TYROBP modulates NFκB phosphorylation and SQSTM1 expression in macrophages during Brucella Abortus LPS infection

Abstract

TYROBP (also known as DAP12), a transmembrane signaling adaptor protein, activates downstream signaling cascades through its immunoreceptor tyrosine-based activation motif (ITAM) by recruiting tyrosine kinase SYK. TYROBP plays an important role in various immune responses, including inflammation and phagocytosis. Although the role of TYROBP in defense against bacterial infections has been partially investigated, its mechanism in Brucella infection is unclear. Using Tyrobp-knockout RAW264.7 macrophages, we demonstrated that gene deletion impaired macrophage phagocytosis. Following B. abortus lipopolysaccharide (LPS) stimulation, Tyrobp deficiency exacerbated mitochondrial damage and enhanced NF-κB phosphorylation. Quantitative proteomics identified SQSTM1 as a TYROBP-interacting partner, and its expression in knockout cells was reduced under LPS treatment conditions in Western blot results (P = 0.0887). RNAi-mediated SQSTM1 depletion phenocopied TYROBP ablation, recapitulating mitochondrial dysfunction and NF-κB hyperactivation. These results suggest that TYROBP inhibits NFκB phosphorylation through upregulation of SQSTM1, affecting macrophage activation and intracellular bacterial clearance. The study also suggests that the TYROBP-SQSTM1-NFκB signaling pathway may play a key role in Brucella infection, providing a new perspective for understanding the mechanism of Brucella infection.