The authors state that they have no conflicts of interest.
Atp6v0d2 Is an Essential Component of the Osteoclast-Specific Proton Pump That Mediates Extracellular Acidification in Bone Resorption†
Article first published online: 29 DEC 2008
Copyright © 2009 ASBMR
Journal of Bone and Mineral Research
Volume 24, Issue 5, pages 871–885, May 2009
How to Cite
Wu, H., Xu, G. and Li, Y.-P. (2009), Atp6v0d2 Is an Essential Component of the Osteoclast-Specific Proton Pump That Mediates Extracellular Acidification in Bone Resorption. J Bone Miner Res, 24: 871–885. doi: 10.1359/jbmr.081239
- Issue published online: 4 DEC 2009
- Article first published online: 29 DEC 2008
- Manuscript Accepted: 22 DEC 2008
- Manuscript Revised: 8 OCT 2008
- Manuscript Received: 30 MAY 2008
- bone resorption;
- extracellular acidification
Bone resorption relies on the extracellular acidification function of vacuolar (V-) ATPase proton pump(s) present in the plasma membrane of osteoclasts. The exact configuration of osteoclast-specific V-ATPases remains largely unknown. In this study, we found that Atp6v0d2 (d2), an isoform of the d subunit in the V-ATPase, showed 5-fold higher expression than that of Atp6v0d1 (d1) in mature osteoclasts, indicating a potential function in osteoclastic bone resorption. When d2 was depleted at an early stage of RANKL-induced osteoclast differentiation in vitro, formation of multinucleated cells was severely impaired. However, depletion of d2 at a late differentiation stage did not affect osteoclast fusion but did abolish the activity of extracellular acidification and bone resorption of mature osteoclasts. We also showed the association of the two tagged-proteins d2 and a3 when co-expressed in mammalian cells with a co-immunoprecipitation assay. Moreover, glutathione-S-transferase (GST) pull-down assay showed the direct interaction of d2 with the N terminus of Atp6v0a3 (a3), which is the functionally identified osteoclast-specific component of V-ATPase. Therefore, our results show the dual function of d2 as a regulator of cell fusion in osteoclast differentiation and as an essential component of the osteoclast-specific proton pump that mediates extracellular acidification in bone resorption.