Identifying and overcoming protein secretion bottlenecks in yeast and filamentous fungal cell factories

酵母菌和霉菌都是真菌。虽然像酿酒酵母这样的酵母菌被广泛认为是有用的，因为它在酿造啤酒和葡萄酒以及制作面包方面起到了作用，但大多数霉菌被认为是一种滋扰，因为它们会导致食物的明显腐烂，尽管有些物种可以用来制造有价值的化学品(如青霉素)。事实上，酵母和霉菌都是非常重要的，在商业上被用来制造不是由这种真菌自然产生的蛋白质。在这种情况下，制造蛋白质所必需的基因被引入真菌中。例如胰岛素(用于糖尿病患者)、凝乳酶(用于奶酪生产)和食品加工中使用的各种酶。此外，有关酶如何工作的基本信息需要充足的蛋白质供应，这通常意味着这些蛋白质是由真菌等‘细胞工厂’产生的。从细胞工厂制造蛋白质的一个常见困难是产量低于预期。这是因为细胞感觉到它被要求制造一种它通常不会制造的蛋白质，并将其分泌到细胞外部。细胞变得紧张，它在细胞内启动了一系列旨在保护自己的事件，在这样做的过程中，减少了分泌到细胞外的蛋白质的产量。有些蛋白质会产生比其他蛋白质更大的压力，但我们不知道支配这种压力的规则。这个项目的目的是找出规律，从而了解如何预测哪些蛋白质会造成最大的压力，然后与“细胞工厂”的有机体一起采取措施来抵消压力。通过这种方式，我们希望能够改进细胞工厂，以生产更多所需的蛋白质。特别是，我们的目标是提高真菌细胞工厂生产可能在临床上有用的抗体分子的能力。

Yeasts and moulds are both types of fungi. While yeasts such as Saccharomyces cerevisiae are widely regarded as useful because of its roles in making beer and wine, and in making bread, most moulds are regarded as a nuisance because they cause visible spoilage of foods, even though some species have uses in making valuable chemicals (e.g. penicillin). In fact, both yeasts and moulds are very important and are used commercially to make proteins that are not naturally produced by that fungus. In those cases, the gene that is necessary to make the protein is introduced into the fungus. Examples are insulin (for diabetics), chymosin (for cheese production) and a variety of enzymes used in food processing. Also, basic information about how enzymes work requires a plentiful supply of protein which usually means that those proteins are produced by a 'cell factory' such as a fungus. A common difficulty in making proteins from cell factories is that the yields are lower than desired. That is because the cell senses that it is being asked to make, and secrete to the outside of the cell, a protein which it wouldn't ordinarily make. The cell becomes stressed and it initiates a series of events within the cell aimed at protecting itself which, in so-doing, reduces the yield of protein secreted to the outside of the cell. Some proteins give rise to a bigger stress than others but we do not know the rules that govern the stress. This project aims to identify the rules and, thereby, understand how to predict which proteins will cause most stress and then to take steps with the 'cell factory' organisms to counteract the stress. In that way, we hope to be able to improve the cell factories to make more of the desired proteins. In particular, we aim to improve the capacity of fungal cell factories to produce antibody molecules that could be useful clinically.