Role of Septins in Organelle Transfer

描述（由申请人提供）：大分子和细胞器的精确区室化/定位在真核细胞中是必不可少的。这一提议涉及一种非膜屏障，它将酵母合子的细胞质细分为不同的亲本来源区域。先前已经在动物细胞的细胞质中描述了纤维“排除区”的实例，其中一些包括中间丝或肌动蛋白。没有一个能像我们在沙门氏菌中检测到的合子中间区复合体（ZMC）那样易于分析。酿酒。ZMC包括septins，并使人联想到在有丝分裂细胞周期期间位于母细胞和子细胞之间的芽颈处的含septins的结构。线粒体重新分布的检查点：初步数据导致ZMC延迟亲本线粒体融合的假设，因此确保线粒体基因组的单亲遗传，如已经观察到的。为了评估这一假设，我们将1）了解ZMC中的隔蛋白是否具有所需的动态特性，以及2）确定线粒体基因组的单亲遗传是否在隔蛋白突变体中受损。多聚体再分布的检查点：为了确定ZMC是否是多聚体再分布延迟的原因，我们将询问它们再分布的时间是否反映了1）它们的大小，2）septins的功能，或3）核（和纺锤体极体）之间的接触，正如我们的初步数据所建议的那样。功能的通用性：为了进一步了解ZMC的重要性范围，我们将了解它是否支配新颗粒在细胞质中的再分配，限制细胞皮层和核膜膜的膜蛋白通量，并负责观察亲本液泡在早期合子中不相互交换组分。 鉴于与芽颈的明显相似性以及初步观察结果，我们将确定ZMC是否划定了胞吐作用发生的皮质区。我们还将了解ZMC的septins是否经历特征性的共价修饰，以及这些修饰是否对ZMC的组织和功能至关重要。 该提案的最后一部分涉及确定一种药物的靶点，即氯吡脲，该药物可逆地改变了Septin组合的结构，并中断了合子中线粒体的再分配。由于这种药物也干扰动物细胞septins，其目标的鉴定将打开与septin生物学相关的研究的意想不到的途径。 公共卫生相关性：我们将研究的分区提供了一个屏障的原型，该屏障将真核细胞的细胞质区域亚区室化。我们的研究将有助于理解这些非常普遍的原则，有助于阐明septins的功能，这些功能与几种疾病有关，澄清发育细胞生物学和线粒体基因组遗传的核心问题，并启动对控制细胞器分布的新检查点的调查。

DESCRIPTION (provided by applicant): Accurate compartmentation/positioning of macromolecules and organelles is essential in eukaryotic cells. This proposal is concerned with a non-membranous barrier that subdivides the cytoplasm of yeast zygotes into regions of distinct parental origin. Examples of fibrous "zones- of-exclusion" have previously been described in the cytoplasm of animal cells, some of which include intermediate filaments or actin. None is nearly as amenable to analysis as the zygote midzone complex (ZMC) that we have detected and will investigate in S. cerevisiae. The ZMC includes septins and is reminiscent of septin-containing structures at the bud neck that lie between the mother and daughter during the mitotic cell cycle. A Checkpoint for Redistribution of Mitochondria: Preliminary data lead to the hypothesis that the ZMC delays fusion of parental mitochondria and therefore ensures uniparental inheritance of the mitochondrial genome, as has been observed. To evaluate this hypothesis, we will 1) Learn whether septins in the ZMC have the dynamic properties that are required, and 2) Determine whether uniparental inheritance of the mitochondrial genome is compromised in septin mutants. A Checkpoint for Redistribution of Polysomes: To determine whether the ZMC is responsible for the delay in redistribution of polysomes, we will inquire whether the timing of their redistribution reflects 1) Their size, 2) Functionality of septins, or 3) Contact between nuclei (and spindle pole bodies), as is suggested by our Preliminary Data. Generality of Function: To further understand the scope of importance of the ZMC we will learn whether it governs the redistribution of novel particles in the cytoplasm, limits flux of membrane proteins of the cell cortex and nuclear envelope, and is responsible for the observation that parental vacuoles do not exchange components with each other in early zygotes. Given the apparent similarity to the bud neck as well as preliminary observations, we will determine whether the ZMC delimits a cortical zone within which exocytosis occurs. We will also learn whether septins of the ZMC undergo characteristic covalent modifications and whether these modifications are essential for the organization and functions of the ZMC. The final part of the proposal concerns identification of the target of a drug, forchlorfenuron that reversibly alters the structures of septin assemblages and interrupts redistribution of mitochondria in zygotes. Since this drug also perturbs animal cell septins, identification of its target will open unanticipated avenues of investigation related to septin biology. PUBLIC HEALTH RELEVANCE: The partition which we will investigate provides a prototype of barriers that subcompartmentalize regions of the cytoplasm of eukaryotic cells. Our studies will help understand these very general principles, help elucidate functions of septins which are implicated in several diseases, clarify issues which are central to developmental cell biology and inheritance of the mitochondrial genome, and initiate the investigation of novel checkpoints that govern the distributions of organelles.