School of Veterinary Medicine, Department of Pathology, Microbiology and Immunology, University of California Davis, Davis, California, USA.
Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA.
mBio. 2019 Jul 16;10(4):e00808-19. doi: 10.1128/mBio.00808-19.
The protozoan parasite secretes proteins from specialized organelles, the rhoptries, and dense granules, which are involved in the modulation of host cell processes. Dense granule protein GRA15 activates the nuclear factor kappa B (NF-κB) pathway, which plays an important role in cell death, innate immunity, and inflammation. Exactly how GRA15 activates the NF-κB pathway is unknown. Here we show that GRA15 interacts with tumor necrosis factor receptor-associated factors (TRAFs), which are adaptor proteins functioning upstream of the NF-κB transcription factor. We identified several TRAF binding sites in the GRA15 amino acid sequence and showed that these are involved in NF-κB activation. Furthermore, a TRAF2 knockout cell line has impaired GRA15-mediated NF-κB activation. Thus, we determined the mechanism for GRA15-dependent NF-κB activation. The parasite can cause birth defects and severe disease in immunosuppressed patients. Strain differences in pathogenicity exist, and these differences are due to polymorphic effector proteins that secretes into the host cell to coopt host cell functions. The effector protein GRA15 of some strains activates the nuclear factor kappa B (NF-κB) pathway, which plays an important role in cell death, innate immunity, and inflammation. We show that GRA15 interacts with TNF receptor-associated factors (TRAFs), which are adaptor proteins functioning upstream of the NF-κB transcription factor. Deletion of TRAF-binding sites in GRA15 greatly reduces its ability to activate the NF-κB pathway, and TRAF2 knockout cells have impaired GRA15-mediated NF-κB activation. Thus, we determined the mechanism for GRA15-dependent NF-κB activation.
原生动物寄生虫从专门的细胞器——棒状体和致密颗粒中分泌蛋白质，这些蛋白质参与宿主细胞过程的调节。致密颗粒蛋白 GRA15 激活核因子 kappa B（NF-κB）途径，该途径在细胞死亡、先天免疫和炎症中发挥重要作用。确切地说，GRA15 如何激活 NF-κB 途径尚不清楚。在这里，我们表明 GRA15 与肿瘤坏死因子受体相关因子（TRAFs）相互作用，TRAFs 是在 NF-κB 转录因子上游发挥作用的衔接蛋白。我们在 GRA15 氨基酸序列中鉴定了几个 TRAF 结合位点，并表明这些结合位点参与 NF-κB 激活。此外，TRAF2 敲除细胞系中 GRA15 介导的 NF-κB 激活受损。因此，我们确定了 GRA15 依赖性 NF-κB 激活的机制。寄生虫可导致免疫抑制患者出生缺陷和严重疾病。致病性存在菌株差异，这些差异是由于寄生虫分泌到宿主细胞中的多态效应蛋白，以篡夺宿主细胞的功能。一些寄生虫株的效应蛋白 GRA15 激活核因子 kappa B（NF-κB）途径，该途径在细胞死亡、先天免疫和炎症中发挥重要作用。我们表明 GRA15 与肿瘤坏死因子受体相关因子（TRAFs）相互作用，TRAFs 是在 NF-κB 转录因子上游发挥作用的衔接蛋白。GRA15 中 TRAF 结合位点的缺失极大地降低了其激活 NF-κB 途径的能力，并且 TRAF2 敲除细胞中 GRA15 介导的 NF-κB 激活受损。因此，我们确定了 GRA15 依赖性 NF-κB 激活的机制。
