Grindheim Ann Kari, Patil Sudarshan S, Nebigil Canan G, Désaubry Laurent, Vedeler Anni
Department of Biomedicine, Faculty of Medicine, University of Bergen, Bergen, Norway.
Regenerative Nanomedicine Laboratory (UMR1260), Faculty of Medicine, FMTS, INSERM-University of Strasbourg, Strasbourg, France.
Front Cell Dev Biol. 2023 May 12;11:1094941. doi: 10.3389/fcell.2023.1094941. eCollection 2023.
Annexin A2 (AnxA2) plays a critical role in cell transformation, immune response, and resistance to cancer therapy. Besides functioning as a calcium- and lipidbinding protein, AnxA2 also acts as an mRNA-binding protein, for instance, by interacting with regulatory regions of specific cytoskeleton-associated mRNAs. Nanomolar concentrations of FL3, an inhibitor of the translation factor eIF4A, transiently increases the expression of AnxA2 in PC12 cells and stimulates shortterm transcription/translation of anxA2 mRNA in the rabbit reticulocyte lysate. AnxA2 regulates the translation of its cognate mRNA by a feed-back mechanism, which can partly be relieved by FL3. Results obtained using the holdup chromatographic retention assay results suggest that AnxA2 interacts transiently with eIF4E (possibly eIF4G) and PABP in an RNA-independent manner while cap pulldown experiments indicate a more stable RNA-dependent interaction. Short-term (2 h) treatment of PC12 cells with FL3 increases the amount of eIF4A in cap pulldown complexes of total lysates, but not of the cytoskeletal fraction. AnxA2 is only present in cap analogue-purified initiation complexes from the cytoskeletal fraction and not total lysates confirming that AnxA2 binds to a specific subpopulation of mRNAs. Thus, AnxA2 interacts with PABP1 and subunits of the initiation complex eIF4F, explaining its inhibitory effect on translation by preventing the formation of the full eIF4F complex. This interaction appears to be modulated by FL3. These novel findings shed light on the regulation of translation by AnxA2 and contribute to a better understanding of the mechanism of action of eIF4A inhibitors.
膜联蛋白A2（AnxA2）在细胞转化、免疫反应及癌症治疗抗性中发挥关键作用。除了作为一种钙结合和脂质结合蛋白发挥作用外，AnxA2还作为一种mRNA结合蛋白，例如，通过与特定细胞骨架相关mRNA的调控区域相互作用。纳摩尔浓度的FL3是翻译因子eIF4A的抑制剂，它能短暂增加PC12细胞中AnxA2的表达，并刺激兔网织红细胞裂解液中anxA2 mRNA的短期转录/翻译。AnxA2通过一种反馈机制调节其同源mRNA的翻译，而FL3可部分解除这种反馈机制。滞留色谱保留分析结果表明，AnxA2以RNA非依赖的方式与eIF4E（可能还有eIF4G）和PABP短暂相互作用，而帽下拉实验表明存在更稳定的RNA依赖相互作用。用FL3对PC12细胞进行短期（2小时）处理，可增加总裂解物帽下拉复合物中eIF4A的量，但细胞骨架部分的帽下拉复合物中eIF4A的量未增加。AnxA2仅存在于细胞骨架部分帽类似物纯化的起始复合物中，而不存在于总裂解物中，这证实AnxA2与特定的mRNA亚群结合。因此，AnxA2与PABP1和起始复合物eIF4F的亚基相互作用，解释了其通过阻止完整eIF4F复合物的形成而对翻译产生的抑制作用。这种相互作用似乎受FL3调节。这些新发现揭示了AnxA2对翻译的调控作用，有助于更好地理解eIF4A抑制剂的作用机制。
