Maurin Justine, Morel Anne, Guérit David, Cau Julien, Urbach Serge, Blangy Anne, Bompard Guillaume
Centre de Recherche de Biologie Cellulaire de Montpellier, CNRS, Montpellier University, Montpellier, France.
BioCampus Montpellier, CNRS, INSERM, Montpellier University, Montpellier, France.
Front Cell Dev Biol. 2021 Nov 18;9:778887. doi: 10.3389/fcell.2021.778887. eCollection 2021.
Osteoclasts are bone resorbing cells that participate in the maintenance of bone health. Pathological increase in osteoclast activity causes bone loss, eventually resulting in osteoporosis. Actin cytoskeleton of osteoclasts organizes into a belt of podosomes, which sustains the bone resorption apparatus and is maintained by microtubules. Better understanding of the molecular mechanisms regulating osteoclast cytoskeleton is key to understand the mechanisms of bone resorption, in particular to propose new strategies against osteoporosis. We reported recently that β-tubulin isotype TUBB6 is key for cytoskeleton organization in osteoclasts and for bone resorption. Here, using an osteoclast model CRISPR/Cas9 KO for Tubb6, we show that TUBB6 controls both microtubule and actin dynamics in osteoclasts. Osteoclasts KO for Tubb6 have reduced microtubule growth speed with longer growth life time, higher levels of acetylation, and smaller EB1-caps. On the other hand, lack of TUBB6 increases podosome life time while the belt of podosomes is destabilized. Finally, we performed proteomic analyses of osteoclast microtubule-associated protein enriched fractions. This highlighted ARHGAP10 as a new microtubule-associated protein, which binding to microtubules appears to be negatively regulated by TUBB6. ARHGAP10 is a negative regulator of CDC42 activity, which participates in actin organization in osteoclasts. Our results suggest that TUBB6 plays a key role in the control of microtubule and actin cytoskeleton dynamics in osteoclasts. Moreover, by controlling ARHGAP10 association with microtubules, TUBB6 may participate in the local control of CDC42 activity to ensure efficient bone resorption.
破骨细胞是参与维持骨骼健康的骨吸收细胞。破骨细胞活性的病理性增加会导致骨质流失，最终导致骨质疏松症。破骨细胞的肌动蛋白细胞骨架组织成一个足体带，它维持着骨吸收装置并由微管维持。更好地理解调节破骨细胞细胞骨架的分子机制是理解骨吸收机制的关键，特别是提出对抗骨质疏松症的新策略。我们最近报道，β-微管蛋白异构体TUBB6对破骨细胞的细胞骨架组织和骨吸收至关重要。在这里，我们使用Tubb6的破骨细胞模型CRISPR/Cas9敲除，表明TUBB6控制破骨细胞中的微管和肌动蛋白动力学。Tubb6敲除的破骨细胞微管生长速度降低，生长寿命延长，乙酰化水平升高，EB1帽变小。另一方面，缺乏TUBB6会增加足体寿命，而足体带则不稳定。最后，我们对破骨细胞微管相关蛋白富集部分进行了蛋白质组学分析。这突出了ARHGAP10作为一种新的微管相关蛋白，其与微管结合似乎受到TUBB6的负调控。ARHGAP10是CDC42活性的负调节剂，参与破骨细胞中的肌动蛋白组织。我们的数据表明，TUBB6在控制破骨细胞中的微管和肌动蛋白细胞骨架动力学中起关键作用。此外，通过控制ARHGAP10与微管的结合，TUBB6可能参与CDC42活性的局部控制，以确保有效的骨吸收。
