# Identification and structural characterization of anthrax toxin receptor 2 as the Clostridium perfringens NetF receptor

## TL;DR

This study identifies a receptor for a Clostridium toxin and reveals how it binds to form pores in cell membranes.

## Contribution

The novel contribution is identifying ANTXR2 as the receptor for NetF and its unique lateral binding mechanism.

## Key findings

- ANTXR2 is the receptor for C. perfringens NetF toxin.
- NetF binds laterally to ANTXR2, spanning two domains.
- Cryo-EM structures show how NetF interacts with the receptor to form pores.

## Abstract

Hemolysin β-pore-forming toxins (βPFTs) are key virulence factors of Clostridium perfringens, associated with severe diseases in humans and animals. Yet, the mechanisms by which Clostridium βPFTs recognize and engage specific target cells remain poorly understood. Here, we identify the cellular receptor for C. perfringens necrotizing enteritis toxin F (NetF), a recently discovered toxin implicated in severe enteritis in dogs and foals. We show that NetF binds to the same receptor as anthrax toxin, namely ANTXR2. Using cryo-electron microscopy, we determined the structure of the oligomeric NetF pre-pore as well as the transmembrane pore, both alone and in complex with the extracellular domain of ANTXR2. Unlike anthrax toxin, which binds to the apical MIDAS motif of ANTXR2 – as does the natural ANTXR2 ligand collagen type VI – NetF engages the receptor laterally, spanning both the von Willebrand A and the Ig-like domains. This interaction positions the toxin near the membrane, facilitating contact with membrane lipids and promoting transmembrane pore formation. Our findings uncover key principles of hemolysin βPFT-receptor recognition and advance our understanding of how pathogenic bacteria use these toxins to breach host defenses.

This study identifies ANTXR2 as the cellular receptor for Clostridium perfringens toxin NetF and determines its structure bound to the toxin using cryo-EM, revealing a distinct lateral binding mechanism that facilitates membrane pore formation.