The role of TREX1 for innate sensing human endogenous retroviruses

TREX1 在先天感知人类内源性逆转录病毒中的作用

• 批准号: 318196085
• 负责人: Professor Dr. Oliver T. Fackler, Ph.D.
• 金额: --
• 依托单位: Abteilung Molekulare Virologie
• 依托单位国家: 德国
• 项目类别: Priority Programmes
• 财政年份: 2016
• 资助国家: 德国
• 起止时间: 2015-12-31 至 2019-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/318196085?language=en
• 关键词: role; TREX1; innate; sensing; human

HIV-1 reverse transcription (RT) products are predominantly sensed in most cell types by the cyclic GMP-AMP synthase cGAS-STING pathway. The host cell cytoplasmic exonuclease TREX1 was described to metabolize exogenous retroviral RT products in the cytoplasm of mammalian cells and studies in trex1 knock-out mice suggested that TREX1 has an important role in the elimination of ERV RT products as well as of cytoplasmic DNA products resulting from DNA damage. Based on these results reported in the literature, a central hypothesis of this project was that TREX1 plays a central role in controlling innate (auto) immune responses by lowering the amounts of retroviral and cellular cytoplasmic DNA to avoid innate immune sensing. Work in the first funding period established innate immune sensing competent and –incompetent cell systems with or without TREX1 expression for the analysis of TREX1 function in response to infection with exogenous retrovirus or upon induction of expression of endogenous retroviruses or DNA damage. In parallel, assays were established for the quantification of enzymatic activities of TREX1 in vitro and their immunological consequences in cells. Finally, the analysis of TREX1 expression in human cells yielded an unexpectedly complex pattern of cell-type and stimulation-dependent expression of various TREX1 isoforms that differ in their substrate specificity and revealed that TREX1 can be subject to proteolytic cleavage. Work in the second funding period will build on these tools and findings to achieve a comprehensive understanding of the role of diverse TREX1 isoforms and processing products in human cells in the context of retrovirus infection and DNA damage. Since TREX1 is a transmembrane protein localized at the endoplasmic reticulum as well as in the nucleus, another central question is how and where the exonuclease has access to retroviral RT products. To address these questions, we will conduct (i) a comprehensive functional characterization of TREX1 isoforms and cleavage products and (ii) dissect the immunological consequences of the metabolism of cytoplasmic DNA. These analyses will systematically compare exogenous infections with HIV-1 with the induction of ERV expression or DNA damage. Together, we aim at providing novel tempo-spatial and mechanistic insight in the interplay between TREX1 and retroviral replication.

HIV-1逆转录（RT）产物在大多数细胞类型中主要通过环GMP-AMP合酶cGAS-STING途径检测。宿主细胞胞质核酸外切酶TREX 1被描述为在哺乳动物细胞的细胞质中代谢外源性逆转录病毒RT产物，并且在RX 1基因敲除小鼠中的研究表明，TREX 1在消除ERV RT产物以及由DNA损伤引起的胞质DNA产物中具有重要作用。基于文献中报道的这些结果，该项目的中心假设是TREX 1通过降低逆转录病毒和细胞胞质DNA的量以避免先天免疫感测在控制先天（自身）免疫应答中起核心作用。在第一个资助期的工作建立了先天免疫感应能力和无能力的细胞系统，有或没有TREX 1表达，用于分析TREX 1功能，以响应外源性逆转录病毒感染或诱导内源性逆转录病毒表达或DNA损伤。同时，建立了用于定量TREX 1体外酶活性及其在细胞中的免疫学后果的测定法。最后，人细胞中TREX 1表达的分析产生了出乎意料的复杂模式的细胞类型和刺激依赖性表达的各种TREX 1同种型，不同的底物特异性，并揭示了TREX 1可以进行蛋白水解切割。第二个资助期的工作将建立在这些工具和发现的基础上，以全面了解逆转录病毒感染和DNA损伤背景下人类细胞中不同TREX 1亚型和加工产物的作用。由于TREX 1是位于内质网以及细胞核中的跨膜蛋白，另一个中心问题是外切核酸酶如何以及在何处获得逆转录病毒RT产物。为了解决这些问题，我们将进行（i）TREX 1亚型和切割产物的全面功能表征和（ii）剖析细胞质DNA代谢的免疫学后果。这些分析将系统地比较HIV-1的外源性感染与ERV表达或DNA损伤的诱导。总之，我们的目标是在TREX 1和逆转录病毒复制之间的相互作用提供新的时空和机制的见解。