Centre for Orthopaedic Research, School of Surgery, The University of Western Australia, Nedlands, WA, Australia.
J Bone Miner Res. 2013 Jan;28(1):119-34. doi: 10.1002/jbmr.1725.
Osteoclastic bone resorption requires strict interplay between acidified carrier vesicles, motor proteins, and the underlying cytoskeleton in order to sustain the specialized structural and functional polarization of the ruffled border. Cytoplasmic dynein, a large processive mechanochemical motor comprising heavy, intermediate, and light chains coupled to the dynactin cofactor complex, powers unilateral motility of diverse cargos to microtubule minus-ends. We have recently shown that regulators of the dynein motor complex constitute critical components of the osteoclastic bone resorptive machinery. Here, by selectively modulating endogenous dynein activity, we show that the integrity of the dynein-dynactin motor complex is an essential requirement for both osteoclast formation and function. Systematic dissection of the osteoclast dynein-dynactin complex revealed that it is differentially localized throughout RANKL-induced osteoclast formation and activation, undergoing microtubule-coupled reorganization upon the establishment of cellular polarization. In osteoclasts actively resorbing bone, dynein-dynactin intimately co-localizes with the CAP-Gly domain-containing microtubule plus-end protein CLIP-170 at the resorptive front, thus orientating the ruffled border as a microtubule plus-end domain. Unexpectedly, disruption of the dynein-dynactin complex by exogenous p50/dynamitin expression retards osteoclast formation in vitro, owing largely to prolonged mitotic stasis of osteoclast progenitor cells. More importantly, loss of osteoclastic dynein activity results in a drastic redistribution of key intracellular organelles, including the Golgi and lysosomes, an effect that coincides with impaired cathepsin K secretion and diminished bone resorptive function. Collectively, these data unveil a previously unrecognized role for the dynein-dynactin motor complex in osteoclast formation and function, serving not only to regulate their timely maturation but also the delivery of osteolytic cargo that is essential to the bone resorptive process.
破骨细胞的骨吸收需要酸化载体囊泡、运动蛋白和底层细胞骨架之间的严格相互作用，以维持皱褶缘的特殊结构和功能极化。细胞质动力蛋白是一种由重链、中间链和轻链与动力蛋白辅助因子复合物偶联而成的大型、连续的机械化学马达，为各种货物向微管负端的单向运动提供动力。我们最近表明，动力蛋白马达复合物的调节剂是破骨细胞骨吸收机制的关键组成部分。在这里，通过选择性地调节内源性动力蛋白活性，我们表明动力蛋白-动力蛋白辅助因子复合物的完整性是破骨细胞形成和功能的必要条件。对破骨细胞动力蛋白-动力蛋白辅助因子复合物的系统剖析表明，它在 RANKL 诱导的破骨细胞形成和激活过程中具有不同的定位，在细胞极化建立时，经历与微管偶联的重组。在积极吸收骨的破骨细胞中，动力蛋白-动力蛋白辅助因子复合物与含有 CAP-Gly 结构域的微管正端蛋白 CLIP-170 密切共定位在吸收前沿，从而将皱褶缘定向为微管正端结构域。出乎意料的是，通过外源性 p50/dynamitin 表达破坏动力蛋白-动力蛋白辅助因子复合物会延迟体外破骨细胞的形成，这主要归因于破骨细胞前体细胞的有丝分裂停滞时间延长。更重要的是，破骨细胞动力蛋白活性的丧失导致关键细胞内细胞器的剧烈重分布，包括高尔基体和溶酶体，这种效应与组织蛋白酶 K 分泌受损和骨吸收功能降低一致。总之，这些数据揭示了动力蛋白-动力蛋白辅助因子复合物在破骨细胞形成和功能中的一个以前未被认识的作用，不仅调节它们的及时成熟，而且还调节对骨吸收过程至关重要的溶骨性货物的输送。
