Ranking the role of RANK ligand in apoptosis.

Many members of tumor necrosis factor (TNF) superfamily are characterized by their ability to induce apoptosis once they bind in a homotrimeric manner to their cognate receptors. The receptor activator of nuclear factor-kappaB ligand (RANKL), a member of the TNF superfamily identified seven years ago, was originally described as a factor that induced osteoclastogenesis and dendritic cell survival. Recent observations indicate that a growth inhibitory and apoptosis-inducing activity is associated with RANKL, as is the case for other members of TNF superfamily. This review describes the possible mechanisms of induction of RANKL-induced growth inhibition/apoptosis and discusses the role of various components in RANKL-signaling in this phenomenon, including TNF receptor-associated factor (TRAF)-6, nuclear factor-kappaB (NF-kappaB), c-jun N-terminal kinase JNK), phosphatidylinositol-3 kinase (PI3K).