Key Findings
The study identifies MG-CB2 as the most active covalent molecular glue degrader designed to reduce the abundance of the G protein-coupled receptor CB1R. In MCF-7 breast cancer and HepG2 hepatocellular carcinoma cells, MG-CB2 induced the depletion of CB1R in a concentration- and time-dependent manner. This degradation resulted in reduced cancer-cell viability and migration.
Technical Details
The degraders were developed using rimonabant as a CB1R-binding scaffold, incorporating electrophilic E3 ligase-recruiting handles. The mechanism of action is dependent on the proteasome and the E3 ligase RNF126, as proteasome inhibition and RNF126 knockdown both blocked the loss of CB1R. Cellular engagement was confirmed via rimonabant competition and cellular thermal shift experiments.
Degradation of CB1R led to the modulation of associated signaling pathways, specifically:
- Reduced phosphorylation of ERK and mTOR.
- Decreased expression of the anti-apoptotic protein BCL2.
Background & Context
CB1R is a major regulatory element of the endocannabinoid system, expressed in the central nervous system and peripheral organs including the liver and skeletal muscle. While it regulates mood, appetite, and motor activity, aberrant CB1R signaling is linked to chronic liver disease and cancer. In breast cancer and hepatocellular carcinoma, CB1R upregulation is associated with increased tumor aggressiveness. This occurs because CB1R activates the ERK and mTOR pathways and upregulates BCL2, creating a pro-survival network that inhibits apoptosis and promotes proliferation.
Significance & Outlook
Traditional pharmacological modulators of CB1R are limited to agonists (e.g., THC) or antagonists/inverse agonists (e.g., rimonabant). The development of MG-CB2 demonstrates that covalent molecular glue-mediated degradation can effectively modulate the abundance of a transmembrane GPCR. This establishes a new strategy for targeting disease-associated proteins that were previously managed only through signaling inhibition.
Source: https://doi.org/10.1038/s44386-026-00087-w
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