PDF(Pubmed)
Abstract：
Regulation of mRNA translation is a crucial step in controlling gene expression in stressed cells, impacting many pathologies, including heart ischemia. In recent years, ribosome heterogeneity has emerged as a key control mechanism driving the translation of subsets of mRNAs. In this study, we investigated variations in ribosome composition in human cardiomyocytes subjected to endoplasmic reticulum stress induced by tunicamycin treatment. Our findings demonstrate that this stress inhibits global translation in cardiomyocytes while activating internal ribosome entry site (IRES)-dependent translation. Analysis of translating ribosome composition in stressed and unstressed cardiomyocytes was conducted using mass spectrometry. We observed no significant changes in ribosomal protein composition, but several mitochondrial ribosomal proteins (MRPs) were identified in cytosolic polysomes, showing drastic variations between stressed and unstressed cells. The most notable increase in polysomes of stressed cells was observed in MRPS15. Its interaction with ribosomal proteins was confirmed by proximity ligation assay (PLA) and immunoprecipitation, suggesting its intrinsic role as a ribosomal component during stress. Knock-down or overexpression experiments of MRPS15 revealed its role as an activator of IRES-dependent translation. Furthermore, polysome profiling after immunoprecipitation with anti-MRPS15 antibody revealed that the \"MRPS15 ribosome\" is specialized in translating mRNAs involved in the unfolded protein response.
摘要：
mRNA翻译的调节是控制应激细胞中基因表达的关键步骤，影响许多病理，包括心脏缺血.近年来,核糖体异质性已成为驱动mRNAs亚群翻译的关键控制机制。在这项研究中,我们研究了衣霉素治疗引起的内质网应激的人心肌细胞中核糖体组成的变化。我们的发现表明，这种压力抑制了心肌细胞的整体翻译，同时激活了内部核糖体进入位点（IRES）依赖性翻译。使用质谱法进行应激和非应激心肌细胞中翻译核糖体组成的分析。我们观察到核糖体蛋白组成没有显著变化，但是一些线粒体核糖体蛋白（MRP）在胞质多体中被鉴定出来，显示应力和非应力细胞之间的剧烈变化。在MRPS15中观察到应激细胞的多聚体的最显著增加。通过邻近连接测定（PLA）和免疫沉淀证实了其与核糖体蛋白的相互作用，表明其在应激过程中作为核糖体成分的内在作用。MRPS15的敲低或过表达实验揭示了其作为IRES依赖性翻译的激活剂的作用。此外，用抗MRPS15抗体免疫沉淀后的多聚体谱分析表明，“MRPS15核糖体”专门翻译与未折叠蛋白反应有关的mRNA。
