Li S, Shu B, Zhang Y, Li J, Guo J, Wang Y, Ren F, Xiao G, Chang Z, Chen D

Objective: Carboxyl terminus of Hsp70-interacting protein (CHIP or STUB1) is an E3 ligase and regulates the stability of several proteins which are involved in tumor growth and metastasis. However, the role of CHIP in bone growth and bone remodeling in vivo has not been reported. The objective of this study ...

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is to investigate the role and mechanism of CHIP in regulation of bone mass and bone remodeling. Methods: The bone phenotype of Chip(-/-) mice was examined by histology, histomorphometry and micro-CT analyses. The regulatory mechanism of CHIP on the degradation of TRAF6 and the inhibition of NF-κB signaling was examined by immunoprecipitation (IP), western blotting and luciferase reporter assays. Results: In this study, we found that deletion of the Chip gene leads to osteopenic phenotype and increased osteoclast formation. We further found that TRAF6, as a novel substrate of CHIP, is up-regulated in Chip(-/-) osteoclasts. TRAF6 is critical for RANKL-induced osteoclastogenesis. TRAF6 is an adaptor protein which functions as an E3 ligase to regulate the activation of TAK1 and the I-κB kinase (IKK) and is a key regulator of NF-κB signaling. CHIP interacts with TRAF6 to promote TRAF6 ubiquitination and proteasome degradation. CHIP inhibits p65 nuclear translocation, leading to the repression of the TRAF6-mediated NF-κB transcription. Conclusion: CHIP inhibits NF-κB signaling via promoting TRAF6 degradation and plays an important role in osteoclastogenesis and bone remodeling, suggesting that it may be a novel therapeutic target for the treatment of bone loss associated diseases. © 2014 American College of Rheumatology.

Date: Feb. 27, 2014

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