Upregulation of Atrogin-1/FBXO32 is not necessary for cartilage destruction in mouse models of osteoarthritis

In a preliminary study, we found that recently identified catabolic regulators of osteoarthritis (OA), including hypoxia-inducible factor (HIF)-2a and members of the zinc-ZIP8-MTF1 axis, upregulate the E3 ubiquitin ligase, Atrogin-1 (encoded by Fbxo32), in chondrocytes. As the ubiquitination/proteasomal degradation pathways are tightly regulated to modulate the expression of catabolic factors in chondrocytes, we examined the in vivo functions of Atrogin-1 in mouse models of OA.