Inhibition of the Ubiquitin Transfer Cascade by a Peptidomimetic Foldamer Mimicking the E2 N‑Terminal Helix

The enzymatic cascades for ubiquitin transfer regulate key cellular processes and are the intense focus of drug development for treating cancer and neurodegenerative diseases. E1 is at the apex of the UB transfer cascade, and molecules inhibiting E1 have shown promising activities against cancer cell proliferation. Compared to small molecules, peptidomimetics have emerged as powerful tools to disrupt the protein–protein interactions (PPI) with less drug resistance and high stability in the cell. Herein, we harnessed the D-sulfono-γ-AA peptide to mimic the N-terminal helix of E2 and thereby inhibit E1–E2 interaction. Two stapled peptidomimetics, M1–S1 and M1–S2, were identified as effective inhibitors to block UB transfer from E1 to E2, as shown by in vitro and cellular assays. Our work suggested that PPIs with the N-terminal helix of E2 at the E1–E2 and E2–E3 interfaces could be a promising target for designing inhibitors against protein ubiquitination pathways in the cell.

介导泛素（ubiquitin, UB）转移的酶级联反应调控着诸多关键细胞生理过程，亦是当前癌症与神经退行性疾病治疗药物研发的核心聚焦方向。泛素激活酶（E1）处于UB转移级联反应的核心位点，靶向E1的抑制剂分子已在抑制癌细胞增殖方面展现出良好活性。相较于传统小分子化合物，拟肽类化合物已成为阻断蛋白质-蛋白质相互作用（protein-protein interactions, PPI）的强效工具，其具备更低的耐药性与更优的胞内稳定性。本研究利用D-磺酰基-γ-AA肽模拟泛素结合酶（E2）的N端螺旋结构，以此实现对E1-E2相互作用的抑制。经体外实验与细胞实验验证，两款钉合拟肽M1–S1与M1–S2可有效阻断UB从E1向E2的转移过程。本研究结果表明，靶向E1-E2与E2-E3相互作用界面中E2的N端螺旋结构的蛋白质-蛋白质相互作用，有望成为设计胞内蛋白质泛素化通路抑制剂的极具潜力的靶点。