Determining how Kaposi’s sarcoma-associated herpesvirus hijacks caspase function to inhibit anti-viral responses

确定卡波西肉瘤相关疱疹病毒如何劫持半胱天冬酶功能以抑制抗病毒反应

• 批准号: 10729751
• 负责人: Marta Maria Gaglia
• 金额: $ 34.91万
• 依托单位: UNIVERSITY OF WISCONSIN-MADISON
• 依托单位国家: 美国
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-12-01 至 2026-11-30
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/10729751
• 关键词: AIDS related cancer; Acquired Immunodeficiency Syndrome; Affect; Africa South of the Sahara; Antiviral Response; Apoptosis; Apoptotic; Autoimmune Diseases; Biology; CASP8 gene; Caspase; Cell Death; Cells; Cessation of life; Communicable Diseases; Complex; Cytoplasm; DNA; Data; Development; Disease; Enzymes; Genetic Transcription; Herpesviridae; Herpesviridae Infections; Human Herpesvirus 8; Immune Evasion; Immune response; Infection; Innate Immune Response; Interferon Type I; Interferons; Kaposi Sarcoma; Lytic Phase; Maintenance; Mediating; Mediator; Molecular; Nature; Oncogenic Viruses; Pathway interactions; Peptide Hydrolases; Production; Proteins; Receptor Signaling; Regulation; Regulatory Pathway; Reporting; Role; Signal Transduction; Stimulus; TLR3 gene; Testing; Toll-Like Receptor Pathway; Toll-like receptors; Tumor Immunity; Up-Regulation; Viral; Virus; Virus Replication; Work; cancer type; druggable target; experience; inhibitor; insight; mutant; new therapeutic target; overexpression; pathogen; prevent; reactivation from latency; receptor; response; targeted treatment; tumor; virus host interaction; AIDS related cancer; Acquired Immunodeficiency Syndrome; Affect; Africa South of the Sahara; Antiviral Response; Apoptosis; Apoptotic; Autoimmune Diseases; Biology; CASP8 gene; Caspase; Cell Death; Cells; Cessation of life; Communicable Diseases; Complex; Cytoplasm; DNA; Data; Development; Disease; Enzymes; Genetic Transcription; Herpesviridae; Herpesviridae Infections; Human Herpesvirus 8; Immune Evasion; Immune response; Infection; Innate Immune Response; Interferon Type I; Interferons; Kaposi Sarcoma; Lytic Phase; Maintenance; Mediating; Mediator; Molecular; Nature; Oncogenic Viruses; Pathway interactions; Peptide Hydrolases; Production; Proteins; Receptor Signaling; Regulation; Regulatory Pathway; Reporting; Role; Signal Transduction; Stimulus; TLR3 gene; Testing; Toll-Like Receptor Pathway; Toll-like receptors; Tumor Immunity; Up-Regulation; Viral; Virus; Virus Replication; Work; cancer type; druggable target; experience; inhibitor; insight; mutant; new therapeutic target; overexpression; pathogen; prevent; reactivation from latency; receptor; response; targeted treatment; tumor; virus host interaction

Project summary. During lytic infection, the AIDS-associated tumor virus Kaposi’s sarcoma-associated herpesvirus (KSHV) blocks cells from activating the anti-viral type I interferon (IFN) responses. This block of the innate immune response facilitates efficient viral replication, which in turn contributes to development of Kaposi’s sarcoma. Thus, elucidating the mechanisms by which KSHV evades the host innate immune response may provide insights on how to target this and other KSHV-induced tumors. However, because of the complex and redundant nature of the type I IFN induction pathway, how KSHV blocks this early antiviral response is still incompletely understood. In a previous study, we found that the host protease caspase-8 is a major mediator of type I IFN inhibition by KSHV. KSHV reactivation from latency only triggers minimal type I IFN induction, but there is a much stronger transcriptional induction and secretion of type I IFNs when caspase-8 is also inhibited. This stronger IFN induction, in turn, reduces KSHV reactivation. These results indicate that caspase-8 activity is necessary to inhibit IFN induction, and thus promotes KSHV replication. This finding was surprising because caspase-8 activation is generally considered antiviral as it induces apoptotic cell death. However, we do not detect wide-spread cell death during reactivation from latency despite caspase-8 activation, suggesting that caspase-8 is hijacked and repurposed by KSHV to inhibit type I IFN responses. At present, the molecular mechanisms that lead to caspase-8 activity and the pathways that are targeted by caspase-8 to control type I IFN during KSHV infection remain unclear. We have new preliminary data suggesting that caspase-8 is activated by a pathogen sensing pathway, the Toll-like receptor (TLR) pathway, as a cellular response to infection. Caspase-8 then proceeds to inhibit a different pathogen sensing pathway, cGAS-mediated DNA sensing. Therefore, we hypothesize that KSHV is taking advantage of a TLR-mediated cellular response to infection that activates caspase-8. KSHV is then able to redirect this activity to inhibit DNA sensing instead of activating apoptosis. We will test this hypothesis and determine how caspase-8 is activated by TLR signaling in KSHV-infected cells without triggering cell death (Aim 1), and which host protein(s) are cleaved by caspase-8 to block cGAS-induced type I IFN responses (Aim 2). Moreover, we will also investigate whether and how caspase activity is connected to other previously described mechanisms of immune evasion by KSHV (Aim 3). As caspase-8 is a druggable target, understanding how caspase-8 is used by KSHV to regulate type I IFNs and promote its replication will reveal whether and how this enzyme could be exploited for KSHV therapy. This is important as there are no target therapies for this virus, and Kaposi’s sarcoma remains one of the leading types of cancers in sub-Saharan Africa and the second most common AIDS-associated malignancy in the US. This project will also uncover fundamental aspects of caspase signaling that may play a role in other diseases connected to IFN.

项目摘要。在裂解感染期间，与艾滋病相关的肿瘤病毒kaposi的肉瘤相关 疱疹病毒（KSHV）阻止细胞激活抗病毒I型干扰素（IFN）反应。这个块 先天免疫反应有助于有效的病毒复制，这反过来有助于发展 卡波西的肉瘤。那，阐明了KSHV逃避宿主先天免疫的机制 反应可能会提供有关如何靶向该KSHV诱导的肿瘤的见解。但是，由于 I型IFN诱导途径的复杂而冗余的性质，KSHV如何阻止此早期抗病毒药 响应仍然不完全理解。在先前的研究中，我们发现宿主蛋白酶caspase-8是一个 KSHV抑制I型IFN的主要介体。延迟延迟重新激活的KSHV重新激活仅触发最小的I IFN诱导，但是当何时有更强的转录诱导和I型IFN的分泌 caspase-8也被抑制。这种较强的IFN诱导反过来降低了KSHV重新激活。这些结果 表明caspase-8活性对于抑制IFN诱导是必要的，从而促进了KSHV复制。 这一发现令人惊讶，因为caspase-8激活通常被认为是抗病毒 凋亡细胞死亡。但是，我们在潜伏期重新激活过程中未检测到广泛的细胞死亡 Mission Caspase-8激活，表明Caspase-8被KSHV劫持和重新利用以抑制I型 IFN响应。目前，导致caspase-8活性的分子机制和 由caspase-8靶向控制在KSHV感染期间I型IFN型，尚不清楚。我们有新的 初步数据表明caspase-8被病原体传感途径激活，该途径是Toll样接收器 （TLR）途径，作为对感染的细胞反应。 caspase-8然后继续抑制不同的病原体 传感途径，CGAS介导的DNA感应。因此，我们假设KSHV正在利用 TLR介导的细胞对激活caspase-8的感染的反应。 KSHV然后能够重定向 活性以抑制DNA感测而不是激活凋亡。我们将检验该假设，并确定如何 caspase-8通过KSHV感染细胞中的TLR信号传导激活而无需触发细胞死亡（AIM 1），并且 哪种宿主蛋白​​通过caspase-8裂解以阻断CGAS诱导的I型IFN响应（AIM 2）。 此外，我们还将调查caspase活动是否以及如何连接到其他 描述了KSHV免疫进化的机制（AIM 3）。由于caspase-8是可吸毒的目标，因此 了解KSHV如何使用Caspase-8来调节I型IFN并促进其复制 是否以及如何探索KSHV疗法的这种酶。这很重要，因为没有目标 该病毒的疗法和Kaposi的肉瘤仍然是撒哈拉以南癌症的主要类型之一 非洲和美国第二大常见的艾滋病相关恶性肿瘤。这个项目也将发现 caspase信号的基本方面可能在与IFN相关的其他疾病中起作用。