Reidl Sebastian, Lehmann Annika, Schiller Roswitha, Salam Khan A, Dobrindt Ulrich
Julius-Maximilians-Universität Würzburg, Institut für Molekulare Infektionsbiologie, Röntgenring 11, 97070 Würzburg, Germany.
Int J Med Microbiol. 2009 Aug;299(6):389-401. doi: 10.1016/j.ijmm.2009.01.001. Epub 2009 Feb 20.
Antigen 43 (Ag43) represents an entire family of closely related autotransporter proteins in Escherichia coli and has been described to confer aggregation and fluffing of cells, to promote biofilm formation, uptake and survival in macrophages as well as long-term persistence of uropathogenic E. coli in the murine urinary tract. Furthermore, it has been reported that glycosylation of the Ag43 passenger domain (alpha(43)) stabilizes its conformation and increases adhesion to Hep-2 cells. We characterized the role of Ag43 as an adhesin and the impact of O-glycosylation on the function of Ag43. To analyze whether structural variations in the alpha(43) domain correlate with different functional properties, we cloned 5 different agn43 alleles from different E. coli subtypes and tested them for autoaggregation, biofilm formation, adhesion to different eukaryotic cell lines as well as to purified components of the extracellular matrix. These experiments were performed with nonglycosylated and O-glycosylated Ag43 variants. We show for the first time that Ag43 mediates bacterial adhesion in a cell line-specific manner and that structural variations of the alpha(43) domain correlate with increased adhesive properties to proteins of the extracellular matrix such as collagen and laminin. Whereas O-glycosylation of many alpha(43) domains led to impaired autoaggregation and a significantly reduced adhesion to eukaryotic cell lines, their interaction with collagen was significantly increased. These data demonstrate that O-glycosylation is not a prerequisite for Ag43 function and that the different traits mediated by Ag43, i.e., biofilm formation, autoaggregation, adhesion to eukaryotic cells and extracellular matrix proteins, rely on distinct mechanisms.
抗原43（Ag43）代表大肠杆菌中一个密切相关的自转运蛋白家族，据报道它能使细胞聚集和蓬松，促进生物膜形成、巨噬细胞摄取和存活以及尿路致病性大肠杆菌在小鼠尿路中的长期存留。此外，有报道称Ag43乘客结构域（α(43)）的糖基化可稳定其构象并增加对Hep-2细胞的粘附。我们表征了Ag43作为粘附素的作用以及O-糖基化对Ag43功能的影响。为了分析α(43)结构域的结构变异是否与不同的功能特性相关，我们从不同的大肠杆菌亚型中克隆了5个不同的agn43等位基因，并测试它们的自聚集、生物膜形成、对不同真核细胞系以及细胞外基质纯化成分的粘附情况。这些实验使用了非糖基化和O-糖基化的Ag43变体进行。我们首次表明，Ag43以细胞系特异性方式介导细菌粘附，并且α(43)结构域的结构变异与对细胞外基质蛋白如胶原蛋白和层粘连蛋白的粘附特性增加相关。虽然许多α(43)结构域的O-糖基化导致自聚集受损以及对真核细胞系的粘附显著降低，但它们与胶原蛋白的相互作用显著增加。这些数据表明，O-糖基化不是Ag43功能的先决条件，并且Ag43介导的不同特性，即生物膜形成、自聚集、对真核细胞和细胞外基质蛋白的粘附，依赖于不同的机制。
