Impact of O-glycosylation on the molecular and cellular adhesion properties of the Escherichia coli autotransporter protein Ag43

• Published in: International journal of medical microbiology Vol. 299; no. 6; pp. 389 - 401
• Main Authors: Reidl, Sebastian, Lehmann, Annika, Schiller, Roswitha, Salam Khan, A, Dobrindt, Ulrich
• Format: Journal Article
• Language: English
• Published: Germany Elsevier GmbH 01.08.2009
• Subjects: Adhesins, Bacterial - genetics; Adhesins, Bacterial - metabolism; Adhesins, Escherichia coli; Adhesion; Animals; Antigen 43; Bacterial Adhesion; Biofilms - growth & development; Cell Line; E. coli; Escherichia coli; Escherichia coli - physiology; Escherichia coli Proteins - genetics; Escherichia coli Proteins - metabolism; Extracellular matrix; Extracellular Matrix Proteins - metabolism; Glycosylation; Humans; Infectious Disease; Medical Education; Mice; Protein Binding; Protein Structure, Tertiary; Antigen 43; Extracellular matrix; Glycosylation; Adhesion; E. coli
• ISSN: 1438-4221; 1618-0607
• DOI: 10.1016/j.ijmm.2009.01.001

Abstract 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 (α43 ) 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 α43 domain correlate with different functional properties, we cloned 5 different agn 43 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 α43 domain correlate with increased adhesive properties to proteins of the extracellular matrix such as collagen and laminin. Whereas O-glycosylation of many α43 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.