PREPROPHASE BAND FORMATION INVOLVES ENDOCYTOSIS MEDIATED BY CLATHRIN-COATED PITS

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 前相带(PPB)是一组微管(MTS)，它标志着植物细胞质膜上细胞板在细胞质分裂的最后阶段融合的位置。通过对与PPB形成相关的内吞和分泌结构的连续切片和电子断层扫描分析，研究了低温保存的洋葱子叶表皮细胞中PPB膜的修饰机理。在这项研究中定量评估的内吞结构包括包被笼蛋白的小凹和小泡，以及结构上相关的非包被小泡。所有这些结构都位于质膜的0.4°m内，含有特征性的深染的货物分子。这些结构之间的因果关系是通过短期治疗布雷菲尔丁A(BFA)，一种分泌和内吞途径抑制剂证明的。在所使用的条件下，只有一小部分高尔基堆叠显示出BFA诱导的结构变化。相反，该处理减少了90%的暗核心内吞小孔，减少了约80%的皮质、笼状蛋白涂层的暗核小泡，以及减少了约67%的皮质、非涂层、暗核心小泡的数量。在PPB形成过程中，与PPB形成区相邻的暗核内吞泡数是质膜非PPB区细胞质中的2.6倍。相反，通过质膜中马蹄形轮廓的数量监测到的分泌活动在两个区域之间是相似的。基于这些发现，我们认为PPB部位质膜的修饰包括通过笼蛋白包裹的凹坑和囊泡去除选定的膜分子。 Karahara，I.，J.sua，T.Murata，L.A.Staehelin和Y.Mineyuki(2006)前期带的形成涉及由氯氰菊酯涂层的凹坑和小泡介导的内吞作用。提交给植物细胞

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The preprophase band (PPB) is an array of microtubules (MTs) that marks the site on the plant cell plasma membrane where the cell plate will fuse during the final stage of cytokinesis. We have investigated the mechanism of PPB membrane modifications in epidermal cells of cryofixed onion cotyledons by analyzing the endocytic and secretory structures associated with PPB formation in serial thin sections and electron tomograms. The endocytic structures that were quantitatively evaluated in this study included clathrin-coated pits and vesicles, as well as structurally related non-coated vesicles. All of these structures were located within 0.4 ¿m of the plasma membrane and contained characteristic darkly staining cargo molecules. A causal relationship between these structures was demonstrated by short-term treatment with brefeldin A (BFA), a secretory and endocytic pathway inhibitor. Under the conditions used, only a fraction of the Golgi stacks showed BFA-induced structural changes. In contrast, the treatment reduced dark-core endocytic pits by >90%, the number of cortical, clathrin-coated, dark-core vesicles by ~80%, and the number of cortical, non-coated, dark-core vesicles by ~67%. During PPB formation, the number of dark-core, endocytic vesicles adjacent to the forming PPB was 2.6-fold higher than in the cytoplasm underlying the non-PPB regions of the plasma membrane. In contrast, the secretory activities, as monitored via the number of horseshoe-shaped profiles in the plasma membrane, were similar between the two regions. Based on these findings, we propose that the modification of the plasma membrane at the site of the PPB involves removal of selected membrane molecules by clathrin-coated pits and vesicles. Karahara, I., J. Suda, T. Murata, L.A. Staehelin and Y. Mineyuki (2006) Preprophase band formation involves endocytosis mediated by chlathrin-coated pits and vesicles. Submitted to Plant Cell