Related Experiment Videos
Dominant suppression of lymphocyte apoptosis by hepatoma cells
R B Evans-Storms1, J A Cidlowski
1Laboratory of Cellular and Molecular Pharmacology, National Institute of Environmental Health Sciences, N.I.H., Research Triangle Park, North Carolina 27709, USA.
Abstract:
Suppression of apoptosis appears to contribute to the development of various diseases, including autoimmune disorders and cancer. Numerous genes that encode activators and suppressors of apoptosis have been identified; however, such genes have not been shown to be expressed in all cell types. Furthermore, the sensitivity of different cell types to induction of apoptosis varies widely. We have employed a genetic approach using somatic cell hybridization to determine if apoptosis is a dominant or a recessive process in cells. These studies have utilized cell fusion partners with differing sensitivity to induction of apoptosis. The apoptosis-sensitive cells chosen were BW5147 murine thymoma cells. These cells readily undergo apoptosis in response to glucocorticoids and calcium ionophore. The resistant fusion partners were HTC rat hepatoma cells, which possess an intact glucocorticoid signal transduction pathway but are resistant to induction of apoptosis by either agent. Neither cell type expresses detectable Bcl-2 protein. Heterokaryons were identified by their retention of fluorescent cytosolic dyes and by nuclear morphology and cell size. The three types of heterokaryons observed were intratypic HTC/HTC and BW5147/BW5147 heterokaryons and intertypic BW5147/HTC heterokaryons. Glucocorticoid receptor was shown by immunohistochemistry to undergo hormone-dependent translocation to all nuclei in intertypic heterokaryons. BW5147/BW5147 heterokaryons die after treatment with glucocorticoid and calcium ionophore, whereas both HTC/ HTC and BW5147/HTC hybrids survive. The presence of multiple BW5147 cells fused to a single HTC cell did not affect this outcome. This demonstrates that HTC cells are able to dominantly suppress apoptosis in all BW5147/HTC heterokaryons. Thus, HTC cells contain activities that can suppress apoptosis in lymphocytes.
Insights
Apoptosis suppression is dominant in cells. HTC rat hepatoma cells can dominantly suppress apoptosis induction in sensitive BW5147 murine thymoma cells, indicating a dominant genetic control of apoptosis.
Area of Science:
- Cell biology
- Genetics
- Immunology
Background:
- Apoptosis (programmed cell death) suppression is implicated in diseases like cancer and autoimmune disorders.
- While apoptosis regulators are known, their expression and cell-type sensitivity vary.
- The genetic basis of apoptosis (dominant or recessive) remains unclear across different cell types.
Purpose of the Study:
- To determine if apoptosis is a dominant or recessive genetic process.
- To investigate the genetic mechanisms underlying differential apoptosis sensitivity in cells.
- To identify cellular factors that can suppress apoptosis.
Main Methods:
- Somatic cell hybridization was used to create heterokaryons (fused cells).
- Apoptosis sensitivity was tested using BW5147 (sensitive) and HTC (resistant) cell lines.
- Apoptosis induction was triggered by glucocorticoids and calcium ionophore.
Main Results:
- BW5147/BW5147 and HTC/HTC heterokaryons showed expected apoptosis sensitivity or resistance.
- BW5147/HTC intertypic heterokaryons survived apoptosis-inducing treatments.
- HTC cells dominantly suppressed apoptosis in fused BW5147 cells, irrespective of fusion ratio.
Conclusions:
- Apoptosis suppression is a dominant genetic trait.
- HTC rat hepatoma cells possess dominant suppressor activities against apoptosis.
- These findings suggest potential therapeutic targets for controlling apoptosis in lymphocytes and related diseases.