TRAIL inhibits RANK signaling and suppresses osteoclast activation via inhibiting lipid raft assembly and TRAF6 recruitment

Hsiu-Jung Liao,Chien-Sheng Wu,I.-Tsu Chyuan,Ping-Ning Hsu,Hwei-Fang Tsai

doi:10.1038/s41419-019-1353-3

Abstract

Human osteoclast formation from mononuclear phagocyte precursors involves interactions between members of the tumor necrosis factor (TNF) ligand superfamily and their receptors. Recent evidence indicated that TNF-α-related apoptosis-inducing ligand (TRAIL) induces osteoclast differentiation via a TRAF6-dependent signaling pathway; but paradoxically, it inhibits RANK ligand (RANKL)-induced osteoclast differentiation. Although a number of signaling pathways were linked to the RANK and osteoclastogenesis, it is not known how TRAIL regulates RANK signaling. In this study, we demonstrate that TRAIL regulates RANK-induced osteoclastogenesis in terms of the assembly of lipid raft-associated signaling complexes. RANKL stimulation induced recruitment of TRAF6, c-Src, and DAP-12 into lipid rafts. However, the RANKL-induced assembly of lipid raft-associated signaling complexes and TRAF6 recruitment was abolished in the presence of TRAIL. TRAIL-induced dissociation of RANKL-induced lipid raft signaling complexes was reversed by treatment with TRAIL receptor (TRAIL-R) siRNA or an anti-TRAIL-R blocking antibody, indicating that TRAIL mediates suppression of RANKL-induced lipid raft signaling via interactions with TRAIL-R. Finally, we demonstrated that TRAIL suppressed inflammation-induced bone resorption and osteoclastogenesis in a collagen-induced arthritis (CIA) rat animal model. Our results provide a novel apoptosis-independent role of TRAIL in regulating RANK signaling and suppresses osteoclast activation via inhibiting lipid raft assembly and TRAF6 recruitment.

Highlights

Osteoclasts are multinucleated cells, derived from precursors of monocyte/macrophage lineages, and are specialized for bone absorption and remodeling
Previous studies demonstrated that in addition to triggering apoptosis, TNF-α-related apoptosis-inducing ligand (TRAIL) induces osteoclast differentiation in mononuclear phagocyte precursors[17,18], and is able to suppress osteoclastic differentiation induced by RANK ligand (RANKL) plus M-CSF20, suggesting that TRAIL may play a role in regulating osteoclast differentiation, and this may implicate it in osteoimmunology in immune response-associated bone absorption
To further confirm whether RANKL or TRAIL induces osteoclastogenesis signaling through nuclear translocation of NFATc1, the critical transcription factor of osteoclasts, we isolated nuclei to detect the translocation of NFATc1 when cells were treated with RANKL plus M-CSF in the presence or absence of TRAIL

Summary

Introduction

Osteoclasts are multinucleated cells, derived from precursors of monocyte/macrophage lineages, and are specialized for bone absorption and remodeling. RANK provokes biochemical signaling via the recruitment of intracellular TNF receptor-associated factors (TRAFs) after ligand. In addition to RANKL, recent studies demonstrated there are several TNF family molecules which promote osteoclast differentiation, including TNF14, FasL15, decoy receptor 3 (DcR3)[16], and TRAIL17,18, indicating that activated T cells and inflammatory responses can remodel bone homeostasis via these effector molecules. Previous studies demonstrated that in addition to triggering apoptosis, TRAIL induces osteoclast differentiation in mononuclear phagocyte precursors[17,18], and is able to suppress osteoclastic differentiation induced by RANKL plus M-CSF20, suggesting that TRAIL may play a role in regulating osteoclast differentiation, and this may implicate it in osteoimmunology in immune response-associated bone absorption. The mechanism and signaling pathways of how TRAIL regulates RANKL-induced osteoclast differentiation are still not clear

Methods

Results

Conclusion