STUB1/CYLD targets VDAC1 to regulate osteogenic differentiation in osteoporosis via modulating its ubiquitination and oligomerization

Osteoporosis (OP) constitutes a major global public health burden whose progression is closely linked to mitochondrial dysfunction and disrupted mitophagy homeostasis. This study was designed to characterize the critical function of voltage-dependent anion-selective channel protein 1 (VDAC1), an outer mitochondrial membrane channel protein, in OP and clarify the underlying mechanisms of VDAC1 modulating osteoblastic differentiation of BMSCs via its own ubiquitination and oligomerization under the action of STUB1/CYLD. Bioinformatic analysis of postmenopausal osteoporosis dataset GSE230665 identified VDAC1 as a core node linking mitophagy and osteoporosis. In vivo, AAV9-VDAC1 overexpression vector (AAV9-OE-VDAC1) alleviated osteoporotic phenotypes in ovariectomized (OVX) mice. In vitro, VDAC1 overexpression restored mitophagy and facilitated osteogenic differentiation of hydrogen peroxide (H₂O₂) -damaged bone marrow mesenchymal stem cells (BMSCs). VDAC1's stability is finely tuned by post-translational ubiquitination: STIP1 homology and U-box containing protein 1 (STUB1), an E3 ubiquitin ligase, triggers VDAC1 degradation through K48- and K63-linked ubiquitination, whereas cylindromatosis tumor suppressor (CYLD), a deubiquitinase, stabilizes VDAC1 by removing K63 ubiquitin chains. Oxidative stress induces aberrant VDAC1 oligomerization to suppress mitophagy and osteogenesis, which is rescued by oligomer inhibitor VBIT-4. Upregulated ubiquitination of VDAC1 aggravates its pathological oligomerization, forming a mutually reinforcing vicious cycle. Pharmacological inhibition of these two modifications could delay osteoporosis progression under experimental conditions. Collectively, targeting the STUB1/CYLD-VDAC1 axis to restore mitophagy and rescue impaired osteogenic differentiation of BMSCs may provide a potential research perspective for developing therapeutic strategies against OP.