Related Experiment Video
Updated: Dec 23, 2025
Proliferation and Differentiation of Murine Myeloid Precursor 32D/G-CSF-R Cells
Published on: February 21, 2018
Cullin 3 Is Crucial for Pro-B Cell Proliferation, Interacts with CD22, and Controls CD22 Internalization on B Cells
Sarah J Meyer1, Alexander Böser2, Marina A Korn1
1Division of Genetics, Department of Biology, University of Erlangen, 91058 Erlangen, Germany.
Insights
The E3 ubiquitin ligase cullin 3 regulates CD22 surface expression and internalization in B cells. Cullin 3 deficiency impairs B cell development and proliferation, highlighting its critical role in immune homeostasis.
Area of Science:
- Immunology
- Molecular Biology
- Cell Biology
Background:
- B lymphocytes are crucial for adaptive immunity, requiring precise regulation of their signaling pathways to prevent immune dysregulation.
- CD22, an inhibitory coreceptor of the B cell receptor (BCR), plays a key role in dampening B cell activation by reducing calcium mobilization upon BCR stimulation.
- Understanding the complete CD22 interactome is essential for elucidating its regulatory functions in B cells.
Purpose of the Study:
- To identify novel proteins interacting with CD22 using quantitative affinity purification-mass spectrometry.
- To investigate the functional role of newly identified CD22-associated proteins in B cell signaling and regulation.
- To elucidate the specific functions of the E3 ubiquitin ligase cullin 3 in B lymphocyte biology.
Main Methods:
- Quantitative affinity purification-mass spectrometry was employed to map the CD22 interactome in the DT40 B cell line.
- Functional assays were conducted to assess the impact of cullin 3 on CD22 surface expression and internalization.
- B cell-specific cullin 3-deficient mice were generated and analyzed for B cell development, proliferation, and phenotype.
Main Results:
- The study identified several new proteins associated with CD22, including the E3 ubiquitin ligase cullin 3.
- Cullin 3 was found to regulate CD22 surface expression and mediate its clathrin-dependent internalization following BCR stimulation.
- B cell-specific cullin 3 deficiency led to reduced B cell populations in bone marrow and periphery, impaired pro-B cell proliferation, and altered mature B cell phenotypes (increased CD22, preactivated, apoptotic).
Conclusions:
- Cullin 3 is a novel and important regulator of CD22 surface expression and internalization in B lymphocytes.
- Cullin 3 plays a critical role in B cell development, proliferation, and maintenance of immune homeostasis.
- These findings reveal new molecular mechanisms governing B cell signaling regulation and highlight cullin 3 as a key player in B lymphocyte function.
Abstract:
B lymphocytes are important players of the adaptive immune system. However, not just activation of B cells but also regulation of B cell signaling is important to prevent hyperactivity and dysregulation of the immune response. Different mechanisms and proteins contribute to this balance. One of these is CD22, a member of the Siglec family. It is an inhibitory coreceptor of the BCR and inhibits B cell activation. Upon BCR stimulation, CD22-dependent inhibition of BCR signaling results in a decreased calcium mobilization. Although some CD22 binding partners have already been identified, the knowledge about the CD22 interactome is still incomplete. In this study, quantitative affinity purification-mass spectrometry enabled the delineation of the CD22 interactome in the B cell line DT40. These data will clarify molecular mechanisms and CD22 signaling events after BCR activation and revealed several new CD22-associated proteins. One new identified interaction partner is the E3 ubiquitin ligase cullin 3, which was revealed to regulate CD22 surface expression and clathrin-dependent CD22 internalization after BCR stimulation. Furthermore cullin 3 was identified to be important for B lymphocytes in general. B cell-specific cullin 3-deficient mice show reduced developing B cells in the bone marrow and a severe pro-B cell proliferation defect. Mature B cells in the periphery are also reduced and characterized by increased CD22 expression and additionally by preactivated and apoptotic phenotypes. The findings reveal novel functions of cullin 3 in B lymphocytes, namely regulating CD22 surface expression and internalization after B cell activation, as well as promoting proliferation of pro-B cells.
Related Concept Videos
01:22T Cell Activation and Clonal Selection
Naive T cells that have not yet encountered an antigen express two primary CD...
01:24B Cell Activation and Differentiation
When naive B cells encounter a specific antigen that can bind to the B cell receptor (BCR) on their surface, they undergo sensitization to respond to the antigen's presence. Sensitization begins with...
01:15Receptor Downregulation in MVBs
The EGFR can initiate signaling pathways that lead to cell proliferation, migration, and differentiation. Overexpression of EGFR stimulates cells to proliferate. Excessive EGFR...
01:31Immunoglobulin-like Cell Adhesion Molecules
Ig-CAMs exhibit either homophilic binding (to other Ig-CAMs) or heterophilic binding (to other ligands such as integrins). While most Ig-CAMs...
01:15Differentiation of Common Myeloid Progenitor Cells
01:24T Cell Types and Functions
Th1 cells stimulate dendritic cells to express necessary co-stimulatory molecules on their surfaces for...