Cellular Control of Endoplasmic Reticulum Biogenesis

内质网生物发生的细胞控制

• 批准号: 0400149
• 负责人: Robin Wright
• 金额: $ 11.29万
• 依托单位: University of Minnesota-Twin Cities
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-09-15 至 2005-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0400149&HistoricalAwards=false
• 关键词: Cellular; Control; Endoplasmic; Reticulum; Biogenesis

Eukaryotic cells are composed of a basic set of organelle "building blocks" that include (among others) the nucleus, endoplasmic reticulum (ER), Golgi apparatus, lysosomes, mitochondria, peroxisomes and, in photosynthetic organisms, chloroplasts. This relatively small number of separate cellular components belies the amazing diversity of cell structure and function that exists in eukaryotic organisms. In each case, the specialization of cell structure and function is mirrored by changes in organelle composition. Thus, a key feature of cell biology is the regulation of subcellular organization, that is, the regulation of which organelles are present and their size, composition, location, number, and life spans. Surprisingly, given the importance of this regulation, there is not yet a single example in which the molecular nature of this regulation is well understood.The experiments that will be performed explore this question by focusing on the regulation of endoplasmic reticulum structure and function in the yeast, Saccharomyces cerevisiae. As in all other cell-types examined, the organization of the ER in yeast is sensitive to the levels of a subset of ER proteins. One of these proteins, HMG-CoA reductase, catalyzes the first committed step in sterol and isoprene biosynthesis. In yeast, expression of increased levels of HMG-CoA reductase induces assembly of specialized regions of ER termed karmellae, consisting of stacks of paired smooth membranes that are closely associated with the nucleus. The ability to control karmella assembly by merely changing the levels of a single protein provides a unique opportunity to explore the molecular mechanisms by which cells increase biogenesis of a particular ER domain when dictated by physiological demands. To uncover these mechanisms, Dr. Wright will use a genetic approach that takes advantage of new resources available as a result of completion of the Yeast Genome Project. Specifically, she will use a population genetic approach to identify deletion mutants that display defects in growth rate when they assemble karmellae. Coupled with information from a Two-Hybrid approach to identify gene products that interact with HMG-CoA reductase, this approach should reveal genes that have important roles in assembly of karmellae. The analysis of karmella assembly mutants will be guided by in vivo time-lapse light microscopy and electron microscopic analysis of karmella assembly. Completion of these experiments should uncover basic features of the communication network that reports and regulates ER function coordinately with changing physiological demands. Such knowledge will have specific application to understanding the cellular regulation of ER structure and function, but should also provide general insights concerning the cellular regulation of organelle biogenesis.

真核细胞由一套基本的细胞器“积木”组成，其中包括(除其他外)核、内质网、高尔基体、溶酶体、线粒体、过氧化物体以及光合作用生物体中的叶绿体。这种相对较少的独立细胞成分掩盖了真核生物中存在的惊人的细胞结构和功能的多样性。在每一种情况下，细胞器组成的变化都反映了细胞结构和功能的特化。因此，细胞生物学的一个关键特征是对亚细胞组织的调节，即调节存在哪些细胞器及其大小、组成、位置、数量和寿命。令人惊讶的是，考虑到这一调控的重要性，目前还没有一个例子能很好地理解这一调控的分子性质。将进行的实验将通过重点调控酿酒酵母中内质网的结构和功能来探索这个问题。正如在所有其他类型的细胞检测中一样，酵母中ER的组织对ER蛋白的一个子集的水平很敏感。其中一种蛋白质，HMG-CoA还原酶，催化甾醇和异戊二烯生物合成的第一步。在酵母中，HMG-CoA还原酶水平的增加导致内质网特殊区域的组装，称为甘露，由与细胞核密切相关的成对平滑膜堆叠组成。仅通过改变单个蛋白质的水平来控制karmella组装的能力为探索细胞在生理需求下增加特定ER结构域的生物发生的分子机制提供了独特的机会。为了揭示这些机制，赖特博士将使用一种遗传方法，利用酵母基因组计划完成后可用的新资源。具体地说，她将使用群体遗传学方法来识别在组装甘蓝时显示生长速度缺陷的缺失突变体。结合来自双杂交方法的信息，以确定与HMG-CoA还原酶相互作用的基因产物，该方法应该揭示在甘蓝组装中具有重要作用的基因。通过体内延时光学显微镜和电子显微镜对甘露聚合体的分析将指导对甘露聚合体的分析。这些实验的完成将揭示通信网络的基本特征，该网络报告和调节ER功能与不断变化的生理需求相协调。这些知识将对理解内质网结构和功能的细胞调控有特定的应用，但也应该提供关于细胞器生物发生的细胞调控的一般见解。