NF-kappaB2 (p100) limits TNF-alpha-induced osteoclastogenesis.

Bone undergoes a continuous cycle of renewal, and osteoclasts--the cells responsible for bone resorption--play a pivotal role in bone homeostasis. This resorption is largely mediated by inflammatory cytokines such as TNF-alpha. In this issue of the JCI, Yao et al. demonstrate that the NF-kappaB precursor protein NF-kappaB2 (p100) acts as a negative regulator of osteoclastogenesis (see the related article beginning on page 3024). TNF-alpha induced a sustained accumulation of p100 in osteoclast precursors, and TNF-alpha-induced osteoclast formation was markedly increased in Nfkb2-/- mice. They also found that TNF receptor-associated factor 3 (TRAF3) is involved in the posttranslational regulation of p100 expression. These results suggest that blockade of the processing of p100 is a novel strategy to treat TNF-alpha-related bone diseases such as RA.