Using Arabidopsis to uncover new roles for peroxins

描述(由申请人提供)：过氧化物体是人类和植物发育所必需的代谢室。尽管人们对基质蛋白是如何进入过氧酶体的了解越来越多，但翻转受损或过时的过氧酶体蛋白的机制仍然很不清楚。拟议的研究将解决拟南芥中过氧化物体相关蛋白的降解；该系统独特的过氧化物体功能和简便的遗传学将使解剖完整生物体中的过氧化物体过程成为可能。由PEX基因编码的过氧化物素是过氧化物体生物发生所必需的。大多数过氧化物素在基质蛋白输入中起作用；这项工作将确定这些过氧化物素的子集是否在基质蛋白周转中具有额外的作用。初步数据表明，过氧化物素的一个子集在受体循环和一种新型的逆转位--去除受损或不再需要的过氧体基质蛋白的降解--中共同发挥作用。提出了三个特定的目标来确定过氧化酶体相关蛋白降解的成分和分子需求。目的1研究过氧化物酶和蛋白酶体亚基缺陷突变株中基质蛋白的定位和稳定性。目标2将确定降解两种过氧化体基质蛋白所需的顺式作用分子信号，这两种蛋白在幼苗发育的特定阶段经历调节破坏。AIM 3将恢复在已知和未发现的过氧化物酶相关降解机制组件中存在缺陷的突变。这些目标的成功完成将开始解决过氧化物体生物学中一个尚未解开的谜团：过氧化物体如何处理受损或过时的蛋白质？过氧化体缺陷是一组被称为过氧化体生物发生障碍的遗传综合征的基础，这些综合征在婴儿期通常是致命的，其特征是严重的精神发育迟缓、神经元迁移缺陷、颅面畸形和其他症状。拟议的实验将利用植物过氧化物体的独特方面，同时利用真菌和哺乳动物系统的知识来提供可能适用于真核生物的见解。将一个进化上截然不同的模型加入到过氧化体生物学的研究中，将允许模型和假设的发展，以扩大和完善我们对这些重要细胞器的理解。公共卫生相关性：利用拟南芥发现过氧化物素的新作用，过氧化物体是容纳关键代谢反应的亚细胞隔间，对正常人类发育至关重要。过氧酶体缺陷是一组被称为过氧酶体生物发生障碍的遗传综合征的基础，通常在婴儿早期是致命的。拟议的实验将阐明当过氧化体受损或不再需要时，细胞如何处理过氧化体中的蛋白质。

DESCRIPTION (provided by applicant): Peroxisomes are metabolic compartments that are essential for human and plant development. Although understanding of how matrix proteins are imported into peroxisomes is increasing, mechanisms for turning over damaged or obsolete peroxisomal proteins remain largely obscure. The proposed studies will address peroxisome-associated protein degradation in Arabidopsis thaliana; the unique peroxisomal functions and facile genetics of this system will allow dissection of peroxisomal processes in an intact organism. Peroxins, encoded by PEX genes, are necessary for peroxisome biogenesis. Most peroxins act in matrix protein import; this work will determine whether a subset of these peroxins have additional roles in matrix protein turnover. Preliminary data suggest that a subset of peroxins work together both in receptor recycling and in a novel type of retrotranslocation - the removal for degradation of peroxisomal matrix proteins that are damaged or no longer needed. Three specific aims are proposed to identify components and molecular requirements of peroxisome-associated protein degradation. Aim 1 will characterize matrix protein localization and stability in mutants defective in peroxins and proteasome subunits. Aim 2 will identify cis-acting molecular signals necessary for degradation of two peroxisomal matrix proteins that undergo regulated destruction during a specific stage of seedling development. Aim 3 will recover mutants defective in known and undiscovered components of the peroxisome-associated degradation machinery. The successful completion of these aims will begin to address an unsolved mystery of peroxisome biology: How do peroxisomes dispose of damaged or obsolete proteins? Peroxisomal defects underlie a group of inherited syndromes known as peroxisome biogenesis disorders, which are generally fatal in infancy and are characterized by severe mental retardation, neuronal migration defects, craniofacial abnormalities, and other symptoms. The proposed experiments will exploit unique aspects of plant peroxisomes while taking advantage of knowledge from fungal and mammalian systems to provide insights that are likely to apply throughout eukaryotes. Adding an evolutionarily distinct model to the study of peroxisome biology will allow the development of model and hypotheses to expand and refine our understanding of these essential organelles. PUBLIC HEALTH RELEVANCE: Using Arabidopsis to Uncover New Roles for Peroxins Peroxisomes are subcellular compartments housing critical metabolic reactions and are essential for normal human development. Peroxisomal defects underlie a group of inherited syndromes known as peroxisome biogenesis disorders, which are generally fatal early in infancy. The proposed experiments will elucidate how cells dispose of proteins within peroxisomes when they are damaged or no longer needed.