Macrophage inflammasome regulation

描述(由申请人提供)：最近发现的独特的细胞内病原体识别受体可以检测进入巨噬细胞胞浆的危险信号，从而加强了先天免疫在肺防御外部挑战中的重要性。这些受体包括NOD样受体(NLRs)以及NOD非依赖性感受器，如吡喃。细胞内传感器的一个关键功能是通过炎症体复合体调节caspase-1酶。在炎症体中，NLR和节点非依赖的感受器通过比林结构域(PYD)或半胱氨酸酶招募结构域(CARD)与接头蛋白ASC相互作用，诱导caspase-1二聚化和自我激活。然后，caspase-1裂解并激活IL-1和IL-18的前体，这两个分子与哮喘、ARDS、肺炎和肺纤维化密切相关。然而，尽管在概念上取得了进展，但这种炎症体复合体如何在物理上与IL-1的处理和释放联系在一起仍然不清楚，这限制了我们对肺部炎症的理解和我们创造新疗法的能力。在此背景下，本申请试图通过将其结构和功能与促进无领导蛋白IL-1的释放的机制联系起来来扩展炎症体假说。我们提出了一种新的结构，释放体。我们推测，这种新的外体结构将proIL-1和炎症体成分一起包裹在肌动蛋白细丝调节的囊泡中。PYRIN和ASC是已知的肌动蛋白结合蛋白。因此，在这个模型中，微泡IL-1以高度浓缩的形式递送到靶细胞膜(如肺成纤维细胞或上皮细胞)，其次级胞吐可由调节局部浓度的ATP(一种经典的炎症体激活因子)的靶细胞受体控制。该项目建议检验以下特定假设：1)IL-1？主要从外切体释放；2)靶细胞诱导的这些外切体的断裂提供了一种集中IL-1？活性的机制；3)吡喃和ASC的相互作用调节caspase-1的外包装以供释放；以及4)肌动蛋白与ProIL-1的相互作用是外体炎症小体proIL-1相互作用的关键。如果得到证实，这些新的假设将改变我们对IL-1调节的概念，并为炎症性肺部疾病提供新的治疗选择。

DESCRIPTION (provided by applicant): Innate immunity's importance in lung defense against external challenges has been heightened by the recent discovery of distinct intracellular pathogen recognition receptors that detect danger signals that gain access to the cytosol of macrophages. These receptors include NOD-like receptors (NLRs) as well as NOD independent sensors such as pyrin. A critical function of the intracellular sensors is to regulate the enzyme caspase-1 through an inflammasome complex. In an inflammasome, NLRs and NOD-independent sensors interact, via pyrin domains (PYD) or caspase recruitment domains (CARD), with an adaptor protein, ASC, to induce caspase-1 dimerization and autoactivation. Caspase-1 then cleaves and activates the precursors of IL-1¿ and IL-18, molecules that have been strongly associated with asthma, ARDS, pneumonia and pulmonary fibrosis. However, despite this conceptual advance, it remains obscure how this inflammasome complex is physically linked to IL-1¿ processing and release, limiting our understanding of lung inflammation and our ability to create new therapies. In this context, the present application seeks to expand upon the inflammasome hypothesis by linking its structure and function to the mechanisms that promote the release of the leaderless protein IL-1¿. We propose a novel structure, the releasosome. We hypothesize that this novel exosomal structure encapsulates proIL-1¿ together with inflammasome components in an actin filament regulated vesicle. Pyrin and ASC are known actin binding proteins. Thus, in this model, microvesicular IL-1¿ is presented to target cell membranes (e.g. lung fibroblasts or epithelium) in a highly concentrated packet where its secondary exocytosis can be controlled by target cell receptors that modulate local concentrations of ATP (a classical inflammasome activating factor). The project proposes to test the following specific hypotheses, 1) IL-1¿ release is predominantly from exosomes; 2) the target cell induced rupture of these exosomes provides a mechanism to focus IL-1¿ activity; 3) pyrin and ASC interactions modulate the exosomal packaging of caspase-1 for release; and 4) actin interactions with proIL-1¿ are critical to exosomal inflammasome proIL-1¿ interaction. If confirmed, these novel hypotheses will change our concepts about IL-1¿ regulation and provide new treatment options for inflammatory lung disorders.