Bone resorption by osteoclasts is mediated by a typical adhesion structure called the sealing zone or actin ring, whose architecture is based on a belt of podosomes. The molecular mechanisms driving podosome organization into superstructures remain poorly understood to date, in particular at the osteoclast podosome belt. We performed proteomic analyses in osteoclasts and found that the adaptor protein tensin 3 is a partner of Dock5, a Rac exchange factor necessary for podosome belt formation and bone resorption. Expression of tensin 3 and Dock5 concomitantly increase during osteoclast differentiation. These proteins associate with the osteoclast podosome belt but not with individual podosomes, in contrast to vinculin. Super-resolution microscopy revealed that, even if they colocalize in the x-y plane of the podosome belt, Dock5 and tensin 3 differentially localize relative to vinculin in the z-axis. Tensin 3 increases Dock5 exchange activity towards Rac, and suppression of tensin 3 in osteoclasts destabilizes podosome organization, leading to delocalization of Dock5 and a severe reduction in osteoclast activity. Our results suggest that Dock5 and tensin 3 cooperate for osteoclast activity, to ensure the correct organization of podosomes.
The authors declare no competing or financial interests.
A.B. designed the research. H.T. and A.M. designed and performed most of the experiments. A.B. and H.T. wrote the paper. S.U. performed proteomic result analyses. J.M.-L. supervised the 3D-SIM acquisition and processing by H.T. H.T. and S.d.R. analyzed fluorescence images. All contributors discussed the results and commented on the manuscript.
This work was supported by research grants from the Institut National du Cancer [grant number INCa-4361 to A.B.]; the Agence Nationale de la Recherche (ANR) [grant number ANR-2011-BLAN-006 to A.B.]; the Société Française de Rhumatologie (SFR) [grant number 2676 to A.B.]; and the Ligue Contre le Cancer [grant number TABY12312].
Supplementary information available online at http://jcs.biologists.org/lookup/doi/10.1242/jcs.184622.supplemental
- Received December 15, 2015.
- Accepted July 25, 2016.
- © 2016. Published by The Company of Biologists Ltd