Gα_i Signaling Promotes Marginal Zone B Cell Development by Enabling Transitional B Cell ADAM10 Expression

Area of Science:

• Immunology
• Cell Biology
• Molecular Biology

Background:

• The differentiation of follicular (FO) and marginal zone (MZ) B cells is critical for adaptive immunity.
• This fate decision is regulated by B cell receptor (BCR), BAFF, and Notch2 signaling pathways.
• The role of Gαi signaling in this process remains largely unexplored.

Purpose of the Study:

• To investigate the impact of Gαi signaling on MZ B cell development.
• To elucidate the molecular mechanisms by which Gαi signaling influences B cell fate decisions.

Main Methods:

• Utilized stromal cells (OP9-Delta-like 1) expressing Notch ligands for co-culture experiments.
• Assessed B cell development in progenitor B cells lacking or with inhibited Gαi proteins.
• Analyzed ADAM10 expression, processing, and Notch2 target gene expression via immunoblotting and gene expression analysis.
• Investigated the effect of CXCL12 stimulation and Gαi nucleotide exchange inhibition on ADAM10 levels.

Main Results:

• Gαi deficiency or inhibition impaired normal MZ B cell development.
• Transitional B cells lacking Gαi showed reduced ADAM10 membrane expression and Notch2 target gene expression.
• Gαi signaling promotes ADAM10 maturation and membrane expression, which is upregulated by CXCL12.
• Inhibition of Gαi nucleotide exchange blocked ADAM10 upregulation and impaired its response to antigen receptor crosslinking.

Conclusions:

• Gαi signaling is essential for ADAM10 maturation and activity in transitional B cells.
• This signaling pathway supports Notch2 signaling, thereby promoting marginal zone B cell development.
• Gαi proteins play a key role in regulating B cell fate decisions in the spleen.