Department of Pathology, Microbiology & Immunology, School of Veterinary Medicine, University of California, Davis, Davis, CA, USA.
College of Medicine and Veterinary Medicine, The University of Edinburgh, Edinburgh, UK.
Nat Commun. 2020 Oct 16;11(1):5258. doi: 10.1038/s41467-020-18991-8.
Macrophages play an essential role in the early immune response against Toxoplasma and are the cell type preferentially infected by the parasite in vivo. Interferon gamma (IFNγ) elicits a variety of anti-Toxoplasma activities in macrophages. Using a genome-wide CRISPR screen we identify 353 Toxoplasma genes that determine parasite fitness in naїve or IFNγ-activated murine macrophages, seven of which are further confirmed. We show that one of these genes encodes dense granule protein GRA45, which has a chaperone-like domain, is critical for correct localization of GRAs into the PVM and secretion of GRA effectors into the host cytoplasm. Parasites lacking GRA45 are more susceptible to IFNγ-mediated growth inhibition and have reduced virulence in mice. Together, we identify and characterize an important chaperone-like GRA in Toxoplasma and provide a resource for the community to further explore the function of Toxoplasma genes that determine fitness in IFNγ-activated macrophages.
巨噬细胞在针对弓形虫的早期免疫反应中发挥着重要作用，是寄生虫在体内优先感染的细胞类型。干扰素 γ（IFNγ）在巨噬细胞中引发多种抗弓形虫活性。我们使用全基因组 CRISPR 筛选鉴定了 353 个弓形虫基因，这些基因决定了未激活或 IFNγ 激活的鼠巨噬细胞中的寄生虫适应性，其中有七个得到了进一步确认。我们表明，这些基因中的一个编码致密颗粒蛋白 GRA45，它具有伴侣样结构域，对于将 GRAs 正确定位到 PVM 中以及将 GRA 效应物分泌到宿主细胞质中至关重要。缺乏 GRA45 的寄生虫对 IFNγ 介导的生长抑制更敏感，在小鼠中的毒力降低。总之，我们鉴定并表征了弓形虫中一种重要的伴侣样 GRA，并为社区提供了一个资源，以进一步探索决定 IFNγ 激活巨噬细胞适应性的弓形虫基因的功能。
