Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles , Los Angeles, California, USA.
Molecular Biology Institute, University of California, Los Angeles , Los Angeles, California, USA.
mSphere. 2023 Oct 24;8(5):e0026323. doi: 10.1128/msphere.00263-23. Epub 2023 Sep 28.
's propensity to infect its host and cause disease is highly dependent on its ability to modulate host cell functions. One of the strategies the parasite uses to accomplish this is via the export of effector proteins from the secretory dense granules. Dense granule (GRA) proteins are known to play roles in nutrient acquisition, host cell cycle manipulation, and immune regulation. Here, we characterize a novel dense granule protein named GRA83, which localizes to the parasitophorous vacuole (PV) in tachyzoites and bradyzoites. Disruption of results in increased virulence, weight loss, and parasitemia during the acute infection, as well as a marked increase in the cyst burden during the chronic infection. This increased parasitemia was associated with an accumulation of inflammatory infiltrates in tissues in both acute and chronic infections. Murine macrophages infected with ∆ tachyzoites produced less interleukin-12 (IL-12) , which was confirmed with reduced IL-12 and interferon-gamma . This dysregulation of cytokines correlates with reduced nuclear translocation of the p65 subunit of the nuclear factor-κB (NF-κB) complex. While GRA15 similarly regulates NF-κB, infection with ∆∆ parasites did not further reduce p65 translocation to the host cell nucleus, suggesting these GRAs function in converging pathways. We also used proximity labeling experiments to reveal candidate GRA83 interacting -derived partners. Taken together, this work reveals a novel effector that stimulates the innate immune response, enabling the host to limit the parasite burden. Importance poses a significant public health concern as it is recognized as one of the leading foodborne pathogens in the United States. Infection with the parasite can cause congenital defects in neonates, life-threatening complications in immunosuppressed patients, and ocular disease. Specialized secretory organelles, including the dense granules, play an important role in the parasite's ability to efficiently invade and regulate components of the host's infection response machinery to limit parasite clearance and establish an acute infection. s ability to avoid early clearance, while also successfully infecting the host long enough to establish a persistent chronic infection, is crucial in allowing for its transmission to a new host. While multiple GRAs directly modulate host signaling pathways, they do so in various ways highlighting the parasite's diverse arsenal of effectors that govern infection. Understanding how parasite-derived effectors harness host functions to evade defenses yet ensure a robust infection is important for understanding the complexity of the pathogen's tightly regulated infection. In this study, we characterize a novel secreted protein named GRA83 that stimulates the host cell's response to limit infection.
其感染宿主并致病的倾向在很大程度上取决于其调节宿主细胞功能的能力。寄生虫完成此任务的策略之一是从分泌致密颗粒中输出效应蛋白。致密颗粒 (GRA) 蛋白已知在营养物质获取、宿主细胞周期操纵和免疫调节中发挥作用。在这里，我们描述了一种新型致密颗粒蛋白 GRA83，它定位于速殖子和缓殖子中的滋养体空泡 (PV)。破坏 导致急性感染时毒力增加、体重减轻和寄生虫血症增加，以及慢性感染时囊泡负担明显增加。这种寄生虫血症增加与急性和慢性感染组织中炎症浸润的积累有关。感染 ∆ 速殖子的小鼠巨噬细胞产生的白细胞介素 12 (IL-12) 减少，这与 IL-12 和干扰素-γ 减少得到证实。这种细胞因子的失调与核因子-κB (NF-κB) 复合物的 p65 亚基向宿主细胞核的核易位减少有关。虽然 GRA15 同样调节 NF-κB，但感染 ∆∆ 寄生虫不会进一步减少 p65 向宿主细胞核的易位，这表明这些 GRA 作用于趋同途径。我们还使用邻近标记实验来揭示候选 GRA83 相互作用的 -衍生伙伴。总之，这项工作揭示了一种新型效应子，它刺激先天免疫反应，使宿主能够限制寄生虫负担。重要性 是一个重大的公共卫生问题，因为它被认为是美国主要的食源性病原体之一。寄生虫感染可导致新生儿先天性缺陷、免疫抑制患者危及生命的并发症和眼部疾病。包括致密颗粒在内的专门分泌细胞器在寄生虫有效入侵和调节宿主感染反应机制成分以限制寄生虫清除和建立急性感染方面发挥着重要作用。寄生虫避免早期清除的能力，同时成功感染宿主以足够长的时间建立持续的慢性感染，对于其传播到新宿主至关重要。虽然多种 GRA 直接调节宿主信号通路，但它们的作用方式不同，这突出了寄生虫控制感染的多种效应子武器。了解寄生虫衍生效应子如何利用宿主功能来逃避防御，同时确保强大的感染，对于理解病原体严格调节的感染的复杂性很重要。在这项研究中，我们描述了一种新型分泌蛋白 GRA83，它刺激宿主细胞对感染的反应以限制感染。
