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

• Published in: Redox biology 2023-11, Vol.67, p.102905-102905, Article 102905
• Main Authors: Ward, Josie, Zhang, Suisheng, Sikora, Adam, Michalski, Radoslaw, Yin, Yuting, D'Alessio, Aurora, McLoughlin, Rachel M., Jaquet, Vincent, Fieschi, Franck, Knaus, Ulla G.
• Format: Article
• Language: English
• Subjects: Asparagine; DUOX; Germ-free mice; Humans; Inflammatory bowel disease; Inflammatory Bowel Diseases; Inflammatory Bowel Diseases - genetics; Life Sciences; NADPH oxidase; NADPH Oxidase 1; NADPH Oxidase 1 - genetics; NADPH Oxidases; NADPH Oxidases - genetics; NADPH Oxidases - metabolism; NOX; NOX1 model; Peroxynitrite; Peroxynitrous Acid; Reactive Oxygen Species; Reactive Oxygen Species - metabolism; Research Paper; VEO-IBD
• ISSN: 2213-2317; 2213-2317
• DOI: 10.1016/j.redox.2023.102905

Inflammatory bowel diseases (IBD) are chronic intestinal disorders that result from an inappropriate inflammatory response to the microbiota in genetically susceptible individuals, often triggered by environmental stressors. Part of this response is the persistent inflammation and tissue injury associated with deficiency or excess of reactive oxygen species (ROS). The NADPH oxidase NOX1 is highly expressed in the intestinal epithelium, and inactivating NOX1 missense mutations are considered a risk factor for developing very early onset IBD. Albeit NOX1 has been linked to wound healing and host defence, many questions remain about its role in intestinal homeostasis and acute inflammatory conditions. Here, we used in vivo imaging in combination with inhibitor studies and germ-free conditions to conclusively identify NOX1 as essential superoxide generator for microbiota-dependent peroxynitrite production in homeostasis and during early endotoxemia. NOX1 loss-of-function variants cannot support peroxynitrite production, suggesting that the gut barrier is persistently weakened in these patients. One of the loss-of-function NOX1 variants, NOX1 p. Asn122His, features replacement of an asparagine residue located in a highly conserved HxxxHxxN motif. Modelling the NOX1-p22phox complex revealed near the distal heme an internal pocket restricted by His119 and Asn122 that is part of the oxygen reduction site. Functional studies in several human NADPH oxidases show that substitution of asparagine with amino acids with larger side chains is not tolerated, while smaller side chains can support catalytic activity. Thus, we identified a previously unrecognized structural feature required for the electron transfer mechanism in human NADPH oxidases. [Display omitted] •NOX1 is crucial for microbiota and LPS-dependent intestinal ONOO−/ONOOH generation.•Identification of a catalytically essential HxxxHxxN motif in NOX/DUOX.•NOX1-p22phox Asn122 modelling supports an internal oxygen capture site.