Outer membrane vesicle-mediated export of PrtV protease from Vibrio cholerae

Background: Gram-negative bacteria release large amounts of outer membrane vesicles (OMVs) during normal growth. OMVs from pathogenic bacteria are known to carry different biologically active toxins and enzymes into the surrounding environment. We hypothesized that OMVs may therefore be able to mediate the transport of bacterial products into host cells. We present here an analysis of the V. cholerae OMV-associated virulence factor PrtV. Methodology/Principal Findings: We observed that PrtV, a M6 family, zinc-binding metalloprotease, is secreted from V. cholerae wild type strain C6706 into the culture supernatant in association with OMVs. The association of PrtV with OMVs was determined by immunoblotting and electron microscopy using immunogold labeling. In addition, we observed that the PKD-domain(s) of PrtV has a role in the protein’s association with OMVs. We also demonstrated that OMV-associated PrtV was biologically active because HCT8 cells treated with OMVs from the wild type V. cholerae strain C6706 exhibited altered morphology, whereas cells treated with OMVs from the prtV isogenic mutant showed no morphological changes. Moreover, our data suggest that OMV-associated PrtV might be transported into target eukaryotic cells by a vesicle fusion mechanism in association with lipid raft microdomains in the plasma membrane. Conclusion/Significance: Our findings suggest that OMVs can deliver biologically active PrtV into target host cells.