scholarly journals The sequential role of Mst1/mTORC1/STAT1 activity in chemokine receptor 2-regulated B cell receptor signaling

2021 ◽  
Author(s):  
Yingzi Zhu ◽  
Heng Gu ◽  
Lu Yang ◽  
Na Li ◽  
Qiuyue Chen ◽  
...  
Keyword(s):  
Cell Signaling ◽  
B Cell ◽  
Signaling Pathway ◽  
Cell Activation ◽  
Cell Receptor ◽  
B Cell Receptor ◽  
B Cell Activation ◽  
B Cell Signaling ◽  
Bcr Signaling

Background: Chemokine (C-C motif) receptor 2 (CCR2) contributes to autoimmune pathogenesis. However, the effect of CCR2 on B cell signaling and its role in autoimmunity remains unclear. Herein, we investigated the role of CCR2 in the B cell receptor (BCR) signaling pathway and aimed to illustrate its potential molecular mechanisms of action. Methods: To investigate the alterations in B cell signaling and the immune response, we used flow cytometry, western blotting, microscopic techniques, Seahorse assay, and immunofluorescence assay on samples from C57BL/6 mice and germinal CCR2-deletion mice. Results: The absence of CCR2 disturbed follicular B cell development. Furthermore, CCR2 absence was correlated with increased mTORC1-mediated energy metabolism and enhanced early B cell activation, which were induced by the up-regulation of BCR proximal signaling and F-actin accumulation. Mst1 and STAT1 were key factors in up-regulating the B cell activation in CCR2 deficient mice. The disrupted peripheral B cell differentiation and enhanced B cell signaling were associated with the inhibition mTORC1, Mst1, and STAT1. Moreover, loss of CCR2 caused a weakened T cell dependent antigen response, resulting in decreased antibody secreting cells and diminished antigen specific IgM levels. Conclusion: CCR2 is involved in the regulation of BCR signaling pathway by sequentially activating signaling pathways dominated by Mst1, mTORC1, and STAT1. Our study suggests that CCR2 might represent a novel therapeutic targeted for autoimmune diseases.

Low-affinity Fcγ receptors, autoimmunity and infection

2009 ◽  
Vol 11 ◽  
Author(s):  
Lisa C. Willcocks ◽  
Kenneth G.C. Smith ◽  
Menna R. Clatworthy
Keyword(s):  
B Cell ◽  
Cell Activation ◽  
Cell Receptor ◽  
B Cell Receptor ◽  
B Cell Activation ◽  
Antibody Dependent Cellular Cytotoxicity ◽  
Igg Antibodies ◽  
Fcγ Receptors ◽  
Susceptibility To Infection

Low-affinity Fcγ receptors (FcγRs) mediate the effects of immunoglobulin G (IgG) antibodies on leukocytes, including recruitment to inflammatory lesions, phagocytosis, antibody-dependent cellular cytotoxicity, release of inflammatory mediators and regulation of B cell activation. These functions are an important part of the mammalian response to infection, but if deployed inappropriately can cause autoimmune disease. Although most FcγRs are activatory, there is also an inhibitory FcγR that, when bound to IgG immune complexes, is able to downregulate the effects of both the activatory FcγRs and the B cell receptor. This review discusses the role of the low-affinity FcγRs in a balanced immune response and how perturbations in FcγR function result in susceptibility to infection or autoimmunity.

LIME acts as a transmembrane adapter mediating BCR-dependent B-cell activation

Blood ◽  
2006 ◽  
Vol 107 (4) ◽  
pp. 1521-1527 ◽  
Author(s):  
Eunseon Ahn ◽  
Hyunsook Lee ◽  
Yungdae Yun
Keyword(s):  
B Cell ◽  
Cell Activation ◽  
Cell Receptor ◽  
B Cell Receptor ◽  
Calcium Flux ◽  
B Cell Activation ◽  
Downstream Signaling ◽  
Signaling Complex ◽  
Bcr Signaling ◽  
Initial Activation

Assembly of a signaling complex around the transmembrane adapter LAT is essential for the transmission of T-cell receptor (TCR)-mediated signaling. However, a LAT-like molecule responsible for the initial activation events in B-cell receptor (BCR) signaling has not yet been identified. Here, we show that LIME is a transmembrane adaptor required for BCR-mediated B-cell activation. LIME was found to be expressed in mouse splenic B cells. Upon BCR cross-linking, LIME was tyrosine phosphorylated by Lyn and associated with Lyn, Grb2, PLC-γ2, and PI3K. Reduction of LIME expression by the introduction of siRNA resulted in the disruption of BCR-mediated activation of MAPK, calcium flux, NF-AT, PI3K, and NF-κB. Taken together, these results establish that LIME is an essential transmembrane adaptor linking BCR ligation to the downstream signaling events that lead to B-cell activation.

scholarly journals The Bacterial Enzyme IdeS Cleaves the IgG-Type of B Cell Receptor (BCR), Abolishes BCR-Mediated Cell Signaling, and Inhibits Memory B Cell Activation

2015 ◽  
Vol 195 (12) ◽  
pp. 5592-5601 ◽  
Author(s):  
Sofia Järnum ◽  
Robert Bockermann ◽  
Anna Runström ◽  
Lena Winstedt ◽  
Christian Kjellman
Keyword(s):  
Cell Signaling ◽  
B Cell ◽  
Cell Activation ◽  
Cell Receptor ◽  
B Cell Receptor ◽  
B Cell Activation ◽  
Memory B Cell ◽  
Bacterial Enzyme

scholarly journals APEX2 proximity biotinylation reveals protein dynamics triggered by B cell receptor activation

2020 ◽  
Author(s):  
Luqman O Awoniyi ◽  
Vid Šuštar ◽  
Sara Hernández-Pérez ◽  
Marika Vainio ◽  
Alexey V Sarapulov ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Lipid Raft ◽  
Cell Activation ◽  
Kinetic Resolution ◽  
Cell Receptor ◽  
Receptor Activation ◽  
B Cell Receptor ◽  
B Cell Activation ◽  
Bcr Signaling

ABSTRACTB lymphocytes form a central part of the adaptive immune system, helping to clear infections by mounting antibody responses and immunological memory. B cell activation is critically controlled by a specific antigen receptor, the B cell receptor (BCR), which triggers a complex, multibranched signaling cascade initiating various cellular changes. While parts of these pathways are reasonably well characterized, we still lack a comprehensive protein-level view of the very dynamic and robust cellular response triggered by antigen engagement. Ability to track, with sufficient kinetic resolution, the protein machineries responding to BCR signaling is imperative to provide new understanding into this complex cell activation event. We address this challenge by using APEX2 proximity labeling technique, that allows capture a major fraction of proteins in a given location with 20nm range and 1min time window, and target the APEX2 enzyme to the plasma membrane lipid raft domain, where BCR efficiently translocates upon activation. Our data provides unprecedented insights into the protein composition of lipid raft environment in B cells, and the changes triggered there upon BCR cross-linking and translocation. In total, we identified 1677 proteins locating at the vicinity of lipid raft domains in cultured mouse B cells. The data includes a majority of proteins known to be involved in proximal BCR signaling. Interestingly, our differential enrichment analysis identified various proteins that underwent dynamic changes in their localization but that had no previously known linkage to early B cell activation. As expected, we also identified, for example, a wealth of proteins linked to clathrin-mediated endocytosis that were recruited to the lipid rafts upon cell activation. We believe that his data serves as a valuable record of proteins involved in BCR activation response and aid various future studies in the field.

scholarly journals Functional Outcome of B Cell Activation by Chromatin Immune Complex Engagement of the B Cell Receptor and TLR9

2007 ◽  
Vol 179 (11) ◽  
pp. 7397-7405 ◽  
Author(s):  
Liliana Busconi ◽  
Jason W. Bauer ◽  
Joseph R. Tumang ◽  
Amy Laws ◽  
Kristin Perkins-Mesires ◽  
...  
Keyword(s):  
B Cell ◽  
Functional Outcome ◽  
Immune Complex ◽  
Cell Activation ◽  
Cell Receptor ◽  
B Cell Receptor ◽  
B Cell Activation

scholarly journals PTIP chromatin regulator controls development and activation of B cell subsets to license humoral immunity in mice

2017 ◽  
Vol 114 (44) ◽  
pp. E9328-E9337 ◽  
Author(s):  
Dan Su ◽  
Stijn Vanhee ◽  
Rebeca Soria ◽  
Elin Jaensson Gyllenbäck ◽  
Linda M. Starnes ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Humoral Immunity ◽  
Cell Activation ◽  
Cell Receptor ◽  
B Cell Receptor ◽  
Transactivation Domain ◽  
B Cell Activation ◽  
Chromatin Regulator ◽  
B Cell Subsets

B cell receptor signaling and downstream NF-κB activity are crucial for the maturation and functionality of all major B cell subsets, yet the molecular players in these signaling events are not fully understood. Here we use several genetically modified mouse models to demonstrate that expression of the multifunctional BRCT (BRCA1 C-terminal) domain-containing PTIP (Pax transactivation domain-interacting protein) chromatin regulator is controlled by B cell activation and potentiates steady-state and postimmune antibody production in vivo. By examining the effects of PTIP deficiency in mice at various ages during ontogeny, we demonstrate that PTIP promotes bone marrow B cell development as well as the neonatal establishment and subsequent long-term maintenance of self-reactive B-1 B cells. Furthermore, we find that PTIP is required for B cell receptor- and T:B interaction-induced proliferation, differentiation of follicular B cells during germinal center formation, and normal signaling through the classical NF-κB pathway. Together with the previously identified role for PTIP in promoting sterile transcription at the Igh locus, the present results establish PTIP as a licensing factor for humoral immunity that acts at several junctures of B lineage maturation and effector cell differentiation by controlling B cell activation.

High ZAP-70 and Differential Expression of B-Cell Receptor Related Genes in Chronic Lymphocytic Leukemia with V3-21 Gene Usage.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 773-773
Author(s):  
Dirk Kienle ◽  
Alexander Kröber ◽  
Dirk Winkler ◽  
Daniel Mertens ◽  
Annett Habermann ◽  
...  
Keyword(s):  
Gene Expression ◽  
B Cell ◽  
Cell Receptor ◽  
B Cell Receptor ◽  
Lymphocytic Leukemia ◽  
Mutation Status ◽  
Bcr Signaling ◽  
Gene Usage ◽  
Lower Expression

Abstract V3-21 gene usage defines a distinct genetic subgroup of chronic lymphocytic leukemia (CLL) characterized by a poor clinical outcome regardless of the VH mutation status. V3-21 cases exhibit a highly characteristic B-cell receptor (BCR) structure as demonstrated by homologous CDR3 sequences and a restricted use of VL genes implicating a common antigen involved in tumor pathogenesis of this specific CLL subgroup. To investigate the role of antigenic stimulation in the pathogenesis of V3-21 using CLL, we analyzed the quantitative expression of genes involved in BCR signaling (ZAP-70, SYK, BLNK, LYN, PI3K, PLCG2, FOS), B-cell activation (TRAF3, STAT6, NFKB), and cell cycle or apoptosis control (ATM, BCL-2, BAX, CDK4, CCND1, CCND2, CCND3, p27, E2F1, MYC) in V3-21 cases in comparison to VH mutated (VH MUT) and VH unmutated (VH UM) cases not using the V3-21 gene. To obtain native expression signatures we studied a non-CD19-purified (nPU) cohort (V3-21: 18 cases, equally divided into VH mutated and VH unmutated cases; VH MUT: 17; VH UM: 19) and, for verification, a CD19-purified (PU) cohort (V3-21: 10 cases, equally divided into VH mutated and unmutated; VH MUT: 12; VH UM: 16) to exclude a contamination of the results by non-tumor cells. All cases were analyzed by FISH for +3q, 6q-, +8q, 11q-, +12q, 13q-, 17p-, and t(11;14) to avoid major imbalances of genomic alterations between the subgroups under study. As expected, ZAP-70 expression was higher in VH UM as compared to VH MUT cases in the nPU (p=0.007) as well as the PU cohort (p=0.009). V3-21 cases showed a higher ZAP-70 expression as compared to VH MUT (nPU: p=0.033; PU: p=0.038). This applied also when restricting this comparison to V3-21 mutated cases (nPU: p=0.018). Median ZAP-70 expression in the PU cohort was 1.15 in VH MUT vs. 7.69 in VH UM cases, as compared to 7.05 in V3-21 cases (V3-21 mutated cases: 10.69; V3-21 unmutated: 6.7). Other genes differentially expressed between the V3-21 and VH MUT subgroups in nPU cases were PI3K (p=0.048), PLCG2 (p=0.007), CCND2 (p=0.003), p27 (p=0.003), BCL-2 (p=0.025), and ATM (p=0.006). In addition, a set of genes was detected with a differential expression between V3-21 and VH UM (nPU) including PLCG2 (p=0.014), NFKB (p=0.023), CCND2 (p=0.001), p27 (0.002), and BAX (p=0.028). Notably, except for ZAP-70, all of the differentially expressed genes showed a lower expression in V3-21 as compared to the other subgroups. When comparing the V3-21 mutated and V3-21 unmutated subgroups (nPU), there were no significant gene expression differences except for CDK4, which showed a lower expression in V3-21 unmutated cases. Therefore, cases with V3-21 usage appear to show a rather homogeneous gene expression pattern independently of the VH mutation status, which can be distinguished from VH MUT and VH UM cases not using V3-21. The expression differences observed suggest a role of differential BCR signaling in the pathogenesis of this distinct CLL subgroup. Deregulation of cell cycle, apoptosis, and candidate genes such as ATM indicate the involvement of additional pathways in the pathogenesis of CLL cases using V3-21.

An HSP90 Inhibitor, PU-H71, Antagonizes Stroma-Induced Pro-Survival Effects in CLL through Its Inhibition of Multi-Component B-Cell Receptor Signaling Pathway

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 5289-5289
Author(s):  
Ailin Guo ◽  
Pin Lu ◽  
Chaojie Zhen ◽  
Gabriela Chiosis ◽  
Yue Lynn Wang
Keyword(s):  
B Cell ◽  
Signaling Pathway ◽  
Cell Receptor ◽  
Hsp90 Inhibitor ◽  
B Cell Receptor ◽  
Receptor Signaling ◽  
Bcr Signaling ◽  
Receptor Signaling Pathway ◽  
B Cell Receptor Signaling ◽  
Cell Receptor Signaling

Abstract Background: Chronic lymphocytic leukemia (CLL) is characterized by the accumulation of B-cells in the hematopoietic system. The B-cell receptor (BCR) plays an essential role in the pathogenesis of CLL and many components of the BCR signaling pathway are known clients of HSP90. HSP90 is a highly conserved molecular chaperone that ensures the proper folding and stabilization of its client proteins. In this study, we investigated whether PU-H71 a novel purine-scaffold HSP90 Inhibitor, has anti-tumor activity in CLL by destabilizing BCR signaling pathway constituents. Design: Fresh CLL cells were isolated and cultured ex vivo with or without stromal co-culture. Molecular and cellular events were studied in PU-H71-treated and control CLL cells. Results: Immunoblotting revealed that a significantly higher amount of HSP90 is present in CLL cells than in peripheral blood mononuclear cells (PBMC), suggesting the chaperone is pathogenically relevant. We found that PU-H71 caused the death of CLL cells in a dose and time dependent manner while the viability of either PBMC or normal B lymphocytes were not affected. PU-H71 induced apoptosis resulting in CLL cell death as it caused mitochondrial cytochrome C release and a decrease in the abundance of several anti-apoptotic proteins. Interestingly, PU-H71 has the ability to counteract the pro-survival effects of the stroma and caused apoptosis in CLL cells co-cultured with stroma. To gain mechanistic insights into how PU-H71 acts, we examined the BCR signaling pathway. We found that the amounts of several key components of the pathway were reduced by PU-H71 treatment. This occurred even in the presence of stromal co-culture. The results suggest that PU-H71 antagonizes the function of HSP90 leading to the destabilization of the BCR signaling transducers. A chemical pull-down experiment revealed the co-existence of the BCR components and HSP90 in the same complex, suggesting these BCR constituents are indeed clients of HSP90 in CLL cells. Further, specific genetic knock-down of the signal transducers by siRNA confirmed their key roles in mediating the survival of CLL cells. Conclusions: PU-H71 antagonizes stroma-induced pro-survival effects in CLL through its inhibition of the B-cell receptor signaling pathway. Our results suggest that PU-H71 may serve as a useful therapy against CLL and is worth further clinical development. Disclosures No relevant conflicts of interest to declare.

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