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Cytolytic activity of peptides derived from the Cry11Bb insecticidal toxin of B. thuringiensis subsp. medellin
Santiago Rendon-Marin1, Carolina Quintero-Gil1, Victor V Lemeshko2
1Escuela de Biociencias, Facultad de Ciencias, Universidad Nacional de Colombia Sede Medellín, Carrera 65 No. 59A - 110, Medellín, 050034, Colombia.
Abstract:
A few Bacillus thuringiensis Cry proteins, known as parasporins, have demonstrated cell proliferation inhibition of human cancer cells in vitro after protease activation. In this work, eight peptides derived from the Cry11Bb protoxin produced by B. thuringiensis subsp. medellin were selected and evaluated to investigate their membrane permeabilization and cytolytic activities, using red blood cells and cancer cell lines A549, MCF-7 and Caco-2, respectively. The most active peptides permeabilized red blood cells in a membrane potential-dependent manner. Half maximal inhibitory concentration in cancer cells was in the range 0.78-7.63 μM. At the same time, at peptides concentration of 25 μM, the hemolysis percentage varied in the range of 4.6-32.4%. The peptides BTM-P1 and BTM-P4 in D form had the lowest IC50 values on the MCF-7 cell line and they are considered as the most promising peptides among the evaluated. Fluorescence microscopy using AnnexinV-FLUOS staining indicates that the possible cause of MCF-7 cell death by peptide BTM-P1, is apoptosis. Real time PCR analysis showed an increased transcription of p53 in MCF-7 cells, thus confirming the probable pro-apoptotic effect of the peptide BTM-P1. In general, this study suggests that the cytolytic activity of the polycationic peptides derived from the Cry11Bb protoxin could be mediated by a pro-apoptotic mechanism that might include potential-dependent membrane permeabilization. Further studies might be accomplished to establish whether the peptides are cytolytic to other cancer cell lines and to solid tumors.
Insights
Eight peptides from Bacillus thuringiensis Cry11Bb protoxin showed cell-killing activity against human cancer cells. The most effective peptides induced apoptosis, a programmed cell death pathway, and permeabilized cell membranes, suggesting potential for cancer therapy development.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- Bacillus thuringiensis (Bt) Cry proteins, specifically parasporins, inhibit cancer cell proliferation.
- Protease activation is key for parasporin activity against cancer cells.
- Cry11Bb protoxin from B. thuringiensis subsp. medellin is a source of potential anti-cancer peptides.
Purpose of the Study:
- To evaluate eight peptides derived from Cry11Bb protoxin for membrane permeabilization and cytolytic activities.
- To investigate the mechanism of action, including apoptosis induction and membrane potential dependence.
- To identify promising peptides for potential cancer therapeutic applications.
Main Methods:
- Peptide selection from Cry11Bb protoxin.
- Assay of membrane permeabilization using red blood cells.
- Cytotoxicity assessment on A549, MCF-7, and Caco-2 cancer cell lines.
- Hemolysis assays.
- AnnexinV-FLUOS staining for apoptosis detection.
- Real-time PCR for p53 transcription analysis.
Main Results:
- Selected peptides demonstrated membrane permeabilization in a membrane potential-dependent manner.
- Half maximal inhibitory concentrations (IC50) in cancer cells ranged from 0.78–7.63 μM.
- Hemolysis percentages at 25 μM peptide concentration varied from 4.6–32.4%.
- Peptides BTM-P1 and BTM-P4 showed the lowest IC50 values against MCF-7 cells.
- BTM-P1 induced apoptosis in MCF-7 cells, evidenced by AnnexinV staining and increased p53 transcription.
Conclusions:
- Polycationic peptides from Cry11Bb protoxin exhibit cytolytic activity against cancer cells.
- The mechanism involves potential-dependent membrane permeabilization and induction of apoptosis.
- Peptides BTM-P1 and BTM-P4 are promising candidates for further investigation in cancer therapy.
- Further studies are warranted to explore efficacy against other cancer types and solid tumors.
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