Effects of alpha1-antitrypsin polymerisation on organelle structure and fluidity in hepatocytes

α1抗胰蛋白酶缺乏的个体患肺和肝脏疾病的风险增加。这种肺部疾病的发生是因为血液中的抗胰蛋白酶水平太低，无法预防肺部炎症造成的损害。这种肝脏疾病是由于一种异常形式的抗胰蛋白酶在肝细胞的内质网(简称ER)内积聚而成。由于尚不清楚的原因，内质网中抗胰酶聚合物的聚集增加了个体发展为肝硬变(疤痕形成)或肝癌的几率。目前还没有针对抗胰蛋白酶缺乏的肝病的治疗方法。我们希望了解抗胰酶聚合物是如何影响ER功能的，以便我们能够开发新的保护肝脏的治疗方法。许多疾病是由一种称为ER应激的ER功能障碍引起的。内质网的目的是制造分泌的蛋白质，如抗胰蛋白酶。新的蛋白质在内质网中被“折叠”成其独特的形状，使它们能够在体内发挥其特定的作用。当新合成的内质网蛋白不能正确折叠时，就会出现内质网应激，例如由于该蛋白的遗传突变。这种“错误折叠”导致新的蛋白质随机地粘在一起，破坏细胞并引发炎症。与这些随机聚集相反，我们和其他人已经证明的最常见的α1-抗胰蛋白酶突变形式形成了有序的“聚合物”链，不会直接导致内质网应激。相反，它们使细胞对其他压力更敏感，如有毒化学物质或高温，这些压力更容易引发内质网应激。抗胰蛋白酶聚合物导致这种敏感性增加的原因尚不清楚，尽管我们之前已经证明，抗胰酶聚合物会损害正常蛋白质在内质网内的运动。这可能会损害正常蛋白质的折叠。我们之前开发了新的技术，使我们能够确定α1-抗胰蛋白酶的聚合物如何改变内质网的生物学，例如改变其粘度。我们的目标是使用先进的显微镜技术来观察抗胰蛋白酶和其他蛋白质如何在内质网中移动，同时也观察使用我们开发的其他技术的蛋白质折叠的效率。通过结合这些新技术，我们将了解抗胰蛋白酶聚合物如何改变内质网内的环境，以及这如何改变细胞对内质网压力的敏感性。利用这一新知识，我们将操纵肝细胞中的内质网，旨在使其行为恢复正常。然后，我们将测试这是否能阻止异常信号，而异常信号是导致α1抗胰蛋白酶缺乏症患者发展为肝脏疤痕(肝硬变)和炎症的原因。该项目的结果为药物开发确定了新的靶点，它们可能使我们能够预防甲型抗胰蛋白酶缺乏症所见的肝病。

Individuals with alpha1-antitrypsin deficiency are at increased risk of lung and liver disease. The lung disease arises because blood levels of antitrypsin are too low to protect against damage caused by lung inflammation. The liver disease results from the accumulation of an abnormal form of antitrypsin inside a part of the liver cell called the endoplasmic reticulum (or ER for short). For reasons that remain unclear, the accumulation of polymers of antitrypsin within the ER increases the chances of an individual developing liver cirrhosis (scarring) or liver cancer. No current therapy targets the liver disease of antitrypsin deficiency. We wish to understand how antitrypsin polymers affect ER function, so that we can develop new liver-protective treatments.Many diseases are caused by a type of ER malfunction called "ER stress". The purpose of the ER is to manufacture secreted proteins, like antitrypsin. New proteins are "folded" within the ER into their unique shape that allows them to perform their specific role in the body. ER stress arises when newly made ER proteins fail to fold correctly, for example due to an inherited mutation of that protein. This "misfolding" causes the new proteins to stick together randomly, damaging the cell and triggering inflammation. In contrast to these random aggregates, the most common mutated forms of alpha1-antitrypsin form ordered chains of "polymers" that we and others have shown do not cause ER stress directly. Instead, they make the cell more sensitive to other stresses, such as toxic chemicals or high temperatures, which can trigger ER stress more easily. The reason why polymers of antitrypsin cause this increased sensitivity is not known, although we previously showed that antitrypsin polymers impair the movement of normal proteins inside the ER. This might impair the folding of normal proteins.We previously developed new technologies that allow us to determine how polymers of alpha1-antitrypsin alter the biology of the ER, for example changing its viscosity. We aim to use advanced microscopy techniques to watch how antitrypsin and other proteins move inside the ER, while also observing the efficiency of protein folding using other technologies we have developed. By combining these new techniques, we will understand how polymers of antitrypsin change the environment inside the ER and how this changes the cell's sensitivity to ER stress. Using this new knowledge, we will manipulate the ER in liver cell aiming to return its behaviour to normal. We will then test if this prevents the abnormal signalling that is responsible for patients with alpha1-antitrypsin deficiency developing liver scarring (cirrhosis) and inflammation. The results of this project identify new targets for drug development they may allow us to prevent the liver disease seen in alpha1-antitrypsin deficiency.