ER and post-ER quality control of integral membrane proteins

在真核生物中，大约三分之一的新合成的蛋白质进入内质 网状结构(ER)。一旦与这个隔室联系在一起，这些新生多肽就是后 翻译处理，获得它们的本机确认，寡聚，并被排序 胞外分泌或输送到其他细胞器。然而，许多致病因素 突变损害了蛋白质的折叠和成熟，进而可以产生聚集- 易受感染的物种。以抵消伴随蛋白质积累的灾难性影响 聚集体，错误折叠的蛋白质底物：(I)由相关的分子伴侣选择 利用内质网，(Ii)用泛素修饰，(Iii)通过称为 逆转易位，以及(Iv)被26S蛋白酶体降解。Brodsky和他的同事被命名为 这条内质网相关降解(ERAD)的途径，在过去的21年里，许多 布罗德斯基实验室对这一系列事件背后的分子机制进行了定义。至 到目前为止，大约有80种人类疾病与ERAD途径有关，已经发表了1200篇出版物 关于这条道路的各个方面的作者。正在进行的努力正在定义 几种ERAD相关疾病的病理生理学基础。同时，委员会的成员 Brodsky实验室揭示了关键组件如何在ERAD期间协调每一步。在 在过去的5年里，该实验室发表了的论文，并开发了 提供了一种前所未有的视角来了解导致选择、泛素化、 不同底物的反向移位和降解。然而，最近的发现 决定追求更具挑战性的研究方向：不可避免地，这些下一步的努力 将需要额外的方法开发和追求更长期的目标。特定的 该研究计划将解决的问题包括：哪些生化特征定义了 Erad底物？哪些因素足以驱动ERAD底物的逆转移位， 其中一些是易于聚合的？内质网相关的蛋白水解酶是否与 26S蛋白酶体，破坏稳定整合到内质网膜上的底物，以及 因此可能对易位有抵抗力？以及，逆转膜蛋白是如何- 从内质网中释放出来后，什么可以留在胞浆中--以可溶的状态保留？ 这些问题的答案，是该领域研究的核心，将显著地 加深对如何在蛋白质毒性应激下维持细胞健康的理解 以及与ERAD相关的疾病是如何产生和可能纠正的。

Approximately one-third of all newly synthesized proteins in eukaryotes enter the endoplasmic reticulum (ER). Once associated with this compartment, these nascent polypeptides are post- translationally processed, acquire their native confirmations, oligomerize, and are sorted for extracellular secretion or delivery to other organelles. However, many disease-causing mutations compromise protein folding and maturation, which in turn can generate aggregation- prone species. To off-set the catastrophic effects that accompany the accumulation of protein aggregates, misfolded protein substrates are: (i) selected by molecular chaperones associated with the ER, (ii) modified with ubiquitin, (iii) delivered to the cytoplasm via a process known as retrotranslocation, and (iv) degraded by the 26S proteasome. Brodsky and colleagues named this pathway ER associated degradation (ERAD), and over the past 21 years many of the molecular mechanisms underlying this sequence of events were defined in the Brodsky lab. To date, ~80 human diseases are linked to the ERAD pathway and >1,200 publications have been authored on various aspects of this pathway. Ongoing efforts are defining the pathophysiological foundation of several ERAD-related disorders. In parallel, members of the Brodsky lab have revealed how key components orchestrate each step during ERAD. In the past 5 years, the lab has published 64 papers, and tools and technologies were developed that provide an unprecedented view of the mechanisms that lead to the selection, ubiquitination, retrotranslocation, and degradation of diverse substrates. Nevertheless, recent discoveries dictate that more challenging research directions are pursued: By necessity, these next efforts will require additional method development and a pursuit of longer-term goals. Specific questions that the research program will address include: What biochemical features define an ERAD substrate? Which factors are sufficient to drive the retrotranslocation of ERAD substrates, some of which are aggregation-prone? Do ER-associated proteases function in tandem with the 26S proteasome to destroy substrates that are stably integrated into the ER membrane, and thus might be retrotranslocation resistant? And, how are retrotranslocated membrane proteins— which can reside in the cytosol after being liberated from the ER—retained in a soluble state? Answers to these questions, which lie at the core of research in the field, will significantly advance an understanding of how cellular health is maintained in the face of proteotoxic stress as well as how ERAD-associated diseases arise and might be rectified.