Selective Stalling of Human Translation by Small Molecules

摘要 许多人类疾病的蛋白质靶标由于其潜在的生化行为而仍然是“不可用药的”。 小分子药物发现的这些限制阻碍了开发负担得起的治疗方法的希望。 在这里，我们建议开发一种全新的作用机制， 通过选择性地阻断人类核糖体对“不可用药的”蛋白质的翻译。大多数毒品和毒品 已知调节人翻译靶翻译起始因子复合物或上游的候选物 信号通路，如哺乳动物雷帕霉素靶蛋白（mTOR）。这些通常会调节 大量的mRNA。到目前为止，只有一种类型的化合物，选择性靶向核糖体-诱导 提前终止密码子通读-正在临床上进行评估。我们最近证明， 分子可以选择性地停止人类蛋白质的翻译，而几乎没有脱靶活性。的 我们分析的化合物PF-06446846（PF 846）直接选择性抑制PCSK 9的翻译 在翻译延伸过程中，通过使核糖体停滞在核糖体出口处的新生多肽上， 隧道然而，目前尚不清楚这种化合物和相关化合物如何选择性地阻止翻译。为数不多 我们鉴定出的被PF 846停滞的脱靶蛋白的例子（不到人类的0.4%）， 蛋白质组）表现出实质性的一级结构变异性，使得难以预测用于 选择性核糖体靶向药物的未来发展。我们有初步证据表明PF 846 用这些不同的新生链序列通过微妙的不同机制诱导核糖体停滞。我们 我建议阐明PF 846翻译停滞的完整分子机制，以便这个家族的 化合物可以进一步优化以靶向其表达或过表达引起多种疾病的蛋白质 人类疾病，目前还没有治疗方法。这类化合物也可以优化 以病毒为目标，这些病毒使用人类翻译来合成它们的蛋白质组。这些努力有可能 为人类治疗开发开辟了一个全新的作用机制。

ABSTRACT Protein targets for many human diseases remain “undruggable” due to their underlying biochemical behavior. These limits to discovery of small molecule drugs hold back the promise of developing affordable therapeutics. Here we propose to develop an entirely new mechanism of action that could enable targeting previously “undruggable” proteins, by selectively blocking their translation by the human ribosome. Most drugs and drug candidates known to modulate human translation target translation initiation factor complexes or upstream signaling pathways such as mammalian target of Rapamycin (mTOR). These generally modulate translation of a large number of mRNAs. To date, only one type of compound that selectively targets the ribosome–to induce premature stop codon readthrough–is being evaluated in the clinic. We recently demonstrated that small molecules can selectively stall the translation of human proteins, with very little off-target activity. The compound we analyzed, PF-06446846 (PF846), directly and selectively inhibits the translation of PCSK9 during translation elongation, by stalling the ribosome on the nascent polypeptide residing in the ribosome exit tunnel. However, it remains unclear how this and related compounds selectively stall translation. The few examples of off-target proteins we identified as stalled by PF846 (less than 0.4 percent of the human proteome) exhibit substantial primary structure variability, making it difficult to predict target sequences for future development of selective ribosome-targeting drugs. We have preliminary evidence that PF846 interacts with these diverse nascent chain sequences to induce ribosome stalling by subtly different mechanisms. We propose to elucidate the full molecular mechanism of PF846 stalling of translation, so that this family of compounds can be further optimized to target proteins whose expression or overexpression causes diverse human diseases for which no treatments are now available. This family of compounds could also be optimized to target viruses, which use human translation to synthesize their proteome. These efforts have the potential to open up an entirely new mechanism of action for human therapeutic development.