Ubiquitin-dependent sorting in endosomes and the TGN

项目摘要和摘要 绝大多数生物功能使用膜包埋蛋白。控制产品质量和质量 这些膜蛋白的数量对这些过程的正常工作至关重要，而这种能力的缺陷 破坏错误折叠的蛋白质或去除不再需要的膜蛋白会导致过量 人类疾病。一种用于确定哪些蛋白质发生降解的中心机制是附着 对他们来说是泛素。泛素是一种很小的蛋白质，在整个王国中都保存得非常好 真核生物。当泛素与膜蛋白化学连接时，它会导致该蛋白质 被能够识别泛素的细胞机器降解。泛素也可以链接到另一个 泛素，形成多泛素链。不同的多泛素链是通过改变一种泛素的方式而形成的 与另一个相连，不同的降解机器使用不同的泛素链。一台机器 将膜蛋白分选到溶酶体的内部，方法是首先将它们分选到腔内小泡中， 聚集在多囊泡内小体/小体(MVB)内。MVB排序主要使用泛素链， 是通过泛素的赖氨酸-63连接在一起的，泛素与许多聚集和排序的内体蛋白结合 泛素化的膜蛋白进入腔内小泡。这些腔内小泡可以是 传递到内部的溶酶体并被降解，或者它们可以作为细胞外分泌 囊泡/外切体，携带内容物并将其传递到其他细胞以引起一系列生物效应。 许多关键问题仍然悬而未决，即蛋白质是如何分类进入腔内膜的 囊泡以及它们如何被分类为溶酶体和被分类为外体的不同之处。Aim1 将通过研究两个同源分选蛋白的分子机制来解决这些问题 用于不同地将蛋白质分类成腔内小泡，这些小泡进入溶酶体或成为外切体。 关于泛素是否附着在膜蛋白上的其他问题仍然存在。 高尔基体网络、内小体和细胞表面在细胞中的初步合成 内质网(所谓的“内质网后”蛋白)通过MVB途径将它们排他地发送出去。 退化模式。我们发现，用不同类型的多泛素链修饰的ER后蛋白是 沿着另一条不同的途径降解。AIM2将研究这一途径的分子特征，并 评估这一途径如何有助于控制膜蛋白的质量和数量。

PROJECT SUMMARY and ABSTRACT The vast majority of biological functions use membrane-embedded proteins. Controlling the quality and quantity of these membrane proteins is critical for these processes to work normally, and defects in the ability to destroy misfolded proteins or getting rid of membrane proteins that are no longer needed cause a plethora of human diseases. A central mechanism used to specify which proteins undergo degradation is attaching ubiquitin to them. Ubiquitin is a small protein that is extremely well-conserved across the entire kingdom of eukaryotic organisms. When ubiquitin is chemically linked to a membrane protein, it causes that protein to be degradaded by cellular machinery that can recognize ubiquitin. Ubiquitin can also be linked to another ubiquitin, forming polyubiquitin chains. Different polyubiquitin chains are made by changing how one ubiquitin is linked to another, and different ubiquitin chains are used by different degradation machines. One machine sorts membrane proteins to the interior of lysosomes by first sorting them into intralumenal vesicles that accumulate within multivesicular endosomes/bodies (MVB). MVB sorting primarily uses ubiquitin chains that are linked via lysine-63 of ubiquitin, which binds to a number of endosomal proteins that cluster and sort ubiquitinated membrane proteins into intralumenal vesicles. These intralumenal vesicles can either be delivered to the interior Lysosomes and be degraded, or they can be secreted as extracellular vesicles/exosomes, that carry and delivery contents to other cells to elicit a range biological effects. Many critical questions remain outstanding about how proteins are sorted into endosomal intralumenal vesicles and what differentiates how they are sorted to Lysosomes versus being sorted into exosomes. Aim1 will address these questions by examining the molecular mechanisms that two homologous sorting proteins use to differentially sort proteins into intralumenal vesicles that go to Lysosomes or become exosomes. Additional questions remain about whether ubiquitin attachment to membrane proteins in the trans- Golgi Network, Endosomes, and cell surface that have made it through their initial synthesis in the endoplasmic reticulum (so-called ‘post-ER’ proteins) exclusively sends them through the MVB pathway as their mode of degradation. We found that post-ER proteins modified with a different type of polyubiquitin chain are sent along a different pathway for degradation. Aim2 will study the molecular features of this pathway and assess how this pathway may contribute to controlling the quality and quantity of membrane proteins.