Cryo-EM Structures of Clostridium perfringens Enterotoxin Bound to its Human Receptor, Claudin-4

Area of Science:

• Microbiology
• Structural Biology
• Biochemistry

Background:

• Pathogenic Clostridium perfringens produces enterotoxin (CpE), a major cause of severe gastrointestinal diseases in humans and animals.
• CpE targets claudins, proteins forming tight junctions in the intestinal epithelium, disrupting normal function.
• CpE hijacks claudins to form small complexes, which are precursors to cytotoxic beta-barrel pores.

Purpose of the Study:

• To determine the high-resolution structures of CpE in complex with its human receptor, claudin-4.
• To elucidate the molecular mechanism of CpE-claudin complex formation and subsequent pore assembly.
• To identify strategies for preventing CpE-induced cytotoxicity and treating associated gastrointestinal diseases.

Main Methods:

• Cryogenic electron microscopy (cryo-EM) was used to obtain structures of CpE-claudin-4 complexes at 4.0 and 2.8 Å resolution.
• Structural analysis focused on the architecture of the small complex, binding interfaces, and CpE-induced alterations in claudin-4.
• Biophysical insights into the transition from small complexes to beta-barrel pores were investigated.

Main Results:

• The structures reveal the detailed architecture of the claudin-4/CpE small complex, including key binding residues.
• The orientation of CpE relative to the intestinal membrane and CpE-induced structural changes in claudin-4 were resolved.
• The study provides evidence for kinetically trapped states of the complex and alludes to the mechanism of beta-barrel pore formation, involving trypsin.

Conclusions:

• This work provides unprecedented structural detail of claudin-bound CpE, clarifying its pore assembly mechanism.
• Understanding the CpE-claudin interaction and pore formation pathway opens avenues for developing novel therapeutics.
• Targeting CpE pore assembly presents a promising strategy for combating CpE-mediated gastrointestinal disorders.