Department of Veterinary Clinical Sciences, College of Veterinary Medicine, China Agricultural University, Beijing, China.
Front Immunol. 2021 Nov 5;12:757909. doi: 10.3389/fimmu.2021.757909. eCollection 2021.
Infantis has emerged as a major clinical pathogen causing gastroenteritis worldwide in recent years. As an intracellular pathogen, has evolved to manipulate and benefit from the cell death signaling pathway. In this study, we discovered that . Infantis inhibited apoptosis of infected Caco-2 cells by phosphorylating Akt. Notably, Akt phosphorylation was observed in a discontinuous manner: immediately 0.5 h after the invasion, then before peak cytosolic replication. Single-cell analysis revealed that the second phase was only induced by cytosolic hyper-replicating bacteria at 3-4 hpi. Next, Akt-mediated apoptosis inhibition was found to be initiated by Furthermore, Akt phosphorylation increased mitochondrial localization of Bcl-2 to prevent Bax oligomerization on the mitochondrial membrane, maintaining the mitochondrial network homeostasis to resist apoptosis. In addition, . Infantis induced pyroptosis, as evidenced by increased caspase-1 (p10) and GSDMS-N levels. In contrast, cells infected with the Δ strain displayed faster but less severe pyroptosis and had less bacterial load. The results indicated that . Infantis -mediated Akt phosphorylation delayed pyroptosis, but aggravated its severity. The wild-type strain also caused more severe diarrhea and intestinal inflammatory damage than the Δ strain in mice. These findings revealed that . Infantis delayed the cells' death by intermittent activation of Akt, allowing sufficient time for replication, thereby causing more severe inflammation.
近年来,婴儿型大肠埃希菌已成为引起全球范围内胃肠炎的主要临床病原体。作为一种细胞内病原体,它已经进化到能够操纵和利用细胞死亡信号通路从中获益。在本研究中,我们发现婴儿型大肠埃希菌通过磷酸化 Akt 来抑制感染的 Caco-2 细胞凋亡。值得注意的是,Akt 磷酸化呈不连续方式出现:在入侵后 0.5 h 立即出现,然后在细胞质复制高峰之前出现。单细胞分析表明,第二期仅在 3-4 hpi 时由细胞质超复制细菌诱导。接下来,我们发现 Akt 介导的细胞凋亡抑制是由 引发的。此外,Akt 磷酸化增加了 Bcl-2 在线粒体中的定位,以防止 Bax 在线粒体膜上寡聚化,维持线粒体网络的平衡以抵抗凋亡。此外,婴儿型大肠埃希菌诱导了细胞焦亡,表现为 caspase-1(p10)和 GSDMD-N 水平升高。相比之下,感染 Δ 株的细胞显示出更快但更不严重的细胞焦亡和更少的细菌负荷。结果表明,婴儿型大肠埃希菌通过间歇性激活 Akt 来延迟细胞焦亡,但会加重其严重程度。野生型菌株在小鼠中也比 Δ 株引起更严重的腹泻和肠道炎症损伤。这些发现表明,婴儿型大肠埃希菌通过间歇性激活 Akt 来延迟细胞死亡,从而为复制提供了足够的时间,导致更严重的炎症。