Mediators and Mechanisms of Innate Immunity in the Lung

描述（由申请人提供）：C5L2是一种神秘的蛇形受体，与C5a受体在包括PMN中性粒细胞在内的许多细胞类型上共表达。C5L2与G蛋白的偶联缺失以及我们的初步数据表明，该受体不像经典的C5a受体那样转导信号，而是可能调节C5a的生物活性。体内研究支持C5L2作为诱饵受体的概念。或者，它可以通过分子间复合物的形成(例如；（异二聚体）与C5aR。C5L2也可能存在不同的信号传导机制。C5L2靶向缺失小鼠C5a/C5adesArg的生物活性增强。因此，C5L2的生物学功能似乎是利用上述一种或多种机制限制对过敏毒素的促炎反应。因此，C5L2的上调可能在C5a驱动的炎症状态中有益，可能在败血症、哮喘、囊性纤维化和慢性阻塞性肺疾病中。C5L2的其他潜在作用包括上调抗炎神经内分泌轴，调节甘油三酯合成和干细胞归巢到骨髓。我们在小鼠中创建的工具将允许证明或拒绝由C5L2介导的这些反应。在目前的更新应用中，我们提出通过以下具体目的来表征C5L2与其配体C5a和C5adeSArg的功能相互作用，以及它与经典C5a受体的关系：1)我们将表征C5L2-/-小鼠在幼稚状态、免疫复合物损伤、感染性休克和Th1/Th2炎症模型中的表型。我们将进一步研究C5L2在甘油三酯合成和肾上腺皮质轴调节中的作用。2)我们将生成C5L2在肺中过表达的小鼠，以及人类C5aR代替小鼠CSaR表达的小鼠，从而允许受体拮抗剂对C5aR进行药物阻断。这些动物将用于评价C5L2在免疫复合物损伤和感染性休克中的抗炎作用。3)我们将确定C5L2作为C5a结合蛋白的结构。最后，我们将研究C5a/C5adeSArg与C5L2结合介导的潜在替代信号传导机制。本研究项目的成功完成将增加我们对急性和慢性肺损伤的相关知识。这些疾病的潜在治疗方案可以通过受此提议启发的转化研究而出现。

DESCRIPTION (provided by applicant): C5L2 is an enigmatic serpentine receptor that is co-expressed with the C5a receptor on many cell types including PMN neutrophils. The absence of coupling of C5L2 to G proteins, as well as our preliminary data, suggest that this receptor does not transduce signals like the classical C5a receptor, but may instead modulate the biological activity of C5a. In vivo studies support the concept that C5L2 acts as a decoy receptor. Alternatively, it may affect function through formation of intermolecular complexes (eg., heterodimers) with the C5aR. A distinct signaling mechanism may also exist for C5L2. Mice bearing a targeted deletion of C5L2 exhibit enhanced biological activity of C5a/C5adesArg. Thus, the biological function of C5L2 appears to be to limit the proinflammatory response to the anaphylatoxin utilizing one or more of the mechanisms described above. Accordingly, up-regulation of C5L2 may be of benefit in inflammatory states driven by C5a, potentially in sepsis, asthma, cystic fibrosis and chronic obstructive lung disease. Other potential actions of C5L2 that have been proposed include up-regulation of the anti- inflammatory neuroendocrine axis, regulation of triglyceride synthesis, and homing of stem cells to bone marrow. The tools we have created in the mouse will allow for proof or rejection of these responses as mediated by C5L2. In the current renewal application, we propose to characterize the functional interactions of C5L2 with its ligands, C5a and C5adeSArg, and its relationship with the classical C5a receptor through the following Specific Aims: 1) we will characterize the phenotype of C5L2-/- mice in the naive state, in models of immune complex injury, septic shock, and Th1/Th2 inflammation. We will further investigate the role of C5L2 in triglyceride synthesis and regulation of the adrenocortical axis. 2) We will generate mice in which C5L2 is over-expressed in the lung, and mice in which human C5aR is expressed in place of murine CSaR, allowing pharmacological blockade of the C5aR with receptor antagonists. These animals will be used to evaluate the anti-inflammatory actions of C5L2 in immune complex injury and septic shock. 3) We will determine the structure of C5L2 as a C5a binding protein. Finally, 4) we will examine potential alternative signaling mechanisms mediated by binding of C5a/C5adeSArg to C5L2. Successful completion of this research program will increase our knowledge relevant to acute and chronic lung injury. Potential treatment options for these diseases could arise through translational research inspired by this proposal.