SCPPPQ1, A Matrix Protein With Structural And Antibacterial Functions

Objectives: The junctional epithelium (JE) is a specialized portion of the gingiva that seals off the tooth supporting tissues from the oral environment via a specialized basal lamina (sBL). This adhesive matrix is composed of three unique proteins - AMTN, ODAM and SCPPPQ1- and Laminin-332 that interact to structure a supramolecular network. We have shown that some periodontal pathogens such as Porphyromonas gingivalis, and related enzymes, alter the supramolecular organization of this critical adhesive matrix by degrading its components, except for SCPPPQ1. The degradation assays we have carried out unexpectedly revealed that SCPPPQ1 may possess antibacterial capacity.
Methods: This study aims to determine the extent of the antimicrobial potential of SCPPPQ1 and characterize its mode of action by exploiting molecular biology and complementary imaging approaches.
Results: Cell counting and FACS analysis showed a decrease in bacterial number for some Gram- and Gram+ bacteria when incubated with SCPPPQ1. In the case of P. gingivalis, there was over 75% reduction in bacterial number. High-resolution electron imaging revealed membrane disruptions, which correlated with internal structural changes. Super-resolution fluorescence microscopy and colloidal-gold immunolabeling showed that the protein formed a beaded coating on the surface of the bacteria. Finally, ongoing studies with various peptides derived from SCPPPQ1 indicate that the antibacterial capacity is sustained by specific regions of the molecule.
Conclusions: These results demonstrate that SCPPPQ1, a structural protein of the sBL, can destroy some bacterial pathogens by attacking their membrane. This unexpected finding highlights the importance of the sBL in periodontal diseases, first by creating a physical barrier and then, when disrupted, by exposing a protein with antibacterial capacity. The integration of peptides derived from SCPPPQ1 in oral hygiene products and targeted application may offer novel therapeutic strategies for the prevention and treatment of periodontal diseases.