Mechanism of Nlrp3 inflammasome activation by mitochondrial dysfunction

描述（由申请人提供）：Nlrp 3炎性体与保护性和病理性免疫应答有关。其适当的激活触发了对入侵病原体（包括流感病毒、金黄色葡萄球菌和白色念珠菌）的先天免疫应答，并且其过度应答是自身炎性综合征CAPS（cryopyrin相关周期性综合征）的基础。Nlrp 3炎性体也由异常代谢状况触发，所述异常代谢状况导致常见的衰弱性疾病如痛风、II型糖尿病和动脉粥样硬化的发展。我们已经确定了Nlrp 3炎症体被激活的途径中的一个新步骤，揭示了以前未被识别的与外源性凋亡途径激活的重叠。我们实验室的初步研究表明，与这些凋亡途径相似，Nlrp 3炎性体激活诱导线粒体功能障碍，如线粒体内正常负电位的丧失所证明的。在细胞凋亡过程中，线粒体膜电位的这种损失与线粒体脂质心磷脂从其位于内膜上的位置到外膜的易位有关。这种运动伴随着心磷脂的氧化及其结合伴侣细胞色素c释放到膜间隙。线粒体外膜上的心磷脂募集并结合半胱天冬酶-8，半胱天冬酶-8又驱动线粒体外膜孔的产生，细胞色素c通过线粒体外膜孔从其与心磷脂的系链松开，穿过线粒体外膜孔进入胞质溶胶，并触发免疫沉默细胞死亡， 凋亡我们现在表明，Nlrp 3共享这种结合线粒体心磷脂的需求和能力，Nlrp 3先前显示在激活过程中迁移到线粒体。此外，线粒体膜电位的丧失（细胞凋亡中的决定性步骤）也是Nlrp 3炎性小体活化所需的。在这个提议中，我们具体剖析了心磷脂在Nlrp 3激活中的作用，并确定Nlrp 3炎性小体激活在多大程度上反映了细胞凋亡。这些研究将确定这两种途径的分歧点，这不仅对促进我们对这一重要炎症途径的理解很重要，而且还因为一旦确定了这两种途径之间的转换可能被证明是治疗干预的目标。这些途径的操纵不仅对于修饰Nlrp 3应答是有吸引力的，而且对于从凋亡途径切换到炎性途径的可能性也是有吸引力的，这可能在恶性肿瘤或隐性感染的情况下是有益的。

DESCRIPTION (provided by applicant): The Nlrp3 inflammasome has been linked to both protective and pathologic immune responses. Its appropriate activation triggers the innate immune response to invading pathogens including influenza virus, Staphylococcus aureus and Candida albicans and its excessive response underlies the autoinflammatory syndromes CAPS (cryopyrin associated periodic syndromes). The Nlrp3 inflammasome is also triggered by abnormal metabolic conditions that lead to the development of common debilitating disorders such as gout, type II diabetes mellitus and atherosclerosis. We have identified a novel step in the pathway by which the Nlrp3 inflammasome is activated that reveals a previously unrecognized overlap with the activation of extrinsic apoptotic pathways. Preliminary studies in our lab show that similar to these apoptotic pathways Nlrp3 inflammasome activation induces mitochondrial dysfunction as demonstrated by a loss of the normal negative potential within the mitochondria. During apoptosis this loss of mitochondrial membrane potential is associated with the translocation of the mitochondrial lipid cardiolipin from its location on the inner mitochondril membrane to the outer membrane. This movement is accompanied by oxidation of cardiolipin and the release of its binding partner, cytochrome c, to the intermembrane space. Cardiolipin on the outer mitochondrial membrane recruits and binds caspase-8 that in turn drives the generation of an outer mitochondrial membrane pore through which cytochrome c, loose from its tether to cardiolipin, crosses to the cytosol and triggers immunologically silent cell death by apoptosis. We now show this requirement for and ability to bind mitochondrial cardiolipin is shared by Nlrp3, previously shown to migrate to the mitochondria during activation. Additionally, the loss of mitochondrial membrane potential, a defining step in apoptosis, is also required for Nlrp3 inflammasome activation. In this proposal we specifically dissect the role of cardiolipin in Nlrp3 activation and determine to what extent Nlrp3 inflammasome activation mirrors apoptosis. These studies will determine the point of divergence of these two pathways, important not only to advance our understanding of this vital inflammatory pathway but also because once identified this switch between pathways may prove to be a target for therapeutic intervention. Manipulation of these pathways is attractive not only for modifying Nlrp3 responses but also for the potential to switch from the apoptotic pathway to an inflammatory one as could be of benefit in the setting of malignancy or covert infections.