Protein import into the intermembrane space of mitochondria

线粒体膜间空间（IMS）的蛋白质对许多线粒体和细胞过程至关重要，如能量代谢、细胞凋亡以及代谢产物和蛋白质的转运。因此，IMS蛋白在IMS中被导入并正确折叠对于线粒体和细胞的稳态是必不可少的。事实上，它们的生物发生缺陷在许多疾病中发挥作用。许多IMS蛋白由线粒体二硫键中继系统（DRS）输入，该系统由两种必需蛋白组成：氧化还原受体Mia 40和巯基电子转移酶Erv 1。Mia 40/Erv 1-DRS在底物蛋白中引入二硫键，触发其折叠并导入IMS。然而，关于Mia 40/Erv 1-DRS，其调节和IMS蛋白的输入的许多基本的和疾病相关的问题仍然存在。第一个目标是解决Mia 40/Erv 1-DRS底物蛋白输入的调节。作为目标的第一部分，我们将阐明参与Mia 40/Erv 1-DRS途径蛋白质转运及其调节的胞浆过程。我们将鉴定和表征与胞质中新合成的底物蛋白相互作用的胞质蛋白。作为第二部分，我们将测试IMS中的线粒体氧化还原蛋白的功能，如硫氧还蛋白系统和过氧化物酶Hyr 1，并分析它们在Mia 40/Erv 1输入途径中的作用。第二个目标是表征Mia 40/Erv 1-二硫键中继系统的生理功能与在人类ERV 1突变患者中观察到的疾病表型之间的联系。通过研究这些突变在酵母模型系统和患者成纤维细胞中的后果，我们将阐明疾病表型的分子基础。我们已经表明，Mia 40/Erv 1-DRS具有比以前认为的更广泛的底物特异性。第三个目标是鉴定和表征酵母DRS的新底物，并表征缺乏已知输入途径底物序列特征的IMS蛋白的输入，通过鉴定与DRS底物相互作用的胞浆蛋白，并通过阐明DRS输入途径中氧化还原蛋白的功能，我们将为该途径及其调控提供有价值的见解。这些研究，以确定新的DRS底物，以表征IMS蛋白的进口与尚未未知的途径，并阐明huERV 1突变体的病理机制，将有助于获得IMS蛋白的生物起源及其在线粒体生理和疾病中的作用的全面了解。

Proteins of the intermembrane space (IMS) of mitochondria are crucial for many mitochondrial and cellular processes, such as energy metabolism, apoptosis and the transport of metabolites and proteins. Thus, it is essential for mitochondrial and cellular homeostasis that IMS proteins are imported and correctly folded in the IMS. Indeed, defects in their biogenesis play a role in many diseases. Many IMS proteins are imported by the mitochondrial disulfide relay system (DRS) consisting of two essential proteins: the redox receptor Mia40 and the sulfhydryl-electron transferase Erv1. The Mia40/Erv1-DRS introduces disulfide bonds in substrate proteins, triggering their folding and import into the IMS. However, many fundamental and disease-relevant questions regarding the Mia40/Erv1-DRS, its regulation and the import of IMS proteins remain.We will focus on three main objectives concerning the import of IMS proteins. The first objective will address the regulation of the import of substrate proteins of the Mia40/Erv1-DRS. As first part of the objective, we will elucidate cytosolic processes involved in the protein transport of the Mia40/Erv1-DRS pathway and its regulation. We will identify and characterize cytosolic proteins that interact with newly synthesized substrate proteins in the cytosol. As second part, we will test the function of mitochondrial redox proteins in the IMS, such as the thioredoxin system and the peroxidase Hyr1, and analyze their role in the Mia40/Erv1 import pathway.The second objective is to characterize the link between the physiological function of the Mia40/Erv1-disulfide relay system and the disease phenotype observed in patients with mutations in human ERV1. By studying the consequences of these mutations in the yeast model system and in patients fibroblasts, we will elucidate the molecular basis of the disease phenotype.We have shown that the Mia40/Erv1-DRS has a broader substrate specificity than previously thought. The third objective is to identify and characterize novel substrates of the yeast DRS and to characterize the import of IMS proteins that lack sequence features of substrates with known import pathways.By identifying cytosolic proteins interacting with DRS substrates and by elucidating the function of redox proteins in the DRS import pathway we will provide valuable insights into this pathway and its regulation. The studies, to identify novel DRS substrates, to characterize the import of IMS proteins with as yet unknown pathway and to elucidate the pathomechanisms of the huERV1 mutants, will contribute to obtain a comprehensive picture of the biogenesis of IMS proteins and their role for mitochondrial physiology and diseases.