DCAF11-dependent molecular glue degrader activated by glutathionylation.

Selective and Potent First-in-Class CRBN-Dependent Molecular Glue Degraders of WW Domain-Binding Protein 4.

Targeted protein degradation via molecular glues represents a powerful modality for modulating "undruggable" proteins. Herein, through proteomic profiling of a CRBN-binding library and rigorous structure-activity relationship (SAR) refinement, we report the discovery of dWBP4-1: a first-in-class, highly selective, CRBN-dependent molecular glue degrader of the spliceosome-associated scaffold protein WBP4. dWBP4-1 induces rapid, nanomolar degradation of WBP4 via a canonical G-loop-mediated mechanism, exhibiting exceptional proteome-wide selectivity with negligible transcriptomic or alternative splicing perturbation. Leveraging this highly specific target-glue interaction, we mapped the minimal WBP4 degron to a 41-amino-acid sequence to establish a compact, inducible chemical-genetic platform termed wTAG. When fused to diverse proteins of interest, wTAG enables robust, monotonic degradation devoid of the hook effect. While the wTAG system is highly versatile, we delineate its boundaries when applied to challenging targets like Cyclin D1, where factors such as steric hindrance, lysine availability, complex sequestration, and tag accessibility (N- vs. C-terminal fusion) must be carefully interrogated. Collectively, this study highlights the discovery of a highly selective WBP4 molecular glue and translates its underlying degron into a robust tool for precise protein control.

Two Mechanisms One Molecule: Developing a 'Truly' Bifunctional Degrader Targeting Rpn13 and CRBN.

Targeted protein degradation (TPD) has emerged as a powerful strategy to eliminate disease-relevant proteins, yet current approaches remain largely constrained to hijacking ubiquitin ligases. We previously introduced ByeTACs, bifunctional molecules that directly recruit proteins to the proteasome for E-ligase independent degradation. Here, we report "Truly" degraders, a new class of dual-mechanism molecules that combine a ligand for the proteasomal receptor Rpn13 with a ligand for cereblon (CRBN) to simultaneously engage both ubiquitin-independent and ubiquitin-dependent degradation pathways. Structure-guided design identified an optimal linker length that supports efficient substrate processing, with the PEG4 derivative (Truly-4) inducing robust depletion of both Rpn13 and CRBN in several cancer cell types. Remarkably, Truly-4 is the first noncovalent small molecule shown to degrade full-length Rpn13, a target previously approached using covalent or domain-restricted strategies. Mechanistic studies confirmed that degradation of Rpn13 proceeds via CRBN-dependent E3 ligase activity, whereas CRBN degradation occurs through an E-ligase independent process, consistent with a ByeTAC mechanism. Importantly, Truly-4 induces selective cytotoxicity in hematologic and solid cancer cell lines but not in healthy cells, despite comparable Rpn13 depletion, indicating that dual degradation can uncouple target engagement from toxicity. These findings establish a generalizable framework for engineering bifunctional degraders that program the proteasome to execute parallel degradation mechanisms and highlight proteasome receptors as druggable nodes for selective destruction of disease-relevant proteins.

Identification of a Ubiquitin-Independent Degron by a Reporter Assay.

A New Recruitable E3 Ligase UHRF1 Supporting Targeted Protein Degradation: A Minimal Azide as a Recruitment Ligand

ABSTRACT Targeted protein degradation represents a promising therapeutic strategy, yet its broader application is often limited by the scarcity of usable E3 ligases. Glutathione peroxidase 4 (GPX4) is a key target for inducing ferroptosis, but achieving sustained and potent inhibition remains challenging with conventional enzymatic inhibitors. Herein, we report the first small‐molecule GPX4 degraders that incorporate either electrophilic warheads or a minimal azide group as an E3 recruitment ligand. The azide‐based degrader DK‐5070 effectively drives potent GPX4 degradation, achieving a DC50 of 17.4 nM and a Dmax of 84%, thereby outperforming larger PROTAC‐based degraders. Notably, DK‑5070 exhibits potent antitumor activity both in vitro (IC50 = 47.21 nM) and in vivo (TGI = 41.8%), demonstrating significant efficacy as a GPX4 degrader. Mechanistic studies reveal that degradation is mediated through recruitment of the oncogenic E3 ligase UHRF1, which is frequently overexpressed in tumors, underscoring the potential for tumor‐specific protein degradation. This demonstrated small‐molecule degraders that recruit UHRF1 to facilitate targeted degradation of GPX4. In this system, the azide group functions as a minimal recruitment ligand, thereby expanding the E3 ligase toolbox and offering a promising strategy for targeted cancer therapy.

Post-translational chemical modification of E3 ligase for efficient target protein degradation.

This work reports the first ligand-directed chemical strategy that converts transient PROTAC-mediated ternary complex formation into binary target recognition via post-translational chemical modification of an E3 ligase, and believes it could provide a platform for next-generation targeted protein degraders to overcome the current limitation of PROTAC approach.

Reprogramming VHL with molecular glues enables selective degradation of caspase-2

Molecular glue degraders (MGDs) reprogram E3 ligases to eliminate neosubstrates, yet their application has largely been confined to CRBN. Here, we identify caspase-2 as a new neosubstrate for von Hippel-Lindau (VHL), expanding the scope of VHL-based MGDs. Guided by a focused VHL ligand library design, we employed TurboID-based proximity labeling to discover stereoisomeric compounds (dCASP2-1 and dCASP2-2) that selectively recruit caspase-2 to VHL and promote its ubiquitin-proteasome system-dependent degradation. Further structure-activity relationship (SAR) studies yielded dCASP2-3 and dCASP2-4, which enhanced degradation potency (by 622-fold relative to dCASP2-1) and abolished enantioselectivity. Mechanistic mapping localized the degrader-induced interface to a two-helix region of the caspase-2 CARD domain, with residues H33, P34, and D100 essential for VHL engagement. Degron-guided computational modeling of the VHL/MGD/caspase-2 ternary complex provided structural insight into neosubstrate recognition. Together, we report the development of VHL molecular glues that selectively and potently degrade caspase-2, offering chemical probes to interrogate its functions in apoptosis and stress responses, while broadening the substrate landscape of VHL-based MGDs.