101
|
Affiliation(s)
- S Tsukada
- Department of Molecular Medicine, Osaka University Medical School, Yamadaoka, Suita City, Osaka 565-0871, Japan
| | | | | |
Collapse
|
102
|
Engels N, Merchant M, Pappu R, Chan AC, Longnecker R, Wienands J. Epstein-Barr virus latent membrane protein 2A (LMP2A) employs the SLP-65 signaling module. J Exp Med 2001; 194:255-64. [PMID: 11489945 PMCID: PMC2193464 DOI: 10.1084/jem.194.3.255] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2001] [Accepted: 06/20/2001] [Indexed: 11/29/2022] Open
Abstract
In latently infected B lymphocytes, the Epstein-Barr virus (EBV) suppresses signal transduction from the antigen receptor through expression of the integral latent membrane protein 2A (LMP2A). At the same time, LMP2A triggers B cell survival by a yet uncharacterized maintenance signal that is normally provided by the antigen receptor. The molecular mechanisms are unknown as LMP2A-regulated signaling cascades have not been described so far. Using a novel mouse model we have identified the intracellular adaptor protein Src homology 2 (SH2) domain-containing leukocyte protein (SLP)-65 as a critical downstream effector of LMP2A in vivo. Biochemical analysis of the underlying signaling pathways revealed that EBV infection causes constitutive tyrosine phosphorylation of one of the two SLP-65 isoforms and complex formation between SLP-65 and the protooncoprotein CrkL (CT10 regulator of kinase like). This leads to antigen receptor-independent phosphorylation of Cbl (Casitas B lineage lymphoma) and C3G. In contrast, phospholipase C-gamma2 (PLC-gamma2) activation is completely blocked. Our data show that in order to establish a latent EBV infection, LMP2A selectively activates or represses SLP-65-regulated signaling pathways.
Collapse
Affiliation(s)
- Niklas Engels
- Department of Biochemistry I, University of Bielefeld, Bielefeld D-33615, Germany
| | - Mark Merchant
- Department of Microbiology and Immunology, Northwestern University Medical School, Chicago, IL 60611
| | - Rajita Pappu
- Center for Immunology, Howard Hughes Medical Institute, Washington University School of Medicine, St. Louis, MO 63110
| | - Andrew C. Chan
- Center for Immunology, Howard Hughes Medical Institute, Washington University School of Medicine, St. Louis, MO 63110
| | - Richard Longnecker
- Department of Microbiology and Immunology, Northwestern University Medical School, Chicago, IL 60611
| | - Jürgen Wienands
- Department of Biochemistry I, University of Bielefeld, Bielefeld D-33615, Germany
| |
Collapse
|
103
|
Abstract
B cell development is a highly regulated process whereby functional peripheral subsets are produced from hematopoietic stem cells, in the fetal liver before birth and in the bone marrow afterward. Here we review progress in understanding some aspects of this process in the mouse bone marrow, focusing on delineation of the earliest stages of commitment, on pre-B cell receptor selection, and B cell tolerance during the immature-to-mature B cell transition. Then we note some of the distinctions in hematopoiesis and pre-B selection between fetal liver and adult bone marrow, drawing a connection from fetal development to B-1/CD5(+) B cells. Finally, focusing on CD5(+) cells, we consider the forces that influence the generation and maintenance of this distinctive peripheral B cell population, enriched for natural autoreactive specificities that are encoded by particular germline V(H)-V(L) combinations.
Collapse
Affiliation(s)
- R R Hardy
- Institute for Cancer Research, Fox Chase Cancer Center, 7701 Burholme Ave., Philadelphia, Pennsylvania 19111, USA.
| | | |
Collapse
|
104
|
Jumaa H, Mitterer M, Reth M, Nielsen PJ. The absence of SLP65 and Btk blocks B cell development at the preB cell receptor-positive stage. Eur J Immunol 2001; 31:2164-9. [PMID: 11449370 DOI: 10.1002/1521-4141(200107)31:7<2164::aid-immu2164>3.0.co;2-s] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Mice deficient for the adapter protein SLP65 (BLNK) show a partial block in early B cell development, reduced numbers of mature B cells in the periphery, an absence of B1 cells and a reduction of IgM and IgG3 serum immunoglobulin levels. A strikingly similar phenotype is observed in Btk-deficient mice. To investigate the consequences of mutations in both SLP65 and Btk, we generated SLP65/ Btk double-mutant mice by crossing the single-mutant mice. Analysis of the double-mutant mice reveals a much more severe defect in B cell development. B cells in the SLP65/Btk double-mutant mice are arrested at the preB cell stage and, surprisingly, express the preB cell receptor. Normally, preB cell receptor expression in wild-type mice is restricted to a very small fraction of B cells making it difficult to identify these cells in the bone marrow. Together, the data demonstrate the synergistic role of SLP65 and Btk in B cell development and describe a situation where large numbers of preB cell receptor-positive cells accumulate in the bone marrow and spleen.
Collapse
Affiliation(s)
- H Jumaa
- Molecular Immunology, Biologie III, University of Freiburg and Max Planck Institute for Immunobiology, Freiburg, Germany.
| | | | | | | |
Collapse
|
105
|
Engels N, Wollscheid B, Wienands J. Association of SLP-65/BLNK with the B cell antigen receptor through a non-ITAM tyrosine of Ig-alpha. Eur J Immunol 2001; 31:2126-34. [PMID: 11449366 DOI: 10.1002/1521-4141(200107)31:7<2126::aid-immu2126>3.0.co;2-o] [Citation(s) in RCA: 109] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The cytoplasmic adaptor protein SLP-65 (BLNK or BASH) is a critical downstream effector of the B cell antigen receptor (BCR). Tyrosine-phosphorylated SLP-65 assembles intracellular signaling complexes such as the Ca(2 +) initiation complex encompassing phospholipase C-gamma2 and Bruton's tyrosine kinase. It is, however, unclear how the SLP-65 signaling module can be recruited to the plasma membrane. Here we show that following B cell stimulation, SLP-65 associates directly with the BCR signaling subunit, the Ig-alpha / Ig-beta heterodimer. The interaction is mediated by the Src homology 2 domain of SLP-65 and the phosphorylated Ig-alpha tyrosine 204, which is located outside of the immunoreceptor tyrosine-based activation motif. Our data identify an unexpected BCR phosphorylation pattern and indicate that Ig-alpha has the capability to serve as transmembrane adaptor in BCR signaling.
Collapse
Affiliation(s)
- N Engels
- Institute of Biology III, University of Freiburg and Max Planck Institute of Immunobiology, Freiburg, Germany
| | | | | |
Collapse
|
106
|
Xu S, Lam KP. B-cell maturation protein, which binds the tumor necrosis factor family members BAFF and APRIL, is dispensable for humoral immune responses. Mol Cell Biol 2001; 21:4067-74. [PMID: 11359913 PMCID: PMC87068 DOI: 10.1128/mcb.21.12.4067-4074.2001] [Citation(s) in RCA: 213] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
B-cell maturation protein (BCMA) is a member of the tumor necrosis factor (TNF) receptor family and is expressed in B lymphocytes. BCMA binds two TNF family members, BAFF and APRIL, that stimulate cellular proliferation. BAFF in particular has been shown to influence B-cell survival and activation, and transgenic mice overexpressing BAFF have a lupus-like autoimmune disorder. We have inactivated BCMA in the mouse germ line. BCMA(-/-) mice have normal B-cell development, and the life span of mutant B lymphocytes is comparable to that of wild-type B cells. The humoral immune responses of BCMA(-/-) mice to T-cell-independent antigens as well as high and low doses of T-cell-dependent antigens are also intact. In addition, mutant mice have normal splenic architecture, and germinal centers are formed during an ongoing immune response. These data suggest a functional redundancy of BCMA in B-cell physiology that is probably due to the presence of TACI, another TNF receptor family member that is expressed on B cells and that can also bind BAFF and APRIL.
Collapse
Affiliation(s)
- S Xu
- Institute of Molecular and Cell Biology, Singapore 117609, Republic of Singapore
| | | |
Collapse
|
107
|
Tedford K, Nitschke L, Girkontaite I, Charlesworth A, Chan G, Sakk V, Barbacid M, Fischer KD. Compensation between Vav-1 and Vav-2 in B cell development and antigen receptor signaling. Nat Immunol 2001; 2:548-55. [PMID: 11376343 DOI: 10.1038/88756] [Citation(s) in RCA: 141] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Vav-1 and Vav-2 are closely related Dbl-homology GTP exchange factors (GEFs) for Rho GTPases. Mutation of Vav-1 disrupts T cell development and T cell antigen receptor-induced activation, but has comparatively little effect on B cells. We found that combined deletion of both Vav-1 and Vav-2 in mice resulted in a marked reduction in mature B lymphocyte numbers. Vav-1(-/-)Vav-2(-/-) B cells were unresponsive to B cell antigen receptor (BCR)-driven proliferation in vitro and to thymus-independent antigen in vivo. BCR-stimulated intracellular calcium mobilization was greatly impaired in Vav-1(-/-)Vav-2(-/-) B cells. These findings establish a role for Vav-2 in BCR calcium signaling and reveal that the Vav family of GEFs is critical to B cell development and function.
Collapse
Affiliation(s)
- K Tedford
- Abteilung Physiologische Chemie, Universität Ulm, Albert-Einstein-Allee 11, D-89069 Ulm, Germany
| | | | | | | | | | | | | | | |
Collapse
|
108
|
Tan JE, Wong SC, Gan SK, Xu S, Lam KP. The adaptor protein BLNK is required for b cell antigen receptor-induced activation of nuclear factor-kappa B and cell cycle entry and survival of B lymphocytes. J Biol Chem 2001; 276:20055-63. [PMID: 11274146 DOI: 10.1074/jbc.m010800200] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
B lymphocytes lacking the adaptor protein B cell linker (BLNK) do not proliferate in response to B cell antigen receptor (BCR) engagement. We demonstrate here that BCR-activated BLNK(-)/- B cells fail to enter the cell cycle, and this is due to their inability to induce the expression of the cell cycle regulatory proteins such as cyclin D2 and cyclin-dependent kinase 4. BCR-stimulated BLNK(-)/- B cells also do not up-regulate the cell survival protein Bcl-x(L), which may be necessary for the cells to complete the cell cycle. In addition, BLNK(-)/- B cells exhibit a high rate of spontaneous apoptosis in culture. Examination of the various BCR-activated signaling pathways in mouse BLNK(-)/- B cells reveals the intact activation of Akt and mitogen-activated protein kinases but the impaired activation of nuclear factor (NF)-kappaB that is known to regulate genes involved in cell proliferation and survival. The inability to activate NF-kappaB in BCR-stimulated BLNK(-)/- B cells is due to a failure to induce the degradation of the inhibitory kappaB protein. In all these aspects, BLNK(-)/- B cells resemble xid B cells that have a mutation in Bruton's tyrosine kinase (Btk). Recently, phospholipase C (PLC)-gamma2 has also been demonstrated to be essential for NF-kappaB activation. Since BLNK has been shown separately to interact with both Btk and PLC-gamma2, our finding of normal Btk but impaired PLC-gamma2 activation in BCR-stimulated BLNK(-)/- B cells strongly suggests that BLNK orchestrates the formation of a Btk-PLC-gamma2 signaling axis that regulates NF-kappaB activation. Taken together, the NF-kappaB activation defect may be sufficient to explain the similar defects in BCR-induced B cell proliferation and T cell-independent immune responses in BLNK(-)/-, Btk(-)/-, and PLC-gamma2(-)/- mice.
Collapse
Affiliation(s)
- J E Tan
- Institute of Molecular and Cell Biology, 30 Medical Drive, Singapore 117609, Singapore
| | | | | | | | | |
Collapse
|
109
|
Lewis CM, Broussard C, Czar MJ, Schwartzberg PL. Tec kinases: modulators of lymphocyte signaling and development. Curr Opin Immunol 2001; 13:317-25. [PMID: 11406363 DOI: 10.1016/s0952-7915(00)00221-1] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The Tec kinases are implicated as important components of the antigen receptor signaling required for proper lymphocyte activation and development. Recent data suggest that these kinases contribute to multiprotein complexes containing LAT and SLP-76 in T cells, and BLNK/SLP-65 in B cells, which are required for activation of PLC-gamma and downstream pathways.
Collapse
Affiliation(s)
- C M Lewis
- National Human Genome Research Institute, National Institutes of Health, 20892, Bethesda, MD, USA
| | | | | | | |
Collapse
|
110
|
|
111
|
|
112
|
Merchant M, Swart R, Katzman RB, Ikeda M, Ikeda A, Longnecker R, Dykstra ML, Pierce SK. The effects of the Epstein-Barr virus latent membrane protein 2A on B cell function. Int Rev Immunol 2001; 20:805-35. [PMID: 11913951 DOI: 10.3109/08830180109045591] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Epstein-Barr Virus (EBV) infects B-lymphocytes circulating through the oral epithelium and establishes a lifelong latent infection in a subset of mature-memory B cells. In these latently infected B cells, EBV exhibits limited gene expression with the latent membrane protein 2A (LMP2A) being the most consistently detected transcript. This persistent expression, coupled with many studies ofthe function of LMP2A in vitro and invivo, indicates that LMP2A is functioning to control some aspect of viral latency. Establishment and maintenance of viral latency requires exquisite manipulation of normal B cell signaling and function. LMP2A is capable of blocking normal B cell signal transduction in vitro, suggesting that LMP2A may act to regulate lytic activation from latency in vivo. Furthermore, LMP2A is capable of providing B cells with survival signals in the absence of normal BCR signaling. These data show that LMP2A may help EBV-infected cells to persist in vivo. This review discusses the advances that have been made in our understanding of LMP2A and the effects it has on B cell development, activation, and viral latency.
Collapse
Affiliation(s)
- M Merchant
- Department of Microbiology-Immunology, Northwestern University Medical School, Chicago, Illinois 60611, USA
| | | | | | | | | | | | | | | |
Collapse
|
113
|
Watanabe S, Take H, Takeda K, Yu ZX, Iwata N, Kajigaya S. Characterization of the CIN85 adaptor protein and identification of components involved in CIN85 complexes. Biochem Biophys Res Commun 2000; 278:167-74. [PMID: 11071869 DOI: 10.1006/bbrc.2000.3760] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
CIN85 is an 85-kDa adaptor protein whose functions in signaling pathways are presently unknown. Using the yeast two-hybrid screen, the B cell linker protein (BLNK) was identified as a binding partner of CIN85. Coimmunoprecipitation experiments using mammalian cells revealed that CIN85 directly bound to BLNK through its SH3 domains. Immunostaining analysis showed that CIN85 and BLNK were colocalized in the cytoplasm. These results indicate a potential role of CIN85 in the B cell receptor-mediated signaling pathway. It was also found that Crk-I, Crk-II, p130(Cas), p85-PI3K, Grb2, and Sos1 were components of CIN85 complexes. CIN85 interacted with itself through its coiled-coil region, resulting in formation of a tetramer. Both the coiled-coil region and SH3 domains of CIN85 were responsible for its subcellular localization. Our data suggest that CIN85 may serve for regulation of various signaling events through formation of its diverse complexes.
Collapse
Affiliation(s)
- S Watanabe
- Hematology Branch, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | | | | | | | | | | |
Collapse
|
114
|
Xu S, Wong SC, Lam KP. Cutting edge: B cell linker protein is dispensable for the allelic exclusion of immunoglobulin heavy chain locus but required for the persistence of CD5+ B cells. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2000; 165:4153-7. [PMID: 11035046 DOI: 10.4049/jimmunol.165.8.4153] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The pre-B cell receptor (pre-BCR) and the BCR are required for B lymphopoiesis and for the allelic exclusion of Ig genes. Mice lacking B cell linker (BLNK) protein that is a component of the BCR signaling pathway have impaired B cell development. In this report, we show that allelic exclusion is intact in BLNK(-/-) mice harboring a V(H)12 transgene. This differs from mice lacking the tyrosine kinase Syk that is upstream of BLNK in BCR signaling and contrasts with mice lacking SLP-76 that is the equivalent adaptor molecule in TCR-signal transduction. We also show that, whereas most wild-type V(H)12-expressing B cells are CD5(+), the majority of the splenic V(H)12-expressing BLNK(-/-) B cells are CD5(-). A small population of V(H)12-expressing, BLNK(-/-) CD5(+) B cells is detectable in the peritoneal cavity of younger but not older mice. This suggests that BLNK deficiency affects not only the generation but also the persistence of B-1 cells.
Collapse
Affiliation(s)
- S Xu
- Institute of Molecular and Cell Biology, Singapore, Republic of Singapore
| | | | | |
Collapse
|
115
|
Ishiai M, Kurosaki M, Inabe K, Chan AC, Sugamura K, Kurosaki T. Involvement of LAT, Gads, and Grb2 in compartmentation of SLP-76 to the plasma membrane. J Exp Med 2000; 192:847-56. [PMID: 10993915 PMCID: PMC2193288 DOI: 10.1084/jem.192.6.847] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
B cell linker protein (BLNK) and Src homology 2 domain-containing leukocyte protein of 76 kD (SLP-76) are adaptor proteins required for B cell receptor (BCR) and T cell receptor function, respectively. Here, we show that expression of SLP-76 cannot reconstitute BCR function in Zap-70(+)BLNK(-) B cells. This could be attributable to inability of SLP-76 to be recruited into glycolipid-enriched microdomains (GEMs) after antigen receptor cross-linking. Supporting this idea, the BCR function was restored when a membrane-associated SLP-76 chimera was enforcedly localized to GEMs. Moreover, we demonstrate that addition of both linker for activation of T cells (LAT) and Grb2-related adaptor downstream of Shc (Gads) to SLP-76 allow SLP-76 to be recruited into GEMs, whereby the BCR function is reconstituted. The Gads function was able to be replaced by overexpression of Grb2. In contrast to SLP-76, BLNK did not require Grb2 families for its recruitment to GEMs. Hence, these data suggest a functional overlap between BLNK and SLP-76, while emphasizing the difference in requirement for additional adaptor molecules in their targeting to GEMs.
Collapse
Affiliation(s)
- M Ishiai
- Department of Molecular Genetics, Institute for Liver Research, Kansai Medical University, Moriguchi 570-8506, Japan
| | | | | | | | | | | |
Collapse
|
116
|
Hashimoto A, Takeda K, Inaba M, Sekimata M, Kaisho T, Ikehara S, Homma Y, Akira S, Kurosaki T. Cutting edge: essential role of phospholipase C-gamma 2 in B cell development and function. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2000; 165:1738-42. [PMID: 10925250 DOI: 10.4049/jimmunol.165.4.1738] [Citation(s) in RCA: 123] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Cross-linking of the B cell Ag receptor (BCR) induces the tyrosine phosphorylation of multiple cellular substrates, including phospholipase C (PLC)-gamma 2, which is involved in the activation of the phosphatidylinositol pathway. To assess the importance of PLC-gamma 2 in murine lymphopoiesis, the PLC-gamma 2 gene was inducibly ablated by using IFN-regulated Cre recombinase. Mice with a neonatally induced loss of PLC-gamma 2 function displayed reduced numbers of mature conventional B cells and peritoneal B1 cells and defective responses in vitro to BCR stimulation and in vivo to immunization with thymus-independent type II Ags. In contrast, T cell development and TCR-mediated proliferation were normal. Taken together, PLC-gamma 2 is a critical component of BCR signaling pathways and is required to promote B cell development.
Collapse
Affiliation(s)
- A Hashimoto
- Department of Molecular Genetics, Institute for Liver Research, Kansai Medical University, Moriguchi, Japan
| | | | | | | | | | | | | | | | | |
Collapse
|
117
|
Affiliation(s)
- D A Fruman
- Department of Molecular Biology and Biochemistry, University of California, Irvine, 92697, USA
| | | | | |
Collapse
|