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Antisense inhibition of Bax mRNA increases survival of terminally differentiated HL60 cells
R Manfredini1, M L Capobianco, F Trevisan
1Dipartimento di Scienze Biomediche, Sezione di Chimica Biologica, Università di Modena, Italy.
Abstract:
Cell sensitivity to programmed cell death is primarily modulated by members of the Bcl-2 family, as the balance of homodimer or heterodimer formation between proapoptotic and antiapoptotic members defines apoptosis susceptibility in the great majority of cellular contexts. It is, therefore, important to clarify if the Bax protein is limiting for activation of the genetic program of programmed cell death or can be complemented by different Bcl-2 family members, such as Bak or Bad. To gain some insight into the role of Bax in the molecular mechanisms of apoptosis of myeloid cells, we inhibited this gene in all-trans-retinoic acid (ATRA)-treated HL60 cells using the methodology of antisense oligodeoxynucleotides (AS-ODN). Our results indicate that Bax inhibition has no effect on the proliferation and differentiation capacity of HL60 cells. Instead, the survival rate of terminally differentiated Bax-inactivated HL60 (Bax(-) HL60) cells is almost three times higher in respect to control cultures, indicating that in mature granulocytes Bax is not efficiently complemented by others members of the Bcl-2 family proteins.
Insights
Bax protein is crucial for programmed cell death in mature granulocytes. Inhibiting Bax significantly increases cell survival, showing other Bcl-2 family members do not compensate for its absence.
Area of Science:
- Cell biology
- Molecular biology
- Cancer research
Background:
- Programmed cell death (apoptosis) is regulated by the Bcl-2 protein family.
- The balance between proapoptotic and antiapoptotic Bcl-2 members dictates cell death susceptibility.
- Bax protein's role in apoptosis, particularly in myeloid cells, requires further clarification.
Purpose of the Study:
- To investigate if Bax protein is essential for initiating programmed cell death.
- To determine if other Bcl-2 family members (e.g., Bak, Bad) can complement Bax deficiency.
- To elucidate the specific role of Bax in the apoptosis of all-trans-retinoic acid (ATRA)-treated HL60 myeloid cells.
Main Methods:
- Utilized antisense oligodeoxynucleotides (AS-ODN) to inhibit Bax gene expression in HL60 cells.
- Treated HL60 cells with all-trans-retinoic acid (ATRA) to induce differentiation.
- Assessed the proliferation, differentiation, and survival rates of Bax-inactivated HL60 cells.
Main Results:
- Bax inhibition did not affect the proliferation or differentiation of HL60 cells.
- Terminally differentiated Bax-inactivated HL60 cells exhibited a nearly threefold increase in survival compared to control cultures.
- These findings suggest Bax is not effectively complemented by other Bcl-2 family proteins in mature granulocytes.
Conclusions:
- Bax protein plays a critical, non-redundant role in mediating apoptosis in terminally differentiated myeloid cells.
- The absence of Bax significantly enhances cell survival, indicating its indispensability for initiating programmed cell death in this context.
- Other Bcl-2 family members cannot fully compensate for Bax function in mature granulocytes, highlighting Bax's unique contribution to apoptosis regulation.