Centre for Orthopaedic Research, School of Surgery, University of Western Australia, Perth 6009, Western Australia, Australia.
Mol Cell Biol. 2011 Apr;31(7):1551-64. doi: 10.1128/MCB.00834-10. Epub 2011 Jan 24.
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.
沿微管的小泡转运必须受到严格调控，以维持破骨细胞独特的结构和功能极性。然而，连接这些囊泡-微管相互作用的分子机制在很大程度上仍不清楚。Rab3D 是小胞吐 Rab 家族（Rab3A/B/C/D）的成员，是破骨细胞囊泡运输机制的核心组成部分。在这里，我们通过酵母双杂交筛选鉴定了一个新的 Rab3D 相互作用伙伴 Tctex-1，它是细胞质动力蛋白微管马达复合物的轻链。我们证明 Tctex-1 以 GTP 依赖性方式特异性结合 Rab3D，并在破骨细胞中与含有 Rab3D 的囊泡共定位。此外，我们提供的证据表明，Tctex-1 和 Rab3D 在破骨细胞中与动力蛋白马达复合物和微管密切相关。最后，通过 RNA 干扰靶向敲低 Tctex-1 显著损害了破骨细胞的骨吸收能力，并使 Rab3D 囊泡定位错误，这证明 Rab3D 运输途径的组成部分有助于维持破骨细胞的吸收功能。
