Functional and structural characterization of phospholipase A2 in Porphyromonas gingivalis

Title: Functional and structural characterization of phospholipase A2 in Porphyromonas gingivalis Phospholipases (PLAs) are a group of enzymes that hydrolyze phospholipids producing fatty acids and lipophilic substances. PLAs are ubiquitous, diverse, and play important roles in maintenance of cell membrane integrity, lipid signaling, and regulation of energy homeostasis. PLAs and their metabolites are also implicated in numerous human illnesses, such as autoimmune disease, atherosclerosis, Alzheimer’s disease, and cancer. Interestingly, growing evidence also suggests that there is a positive correlation between PLA activity and periodontitis, e.g., elevated PLA activity is detected in patients’ gingival crevicular fluid (GCF) and recovers to normal levels after treatments; however, little is known about its underpinning pathogenic mechanism. Specifically, the factors that elevate the activity of PLAs in GCF remain unknown. Is this effect caused by particular periodontal pathogens and/or by host responses to the infection? To answer this question, we interrogated the genomes of Porphyromonas gingivalis, a keystone pathogen of periodontitis, and identified a putative PLA in all sequenced isolates, such as PG1879 in W83 strain and PGN1806 in 33277 strain. We carried out biochemical and loss-of-function studies and our preliminary results reveal that PG1879 has PLA2 activity, lyses sheep red blood cells, and is required for P. gingivalis growth in a chemically defined medium (CDM). Building upon these results, we hypothesize that PG1879 is a PLA2 with a unique biochemical and structural feature and contributes to the pathophysiology of P. gingivalis. To test this hypothesis, the following two specific aims are proposed: (1) Delineate the biochemical and structural feature of PG1879 as a PLA2; and (2) Determine the role of PG1879 in the pathophysiology of P. gingivalis. To the best of our knowledge, PLA2 has not been functionally characterized in any oral pathogens and their role in the pathogenesis of periodontitis remains unknown. Completion of this project will elucidate the biochemical and structural feature of PG1879 as a PLA2 and its role in the pathophysiology of P. gingivalis and pave a way to investigate PLA2 in other oral pathogens. In addition, this project will provide me with a comprehensive training on bacterial genetics, biochemistry, cell biology, and structural biology. Project Number: 1F31DE035006-01A1 | Fiscal Year: 2026 | NIH Institute/Center: National Institute of Dental and Craniofacial Research (NIDCR) | Principal Investigator: Katelyn Hustus | Institution: VIRGINIA COMMONWEALTH UNIVERSITY, RICHMOND, VA | Award Amount: $50,914 | Activity Code: F31 | Study Section: Special Emphasis Panel[ZRG1 F07A-W (20)] View on NIH RePORTER: https://reporter.nih.gov/project-details/11318268