A novel, non-canonical mechanism for the nuclear entry of large mitochondrial enzymes

大型线粒体酶进入核的一种新颖的、非常规的机制

• 批准号: RGPIN-2020-05377
• 负责人: Michelakis, Evangelos
• 金额: $ 3.64万
• 依托单位: University of Alberta
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=716876
• 关键词: novel; non; canonical; mechanism; nuclear

To achieve efficiency, the interior of a cell is well-compartmentalized. Mitochondria are organelles in the cell where a number of specialized proteins work toward the production of energy to fuel all cellular functions. The nucleus is another organelle within the cell where the genes are located. Because of the critical importance of the genes, the interior of the nucleus is well protected with specialized membranes that surround the nucleus. Entry and exit from the nucleus occur only through specialized channels called nuclear pores (NP), that only allow proteins below a size limit to entry. In addition, a protein originating from another part of the cell, has to have a specific segment in one of its two ends, called “nuclear localization sequence” (NLS), to which specific traffic chaperones can bind it and guide it through the NP into the nucleus. We recently found that a very important enzyme only thought to exist within the mitochondria, was unexpectedly found in the nucleus as well. This enzyme (called pyruvate dehydrogenase complex, PDC) was functional in the nucleus, producing a critical metabolite for gene regulation. But PDC is the largest enzyme known in biology (its size far exceeds the size limit of NPs) and has no NLS. Thus it remains a mystery how PDC can enter the nucleus and its presence there suggests that an unknown, novel mechanism may exist for the entrance of large proteins in the nucleus. This research program aims to discover this novel entry mechanism. We will pursue early evidence from our preliminary experiments, that mitochondria travel and make contact points with the nucleus. A protein called Mitofusin2 (MFN2) that is found in both the mitochondria and the nucleus membranes, is used to tether the 2 organelles together. This allows the PDC to enter the external nuclear membrane and interact with one of the main proteins of the internal nuclear membrane, i.e. lamin, enabling its nuclear entry. We believe that this is a feature of all cells in the body and thus we will study many different cell types using advance molecular and imaging techniques, including super-resolution confocal microscopy. Our work is expected to significantly enhance the relative recent and incompletely understood concept of communication of mitochondria with the nucleus and, in general, the communication pathways between different cellular organelles. Its potential implications are many and range from the function of cells during embryo development, to the function of cells during metabolic stress, to the mechanism of aging. This research program provides excellent opportunities of the training of graduate students and is expected to result in important publications that cross many different aspects of biology.

为了实现效率，细胞的内部被很好地划分。线粒体是细胞中的细胞器，其中许多专门的蛋白质致力于产生能量，为所有细胞功能提供燃料。细胞核是细胞内基因所在的另一个细胞器。由于基因的重要性，细胞核的内部被围绕细胞核的特殊膜很好地保护着。进入和离开细胞核仅通过称为核孔（NP）的专门通道发生，该通道仅允许低于大小限制的蛋白质进入。此外，来自细胞另一部分的蛋白质必须在其两端之一具有特定片段，称为“核定位序列”（NLS），特定的交通分子伴侣可以将其结合并引导其通过NP进入细胞核。 我们最近发现，一种被认为只存在于线粒体中的非常重要的酶，也意外地在细胞核中发现。这种酶（称为丙酮酸脱氢酶复合物，PDC）在细胞核中起作用，产生基因调控的关键代谢物。但是PDC是生物学中已知的最大的酶（它的大小远远超过了NP的大小限制），并且没有NLS。因此，PDC如何进入细胞核仍然是一个谜，它的存在表明，一个未知的，新的机制可能存在的大型蛋白质进入细胞核。 本研究计划旨在发现这种新的进入机制。我们将从我们的初步实验中寻找早期证据，即线粒体旅行并与细胞核接触。 一种被称为线粒体融合蛋白2（MFN 2）的蛋白质在线粒体和核膜中都有发现，用于将两个细胞器拴在一起。这允许PDC进入外核膜并与内核膜的主要蛋白质之一（即核纤层蛋白）相互作用，使其能够进入核。 我们相信这是体内所有细胞的一个特征，因此我们将使用先进的分子和成像技术，包括超分辨率共聚焦显微镜，研究许多不同的细胞类型。我们的工作预计将显着提高相对最近和不完全理解的线粒体与细胞核的通信概念，并在一般情况下，不同的细胞器之间的通信途径。它的潜在意义是很多的，从胚胎发育过程中细胞的功能，到代谢应激过程中细胞的功能，再到衰老的机制。该研究计划提供了培养研究生的绝佳机会，预计将导致跨越生物学许多不同方面的重要出版物。