Nucleocytoplasmic shuttling of cytoskeletal proteins : molecular mechanism and biological significance

在这项研究中，我们重点关注细胞骨架和细胞核之间的通讯，这是通过细胞骨架成分动态穿梭进入细胞核来实现的。核孔复合体（NPC）作为核质分子转运的疏水选择性门，使小分子（~40kDa）和核转运受体（例如输入蛋白和输出蛋白）能够穿过核膜。然而，NPC的详细选择性特性仍然未知。首先，我们通过对用 Leptomycin B（一种 CRM1 依赖性核输出的选择性抑制剂）处理的细胞进行免疫染色，证明了几种细胞骨架蛋白（如血影蛋白和肌动蛋白）的核细胞质穿梭。共沉淀和定量 PCR 测定揭示了它们在基因表达等基本核功能中的作用。使用洋地黄皂苷处理的细胞质耗尽细胞进行的体外核转运测定清楚地显示了它们自发迁移到细胞核中的有趣特性。由于这些蛋白质在其 3D 结构中具有特征性的两亲基序，因此推测该两亲基序在分子穿过孔的疏水屏障的过程中发挥重要作用。表面疏水性测量使用

In this study we focused on the communication between cytoskeleton and the nucleus, which is achieved by the dynamic shuttling of cytoskeletal components into the nucleus. Nuclear pore complex(NPC) serves as a hydrophobic selective gate of nucleocytoplasmic molecular transport, enabling small molecules(~ 40kDa) and nuclear transport receptors(e. g., importins and exportins) to pass through the nuclear membrane. However, the detailed selectivity property of NPC still remained unknown. First, we demonstrated the nucleocytoplasmic shuttling of several cytoskeletal proteins such as spectrin and actinin by immunostaining of cells treated with Leptomycin B, a selective inhibitor for CRM1-dependent nuclear export. Co-precipitation and quantitative PCR assays revealed their role in fundamental nuclear functions such as gene expression. In vitro nuclear transport assay using digitonin-treated cytoplasm-depleted cells clearly showed their interesting property to spontaneously migrate into the nucleus. Because these proteins possess a characteristic amphiphilic motif in their 3D structure, it was speculated that this amphiphilic motif plays an important role in the molecular passage through the hydrophobic barrier of the pore. Surface hydrophobicity measurement by using