Department of Microbiology, Biocenter, University of Würzburg, Würzburg, Germany.
Front Cell Infect Microbiol. 2020 Oct 29;10:594932. doi: 10.3389/fcimb.2020.594932. eCollection 2020.
is a -like bacterium and emerging pathogen of the respiratory tract. It is an obligate intracellular bacterium with a biphasic developmental cycle, which replicates in a wide range of host cells. The life cycle of has been shown to proceed for more than 12 days, but little is known about the mechanisms that mediate the cellular release of these bacteria. This study focuses on the investigation of host cell exit by and its connection to host cell death modulation. We show that -infected epithelial HeLa as well as macrophage-like THP-1 cells reduce in number during the course of infection. At the same time, the infectivity of the cell culture supernatant increases, starting at the day 3 for HeLa and day 4 for THP-1 cells and reaching maximum at day 5 post infection. This correlates with the ability of to block TNFα-, but not staurosporin-induced cell death up to 3 days post infection, after which cell death is boosted by the presence of bacteria. Mitochondrial permeabilization through Bax and Bak is not essential for host cell lysis and release of . The inhibition of caspases by Z-VAD-FMK, caspase 1 by Ac-YVAD-CMK, and proteases significantly reduces the number of released infectious particles. In addition, the inhibition of myosin II by blebbistatin also strongly affects release, pointing to a possible double mechanism of exit through host cell lysis and potentially extrusion.
是一种类似于细菌的、新兴的呼吸道病原体。它是一种专性细胞内细菌，具有两相发育周期，在广泛的宿主细胞中复制。已经表明的生活周期超过 12 天，但对于介导这些细菌细胞释放的机制知之甚少。本研究专注于研究通过和宿主细胞死亡调节的宿主细胞退出。我们表明，感染上皮 HeLa 以及巨噬细胞样 THP-1 细胞在感染过程中数量减少。同时，细胞培养上清液的感染力增加，HeLa 细胞从第 3 天开始，THP-1 细胞从第 4 天开始，感染后第 5 天达到最大值。这与阻断 TNFα-，但不能阻断 3 天感染后星孢菌素诱导的细胞死亡的能力相关，此后细菌的存在会促进细胞死亡。Bax 和 Bak 通过线粒体通透化对于宿主细胞裂解和释放并不重要。通过 Z-VAD-FMK 抑制半胱天冬酶，通过 Ac-YVAD-CMK 抑制半胱天冬酶 1，以及通过蛋白酶显著减少释放的感染性颗粒的数量。此外，通过 blebbistatin 抑制肌球蛋白 II 也强烈影响的释放，表明通过宿主细胞裂解和潜在的挤出可能存在双重退出机制。
