Bacterial activation and evasion of a PP2A phosphatase – Pyrin - Gasdermin D axis

摘要： 许多成功的革兰氏阴性病原体通过III型分泌系统逃避或阻碍先天免疫 （T3 SS），通常对毒性至关重要。耶尔森氏菌会引起肠胃炎和鼠疫等感染， 是研究T3 SS对先天免疫应答影响的一个很好的模型系统。触发 炎性小体复合物通常以半胱天冬酶-1的激活而达到高潮，半胱天冬酶-1然后裂解并成熟为促炎性小体。 炎性细胞因子IL-1b和IL-18的形式，具有众所周知的抗菌作用的细胞因子，以及孔- 在残基D276处形成和热解诱导蛋白Gasdermin D（GSDMD）。GSDMD孔还允许 IL-1b/IL-18的传递，但GSDMD切割在抵抗许多细菌感染中的作用很差 明白我们已经发现了一套非常复杂的操纵炎性小体的方法， 耶尔森氏菌T3 SS。一种半胱天冬酶-1活化途径由耶尔森氏菌效应子YopE（RhoA抑制剂）触发， 通过Pyrin炎性体导致髓样细胞中大量的IL-1b/IL-18释放。Pyrin的许多细节 激活仍然不清楚，但Pyrin似乎不是由毒素或效应物（如YopE）直接触发的 或梭菌TcdB，而不是通过宿主RhoA信号传导的病理性干扰。自发激活等位基因 此外，Pyrin还与家族性地中海热等自身炎症性疾病有关。 据信，无活性的Pyrin被磷酸化，并且需要未知的磷酸酶来触发Pyrin 炎性小体我们的实验表明PP 2A磷酸酶参与其中。我们假设PP 2A 磷酸酶正调节细菌毒素诱导的Pyrin活化，导致裂解 caspase-1、IL-1b和GSDMD。此外，有效的抑制机制，如那些促进 耶尔森氏菌T3 SS效应子YopM可以阻断这一有效的抗菌途径以促进感染。YopM 似乎特异性抑制T3 SS诱导的Pyrin炎性体，可能是通过与几种 激酶。我们的研究结果表明，缺乏YopM的减毒耶尔森菌菌株在缺乏YopM的情况下恢复毒力。 Pyrin或GSDMD。我们的目标是破译PP 2A介导的抗感染保护机制， Pyrin、caspase-1和GSDMD，但被YopM抑制。我们的工作将弥补以下方面的差距： 通过澄清与磷酸酶和激酶如何调节Pyrin相关的关键问题，了解Pyrin的知识。

Abstract: Many successful Gram-negative pathogens evade or thwart innate immunity via Type III secretion systems (T3SS), often essential for virulence. Yersinia bacteria cause infections such as gastroenteritis and plague, and is an excellent model system for studies of T3SS effects on innate immune responses. Triggering of inflammasome complexes typically culminate with activation of caspase-1 that then cleaves and matures pro- forms of inflammatory cytokines IL-1b and IL-18, cytokines with well-known antibacterial effects, and the pore- forming and pyroptosis-inducing protein Gasdermin D (GSDMD) at residue D276. GSDMD pores also allow passing of IL-1b/IL-18, but the role of GSDMD cleavage in the resistance to many bacterial infections is poorly understood. We have uncovered an extraordinarily complex set of manipulations of inflammasomes by the Yersinia T3SS. One caspase-1 activation pathway is triggered by Yersinia effector YopE, a RhoA inhibitor, and leads to substantial IL-1b/IL-18 release in myeloid cells via Pyrin inflammasomes. Many details of Pyrin activation remain unclear, but Pyrin does not appear to be directly triggered by toxins or effectors such as YopE or Clostridium TcdB, rather by pathological disturbance of host RhoA signaling. Spontaneously activating alleles of Pyrin are also linked to auto-inflammatory diseases such as familial Mediterranean fever. It is believed that inactive Pyrin is phosphorylated, and an unknown phosphatase is needed to trigger Pyrin inflammasomes. Our experiments suggest PP2A phosphatase is involved. We hypothesize that PP2A phosphatase positively regulates bacterial toxin-induced Pyrin activation leading to cleavage of caspase-1, IL-1b and GSDMD. Furthermore, effective inhibitory mechanisms such as those promoted by Yersinia T3SS effector YopM can block this effective anti-bacterial pathway to promote infection. YopM appears to specifically inhibit the T3SS induced Pyrin inflammasome, likely by interactions with several kinases. Our results suggest that attenuated Yersinia strains lacking YopM regain virulence in the absence of Pyrin or GSDMD. Our goal is to decipher the protective mechanisms against infection mediated by PP2A, Pyrin, caspase-1 and GSDMD but suppressed by YopM, in vitro and in vivo. Our work will bridge the gap of knowledge by clarifying key questions related to how Pyrin is regulated by phosphatases and kinases.