AdpC Is aPrevotella intermedia17 Leucine-Rich Repeat Internalin-Like Protein

Abstract

The oral bacterium Prevotella intermedia attaches to and invades gingival epithelial cells, fibroblasts, and endothelial cells. Several genes encoding proteins that mediate both the adhesion and invasion processes are carried on the genome of this bacterium. Here, we characterized one such protein, AdpC, belonging to the leucine-rich repeat (LRR) protein family. Bioinformatics analysis revealed that this protein shares similarity with the Treponema pallidum LRR (LRR TP ) family of proteins and contains six LRRs. Despite the absence of a signal peptide, this protein is localized on the bacterial outer membrane, indicating that it is transported through an atypical secretion mechanism. The recombinant form of this protein (rAdpC) was shown to bind fibrinogen. In addition, the heterologous host strain Escherichia coli BL21 expressing rAdpC (V2846) invaded fibroblast NIH 3T3 cells at a 40-foldhigher frequency than control E. coli BL21 cells expressing a sham P. intermedia 17 protein. Although similar results were obtained by using human umbilical vein endothelial cells (HUVECs), only a 3-fold-increased invasion of V2846 into oral epithelial HN4 cells was observed. Thus, AdpC-mediated invasion is cell specific. This work demonstrated that AdpC is an important invasin protein of P. intermedia 17.

Interaction of Prevotella intermedia Strain 17 Leucine-Rich Repeat Domain Protein AdpF with Eukaryotic Cells Promotes Bacterial Internalization

“…Since it is associated with a human pathogen, such a protein would be expected to play a role in host-pathogen interactions. Our work showed that AdpF binds to fibronectin; thus, its specificity is similar to that of AdpB, previously characterized by our laboratory (25). The mechanism by which fibronectin, a 440-kDa mosaic glycoprotein, stimulates the internalization of bacteria by mammalian cells is not clear.…”

“…These results suggest that the effect may not be cell specific. Previously, we have shown that the internalin-like P. intermedia 17 protein AdpC confers an invasive phenotype on E. coli cells expressing the protein (25). However, this effect was observed only using endothelial HUVECs and NIH 3T3 cells and was not detected with the oral epithelial HN4 cell line.…”

“…This is the second LRR domain protein identified in P. intermedia 17 that plays a role in the internalization of the bacterium (25,33). Unlike the previously characterized AdpC protein, which acts on the bacterium and confers an invasive phenotype when expressed heterologously in E. coli, AdpF alters the host cells to more readily take up invasive bacteria.…”

“…Interestingly, we have also identified several genes coding for LRR domain proteins (2). One of the gene products, AdpC, has been shown to be a cell-surface-exposed outer membrane protein that confers an invasive phenotype on Escherichia coli cells expressing the protein (25). Here, we characterized another LRR domain protein, AdpF, encoded by the PI0493 gene (Los Alamos annotation, The Bioinformatics Resource for Oral Pathogens [BROP] at genome.brop.org), that binds fibronectin and promotes the invasion of P. intermedia 17 into a variety of host cells.…”

<em>Porphyromonas gingivalis</em> as a Model Organism for Assessing Interaction of Anaerobic Bacteria with Host Cells

“…In summary, described are a few simple protocols that can be used to examine host-pathogen interaction for anaerobic bacteria. These protocols have also been used to assess the effect of bacterial internalins, proteins promoting bacterial invasion 40 , as well as surrogate non-invasive bacteria expressing a protein conferring invasive property on the bacteria 47 .…”