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首页> 外文期刊>Proceedings of the National Academy of Sciences of the United States of America >Electron Tomography Of Early Melanosomes: Implications For Melanogenesis And The Generation Of Fibrillar Amyloid Sheets
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Electron Tomography Of Early Melanosomes: Implications For Melanogenesis And The Generation Of Fibrillar Amyloid Sheets

机译：早期黑素体的电子断层扫描：对黑色素生成和原纤维淀粉样片的产生的影响。

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摘要

Melanosomes are lysosome-related organelles (LROs) in which mel-anins are synthesized and stored. Early stage melanosomes are characterized morphologically by intralumenal fibrils upon which melanins are deposited in later stages. The integral membrane protein Pmel17 is a component of the fibrils, can nucleate fibril formation in the absence of other pigment cell-specific proteins, and forms amyloid-like fibrils in vitro. Before fibril formation Pmel17 traffics through multivesicular endosomal compartments, but how these compartments participate in downstream events leading to fibril formation is not fully known. By using high-pressure freezing of MNT-1 melanoma cells and freeze substitution to optimize ultrastruc-tural preservation followed by double tilt 3D electron tomography, we show that the amyloid-like fibrils begin to form in multivesicular compartments, where they radiate from the luminal side of intralumenal membrane vesicles. The fibrils in fully formed stage II premela-nosomes organize into sheet-like arrays and exclude the remaining intralumenal vesicles, which are smaller and often in continuity with the limiting membrane. These observations indicate that premelano-some fibrils form in association with intralumenal endosomal membranes. We suggest that similar processes regulate amyloid formation in pathological models.
机译：黑素体是与溶酶体相关的细胞器（LRO），其中合成并储存了黑色素。早期黑素体在形态上以腔内原纤维为特征，黑色素在后期沉积在其上。完整的膜蛋白Pmel17是原纤维的组成部分，可以在没有其他色素细胞特异性蛋白的情况下使原纤维成核，并在体外形成淀粉样蛋白样原纤维。在原纤维形成之前，Pmel17通过多囊泡内体区室运输，但是这些区室如何参与导致原纤维形成的下游事件尚不完全清楚。通过使用MNT-1黑色素瘤细胞的高压冷冻和冷冻替代来优化超微结构保存，然后进行双倾斜3D电子断层扫描，我们显示淀粉样蛋白原纤维开始在多囊腔室中形成，并从腔中放射出腔内膜囊泡的一侧。完全形成的II期前黑素体前体的原纤维组织成片状阵列，并排除了剩余的管腔内囊泡，它们较小且通常与限制膜连续。这些观察结果表明前黑素体-一些原纤维与腔内的内体膜结合形成。我们建议在病理模型中类似的过程调节淀粉样蛋白的形成。

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