RelB-induced Expression of Cot, an MAP3K Family Member, Rescues RANKL-induced Osteoclastogenesis in Alymphoplasia Mice by Promoting NF-κB2 Processing by IKKα

• Published in: The Journal of biological chemistry Vol. 289; no. 11; pp. 7349 - 7361
• Main Authors: Taniguchi, Rei, Fukushima, Hidefumi, Osawa, Kenji, Maruyama, Toshimasa, Yasuda, Hisataka, Weih, Falk, Doi, Takahiro, Maki, Kenshi, Jimi, Eijiro
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 14.03.2014; American Society for Biochemistry and Molecular Biology
• Subjects: Animals; Bone; Bone Marrow Cells - cytology; Cell Biology; Cell Differentiation; Cells, Cultured; Female; Gene Expression Regulation; Glutathione Transferase - metabolism; I-kappa B Kinase - metabolism; Macrophages - cytology; Male; MAP Kinase Kinase Kinases - metabolism; MAP Kinase Signaling System; Mice; Mice, Transgenic; NF-kappa B p52 Subunit - metabolism; NF-kappaB; Osteoclast; Osteoclasts - cytology; Osteogenesis; Phosphorylation; Promoter Regions, Genetic; Proto-Oncogene Proteins - metabolism; Proto-Oncogene Proteins c-akt - metabolism; RANK Ligand - metabolism; Retroviridae - metabolism; Signal Transduction; Transcription Factor RelB - metabolism; Phosphorylation; NF-kappaB; Osteoclast; Bone; Signal Transduction
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M113.538314

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. Background: The alternative NF-κB pathway plays important roles in osteoclastogenesis through an unknown mechanism. Results: RelB-induced Cot expression rescues RANKL-induced osteoclastogenesis in cells isolated from aly/aly mice, which lack active NIK. Conclusion: The overexpression of RelB rescues RANKL-induced osteoclastogenesis by Cot/IKKα-induced NF-κB2 processing in aly/aly cells. Significance: The Akt/Cot/IKKα pathway that is induced by RelB contributes to RANKL-induced osteoclastogenesis by activating the alternative NF-κB pathway.