Decorin-binding adhesins from Borrelia burgdorferi

Area of Science:

• Microbiology
• Molecular Biology
• Immunology

Background:

• Lyme disease is caused by Borrelia burgdorferi, a spirochete transmitted by ticks.
• B. burgdorferi associates with host collagen fibers in the dermis.
• The bacterium binds decorin, a collagen-associated proteoglycan, via expressed decorin-binding proteins (Dbps).

Purpose of the Study:

• To clone and characterize two genes, DbpA and DbpB, encoding decorin-binding proteins.
• To investigate the structure, surface exposure, and binding specificity of DbpA and DbpB.
• To determine the role of Dbps in mediating B. burgdorferi attachment to host extracellular matrix.

Main Methods:

• Gene cloning and sequencing of DbpA and DbpB.
• Circular dichroism (CD) spectroscopy for protein structure analysis.
• Competition binding assays, Western blot, and transmission electron microscopy (TEM) to assess protein function and localization.
• Adhesion assays using coated polystyrene beads and fibroblast-derived extracellular matrix.

Main Results:

• DbpA and DbpB share similar structures but exhibit distinct binding specificities.
• Dbps are surface-exposed proteins on B. burgdorferi.
• DbpA significantly inhibits bacterial attachment to decorin, while DbpB has a minimal effect.
• DbpA-coated beads adhere to decorin-containing extracellular matrix, unlike OspC-coated beads.

Conclusions:

• DbpA and DbpB are surface-exposed adhesins belonging to the microbial surface component-recognizing adhesive matrix molecule (MSCRAMM) family.
• DbpA plays a critical role in mediating B. burgdorferi attachment to the host extracellular matrix, contributing to Lyme disease pathogenesis.