Department of Molecular Genetics, University of Toronto, Toronto, ON M5S 1A8, Canada.
Mol Biol Cell. 2013 May;24(9):1444-53. doi: 10.1091/mbc.E12-12-0878. Epub 2013 Feb 27.
De novo formation of cells in the Drosophila embryo is achieved when each nucleus is surrounded by a furrow of plasma membrane. Remodeling of the plasma membrane during cleavage furrow ingression involves the exocytic and endocytic pathways, including endocytic tubules that form at cleavage furrow tips (CFT-tubules). The tubules are marked by amphiphysin but are otherwise poorly understood. Here we identify the septin family of GTPases as new tubule markers. Septins do not decorate CFT-tubules homogeneously: instead, novel septin complexes decorate different CFT-tubules or different domains of the same CFT-tubule. Using these new tubule markers, we determine that all CFT-tubule formation requires the BAR domain of amphiphysin. In contrast, dynamin activity is preferentially required for the formation of the subset of CFT-tubules containing the septin Peanut. The absence of tubules in amphiphysin-null embryos correlates with faster cleavage furrow ingression rates. In contrast, upon inhibition of dynamin, longer tubules formed, which correlated with slower cleavage furrow ingression rates. These data suggest that regulating the recycling of membrane within the embryo is important in supporting timely furrow ingression.
果蝇胚胎中的细胞从头形成是通过每个核被质膜的凹陷包围来实现的。在分裂沟内陷过程中质膜的重塑涉及胞吐和胞吞途径，包括在分裂沟尖端形成的内吞小管（CFT-小管）。这些小管由 amphiphysin 标记，但除此之外知之甚少。在这里，我们将 GTPase 家族的 septin 鉴定为新的小管标记物。septin 并不均匀地装饰 CFT-小管：相反，新的 septin 复合物装饰不同的 CFT-小管或同一 CFT-小管的不同区域。使用这些新的小管标记物，我们确定所有 CFT-小管的形成都需要 amphiphysin 的 BAR 结构域。相比之下，dynamin 活性优先需要形成含有 septin Peanut 的 CFT-小管亚群。在 amphiphysin 缺失的胚胎中没有小管与更快的分裂沟内陷速率相关。相比之下，当 dynamin 被抑制时，形成了更长的小管，这与较慢的分裂沟内陷速率相关。这些数据表明，调节胚胎内膜的再循环对于支持及时的沟内陷很重要。
