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Updated: Jul 15, 2025
Spectrophotometric Screening for Potential Inhibitors of Cytosolic Glutathione S-Transferases
Published on: October 10, 2020
Covalent Targeting of Glutamate Cysteine Ligase to Inhibit Glutathione Synthesis
Lydia H Zhang1,2, Michelle Tang2,3, Xavier Tao2,4
1Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, CA, 94720, USA.
Abstract:
Dysregulated oxidative stress plays a major role in cancer pathogenesis and some types of cancer cells are particularly vulnerable to inhibition of their cellular antioxidant capacity. Glutamate-cysteine ligase (GCL) is the first and rate-limiting step in the synthesis of the major cellular antioxidant glutathione (GSH). Developing a GCL inhibitor may be an attractive therapeutic strategy for certain cancer types that are particularly sensitive to oxidative stress. In this study, we reveal a cysteine-reactive ligand, EN25, that covalently targets an allosteric cysteine C114 on GCLM, the modifier subunit of GCL, and leads to inhibition of GCL activity. This interaction also leads to reduced cellular GSH levels and impaired cell viability in ARID1A-deficient cancer cells, which are particularly vulnerable to glutathione depletion, but not in ARID1A-positive cancer cells. Our studies uncover a novel potential ligandable site within GCLM that can be targeted to inhibit GSH synthesis in vulnerable cancer cell types.
Insights
Researchers identified EN25, a novel inhibitor targeting glutamate-cysteine ligase (GCL). This compound reduces glutathione (GSH) synthesis and impairs cancer cell viability, particularly in ARID1A-deficient tumors sensitive to oxidative stress.
Area of Science:
- Biochemistry
- Oncology
- Medicinal Chemistry
Background:
- Oxidative stress is crucial in cancer development.
- Cancer cells with inhibited antioxidant capacity are vulnerable.
- Glutathione (GSH) synthesis, regulated by glutamate-cysteine ligase (GCL), is a key antioxidant pathway.
Purpose of the Study:
- To identify and characterize novel inhibitors of GCL.
- To explore therapeutic strategies targeting GSH synthesis in cancer.
- To investigate the role of GCL inhibition in ARID1A-deficient cancers.
Main Methods:
- Development of a cysteine-reactive ligand, EN25.
- Targeting an allosteric cysteine (C114) on the GCLM subunit of GCL.
- Assessing GCL activity, cellular GSH levels, and cell viability in cancer cell lines.
Main Results:
- EN25 covalently binds to GCLM, inhibiting GCL activity.
- EN25 reduces intracellular GSH levels.
- EN25 selectively impairs viability in ARID1A-deficient cancer cells, not ARID1A-positive cells.
Conclusions:
- A novel allosteric site on GCLM can be targeted to inhibit GSH synthesis.
- EN25 demonstrates potential as a therapeutic agent for specific cancer types.
- Targeting GSH synthesis offers a promising strategy for cancers vulnerable to oxidative stress.
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