Scheithauer Lina, Thiem Stefanie, Ünal Can M, Dellmann Ansgar, Steinert Michael
Institut für Mikrobiologie, Technische Universität Braunschweig, Spielmannstr. 7, 38106 Braunschweig, Germany.
Institut für Pathologie, Städtisches Klinikum Braunschweig, Celler Straße 38, 38114 Braunschweig, Germany.
Biomolecules. 2022 Apr 22;12(5):624. doi: 10.3390/biom12050624.
The environmental bacterium is an intracellular pathogen of various protozoan hosts and able to cause Legionnaires' disease, a severe pneumonia in humans. By encoding a wide selection of virulence factors, the infectious agent possesses several strategies to manipulate its host cells and evade immune detection. In the present study, we demonstrate that the zinc metalloprotease ProA functions as a modulator of flagellin-mediated TLR5 stimulation and subsequent activation of the pro-inflammatory NF-κB pathway. We found ProA to be capable of directly degrading immunogenic FlaA monomers but not the polymeric form of bacterial flagella. These results indicate a role of the protease in antagonizing immune stimulation, which was further substantiated in HEK-Blue hTLR5 Detection assays. Addition of purified proteins, bacterial suspensions of mutant strains as well as supernatants of human lung tissue explant infection to this reporter cell line demonstrated that ProA specifically decreases the TLR5 response via FlaA degradation. Conclusively, the zinc metalloprotease ProA serves as a powerful regulator of exogenous flagellin and presumably creates an important advantage for proliferation in mammalian hosts by promoting immune evasion.
这种环境细菌是多种原生动物宿主的细胞内病原体，能够引发军团病，一种人类严重肺炎。通过编码多种毒力因子，该感染因子拥有多种策略来操纵其宿主细胞并逃避免疫检测。在本研究中，我们证明锌金属蛋白酶ProA作为鞭毛蛋白介导的TLR5刺激以及随后促炎NF-κB途径激活的调节剂发挥作用。我们发现ProA能够直接降解免疫原性FlaA单体，但不能降解细菌鞭毛的聚合形式。这些结果表明该蛋白酶在拮抗免疫刺激中发挥作用，这在HEK-Blue hTLR5检测试验中得到进一步证实。将纯化蛋白、突变菌株的细菌悬液以及人肺组织外植体感染的上清液添加到该报告细胞系中表明，ProA通过FlaA降解特异性降低TLR5反应。总之，锌金属蛋白酶ProA作为外源性鞭毛蛋白的强大调节剂，可能通过促进免疫逃避为其在哺乳动物宿主中的增殖创造重要优势。
