The RhoGAP activity of myosin IXB is critical for osteoclast podosome patterning, motility, and resorptive capacity.
The RhoGAP activity of myosin IXB is critical for osteoclast podosome patterning, motility, and resorptive capacity.
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DOI：
10.1371/journal.pone.0087402
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发表时间：
2014
期刊：
影响因子：
3.7
通讯作者：
Lee BS
中科院分区：
文献类型：
--
作者：
McMichael BK;Scherer KF;Franklin NC;Lee BS
破骨细胞是单核细胞-巨噬细胞谱系的大型多核细胞，可产生专门的底物粘附复合物以促进其作为骨降解细胞的功能。这些基于肌动蛋白的复合物、足体和密封区的模式和功能由小型 GTPase Rho 调节。肌球蛋白 IXB (Myo9b) 是一种独特的基于肌动蛋白的运动蛋白，包含 RhoGAP 结构域，与其他 RhoGAP 一样，它对 Rho 信号传导具有抑制作用。在这项研究中，Myo9b 在破骨细胞中表达，并作为足体模式和破骨细胞功能的关键调节因子。 SiRNA 介导的 Myo9b 敲低会导致破骨细胞中 Rho 活性增加，但 Rac 活性不会增加。玻璃上破骨细胞的敲低会导致足体模式改变和运动性降低，并且通过添加 Rho 抑制剂可以逆转这种效应。即使封闭区看起来正常，SiRNA 介导的破骨细胞中 Myo9b 表达的抑制也会导致骨吸收能力的急剧丧失。添加 Rho 抑制剂后，这种吸收损失也是可逆的。 Myo9b 水平降低的细胞显示 Src 的错误定位和激活受到抑制，Src 是一种酪氨酸激酶，对破骨细胞肌动蛋白细胞骨架重排和功能具有关键影响。此外，siRNA处理的细胞显示出形成不良的微管网络，并且缺乏微管蛋白乙酰化（微管稳定性的标志）。然而，向 Myo9b 水平受到抑制的细胞短期添加 TNFα 可以克服或规避这些缺陷，并导致密封区尺寸和再吸收能力增加。这些结果表明，Myo9b 的 RhoGAP 活性在调节破骨细胞运动和吸收所需的基于肌动蛋白的结构中发挥着关键作用，并证实 Myo9b 可以充当将 Rho 信号传导与动态肌动蛋白细胞骨架连接的机动化信号分子。
Osteoclasts are large, multinucleated cells of the monocyte-macrophage lineage that generate specialized substrate adhesion complexes to facilitate their function as bone-degrading cells. The patterning and function of these actin-based complexes, podosomes and sealing zones, are regulated by the small GTPase Rho. Myosin IXB (Myo9b) is a unique actin-based motor protein that contains a RhoGAP domain, which, like other RhoGAPs, is inhibitory to Rho signaling. In this study, Myo9b is shown to be expressed in osteoclasts and act as a critical regulator of podosome patterning and osteoclast function. SiRNA-mediated knockdown of Myo9b results in increased activity of Rho but not Rac in osteoclasts. Knockdown in osteoclasts on glass results in altered podosome patterning and decreased motility, and this effect is reversed by addition of a Rho inhibitor. SiRNA-mediated suppression of Myo9b expression in osteoclasts on bone results in a dramatic loss of resorptive capacity even though sealing zones appear normal. This loss of resorption is also reversible with addition of a Rho inhibitor. Cells with diminished Myo9b levels display mislocalization and suppressed activation of Src, a tyrosine kinase with critical effects on osteoclast actin cytoskeletal rearrangement and function. In addition, siRNA-treated cells display poorly formed microtubule networks and a lack of tubulin acetylation, a marker of microtubule stability. However, short-term addition of TNFα to cells with suppressed Myo9b levels overcomes or circumvents these defects and causes increased sealing zone size and resorptive capacity. These results indicate that the RhoGAP activity of Myo9b plays a key role in regulating the actin-based structures necessary for osteoclast motility and resorption, and confirms that Myo9b can act as a motorized signaling molecule that links Rho signaling to the dynamic actin cytoskeleton.
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影响因子：
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作者：
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通讯作者：
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DOI：
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发表时间：
1994-07-05
影响因子：
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