Synthesis of Unsymmetrical Squaramides as Allosteric GSK-3β Inhibitors Promoting β-Catenin-Mediated Transcription of TCF/LEF in Retinal Pigment Epithelial Cells

The glycogen synthase kinase 3 beta (GSK-3 beta) is a ubiquitous enzyme that is a validated target for the development of potential therapeutics useful in several diseases including retinal degeneration. Aiming at developing an innovative class of allosteric inhibitors of GSK-3 beta potentially useful for retinal degeneration, we explored the class of squaramides. The developed compounds (6 a-l) were obtained through a nontoxic one-pot synthetic protocol, which employs low-cost goods and avoids any purification step. Ethanol was used as the reaction solvent, simultaneously allowing the pure reaction products ' recovery (by precipitation). Out of this set of squaramides, 6 j stood out, from computational and enzymatic converging data, as an ATP non-competitive inhibitor of GSK-3 beta of micromolar potency. When engaged in cellular studies using retinal pigment epithelial cells (ARPE-19) transfected with a luciferase reporter gene under the control of T-cell factor/lymphoid enhancer factor (TCF/LEF) binding sites, 6 j was able to dose-dependently induce beta-catenin nuclear accumulation, as shown by the increased luciferase activity at a concentration of 2.5 mu M.

Automated summary

In this study, a new class of GSK-3β inhibitors was successfully developed through a simple synthetic method, and 6 j showed high activity. In cellular studies, 6 j was able to dose-dependently induce the nuclear accumulation of β-catenin.