Characterization of DIP0733, a multi-functional virulence factor of Corynebacterium diphtheriae

Abstract

Corynebacterium diphtheriae is typically recognized as an extracellular pathogen. However, a number of studies revealed its ability to invade epithelial cells, indicating a more complex pathogen-host interaction. The molecular mechanisms controlling and facilitating internalization of Cor. diphtheriae are poorly understood. In this study, we investigated the role of DIP0733 as virulence factor to elucidate how it contributes to the process of pathogen-host cell interaction. Based on in vitro experiments, it was suggested recently that the DIP0733 protein might be involved in adhesion, invasion of epithelial cells and induction of apoptosis. A corresponding Cor. diphtheriae mutant strain generated in this study was attenuated in its ability to colonize and kill the host in a Caenorhabditis elegans infection model system. Furthermore, the mutant showed an altered adhesion pattern and a drastically reduced ability to adhere and invade epithelial cells. Subsequent experiments showed an influence of DIP0733 on binding of Cor. diphtheriae to extracellular matrix proteins such as collagen and fibronectin. Furthermore, based on its fibrinogen-binding activity, DIP0733 may play a role in avoiding recognition of Cor. diphtheriae by the immune system. In summary, our findings support the idea that DIP0733 is a multi-functional virulence factor of Cor. diphtheriae.

Colonization of human epithelial cell lines by Corynebacterium ulcerans from human and animal sources

“…In C. diphtheriae CDC-E8392, DIP0733 is important for adhesion and invasion, and a mutation of the corresponding gene influenced these processes negatively (Antunes et al, 2015). In C. ulcerans, an effect on adhesion and invasion by CULC22_00609, the corresponding homologue of DIP0733, was not observed under the experimental conditions tested.…”

“…In line with this idea, initial sequencing of strains 809 and BR-AD22 (Trost et al, 2011) as well as next-generation sequencing of nine C. ulcerans isolates revealed a number of different virulence factors which might influence colonization by different isolates of this pathogen. Proteins found included PLD, neuraminidase H, endoglycosidase E, SpaDEF-type adhesive pili, diphtheria toxin, a ribosome-binding protein with similarity to Shiga-like toxin, a haemagglutinin protein, a Fic toxin homologue and a RhuM homologue (Trost et al, 2011;Meinel et al, 2014Meinel et al, , 2015Antunes et al, 2015).…”

“…Another example of a putative virulence factor encoded in the C. ulcerans genome is CULC22_00609, a homologue of C. diphtheriae DIP0733, which was found recently to be involved in adhesion to and invasion of epithelial cells (Antunes et al, 2015). The corresponding protein comprises 81 % identity to DIP0733 from strain C. diphtheriae NCTC 13129.…”

Caenorhabditis elegans star formation and negative chemotaxis induced by infection with corynebacteria

“…elegans lives on bacteria but also can be infected by nematopathogenic coryneform bacteria such as Microbacterium and Leucobacter species. The nematodes are a well-established infection model system for many pathogenic bacteria (Clark & Hodgkin, 2014) including C. diphtheriae (Ott et al, 2012;Broadway et al, 2013;Antunes et al, 2015;Santos et al, 2015). Interestingly, in this study, worm-star and Dar formation, morphological changes typical for nematopathogenic bacteria, were observed with both pathogenic and non-pathogenic corynebacteria.…”

“…elegans was applied in a proof-of-principle study for application of this nematode as an infection model for pathogenic corynebacteria (Ott et al, 2012). Later, it was used to investigate the role of pili (Broadway et al, 2013), the DIP0733 protein (Antunes et al, 2015) and a putative tellurite resistance protein (Santos et al, 2015) for virulence of Corynebacterium diphtheriae.…”