A protein secretion system linked to bacteroidete gliding motility and pathogenesis

Area of Science:

• Microbiology
• Bacterial Pathogenesis
• Molecular Biology

Background:

• Porphyromonas gingivalis causes periodontal disease through secreted proteases called gingipains.
• P. gingivalis lacks conventional protein secretion systems, suggesting unique mechanisms for virulence factor export.
• Previous studies linked proteins like PorT to gingipain secretion.

Purpose of the Study:

• To identify and characterize novel proteins involved in gingipain secretion in P. gingivalis.
• To elucidate the relationship between protein secretion, motility, and virulence in Bacteroidetes.

Main Methods:

• Comparative genome analysis to identify candidate secretion proteins.
• Genetic experiments, including gene disruption and real-time RT-PCR, to assess protein function and regulation.
• Functional analysis of orthologous genes in Flavobacterium johnsoniae.

Main Results:

• Eleven novel proteins (PorK-N, PorW, Sov, PorX, PorY, etc.) were identified as crucial for gingipain secretion.
• Six identified proteins share sequence similarity with Flavobacterium johnsoniae gliding motility proteins.
• PorX and PorY act as regulatory proteins for the secretion system.
• Genes encoding secretion proteins were downregulated in porX and porY mutants.
• Disruption of the F. johnsoniae porT ortholog impaired motility and protein secretion.

Conclusions:

• P. gingivalis employs a unique, non-classical secretion system for gingipains, involving at least 11 proteins.
• This secretion system is interconnected with the bacterial motility apparatus in Bacteroidetes.
• The findings provide insights into the pathogenesis of P. gingivalis and potential therapeutic targets.