Tctex-1, a Novel Interaction Partner of Rab3D, Is Required for Osteoclastic Bone Resorption

Abstract

Vesicular transport along microtubules must be strictly regulated to sustain the unique structural and functional polarization of bone-resorbing osteoclasts. However, the molecular mechanisms bridging these vesicle-microtubule interactions remain largely obscure. Rab3D, a member of the Rab3 subfamily (Rab3A/B/C/D) of small exocytotic GTPases, represents a core component of the osteoclastic vesicle transport machinery. Here, we identify a new Rab3D-interacting partner, Tctex-1, a light chain of the cytoplasmic dynein microtubule motor complex, by a yeast two-hybrid screen. We demonstrate that Tctex-1 binds specifically to Rab3D in a GTP-dependent manner and co-occupies Rab3D-bearing vesicles in bone-resorbing osteoclasts. Furthermore, we provide evidence that Tctex-1 and Rab3D intimately associate with the dynein motor complex and microtubules in osteoclasts. Finally, targeted disruption of Tctex-1 by RNA interference significantly impairs bone resorption capacity and mislocalizes Rab3D vesicles in osteoclasts, attesting to the notion that components of the Rab3D-trafficking pathway contribute to the maintenance of osteoclastic resorptive function.

ACKNOWLEDGMENTS

We thank R. Regazzi, S. M. King, M. Zerial, and S. P. Klinken for providing antibodies and cDNA constructs. All microscopy was carried out using facilities at the Centre for Microscopy, Characterization, and Analysis, The University of Western Australia. We thank Karin Eidne for assisting with BRET assays and Adrian Keating for his assistance with the optical profilometer as well as the Australian Research Council for support of this instrument (LE0775499).

This work was supported by the National Health and Medical Research Council of Australia (NHMRC, ID458765) to M.-H.Z., J.X., and N.J.P., the UWA Research Scheme to N.J.P., and the Raine Foundation to N.J.P. N.J.P. is a NHMRC CJ Martin Fellow (ID463911). J.X. is a recipient of the ASBMR Career Enhancement Award. This work was further supported by the NIH (EY11307) and Research To Prevent Blindness to C.-H.S.