Torelli Francesca, da Fonseca Diogo M, Butterworth Simon W, Young Joanna C, Treeck Moritz
Signalling in Apicomplexan Parasites Laboratory, The Francis Crick Institute, London, United Kingdom.
Host-Pathogen Interactions Laboratory, Gulbenkian Institute for Molecular Medicine, Oeiras, Portugal.
Elife. 2024 Dec 10;13:RP102592. doi: 10.7554/eLife.102592.
is an intracellular parasite that subverts host cell functions via secreted virulence factors. Up to 70% of parasite-controlled changes in the host transcriptome rely on the MYR1 protein, which is required for the translocation of secreted proteins into the host cell. Mice infected with MYR1 knock-out (KO) strains survive infection, supporting a paramount function of MYR1-dependent secreted proteins in virulence and proliferation. However, we have previously shown that MYR1 mutants have no growth defect in pooled CRISPR-Cas9 screens in mice, suggesting that the presence of parasites that are wild-type at the locus in pooled screens can rescue the phenotype. Here, we demonstrate that MYR1 is not required for the survival in IFN-γ-activated murine macrophages, and that parasites lacking MYR1 are able to expand during the onset of infection. While ΔMYR1 parasites have restricted growth in single-strain murine infections, we show that the phenotype is rescued by co-infection with wild-type (WT) parasites , independent of host functional adaptive immunity or key pro-inflammatory cytokines. These data show that the major function of MYR1-dependent secreted proteins is not to protect the parasite from clearance within infected cells. Instead, MYR-dependent proteins generate a permissive niche in a paracrine manner, which rescues ΔMYR1 parasites within a pool of CRISPR mutants in mice. Our results highlight an important limitation of otherwise powerful CRISPR screens and point towards key functions for MYR1-dependent -host interactions beyond the infected cell.
是一种细胞内寄生虫，它通过分泌毒力因子来颠覆宿主细胞功能。宿主转录组中高达70%的由寄生虫控制的变化依赖于MYR1蛋白，该蛋白是分泌蛋白转运到宿主细胞所必需的。感染MYR1基因敲除（KO）菌株的小鼠能在感染中存活，这支持了依赖MYR1的分泌蛋白在毒力和增殖方面的至关重要的功能。然而，我们之前已经表明，在小鼠的混合CRISPR - Cas9筛选中，MYR1突变体没有生长缺陷，这表明在混合筛选中该位点为野生型的寄生虫的存在可以挽救该表型。在这里，我们证明在IFN -γ激活的小鼠巨噬细胞中存活不需要MYR1，并且缺乏MYR1的寄生虫在感染开始时能够增殖。虽然ΔMYR1寄生虫在单菌株小鼠感染中生长受限，但我们表明与野生型（WT）寄生虫共同感染可以挽救该表型，这与宿主功能性适应性免疫或关键促炎细胞因子无关。这些数据表明，依赖MYR1的分泌蛋白的主要功能不是保护寄生虫免受感染细胞内的清除。相反，依赖MYR的蛋白以旁分泌方式产生一个允许的微环境，从而在小鼠的CRISPR突变体库中挽救ΔMYR1寄生虫。我们的结果突出了原本强大的CRISPR筛选的一个重要局限性，并指出了依赖MYR1的宿主 - 寄生虫相互作用在感染细胞之外的关键功能。
