Section of Microbiology, MRC Centre for Molecular Bacteriology and Infection, Imperial College London, London, United Kingdom.
PLoS One. 2013;8(1):e53064. doi: 10.1371/journal.pone.0053064. Epub 2013 Jan 8.
Intracellular replication of Salmonella enterica requires effector proteins translocated across the Salmonella-containing vacuolar membrane by Salmonella pathogenicity island-2 (SPI-2) encoded type III secretion system (T3SS). The SPI-2 T3SS effector SseL is a deubiquitinase that contributes to virulence in mice. Previous work has produced conflicting evidence as to the involvement of SseL in interference with the NF-κB pathway. To attempt to clarify these discrepancies, we compared mRNA levels in mouse primary bone marrow-derived macrophages infected with wild-type or sseL mutant strains using a genome-wide microarray. There was no detectable effect of loss of SseL on mRNA levels corresponding to any known NF-κB-regulated gene. In addition, there was no effect of SseL on (i) the activation or levels of both the canonical inhibitor of the NF-κB pathway (IκBα and phospho-IκBα), and the non-canonical NF-κB precursor p100/p52, (ii) the translocation of the NF-κB transcription factor p65 to the nucleus of infected macrophages and (iii) pro-inflammatory cytokines secretion. Furthermore, ectopic expression of SseL did not affect NF-κB activation in reporter cell lines. These results fail to support a role for SseL in the down-regulation of the host immune response and in particular the NF-κB pathway.
沙门氏菌肠内复制需要效应蛋白通过沙门氏菌致病性岛-2（SPI-2）编码的 III 型分泌系统（T3SS）穿过沙门氏菌包含的液泡膜转运。SPI-2 T3SS 效应蛋白 SseL 是一种去泛素化酶，有助于在小鼠中产生毒力。先前的工作对 SseL 参与干扰 NF-κB 途径产生了相互矛盾的证据。为了试图澄清这些差异，我们使用全基因组微阵列比较了野生型或 sseL 突变株感染的小鼠原代骨髓来源的巨噬细胞中的 mRNA 水平。SseL 的缺失对任何已知的 NF-κB 调节基因的 mRNA 水平没有可检测到的影响。此外，SseL 对（i）NF-κB 途径的经典抑制剂（IκBα 和磷酸化 IκBα）和非经典 NF-κB 前体 p100/p52 的激活或水平没有影响，（ii）NF-κB 转录因子 p65 向感染的巨噬细胞核的易位和（iii）促炎细胞因子的分泌也没有影响。此外，SseL 的异位表达不会影响报告细胞系中 NF-κB 的激活。这些结果不支持 SseL 在下调宿主免疫反应，特别是 NF-κB 途径中的作用。
