Related Experiment Video
Updated: Mar 6, 2026
Detection of Aggregation-Prone Behavior in Mutant P53 V157F Breast Cancer Cells Using Multipoint Thioflavin T Fluorescence
Published on: December 30, 2025
Multisite aggregation of p53 and implications for drug rescue
1MRC Laboratory of Molecular Biology, PNAC Division, Cambridge CB2 0QH, United Kingdom.
Abstract:
Protein aggregation is involved in many diseases. Often, a unique aggregation-prone sequence polymerizes to form regular fibrils. Many oncogenic mutants of the tumor suppressor p53 rapidly aggregate but form amorphous fibrils. A peptide surrounding Ile254 is proposed to be the aggregation-driving sequence in cells. We identified several different aggregating sites from limited proteolysis of harvested aggregates and effects of mutations on kinetics and products of aggregation. We present a model whereby the amorphous nature of the aggregates results from multisite branching of polymerization after slow unfolding of the protein, which may be a common feature of aggregation of large proteins. Greatly lowering the aggregation propensity of any one single site, including the site of Ile254, by mutation did not inhibit aggregation in vitro because aggregation could still occur via the other sites. Inhibition of an individual site is, accordingly, potentially unable to prevent aggregation in vivo. However, cancer cells are specifically killed by peptides designed to inhibit the Ile254 sequence and further aggregation-driving sequences that we have found. Consistent with our proposed mechanism of aggregation, we found that such peptides did not inhibit aggregation of mutant p53 in vitro. The cytotoxicity was not eliminated by knockdown of p53 in 2D cancer cell cultures. The peptides caused rapid cell death, much faster than usually expected for p53-mediated transcription-dependent apoptosis. There may also be non-p53 targets for those peptides in cancer cells, such as p63, or the peptides may alter other interactions of partly denatured p53 with receptors.
Insights
Cancer-associated protein p53 mutations cause amorphous aggregates. Inhibiting specific aggregation sites kills cancer cells, suggesting novel therapeutic strategies beyond targeting p53 alone.
Area of Science:
- Biochemistry
- Molecular Biology
- Cancer Research
Background:
- Protein aggregation is implicated in various diseases, often forming regular fibrils from specific sequences.
- Oncogenic mutants of tumor suppressor p53 aggregate into amorphous fibrils, with a peptide near Ile254 proposed as a key aggregation driver.
- Understanding the mechanisms of amorphous protein aggregation is crucial for disease intervention.
Purpose of the Study:
- To investigate the aggregation mechanisms of mutant p53 and identify aggregation-driving sequences.
- To evaluate the efficacy of inhibiting specific aggregation sites in vitro and in vivo.
- To explore the therapeutic potential of peptides targeting aggregation-driving sequences in cancer cells.
Main Methods:
- Limited proteolysis of harvested aggregates to identify aggregation sites.
- Site-directed mutagenesis to assess the impact of mutations on aggregation kinetics and products.
- In vitro aggregation assays and cell-based cytotoxicity studies using engineered peptides.
Main Results:
- Multiple aggregation-prone sites were identified, and amorphous aggregate formation was linked to multisite branching after slow protein unfolding.
- Mutating individual aggregation sites, including the Ile254-surrounding peptide, did not prevent in vitro aggregation due to compensatory aggregation via other sites.
- Peptides targeting identified aggregation sequences, including Ile254, effectively killed cancer cells, independent of p53 knockdown, indicating potential non-p53 targets or altered protein interactions.
Conclusions:
- Amorphous aggregation of large proteins like mutant p53 may result from multisite branching after unfolding.
- Inhibiting single aggregation sites may be insufficient to prevent aggregation in vivo.
- Targeted peptides show promise for cancer therapy by inducing rapid cell death through mechanisms potentially independent of p53's transcriptional activity.
Related Concept Videos
02:23Abnormal Proliferation
02:56Treatment Resistant Cancers
01:19Interactions Between Signaling Pathways
Convergence and divergence, and cross-talk between signaling pathways
Two distinct signaling pathways can converge on a single functional unit, which may either be a single protein or a complex of proteins. The response is either functionally distinct or synergistic between the two pathways but different from the response...