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Updated: May 6, 2026
A Fluorescence-based Lymphocyte Assay Suitable for High-throughput Screening of Small Molecules
Published on: March 10, 2017
Development of a fluorescence polarization based high-throughput assay to identify Casitas B-lineage lymphoma RING
Xingliang Xie1, Lin Sun, Ziyan Yuan Pessetto
1Department of Pharmacy, Chengdu Medical College, Chengdu, Sichuan Province, China.
Abstract:
The E3 ubiquitin protein ligase Casitas B-lineage Lymphoma (Cbl) proteins and their binding partners play an important role in regulating signal transduction pathways. It is important to utilize regulators to study the protein-protein interactions (PPIs) between these proteins. However, finding specific small-molecule regulators of PPIs remains a significant challenge due to the fact that the interfaces involved in PPIs are not well suited for effective small molecule binding. We report the development of a competitive, homogeneous, high-throughput fluorescence polarization (FP) assay to identify small molecule regulators of Cbl (RING) domain. The FP assay was used to measure binding affinities and inhibition constants of UbCH7 peptides and small molecule regulators of Cbl (RING) domains, respectively. In order to rule out promiscuous, aggregation-based inhibition, two assay conditions were developed and compared side by side. Under optimized conditions, we screened a 10,000 natural compound library in detergent-free and detergent-present (0.01% Triton X-100) systems. The results indicate that the detergent-present system is more suitable for high-throughput screens. Three potential compounds, methylprotodioscin, leonuride and catalpol, have been identified that bind to Cbl (RING) domain and interfere with the Cbl (RING)-UbCH7 protein-protein interaction.
Insights
Researchers developed a high-throughput fluorescence polarization assay to find small molecules regulating Casitas B-lineage Lymphoma (Cbl) protein interactions. Three compounds were identified that bind to the Cbl (RING) domain and disrupt Cbl-UbCH7 protein interactions.
Area of Science:
- Biochemistry
- Molecular Biology
- Pharmacology
Background:
- Casitas B-lineage Lymphoma (Cbl) proteins are E3 ubiquitin ligases crucial for signal transduction.
- Studying protein-protein interactions (PPIs) involving Cbl proteins is vital for understanding cellular signaling.
- Identifying small-molecule regulators of PPIs is challenging due to the nature of PPI interfaces.
Purpose of the Study:
- To develop a high-throughput screening assay for identifying small-molecule regulators of Cbl (RING) domain interactions.
- To measure binding affinities and inhibition constants for Cbl (RING) domain and its interacting partners.
- To discover novel compounds that modulate Cbl (RING)-UbCH7 protein-protein interactions.
Main Methods:
- Development of a competitive, homogeneous, high-throughput fluorescence polarization (FP) assay.
- Optimization of assay conditions, comparing detergent-free and detergent-present systems.
- Screening of a 10,000 natural compound library using the optimized FP assay.
Main Results:
- The detergent-present system proved more effective for high-throughput screening.
- Three compounds—methylprotodioscin, leonuride, and catalpol—were identified as potential binders to the Cbl (RING) domain.
- These compounds demonstrated interference with the Cbl (RING)-UbCH7 protein-protein interaction.
Conclusions:
- A robust FP assay was established for high-throughput screening of Cbl (RING) domain regulators.
- Novel small molecules capable of modulating Cbl (RING)-UbCH7 interactions were discovered.
- These findings provide a foundation for developing targeted therapeutics modulating Cbl-mediated signaling pathways.
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