Structural Tailoring of a Novel Fluorescent IRE‑1 RNase Inhibitor to Precisely Control Its Activity

• Published in: Journal of medicinal chemistry 2019-06, Vol.62 (11), p.5404-5413
• Main Authors: Shao, Andong, Kang, Chang Won, Tang, Chih-Hang Anthony, Cain, Christopher F, Xu, Qin, Phoumyvong, Claire M, Del Valle, Juan R, Hu, Chih-Chi Andrew
• Format: Article
• Language: English
• ISSN: 0022-2623; 1520-4804
• DOI: 10.1021/acs.jmedchem.9b00269

Activation of the IRE-1/XBP-1 pathway has been linked to many human diseases. We report a novel fluorescent tricyclic chromenone inhibitor, D-F07, in which we incorporated a 9-methoxy group onto the chromenone core to enhance its potency and masked the aldehyde to achieve long-term efficacy. Protection of the aldehyde as a 1,3-dioxane acetal led to strong fluorescence emitted by the coumarin chromophore, enabling D-F07 to be tracked inside the cell. We installed a photolabile structural cage on the hydroxy group of D-F07 to generate PC-D-F07. Such a modification significantly stabilized the 1,3-dioxane acetal protecting group, allowing for specific stimulus-mediated control of inhibitory activity. Upon photoactivation, the re-exposed hydroxy group on D-F07 triggered the aldehyde-protecting 1,3-dioxane acetal to slowly decompose, leading to the inhibition of the RNase activity of IRE-1. Our novel findings will also allow for spatiotemporal control of the inhibitory effect of other salicylaldehyde-based compounds currently in development.