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1.
Proc Natl Acad Sci U S A ; 116(27): 13480-13489, 2019 07 02.
Artigo em Inglês | MEDLINE | ID: mdl-31127044

RESUMO

IgA is the most abundantly produced antibody in the body and plays a crucial role in gut homeostasis and mucosal immunity. IgA forms a dimer that covalently associates with the joining (J) chain, which is essential for IgA transport into the mucosa. Here, we demonstrate that the marginal zone B and B-1 cell-specific protein (MZB1) interacts with IgA through the α-heavy-chain tailpiece dependent on the penultimate cysteine residue and prevents the intracellular degradation of α-light-chain complexes. Moreover, MZB1 promotes J-chain binding to IgA and the secretion of dimeric IgA. MZB1-deficient mice are impaired in secreting large amounts of IgA into the gut in response to acute inflammation and develop severe colitis. Oral administration of a monoclonal IgA significantly ameliorated the colitis, accompanied by normalization of the gut microbiota composition. The present study identifies a molecular chaperone that promotes J-chain binding to IgA and reveals an important mechanism that controls the quantity, quality, and function of IgA.


Assuntos
Colite/metabolismo , Imunoglobulina A Secretora/metabolismo , Cadeias J de Imunoglobulina/metabolismo , Chaperonas Moleculares/fisiologia , Animais , Colite/induzido quimicamente , Colite/imunologia , Sulfato de Dextrana/farmacologia , Feminino , Microbioma Gastrointestinal , Imunoglobulina G/metabolismo , Imunoglobulina M/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout
2.
Int Immunol ; 32(1): 17-26, 2020 01 09.
Artigo em Inglês | MEDLINE | ID: mdl-31412363

RESUMO

B-cell novel protein 1 (BCNP1) has recently been identified as a new B-cell receptor (BCR) signaling molecule but its physiological function remains unknown. Here, we demonstrate that mice deficient in BCNP1 exhibit impaired B-cell maturation and a reduction of B-1a cells. BCNP1-deficient spleen B cells show enhanced survival, proliferation and Ca2+ influx in response to BCR cross-linking as compared with wild-type spleen B cells. Consistently, mutant B cells show elevated phosphorylation of SYK, B-cell linker protein (BLNK) and PLCγ2 upon BCR cross-linking. In vivo, BCNP1-deficient mice exhibit enhanced humoral immune responses to T-independent and T-dependent antigens. Moreover, aged mutant mice contain elevated levels of serum IgM and IgG3 antibodies and exhibit polyclonal and monoclonal B-cell expansion in lymphoid organs. These results reveal distinct roles for BCNP1 in B-cell development, activation and homeostasis.


Assuntos
Proteínas Adaptadoras de Transdução de Sinal/imunologia , Linfócitos B/imunologia , Proteínas Adaptadoras de Transdução de Sinal/deficiência , Animais , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout
3.
Eur J Immunol ; 49(6): 911-917, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-30888050

RESUMO

The BCR plays a central role in B cell development, survival, activation, and differentiation. We have identified the B cell novel protein 1 (BCNP1) as a new regulator of BCR signaling. BCNP1 contains a pleckstrin homology domain, three proline-rich motifs, and a potential SH2 binding site, and is predominantly expressed by B cells. We found that BCNP1 overexpression in WEHI231 immature B cells potentiated α-IgM-induced apoptosis. Conversely, BCNP1-deficient WEHI231 cells, generated by CRISPR-Cas9-mediated genome editing, exhibited reduced apoptosis after BCR crosslinking. Biochemical analyses revealed that BCNP1 physically interacted with the B cell linker protein (BLNK), Grb2, and PLCγ2. Moreover, absence of BCNP1 resulted in accelerated dephosphorylation of BLNK, reduced phosphorylation of SYK and PLCγ2, and decreased Ca2+ influx after BCR crosslinking. These results demonstrate that BCNP1 promotes BCR signaling by modulating the phosphorylation of BLNK, SYK, and PLCγ2.


Assuntos
Proteínas Reguladoras de Apoptose/imunologia , Apoptose/imunologia , Linfócitos B/imunologia , Receptores de Antígenos de Linfócitos B/imunologia , Transdução de Sinais/imunologia , Animais , Proteínas Reguladoras de Apoptose/metabolismo , Linfócitos B/metabolismo , Linhagem Celular , Proteínas de Membrana/imunologia , Proteínas de Membrana/metabolismo , Camundongos , Receptores de Antígenos de Linfócitos B/metabolismo
4.
Adv Exp Med Biol ; 1254: 75-86, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32323271

RESUMO

Immunoglobulin (Ig) M is the first antibody isotype produced during an immune response and is critical for host defense against infections. Recent studies have revealed that IgM also plays an important role in immune regulation and immunological tolerance. Mice lacking secretory IgM not only exhibit impaired production of antigen-specific IgG and are more susceptible to bacterial and viral infections, but also produce autoantibodies and are prone to develop autoimmune diseases. For many years, IgM has been thought to function predominantly by binding to antigen and activating complement (C') system. It is now clear that IgM can also elicit its function through the IgM Fc receptor (FcµR). In this chapter, we will review the role of FcµR in B cell development, maturation, survival and activation, antibody production, host defense against bacterial and viral infections, and B cell tolerance. We will also discuss the relative contribution of IgM-C' and IgM-FcµR pathways in humoral immune responses. Finally, we will discuss the possible involvement of FcµR in human chronic lymphocytic leukemia.


Assuntos
Linfócitos B , Tolerância Imunológica , Imunidade Humoral , Receptores Fc , Animais , Humanos
5.
J Immunol ; 199(9): 3023-3030, 2017 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-28939756

RESUMO

Activation-induced cytidine deaminase (AID) initiates both somatic hypermutation (SHM) and class switch recombination (CSR) of Ig genes. How AID is targeted to the Ig V gene and switch region to trigger SHM and CSR remains elusive. Primary B cells stimulated with CD40L plus IL-4 or LPS plus IL-4 undergo efficient CSR, but it has been difficult to induce SHM in these cells. In the current study, we used B cells from B1-8hi mice carrying a prerecombined VH186.2DFL16.1JH2 Ab gene to investigate the induction of SHM under in vitro culture conditions. B1-8hi splenic B cells stimulated with CD40L plus IL-4 or LPS plus IL-4 underwent robust CSR to IgG1, but failed to generate SHM in the VH186.2 gene. Remarkably, ectopic expression of AID in AID-deficient, but not wild-type, B1-8hi B cells induced efficient SHM at a rate close to that observed in germinal center B cells. We further established an AID-deficient CH12 B lymphoma line and found that ectopic expression of AID in the mutant line, but not in AID-sufficient CH12 cells, induced efficient point mutations and deletions in the V gene. These results demonstrate that the endogenous AID in ex vivo-activated primary B and B lymphoma cells not only cannot induce SHM but also inhibit the induction of SHM by the exogenous AID. Our results further suggest that the spatiotemporal distribution and/or posttranslational modification of AID strongly affects the induction of SHM in ex vivo-activated primary B cells.


Assuntos
Linfócitos B/imunologia , Citidina Desaminase/imunologia , Imunoglobulina G/imunologia , Ativação Linfocitária , Hipermutação Somática de Imunoglobulina , Animais , Linhagem Celular Tumoral , Citidina Desaminase/genética , Imunoglobulina G/genética , Camundongos , Camundongos Knockout , Mutação Puntual
6.
Exp Cell Res ; 340(1): 62-70, 2016 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-26708617

RESUMO

Previous studies suggest that early growth response gene-1 (Egr-1) plays an important role in hypoxia-induced drug-resistance. However, the mechanism still remains to be clarified. Herein, we investigated the role of Egr-1 in hypoxia-induced autophagy and its resulted hypoxia-driven chemo-resistance in Hepatocellular Carcinoma (HCC) cells. Our data demonstrated that Egr-1 was overexpressed in HCC tissues and cells and conferred them drug resistance under hypoxia. Mechanistically, Egr-1 transcriptionally regulated hypoxia-induced autophagy by binding to LC3 promoter in HCC cells, which resulted in resistance of HCC cells to chemotherapeutic agents; while dominant negative Egr-1 could inhibit autophagy level, and thus enhanced the sensitivity of HCC cells to chemotherapeutic agents, indicating that hypoxia-induced Egr-1 expression enhanced drug resistance of HCC cells likely through autophagy. Accordingly, it is suggested that a mechanism of hypoxia/Egr-1/autophagy axis might be involved in drug resistance in HCC.


Assuntos
Protocolos de Quimioterapia Combinada Antineoplásica/farmacologia , Autofagia , Carcinoma Hepatocelular/tratamento farmacológico , Resistencia a Medicamentos Antineoplásicos , Proteína 1 de Resposta de Crescimento Precoce/metabolismo , Neoplasias Hepáticas/tratamento farmacológico , Autofagia/efeitos dos fármacos , Carcinoma Hepatocelular/metabolismo , Carcinoma Hepatocelular/patologia , Ciclo Celular/efeitos dos fármacos , Hipóxia Celular/efeitos dos fármacos , Relação Dose-Resposta a Droga , Resistencia a Medicamentos Antineoplásicos/efeitos dos fármacos , Ensaios de Seleção de Medicamentos Antitumorais , Proteína 1 de Resposta de Crescimento Precoce/genética , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Células Hep G2 , Humanos , Neoplasias Hepáticas/metabolismo , Neoplasias Hepáticas/patologia , Relação Estrutura-Atividade , Células Tumorais Cultivadas
7.
Exp Cell Res ; 319(12): 1714-1723, 2013 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-23684856

RESUMO

Previous studies suggest that ING4, a novel member of ING (inhibitor of growth) family, can inhibit brain tumor growth. However, whether autophagy is involved in ING4-induced cell death still remains unknown. In this study, we found that in addition to apoptosis, autophagy also contributed to cell death induced by ING4. Autophagy levels were elevated following the exposure to Ad-ING4, including enhanced fluorescence intensity of monodansylcadervarine (MDC), a specific in vivo marker for autophagic vacuoles, and increased expression levels of the LC3-II and Beclin-1, wheras the autophagic levels were attenuated following the pretreatment of 3-MA, the inhibitor of autophagy, which significantly decreased the Ad-ING4-induced cell death compared with caspase inhibitor zVAD. Furthermore, ING4 also induced mitochondrial dysfunction, such as mitophagy, collapse of mitochondrial membrane potential and the intracellular ROS, which indicated that mitochondria might be associated with the process of autophagic cell death of glioma cells. Finally, the relationship among Bax, Bcl-2, Beclin-1 and caspase family proteins levels were analyzed in glioma cells U251MG and LN229 infected with Ad-ING4 or Ad-lacZ. It is suggested that both autophagy and apoptosis could contribute to ING4-induced glioma cell death, and mitochondria might play an important role in this process. Our findings reveal novel aspects of the autophagy in glioma cells that underlie the cytotoxic action of ING4, possibly providing new insights in the development of combinatorial therapies for gliomas.


Assuntos
Apoptose , Autofagia , Neoplasias Encefálicas/metabolismo , Proteínas de Ciclo Celular/metabolismo , Glioma/metabolismo , Proteínas de Homeodomínio/metabolismo , Proteínas Supressoras de Tumor/metabolismo , Proteínas Reguladoras de Apoptose/metabolismo , Proteína Beclina-1 , Neoplasias Encefálicas/patologia , Inibidores de Caspase/farmacologia , Caspases/metabolismo , Linhagem Celular Tumoral , Glioma/patologia , Humanos , Potencial da Membrana Mitocondrial , Proteínas de Membrana/metabolismo , Proteínas Associadas aos Microtúbulos/metabolismo , Mitocôndrias/metabolismo , Mitofagia , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , Espécies Reativas de Oxigênio/metabolismo , Vacúolos/metabolismo , Proteína X Associada a bcl-2/metabolismo
8.
Front Immunol ; 13: 1083119, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36685499

RESUMO

Introduction: The differentiation of B cells into antibody-secreting plasma cells depends on cell division-coupled, epigenetic and other cellular processes that are incompletely understood. Methods: We have developed a CRISPR/Cas9-based screen that models an early stage of T cell-dependent plasma cell differentiation and measures B cell survival or proliferation versus the formation of CD138+ plasmablasts. Here, we refined and extended this screen to more than 500 candidate genes that are highly expressed in plasma cells. Results: Among known genes whose deletion preferentially or mostly affected plasmablast formation were the transcription factors Prdm1 (BLIMP1), Irf4 and Pou2af1 (OBF-1), and the Ern1 gene encoding IRE1a, while deletion of XBP1, the transcriptional master regulator that specifies the expansion of the secretory program in plasma cells, had no effect. Defective plasmablast formation caused by Ern1 deletion could not be rescued by the active, spliced form of XBP1 whose processing is dependent on and downstream of IRE1a, suggesting that in early plasma cell differentiation IRE1a acts independently of XBP1. Moreover, we newly identified several genes involved in NF-kB signaling (Nfkbia), vesicle trafficking (Arf4, Preb) and epigenetic regulators that form part of the NuRD complex (Hdac1, Mta2, Mbd2) to be required for plasmablast formation. Deletion of ARF4, a small GTPase required for COPI vesicle formation, impaired plasmablast formation and blocked antibody secretion. After Hdac1 deletion plasmablast differentiation was consistently reduced by about 50%, while deletion of the closely related Hdac2 gene had no effect. Hdac1 knock-out led to strongly perturbed protein expression of antagonistic transcription factors that govern plasma cell versus B cell identity (by decreasing IRF4 and BLIMP1 and increasing BACH2 and PAX5). Discussion: Taken together, our results highlight specific and non-redundant roles for Ern1, Arf4 and Hdac1 in the early steps of plasma cell differentiation.


Assuntos
Linfócitos B , Sistemas CRISPR-Cas , Plasmócitos , Diferenciação Celular/genética , Anticorpos
9.
Front Oncol ; 11: 715593, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34381734

RESUMO

Malic enzyme 2 (ME2) catalyzes the formation of pyruvate from malic acid and is abnormally expressed in some tumors. However, the exact effects of ME2 on proneural-mesenchymal transition (PMT) and lipogenesis in glioblastoma multiforme (GBM) remain unexplored. Here, we found that ME2 expression was significantly higher in GBM than in normal brain tissues and negatively correlated with overall survival of patients with GBM. Furthermore, we demonstrated that ME2 was positively correlated with mesenchymal features in GBM and promoted proliferation, migration, and invasion of glioma cells. Moreover, ME2 upregulated the expression of mesenchymal markers (N-cadherin, vimentin, YKL40, and MET), whereas it inhibited the expression of proneural maker OLIG2, indicating that ME2 might promote PMT in GBM. We also found that ME2 inhibited the production of mitochondrial reactive oxygen species and AMPK phosphorylation, resulting in SREBP-1 maturation and nuclear localization and enhancing the ACSS2 lipogenesis pathway. Taken together, these results suggest that ME2 promotes PMT and is linked with reprogramming of lipogenesis via AMPK-SREBP-1-ACSS2 signaling in GBM. Therefore, ME2 has potential as a new classification marker in GBM and could provide a new approach to glioma treatment.

10.
JCI Insight ; 6(19)2021 10 08.
Artigo em Inglês | MEDLINE | ID: mdl-34622798

RESUMO

Hypomorphic RAG1 or RAG2 mutations cause primary immunodeficiencies and can lead to autoimmunity, but the underlying mechanisms are elusive. We report here a patient carrying a c.116+2T>G homozygous splice site mutation in the first intron of RAG1, which led to aberrant splicing and greatly reduced RAG1 protein expression. B cell development was blocked at both the pro-B to pre-B transition and the pre-B to immature B cell differentiation step. The patient B cells had reduced B cell receptor repertoire diversity and decreased complementarity determining region 3 lengths. Despite B cell lymphopenia, the patient had abundant plasma cells in the BM and produced large quantities of IgM and IgG Abs, including autoantibodies. The proportion of naive B cells was reduced while the frequency of IgD-CD27- double-negative (DN) B cells, which quickly differentiated into Ab-secreting plasma cells upon stimulation, was greatly increased. Immune phenotype analysis of 52 patients with primary immunodeficiency revealed a strong association of the increased proportion of DN B and memory B cells with decreased number and proportion of naive B cells. These results suggest that the lymphopenic environment triggered naive B cell differentiation into DN B and memory B cells, leading to increased Ab production.


Assuntos
Autoanticorpos/imunologia , Doenças Autoimunes/genética , Linfócitos B/imunologia , Granuloma/genética , Proteínas de Homeodomínio/genética , Síndromes de Imunodeficiência/genética , Linfopoese/genética , Receptores de Antígenos de Linfócitos B/imunologia , Doenças Autoimunes/imunologia , Doenças Autoimunes/terapia , Criança , Transplante de Células-Tronco de Sangue do Cordão Umbilical , Evolução Fatal , Granuloma/imunologia , Granuloma/terapia , Proteínas de Homeodomínio/metabolismo , Homozigoto , Humanos , Imunoglobulina G/imunologia , Imunoglobulina M/imunologia , Síndromes de Imunodeficiência/imunologia , Síndromes de Imunodeficiência/terapia , Memória Imunológica/imunologia , Linfopenia/genética , Linfopenia/imunologia , Linfopoese/imunologia , Masculino , Plasmócitos/imunologia , Sítios de Splice de RNA/genética , Recombinação V(D)J/genética
11.
Front Immunol ; 10: 529, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30967868

RESUMO

Immunoglobulin (Ig) M is the first antibody isotype to appear during evolution, ontogeny and immune responses. IgM not only serves as the first line of host defense against infections but also plays an important role in immune regulation and immunological tolerance. For many years, IgM is thought to function by binding to antigen and activating complement system. With the discovery of the IgM Fc receptor (FcµR), it is now clear that IgM can also elicit its function through FcµR. In this review, we will describe the molecular characteristics of FcµR, its role in B cell development, maturation and activation, humoral immune responses, host defense, and immunological tolerance. We will also discuss the functional relationship between IgM-complement and IgM-FcµR pathways in regulating immunity and tolerance. Finally, we will discuss the potential involvement of FcµR in human diseases.


Assuntos
Linfócitos B/imunologia , Imunoglobulina M/imunologia , Ativação Linfocitária , Receptores Fc/imunologia , Animais , Humanos , Tolerância Imunológica
12.
Mol Immunol ; 105: 173-180, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30529036

RESUMO

CD40 ligand (CD40 L) expressed by activated T cells interacts with CD40 on B cells and triggers B cell survival, proliferation and differentiation. Deficiency in CD40 L or CD40 in humans causes hyper IgM syndrome due to a defect in T-B interaction that is essential for Ig gene class switch recombination (CSR). CD40 L belongs to the tumor necrosis factor family and normally forms a homotrimer on the cell surface, which is important for its biological activity. To generate a multimeric CD40 L that can be used to stimulate both mouse and human B cells, we fused the extracellular domain of mouse CD40 L, which is known to also bind human CD40, with streptavidin (SA) that forms a stable tetramer under physiological conditions. As expected, 293 T cells transiently transfected with an SA-CD40 L expression vector secreted tetrameric SA-CD40 L in the culture supernatant. The secreted SA-CD40 L exhibited > 25-fold stronger activities in inducing the survival, activation and proliferation of both mouse and human primary B cells than did an agonistic anti-mouse or anti-human CD40 antibody. In the presence of IL-4, SA-CD40 L also induced efficient CSR and plasma cell differentiation in both mouse and human B cells. Moreover, administration of SA-CD40 L in mice induced activation and proliferation of spleen B cells in vivo. These results demonstrate that the SA-CD40 L fusion protein generated in the present study recapitulates the function of membrane-bound trimeric CD40 L and has potent biological activities in both mouse and human primary B cells.


Assuntos
Ligante de CD40/farmacologia , Diferenciação Celular/efeitos dos fármacos , Plasmócitos/imunologia , Proteínas Recombinantes de Fusão/farmacologia , Animais , Antígenos CD40/imunologia , Ligante de CD40/genética , Ligante de CD40/imunologia , Diferenciação Celular/imunologia , Feminino , Humanos , Síndrome de Imunodeficiência com Hiper-IgM/tratamento farmacológico , Síndrome de Imunodeficiência com Hiper-IgM/genética , Síndrome de Imunodeficiência com Hiper-IgM/imunologia , Síndrome de Imunodeficiência com Hiper-IgM/patologia , Masculino , Camundongos , Plasmócitos/patologia , Domínios Proteicos , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/imunologia
13.
Front Immunol ; 9: 160, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-29459869

RESUMO

The marginal zone B cells (MZB) are located at the interface between the circulation and lymphoid tissue and as a gatekeeper play important roles in both innate and adaptive immune responses. We have previously found that MZB are significantly reduced in mice deficient in the IgM Fc receptor (FcµR) but how FcµR regulates the development and function of MZB remains unknown. In this study, we found that both marginal zone precursor (MZP) and MZB were decreased in FcµR-/- mice. The reduction of MZP and MZB was not due to impaired proliferation of these cells but rather due to their increased death. Further analysis revealed that FcµR-/- MZB had reduced tonic BCR signal, as evidenced by their decreased levels of phosphorylated SYK and AKT relative to WT MZB. MZB in FcµR-/- mice responded poorly to LPS in vivo when compared with MZB in WT mice. Consistent with the reduced proportion of MZB and their impaired response to LPS, antibody production against the type 1 T-independent Ag, NP-LPS, was significantly reduced in FcµR-/- mice. Moreover, FcµR-/- mice were highly susceptible to Citrobacter rodentium-induced sepsis. These results reveal a critical role for FcµR in the survival and activation of MZB and in protection against acute bacterial infection.


Assuntos
Linfócitos B/imunologia , Ativação Linfocitária , Receptores Fc/genética , Sepse/prevenção & controle , Animais , Apoptose , Linfócitos B/patologia , Citrobacter rodentium , Infecções por Enterobacteriaceae/imunologia , Infecções por Enterobacteriaceae/prevenção & controle , Regulação da Expressão Gênica , Imunidade Humoral , Tecido Linfoide/citologia , Camundongos , Camundongos Knockout , Receptores Fc/imunologia , Sepse/imunologia , Sepse/microbiologia , Baço/imunologia
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