Covalent Reprogramming of Kinase Binders to Modulate Protein Homeostasis.

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.