Abstract
Small molecules that modulate protein abundance through induced proximity have expanded the landscape beyond traditional inhibition. Here, we explore how introducing covalent or latent electrophilic groups into a multi-kinase binder scaffold can reprogram protein homeostasis within the kinase family. Using the broad-spectrum kinase ligand TL13-87 as a template, we synthesized analogs bearing α-chloroacetamide, acrylamide, or terminal amine groups. Quantitative proteomics revealed that while most analogs had minimal global impact, MKI-AA uniquely stabilized the mitotic kinase AURKA, a protein often destabilized by ATP-competitive inhibitors. Mechanistic studies showed that MKI-AA acts post-translationally to suppress AURKA ubiquitination and proteasomal degradation. Proteomic mapping of MKI-AA-induced AURKA interactors revealed changes in protein associations upon treatment, providing mechanistic insights into how MKI-AA influences AURKA stability. Intriguingly, adding a short linker to MKI-AA converted it from a stabilizer into a degrader, highlighting how subtle structural variations can invert functional outcomes. These findings demonstrate that electrophilic ligand design can modulate kinase stability and reveal a previously unrecognized mode of covalent proximity-driven protein stabilization.