The Porphyromonas gingivalis lipid A 1-phosphatase LpxE has unique features and requires a functional type IX secretion system for its activity

Wang, S.; Liu, Y.; Zhang, B.; Aduse-Opoku, J.; Buccafusca, R.; Mastroianni, G.; Machado, P.; Roberts, M.; Curtis, M. A.; Garnett, J.

doi:10.1101/2024.12.20.629629

bioRxiv · 10.1101/2024.12.20.629629

The Porphyromonas gingivalis lipid A 1-phosphatase LpxE has unique features and requires a functional type IX secretion system for its activity

Wang, S.·Liu, Y.·Zhang, B.·Aduse-Opoku, J.·Buccafusca, R.·Mastroianni, G.·Machado, P.·Roberts, M.·Curtis, M. A.·Garnett, J.

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Abstract

Porphyromonas gingivalis is a Gram-negative bacterium that plays a central role in the development of periodontal disease. It uses a type IX secretion system (T9SS) to export a range of virulence factors to the bacterial surface where they are attached to A-LPS, one of the two forms of lipopolysaccharide (LPS) produced in P. gingivalis, and then packaged into outer membrane vesicles (OMVs). We previously showed that 1-P dephosphorylation of the lipid A component of LPS is regulated by the T9SS outer membrane protein (OMP) PorV, and this is linked to membrane destabilisation and OMV blebbing/formation. In this study we aimed to extend this and investigate the role of other T9SS OMPs in OMV biogenesis. We examined gingipain activity, gingipain secretion, A-LPS production, OMV morphology, and lipid A structure in P. gingivalis W50 and T9SS OMP mutant strains, and our results support an essential role for these proteins in type IX secretion. In addition, we produced a lipid A 1-phosphatase ({Delta}lpxE) mutant and show that all T9SS OMPs are required for LpxE activity and correct vesicle formation. LpxE has a unique C-terminal extension, and we propose that a cargo protein exported by the T9SS can directly/indirectly interact with this and regulate LpxE activity. This study provides insight into a new mechanism that links type IX cargo sorting with OMV blebbing, which may also be present in other Bacteroidota that colonise the gut and oral cavity.

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Wang, S., Liu, Y., Zhang, B., Aduse-Opoku, J., Buccafusca, R., Mastroianni, G., Machado, P., Roberts, M., Curtis, M. A., Garnett, J.. 2024-12-21. The Porphyromonas gingivalis lipid A 1-phosphatase LpxE has unique features and requires a functional type IX secretion system for its activity. https://doi.org/10.1101/2024.12.20.629629

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