Gandhi Shraddha, Puravankara Sindhoora, Mondal Anish Kumar, Chauhan Aakanksha, Yadav Shashi Prakash, Chattopadhyay Kausik, Mukhopadhaya Arunika
Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Mohali, Punjab, India.
PLoS Pathog. 2025 Apr 4;21(4):e1013033. doi: 10.1371/journal.ppat.1013033. eCollection 2025 Apr.
Vibrio cholerae cytolysin (VCC) is a potent exotoxin secreted by Vibrio cholerae, the etiological agent of the severe diarrheal disease cholera. VCC is a membrane-damaging pore-forming toxin by nature, and is well known for its ability to cause host cell death. Using wild type V. cholerae and VCC-deleted mutant variant of the bacteria, we show that VCC plays an important role in the inflammatory responses during infection in mice. This observation supports that VCC can function as a pathogen-associated molecular pattern (PAMP). Toll-like receptors (TLRs) are the key initiators of inflammation. Upon ligand recognition, TLR1 and TLR6 generally form heterodimers with TLR2 for triggering pro-inflammatory signals. In the present study, we show that VCC engages novel TLR1/4 heterodimer assembly, and elicits pro-inflammatory responses in both dendritic cells (DCs) and macrophages. Along with TLR1/4, VCC-induced pro-inflammatory response in macrophages also involves TLR2. It has been shown earlier that VCC is implicated in the V. cholerae-mediated killing of the immune cells following biofilm formation. Here we show that TLRs play an important role in VCC-mediated killing of DCs and macrophages following V. cholerae infection. Interestingly, we find that TLR1/4 signalling is specifically crucial for the VCC-induced inflammatory and death responses in DCs, as well as in mice. Additionally, we observe that similar to DCs and macrophages, TLR1/4-MyD88 play an important role in VCC-mediated inflammatory responses in another crucial immune cell type, neutrophils. Taken together, our study shows novel TLR heterodimer formation, differential recognition of the same ligand by different TLR combination in cell type-dependent manner, and their implications in the context of V. cholerae and VCC-induced immune cell death and mortality.
霍乱弧菌溶细胞素（VCC）是由霍乱弧菌分泌的一种强效外毒素，霍乱弧菌是严重腹泻病霍乱的病原体。VCC本质上是一种破坏膜的成孔毒素，以其导致宿主细胞死亡的能力而闻名。利用野生型霍乱弧菌和该细菌的VCC缺失突变变体，我们表明VCC在小鼠感染期间的炎症反应中起重要作用。这一观察结果支持VCC可作为一种病原体相关分子模式（PAMP）发挥作用。Toll样受体（TLR）是炎症的关键启动因子。在识别配体后，TLR1和TLR6通常与TLR2形成异二聚体以触发促炎信号。在本研究中，我们表明VCC参与了新型TLR1/4异二聚体的组装，并在树突状细胞（DC）和巨噬细胞中引发促炎反应。与TLR1/4一起，VCC在巨噬细胞中诱导的促炎反应也涉及TLR2。先前已表明VCC与生物膜形成后霍乱弧菌介导的免疫细胞杀伤有关。在这里我们表明，TLR在霍乱弧菌感染后VCC介导的DC和巨噬细胞杀伤中起重要作用。有趣的是，我们发现TLR1/4信号传导对于VCC诱导的DC以及小鼠中的炎症和死亡反应特别关键。此外，我们观察到，与DC和巨噬细胞类似，TLR1/4-MyD88在另一种关键免疫细胞类型中性粒细胞的VCC介导的炎症反应中起重要作用。综上所述，我们的研究显示了新型TLR异二聚体的形成、不同TLR组合以细胞类型依赖方式对同一配体的差异识别，以及它们在霍乱弧菌和VCC诱导的免疫细胞死亡及致死方面的意义。
