RelB-induced expression of Cot, an MAP3K family member, rescues RANKL-induced osteoclastogenesis in alymphoplasia mice by promoting NF-κB2 processing by IKKα.
The alternative nuclear factor-κB (NF-κB) pathway, mainly the RelB-p52 heterodimer, plays important roles in bone metabolism through an unknown mechanism. We have previously reported that alymphoplasia (aly/aly) mice, which lack active NF-κB-inducing kinase (NIK), show mild osteopetrosis due to the inhibition of osteoclastogenesis. p100 retains RelB in the cytoplasm and inhibits RANKL-induced osteoclastogenesis in aly/aly cells. Furthermore, the overexpression of RelB in aly/aly cells rescues RANKL-induced osteoclastogenesis by inducing p100 processing. In contrast, the overexpression of p65 in aly/aly cells has no effect. However, the overexpression of RelB fails to rescue RANKL-induced osteoclastogenesis in the presence of p100ΔGRR, which cannot be processed to p52, suggesting that p100 processing is a key step in RelB-rescued, RANKL-induced osteoclastogenesis in aly/aly cells. In this study, Cot (cancer Osaka thyroid), an MAP3K, was up-regulated by RelB overexpression. Analysis of the Cot promoter demonstrated that p65 and RelB bound to the distal NF-κB-binding site and that RelB but not p65 bound to the proximal NF-κB-binding site in the Cot promoter. The knocking down of Cot expression significantly reduced the RANKL-induced osteoclastogenesis induced by RelB overexpression. The phosphorylation of IKKα at threonine 23 and its kinase activity were indispensable for the processing of p100 and osteoclastogenesis by RelB-induced Cot. Finally, constitutively activated Akt enhanced osteoclastogenesis by RelB-induced Cot, and a dominant-negative form of Akt significantly inhibited it. Taken together, these results indicate that the overexpression of RelB restores RANKL-induced osteoclastogenesis by activation of Akt/Cot/IKKα-induced p100 processing.
From the Division of Molecular Signaling and Biochemistry and.
Rei
R
Taniguchi
Hidefumi
H
Fukushima
Kenji
K
Osawa
Toshimasa
T
Maruyama
Hisataka
H
Yasuda
Falk
F
Weih
Takahiro
T
Doi
Kenshi
K
Maki
Eijiro
E
Jimi
D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology; D002454:Cell Differentiation; D002478:Cells, Cultured; D005260:Female; D005786:Gene Expression Regulation; D005982:Glutathione Transferase / Q000378:metabolism; D051550:I-kappa B Kinase / Q000378:metabolism*; D020930:MAP Kinase Kinase Kinases / Q000378:metabolism*; D020935:MAP Kinase Signaling System; D008264:Macrophages / Q000166:cytology; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D052003:NF-kappa B p52 Subunit / Q000378:metabolism*; D010010:Osteoclasts / Q000166:cytology*; D010012:Osteogenesis; D010766:Phosphorylation; D011401:Promoter Regions, Genetic; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D053245:RANK Ligand / Q000378:metabolism; D012190:Retroviridae / Q000378:metabolism; D015398:Signal Transduction; D051841:Transcription Factor RelB / Q000378:metabolism*
D052003:NF-kappa B p52 Subunit; C498207:Nfkb2 protein, mouse; D011518:Proto-Oncogene Proteins; D053245:RANK Ligand; C497594:Relb protein, mouse; C505689:Tnfsf11 protein, mouse; D051841:Transcription Factor RelB; D005982:Glutathione Transferase; D051057:Proto-Oncogene Proteins c-akt; D051550:I-kappa B Kinase; D020930:MAP Kinase Kinase Kinases; C489843:Map3k8 protein, mouse
Bone; NF-kappaB; Osteoclast; Phosphorylation; Signal Transduction