(613g) Host-Pathogen Interactions at the Tight Junctions: Molecular Insights from Membrane Guided Self-Assembly

Transmembrane proteins of the claudin family assemble in the paracellular space to from tight junctions. Clostridium perfringens is a spore forming opportunistic pathogen that releases enterotoxins (CPE) that disrupt intestinal tight junctions. C. perfringens related enteric infections are the second leading cause of foodborne illness in developed countries. Several members in the claudin family act as receptors for the CPE, and they specifically bind to the C-terminal domain of the toxin (cCPE). CPE initially forms a small complex with receptor claudins that consequently initiates the assembly of a ~450 kDa hexameric pore complex CH-1. The CH-1 complex causes Ca2+ influx and consequently apoptosis. The interaction between the cCPE and claudins are active topics of research for potential translational applications that range from cancer treatment and opening the blood-brain barrier. Crystal structures of the full-length toxin show them to form solvent stabilized trimers in C3 symmetry and more recently, the cCPE complex with claudin-4 was resolved, yet still, the molecular and mechanistic details of the pathogenesis remain to clarified. In this study using multiscale self-assembly simulations, we show that many claudins (including CPE receptor claudin-3/-4), form C3 mediated symmetric interaction in the membrane, which match the receptor orientation for the trimeric CPE toxin. The trimer arrangement presents an electrostatic interaction site that complements the binding pockets in the CPE. We further performed molecular docking and atomistic molecular dynamics to unravel the mechanism of Claudin-CPE interactions. The results from this work will be instrumental in designing translational therapeutics utilizing CPE.