From Gut to Systemic Circulation: Molecular Strategies of Botulinum Neurotoxin Complexes

Area of Science:

• Microbiology
• Toxicology
• Structural Biology

Background:

• Botulinum neurotoxins (BoNTs) are potent toxins requiring co-produced nontoxic proteins for oral delivery.
• Nontoxic proteins facilitate BoNT survival in the gastrointestinal tract and systemic dissemination.
• Previous studies identified interactions between BoNTs, nontoxic non-hemagglutinin (NTNH) factors, OrfXs/P47, and hemagglutinins (HAs).

Purpose of the Study:

• To synthesize recent findings on the molecular basis of BoNT-nontoxic protein interactions.
• To elucidate the mechanisms of NTNH anchoring to HA70 and OrfX2.
• To highlight divergent pathways enhancing oral toxicity and discuss intestinal absorption mechanisms.

Main Methods:

• Review of recent structural and functional studies.
• Analysis of molecular interactions between BoNTs and associated nontoxic proteins.
• Synthesis of current perspectives on intestinal absorption.

Main Results:

• NTNH specifically anchors to the HA70 triskelion-like element.
• NTNH also binds to the host protease-activated form of OrfX2.
• These interactions reveal divergent pathways that enhance oral toxicity.

Conclusions:

• The molecular basis for NTNH anchoring to HA70 and OrfX2 has been elucidated.
• Divergent binding pathways contribute to enhanced oral toxicity of BoNTs.
• Understanding these mechanisms provides insights into BoNT absorption from the intestine.