The reversible phosphorylation of proteins controls most cellular functions. Protein kinases have been popular drug targets, unlike phosphatases, which remain a drug discovery challenge. Guanabenz and Sephin1 are selective inhibitors of the phosphatase regulatory subunit PPP1R15A (R15A) that prolong the benefit of eIF2α phosphorylation, thereby protecting cells from proteostatic defects. In mice, Sephin1 prevents two neurodegenerative diseases, Charcot–Marie–Tooth 1B (CMT-1B) and SOD1-mediated amyotrophic lateral sclerosis (ALS). However, the molecular basis for R15A inhibition is unknown. Here we reconstituted human recombinant eIF2α holophosphatases, R15A–PP1 and R15B–PP1, whose activity depends on both the catalytic subunit PP1 (protein phosphatase 1) and either R15A or R15B. This system enabled the functional characterization of these holophosphatases and revealed that Guanabenz and Sephin1 induced a selective conformational change in R15A, detected by resistance to limited proteolysis. This altered the recruitment of eIF2α, preventing its dephosphorylation. This work demonstrates that regulatory subunits of phosphatases are valid drug targets and provides the molecular rationale to expand this concept to other phosphatases.

中文翻译：

---

解码eIF2α整体磷酸酶和PPP1R15A抑制剂的选择性

蛋白质的可逆磷酸化控制大多数细胞功能。与磷酸酶不同，蛋白激酶一直是受欢迎的药物靶标，而磷酸酶仍然是药物开发的挑战。胍那苄和Sephin1是磷酸酶调节亚基PPP1R15A（R15A）的选择性抑制剂，其延长的eIF2的益处α磷酸化，从而保护细胞免受proteostatic缺陷。在小鼠中，Sephin1可预防两种神经退行性疾病，Charcot–Marie–Tooth 1B（CMT-1B）和SOD1介导的肌萎缩性侧索硬化症（ALS）。但是，R15A抑制的分子基础是未知的。在这里，我们重组人重组的eIF2 α整体磷酸酶，R15A–PP1和R15B–PP1，其活性取决于催化亚基PP1（蛋白质磷酸酶1）和R15A或R15B。该系统能够对这些全磷酸酶进行功能表征，并揭示了瓜纳本斯和Sephin1诱导了R15A的选择性构象变化，这是通过对有限蛋白水解的抗性来检测的。这种改变的eIF2招聘α，防止其去磷酸化。这项工作证明磷酸酶的调节亚基是有效的药物靶标，并提供了将这一概念扩展到其他磷酸酶的分子原理。