PDF(Pubmed)
Abstract：
The disruption of nucleocytoplasmic transport (NCT) is an important mechanism in neurodegenerative diseases. In the case of C9orf72-ALS, trafficking of macromolecules through the nuclear pore complex (NPC) might get frustrated by the binding of C9orf72-translated arginine-containing dipeptide repeat proteins (R-DPRs) to the Kapβ family of nuclear transport receptors. Besides Kapβs, several other types of transport components have been linked to NCT impairments in R-DPR-expressed cells, but the molecular origin of these observations has not been clarified. Here, we adopt a coarse-grained molecular dynamics model at amino acid resolution to study the direct interaction between polyPR, the most toxic DPR, and various nuclear transport components to elucidate the binding mechanisms and provide a complete picture of potential polyPR-mediated NCT defects. We found polyPR to directly bind to several isoforms of the Impα family, CAS (the specific exporter of Impα) and RanGAP. We observe no binding between polyPR and Ran. Longer polyPRs at lower salt concentrations also make contact with RanGEF and NTF2. Analyzing the polyPR contact sites on the transport components reveals that polyPR potentially interferes with RanGTP/RanGDP binding, with nuclear localization signal (NLS)-containing cargoes (cargo-NLS) binding to Impα, with cargo-NLS release from Impα, and with Impα export from the nucleus. The abundance of polyPR-binding sites on multiple transport components combined with the inherent polyPR length dependence makes direct polyPR interference of NCT a potential mechanistic pathway of C9orf72 toxicity.
摘要：
核质转运（NCT）的破坏是神经退行性疾病的重要机制。在C9orf72-ALS的情况下，通过C9orf72翻译的含精氨酸的二肽重复蛋白（R-DPRs）与核运输受体的Kapβ家族的结合可能会阻碍大分子通过核孔复合物（NPC）的运输。除了Kapβs,其他几种类型的转运成分与R-DPR表达细胞中的NCT损伤有关，但是这些观察的分子起源尚未得到澄清。这里,我们采用氨基酸分辨率的粗粒度分子动力学模型来研究PolyPR之间的直接相互作用，毒性最强的DPR,和各种核转运成分来阐明结合机制，并提供潜在的polyPR介导的NCT缺陷的完整图片。我们发现polyPR直接与Impa家族的几种亚型结合，CAS(Impa的特定出口商)和RanGAP。我们观察到polyPR和Ran之间没有结合。较低盐浓度下的较长polyPR也与RanGEF和NTF2接触。分析转运成分上的polyPR接触位点表明，polyPR可能会干扰RanGTP/RanGDP结合，含有核定位信号(NLS)的货物(cargo-NLS)与Impa结合，随着货物-NLS从Impa释放，并从原子核导出Impα。多种转运成分上的polyPR结合位点的丰度与固有的polyPR长度依赖性相结合，使得NCT的直接polyPR干扰成为C9orf72毒性的潜在机制途径。
