TRAF1 Promotes Osteoclastogenesis by Enhancing Metabolic Adaptation to Oxidative Phosphorylation in an AKT-dependent Manner

Tumor necrosis factor receptor-associated factor 1 (TRAF1) is a crucial signaling adaptor involved in multiple cellular events. However, its role in regulating osteoclastogenesis and energy metabolism remains unclear. Here, we report that TRAF1 promotes osteoclastogenesis and oxidative phosphorylation (OXPHOS). Employing RNA sequencing, we found that TRAF1 is markedly upregulated during osteoclastogenesis and is positively associated with osteoporosis. TRAF1 knockout inhibits osteoclastogenesis and increases bone mass in both normal and ovariectomized adult mice without affecting bone mass in childhood. Furthermore, TRAF1 promotes osteoclast OXPHOS by increasing the phosphorylation level of AKT. Mechanistically, TRAF1 functions to inhibit TRAF2-induced ubiquitination of Gβl, a known activator of AKT, and further upregulates AKT phosphorylation. Rescue experiments revealed that the inhibitory effects of TRAF1 knockout on osteoclastogenesis, OXPHOS, and bone mass are dependent on AKT. Collectively, our findings uncover a previously unrecognized function of TRAF1 in regulating osteoclastogenesis and energy metabolism, and establish a novel TRAF1-AKT-OXPHOS axis in osteoclasts.