Inner nuclear membrane associated protein degradation

项目摘要 真核生物的细胞核被一层双膜结构所包围，即核被膜， 将核质与细胞质分开。外核膜是连续的， 内质网（ER），而内核膜（INM）是一个专门的细胞区室 一个独特的蛋白质组。为了确保房室内稳态，INM相关降解 蛋白质质量控制和INM蛋白的调节性蛋白水解都需要INMAD途径。我们 最近发现了一个新的INMAD分支，通过E3泛素连接酶发挥作用：后期 促进复合物/环体（APC/C），其降解芽殖酵母中的整合INM蛋白Mps 3。 此外，APC/C依赖性INMAD调节核膜重组，这是控制细胞凋亡的关键因素。 复制寿命和细胞老化。我们的假设是APC/C直接泛素化INM底物， 靶向它们进行蛋白酶体降解，这一过程对维持核膜至关重要 体内平衡为了验证这一假设，将实现三个具体目标：（1）确定APC/C模式- （2）确定APC/C依赖性INMAD底物的模式 提取和易位，和（3）确定受损的APC/C介导的病理后果， INMAD。在第一个目标下，负责APC/C介导的INM蛋白的关键顺式和反式因子 将表征泛素化和降解。在第二个目标下， AAA-ATP酶Cdc 48/p97及其辅因子提取并转运APC/C依赖的INMAD底物将被激活。 表征了在第三个目标下，核膜重塑和复制的生物学功能 将确定由APC/C介导的INMAD调节的寿命。预计拟议的研究将 为控制APC/C依赖性INMAD底物遍在化的机制提供关键见解， 易位和降解，以及INMAD损伤的病理后果。聚集 Mps 3同源物SUN 1参与了细胞的过早老化和营养不良性核纤层蛋白病， 哺乳动物揭示APC/C介导的INMAD如何调节其在酵母中的底物周转是研究INMAD的关键一步。 了解人类细胞中INM蛋白周转的分子机制，并可能提供一个 核分裂相关疾病和细胞周期调控之间的直接联系。

Project Summary The eukaryotic nucleus is enclosed by a double-membrane structure, the nuclear envelope, which separates the nucleoplasm from the cytoplasm. The outer nuclear membrane is continuous with the endoplasmic reticulum (ER), whereas the inner nuclear membrane (INM) is a specialized cellular compartment with a unique proteome. In order to ensure compartmental homeostasis, the INM-associated degradation (INMAD) pathway is required for both protein quality control and regulated proteolysis of INM proteins. We have recently discovered a novel INMAD branch functioning through the E3 ubiquitin ligase: the anaphase promoting complex/cyclosome (APC/C), which degrades the integral INM protein Mps3 in budding yeast. Furthermore, APC/C-dependent INMAD regulates nuclear envelope reorganization, a key factor controlling replicative lifespan and cell aging. Our hypothesis is that APC/C directly ubiquitinates INM substrates, targeting them for proteasomal degradation, which process is critical for maintaining nuclear envelope homeostasis. Three specific aims will be fulfilled to test this hypothesis: (1) determine the modes of APC/C- dependent INMAD substrate recognition, (2) determine the modes of APC/C-dependent INMAD substrate extraction and translocation, and (3) determine the pathological consequences of impaired APC/C-mediated INMAD. Under the first aim, the critical cis and trans factors responsible for APC/C-mediated INM protein ubiquitination and degradation will be characterized. Under the second aim, the mechanism by which the AAA-ATPase Cdc48/p97 and its cofactors extract and translocate APC/C-dependent INMAD substrates will be characterized. Under the third aim, the biological function of nuclear envelope remodeling and replicative lifespan regulated by APC/C-mediated INMAD will be determined. The proposed research is expected to provide key insights into the mechanism controlling APC/C-dependent INMAD substrate ubiquitination, translocation and degradation, and the pathological consequences of INMAD impairment. Aggregation of SUN1, the Mps3 homolog, has been implicated in premature cell aging and dystrophic laminopathies in mammals. Unraveling how APC/C-mediated INMAD regulates its substrate turnover in yeast is a crucial step to understanding the molecular mechanisms governing INM protein turnover in human cells and may provide a direct link between nuclear envelope-associated diseases and cell-cycle regulation.