Tail-anchored protein biogenesis: defining the ATP dependent route

生物是由细胞组成的，细胞需要膜来提供细胞内的屏障，并保护它们免受外界的伤害。虽然形成这些屏障的生物膜在本质上是令人难以置信的复杂和多样的，但它们通常以布满许多蛋白质的脂质双层为特征。细胞通常必须通过制造新的膜来补充和更新它们的膜，而这个过程的关键部分是将新的蛋白质插入或缝合到脂质双层中。在更复杂的细胞中，例如组成我们身体的那些细胞，这种膜蛋白的整合是称为内质网的专门隔室的关键功能之一。与许多生物学过程一样，蛋白质整合到内质网的脂质双层中有不同的方式。其中一种机制现在已经相当清楚，可以被描述为内质网膜蛋白合成的“经典”途径。虽然这一经典途径的精确细节仍有待完全确定，但我们知道大多数介导它的细胞因子和机制。相比之下，另一个完全不同的途径却没有得到很好的研究，因此我们对负责它的细胞成分或它们的确切作用知之甚少。第二条途径用于制造一类重要的分子，称为尾锚定膜蛋白，这是更复杂细胞的特征，如我们自己的细胞。这个项目的目的是确定负责将尾锚定蛋白质放入内质网膜的细胞机器。我们将利用我们现在可以在试管中复制第二种途径的事实，使我们能够比较细胞组分的不同组合如何进行尾锚定蛋白插入。我们特别感兴趣的是观察被称为分子伴侣的细胞机器的贡献，因为我们有充分的理由相信它们在将尾锚定蛋白质放入内质网中起着重要作用。有许多不同的伴侣，我们的工作将告诉我们哪些特定的伴侣对第二条途径很重要，以及它们在这个过程中到底起什么作用。

Living things are made up of cells, and cells need membranes to provide barriers inside the cell and to protect them from the outside world. Whilst the biological membranes that form these barriers are incredibly complex and diverse in nature, they are generally characterised by a lipid bilayer that is studded with many proteins. Cells must normally replenish and renew their membranes by making new ones, and a key part of this process is the insertion or stitching of new proteins into the lipid bilayer. In more complex cells, such as those that make up our body, this integration of membrane proteins is one of the key functions of a specialised compartment known as the endoplasmic reticulum. As is the case for many biological processes, it has become clear that there are different ways of integrating a protein into the lipid bilayer of the endoplasmic reticulum. One mechanism is now fairly well understood and can be described as the 'classical' route for membrane proteins synthesis at the endoplasmic reticulum. Whilst the precise details of this classical pathway remain to be fully determined, we know most of the cellular factors and machineries that mediate it. In contrast, a second quite different pathway has been far less well studied so we know very little about the cellular components that are responsible for it or exactly what they do. This second pathway is used to make an important class of molecules called tail-anchored membrane proteins that are characteristic of more complex cells such as our own. The aim of this project is to identify the cellular machines that are responsible for putting tail-anchored proteins into the membrane of the endoplasmic reticulum. We will make use of the fact that we can now replicate this second pathway in a test tube, allowing us to compare how well different combinations of cellular components can carry out tail-anchored protein insertion. We are particularly interested in looking at the contribution of cellular machines known as molecular chaperones, since we have good reason to believe they play a major role in putting tail-anchored proteins into the endoplasmic reticulum. There are many different chaperones, and our work will tell us which particular chaperones are important for the second pathway and what exactly it is that they do during this process.