Mia40 and ALR substrates: initial steps in biogenesis and regulation

线粒体的生物发生和维持是细胞活力的基础。我们的特点的生物起源和功能的线粒体膜间空间（IMS）蛋白，这是至关重要的，例如组装的呼吸链，诱导细胞凋亡和钙的稳态。虽然一些IMS蛋白是在线粒体靶向序列（MTS）的帮助下导入的，但大多数蛋白依赖于保守的半胱氨酸和IMS氧化还原酶Mia40的帮助来导入和折叠。Mia40及其巯基氧化酶ALR是最近发现的氧化机制的一部分，其工作方式不同于内质网中的氧化机制。到目前为止，这种机制主要是在体外实验和酵母中阐明的。然而，我们缺乏对许多基本方面的重要见解，包括机制的调节，以及相关的底物网络及其在哺乳动物细胞中的调节。此外，在导入无MTS的Mia40底物之前的胞质过程仍然不清楚。这包括例如识别信号的身份在基板或基板如何被引导到mitochondrial.We最近解决了人类Mia40和ALR的相互作用，从而揭示了他们的底物谱更广泛，他们的许多基板的结构比以前预期的更复杂。同样，我们发现，底物的Mia40表现非常不同的细胞质线粒体进口前相比，含有MTS的基板。在这些令人兴奋的新数据的鼓舞下，我们的目标是接下来识别和表征Mia40底物的胞质相互作用伴侣，这些底物可能参与底物在底物易位到IMS中之前的稳定化、校对和靶向。我们还旨在通过详细描述Mia40和ALR与来自其相互作用组的选定蛋白质的相互作用机制，进一步了解与Mia40和ALR相关的功能。此外，我们将扩展我们的蛋白质组学分析，以确定Mia40和ALR目标在不同的压力条件下，扩大我们的见解，他们的相互作用组的动态。

The biogenesis and maintenance of mitochondria is fundamental for cellular viability. We characterize the biogenesis and function of mitochondrial intermembrane space (IMS) proteins which are crucial for example for the assembly of the respiratory chain, the induction of apoptosis and the homeostasis of calcium. While some IMS proteins are imported with the help of mitochondrial targeting sequences (MTS), most rely on conserved cysteines and the help of the IMS oxidoreductase Mia40 for import and folding. Mia40 and its sulfhydryl oxidase ALR are part of a recently discovered oxidative machinery that works different than the oxidation machinery in the endoplasmic reticulum. So far the mechanics of this machinery have been mainly elucidated in in vitro experiments and in yeast. However, we lack crucial insights into many fundamental aspects which include the regulation of the machinery, and the associated substrate networks and their regulation in mammalian cells. Moreover, the cytosolic processes prior to import of MTS-less Mia40 substrates remain unclear. This includes for example the identity of recognition signals in the substrates or how the substrates are guided to mitochondria.We recently solved the interactomes of human Mia40 and ALR and thereby revealed that their substrate spectrum is much broader and the structure of many of their substrates more complex than previously anticipated. Likewise, we found that substrates of Mia40 behave very different in the cytosol prior to mitochondrial import compared with MTS-containing substrates. Encouraged by these exciting new data we aim to next identify and characterize cytosolic interaction partners of Mia40 substrates that might be involved in stabilization, proof-reading and targeting of the substrates prior to substrate translocation into the IMS. We also aim to understand further functions associated with Mia40 and ALR by characterizing in mechanistic detail their interplay with selected proteins from their interactomes. Furthermore, we will extend our proteomic analyses to identifying Mia40 and ALR targets during different stress conditions to extend our insights on the dynamics of their interactomes.