FcR-Like 2 Inhibition of B Cell Receptor-Mediated Activation of B Cells

B cell receptor (BCR)-mediated antigen processing is a mechanism that allows class II–restricted presentation of specific antigen by B cells at relatively low antigen concentrations. Although BCR-mediated antigen processing and class II peptide loading may occur within one or more endocytic compartments, the functions of these compartments and their relationships to endosomes and lysosomes remain uncertain. In murine B cells, at least one population of class II– containing endocytic vesicles (i.e., CIIV) has been identified and demonstrated to be distinct both physically and functionally from endosomes and lysosomes. We now demonstrate the delivery of BCR-internalized antigen to CIIV within the time frame during which BCR-mediated antigen processing and formation of peptide–class II complexes occurs. Only a fraction of the BCR-internalized antigen was delivered to CIIV, with the majority of internalized antigen being delivered to lysosomes that are largely class II negative. The extensive colocalization of BCR-internalized antigen and newly synthesized class II molecules in CIIV suggests that CIIV may represent a specialized subcellular compartment for BCR-mediated antigen processing. Additionally, we have identified a putative CIIV-marker protein, immunologically related to the Igα subunit of the BCR, which further illustrates the unique nature of these endocytic vesicles.

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Targeted inhibition of eIF4A suppresses B-cell receptor-induced translation and expression of MYC and MCL1 in chronic lymphocytic leukemia cells

Cellular and Molecular Life Sciences ◽

10.1007/s00018-021-03910-x ◽

2021 ◽

Author(s):

Sarah Wilmore ◽

Karly-Rai Rogers-Broadway ◽

Joe Taylor ◽

Elizabeth Lemm ◽

Rachel Fell ◽

...

Keyword(s):

B Cells ◽

Chronic Lymphocytic Leukemia ◽

B Cell ◽

Mrna Translation ◽

Cell Receptor ◽

Memory B Cells ◽

B Cell Receptor ◽

Lymphocytic Leukemia ◽

Mrna Levels ◽

Mrna Stabilization

AbstractSignaling via the B-cell receptor (BCR) is a key driver and therapeutic target in chronic lymphocytic leukemia (CLL). BCR stimulation of CLL cells induces expression of eIF4A, an initiation factor important for translation of multiple oncoproteins, and reduces expression of PDCD4, a natural inhibitor of eIF4A, suggesting that eIF4A may be a critical nexus controlling protein expression downstream of the BCR in these cells. We, therefore, investigated the effect of eIF4A inhibitors (eIF4Ai) on BCR-induced responses. We demonstrated that eIF4Ai (silvestrol and rocaglamide A) reduced anti-IgM-induced global mRNA translation in CLL cells and also inhibited accumulation of MYC and MCL1, key drivers of proliferation and survival, respectively, without effects on upstream signaling responses (ERK1/2 and AKT phosphorylation). Analysis of normal naïve and non-switched memory B cells, likely counterparts of the two main subsets of CLL, demonstrated that basal RNA translation was higher in memory B cells, but was similarly increased and susceptible to eIF4Ai-mediated inhibition in both. We probed the fate of MYC mRNA in eIF4Ai-treated CLL cells and found that eIF4Ai caused a profound accumulation of MYC mRNA in anti-IgM treated cells. This was mediated by MYC mRNA stabilization and was not observed for MCL1 mRNA. Following drug wash-out, MYC mRNA levels declined but without substantial MYC protein accumulation, indicating that stabilized MYC mRNA remained blocked from translation. In conclusion, BCR-induced regulation of eIF4A may be a critical signal-dependent nexus for therapeutic attack in CLL and other B-cell malignancies, especially those dependent on MYC and/or MCL1.

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Expression of TASK‐2 and its upregulation by B cell receptor stimulation in WEHI‐231 mouse immature B cells

The FASEB Journal ◽

10.1096/fasebj.25.1_supplement.lb510 ◽

2011 ◽

Vol 25 (S1) ◽

Author(s):

Dong Hoon Shin

Keyword(s):

B Cells ◽

B Cell ◽

Cell Receptor ◽

B Cell Receptor ◽

Receptor Stimulation ◽

Wehi 231 ◽

Immature B Cells

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Characterization of B-cell Receptor Heavy Chain Complementarity-determining Region 3 Repertoire Based on the Differences of Symbiotic Microorganisms in the Gut of Mice

10.21203/rs.3.rs-203289/v1 ◽

2021 ◽

Author(s):

Jun Li ◽

Yurong Pan ◽

Qingqing Ma ◽

Long Ma ◽

Bin Shi ◽

...

Keyword(s):

Small Intestine ◽

B Cells ◽

B Cell ◽

Heavy Chain ◽

Intestinal Microflora ◽

Cell Receptor ◽

Memory B Cells ◽

B Cell Receptor ◽

Positive Effects ◽

Significant Difference

Abstract Background Colonization of gut microorganism is related to maturation of B cells in peripheral immune organs. This study aims to investigate the effect of intestinal microflora in Germ-free (GF), Specific Pathogen-free (SPF) and Clean (CL) BALB/C mice to small intestine total B-cell and memory B-cell receptor (BCR) complementary-determining region 3 (CDR3) repertoire. Results The composition and characteristics of intestinal microflora were analyzed by 16S rDNA sequencing. Genomic DNA extracted from small intestine tissue and memory B-cells of GF, SPF and CL mice were conducted via high-throughput DNA sequencing methods. As expected, significant differences of gut microflora diversity were observed in the three mice groups. CL group showed the most diversity, followed by SPF group, and GF group had the lowest diversity. Moreover, anormogenesis of intestinal lymphoid tissue were observed in GF mice. Diversity of the BCR heavy chain CDR3 repertoire in memory B cells were significant difference among three groups, but not in total B cells. The nucleotide polymorphism, usage frequency of gene segments (V, D, J, V–J gene segments) and amino acid of total B cells and memory B cells CDR3 were comparable among three mice groups, and there was significant difference between CL and GF mice groups. Conclusions The results of this study advocate that the colonization of intestinal microorganisms affect the diversity of B cells CDR3 repertoire. Elucidating mechanism of microbiome participated in the function of intestinal mucosal immune system may have positive effects on human health, and it requires further investigation.

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Faculty Opinions recommendation of B Cell Receptor and CD40 Signaling Are Rewired for Synergistic Induction of the c-Myc Transcription Factor in Germinal Center B Cells.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.732604893.793573078 ◽

2020 ◽

Author(s):

Elizabeth Mellins ◽

Debopam Ghosh

Keyword(s):

Transcription Factor ◽

B Cells ◽

B Cell ◽

Germinal Center ◽

Cell Receptor ◽

B Cell Receptor ◽

Synergistic Induction ◽

Germinal Center B Cells

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Signatures of B Cell Receptor Repertoire Following Pneumocystis Infection

Frontiers in Microbiology ◽

10.3389/fmicb.2021.636250 ◽

2021 ◽

Vol 12 ◽

Author(s):

Han Sun ◽

Hu-Qin Yang ◽

Kan Zhai ◽

Zhao-Hui Tong

Keyword(s):

B Cells ◽

B Cell ◽

Single Cell ◽

Plasma Cells ◽

Somatic Hypermutation ◽

Cell Receptor ◽

B Cell Receptor ◽

Receptor Repertoire ◽

Elevated Expression ◽

Pneumocystis Infection

B cells play vital roles in host defense against Pneumocystis infection. However, the features of the B cell receptor (BCR) repertoire in disease progression remain unclear. Here, we integrated single-cell RNA sequencing and single-cell BCR sequencing of immune cells from mouse lungs in an uninfected state and 1–4 weeks post-infection in order to illustrate the dynamic nature of B cell responses during Pneumocystis infection. We identified continuously increased plasma cells and an elevated ratio of (IgA + IgG) to (IgD + IgM) after infection. Moreover, Pneumocystis infection was associated with an increasing naïve B subset characterized by elevated expression of the transcription factor ATF3. The proportion of clonal expanded cells progressively increased, while BCR diversity decreased. Plasma cells exhibited higher levels of somatic hypermutation than naïve B cells. Biased usage of V(D)J genes was observed, and the usage frequency of IGHV9-3 rose. Overall, these results present a detailed atlas of B cell transcriptional changes and BCR repertoire features in the context of Pneumocystis infection, which provides valuable information for finding diagnostic biomarkers and developing potential immunotherapeutic targets.

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Rewiring of B cell receptor signaling by Epstein–Barr virus LMP2A

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2007946117 ◽

2020 ◽

Vol 117 (42) ◽

pp. 26318-26327

Author(s):

Kamonwan Fish ◽

Federico Comoglio ◽

Arthur L. Shaffer ◽

Yanlong Ji ◽

Kuan-Ting Pan ◽

...

Keyword(s):

Cell Cycle ◽

B Cells ◽

B Cell ◽

Epstein Barr Virus ◽

Cell Receptor ◽

B Cell Receptor ◽

Barr Virus ◽

Human B Cells ◽

Bcr Signaling ◽

Epstein Barr

Epstein–Barr virus (EBV) infects human B cells and reprograms them to allow virus replication and persistence. One key viral factor in this process is latent membrane protein 2A (LMP2A), which has been described as a B cell receptor (BCR) mimic promoting malignant transformation. However, how LMP2A signaling contributes to tumorigenesis remains elusive. By comparing LMP2A and BCR signaling in primary human B cells using phosphoproteomics and transcriptome profiling, we identified molecular mechanisms through which LMP2A affects B cell biology. Consistent with the literature, we found that LMP2A mimics a subset of BCR signaling events, including tyrosine phosphorylation of the kinase SYK, the calcium initiation complex consisting of BLNK, BTK, and PLCγ2, and its downstream transcription factor NFAT. However, the majority of LMP2A-induced signaling events markedly differed from those induced by BCR stimulation. These included differential phosphorylation of kinases, phosphatases, adaptor proteins, transcription factors such as nuclear factor κB (NF-κB) and TCF3, as well as widespread changes in the transcriptional output of LMP2A-expressing B cells. LMP2A affected apoptosis and cell-cycle checkpoints by dysregulating the expression of apoptosis regulators such as BCl-xL and the tumor suppressor retinoblastoma-associated protein 1 (RB1). LMP2A cooperated with MYC and mutant cyclin D3, two oncogenic drivers of Burkitt lymphoma, to promote proliferation and survival of primary human B cells by counteracting MYC-induced apoptosis and by inhibiting RB1 function, thereby promoting cell-cycle progression. Our results indicate that LMP2A is not a pure BCR mimic but rather rewires intracellular signaling in EBV-infected B cells that optimizes cell survival and proliferation, setting the stage for oncogenic transformation.

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