Université Paris-Saclay, UVSQ, Inserm, Infection et inflammation, Montigny-Le-Bretonneux, France.
Centre National de la Recherche Scientifique UMR 9004, Institut de Recherche en Infectiologie de Montpellier (IRIM), Université de Montpellier, Montpellier, France.
PLoS Pathog. 2022 Aug 12;18(8):e1010771. doi: 10.1371/journal.ppat.1010771. eCollection 2022 Aug.
ESX type VII secretion systems are complex secretion machineries spanning across the mycobacterial membrane and play an important role in pathogenicity, nutrient uptake and conjugation. We previously reported the role of ESX-4 in modulating Mycobacterium abscessus intracellular survival. The loss of EccB4 was associated with limited secretion of two effector proteins belonging to the WXG-100 family, EsxU and EsxT, and encoded by the esx-4 locus. This prompted us to investigate the function of M. abscessus EsxU and EsxT in vitro and in vivo. Herein, we show that EsxU and EsxT are substrates of ESX-4 and form a stable 1:1 heterodimer that permeabilizes artificial membranes. While expression of esxU and esxT was up-regulated in M. abscessus-infected macrophages, their absence in an esxUT deletion mutant prevented phagosomal membrane disruption while maintaining M. abscessus in an unacidified phagosome. Unexpectedly, the esxUT deletion was associated with a hyper-virulent phenotype, characterised by increased bacterial loads and mortality in mouse and zebrafish infection models. Collectively, these results demonstrate that the presence of EsxU and EsxT dampens survival and persistence of M. abscessus during infection.
ESX 类型 VII 分泌系统是一种跨越分枝杆菌膜的复杂分泌机制，在致病性、营养物质摄取和共轭中发挥重要作用。我们之前报道了 ESX-4 在调节脓肿分枝杆菌细胞内存活中的作用。EccB4 的缺失与属于 WXG-100 家族的两种效应蛋白 EsxU 和 EsxT 的有限分泌有关，这些蛋白由 esx-4 基因座编码。这促使我们研究脓肿分枝杆菌 EsxU 和 EsxT 在体外和体内的功能。在此，我们表明 EsxU 和 EsxT 是 ESX-4 的底物，并形成稳定的 1:1 异二聚体，可使人工膜穿孔。虽然在感染巨噬细胞的脓肿分枝杆菌中，esxU 和 esxT 的表达上调，但在 esxUT 缺失突变体中缺乏它们会阻止吞噬体膜破裂，同时保持未酸化的吞噬体中的脓肿分枝杆菌。出乎意料的是，esxUT 缺失与超毒力表型相关，其特征是在小鼠和斑马鱼感染模型中细菌负荷和死亡率增加。总之，这些结果表明，EsxU 和 EsxT 的存在可减轻感染期间脓肿分枝杆菌的存活和持续存在。
