a differential fashion from LFA-1, but also facilitates phagocytosis during inflammation and the clearance of apoptotic cells. We will study Mac-1's interaction with ICAM-1, and compare it with LFA-1/ICAM interactions to investigate their sequential engagement of ICAM-1 for leukocyte recruitment. We will study Mac-1 (and also aX(32) interactions with complement component, iC3b, the major opsonin in facilitating pathogen phagocytosis by neutrophils. We will study Mac-1 interactions with the endothelium-secreted extracellular matrix ligand, Del-1, the suggested bridge between apoptotic cells and phagocytes. We will employ several affinity-enhanced Mac-1 I domain mutants for the structural studies with these ligands' Mac-1-binding domains. We will test the hypothesis that compared to relatively flat binding interface LFA-1 associates, Mac-1's ligands may have their protruding loops to bind "bumpier" Mac-1 I domain. We will perform comparison of RGD-containing ligands bound to integrins with and without I domain. The investigation on the seemingly promiscuous binding ability of Mac-1 will lay a good foundation for therapeutic exploration to treat many relevant diseases.