| Co-Investigator(Kenkyū-buntansha) |
SHIBATA Mitsue Nagasaki University School of Dentistry, Departemnt of Pharmacology, Research Associate, 歯学部, 助手 (20274665)
NISHISHITA Kazuhisa Nagasaki University School of Dentistry, Departemnt of Pharmacology, Research Associate, 歯学部, 助手 (20237697)
SAKAI Hideaki Nagasaki University School of Dentistry, Departemnt of Pharmacology, Associate Professor, 歯学部, 助教授 (40225769)
SAKAI Eiko Nagasaki University School of Dentistry, Departemnt of Pharmacology, Research Assistant, 歯学部, 教務職員 (10176612)
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| Research Abstract |
Metalloprotease-disintegrins are a family of transmembrane glycoproteins that play roles in cell-cell interaction and in the processing of the ectodomains of proteins such as tumor necrosis factor α (TNFα). Recently, a membrane-bound TNF family protein designated as osteoclast differentiation factor (ODF, also called RANKL, OPGL and TRANCE) has been identified as an essential factor for normal osteoclastogenesis. ODF is expressed in osteoblastic stromal cells and support osteoclastogenesis by direct cell-cell contact. Under certain condition, the ectodomain of ODF is shed and released into the media. This shedding abolishes cell-cell interaction between stromal cells and bone marrow osteoclast precursors, therefore, may significantly alter the efficiency of osteoclastogenesis. However, the mechanism which controls the shedding of ODF remains to be elucidated. We have developed an assay system to detect soluble ODF (sODF), in which the sODF is captured from culture media or tissue fluid by 6xhistidine-tagged osteoprotegerin (OPG), a decoy receptor of ODF, and detected by immunoblotting using an anti-ODF antibody. When murine calvaria-derived osteoblast/stromal cells were cultured in the presence of vitamin D3, the expression of membrane-bound ODF was significantly elevated. Under these conditions, sODF was not detected. However, when cells were simultaneously treated with phorbol 12-myristate-13-acetate (PMA) or proinflammatory cytokines, such as IL-1, TNFα, IL-17 or IL-11, a significant amount of sODF was detected in the culture media. The shedding of ODF was potently inhibited by KB8301, a metalloprotease inhibitor. Of the metalloprotease-disintegrin family proteins, we identified mRNAs for TACE (ADAM17) and Kuzbanian (ADAM10) in murine calvaria-derived osteoblast/atromal cells. Further studies are necessary to determine which enzymes are involved in the shedding process.
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