PREPROPHASE BAND FORMATION INVOLVES ENDOCYTOSIS MEDIATED BY CLATHRIN-COATED PITS

这个子项目是许多利用 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 前前期带（PPB）是一组微管（MT），标记植物细胞质膜上细胞板在胞质分裂最后阶段融合的位置。 我们已经研究了PPB膜的修改机制，在表皮细胞冷冻固定的洋葱子叶通过分析与PPB形成在连续的薄片和电子断层扫描的内吞和分泌结构。 在本研究中定量评价的内吞结构包括网格蛋白包被的凹坑和囊泡，以及结构相关的非包被囊泡。 所有这些结构都位于质膜的0.4 μ m范围内，并含有特征性的深染货物分子。 这些结构之间的因果关系被证明是短期治疗与布雷菲德菌素A（BFA），分泌和内吞途径抑制剂。在所使用的条件下，只有一小部分的高尔基体堆栈显示出BFA诱导的结构变化。相比之下，该处理使暗核内吞陷凹减少> 90%，使皮质网格蛋白包被的暗核囊泡的数量减少约80%，并且使皮质非包被的暗核囊泡的数量减少约67%。在PPB形成过程中，暗核心，形成PPB附近的内吞囊泡的数量是2.6倍高于在细胞质中的非PPB区域的质膜。 与此相反，分泌活动，通过在质膜上的马蹄形配置文件的数量进行监测，这两个区域之间是相似的。 基于这些研究结果，我们建议，在PPB的网站的质膜的修改涉及删除选定的膜分子网格蛋白涂层的坑和囊泡。 卡拉哈拉岛J.苏达，T.洛杉矶村田Staehelin和Y. Mineyuki（2006）Preprophase band formation involves endocytosis mediated by chlathrin-coated pit and vesicles.提交给Plant Cell

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