期刊
CYTOKINE
卷 71, 期 2, 页码 199-206出版社
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
DOI: 10.1016/j.cyto.2014.10.007
关键词
Osteoprotegerin; Osteoclast; Calcium; MAPKs; Podosome
资金
- National Natural Science Foundation of China [31172373, 31302154, 31372495]
- Specialized Research Fund for the Doctoral Program of Higher Education [20113250110003]
- Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD)
- Graduate Innovation Project of Jiangsu Province [CXZZ12_0917]
Osteoclasts are critical for bone resorption and use podosomes to attach to bone matrix. Osteoprotegerin (OPG) is a negative regulator of osteoclast function that can affect the formation and function of podosomes. However, the signaling pathways that link OPG to podosome function have not been well characterized. Therefore, this study examined the roles of intracellular calcium and MAPKs in OPG-induced podosome disassembly in osteoclasts. We assessed the effects of the intracellular calcium chelator Bapta-AM, ERK inhibitor U0126, and p38 inhibitor SB202190 on OPG-treated osteoclast differentiation, adhesion structures, intracellular free Ca2+ concentration and the phosphorylation state of podosome associated proteins (Pyk2 and Src). Mouse monocytic RAW 264.7 cells were differentiated to osteoclasts using RANKL (30 ng/mL) and M-CSF (25 ng/mL). The cells were pretreated with Bapta-AM (5 mu M), U0126 (5 mu M), or SB202190 (10 mu M) for 30 min, followed by 40 ng/mL OPG for 3 h. Osteoclastogenesis, adhesion structure, viability and morphology, intracellular free Ca2+ concentration and the phosphorylation state of Pyk2 and Src were measured by TRAP staining, scanning electron microscopy, real-time cell analyzer, flow cytometry and western blotting, respectively. OPG significantly inhibited osteoclastogenesis, the formation of adhesion structures, and reduced the amount of phosphotylated Pyk2 and Src-pY527, but increased phosphoiylation of Src-pY416. Bapta-AM, U0126, and SB202190 partially restored osteoclast differentiation and adhesion structures. Both Bapta-AM and U0126, but not SB202190, restored the levels of intracellular free Ca2+ concentration, phosphorylated Pyk2 and Src-pY527. All three inhibitors blocked OPG-induced phosphorylation at Src-pY416. These results suggest OPG disrupts the attachment structures of osteoclasts and activates Src as an adaptor protein that competes for the reduced amount of phosphorylated Pyk2 through calcium- and ERK-dependent signaling pathways. p38 MAPK signaling may have a different role in OPG-induced osteoclast retraction. Our findings potentially offer novel insights into the signaling mechanisms downstream of OPG that affect osteoclast attachment to the extracellular matrix. (C) 2014 Elsevier Ltd. All rights reserved.
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