The surface protein Gbp of Fusobacterium nucleatum inhibits osteogenic differentiation by inactivating the Wnt/β-catenin pathway via binding to Annexin A2

Abstract Background Periodontitis is a chronic inflammatory disease that significantly impacts periodontal bone regeneration, yet the distinct biological features of osteoblasts in this condition remain poorly understood. This study aims to elucidate the cellular and molecular mechanisms underlying osteoblast dysfunction in periodontitis, with a focus on the role of Fusobacterium nucleatum (Fn) and its effector protein, D-galactose-binding periplasmic protein (Gbp). Method Single-cell RNA sequencing (scRNA-seq) data from human gingival tissues of periodontitis patients (PD) and healthy controls (HC) were analyzed to identify cellular heterogeneity and molecular pathways. An experimental periodontitis model in mice and primary osteoblast cultures were used to investigate the effects of Fn and Gbp on osteogenic differentiation. Transcriptomic analysis, gene set enrichment analysis (GSEA), and protein-protein interaction (PPI) networks were employed to explore the underlying mechanisms. Results scRNA-seq revealed a reduction in mesenchymal stem cells (MSCs) and osteoblastic lineage cells in PD tissues, with significant downregulation of osteogenic pathways such as Wnt signaling. Fn infection induced alveolar bone destruction in vivo and inhibited osteoblast proliferation, differentiation, and mineralization in vitro. Gbp, an Fn adhesin, similarly impaired osteogenic differentiation by downregulating key osteogenic genes and pathways. Transcriptomic analysis identified shared inflammatory and osteogenic pathways affected by Fn and Gbp, with NF-κB signaling activated and Wnt/β-catenin signaling inhibited. Mechanistically, Gbp interacted with the host protein ANXA2, disrupting the ANXA2/GSK3β complex and inhibiting Wnt/β-catenin signaling, a pivotal route for osteoblast differentiation. ANXA2 knockdown mitigated the Fn/Gbp-induced suppression of osteogenic activity, emphasizing its role in Fn-induced bone loss. Conclusion This study demonstrates that Fn and its effector Gbp disrupt osteogenic differentiation by inactivating the Wnt/β-catenin pathway binding to ANXA2.