Cell Death Pathways in Cytomegalovirus Pathogenesis and Control

巨细胞病毒（CMV）是新生儿和免疫功能低下宿主疾病的主要原因。这种病毒编码一系列免疫调节基因产物，确保有效的全身性感染以及长期持续和潜伏期，这在医学上具有重要意义。这个项目的重点是在第一个被感染的细胞的入口处进行宿主防御。我们解决宿主程序性细胞死亡（PCD）途径和cmv编码的抑制因子在雕刻发病机制中抑制细胞死亡的相互作用。重要的是，PCD通路以进化保守的方式与CMV编码的抑制因子结合，因此在小鼠和人类CMV中存在机制相似性。通过caspase 8介导的外源性凋亡和受体相互作用蛋白3 （RIP3）激酶介导的坏死在感染细胞内通过与两种互锁的CMV细胞死亡抑制因子的界面发挥作用，一种是β疱疹病毒保守的，抑制caspase 8的激活（vICA），另一种是最近发现的，阻断由vICA抑制caspase 8释放的坏死细胞死亡（vIRA）。通过对小鼠CMV和小鼠突变株的深入研究，我们揭示了坏死PCD途径以及vICA和vIRA之间的关系。在这里，我们将研究这些病毒编码的PCD抑制因子及其抑制的同源PCD途径的相互作用，确定可能在病原体-宿主相互作用中具有广泛意义的关键机制。通过鉴定由该病毒编码的rip3依赖性坏死死亡抑制因子并研究其机制，将建立其与人类巨细胞病毒的相关性。我们将确定细胞凋亡和坏死在单核细胞源性巨噬细胞感染的早期阶段的作用。通过这种方式，我们获得了凋亡和坏死PCD在宿主防御中的保守性方面的相关知识和理解，这是目前唯一能够完全阻止病毒和预防感染的免疫机制。特异性目的1将鉴定人cmv编码的RIP3依赖性坏死抑制剂，并研究外源性凋亡抑制剂（caspase 8）和坏死抑制剂（RIP3）对细胞命运结局的相互作用，重点关注蛋白-蛋白相互作用和触发细胞死亡的细胞信号机制的变化。Specific Aim将通过研究vICA抑制Casp8的机制，以及在细胞和小鼠中促进RIP3 RHIM和激酶依赖性坏死的蛋白-蛋白相互作用的变化，来评估caspase 8和RIP3调控的细胞死亡途径对细胞命运结局的贡献。

DESCRIPTION (provided by applicant): Cell Death Pathways in Cytomegalovirus Pathogenesis and Control Cytomegalovirus (CMV) is a major cause of disease in newborns and immunocompromised hosts. Contributing to medical significance, this virus encodes an arsenal of immunomodulatory gene products that assure efficient systemic infection as well as long-term persistence and latency. This project focuses on host defense at the portal of entry in the first cells that become infected. We address the interplay of host programmed cell death (PCD) pathways and the CMV-encoded suppressors that inhibit cell death in sculpting pathogenesis. Importantly, PCD pathways interface with CMV-encoded suppressors in an evolutionarily conserved fashion such that there are mechanistic similarity in murine and human CMV. Extrinsic apoptosis mediated through caspase 8 and necrosis mediated by receptor interacting protein 3 (RIP3) kinase play out within infected cells by interfacing with two interlocked classes of CMV cell death suppressors, one that is betaherpesvirus- conserved and suppresses caspase 8 activation (vICA) and the other, recently discovered, that blocks necrotic cell death (vIRA) unleashed by vICA inhibition of caspase 8. The necrotic PCD pathway and the relationship between vICA and vIRA were brought to light through our incisive studies employing murine CMV and mutant strains of mice. Here, we will investigate the interplay of these virus-encoded PCD suppressors and the cognate PCD pathways they inhibit, identifying key mechanism(s) that likely have broad significance in pathogen-host interactions. Relevance to human CMV will be established by identifying the RIP3-dependent necrotic death suppressor(s) encoded by this virus and studying mechanism. We will determine the role of apoptosis and necrosis in the earliest stages of infection of monocyte-derived macrophage. In this manner, we gain knowledge and understanding relevant to conserved aspects of apoptotic and necrotic PCD in host defense, which is the only immune mechanism currently able to completely stop virus and prevent infection: Specific Aim 1 will identify the human CMV-encoded inhibitor of RIP3-dependent necrosis and investigate the interplay of inhibitors of extrinsic apoptosis (caspase 8) and necrosis (RIP3) on cell fate outcomes, focusing on changes in protein-protein interactions and cell signaling machinery that trigger cell death. Specific Aim will evaluate the contribution of caspase 8- and RIP3-regulated cell death pathways to cell fate outcome by investigating the mechanism of Casp8 inhibition by vICA, as well as changes in protein-protein interactions that contribute to RIP3 RHIM- and kinase-dependent necrosis in cells and mice.