The IVVY Motif and Tumor Necrosis Factor Receptor Associated Factor (TRAF) Sites in the Cytoplasmic Domain of the Receptor Activator of Nuclear Factor kappa B (RANK) Cooperate to Induce Osteoclastogenesis [Cell Biology]

August 14th, 2015 by Jules, J., Wang, S., Shi, Z., Liu, J., Wei, S., Feng, X.

RANK activation by RANK ligand (RANKL) mediates osteoclastogenesis by recruiting TRAFs via three cytoplasmic motifs (Motif 1: PFQEP369-373; Motif 2: PVQEET559-564; and Motif 3: PVQEQG604-609) to activate the NF-κB and MAPK signaling pathways. RANK also has a TRAF-independent motif (IVVY535-538) which is dispensable for the activation of TRAF-induced signaling pathways but is essential for osteoclast lineage commitment by inducing the expression of the nuclear factor of activated T-cells, c1 (NFATc1) to regulate osteoclast gene expression. Notably, TNF-/IL-1-mediated osteoclastogenesis requires RANKL assistance, and the IVVY motif is also critical for TNF-/IL-1-mediated osteoclastogenesis by rendering osteoclast genes responsive to these two cytokines. Here, we show that the two types of RANK cytoplasmic motifs have to be on the same RANK molecule to mediate osteoclastogenesis, suggesting a functional cooperation between them. Subsequent osteoclastogenesis assays with TNF or IL-1 revealed that while all three TRAF motifs play roles in TNF-/IL-1-mediated osteoclastogenesis, Motifs 2 and 3 are more potent than Motif 1. Accordingly, inactivation of Motifs 2 and 3 blocks TNF-/IL-1-mediated osteoclastogenesis. Mechanistically, double mutation of Motifs 2 and 3, similarly to inactivation of IVVY motif, abrogates the expression of NFATc1and osteoclast genes in assays reflecting RANK-initiated and TNF-/IL-1-mediated osteoclastogenesis. In contrast, double inactivation of Motifs 2 and 3 did not affect the ability of RANK to activate the NF-κB and MAPK signaling pathways. Collectively, these results indicate that the RANK IVVY motif cooperates with the TRAF-binding motifs to promote osteoclastogenesis, which provide a novel insight into the molecular mechanism of RANK signaling in osteoclastogenesis.
  • Posted in Journal of Biological Chemistry, Publications
  • Comments Off on The IVVY Motif and Tumor Necrosis Factor Receptor Associated Factor (TRAF) Sites in the Cytoplasmic Domain of the Receptor Activator of Nuclear Factor kappa B (RANK) Cooperate to Induce Osteoclastogenesis [Cell Biology]