UpaG, a New Member of the Trimeric Autotransporter Family of Adhesins in UropathogenicEscherichia coli

Abstract

The ability of Escherichia coli to colonize both intestinal and extraintestinal sites is driven by the presence of specific virulence factors, among which are the autotransporter (AT) proteins. Members of the trimeric AT adhesin family are important virulence factors for several gram-negative pathogens and mediate adherence to eukaryotic cells and extracellular matrix (ECM) proteins. In this study, we characterized a new trimeric AT adhesin (UpaG) from uropathogenic E. coli (UPEC). Molecular analysis of UpaG revealed that it is translocated to the cell surface and adopts a multimeric conformation. We demonstrated that UpaG is able to promote cell aggregation and biofilm formation on abiotic surfaces in CFT073 and various UPEC strains. In addition, UpaG expression resulted in the adhesion of CFT073 to human bladder epithelial cells, with specific affinity to fibronectin and laminin. Prevalence analysis revealed that upaG is strongly associated with E. coli strains from the B2 and D phylogenetic groups, while deletion of upaG had no significant effect on the ability of CFT073 to colonize the mouse urinary tract. Thus, UpaG is a novel trimeric AT adhesin from E. coli that mediates aggregation, biofilm formation, and adhesion to various ECM proteins.Pathogenic bacteria often interact with their host through surface proteins referred to as adhesins. Two major classes of adhesins have been described, and both utilize vastly different mechanisms for their assembly at the cell surface. Fimbrial adhesins such as the prototypical type 1 fimbriae of Escherichia coli are composed primarily of a major repeating subunit protein and often contain minor-subunit proteins (including the adhesin) at the tip of the organelle. The biogenesis of these fimbriae is dependent on a highly conserved chaperone-usher system (20,29). Nonfimbrial adhesins are a second class of adherence factors and encompass a diverse range of adhesins that includes the autotransporter (AT) family of proteins. AT proteins are particularly unique in that the information required for receptor recognition and routing and anchorage to the outer membrane is provided by the protein itself (25). Recent studies have identified a new group of nonfimbrial adhesins that have the capacity to form stable trimeric structures on the bacterial cell surface. These adhesins are characterized by a membrane-anchored C-terminal domain that forms a trimeric ␤-barrel pore and facilitates the translocation of a passenger domain (consisting of an extended stalk and an N-terminal head) to the bacterial cell surface via the type V secretion pathway (54, 67).Trimeric AT proteins have been identified from a range of different gram-negative bacterial pathogens. Where characterized, the function of trimeric AT proteins is universally associated with bacterial adherence, and thus they constitute an important group of virulence factors (14). The YadA adhesin from Yersinia enterocolitica represents the best-characterized trimeric AT protein. YadA mediates adherence to host epithelial cells an...

Genome-wide analysis of DNA repeats in Burkholderia cenocepacia J2315 identifies a novel adhesin-like gene unique to epidemic-associated strains of the ET-12 lineage

“…4a). Hep_Hag and HIM are short repeat motifs found in many bacterial invasins and haemagglutinins (Valle et al, 2008). Using the daTAA program, we also predict the presence of an extended signal sequence with a predicted cleavage site between amino acids 1 and 43 (Fig.…”

Innate Transcriptional Networks Activated in Bladder in Response to Uropathogenic Escherichia coli Drive Diverse Biological Pathways and Rapid Synthesis of IL-10 for Defense against Bacterial Urinary Tract Infection

“…The murine model of UTI utilizing female C57BL/6 mice (8-10 wk; The Jackson Laboratory [Bar Harbor, ME], Animal Resources Centre [Canning Vale, WA]) based on transurethral inoculation is described elsewhere (24)(25)(26)(27). IL-10-deficient B6.129P2-Il10 tm1Cgn/J mice (002251) were purchased with appropriate control mice (000664, C57BL/6J) from The Jackson Laboratory.…”

Molecular Defense Mechanisms during Urinary Tract Infection

“…With Auf fimbriae, the nonfimbrial UpaG supports cell aggregation and adhesion to human urothelium. But UpaG is not essential for colonization [22]. These assorted fimbriae may help adherence to host cell avoiding immune mechanisms in different regions of the urinary tract (Table 3).…”