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Int J Mol Sci. 2017 Sep 25;18(10). pii: E2054. doi: 10.3390/ijms18102054.

Blocking of the Ubiquitin-Proteasome System Prevents Inflammation-Induced Bone Loss by Accelerating M-CSF Receptor c-Fms Degradation in Osteoclast Differentiation.

Author information

1
Department of Microbiology, Laboratory of Bone Metabolism and Control, Yeungnam University College of Medicine, Daegu 42415, Korea. kyungheelee@ynu.ac.kr.
2
Department of Microbiology, Laboratory of Bone Metabolism and Control, Yeungnam University College of Medicine, Daegu 42415, Korea. gsungmi1004@naver.com.
3
Department of Microbiology, Laboratory of Bone Metabolism and Control, Yeungnam University College of Medicine, Daegu 42415, Korea. fairykd@naver.com.
4
Department of Biomedical Engineering, College of Health Science, Institute of Medical Engineering, Yonsei University, Wonju 26493, Korea. hanskim@yonsei.ac.kr.
5
IHBR, Department of Oral Pathology, School of Dentistry, Kyungpook National University, Daegu 41940, Korea. hishin@knu.ac.kr.
6
Department of Microbiology, Laboratory of Bone Metabolism and Control, Yeungnam University College of Medicine, Daegu 42415, Korea. dwjeong@ynu.ac.kr.

Abstract

Anti-osteoporotic activity of a blocker of the ubiquitin-proteasome system, bortezomib, has known to be achieved by directly opposed action in increased bone formation by osteoblasts and in decreased bone destruction by osteoclasts. However, the mechanisms underlying the proteasome blocker inhibition of osteoclast differentiation and function are not fully understood. Here, we observed that proteasome inhibitors, such as MG132 and bortezomib, in osteoclasts accelerated the degradation of c-Fms, a cognate receptor of macrophage colony-stimulating factor (M-CSF), and did not affect the amount of receptor activator of nuclear factor kappa-B (RANK), a receptor of receptor activator of nuclear factor kappa-B ligand (RANKL). c-Fms degradation induced by proteasome inhibitors was controlled by the activation of p38/tumor necrosis factor-alpha converting enzyme (TACE)-mediated regulated intramembrane proteolysis (RIPping). This was validated through the restoration of c-Fms using specific inhibitors of p38 and TACE, and a stimulation of p38-dependent TACE. In addition, c-Fms degradation by proteasome inhibition completely blocked M-CSF-mediated intrinsic signalling and led to the suppression of osteoclast differentiation and bone resorption. In a mouse model with intraperitoneal administration of lipopolysaccharide (LPS) that stimulates osteoclast formation and leads to bone loss, proteasome blockers prevented LPS-induced inflammatory bone resorption due to a decrease in the number of c-Fms-positive osteoclasts. Our study showed that accelerating c-Fms proteolysis by proteasome inhibitors may be a therapeutic option for inflammation-induced bone loss.

KEYWORDS:

bone resorption; c-Fms; osteoclast; proteasome inhibitors

PMID:
28946669
PMCID:
PMC5666736
DOI:
10.3390/ijms18102054
[Indexed for MEDLINE]
Free PMC Article

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