Related Experiment Video
Updated: May 18, 2026
The Lactate Dehydrogenase Sequestration Assay — A Simple and Reliable Method to Determine Bulk Autophagic Sequestration Activity in Mammalian Cells
Published on: July 27, 2018
Lithocholic acid is an endogenous inhibitor of MDM4 and MDM2
Simon M Vogel1, Matthias R Bauer, Andreas C Joerger
1Laboratory for Molecular Design and Pharmaceutical Biophysics, Department of Pharmaceutical and Medicinal Chemistry, Institute of Pharmacy, Eberhard Karls University Tuebingen, Auf der Morgenstelle 8, 72076 Tuebingen, Germany.
Abstract:
The proteins MDM2 and MDM4 are key negative regulators of the tumor suppressor protein p53, which are frequently upregulated in cancer cells. They inhibit the transactivation activity of p53 by binding separately or in concert to its transactivation domain. MDM2 is also a ubiquitin ligase that leads to the degradation of p53. Accordingly, MDM2 and MDM4 are important targets for drugs to inhibit their binding to p53. We found from in silico screening and confirmed by experiment that lithocholic acid (LCA) binds to the p53 binding sites of both MDM2 and MDM4 with a fivefold preference for MDM4. LCA is an endogenous steroidal bile acid, variously reported to have both carcinogenic and apoptotic activities. The comparison of LCA effects on apoptosis in HCT116 p53(+/+) vs. p53(-/-) cells shows a predominantly p53-mediated induction of caspase-3/7. The dissociation constants are in the μM region, but only modest inhibition of binding of MDM2 and MDM4 is required to negate their upregulation because they have to compete with transcriptional coactivator p300 for binding to p53. Binding was weakened by structural changes in LCA, and so it may be a natural ligand of MDM2 and MDM4, raising the possibility that MDM proteins may be sensors for specific steroids.
Insights
Lithocholic acid (LCA) inhibits MDM2 and MDM4, key regulators of the tumor suppressor p53, potentially impacting cancer therapy. This bile acid shows a preference for MDM4, suggesting a role in p53 regulation.
Area of Science:
- Oncology
- Molecular Biology
- Biochemistry
Background:
- MDM2 and MDM4 are crucial negative regulators of the tumor suppressor protein p53.
- These proteins are frequently upregulated in cancer, inhibiting p53's activity and promoting tumor growth.
- MDM2 also functions as a ubiquitin ligase, targeting p53 for degradation.
Purpose of the Study:
- To identify novel inhibitors of MDM2 and MDM4 interactions with p53.
- To investigate the potential of lithocholic acid (LCA) as a therapeutic agent targeting these interactions.
Main Methods:
- In silico screening to identify potential binding compounds.
- Experimental validation of LCA binding to MDM2 and MDM4.
- Assays to measure LCA's effect on p53-mediated apoptosis in cancer cells.
- Determination of dissociation constants for LCA binding.
Main Results:
- Lithocholic acid (LCA) was identified as a compound that binds to the p53 binding sites of both MDM2 and MDM4, with a fivefold preference for MDM4.
- LCA induces apoptosis in a p53-dependent manner.
- The binding affinity (dissociation constants) is in the micromolar range.
- Structural modifications of LCA weakened its binding, suggesting it may be a natural ligand.
Conclusions:
- LCA is a potential therapeutic lead for targeting MDM2/MDM4 in cancer.
- The findings suggest that MDM proteins might act as sensors for specific steroids.
- Further research into LCA and its derivatives could yield new cancer treatments.
Related Concept Videos
02:23Abnormal Proliferation
02:34Inhibition of Cdk Activity