TFPI is a colonic crypt receptor for TcdB from hypervirulent clade 2 C. difficile

Area of Science:

• Microbiology
• Molecular Biology
• Structural Biology

Background:

• Hypervirulent clade 2 Clostridioides difficile strains cause severe infections, with TcdB being a key virulence factor.
• Clade 2 strains express TcdB variants (TcdB2, TcdB4) that bind to unknown receptors, differing from classic TcdB.

Purpose of the Study:

• To identify the receptor for TcdB4 from hypervirulent C. difficile clade 2 strains.
• To elucidate the structural basis of TcdB-receptor interactions and their role in pathogenesis.

Main Methods:

• CRISPR/Cas9 screening to identify TcdB4 receptors.
• Cryo-electron microscopy (cryo-EM) to determine the structure of the TcdB4-TFPI complex.
• Analysis of TcdB variant receptor-binding regions.

Main Results:

• Tissue factor pathway inhibitor (TFPI) was identified as the receptor for TcdB4.
• Cryo-EM revealed the structure of the TcdB4-TFPI complex, defining a common TcdB receptor-binding region.
• This region classifies TcdB variants into two groups based on receptor preference: Frizzled (FZD) or TFPI.
• TFPI is highly expressed in intestinal glands and protects the colonic epithelium from TcdB2/4.

Conclusions:

• TFPI is established as a colonic crypt receptor for TcdB from clade 2 C. difficile.
• These findings uncover novel mechanisms in Clostridioides difficile infection (CDI) pathogenesis.