Lamin A variants that cause striated muscle disease are defective in anchoring transmembrane actin-associated nuclear lines for nuclear movement
Lamin A variants that cause striated muscle disease are defective in anchoring transmembrane actin-associated nuclear lines for nuclear movement
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DOI：
10.1073/pnas.1000824108
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发表时间：
2011-01-04
影响因子：
11.1
通讯作者：
Gundersen, Gregg G.
中科院分区：
文献类型：
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作者：
Folker, Eric S.;Oestlund, Cecilia;Gundersen, Gregg G.
编码A型核纤层蛋白的LMNA中的突变导致不同的疾病，统称为核纤层蛋白病，其影响不同的组织，包括横纹肌和脂肪组织。核纤层蛋白为细胞核和染色质附着位点提供结构支持，这些功能的缺陷可能导致疾病的发病机制。最近的研究表明，A型核纤层蛋白可能通过核膜nesprin和SUN蛋白介导的细胞核与细胞骨架之间的连接。然而，在哺乳动物细胞中，干扰A型核纤层蛋白并不影响这些蛋白的定位。在这里，我们使用成纤维细胞中的中心体方向，这需要单独的核和中心体定位途径，作为一个模型系统，以了解LMNA突变如何影响核-细胞骨架连接。我们发现导致横纹肌疾病的LMNA突变阻断了肌动蛋白依赖的核运动，而大多数影响脂肪组织的突变抑制了微管依赖的中心体定位。A型核纤层蛋白的遗传缺失或瞬时缺失也阻断了核运动，表明影响肌肉的突变表现出无效表型。缺乏A型核纤层蛋白，或导致横纹肌疾病的变体的表达，并不影响组装nesprin-2G和SUN 2成跨膜肌动蛋白相关核（TAN）线，将细胞核连接到逆行移动的肌动蛋白电缆。然而，Nesprin-2G TAN线不太稳定，并且在核上滑动而不是与其一起移动，表明它们没有锚定。Nesprin-2G TAN系也在SUN 2耗尽的细胞中滑动。我们的研究结果建立了A型核纤层蛋白作为nesprin-2G-SUN 2 TAN系的锚，以允许肌动蛋白对核进行有效的运动和适当的定位。
Mutations in LMNA, which encodes A-type lamins, result in disparate diseases, known collectively as laminopathies, that affect distinct tissues, including striated muscle and adipose tissue. Lamins provide structural support for the nucleus and sites of attachment for chromatin, and defects in these functions may contribute to disease pathogenesis. Recent studies suggest that A-type lamins may facilitate connections between the nucleus and the cytoskeleton mediated by nuclear envelope nesprin and SUN proteins. In mammalian cells, however, interfering with A-type lamins does not affect the localization of these proteins. Here, we used centrosome orientation in fibroblasts, which requires separate nuclear and centrosome positioning pathways, as a model system to understand how LMNA mutations affect nucleus-cytoskeletal connections. We find that LMNA mutations causing striated muscle diseases block actin-dependent nuclear movement, whereas most that affect adipose tissue inhibit microtubule-dependent centrosome positioning. Genetic deletion or transient depletion of A-type lamins also blocked nuclear movement, showing that mutations affecting muscle exhibit the null phenotype. Lack of A-type lamins, or expression of variants that cause striated muscle disease, did not affect assembly of nesprin-2G and SUN2 into transmembrane actin-associated nuclear (TAN) lines that attach the nucleus to retrogradely moving actin cables. Nesprin-2G TAN lines were less stable, however, and slipped over the nucleus rather than moving with it, indicating that they were not anchored. Nesprin-2G TAN lines also slipped in SUN2-depleted cells. Our results establish A-type lamins as anchors for nesprin-2G-SUN2 TAN lines to allow productive movement and proper positioning of the nucleus by actin.