Chemical Inhibitors of Protein Translocation

为了开发蛋白质转运的新方法和新探针，我们一直在开发在体内调节这一过程的药理学方法。我们最近合成并表征了一种新型的小分子共翻译蛋白易位抑制剂。这种化合物(称为辅酶转运蛋白)在体外和培养细胞中都被证明能抑制某些蛋白质的移位，但不能抑制其他蛋白质的移位。值得注意的是，这种底物特异性被发现编码在信号序列中。因此，对辅酶转运蛋白的敏感性或抗性可以简单地通过选择信号来赋予任何感兴趣的蛋白质。辅酶转运蛋白的靶标已经确定，似乎是蛋白质转位通道的中心成分Sec61复合体。这些工具和发现现在为选择性和有效地调节活细胞中单个底物的移位开辟了道路。这种方法现在被应用于研究蛋白质转位在各种细胞事件中的作用，如蛋白质聚集和毒性、蛋白质降解以及细胞对内质网应激的反应。此外，辅酶转运蛋白的类似物现在正在测试它们在各种底物上的作用，以确定是否可以调节抑制的特异性。最后，辅酶转运蛋白正被用作一种工具来剖析信号序列与转运子相互作用的机制基础，这是蛋白质易位的决定性步骤。

To develop new methods and probes for protein translocation, we have been developing pharmacologic methods of modulating this process in vivo. We have recently synthesized and characterized a novel small molecule inhibitor of cotranslational protein translocation. This compound (called cotransin) was demonstrated both in vitro and in cultured cells to inihibit the translocation of some, but not other proteins. Remarkably, this substrate-specificity was found to be encoded in the signal sequence. Thus, the sensitivity or resistance to cotransin can be conferred to any protein of interest simply by the choice of signal. The target of cotransin has been identified, and appears to be the Sec61 complex, the central component of the protein translocation channel. These tools and findings now open the way to selectively and potently modulate the translocation of individual substrates in live cells. This approach is now being applied to study the role of protein translocation in various cellular events such a protein aggregation and toxicity, protein degradation, and the cellular response to ER stress. In addition, analogoues of cotransin are now being tested for their effects on a variety of substrates to determine whether specificity of inhibition can be modulated. And finally, cotransin is being used as a tool to dissect the mechanistic basis of signal sequence interaction with the translocon, a decisive step in protein translocation.