Expression of vacuolar H+-ATPase in osteoclasts and its role in resorption |
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Authors: | Takahisa Sasaki Mei-Hua Hong Nobuyuki Udagawa Yoshinori Moriyama |
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Institution: | (1) Department of Oral Anatomy, School of Dentistry, Showa University, 1-5-8 Hatanodai, Shinagawa-ku, 142 Tokyo, Japan;(2) Department of Biochemistry, School of Dentistry, Showa University, 1-5-8 Hatanodai, Shinagawa-ku, 142 Tokyo, Japan;(3) Department of Organic Chemistry and Biochemistry, Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, 567 Ibaraki, Osaka, Japan |
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Abstract: | By means of light- and electron-microscopic immunocytochemistry, we have demonstrated the expression of vacuolar H+-ATPase in mouse osteoclasts. In fully differentiated osteoclasts, intense immunolabeling was observed along the plasma membranes including those of ruffled borders and associated pale vesicles and vacuoles, whereas those of clear zones and basolateral cell surfaces were entirely free of immunoreaction. Specific expression of vacuolar H+-ATPase was also detected over polyribosomes and cisterns of the rough-surfaced endoplasmic reticulum. Multinucleated osteoclastic cells were suspended on dentine slices and cultured for 48 h in the presence or absence of either concanamycin B or bafilomycin A1, specific inhibitors of vacuolar H+-ATPase. Morphometric analysis of co-cultured dentine slices with backscattered electron microscopy revealed that both inhibitors strongly reduced the formation of resorption lacunae in a dose-dependent manner. These results suggest that vacuolar H+-ATPase is produced in the rough-surfaced endoplasmic reticulum, stored in the membrane vesicles, and transported into the ruffled border membranes of osteoclasts, and that this enzyme plays a key role in the creation of an acidic subosteoclastic microenvironment for the demineralization of co-cultered substrates. |
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Keywords: | Bone resorption Osteoclast Vacuolar H+-ATPase Immuno-electron microscopy Mouse (ddY) |
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