Key Laboratory of Applied Technology on Green-Eco-Healthy Animal Husbandry of Zhejiang Province, China-Australia Joint Laboratory for Animal Health Big Data Analytics, Zhejiang Provincial Engineering Laboratory for Animal Health Inspection & Internet Technology, College of Animal Science and Technology & College of Veterinary Medicine of Zhejiang A&F University, Hangzhou, China.
Front Immunol. 2020 Jun 3;11:1146. doi: 10.3389/fimmu.2020.01146. eCollection 2020.
Listeriolysin O (LLO) is a cholesterol-dependent cytolysin that mediates escape of from phagosomes and enables the bacteria to grow within the host. LLO is a versatile tool allowing to trigger several cellular responses. In this study, rapid phosphorylation of ERK1/2 on Caco-2 cells caused by infection was demonstrated to be highly dependent on LLO activity. The effect could be strongly induced by adding purified recombinant LLO alone and could be inhibited by exogenous cholesterol. Lack of the PEST sequence, known to tightly control cytotoxicity of LLO, did not affect ERK1/2 activation. However, the recombinant non-cytolytic LLO, with mutations in the cholesterol-binding motif, was unable to trigger this response. Recombinant LLO, which lacks most of the cytolytic activity, also failed to activate ERK1/2 phosphorylation, and this effect could be rescued when the protein concentration reached a cytolytic level. Infection with an LLO-deficient mutant (Δ) or the mutant complementing LLO abrogated the capacity of the bacteria to activate ERK1/2. However, infection with the Δ mutant complementing LLO, which retained partial pore-forming ability and could grow intracellularly, was capable of triggering ERK1/2 phosphorylation. Collectively, these data suggest that ERK1/2 activation by depends on the permeabilization activity of LLO and more importantly correlates with the cholesterol-binding motif of LLO.
李斯特菌溶血素 O(LLO)是一种胆固醇依赖性细胞毒素,可介导李斯特菌从吞噬体中逃逸,并使其在宿主内生长。LLO 是一种多功能工具,可使李斯特菌引发多种细胞反应。在这项研究中,证明了李斯特菌感染迅速引起 Caco-2 细胞 ERK1/2 的磷酸化高度依赖于 LLO 活性。仅添加纯化的重组 LLO 就可以强烈诱导这种作用,并且可以通过外源性胆固醇抑制。缺乏已知可严格控制 LLO 细胞毒性的 PEST 序列不会影响 ERK1/2 的激活。但是,突变了胆固醇结合基序的非细胞毒性重组 LLO 无法触发这种反应。缺乏大多数细胞毒性活性的重组 LLO 也不能激活 ERK1/2 磷酸化,并且当蛋白质浓度达到细胞毒性水平时,这种作用可以得到挽救。LLO 缺陷突变体(Δ)或互补 LLO 的突变体感染均消除了细菌激活 ERK1/2 的能力。然而,具有部分形成孔能力并能在细胞内生长的 ΔLLO 互补突变体的感染能够触发 ERK1/2 磷酸化。总的来说,这些数据表明李斯特菌通过 LLO 依赖的 ERK1/2 激活取决于 LLO 的通透活性,更重要的是与 LLO 的胆固醇结合基序相关。