Role of PISA; a PYHIN Family Member in Intracellular DNA Recognition

描述（由申请人提供）：先天免疫系统通过种系编码模式识别受体感知非自身核酸。RNA通过toll样受体(TLR)-3、-7和-8或细胞质RNA解旋酶rig - 1和MDA-5感知。对于细胞质DNA的传感器知之甚少，当它被传递到细胞质时，会触发I型IFN基因转录和caspase-1介导的IL-12加工。我们已经鉴定出四种人类PYHIN蛋白之一的PISA （PYHIN蛋白刺激ASC）作为细胞质DNA的受体。PISA的HIN200结构域与DNA结合，而PYD结构域（而不是PYHIN1-3结构域）与适配器分子ASC结合以激活NF-:B和caspase-1。敲低PISA可下调caspase-1介导的IL-12反应，并伴随I型干扰素产生的增加。我们的假设是，PISA用于识别微生物细胞质DNA（如细菌或病毒DNA），并且PISA通过参与ASC和caspase-1的炎性小体的组装诱导对细胞质DNA的促炎反应。在这项研究中，我们建议进一步表征PISA在识别病毒和细菌细胞质DNA中的作用。我们还将通过基因诱捕技术和/或靶向基因删除产生一个PISA敲除小鼠，并建议分析PISA与微生物感染的体内相关性。最后，我们将评估PISA对干扰素对细胞质DNA反应的调节作用。胞质DNA识别的分子机制的阐明可能导致微生物感染的新治疗靶点，从而实现新的策略，可以防止基因治疗方法的炎症反应。

DESCRIPTION (provided by applicant): The innate immune system senses non-self nucleic acids via germ-line encoded pattern recognition receptors. RNA is sensed via Toll-like receptor (TLR)-3, -7 and -8 or by the cytoplasmic RNA helicases RIG-I and MDA-5. Little is known about sensors for cytoplasmic DNA, which when delivered to the cytoplasm trigger type I IFN gene transcription and caspase-1-mediated processing of IL-12. We have identified PISA (PYHIN protein stimulating ASC), one of four human PYHIN proteins as a receptor for cytosolic DNA. The HIN200 domain of PISA binds to DNA, while the PYD domain (but not that of PYHIN1-3) associates with the adapter molecule ASC to activate NF-:B and caspase-1. Knockdown of PISA downregulates caspase-1-mediated IL-12 responses, with concomitant increases in type I interferon production. Our hypothesis is that PISA serves to recognize microbial cytosolic DNA (such as bacterial or viral DNA) and that PISA induces pro-inflammatory responses towards cytoplasmic DNA via the assembly of an inflammasome that engages ASC and caspase-1. In this study, we propose to further characterize the role of PISA in the recognition of viral and bacterial cytosolic DNA. We will also generate a PISA knock-out mouse by gene-trap technology and/or targeted gene deletion and propose to analyze the in vivo relevance of PISA for microbial infections. Finally, we will assess the role of PISA for the modulation of interferon responses towards cytoplasmic DNA. Elucidation of the molecular mechanisms of cytosolic DNA recognition could lead to novel therapeutic targets for microbial infections and thereby enable novel strategies that could prevent inflammatory reactions to gene therapy approaches.