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Published on: August 27, 2021
Development of High-Affinity Ligands for Human UBR2
Shih-Ting Huang1, Abdelfattah Faouzi, Nicole Thomas
1Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093-0021, United States.
Abstract:
UBR box-containing ubiquitin E3 ligases recognize the N-termini of their target proteins through the UBR box, and a member of the family, UBR2, has been established as a target to treat cancer- and diabetes-associated cachexia. However, the development of high-affinity small-molecule ligands for UBR2 has not been reported. We developed high-affinity UBR2 ligands through a peptidomimetic approach by incorporating unnatural amino acids to obtain ligands that bind to UBR2 with Kd ∼ 20-40 nM and with 10-fold selectivity over UBR2's closest homologue, UBR1. High-resolution cocrystal structures (∼1.2 Å) of UBR2 in complexes with two high-affinity tripeptides revealed molecular mechanisms for their high-affinity binding. Importantly, a high-affinity UBR2 ligand effectively attenuated cancer-induced cachexia in a cellular model. Our findings demonstrate that the UBR boxes are ligandable and thus could spur interest in targeting this class of E3 ligases for developing novel therapeutic approaches for the treatment of cachexia and other illnesses.
Insights
Researchers developed high-affinity small-molecule ligands targeting UBR2, a protein implicated in cancer and diabetes cachexia. These novel ligands show promise for therapeutic development against cachexia by effectively binding UBR2.
Area of Science:
- Biochemistry
- Structural Biology
- Drug Discovery
Background:
- UBR box-containing E3 ligases target protein N-termini.
- UBR2 is a therapeutic target for cachexia associated with cancer and diabetes.
- High-affinity small-molecule ligands for UBR2 are currently lacking.
Purpose of the Study:
- To develop high-affinity small-molecule ligands for UBR2.
- To elucidate the molecular mechanisms of UBR2 ligand binding.
- To evaluate the therapeutic potential of UBR2 ligands in cachexia models.
Main Methods:
- Peptidomimetic approach incorporating unnatural amino acids.
- High-resolution cocrystal structural analysis (∼1.2 Å).
- In vitro binding assays to determine affinity (Kd) and selectivity.
- In vitro cellular models of cancer-induced cachexia.
Main Results:
- Developed UBR2 ligands with high affinity (Kd ∼ 20-40 nM).
- Achieved 10-fold selectivity for UBR2 over its homolog UBR1.
- Determined high-resolution structures revealing binding mechanisms.
- Demonstrated attenuation of cancer-induced cachexia in a cellular model.
Conclusions:
- UBR boxes are druggable targets.
- High-affinity UBR2 ligands can be developed using peptidomimetics.
- These findings support targeting UBR E3 ligases for novel cachexia therapeutics.
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