CLU1: a regulator of mitochondrial distribution and translation of nuclear-encoded mitochondrial proteins

线粒体是必不可少的细胞器，参与ATP的产生、关键的代谢过程、钙缓冲和细胞死亡。线粒体在细胞中的分布对其功能至关重要，特别是在高度极化的细胞如神经元中，线粒体需要长途跋涉才能到达轴突和树突中ATP需求量高的区域。绝大多数线粒体蛋白在细胞质中合成，然后输入细胞器。这就提出了一个重要的问题，核编码线粒体蛋白的合成是否发生在靠近细胞器的地方。我们已经确定哺乳动物CLU1作为候选分子调节核编码线粒体蛋白的翻译和线粒体分布。从拟南芥到人类，CLU1在进化过程中高度保守。在植物、酵母和果蝇中，CLU1敲除导致线粒体聚集在靠近细胞核的地方。我们有证据表明，哺乳动物的CLU1可以类似地影响细胞中的线粒体分布。此外，我们发现CLU1是一种直接结合RNA的核糖体相关蛋白。此外，CLU1与astrin-SKAP复合物相互作用，参与有丝分裂过程中着丝点的分离。一个有吸引力的假设是，CLU1可能调节核编码线粒体蛋白的翻译，或靠近线粒体的核糖核粒子亚群的运输，从而影响线粒体分布。在此，我们建议：1)通过鉴定与CLU1结合的靶mrna并进行多聚体分析来评估其在不同条件下的翻译效率，研究CLU1在调节核编码线粒体蛋白翻译中的可能作用；2)确定CLU1与astrin-SKAP复合物相互作用的作用；3)评估cla1基因敲除对小鼠体内不同组织的生理影响。

Mitochondria are essential organelles, implicated in ATP production, crucial metabolic processes, calcium buffering, and cell death. Mitochondria distribution in cells is crucial for their function, especially in highly polarized cells as neurons, where mitochondria travel long distances to reach regions of high ATP demand in axons and dendrites. The vast majority of mitochondrial proteins are synthesized in the cytosol and imported in the organelle. This raises the important question whether synthesis of nuclear-encoded mitochondrial proteins occurs close to the organelle. We have identified mammalian CLU1 as a candidate molecule regulating both translation of nuclear encoded mitochondrial proteins and mitochondrial distribution. CLU1 is highly conserved during evolution, from Arabidopsis thaliana to humans. In plant, yeast, and Drosophila melanogaster, CLU1 knock-out leads to clustering of mitochondria close to the nucleus. We have evidence that mammalian CLU1 can similarly affect mitochondrial distribution in cells. Moreover, we find that CLU1 is a ribosomal-associated protein, which directly binds RNA. In addition, CLU1 interacts with the astrin-SKAP complex, which is implicated in kinetochore separation during mitosis. An attractive hypothesis is that CLU1 might regulate the translation of nuclear-encoded mitochondrial proteins, or the transport of a subset of ribonucleoparticles close to mitochondria, thereby affecting mitochondrial distribution. Here we propose to: 1) investigate a possible the role of CLU1 in regulation of translation of nuclear-encoded mitochondrial proteins, by identifying target mRNAs which are bound by CLU1 and performing polysome profiling to assess the efficiency of their translation under different conditions; 2) identify the role of CLU1 interaction with the astrin-SKAP complex; 3) assess the physiological consequences of CLU1 knock-out in vivo in different tissues of the mouse.