TNF receptor-associated factor 6 (TRAF6)–p38 mitogen-activated protein kinase (p38 MAPK)–c-Jun N-terminal kinase (JNK)–nuclear factor of activated T-cells cytoplasmic 1 (NFATc1) signaling axis (TRAF6–p38–JNK–NFATc1 axis)

The TRAF6–p38–JNK–NFATc1 signaling axis is a pivotal molecular pathway that governs the differentiation, maturation, and activation of osteoclasts, the primary cells responsible for bone resorption (Takayanagi et al., 2002; NIH). This signaling cascade is typically triggered by the interaction between Receptor Activator of Nuclear Factor-κB Ligand (RANKL) and its receptor RANK, which leads to the recruitment of the adaptor protein TNF receptor-associated factor 6 (TRAF6) (Kobayashi et al., 2001; UniProt). TRAF6 subsequently activates downstream mitogen-activated protein kinases (MAPKs), including p38 and c-Jun N-terminal kinase (JNK), which are essential for the induction and sustained expression of Nuclear factor of activated T-cells cytoplasmic 1 (NFATc1), the master transcriptional regulator of osteoclastogenesis (Ishida et al., 2002; PubMed). Overactivation of this axis is a central driver in the pathogenesis of metabolic bone diseases such as osteoporosis, rheumatoid arthritis, and bone-destructive cancers (Takayanagi et al., 2005; NIH). While drugs like denosumab target the upstream ligand RANKL, experimental inhibitors of TRAF6, p38, and JNK are being explored to more precisely modulate this pathway (PubMed; ResearchGate). However, the broad involvement of these signaling components in systemic immune responses and cell survival poses significant challenges for drug development, particularly regarding potential immunosuppressive side effects and off-target toxicities (NIH; PubMed). Additionally, this axis has been implicated in neuroinflammatory conditions such as neuropathic pain, where it mediates microglial activation (ResearchGate). Understanding the precise regulatory mechanisms of this axis is essential for developing targeted therapies that minimize systemic side effects while effectively treating pathological bone loss (NIH).

Other names

RANKL–RANK–TRAF6–MAPK–NFATc1 pathwayOsteoclastogenic signaling axisTRAF6-MAPK-NFATc1 signaling pathwayRANKL-induced osteoclastogenesis axis

Inhibition of RANKL binding to RANK, blockade of TRAF6 adaptor function or E3 ligase activity, inhibition of p38 or JNK kinase activity, or suppression of NFATc1 nuclear translocation and transcriptional activity.