Abdel-Nour Mena, Su Han, Duncan Carla, Li Shaopei, Raju Deepa, Shamoun Feras, Valton Marine, Ginevra Christophe, Jarraud Sophie, Guyard Cyril, Kerman Kagan, Terebiznik Mauricio R
Ontario Agency for Health Protection and Promotion, Toronto, ON, Canada.
Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada.
Front Microbiol. 2019 Apr 5;10:604. doi: 10.3389/fmicb.2019.00604. eCollection 2019.
Legionellosis is a severe respiratory illness caused by the inhalation of aerosolized water droplets contaminated with the opportunistic pathogen . The ability of to produce biofilms has been associated with its capacity to colonize and persist in human-made water reservoirs and distribution systems, which are the source of legionellosis outbreaks. Nevertheless, the factors that mediate biofilm formation are largely unknown. In previous studies we reported that the adhesin collagen-like protein (Lcl), is required for auto-aggregation, attachment to multiple surfaces and the formation of biofilms. Lcl structure contains three distinguishable regions: An N-terminal region with a predicted signal sequence, a central region containing tandem collagen-like repeats (R-domain) and a C-terminal region (C-domain) with no significant homology to other known proteins. Lcl R-domain encodes tandem repeats of the collagenous tripeptide Gly-Xaa-Yaa (GXY), a motif that is key for the molecular organization of mammalian collagen and mediates the binding of collagenous proteins to different cellular and environmental ligands. Interestingly, Lcl is polymorphic in the number of GXY tandem repeats. In this study, we combined diverse biochemical, genetic, and cellular approaches to determine the role of Lcl domains and GXY repeats polymorphisms on the structural and functional properties of Lcl, as well as on bacterial attachment, aggregation and biofilm formation. Our results indicate that the R-domain is key for assembling Lcl collagenous triple-helices and has a more preponderate role over the C-domain in Lcl adhesin binding properties. We show that Lcl molecules oligomerize to form large supramolecular complexes to which both, R and C-domains are required. Furthermore, we found that the number of GXY tandem repeats encoded in Lcl R-domain correlates positively with the binding capabilities of Lcl and with the attachment and biofilm production capacity of strains. Accordingly, the number of GXY tandem repeats in Lcl influences the clinical prevalence of strains. Therefore, the number of Lcl tandem repeats could be considered as a potential predictor for virulence in isolates.
军团菌病是一种严重的呼吸道疾病，由吸入被机会性病原体污染的雾化水滴引起。该病原体产生生物膜的能力与其在人造水库和分配系统中定殖和持续存在的能力有关，而这些系统正是军团菌病爆发的源头。然而，介导生物膜形成的因素在很大程度上尚不清楚。在先前的研究中，我们报道了粘附素——类胶原蛋白（Lcl），它是自动聚集、附着于多种表面以及生物膜形成所必需的。Lcl结构包含三个可区分的区域：一个带有预测信号序列的N端区域、一个包含串联类胶原蛋白重复序列（R结构域）的中央区域以及一个与其他已知蛋白质无显著同源性的C端区域（C结构域）。Lcl R结构域编码胶原三肽Gly-Xaa-Yaa（GXY）的串联重复序列，该基序是哺乳动物胶原蛋白分子组织的关键，介导胶原蛋白与不同细胞和环境配体的结合。有趣的是，Lcl在GXY串联重复序列的数量上具有多态性。在本研究中，我们结合了多种生化、遗传和细胞方法，以确定Lcl结构域和GXY重复序列多态性对Lcl的结构和功能特性以及细菌附着、聚集和生物膜形成的作用。我们的结果表明，R结构域对于组装Lcl胶原三螺旋至关重要，并且在Lcl粘附素结合特性方面比C结构域发挥更重要的作用。我们表明，Lcl分子寡聚形成大型超分子复合物，R和C结构域都是必需的。此外，我们发现Lcl R结构域中编码的GXY串联重复序列的数量与Lcl的结合能力以及菌株的附着和生物膜产生能力呈正相关。因此，Lcl中GXY串联重复序列的数量影响菌株的临床流行率。所以，Lcl串联重复序列的数量可被视为军团菌分离株毒力的潜在预测指标。
