Protein Kinase CK2 Acts as a Molecular Brake to Control NADPH Oxidase 1 Activation and Colon Inflammation

BACKGROUND & AIMS:NADPH oxidase 1 (NOX1) hasemerged as a prime regulator of intestinal mucosa immunityand homeostasis. Dysregulation of NOX1 may cause inflam-matory bowel disease (IBD). It is not clear how NOX1 is regu-latedin vivounder inflammatory conditions. We studied therole of CK2 in this process.& nbsp;METHODS:The NOX1 organizer subunit, NADPH oxidase orga-nizer 1 (NOXO1), was immunoprecipitated from cytokine-treated colon epithelial cells, and bound proteins were identi-fied by mass spectrometry analysis. Sites on NOXO1phosphorylated by CK2 were identified by nanoscale liquidchromatography coupled to tandem mass spectrometry. NOX1activity was determined in colon epithelial cells and colonoids inthe presence or absence of CX-4945, a CK2 specific inhibitor.Acute colitis was induced by administration of trini-trobenzenesulfonic acid in mice treated or not with CX-4945.Colon tissues were analyzed by histologic examination, quanti-tative polymerase chain reaction, and Western blots. CK2 activ-ity, markers of inflammation, and oxidative stress were assessed.& nbsp;RESULTS:We identified CK2 as a major partner of NOXO1 incolon epithelial cells under inflammatory conditions. CK2 directlybinds NOXO1 at the C-terminus containing the Phox homologydomain and phosphorylates NOXO1 on several sites. CX-4945increased ROS generation by NOX1 in human colon epithelialcells and organoids. Strikingly, CK2 activity was reduced in tri-nitrobenzenesulfonic acid-induced acute colitis, and CX-4945exacerbated colitis inflammation as shown by increased levelsof CXCL1, ROS generation, lipid peroxidation, and colon damage.& nbsp;CONCLUSIONS:The ubiquitous protein kinase CK2 limits NOX1activity via NOXO1 binding and phosphorylation in colonicepithelial cells and lessens experimental colitis. Loss of CK2activity during acute colitis results in excessive ROS production,contributing to the pathogenesis. Strategies to activate CK2could be an effective novel therapeutic approach in IBD.

Automated summary

CK2 is a major partner of NOXO1 in colon epithelial cells under inflammatory conditions. CK2 limits NOX1 activity by directly binding and phosphorylating NOXO1. Reduced CK2 activity during acute colitis results in excessive ROS production and contributes to the pathogenesis.