Earlham Institute, Norwich Research Park, Norwich, United Kingdom.
Quadram Institute Bioscience, Norwich Research Park, Norwich, United Kingdom.
Front Cell Infect Microbiol. 2022 Aug 17;12:834895. doi: 10.3389/fcimb.2022.834895. eCollection 2022.
Macroautophagy is a ubiquitous homeostasis and health-promoting recycling process of eukaryotic cells, targeting misfolded proteins, damaged organelles and intracellular infectious agents. Some intracellular pathogens such as serovar Typhimurium hijack this process during pathogenesis. Here we investigate potential protein-protein interactions between host transcription factors and secreted effector proteins of and their effect on host gene transcription. A systems-level analysis identified effector proteins that had the potential to affect core autophagy gene regulation. The effect of a SPI-1 effector protein, SopE, that was predicted to interact with regulatory proteins of the autophagy process, was investigated to validate our approach. We then confirmed experimentally that SopE can directly bind to SP1, a host transcription factor, which modulates the expression of the autophagy gene . We also revealed that SopE might have a double role in the modulation of autophagy: Following initial increase of transcription triggered by infection, subsequent decrease in transcription at 6h post-infection was SopE-dependent. SopE also played a role in modulation of the autophagy flux machinery, in particular MAP1LC3B and p62 autophagy proteins, depending on the level of autophagy already taking place. Upon typical infection of epithelial cells, the autophagic flux is increased. However, when autophagy was chemically induced prior to infection, SopE dampened the autophagic flux. The same was also observed when most of the intracellular cells were not associated with the SCV (strain lacking ) regardless of the autophagy induction status before infection. We demonstrated how regulatory network analysis can be used to better characterise the impact of pathogenic effector proteins, in this case, . This study complements previous work in which we had demonstrated that specific pathogen effectors can affect the autophagy process through direct interaction with autophagy proteins. Here we show that effector proteins can also influence the upstream regulation of the process. Such interdisciplinary studies can increase our understanding of the infection process and point out targets important in intestinal epithelial cell defense.
自噬是真核细胞普遍存在的一种维持细胞内环境稳定和促进健康的回收过程，靶向错误折叠的蛋白质、受损的细胞器和细胞内感染因子。一些细胞内病原体，如肠炎沙门氏菌，在发病过程中劫持了这个过程。在这里，我们研究了宿主转录因子与肠炎沙门氏菌分泌效应蛋白之间的潜在蛋白-蛋白相互作用及其对宿主基因转录的影响。系统水平分析确定了一些效应蛋白，这些蛋白有可能影响核心自噬基因的调节。我们研究了预测与自噬过程的调节蛋白相互作用的 SPI-1 效应蛋白 SopE 的作用，以验证我们的方法。然后，我们通过实验证实 SopE 可以直接与 SP1（一种宿主转录因子）结合，从而调节自噬基因 的表达。我们还揭示 SopE 可能在调节自噬方面具有双重作用：在感染后 6 小时，感染触发的 转录最初增加后，随后的 转录减少依赖于 SopE。SopE 还在调节自噬通量机制方面发挥作用，特别是 MAP1LC3B 和 p62 自噬蛋白，这取决于已经发生的自噬程度。在典型的上皮细胞感染中，自噬通量增加。然而，当自噬在感染前通过化学方法诱导时，SopE 会抑制自噬通量。当感染前大多数细胞内的 细胞与 SCV（缺乏 的菌株）无关时，也观察到了同样的情况，而不管感染前自噬的诱导状态如何。我们展示了如何使用调控网络分析来更好地描述致病效应蛋白的影响，在这种情况下，是 。这项研究补充了我们之前的工作，即特定的病原体效应蛋白可以通过与自噬蛋白的直接相互作用来影响自噬过程。在这里，我们表明效应蛋白也可以影响该过程的上游调节。这种跨学科的研究可以增加我们对感染过程的理解，并指出在肠道上皮细胞防御中重要的靶点。
