Role of DAF in the Complement Cascade

说明(申请人提供)：衰变加速因子(DAF)是一种70 kDa的固有膜调节因子，可保护自身细胞免受自体补体介导的损伤。它通过衰减C3中央转换酶(C4b2a和C3bBb)来发挥作用，这一过程决定了补体激活是中止还是继续。通过前期的诱变研究和核磁共振结构分析，我们初步定位了DAF的活性部位(S)。在其他工作中，我们准备了DAF基因敲除小鼠，并开始表征DAF在不同自身免疫/炎症状态下的生理重要性。 我们提出的研究旨在为有关DAF功能的几个悬而未决的问题提供见解。目的1精确描述DAF与C3转换酶的界面，并确定其分子作用机制。这不仅为理解DAF的功能提供了基础，也为解开其他C3转换酶调控因子的作用提供了基础。目的2进一步阐明DAF在体内的整体生理功能。这将为一些疾病的发病机制提供重要的见解，并为免疫调节和免疫效应功能提供新的信息。目的3)研究控制DAF及其他内源性调控因子表达水平的转录机制，以及将外源重组DAF衍生物靶向体内特定部位。后一项工作不仅与自身免疫/炎症性疾病有关，而且可能与肿瘤有关。关于通过转录机制对蛋白质表达水平进行药物调控的新发现，可能会为新的治疗方法开辟道路。

DESCRIPTION (provided by applicant): Decay accelerating factor (DAF) is a 70 kDa intrinsic membrane regulator that protects self cells from autologous complement-mediated injury. It functions by decaying the C3 central convertases (C4b2a and C3bBb), a process which determines whether complement activation aborts or proceeds. Through previous mutagenesis studies and NMR structural analyses, we have provisionally mapped DAF's active site(s). In other work, we have prepared Daf knockout mice and have begun to characterize DAF's physiological importance in different autoimmune/inflammatory states. Our proposed research is designed to provide insights into several unresolved questions concerning DAF's function. Aim 1 focuses on precisely characterizing DAF's interface with the C3 convertases and defining its molecular mechanism of action. This should provide a basis not only for understanding DAF's function but for unraveling the actions of other C3 convertase regulators. Aim 2 focuses on further clarifying DAF's overall physiological function in vivo. This should shed important insights into the pathogeneses of a number of disorders as well as new information on immune regulation and immune effector function. Aim 3 focuses on a) characterizing the transcriptional mechanisms controlling expression levels of DAF and other intrinsic regulators and b) targeting exogenous recombinant DAF derivatives to specific sites in vivo. This latter work is relevant not only to autoimmune/inflammatory disorders but potentially also to neoplasia. New findings concerning pharmacological manipulation of the proteins' expression levels via transcriptional mechanisms could open the way to new approaches to therapy.