Biochemie Intrazellulärer Transportprozesse, Ruhr-Universität Bochum, Universitätsstr. 150, D-44780 Bochum, Germany.
Systembiochemie, Ruhr-Universität Bochum, Universitätsstr. 150, D-44780 Bochum, Germany.
Biochimie. 2014 Mar;98:16-28. doi: 10.1016/j.biochi.2013.12.009. Epub 2013 Dec 15.
The biogenesis of peroxisomes is an ubiquitin-dependent process. In particular, the import of matrix proteins into the peroxisomal lumen requires the modification of import receptors with ubiquitin. The matrix proteins are synthesized on free polyribosomes in the cytosol and are recognized by import receptors via a peroxisomal targeting sequence (PTS). Subsequent to the transport of the receptor/cargo-complex to the peroxisomal membrane and the release of the cargo into the peroxisomal lumen, the PTS-receptors are exported back to the cytosol for further rounds of matrix protein import. The exportomer represents the molecular machinery required for the retrotranslocation of the PTS-receptors. It comprises enzymes for the ubiquitination as well as for the ATP-dependent extraction of the PTS-receptors from the peroxisomal membrane. Furthermore, recent evidence indicates a mechanistic interconnection of the ATP-dependent removal of the PTS-receptors with the translocation of the matrix protein into the organellar lumen. Interestingly, the components of the peroxisomal exportomer seem also to be involved in cellular tasks that are distinct from the ubiquitination and dislocation of the peroxisomal PTS-receptors. This includes work that indicates a central function of this machinery in the export of peroxisomal matrix proteins in plants, while a subset of exportomer components is involved in the meiocyte formation in some fungi, the peroxisome-chloroplast contact during photorespiration in plants and possibly even the selective degradation of peroxisomes via pexophagy. In this review, we want to discuss the central role of the exportomer during matrix protein import, but also highlight distinct roles of exportomer constituents in additional cellular processes. This article is part of a Special Issue entitled: Peroxisomes: biogenesis, functions and diseases.
过氧化物酶体的生物发生是一个泛素依赖性的过程。特别是，基质蛋白向过氧化物酶体腔中的导入需要通过泛素对导入受体进行修饰。基质蛋白在细胞质中的游离多核糖体上合成，并通过过氧化物酶体靶向序列 (PTS) 被导入受体识别。在受体/货物复合物被转运到过氧化物酶体膜并将货物释放到过氧化物酶体腔中之后，PTS 受体被输出回细胞质，以便进行下一轮基质蛋白的导入。外排体代表 PTS 受体反向转运所需的分子机制。它包含用于泛素化以及用于 PTS 受体从过氧化物酶体膜上 ATP 依赖性提取的酶。此外，最近的证据表明，PTS 受体的 ATP 依赖性去除与基质蛋白向细胞器腔中的移位之间存在机制上的联系。有趣的是，过氧化物酶体外排体的组成部分似乎也参与了与泛素化和过氧化物酶体 PTS 受体的脱位不同的细胞任务。这包括表明该机制在植物过氧化物酶体基质蛋白的输出中的核心功能的工作，而外排体成分的子集参与了一些真菌中的减数分裂形成、植物光合作用呼吸期间的过氧化物酶体-叶绿体接触，甚至可能通过过氧化物酶体自噬进行过氧化物酶体的选择性降解。在这篇综述中，我们希望讨论外排体在基质蛋白导入过程中的核心作用，但也要强调外排体成分在其他细胞过程中的独特作用。本文是题为“过氧化物酶体：生物发生、功能和疾病”的特刊的一部分。
