Mechanisms of Golgi Vesiculation during Mitosis

描述(申请人提供)：在有丝分裂的哺乳动物细胞中，高尔基体池周围相互连接的堆叠是碎裂的。为什么这些膜在其组织结构上经历了如此剧烈的变化，通过什么机制？高尔基体膜在有丝分裂过程中是否与内质网融合，从而利用内质网将其传递到子细胞？我们最近的发现表明，高尔基体膜在有丝分裂过程中不与内质网融合。这些发现解决了一个长期存在的争议。我们发现，抑制高尔基体碎裂可以阻止进入有丝分裂。我们已经提出了高尔基膜细胞周期特异性检查点的存在。我们已经发现，高尔基体碎裂需要MEK1和Polo-like Kinase(PLK)以及高尔基体相关蛋白GRASP55和GRASP65。我们的假设是，MEK1激活了一种名为ERK1c的新型ERK剪接变体，它使GRASP55磷酸化，从而断开高尔基体堆叠。这一事件发生在G2期，是进入有丝分裂所必需的。另一方面，我们建议将GRASP65磷酸化。磷酸化的GRASP65招募一种名为GIP(GRAP相互作用蛋白)的新蛋白，这一事件是GRASP65依赖于有丝分裂中纺锤体动力学调节所必需的。一项新的筛查揭示了一些调节高尔基体堆叠大小的蛋白质，我们的假设是这些蛋白质在有丝分裂过程中被修饰(通过磷酸化/去磷酸化)来重组高尔基体膜。最后，我们正在筛选5000种人类酶(激酶、磷酸酶、脂肪酶、GTP酶等)，以确定通过高尔基体的组织控制细胞进入有丝分裂的成分。我们的发现将揭示细胞在细胞周期中复制其重要细胞器的机制，以及高尔基体膜如何反过来通过它们的组织控制有丝分裂的进入

DESCRIPTION (provided by applicant): The pericentriolar inter connected stacks of Golgi cisternae are fragmented in mitotic mammalian cells. Why do these membranes undergo such a drastic change in their organization and by what mechanism? Do Golgi membranes fuse with the endoplasmic reticulum (ER) during mitosis and therefore use ER for their transmission into daughter cells? Our recent findings reveal that Golgi membranes do not fuse with the ER during mitosis. These findings resolve a long-standing controversy. We have found that inhibiting Golgi fragmentation prevents entry into mitosis. We have proposed the existence of a Golgi membrane specific cell-cycle checkpoint. We have found that kinases MEK1 and Polo like kinase (Plk); and Golgi associated proteins GRASP55 and GRASP65 are required for Golgi fragmentation. Our hypothesis is that MEK1 activates a novel spliced variant of ERK called ERK1c, which phosphorylates GRASP55 to disconnect Golgi stacks. This event occurs in G2 and it is necessary for entry into mitosis. Plk on the other hand, we suggest phosphorylates GRASP65. The phosphorylated GRASP65 recruits a novel protein called Gip (GRASP interacting protein) and this event is necessary for GRASP65 dependent regulation of spindle dynamics in mitosis. A new screen has revealed a number of proteins that regulate the dimensions of Golgi stacks and our hypothesis is that these proteins are modified (by phosphorylation/dephosphorylation) to reorganize Golgi membranes during mitosis. Finally, we are screening 5000 human enzymes (kinase, phosphatase, lipases, GTPases etc) to identify components that control, through the organization of Golgi apparatus, entry of cells into mitosis. Our findings will reveal the mechanism by which, cells duplicate their essential organelles during the cell cycle, and how Golgi membranes in turn through their organization, control mitotic entry