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DBC1 is a suppressor of B cell activation by negatively regulating alternative NF-κB transcriptional activity
Sinyi Kong1, Muthusamy Thiruppathi2, Quan Qiu1
1Department of Pathology, Northwestern University Feinberg School of Medicine, Chicago, IL 60611;
Insights
Deletion of DBC1 gene enhances B cell activation via CD40 and BAFF signaling, boosting antibody production. This discovery reveals DBC1 as a key regulator of B cell responses and autoimmune disease susceptibility.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- CD40 and BAFFR signaling are crucial for B cell proliferation and immunoglobulin (Ig) production.
- Dysregulated B cell activation contributes to autoimmune diseases.
Purpose of the Study:
- To investigate the role of DBC1 (Deleted in Breast Cancer 1) in regulating B cell activation.
- To elucidate the molecular mechanisms by which DBC1 influences CD40 and BAFFR signaling pathways.
Main Methods:
- Utilized Dbc1 gene-deficient (Dbc1(-/-)) mice and wild-type littermates.
- Performed in vitro stimulation assays (CD40, BAFF, BCR, LPS).
- Conducted microarray analysis and chromatin immunoprecipitation (ChIP) assays.
- Immunized mice and assessed B cell populations and antigen-specific Ig levels.
- Evaluated susceptibility to experimental autoimmune myasthenia gravis.
Main Results:
- Dbc1(-/-) B cells exhibited elevated proliferation and Ig (IgG1, IgA) production upon CD40 and BAFF stimulation.
- DBC1 was found to suppress the transcriptional activity of alternative NF-κB members (RelB and p52) downstream of CD40 signaling.
- Dbc1(-/-) mice showed increased germinal center B cells, plasma cells, and antigen-specific Ig levels post-immunization.
- Loss of DBC1 conferred higher susceptibility to experimental autoimmune myasthenia gravis.
Conclusions:
- DBC1 acts as a cell-intrinsic inhibitor of CD40/BAFF-mediated B cell activation.
- DBC1 regulates B cell function by suppressing the alternative NF-κB pathway.
- DBC1 is a novel regulator of B cell responses with implications for autoimmune pathogenesis.
Abstract:
CD40 and BAFFR signaling play important roles in B cell proliferation and Ig production. In this study, we found that B cells from mice with deletion of Dbc1 gene (Dbc1(-/-)) show elevated proliferation, and IgG1 and IgA production upon in vitro CD40 and BAFF, but not BCR and LPS stimulation, indicating that DBC1 inhibits CD40/BAFF-mediated B cell activation in a cell-intrinsic manner. Microarray analysis and chromatin immunoprecipitation experiments reveal that DBC1 inhibits B cell function by selectively suppressing the transcriptional activity of alternative NF-κB members RelB and p52 upon CD40 stimulation. As a result, when immunized with nitrophenylated-keyhole limpet hemocyanin, Dbc1(-/-) mice produce significantly increased levels of germinal center B cells, plasma cells, and Ag-specific Ig. Finally, loss of DBC1 in mice leads to higher susceptibility to experimental autoimmune myasthenia gravis. Our study identifies DBC1 as a novel regulator of B cell activation by suppressing the alternative NF-κB pathway.
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