Discovery of Inhibitor of Wnt Production 2 (IWP-2) and Related Compounds As Selective ATP-Competitive Inhibitors of Casein Kinase 1 (CK1) δ/ε

Inhibitors of Wnt production (IWPs) are known antagonists of the Wnt pathway, targeting the membrane-bound O-acyltransferase porcupine (Porcn) and thus preventing a crucial Wnt ligand palmitoylation. Since IWPs show structural similarities to benzimidazole-based CK1 inhibitors, we hypothesized that IWPs could also inhibit CK1 isoforms. Molecular modeling revealed a plausible binding mode of IWP-2 in the ATP binding pocket of CK1δ which was confirmed by X-ray analysis. In vitro kinase assays demonstrated IWPs to be ATP-competitive inhibitors of wtCK1δ. IWPs also strongly inhibited the gatekeeper mutant M82FCK1δ. When profiled in a panel of 320 kinases, IWP-2 specifically inhibited CK1δ. IWP-2 and IWP-4 also inhibited the viability of various cancer cell lines. By a medicinal chemistry approach, we developed improved IWP-derived CK1 inhibitors. Our results suggest that the effects of IWPs are not limited to Porcn, but also might influence CK1δ/ε-related pathways.

Wnt生成抑制剂（IWPs）是一类已知的Wnt通路拮抗剂，其靶向膜结合O-酰基转移酶Porcupine（Porcn），从而阻断关键的Wnt配体棕榈酰化修饰。由于IWPs与苯并咪唑类酪蛋白激酶1（Casein Kinase 1，CK1）抑制剂具有结构相似性，我们推测IWPs同样能够抑制CK1同工型。分子模拟显示，IWP-2在CK1δ的ATP结合口袋中存在合理的结合模式，该结果经X射线晶体学分析得以验证。体外激酶实验证实，IWPs是野生型CK1δ（wtCK1δ）的ATP竞争性抑制剂。IWPs同时能够强效抑制CK1δ的守门人突变体M82F。在包含320种激酶的筛选面板中进行表征时，IWP-2仅特异性抑制CK1δ。IWP-2与IWP-4同样能够抑制多种癌细胞系的增殖活力。本研究通过药物化学策略开发了经优化的、源自IWPs的CK1抑制剂。本研究结果表明，IWPs的生物学效应并非仅局限于Porcn，同时还可能影响CK1δ/ε相关的信号通路。