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Daxx enhances Fas-mediated apoptosis in a murine pro-B cell line, BAF3
Ryuta Muromoto1, Tetsuya Yamamoto, Taro Yumioka
1Department of Immunology, Graduate School of Pharmaceutical Sciences, Hokkaido University, Kita-Ku Kita 12 Nishi 6, Sapporo 060-0812, Japan.
Abstract:
Daxx has been shown to play an essential in type I interferon (IFN-alpha/beta)-mediated suppression of B cell development and apoptosis. Recently, we demonstrated that Tyk2 is directly involved in IFN signaling for the induction and nuclear translocation of Daxx, which may result in growth arrest and/or apoptosis of B lymphocyte progenitors. To clarify the mechanism of Daxx-mediated apoptosis signaling in B lymphocyte progenitors, here we introduced an efficient suicide switch in a murine pro-B cell line, BAF3, by expressing FK506-binding protein-fused Fas intracellular domain (FKBP-Fas) and Daxx. It allows us to monitor Fas/Daxx-mediated signal by induction of Fas dimerization with the dimerizer drug AP20187. AP20187-mediated Fas dimerization induced not only apoptosis but also Jun N-terminal kinase (JNK) activation. However, AP20187 had no effect on cells expressing either Fas or Daxx only. Furthermore, expression of a JNK inhibitor, the JNK-binding domain of JIP-1, resulted in resistance to AP20187-mediated apoptosis in cells expressing FKBP-Fas and Daxx. These results imply that our novel suicide switch system may provide a powerful tool to delineate or identify the signaling molecules for Daxx-mediated apoptotic machinery in B lymphocyte progenitors through JNK activation.
Insights
This study introduces a novel suicide switch system to investigate Daxx-mediated apoptosis in B lymphocyte progenitors. The system reveals Jun N-terminal kinase (JNK) activation is crucial for Daxx-induced apoptosis.
Area of Science:
- Immunology
- Cell Biology
- Molecular Biology
Background:
- Daxx protein is essential for type I interferon (IFN-alpha/beta)-mediated suppression of B cell development and apoptosis.
- Tyk2 kinase is involved in IFN signaling, regulating Daxx induction and nuclear translocation, potentially causing B lymphocyte progenitor apoptosis.
- The precise mechanism of Daxx-mediated apoptosis in these cells requires further elucidation.
Purpose of the Study:
- To establish and utilize a novel suicide switch system for investigating Daxx-mediated apoptosis signaling in B lymphocyte progenitors.
- To elucidate the role of Jun N-terminal kinase (JNK) activation in the Daxx-induced apoptotic pathway.
Main Methods:
- Engineered a murine pro-B cell line (BAF3) with a suicide switch system expressing FKBP-Fas and Daxx.
- Induced Fas dimerization using AP20187 to trigger apoptosis and signaling.
- Utilized a JNK inhibitor (JIP-1) to assess JNK's role in the apoptotic pathway.
Main Results:
- AP20187-induced Fas dimerization triggered apoptosis and JNK activation in cells co-expressing FKBP-Fas and Daxx.
- AP20187 had no effect on cells expressing only Fas or Daxx.
- Inhibition of JNK signaling conferred resistance to AP20187-mediated apoptosis.
Conclusions:
- The developed suicide switch system is a powerful tool for studying Daxx-mediated apoptosis in B lymphocyte progenitors.
- JNK activation is a critical component of the Daxx-mediated apoptotic machinery in these cells.