VEO-IBD NOX1 variant highlights a structural region essential for NOX/DUOX catalytic activity

Area of Science:

• Gastroenterology
• Molecular Biology
• Immunology

Background:

• Inflammatory bowel diseases (IBD) involve chronic intestinal inflammation linked to host-microbiota interactions and reactive oxygen species (ROS).
• The NADPH oxidase NOX1, expressed in the intestinal epithelium, is implicated in IBD pathogenesis, with inactivating mutations being an early-onset IBD risk factor.

Purpose of the Study:

• To elucidate the specific role of NOX1 in intestinal homeostasis and inflammation.
• To identify the molecular mechanisms underlying NOX1's function and the impact of its mutations on gut barrier integrity.

Main Methods:

• In vivo imaging, inhibitor studies, and germ-free conditions were employed to assess NOX1 function.
• Structural modeling of the NOX1-p22^phox complex and functional assays on human NADPH oxidases were performed.

Main Results:

• NOX1 was confirmed as essential for superoxide generation, driving microbiota-dependent peroxynitrite production in homeostasis and early endotoxemia.
• Loss-of-function NOX1 variants, like p.Asn122His, impair peroxynitrite production, suggesting a weakened gut barrier in affected individuals.
• A conserved HxxxHxxN motif pocket near the heme is critical for NOX1 electron transfer, with specific amino acid substitutions impacting catalytic activity.

Conclusions:

• NOX1 plays a vital role in maintaining gut barrier function through microbiota-dependent peroxynitrite production.
• Specific structural features within NOX1 are essential for its catalytic activity, and mutations can compromise gut health, contributing to IBD development.