Septin-Mediated Uniform Bracing of Phospholipid Membranes
Septin-Mediated Uniform Bracing of Phospholipid Membranes
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DOI：
10.1016/j.cub.2008.12.030
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发表时间：
2009-01-27
期刊：
影响因子：
9.2
通讯作者：
Takiguchil, Kingo
中科院分区：
文献类型：
--
作者：
Tanaka-Takiguchi, Yohko;Kinoshita, Makato;Takiguchil, Kingo
细胞形状由脂质双层和蛋白质聚合物的底层网络之间的相互作用决定[1]。我们探讨了未知的决定因素参与细胞形态的因素，转化磷脂为基础的脂质体（直径5-20 μ m）。通过暗场光学观察到的未标记的巨大脂质体在水性悬浮液中是亚稳定的。与此相反，脂质体强有力地突出均匀的小管后，立即加入脑提取物的悬浮液。当脂质体中含有PIP或PIP 2时，大大促进了脂质体反应。脑提取物的生化分析表明，异聚复合物的septins，一个家庭的聚合GTP/GDP结合蛋白，负责膜的转变。超微结构分析表明，每个膜小管（直径0.43 +/- 0.079 μ m）由隔蛋白丝的圆周阵列支撑。尽管膜下隔蛋白组装体与从酵母到哺乳动物的不同皮层形态发生相关[2-5]，但隔蛋白-膜相互作用的生物物理基础在很大程度上仍然未知。此外，在细胞中的快速隔蛋白重塑与它们在体外的缓慢自组装之间存在生物化学差异[6，7]。我们独特的实验系统首次证明了这种膜促进的快速Septin组装应该为表征这些过程提供重要线索。
Cell shape is determined by the interplay between the lipid bilayer and the underlying network of protein polymers [1]. We explored unknown determinants involved in cell morphogenesis as factors that transform phospholipid-based liposomes (diameter 5-20 mu m). Unlabeled giant liposomes, observed through dark-field optics, were metastable in an aqueous suspension. In contrast, liposomes robustly protruded uniform tubules immediately after the addition of a brain extract to the suspension. The tubulation reaction was greatly facilitated when the liposomes contained PIP or PIP2. Biochemical analysis of the brain extract revealed that heteromeric complexes of septins, a family of polymerizing GTP/GDP-binding proteins, are responsible for the membrane transformation. Ultrastructural analysis established that each membrane tubule (diameter 0.43 +/- 0.079 mu m) is braced by a circumferential array of septin filaments. Although submembranous septin assemblies are associated with diverse cortical morphogenesis from yeast to mammals [2-5], the biophysical basis for the septin-membrane interplay remains largely unknown. Further, there is a biochemical discrepancy between the fast septin remodeling in cells and their slow self-assembly in vitro [6, 7]. This membrane-facilitated fast septin assembly demonstrated for the first time by our unique experimental system should provide important clues to characterize these processes.