Center of Infectious Diseases and Pathogen Biology, Institute of Virology and AIDS Research, Key Laboratory of Organ Regeneration and Transplantation of The Ministry of Education, The First Hospital of Jilin University, Changchun, China.
College of Medicine, Jilin University, Changchun, China.
mBio. 2022 Jun 28;13(3):e0130022. doi: 10.1128/mbio.01300-22. Epub 2022 May 31.
Ubiquitin signaling is essential for immunity to restrict pathogen proliferation. Due to its enormous impact on human health and the global economy, intensive efforts have been invested in studying severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and its interactions with hosts. However, the role of the ubiquitin network in pathogenicity has not yet been explored. Here, we found that ORF9b of SARS-CoV-2 is ubiquitinated on Lys-4 and Lys-40 by unknown E3 ubiquitin ligases and is degraded by the ubiquitin proteasomal system. Importantly, we identified USP29 as a host factor that prevents ORF9b ubiquitination and subsequent degradation. USP29 interacts with the carboxyl end of ORF9b and removes ubiquitin chains from the protein, thereby inhibiting type I interferon (IFN) induction and NF-κB activation. We also found that ORF9b stabilization by USP29 enhanced the virulence of VSV-eGFP and transcription and replication-competent SARS-CoV-2 virus-like-particles (trVLP). Moreover, we observed that the mRNA level of USP29 in SARS-CoV-2 patients was higher than that in healthy people. Our findings provide important evidence indicating that targeting USP29 may effectively combat SARS-CoV-2 infection. Coronavirus disease 2019 (COVID-19) is a current global health threat caused by SARS-CoV-2. The innate immune response such as type I IFN (IFN-I) is the first line of host defense against viral infections, whereas SARS-CoV-2 proteins antagonize IFN-I production through distinct mechanisms. Among them, ORF9b inhibits the canonical IκB kinase alpha (IKKɑ)/β/γ-NF-κB signaling and subsequent IFN production; therefore, discovering the regulation of ORF9b by the host might help develop a novel antiviral strategy. Posttranslational modification of proteins by ubiquitination regulates many biological processes, including viral infections. Here, we report that ORF9b is ubiquitinated and degraded through the proteasome pathway, whereas deubiquitinase USP29 deubiquitinates ORF9b and prevents its degradation, resulting in the enhancement of ORF9b-mediated inhibition of IFN-I and NF-κB activation and the enhancement of virulence of VSV-eGFP and SARS-CoV-2 trVLP.
泛素信号对于限制病原体增殖的免疫至关重要。由于其对人类健康和全球经济的巨大影响，人们投入了大量精力研究严重急性呼吸综合征冠状病毒 2（SARS-CoV-2）及其与宿主的相互作用。然而，泛素网络在致病性中的作用尚未得到探索。在这里，我们发现 SARS-CoV-2 的 ORF9b 被未知的 E3 泛素连接酶在赖氨酸 4 和赖氨酸 40 上泛素化，并被泛素蛋白酶体系统降解。重要的是，我们鉴定了 USP29 是一种阻止 ORF9b 泛素化和随后降解的宿主因子。USP29 与 ORF9b 的羧基端相互作用，并从蛋白质上去除泛素链，从而抑制 I 型干扰素（IFN）诱导和 NF-κB 激活。我们还发现，USP29 稳定 ORF9b 增强了 VSV-eGFP 和转录和复制有活性的 SARS-CoV-2 病毒样颗粒（trVLP）的毒力。此外，我们观察到 SARS-CoV-2 患者的 USP29 mRNA 水平高于健康人。我们的研究结果提供了重要的证据，表明靶向 USP29 可能有效对抗 SARS-CoV-2 感染。 新型冠状病毒肺炎（COVID-19）是由 SARS-CoV-2 引起的当前全球健康威胁。I 型干扰素（IFN-I）等先天免疫反应是宿主防御病毒感染的第一道防线，而 SARS-CoV-2 蛋白通过不同的机制拮抗 IFN-I 的产生。其中，ORF9b 抑制经典 IKKɑ/β/γ-NF-κB 信号和随后的 IFN 产生；因此，发现宿主对 ORF9b 的调节可能有助于开发新的抗病毒策略。泛素化对蛋白质的翻译后修饰调节着许多生物学过程，包括病毒感染。在这里，我们报告 ORF9b 通过蛋白酶体途径被泛素化和降解，而去泛素化酶 USP29 去泛素化 ORF9b 并阻止其降解，导致 ORF9b 介导的 IFN-I 抑制和 NF-κB 激活增强，以及 VSV-eGFP 和 SARS-CoV-2 trVLP 的毒力增强。
