Dynamics of membrane nanotubes coated with I-BAR
Dynamics of membrane nanotubes coated with I-BAR
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DOI：
10.1038/srep30054
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发表时间：
2016-07-21
影响因子：
4.6
通讯作者：
Bendix, Poul M.
中科院分区：
文献类型：
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作者：
Barooji, Younes F.;Rorvig-Lund, Andreas;Bendix, Poul M.
膜变形是许多细胞过程（例如丝状伪足和侵袭伪足形成）中的必要步骤，并且已被证明涉及含有 IRSp53-MIM 蛋白家族膜结合域的膜成形蛋白。在重构膜中，膜成形域可以有效地将带负电的膜变形为小管，而不存在任何其他蛋白质。在这里，我们证明来自蛋白质 ABBA 的 IM 结构域（也称为 I-BAR 结构域）形成突出到巨型单层脂质囊泡 (GUV) 中的半柔性纳米管。通过同时量化管强度和管形状，我们找到了纳米管的直径和刚度。 I-BAR 装饰管经量化具有-50 nm 的直径，并且相对于相同直径的无蛋白质管没有表现出硬化。在高蛋白质密度下，管子是不动的，而在较低密度下，管子在 GUV 表面自由扩散。荧光标记的 I-BAR 的漂白实验证实，管的迁移率与 I-BAR 在 GUV 膜上的迁移率相关。最后，在 I-BAR 的低密度下，蛋白质在伸入 GUV 的管内浓缩。这意味着 I-BAR 对负弯曲膜表现出强烈的偏好。
Membrane deformation is a necessary step in a number of cellular processes such as filopodia and invadopodia formation and has been shown to involve membrane shaping proteins containing membrane binding domains from the IRSp53-MIM protein family. In reconstituted membranes the membrane shaping domains can efficiently deform negatively charged membranes into tubules without any other proteins present. Here, we show that the IM domain (also called I-BAR domain) from the protein ABBA, forms semi-flexible nanotubes protruding into Giant Unilamellar lipid Vesicles (GUVs). By simultaneous quantification of tube intensity and tubular shape we find both the diameter and stiffness of the nanotubes. I-BAR decorated tubes were quantified to have a diameter of -50 nm and exhibit no stiffening relative to protein free tubes of the same diameter. At high protein density the tubes are immobile whereas at lower density the tubes diffuse freely on the surface of the GUV. Bleaching experiments of the fluorescently tagged I-BAR confirmed that the mobility of the tubes correlates with the mobility of the I-BAR on the GUV membrane. Finally, at low density of I-BAR the protein upconcentrates within tubes protruding into the GUVs. This implies that I-BAR exhibits strong preference for negatively curved membranes.