Porphyromonas gingivalis laboratory strains and clinical isolates exhibit different distribution of cell surface and secreted gingipains

Christine A Seers; A Sayeed M Mahmud; N Laila Huq; Keith J Cross; Eric C Reynolds

doi:10.1080/20002297.2020.1858001

Porphyromonas gingivalis laboratory strains and clinical isolates exhibit different distribution of cell surface and secreted gingipains

J Oral Microbiol. 2020 Dec 9;13(1):1858001. doi: 10.1080/20002297.2020.1858001.

Authors

Christine A Seers¹, A Sayeed M Mahmud¹, N Laila Huq¹, Keith J Cross¹, Eric C Reynolds¹

Affiliation

¹ Oral Health Cooperative Research Centre, Melbourne Dental School, Bio21 Institute, The University of Melbourne, Melbourne, Australia.

Abstract

Background: The cell-surface cysteine proteinases RgpA, RgpB (Arg-gingipain), and Kgp (Lys-gingipain) are major virulence factors of P. gingivalis, a keystone pathogen in the development of destructive periodontal disease. The gingipains function as proteinases and transpeptidases utilising small peptides such as glycylglycine as acceptor molecules. However, the characteristics of the gingipains from most P. gingivalis strains have not been determined. Methods: We determined the phenotypes of a panel of P. gingivalis laboratory strains and global clinical isolates with respect to growth on blood agar plus whole-cell and vesicle-free culture supernatant (VFSN) Arg- and Lys-specific proteinase activities. Results: The P. gingivalis isolates exhibited different growth characteristics and hydrolysis of haemoglobin in solid media. Whole-cell Arg-gingipain Vmax varied 5.8-fold and the whole cell Lys-gingipain V_max varied 2.1-fold across the strains. Furthermore, the P. gingivalis strains showed more than 107-fold variance in soluble Arg-gingipain activity in VFSN and more than 371-fold variance in soluble Lys-gingipain activity in VFSN. Glycylglycine and cysteine stimulated Arg- and Lys-specific cleavage activities of all strains. The stimulation by cysteine was in addition to its redox effect consistent with both glycylglycine and cysteine promoting transpeptidation. Conclusion: The global P. gingivalis clinical isolates exhibit different Arg- and Lys‑gingipain activities with substantial variability in the level of soluble proteinases released into the environment.

Keywords: Porphyromonas gingivalis; gingipains; periodontitis; propeptides; protease; proteinase.

Grants and funding

This study was supported by the Australian Government Department of Industry, Innovation and Science Grant 20080108, the National Health & Medical Research Council grant 1081252, an Endeavour Foundation Postgraduate Scholarship 4588_2015, and an Australian Dental Research Foundation grant 34-2013.