Related Experiment Videos
Microfilament-disrupting agents prevent the formation of apoptotic bodies in tumor cells undergoing apoptosis
T G Cotter1, S V Lennon, J M Glynn
1Division of Cellular Immunology, La Jolla Institute for Allergy and Immunology, California 92037.
Abstract:
Apoptosis is a form of cell death in which the cell "participates," such that metabolic energy and often protein synthesis are required for the death to occur. Once begun, the process of apoptosis proceeds in an ordered fashion. In the earliest phase DNA fragmentation occurs, accompanied by cell shrinkage and dilation of the endoplasmic reticulum. This is followed by cell fragmentation with the formation of sealed membrane vesicles, termed apoptotic bodies. In the present study we have demonstrated that the fungal metabolite cytochalasin B inhibits cell fragmentation and the formation of apoptotic bodies, probably by its ability to interfere with actin polymerization. This effect was seen when HL-60 cells were pretreated with cytochalasin B and then exposed to one of a number of apoptosis-inducing agents, including UV irradiation, camptothecin, aphidocholin, or PMA plus ionomycin. The observed effect was not peculiar to HL-60 cells, inasmuch as it was also seen for both Molt-4 and U-937 cell lines. Cytochalasin B had no effect on DNA fragmentation occurring in the earliest stage of apoptosis, and it appeared to have no inhibitory effects on nuclear fragmentation. Staurosporin had an effect similar to that seen with cytochalasin B, probably due to its ability to inhibit protein kinase C, which is a known potentiator of microfilament assembly. These data demonstrate that microfilament assembly is necessary for the formation of apoptotic bodies in the later stages of the apoptotic process.
Insights
Cytochalasin B inhibits later stages of apoptosis, specifically cell fragmentation and apoptotic body formation, by interfering with actin polymerization. This highlights the necessity of microfilament assembly for these late-stage apoptotic events.
Area of Science:
- Cell Biology
- Biochemistry
Background:
- Apoptosis is an ordered process of programmed cell death.
- Key early events include DNA fragmentation and cell shrinkage.
- Later stages involve cell fragmentation into apoptotic bodies.
Purpose of the Study:
- To investigate the role of microfilament assembly in apoptosis.
- To determine if cytochalasin B affects specific stages of apoptosis.
Main Methods:
- Treatment of HL-60, Molt-4, and U-937 cell lines with cytochalasin B.
- Induction of apoptosis using agents like UV irradiation, camptothecin, and staurosporin.
- Observation of DNA fragmentation, nuclear fragmentation, and apoptotic body formation.
Main Results:
- Cytochalasin B inhibited cell fragmentation and apoptotic body formation.
- This inhibition occurred without affecting early DNA or nuclear fragmentation.
- Staurosporin showed similar effects, suggesting involvement of protein kinase C and microfilaments.
Conclusions:
- Microfilament assembly is essential for the formation of apoptotic bodies in late-stage apoptosis.
- Cytochalasin B's interference with actin polymerization disrupts this process.
- These findings elucidate the molecular mechanisms underlying apoptotic morphology.