Assembly and dynamics of macromolecular protein complexes at the membrane-microtubule nexus during cell division

细胞分裂过程中膜-微管连接处大分子蛋白复合物的组装和动力学

• 批准号: 396136985
• 负责人: Professorin Dr. Katharina Bürstenbinder
• 金额: --
• 依托单位: Arbeitsgruppe Zellbiologie der Pflanzen
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/396136985?language=en
• 关键词: Assembly; dynamics; macromolecular; protein; complexes

Precise spatio-temporal regulation of cell division is fundamental for plant growth and morphogenesis. The plant cytoskeleton, comprised of actin filaments and microtubules, plays essential roles during cell division. During G2 to M transition, cortical interphase microtubules reorganize into a broad band, termed preprophase band (PPB) that encircles the cell at the future division site. The PPB disassembles at late prophase. Its positional information is maintained throughout cell division by a polarized membrane domain, referred to as cortical division zone (CDZ). The formation of a new cell wall is initiated at the cell center after separation of chromosomes by the spindle apparatus. It is facilitated by the phragmoplast, a bipolar array of microtubules that serves as scaffold for vesicle delivery and cell plate formation. The phragmoplast expands centrifugally and guides the growing cell plate to the CDZ, where it eventually fuses with the maternal wall to generate a new crosswall. Distinct sets of microtubule-associated proteins (MAPs) regulate PPB and spindle formation, CDZ set up, phragmoplast dynamics and the connection between microtubules and membrane compartments. Several genetic, cell biological, and physiological studies have provided insights into the role of individual MAPs and membrane-associated proteins in microtubule organization and membrane dynamics during cell plate formation. How different MAPs interact with each other, and how microtubule arrays are coordinated with membranes at the CDZ, cell plate and during vesicle delivery, however, remains elusive. Our work in the model plant Arabidopsis thaliana identified plant-specific IQ67 Domain (IQD) proteins as novel MAPs with proposed roles as cellular scaffolds for macromolecular complex assembly. We showed that members of the IQD family determine division plane positioning by controlling PPB formation and recruitment of CDZ-resident proteins. The respective IQD proteins localize to membranes and microtubules at the CDZ and cell plate, and at the PPB and phragmoplast, respectively, and interact with several CDZ-, phragmoplast- and cell plate-localized proteins via distinct motifs and domains adjacent to its eponymous IQ67 domain. The IQ67 domain harbors multiple functional Calmodulin (CaM) binding motifs pointing to a role of IQDs in calcium signaling. How or if IQDs contribute to CaM-mediated calcium signaling at the microtubule cytoskeleton, however, is still unknown.This proposal aims at elucidating the (CaM-regulated) dynamics and composition of IQD-assembled complexes at the phragmoplast and cell plate by combining cell biology, genetics and protein biochemistry. The combined approach will deepen our understanding of the regulation of microtubule organization and its connection with membranes. Thereby, our strategy offers a mechanistic framework to unravel principles governing signal integration at macromolecular protein assemblies during cell division and beyond.

细胞分裂的精确时空调控是植物生长和形态建成的基础。植物细胞骨架由肌动蛋白丝和微管组成，在细胞分裂过程中起着重要作用。在G2到M的过渡期，皮层间期微管重组成一个宽带，称为preprophase带（PPB），包围细胞在未来的分裂网站。PPB在前期晚期解体。它的位置信息通过极化的膜结构域（称为皮质分裂区（CDZ））在整个细胞分裂过程中保持。新细胞壁的形成始于纺锤体分离染色体后的细胞中心。成膜体是一种微管的双极阵列，作为囊泡递送和细胞板形成的支架。成膜体离心膨胀，并引导生长的细胞板到CDZ，在那里它最终与母体壁融合，产生一个新的横壁。不同的微管相关蛋白（MAPs）调节PPB和纺锤体的形成，CDZ的建立，成膜体动力学以及微管和膜室之间的连接。一些遗传学、细胞生物学和生理学研究已经提供了对单个MAP和膜相关蛋白在细胞板形成过程中微管组织和膜动力学中的作用的见解。然而，不同的MAP如何相互作用，以及微管阵列如何与CDZ、细胞板和囊泡递送期间的膜协调，仍然难以捉摸。我们在模式植物拟南芥中的工作确定了植物特异性IQ 67结构域（IQD）蛋白作为新的MAP，并提出了作为大分子复合物组装的细胞支架的作用。我们发现，IQD家族的成员通过控制PPB的形成和CDZ驻留蛋白的募集来确定分裂平面的定位。相应的IQD蛋白定位于膜和微管在CDZ和细胞板，并在PPB和成膜体，分别，并相互作用与几个CDZ-，成膜体和细胞板定位的蛋白质通过不同的基序和结构域相邻的epidermal IQ 67结构域。IQ 67结构域含有多个功能性钙调蛋白（CaM）结合基序，表明IQDs在钙信号传导中的作用。IQDs如何或是否有助于钙调素介导的钙信号在微管cytoskeleton，然而，仍然是未知的，这一建议的目的是阐明（钙调素调节）的动力学和组成的IQDs组装复合物在成膜体和细胞板结合细胞生物学，遗传学和蛋白质生物化学。结合的方法将加深我们对微管组织的调节及其与膜的联系的理解。因此，我们的策略提供了一个机制框架，以解开在细胞分裂及以后的大分子蛋白质组装体的信号整合的原则。