F-Box and WD repeat domain containing 7 induces infectious osteomyelitis by regulating MYB stability and ubiquitination.

Osteomyelitis is a bone inflammation initiated by invading pathogens. Macrophages and inflammation play essential roles in osteomyelitis. F-Box and WD repeat domain containing 7 (Fbxw7) is a tumour suppressor and E3 ubiquitin ligase. In the present study, the potential roles of Fbxw7 in osteomyelitis were explored. The mRNA level of Fbxw7 was measured in bone marrow cells from patients with osteomyelitis and Staphylococcus aureus (S. aureus)-infected macrophages. The conditional knockout mice with Fbxw7 deficiency in myeloid cells were generated. The expression of interleukin (IL)-6, IL-23a and nitric oxide synthase 2 (Nos2) was measured in S. aureus-infected Fbxw7-deficient bone marrow-derived macrophages (BMDMs). The body weight loss, bacterial burden, bone loss and formation and serum level of IL-6, IL-23 and TNF-α were measured in S. aureus-infected Fbxw7 conditional KO mice. The interacting partners of Fbxw7 were predicted using STRING and the interaction were tested. Elevated expression of Fbxw7 was observed in bone marrow cells from patients with osteomyelitis and in S. aureus-infected macrophages. The expression of IL-6, IL-23a and Nos2 was remarkably suppressed in S. aureus-infected Fbxw7-deficient BMDMs. Fbxw7 conditional knockout mice had less body weight loss, higher bacterial burden, less bone loss and formation and decreased serum level of cytokines. Fbxw7 interacted with MYB. S. aureus-infected Fbxw7-deficient BMDMs had higher level of MYB and less ubiquitination of MYB. Fbxw7 promotes osteomyelitis symptoms by regulating ubiquitination and stability of MYB.