Specificity of the GET pathway for TA protein insertion in Arabidopsis thaliana

拟南芥中 TA 蛋白插入的 GET 途径的特异性

• 批准号: 373192667
• 负责人: Professor Dr. Christopher Grefen
• 金额: --
• 依托单位: Lehrstuhl für Molekulare und Zelluläre Botanik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2017
• 资助国家: 德国
• 起止时间: 2016-12-31 至 2017-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/373192667?language=en
• 关键词: Specificity; GET; pathway; TA; protein

The Guided Entry of Tail-anchored proteins (GET) pathway is viewed as textbook example of TA protein insertion into the ER membrane. The cytosolic ATPase ScGET3 shuttles nascent TA proteins to the ER receptors ScGET1/2 for membrane insertion. While biochemical and structural analyses have established this seemingly compelling model, physiological and genetic evidence for the mechanism is scarce. In yeast, loss of GET function is dispensable and only a limited number of TA proteins have so far been tested to depend on GET for membrane insertion, leaving the question unresolved which alternative pathway(s) is(are) likely responsible for posttranslational insertion of most TA proteins. ScGET3 also acts as a molecular chaperone in protein quality control, binding to misfolded TA proteins and either reverting these to an insertion competent state or targeting them for degradation.We have identified and characterised the main orthologues of a putative GET pathway in plants and uncovered that GET loss-of-function lines in Arabidopsis show shorter root hairs, while otherwise growing normally. While this defect can at least in part be attributed to reduced abundance of an important plasma membrane SNARE (SYP123), lack of a more pronounced phenotype and identification of TA proteins that do not bind to AtGET orthologues suggest existence of alternative insertion pathways. Moreover, aberrant expression of the cytosolic AtGET3a in the Atget1 line leads to a range of severe phenotypes from seedling lethality to reduced growth and fertility. We aim to understand the specificity of AtGET3a in targeting TA proteins to the ER and what, if any, alternative cellular functions does it execute. Also, we seek to determine the key players in the ER membrane for TA protein insertion and identify protein(s) that engage in an alternative insertion pathway.

尾锚定蛋白的引导进入（GET）途径被视为TA蛋白插入ER膜的教科书实例。胞质ATP酶ScGET 3将新生TA蛋白穿梭至ER受体ScGET 1/2以进行膜插入。虽然生物化学和结构分析已经建立了这个看似令人信服的模型，但生理和遗传证据很少。在酵母中，GET功能的丧失是不可避免的，并且迄今为止仅有限数量的TA蛋白被测试为依赖于GET进行膜插入，留下了未解决的问题，即哪个替代途径可能负责大多数TA蛋白的翻译后插入。ScGET 3也作为一个分子伴侣蛋白质的质量控制，结合错误折叠的TA蛋白，并恢复这些插入能力的状态或针对他们degradation.We已经确定和其特征的主要直系同源物的推定GET途径在植物和发现，在拟南芥中的GET功能丧失线显示较短的根毛，而在其他方面正常生长。虽然这种缺陷可以至少部分地归因于重要的质膜SNARE（SYP 123）的丰度降低，但是缺乏更明显的表型和鉴定不与AtGET直向同源物结合的TA蛋白表明存在替代插入途径。此外，Atget 1系中胞质AtGET 3a的异常表达导致从幼苗致死到生长和生育力降低的一系列严重表型。我们的目标是了解AtGET 3a在靶向TA蛋白到ER中的特异性，以及它执行的替代细胞功能（如果有的话）。此外，我们试图确定ER膜中TA蛋白插入的关键参与者，并鉴定参与替代插入途径的蛋白质。