Functional Adaptation of Microtubules by Acetylation

描述（由申请人提供）：微管是普遍存在的真核结构，由 1- 和 2- 微管蛋白二聚体构成。微管在细胞运动、细胞内运输和细胞极化中发挥关键作用。目前尚不清楚不同的微管如何在细胞内的多种环境中发挥作用。通常，运动蛋白沿着微管子集移动特定的细胞货物，这种选择性运输对于细胞极化至关重要。一个引人注目的例子是神经元，其中特定的货物从细胞体转移到树突或轴突投影中。控制微管表面选择性运输的原理和机制尚不清楚。我们探索了一个假设，即微管通过微管蛋白亚基的空间限制性翻译后修饰（PTM）在功能上适应选择性运输和其他局部功能。 1-微管蛋白上 K40 的乙酰化是一种高度保守的 PTM，它标记周转相对较慢的微管。在神经元中，与树突中的微管相比，1-微管蛋白的 K40 乙酰化在轴突的微管上高度富集。最近的研究表明，轴突微管的 K40 乙酰化可刺激特定运动蛋白（包括轴突内的驱动蛋白-1）的结合和运动。我们在此报告了在模型原生生物四膜虫和斑马鱼中鉴定出 K40 1-微管蛋白乙酰化所需的保守蛋白。该蛋白是 MEC-17 的直系同源物，MEC-17 是一种先前研究过的蛋白，是秀丽隐杆线虫接触受体神经元功能所必需的。我们证明 MEC-17 在体外介导 1-微管蛋白上 K40 的乙酰化。我们将检验以下假设：MEC17 是人们长期寻找的 1-微管蛋白 K40 乙酰转移酶，并且 MEC-17 通过乙酰化 1-微管蛋白上的 K40，有助于神经元分化和功能。我们将使用模型生物，即秀丽隐杆线虫和斑马鱼斑马鱼，来评估 MEC-17 和 K40 乙酰化对 1-微管蛋白的功能，特别是在两种类型的神经元中：接触受体神经元（秀丽隐杆线虫）和初级运动神经元（斑马鱼）。由于 1-微管蛋白的乙酰化在神经系统中高度富集，因此该提议与多种疾病，特别是神经退行性疾病相关。 公共健康相关性：真核细胞充满了称为微管的纤维，充当细胞内运输的轨道并调节细胞的形状。该项目将测试一个假设，即微管表面的生化标记模式使特定的微管纤维适应特定的功能，包括选择性运输某些细胞成分。该项目将影响对与微管缺陷相关的人类疾病的病理学的理解，包括一些神经退行性疾病。

DESCRIPTION (provided by applicant): Microtubules are ubiquitous eukaryotic structures, built of dimers of 1- and 2-tubulin. Microtubules play key roles in cell motility, intracellular trafficking and cell polarization. It is not well understood how diverse microtubules function in multiple contexts inside the cell. Commonly, motor proteins move specific cellular cargoes along subsets of microtubules, and this selective transport is critical for cell polarization. One striking example is the neuron, where specific cargoes are moved from the cell body either into the dendrite or axon projections. The principles and mechanisms that govern the selective transport on the surface of microtubules are not well understood. We explore a hypothesis that microtubules are functionally adapted for selective transport and other localized functions, by spatially restricted post-translational modifications (PTMs) of tubulin subunits. Acetylation of K40 on 1- tubulin is a highly conserved PTM, that marks microtubules which turnover relatively slowly. In neurons, K40 acetylation of 1-tubulin is highly enriched on microtubules of the axon as compared to microtubules in dendrites. Recent studies indicate that K40 acetylation of axonal microtubules stimulates binding and motility of specific motor proteins, including kinesin-1 inside the axon. We report here an identification of a conserved protein that is required for K40 1-tubulin acetylation in the model protist Tetrahymena and zebrafish. This protein is an ortholog of MEC-17, a previously studied protein which is required for the function of touch receptor neurons in C. elegans. We show that MEC-17 mediates acetylation of K40 on 1- tubulin in vitro. We will test the hypothesis that MEC17 is the long-sought 1-tubulin K40 acetyltransferase, and that MEC-17, by acetylating K40 on 1-tubulin, contributes to neuronal differentiation and function. We will use model organisms, the worm Caenorhabditis elegans and zebrafish Danio rerio, to evaluate the function of MEC-17 and K40 acetylation on 1- tubulin, specifically in two types of neurons: in touch receptor neurons (C. elegans) and in primary motor neurons (zebrafish). As acetylation of 1-tubulin is highly enriched in the nervous system, this proposal is relevant to a broad range of diseases and in particular to the neurodegenerative disorders. PUBLIC HEALTH RELEVANCE: Eukaryotic cells are filled with fibers known as microtubules, that serve as tracks for intracellular transport and regulate the shape of cells. This project will test a hypothesis that patterns of biochemical marks on the surface of microtubules adapt specific microtubule fibers for specific functions, including a selective transport of certain cellular components. This project will have an impact on understanding of pathology of human diseases that are associated with defects in microtubules, including some neurodegenerative disorders.