Functional Adaptation of Microtubules by Acetylation

描述(申请人提供)：微管是真核生物中普遍存在的结构，由1-微管蛋白和2-微管蛋白二聚体组成。微管在细胞运动、细胞内运输和细胞极化中起着关键作用。不同的微管如何在细胞内的多种环境中发挥作用还不是很清楚。通常情况下，马达蛋白沿着微管的亚群移动特定的细胞货物，这种选择性运输对细胞极化至关重要。一个引人注目的例子是神经元，在那里特定的货物从细胞体移动到树突或轴突投射中。微管表面选择性传输的原理和机制还不是很清楚。我们探索了一个假设，即微管通过微管蛋白亚基的空间受限翻译后修饰(PTM)在功能上适用于选择性运输和其他局部功能。K40在1-微管蛋白上的乙酰化是一种高度保守的PTM，标志着微管的更新相对缓慢。在神经元中，1-微管蛋白的K40乙酰化在轴突的微管上比在树突中的微管上高度丰富。最近的研究表明，轴突微管的K40乙酰化刺激特定运动蛋白的结合和运动，包括轴突内的Kinesin-1。我们在这里报告了在模式原生动物四膜虫和斑马鱼中鉴定了K401-微管蛋白乙酰化所需的保守蛋白。该蛋白是MEC-17的同源蛋白，MEC-17是一种先前研究过的蛋白质，是线虫触觉感受器神经元功能所必需的。我们发现MEC-17在体外介导了K40在1-微管蛋白上的乙酰化。我们将检验这一假设，即MEC17是长期寻找的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，促进神经元的分化和功能。我们将使用模式生物，线虫线虫和斑马鱼Danio rerio，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：触摸感受器神经元(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丰富，这一建议与广泛的疾病有关，特别是与神经退行性疾病有关。

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.