TRIM21 interacts with IκBα and negatively regulates NF-κB activation in Corynebacterium pseudotuberculosis-infected macrophages.

Corynebacterium pseudotuberculosis, a zoonotic intracellular bacteria, is responsible for abscesses and pyogranuloma formation of the infected host, which is essentially a chronic inflammatory response. Tripartite motif-containing protein 21 (TRIM21) negatively regulates pro-inflammatory cytokines production during C. pseudotuberculosis infection, the mechanism of which remains unclear. This study found that C. pseudotuberculosis infection in macrophages induced phosphorylation of IκB and p65. TRIM21 interacted with IκBα by PRY/SPRY domain, stabilizes IκBα and negatively regulates IκBα phosphorylation in macrophages during C. pseudotuberculosis infection. In addition, TRIM21 positively regulates the ubiquitination of IκBα via K48 linkage rather than K63 linkage in C. pseudotuberculosis-infected macrophages. In brief, our research confirmed that TRIM21 negatively regulates canonical NF-κB activation by interacting with IκBα and decreasing IκBα phosphorylation in macrophages during C. pseudotuberculosis infection. Preventing inflammation induced by C. pseudotuberculosis infection through regulation of the NF-κB pathway is a potential way to control this pathogen.