a Departamento de Biomedicina Molecular , Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional , Ciudad de México , México.
b Department of Pediatrics , University of California San Diego , San Diego , CA , USA.
Virulence. 2018;9(1):1390-1402. doi: 10.1080/21505594.2018.1509664.
B cells are a target of Salmonella infection, allowing bacteria survival without inducing pyroptosis. This event is due to downregulation of Nlrc4 expression and lack of inflammasome complex activation, which impairs the secretion of IL-1β. YAP phosphorylation is required for downregulation of Nlrc4 in B cells during Salmonella infection; however, the microorganism's mechanisms underlying the inhibition of the NLRC4 inflammasome in B cells are not fully understood. Our findings demonstrate that the Salmonella effector SopB triggers a signaling cascade involving PI3K, PDK1 and mTORC2 that activates Akt with consequent phosphorylation of YAP. When we deleted sopB in Salmonella, infected B cells that lack Rictor, or inhibited the signaling cascade using a pharmacological approach, we were able to restore the function of the NLRC4 inflammasome in B cells and the ability to control the infection. Furthermore, B cells from infected mice exhibited activation of Akt and YAP phosphorylation, suggesting that Salmonella also triggers this pathway in vivo. In summary, our data demonstrate that the Salmonella effector inositide phosphate phosphatase SopB triggers the PI3K-Akt-YAP pathway to inhibit the NLRC4 inflammasome in B cells. This study provides further evidence that Salmonella triggers cellular mechanisms in B lymphocytes to manipulate the host environment by turning it into a survival niche to establish a successful infection.
B 细胞是沙门氏菌感染的靶标,使细菌在不诱导细胞焦亡的情况下存活。这一事件归因于 Nlrc4 表达下调和炎症小体复合物激活缺乏,从而损害了 IL-1β 的分泌。YAP 磷酸化是沙门氏菌感染期间 B 细胞中 Nlrc4 下调所必需的;然而,微生物抑制 B 细胞中 NLRC4 炎症小体的机制尚不完全清楚。我们的研究结果表明,沙门氏菌效应蛋白 SopB 触发了一个涉及 PI3K、PDK1 和 mTORC2 的信号级联反应,该反应激活 Akt,随后磷酸化 YAP。当我们在沙门氏菌中缺失 sopB、感染缺乏 Rictor 的 B 细胞,或使用药理学方法抑制信号级联反应时,我们能够恢复 B 细胞中 NLRC4 炎症小体的功能,并控制感染。此外,感染小鼠的 B 细胞表现出 Akt 的激活和 YAP 磷酸化,表明沙门氏菌在体内也触发了这一途径。总之,我们的数据表明,沙门氏菌效应物肌醇磷酸盐磷酸酶 SopB 触发 PI3K-Akt-YAP 途径抑制 B 细胞中的 NLRC4 炎症小体。本研究进一步证明,沙门氏菌通过将 B 淋巴细胞中的细胞机制转化为生存龛,来操纵宿主环境,从而建立成功的感染。