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Positive selection of apoptosis-resistant cells correlates with activation of dominant-negative STAT5
C Bovolenta1, L Testolin, L Benussi
1Institutes of Biological Chemistry, University of Verona, Verona 37134, Milano, Italy.
Abstract:
The STAT5 activation has important roles in cell differentiation, cell cycle control, and development. However, the potential implications of STAT5 in the control of apoptosis remain unexplored. To evaluate any possible link between the erythropoietin receptor (EpoR) JAK2/STAT5 transduction pathway and apoptosis, we have investigated apoptosis-resistant cells (ApoR) that arose from positive selection of the erythroid-committed Ba/F3EpoR cells triggered to apoptosis by ectopic expression of the HOX-B8 homeotic gene. We show that JAK2 is normally activated by Epo in both Ba/F3EpoR and ApoR cells. In contrast, both STAT5a and STAT5b isoforms are uniquely activated in a C-truncated form (86 kDa) only in ApoR cells. Analysis of ApoR and Ba/F3EpoR subclones confirmed that the switch to the truncated STAT5 isoform coincides with apoptosis survival and that ApoR do not derive from preexisting cells with a shortened STAT5. In addition, ApoR cells die in the absence of Epo. This indicates that resistance to apoptosis is not because of a general defect in the apoptotic pathway of ApoR cells. Furthermore, we show that the 86-kDa STAT5 protein presents a dominant-negative (DN) character. We hypothesize that the switch to a DN STAT5 may be part of a mechanism that allows ApoR cells to be selectively advantaged during apoptosis. In conclusion, we provide evidence for a functional correlation between a naturally occurring DN STAT5 and a biological response.
Insights
A novel dominant-negative STAT5 isoform promotes apoptosis resistance in erythroid cells. This discovery links a truncated STAT5 protein to cell survival, offering insights into apoptosis regulation.
Area of Science:
- Cell Biology
- Molecular Biology
- Signal Transduction
Background:
- Signal transducer and activator of transcription 5 (STAT5) plays key roles in cell differentiation and development.
- The involvement of STAT5 in apoptosis regulation remains largely unexplored.
- The erythropoietin receptor (EpoR) pathway is crucial for erythroid cell survival.
Purpose of the Study:
- To investigate the potential link between the EpoR JAK2/STAT5 pathway and apoptosis.
- To characterize the role of STAT5 isoforms in apoptosis-resistant cells.
Main Methods:
- Generated apoptosis-resistant (ApoR) cells from Ba/F3EpoR cells via HOX-B8 expression.
- Analyzed STAT5 activation and isoform expression in Ba/F3EpoR and ApoR cells.
- Assessed apoptosis sensitivity and STAT5 protein characteristics.
Main Results:
- JAK2 activation by Epo was observed in both cell types.
- A unique C-truncated 86 kDa STAT5 isoform was activated exclusively in ApoR cells.
- The switch to truncated STAT5 correlated with apoptosis resistance and dominant-negative activity.
Conclusions:
- A naturally occurring dominant-negative STAT5 isoform is functionally correlated with apoptosis resistance.
- This truncated STAT5 may represent a survival advantage mechanism in erythroid cells.
- Provides evidence for STAT5's role in modulating apoptosis.