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Tsubata T. Siglec cis-ligands and their roles in the immune system. Glycobiology 2023; 33:532-544. [PMID: 37154567 DOI: 10.1093/glycob/cwad038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Revised: 04/14/2023] [Indexed: 05/10/2023] Open
Abstract
Sialic acid-binding immunoglobulin-like lectins are a family of membrane molecules primarily expressed in immune cells. Most of them are inhibitory receptors containing immunoreceptor tyrosine-based inhibition motifs in the cytoplasmic tail. On the cell surface, sialic acid-binding immunoglobulin-like lectins are mostly bound by sialylated glycans on membrane molecules expressed in the same cell (cis-ligands). Although ligands of sialic acid-binding immunoglobulin-like lectins are not efficiently identified by conventional methods such as immunoprecipitation, in situ labeling including proximity labeling is useful in identifying both cis-ligands and the sialylated ligands expressed by other cells (trans-ligands) of sialic acid-binding immunoglobulin-like lectins. Interaction of the inhibitory sialic acid-binding immunoglobulin-like lectins with cis-ligands including both those with and without signaling function modulates the inhibitory activity of sialic acid-binding immunoglobulin-like lectins by multiple different ways. This interaction also modulates signaling function of the cis-ligands. So far, little is known about the role of the interaction between sialic acid-binding immunoglobulin-like lectins and the cis-ligands. Nonetheless, recent studies showed that the inhibitory activity of CD22 (also known as Siglec-2) is regulated by endogenous ligands, most likely cis-ligands, differentially in resting B cells and those in which B-cell antigen receptor is ligated. This differential regulation plays a role in quality control of signaling-competent B cells and also partial restoration of B-cell antigen receptor signaling in immunodeficient B cells.
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Affiliation(s)
- Takeshi Tsubata
- Department of Pathology, Nihon University School of Dentistry, Tokyo 101-8310, Japan
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Sepehrirad S, Amanlou A, Bagherzadeh K, Azizian H, Amanlou M. Library-based lead compound discovery for CS-1 protein in multiple myeloma: homology modelling, molecular dynamic simulations, virtual screening and molecular docking. MOLECULAR SIMULATION 2021. [DOI: 10.1080/08927022.2021.1971225] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Affiliation(s)
- Shahrzad Sepehrirad
- Tehran University of Medical Sciences, International campus (TUMS-IC), Tehran, Iran
| | - Arash Amanlou
- Faculty of Specialized Veterinary Sciences, Science and Research Branch, Islamic Azad University, Tehran, Iran
- Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran
| | - Kowsar Bagherzadeh
- Stem Cell and Regenerative Medicine Research Center, Iran University of Medical Sciences, Tehran, Iran
- Eye Research Center, The Five Senses Institute, Rasoul Akram Hospital, Iran University of Medical Sciences, Tehran, Iran
| | - Homa Azizian
- Department of Medicinal Chemistry, School of Pharmacy, Iran University of Medical Sciences, Tehran, Iran
| | - Massoud Amanlou
- Experimental Medicine Research Center, Tehran University of Medical Sciences, Tehran, Iran
- Department of Medicinal Chemistry, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran
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Radomir L, Cohen S, Kramer MP, Bakos E, Lewinsky H, Barak A, Porat Z, Bucala R, Stepensky P, Becker-Herman S, Shachar I. T Cells Regulate Peripheral Naive Mature B Cell Survival by Cell-Cell Contact Mediated through SLAMF6 and SAP. THE JOURNAL OF IMMUNOLOGY 2017; 199:2745-2757. [PMID: 28904129 DOI: 10.4049/jimmunol.1700557] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Accepted: 08/10/2017] [Indexed: 11/19/2022]
Abstract
The control of lymphoid homeostasis is the result of a very fine balance between lymphocyte production, proliferation, and apoptosis. In this study, we focused on the role of T cells in the maintenance/survival of the mature naive peripheral B cell population. We show that naive B and T cells interact via the signaling lymphocyte activation molecule (SLAM) family receptor, SLAMF6. This interaction induces cell type-specific signals in both cell types, mediated by the SLAM-associated protein (SAP) family of adaptors. This signaling results in an upregulation of the expression of the cytokine migration inhibitory factor in the T cells and augmented expression of its receptor CD74 on the B cell counterparts, consequently enhancing B cell survival. Furthermore, in X-linked lymphoproliferative disease patients, SAP deficiency reduces CD74 expression, resulting in the perturbation of B cell maintenance from the naive stage. Thus, naive T cells regulate B cell survival in a SLAMF6- and SAP-dependent manner.
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Affiliation(s)
- Lihi Radomir
- Department of Immunology, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Sivan Cohen
- Department of Immunology, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Matthias P Kramer
- Department of Immunology, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Eszter Bakos
- Department of Immunology, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Hadas Lewinsky
- Department of Immunology, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Avital Barak
- Department of Immunology, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Ziv Porat
- Department of Biological Services, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Richard Bucala
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06520; and
| | - Polina Stepensky
- Pediatric Hematology-Oncology and Bone Marrow Transplantation Unit, Hadassah Hebrew University Medical Center, Jerusalem 91120, Israel
| | | | - Idit Shachar
- Department of Immunology, Weizmann Institute of Science, Rehovot 76100, Israel;
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Liñán-Rico L, Hernández-Castro B, Doniz-Padilla L, Portillo-Salazar H, Baranda L, Cruz-Muñoz ME, González-Amaro R. Analysis of expression and function of the co-stimulatory receptor SLAMF1 in immune cells from patients with systemic lupus erythematosus (SLE). Lupus 2015; 24:1184-90. [PMID: 25920347 DOI: 10.1177/0961203315584412] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2014] [Accepted: 03/30/2015] [Indexed: 01/30/2023]
Abstract
The signaling lymphocytic activation molecule SLAMF1 (CD150) is a co-stimulatory molecule that is expressed by most immune cells, including T regulatory (Treg) lymphocytes. Since different abnormalities have been reported regarding the number and function of Foxp3+ Treg cells in patients with systemic lupus erythematosus (SLE), we decided to analyze the expression and function of CD150 in these regulatory lymphocytes in this condition. We isolated peripheral blood mononuclear cells from 20 patients with SLE, and 20 healthy controls. The expression of SLAMF1 was determined by multi-parametric flow cytometry and the suppressive function of CD4+CD25+ lymphocytes, upon engagement or not of CD150 with an agonistic monoclonal antibody, was analyzed by an assay of inhibition of cell proliferation. We observed a significantly increased expression of SLAMF1 by CD3+CD4+ helper T cells and CD19+ B cells in patients with SLE and active disease. However, similar levels of SLAMF1 expression were detected in Foxp3+ Treg cells from patients and controls. In contrast, a higher proportion of SLE patients increased their suppressive function of Treg cells upon CD150 engagement compared to healthy controls. Our data suggest that SLAMF1 is another significant piece in the intricate defective immune-regulatory function of patients with SLE.
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Affiliation(s)
- L Liñán-Rico
- Department of Immunology, UASLP, San Luis Potosí, Mexico
| | | | - L Doniz-Padilla
- Unidad Académica Multidisciplinaria Zona Huasteca, UASLP, San Luis Potosí, Mexico
| | - H Portillo-Salazar
- Unidad Académica Multidisciplinaria Zona Huasteca, UASLP, San Luis Potosí, Mexico
| | - L Baranda
- Department of Immunology, UASLP, San Luis Potosí, Mexico Regional Unit of Rheumatology and Osteoporosis, Hospital Central Dr. Ignacio Morones Prieto, San Luis Potosí, Mexico
| | | | - R González-Amaro
- Department of Immunology, UASLP, San Luis Potosí, Mexico Unidad Académica Multidisciplinaria Zona Huasteca, UASLP, San Luis Potosí, Mexico
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Jukosky J, Gosselin BJ, Foley L, Dechen T, Fiering S, Crane-Godreau MA. In vivo Cigarette Smoke Exposure Decreases CCL20, SLPI, and BD-1 Secretion by Human Primary Nasal Epithelial Cells. Front Psychiatry 2015; 6:185. [PMID: 26793127 PMCID: PMC4710704 DOI: 10.3389/fpsyt.2015.00185] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Accepted: 12/18/2015] [Indexed: 11/30/2022] Open
Abstract
Smokers and individuals exposed to second-hand cigarette smoke have a higher risk of developing chronic sinus and bronchial infections. This suggests that cigarette smoke (CS) has adverse effects on immune defenses against pathogens. Epithelial cells are important in airway innate immunity and are the first line of defense against infection. Airway epithelial cells not only form a physical barrier but also respond to the presence of microbes by secreting antimicrobials, cytokines, and chemokines. These molecules can lyse infectious microorganisms and/or provide signals critical to the initiation of adaptive immune responses. We examined the effects of CS on antimicrobial secretions of primary human nasal epithelial cells (PHNECs). Compared to non-CS-exposed individuals, PHNEC from in vivo CS-exposed individuals secreted less chemokine ligand (C-C motif) 20 (CCL20), Beta-defensin 1 (BD-1), and SLPI apically, less BD-1 and SLPI basolaterally, and more CCL20 basolaterally. Cigarette smoke extract (CSE) exposure in vitro decreased the apical secretion of CCL20 and beta-defensin 1 by PHNEC from non-CS-exposed individuals. Exposing PHNEC from non-CS exposed to CSE also significantly decreased the levels of many mRNA transcripts that are involved in immune signaling. Our results show that in vivo or in vitro exposure to CS alters the secretion of key antimicrobial peptides from PHNEC, but that in vivo CS exposure is a much more important modifier of antimicrobial peptide secretion. Based on the gene expression data, it appears that CSE disrupts multiple immune signaling pathways in PHNEC. Our results provide mechanistic insight into how CS exposure alters the innate immune response and increases an individual's susceptibility to pathogen infection.
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Affiliation(s)
- James Jukosky
- Department of Natural Science, Colby-Sawyer College , New London, NH , USA
| | - Benoit J Gosselin
- Department of Otolaryngology, Dartmouth Hitchcock Medical Center , Lebanon, NH , USA
| | - Leah Foley
- Department of Natural Science, Colby-Sawyer College , New London, NH , USA
| | - Tenzin Dechen
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth , Lebanon, NH , USA
| | - Steven Fiering
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth , Lebanon, NH , USA
| | - Mardi A Crane-Godreau
- Department of Microbiology and Immunology, Geisel School of Medicine at Dartmouth , Lebanon, NH , USA
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Aiello FB, Graciotti L, Procopio AD, Keller JR, Durum SK. Stemness of T cells and the hematopoietic stem cells: fate, memory, niche, cytokines. Cytokine Growth Factor Rev 2013; 24:485-501. [PMID: 24231048 PMCID: PMC6390295 DOI: 10.1016/j.cytogfr.2013.10.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Stem cells are able to generate both cells that differentiate and cells that remain undifferentiated but potentially have the same developmental program. The prolonged duration of the protective immune memory for infectious diseases such as polio, small pox, and measles, suggested that memory T cells may have stem cell properties. Understanding the molecular basis for the life-long persistence of memory T cells may be useful to project targeted therapies for immune deficiencies and infectious diseases and to formulate vaccines. In the last decade evidence from different laboratories shows that memory T cells may share self-renewal pathways with bone marrow hematopoietic stem cells. In stem cells the intrinsic self-renewal activity, which depends on gene expression, is known to be modulated by extrinsic signals from the environment that may be tissue specific. These extrinsic signals for stemness of memory T cells include cytokines such as IL-7 and IL-15 and there are other cytokine signals for maintaining the cytokine signature (TH1, TH2, etc.) of memory T cells. Intrinsic and extrinsic pathways that might be common to bone marrow hematopoietic stem cells and memory T lymphocytes are discussed and related to self-renewal functions.
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Affiliation(s)
- Francesca B Aiello
- Laboratory of Molecular Immunoregulation, Frederick, MD 21702, USA; Department of Medicine and Aging Sciences, University of Chieti-Pescara, 66013 Chieti, Italy.
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Do inhibitory immune receptors play a role in the etiology of autoimmune disease? Clin Immunol 2013; 150:31-42. [PMID: 24333531 DOI: 10.1016/j.clim.2013.11.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2013] [Revised: 11/07/2013] [Accepted: 11/10/2013] [Indexed: 12/21/2022]
Abstract
Inhibitory receptors are thought to be important in balancing immune responses. The general assumption is that lack of inhibition predisposes for autoimmune diseases. As reviewed here, various experimental and clinical data support this assumption. However, in humans genetic evidence implicates only a limited number of inhibitory receptors. GWAS have established common variation in a few inhibitory receptor genes, such as FCγRIIB, PD-1 and CTLA-4 as risk factors. The question arises whether inhibitory receptor function is a major determinant of autoimmune disease. In this respect, the finding that genetic variation in CSK and PTPN22 is strongly associated with multiple autoimmune diseases is of interest. We propose a model in which the molecules encoded by these genes are downstream of inhibitory receptors. We conclude that common genetic variation of inhibitory receptors, with few exceptions, is not a determining factor for autoimmunity in humans. However, common downstream signaling pathways are.
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Youn JI, Collazo M, Shalova IN, Biswas SK, Gabrilovich DI. Characterization of the nature of granulocytic myeloid-derived suppressor cells in tumor-bearing mice. J Leukoc Biol 2011; 91:167-81. [PMID: 21954284 DOI: 10.1189/jlb.0311177] [Citation(s) in RCA: 400] [Impact Index Per Article: 30.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
MDSCs are a group of cells with potent immune-suppressive activity. These cells accumulate in many pathologic conditions and play a major role in the regulation of immune responses. The nature of MDSC remains highly debatable. In cancer, most MDSCs are represented by cells with granulocytic phenotype and morphology, G-MDSC. The relationship between G-MDSCs and Neu remains unclear. In this study, we have found that G-MDSCs, from tumor-bearing, and Neu, from tumor-free, mice share a common morphology and phenotype. However, in contrast to Neu, a substantial proportion of G-MDSCs expressed M-CSFR and a CD244 molecule. Neu had significantly higher phagocytic activity, expression of lysosomal proteins, and TNF-α than corresponding G-MDSCs, which had significantly higher activity of arginase, MPO, and ROS. In contrast to G-MDSC, neither rested nor mobilized Neu suppressed T cells. G-MDSC survived 2 days in culture in the presence of GM-CSF and within 24 h, became phenotypic and functionally similar to Neu. Tumor-associated G-MDSC shared most characteristics of splenic G-MDSC, rather then Neu. These data suggest that in cancer, despite morphological and phenotypic similarities, G-MDSCs are functionally distinct from Neu and are comprised of pathologically activated precursors of Neu.
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Affiliation(s)
- Je-In Youn
- H. Lee Moffitt Cancer Center, Tampa, Florida 33612, USA
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Engel P, Pérez-Carmona N, Albà MM, Robertson K, Ghazal P, Angulo A. Human cytomegalovirus UL7, a homologue of the SLAM-family receptor CD229, impairs cytokine production. Immunol Cell Biol 2011; 89:753-66. [PMID: 21670740 DOI: 10.1038/icb.2011.55] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Human cytomegalovirus (HCMV), the β-herpesvirus prototype, has evolved a wide spectrum of mechanisms to counteract host immunity. Among them, HCMV uses cellular captured genes encoding molecules capable of interfering with the original host function or of fulfilling new immunomodulatory tasks. Here, we report on UL7, a novel HCMV heavily glycosylated transmembrane protein, containing an Ig-like domain that exhibits remarkable amino acid similarity to CD229, a cell-surface molecule of the signalling lymphocyte-activation molecule (SLAM) family involved in leukocyte activation. The UL7 Ig-like domain, which is well-preserved in all HCMV strains, structurally resembles the SLAM-family N-terminal Ig-variable domain responsible for the homophilic and heterophilic interactions that trigger signalling. UL7 is transcribed with early-late kinetics during the lytic infectious cycle. Using a mAb generated against the viral protein, we show that it is constitutively shed, through its mucine-like stalk, from the cell-surface. Production of soluble UL7 is enhanced by PMA and reduced by a broad-spectrum metalloproteinase inhibitor. Although UL7 does not hold the ability to interact with CD229 or other SLAM-family members, it shares with them the capacity to mediate adhesion to leukocytes, specifically to monocyte-derived DCs. Furthermore, we demonstrate that UL7 expression attenuates the production of proinflammatory cytokines TNF, IL-8 and IL-6 in DCs and myeloid cell lines. Thus, the ability of UL7 to interfere with cellular proinflammatory responses may contribute to viral persistence. These results enhance our understanding of those HCMV-encoded molecules involved in sustaining the balance between HCMV and the host immune system.
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Affiliation(s)
- Pablo Engel
- Department of Cell Biology, Immunology, and Neurosciences, Medical School, University of Barcelona, Barcelona, Spain
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10
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The SLAM family member CD48 (Slamf2) protects lupus-prone mice from autoimmune nephritis. J Autoimmun 2011; 37:48-57. [PMID: 21561736 DOI: 10.1016/j.jaut.2011.03.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2011] [Revised: 03/28/2011] [Accepted: 03/29/2011] [Indexed: 12/27/2022]
Abstract
Polymorphisms in the SLAM family of leukocyte cell surface regulatory molecules have been associated with lupus-like phenotypes in both humans and mice. The murine Slamf gene cluster lies within the lupus-associated Sle1b region of mouse chromosome 1. Non-autoreactive C57BL/6 (B6) mice that have had this region replaced by syntenic segments from other mouse strains (i.e. 129, NZB and NZW) are B6 congenic strains that spontaneously produce non-nephritogenic lupus-like autoantibodies. We have recently reported that genetic ablation of the SLAM family member CD48 (Slamf2) drives full-blown autoimmune disease with severe proliferative glomerulonephritis (CD48GN) in B6 mice carrying 129 sequences of the Sle1b region (B6.129CD48(-/-)). We also discovered that BALB/c mice with the same 129-derived CD48-null allele (BALB.129CD48(-/-)) have neither nephritis nor anti-DNA autoantibodies, indicating that strain specific background genes modulate the effects of CD48 deficiency. Here we further examine this novel model of lupus nephritis in which CD48 deficiency transforms benign autoreactivity into fatal nephritis. CD48GN is characterized by glomerular hypertrophy with mesangial expansion, proliferation and leukocytic infiltration. Immune complexes deposit in mesangium and in sub-endothelial, sub-epithelial and intramembranous sites along the glomerular basement membrane. Afflicted mice have low-grade proteinuria, intermittent hematuria and their progressive renal injury manifests with elevated urine NGAL levels and with uremia. In contrast to the lupus-like B6.129CD48(-/-) animals, neither BALB.129CD48(-/-) mice nor B6 × BALB/c F1.129CD48(-/-) progeny have autoimmune traits, indicating that B6-specific background genes modulate the effect of CD48 on lupus nephritis in a recessive manner.
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Abstract
Cell contact-dependent inhibition and regulation of immune responses play an essential role in balancing the need for rapid and efficient responses to a wide variety of pathological challenges, while at the same time maintaining self-tolerance. Much attention has been given to immune synapses that lead to the activation of, for example, cell-mediated cytotoxicity, and here we compare the supramolecular dynamics of synapses that lead to inhibition or regulatory functions. We focus on natural killer cells where such different synapses have been best studied. An emergent principle is that inhibition or regulatory responses are commonly achieved by selective recruitment of signalling proteins to the synapse and exclusion of membrane-proximal intracellular proteins needed for activation. We also discuss evidence that an inhibitory synapse triggers or maintains effector cells in a migratory configuration, which serves to break the synapse before the steps needed for effector cell activation can be completed. This model implies that the concept of kinetic-proofreading, previously used to describe activation of individual T-cell receptors, can also apply in determining the outcome of intercellular conjugation.
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Masilamani M, Peruzzi G, Borrego F, Coligan JE. Endocytosis and intracellular trafficking of human natural killer cell receptors. Traffic 2009; 10:1735-44. [PMID: 19719476 DOI: 10.1111/j.1600-0854.2009.00973.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Natural killer (NK) cells play a vital role in the defense against viral infections and tumor development. NK cell function is primarily regulated by the sum of signals from a broad array of activation and inhibitory receptors. Key to generating the input level of either activating or inhibitory signals is the maintenance of receptor expression levels on the cell surface. Although the mechanisms of endocytosis and trafficking for some cell surface receptors, such as transferrin receptor and certain immune receptors, are very well known, that is not the situation for receptors expressed by NK cells. Recent studies have uncovered that endocytosis and trafficking routes characteristic for specific activation and inhibitory receptors can regulate the functional responses of NK cells. In this review, we summarize the current knowledge of receptor endocytosis and trafficking, and integrate this with our current understanding of NK cell receptor trafficking.
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Affiliation(s)
- Madhan Masilamani
- The Jaffe Food Allergy Institute, Department of Pediatrics, Mount Sinai School of Medicine, One Gustave L Levy Place, New York, NY 10029, USA.
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Kochi Y, Suzuki A, Yamada R, Yamamoto K. Genetics of rheumatoid arthritis: Underlying evidence of ethnic differences. J Autoimmun 2009; 32:158-62. [DOI: 10.1016/j.jaut.2009.02.020] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2009] [Accepted: 02/11/2009] [Indexed: 11/30/2022]
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Abstract
Hematopoiesis is a carefully controlled process that is regulated by complex networks of transcription factors that are, in part, controlled by signals resulting from ligand binding to cell-surface receptors. To further understand hematopoiesis, we have compared gene expression profiles of human erythroblasts, megakaryocytes, B cells, cytotoxic and helper T cells, natural killer cells, granulocytes, and monocytes using whole genome microarrays. A bioinformatics analysis of these data was performed focusing on transcription factors, immunoglobulin superfamily members, and lineage-specific transcripts. We observed that the numbers of lineage-specific genes varies by 2 orders of magnitude, ranging from 5 for cytotoxic T cells to 878 for granulocytes. In addition, we have identified novel coexpression patterns for key transcription factors involved in hematopoiesis (eg, GATA3-GFI1 and GATA2-KLF1). This study represents the most comprehensive analysis of gene expression in hematopoietic cells to date and has identified genes that play key roles in lineage commitment and cell function. The data, which are freely accessible, will be invaluable for future studies on hematopoiesis and the role of specific genes and will also aid the understanding of the recent genome-wide association studies.
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CS1 promotes multiple myeloma cell adhesion, clonogenic growth, and tumorigenicity via c-maf-mediated interactions with bone marrow stromal cells. Blood 2009; 113:4309-18. [PMID: 19196658 DOI: 10.1182/blood-2008-10-183772] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
CS1 is highly expressed on tumor cells from the majority of multiple myeloma (MM) patients regardless of cytogenetic abnormalities or response to current treatments. Furthermore, CS1 is detected in MM patient sera and correlates with active disease. However, its contribution to MM pathophysiology is undefined. We here show that CS1 knockdown using lentiviral short-interfering RNA decreased phosphorylation of ERK1/2, AKT, and STAT3, suggesting that CS1 induces central growth and survival signaling pathways in MM cells. Serum deprivation markedly blocked survival at earlier time points in CS1 knockdown compared with control MM cells, associated with earlier activation of caspases, poly(ADP-ribose) polymerase, and proapoptotic proteins BNIP3 and BIK. CS1 knockdown further delayed development of MM tumor and prolonged survival in mice. Conversely, CS1 overexpression promoted myeloma cell growth and survival by significantly increasing myeloma adhesion to bone marrow stromal cells (BMSCs) and enhancing myeloma colony formation in semisolid culture. Moreover, CS1 increased c-maf-targeted cyclin D2-dependent proliferation, -integrin beta7/alphaE-mediated myeloma adhesion to BMSCs, and -vascular endothelial growth factor-induced bone marrow angiogenesis in vivo. These studies provide direct evidence of the role of CS1 in myeloma pathogenesis, define molecular mechanisms regulating its effects, and further support novel therapies targeting CS1 in MM.
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Hsi ED, Steinle R, Balasa B, Szmania S, Draksharapu A, Shum BP, Huseni M, Powers D, Nanisetti A, Zhang Y, Rice AG, van Abbema A, Wong M, Liu G, Zhan F, Dillon M, Chen S, Rhodes S, Fuh F, Tsurushita N, Kumar S, Vexler V, Shaughnessy JD, Barlogie B, van Rhee F, Hussein M, Afar DEH, Williams MB. CS1, a potential new therapeutic antibody target for the treatment of multiple myeloma. Clin Cancer Res 2008; 14:2775-84. [PMID: 18451245 DOI: 10.1158/1078-0432.ccr-07-4246] [Citation(s) in RCA: 428] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
PURPOSE We generated a humanized antibody, HuLuc63, which specifically targets CS1 (CCND3 subset 1, CRACC, and SLAMF7), a cell surface glycoprotein not previously associated with multiple myeloma. To explore the therapeutic potential of HuLuc63 in multiple myeloma, we examined in detail the expression profile of CS1, the binding properties of HuLuc63 to normal and malignant cells, and the antimyeloma activity of HuLuc63 in preclinical models. EXPERIMENTAL DESIGN CS1 was analyzed by gene expression profiling and immunohistochemistry of multiple myeloma samples and numerous normal tissues. HuLuc63-mediated antimyeloma activity was tested in vitro in antibody-dependent cellular cytotoxicity (ADCC) assays and in vivo using the human OPM2 xenograft model in mice. RESULTS CS1 mRNA was expressed in >90% of 532 multiple myeloma cases, regardless of cytogenetic abnormalities. Anti-CS1 antibody staining of tissues showed strong staining of myeloma cells in all plasmacytomas and bone marrow biopsies. Flow cytometric analysis of patient samples using HuLuc63 showed specific staining of CD138+ myeloma cells, natural killer (NK), NK-like T cells, and CD8+ T cells, with no binding detected on hematopoietic CD34+ stem cells. HuLuc63 exhibited significant in vitro ADCC using primary myeloma cells as targets and both allogeneic and autologous NK cells as effectors. HuLuc63 exerted significant in vivo antitumor activity, which depended on efficient Fc-CD16 interaction as well as the presence of NK cells in the mice. CONCLUSIONS These results suggest that HuLuc63 eliminates myeloma cells, at least in part, via NK-mediated ADCC and shows the therapeutic potential of targeting CS1 with HuLuc63 for the treatment of multiple myeloma.
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Affiliation(s)
- Eric D Hsi
- Clinical Pathology, Cleveland Clinic Foundation, Cleveland, Ohio, USA
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Naschberger E, Croner RS, Merkel S, Dimmler A, Tripal P, Amann KU, Kremmer E, Brueckl WM, Papadopoulos T, Hohenadl C, Hohenberger W, Stürzl M. Angiostatic immune reaction in colorectal carcinoma: Impact on survival and perspectives for antiangiogenic therapy. Int J Cancer 2008; 123:2120-9. [PMID: 18697200 DOI: 10.1002/ijc.23764] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Angiogenesis and inflammation are the 2 major stroma reactions in colorectal carcinoma (CRC). Guanylate binding protein-1 (GBP-1) is a key mediator of angiostatic effects of inflammation. Therefore, we hypothesized that GBP-1 may be a biomarker of intrinsic angiostasis associated with an improved outcome in CRC patients. GBP-1 was strongly expressed in endothelial cells and immune cells in the desmoplastic stroma of 32% of CRC as determined by immunohistochemical investigation of 388 sporadic CRC. Cancer-related 5-year survival was highly significant (p < 0.001) increased (16.2%) in patients with GBP-1-positive CRC. Multivariate analysis showed that GBP-1 is an independent prognostic factor indicating a reduction of the relative risk of cancer-related death by the half (p = 0.032). A comparative transcriptome analysis (22,215 probe sets) of GBP-1-positive (n = 12) and -negative (n = 12) tumors showed that particularly IFN-gamma-induced genes including the major antiangiogenic chemokines CXCL9, CXCL10 and CXCL11 were coexpressed with GBP-1. Altogether our findings indicated that GBP-1 may be a novel biomarker and an active component of a Th-1-like angiostatic immune reaction in CRC. This reaction may affect patient's response to antiangiogenic therapy and the identification of such tumors may provide a novel criterion for patient selection. Moreover, the induction of a Th-1-like angiostatic immune reaction may be a promising approach for the clinical treatment of CRC.
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Affiliation(s)
- Elisabeth Naschberger
- Division of Molecular and Experimental Surgery, Department of Surgery, University of Erlangen-Nuremberg, Schwabachanlage 10, Erlangen, Germany
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18
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Saborit-Villarroya I, Martinez-Barriocanal A, Oliver-Vila I, Engel P, Sayos J, Martin M. The adaptor 3BP2 activates CD244-mediated cytotoxicity in PKC- and SAP-dependent mechanisms. Mol Immunol 2008; 45:3446-53. [PMID: 18479751 DOI: 10.1016/j.molimm.2008.03.021] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2008] [Revised: 03/25/2008] [Accepted: 03/31/2008] [Indexed: 11/27/2022]
Abstract
Natural killer (NK) cell cytotoxicity requires triggering of activation receptors over inhibitory receptors. CD244, a member of CD150 receptor family, positively regulates NK-mediated lyses by activating an intracellular multiproteic signaling network that involves the adaptors X-linked lymphoproliferative gene product SAP and 3BP2. However, the exact mechanisms used by 3BP2 to enhance CD244-mediated cytotoxicity are still not fully understood. Here using the human NK cell line YT-overexpressing 3BP2, we found that the adaptor increases CD244, PI3K, and Vav phosphorylation upon CD244 engagement. The use of enzymatic inhibitors revealed that 3BP2-dependent cytolysis enhancement was PKC-dependent and PI3K-ERK independent. Furthermore, 3BP2 overexpression enhanced PKC delta phosphorylation. SAP knockdown expression inhibited PKC delta activation, indicating that the activating role played by 3BP2 depends upon the presence of SAP. In conclusion, our data show that 3BP2 acts downstream of SAP, increases CD244 phosphorylation and links the receptor with PI3K, Vav, PLC gamma, and PKC downstream events in order to achieve maximum NK killing function.
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Affiliation(s)
- Ifigenia Saborit-Villarroya
- Immunoreceptors group, Institut d'Investigació August Pi i Sunyer (IDIBAPS), Immunology Unit, Department of Cellular Biology and Pathology, Medical School, University of Barcelona, Barcelona, Spain
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19
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Mehrle S, Schmidt J, Büchler MW, Watzl C, Märten A. Enhancement of anti-tumor activity in vitro and in vivo by CD150 and SAP. Mol Immunol 2008; 45:796-804. [PMID: 17692919 DOI: 10.1016/j.molimm.2007.06.361] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2007] [Accepted: 06/04/2007] [Indexed: 11/23/2022]
Abstract
Signaling lymphocyte activation molecule (SLAM, CD150) is a co-stimulatory receptor involved in T cell activation. The activity of CD150 is dependent on the intracellular signaling molecule SAP. Here, we investigated anti-CD3 activated human lymphocytes, transfected either with CD150-plasmid or with CD150- or SAP-siRNA in cytotoxicity assays against human colon cancer cells in vitro and in a xenograft model (CB/Scid/CrL mice) in vivo. Up-regulation or silencing of CD150 was accompanied by increased or decreased cytotoxic activity, respectively. Similar effects could also be shown in an IFN-gamma ELISpot assay. Furthermore, CD150 co-localized after activation with lipid rafts in specific membrane compartments on CD8 T cells. Treatment of xenografted mice with CD150 over-expressing lymphocytes decelerated tumor growth significantly. Lymphocytes were detectable in spleen 18 days after injection and expressed mainly CD8, CD45RO and CD150 above average. In conclusion, over-expression of CD150 in lymphocytes is accompanied with enhanced cytotoxic activity and IFN-gamma secretion in vitro and anti-tumor activity in vivo, whereas silencing of CD150 down-regulates effector functions. Adoptive cell transfer of CD150 over-expressing lymphocytes results in an accumulation of CD8, CD45RO and CD150 cells in tumor and spleen indicating together with the observed CD150 co-localization with lipid rafts that CD150 mediates a Th1 response.
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Affiliation(s)
- Stefan Mehrle
- Department of Surgery, University of Heidelberg, 69120 Heidelberg, Germany
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20
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Li W, Sofi MH, Rietdijk S, Wang N, Terhorst C, Chang CH. The SLAM-associated protein signaling pathway is required for development of CD4+ T cells selected by homotypic thymocyte interaction. Immunity 2008; 27:763-74. [PMID: 18031696 DOI: 10.1016/j.immuni.2007.10.008] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2007] [Revised: 09/11/2007] [Accepted: 10/15/2007] [Indexed: 10/22/2022]
Abstract
MHC class II-expressing double-positive thymocytes induce progression of CD4(+) T cell development as efficiently as cortical thymic epithelial cells do. Because double-positive thymocytes expressing CD1d select natural killer T (NKT) cells, we investigated whether thymocyte-selected CD4(+) (T-CD4) T cells require the same signaling components as NKT cells. Using bone-marrow chimeras, we found that the signaling molecules SAP, Fyn, and PKCtheta were essential for T-CD4 T cell generation, whereas mutations in the Ly108 receptor, interleukin-15 receptor alpha, or the transcription factor T-bet had a marginal effect. Furthermore, SAP was critical for IL-4 production by T-CD4 T cells, but the PKCtheta deficiency did not alter the ability of T-CD4 T cells to produce cytokines. T-bet was necessary to produce the maximum amount of IFN-gamma for CD4(+) T cells regardless of the selection pathway. Thus, in contrast to epithelial cell-selected CD4(+) T cells, the two distinct lineages of T cells selected by thymocytes--i.e., T-CD4 and NKT cells--both utilize the SAP-Fyn-PKCtheta pathway for their development and function.
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Affiliation(s)
- Wei Li
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
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21
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Byrd A, Hoffmann SC, Jarahian M, Momburg F, Watzl C. Expression analysis of the ligands for the Natural Killer cell receptors NKp30 and NKp44. PLoS One 2007; 2:e1339. [PMID: 18092004 PMCID: PMC2129109 DOI: 10.1371/journal.pone.0001339] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2007] [Accepted: 11/26/2007] [Indexed: 01/17/2023] Open
Abstract
Background The natural cytotoxicity receptors (NCR) are important to stimulate the activity of Natural Killer (NK) cells against transformed cells. Identification of NCR ligands and their level of expression on normal and neoplastic cells has important implications for the rational design of immunotherapy strategies for cancer. Methodology/Principal Findings Here we analyze the expression of NKp30 ligand and NKp44 ligand on 30 transformed or non-transformed cell lines of different origin. We find intracellular and surface expression of these two ligands on almost all cell lines tested. Expression of NKp30 and NKp44 ligands was variable and did not correlate with the origin of the cell line. Expression of NKp30 and NKp44 ligand correlated with NKp30 and NKp44-mediated NK cell lysis of tumor cells, respectively. The surface expression of NKp30 ligand and NKp44 ligand was sensitive to trypsin treatment and was reduced in cells arrested in G2/M phase. Conclusion/Significance These data demonstrate the ubiquitous expression of the ligands for NKp30 and NKp44 and give an important insight into the regulation of these ligands.
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Affiliation(s)
- Andreina Byrd
- Institute for Immunology, University Heidelberg, Heidelberg, Germany
| | | | - Mostafa Jarahian
- Department of Molecular Immunology, German Cancer Research Center, Heidelberg, Germany
| | - Frank Momburg
- Department of Molecular Immunology, German Cancer Research Center, Heidelberg, Germany
| | - Carsten Watzl
- Institute for Immunology, University Heidelberg, Heidelberg, Germany
- * To whom correspondence should be addressed. E-mail:
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22
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Hoffmann SC, Schellack C, Textor S, Konold S, Schmitz D, Cerwenka A, Pflanz S, Watzl C. Identification of CLEC12B, an inhibitory receptor on myeloid cells. J Biol Chem 2007; 282:22370-5. [PMID: 17562706 DOI: 10.1074/jbc.m704250200] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Activation of immune cells has to be tightly controlled to prevent detrimental hyperactivation. In this regulatory process molecules of the C-type lectin-like family play a central role. Here we describe a new member of this family, CLEC12B. The extracellular domain of CLEC12B shows considerable homology to the activating natural killer cell receptor NKG2D, but unlike NKG2D, CLEC12B contains an immunoreceptor tyrosine-based inhibition motif in its intracellular domain. Despite the homology, CLEC12B does not appear to bind NKG2D ligands and therefore does not represent the inhibitory counterpart of NKG2D. However, CLEC12B has the ability to counteract NKG2D-mediated signaling, and we show that this function is dependent on the immunoreceptor tyrosine-based inhibition motif and the recruitment of the phosphatases SHP-1 and SHP-2. Using monoclonal anti-CLEC12B antibodies we found de novo expression of this receptor on in vitro generated human macrophages and on the human myelo-monocytic cell line U937 upon phorbol 12-myristate 13-acetate treatment, suggesting that this receptor plays a role in myeloid cell function.
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Affiliation(s)
- Sabrina C Hoffmann
- Institute for Immunology, University of Heidelberg, Im Neuenheimer Feld 305, 69120 Heidelberg, Germany
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23
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Ostrakhovitch EA, Li SSC. The role of SLAM family receptors in immune cell signaling. Biochem Cell Biol 2007; 84:832-43. [PMID: 17215871 DOI: 10.1139/o06-191] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
The signaling lymphocyte-activating molecule (SLAM) family immunoreceptors are expressed in a wide array of immune cells, including both T and B lymphocytes. By virtue of their ability to transduce tyrosine phosphorylation signals through the so-called ITSM (immunoreceptor tyrosine-based switch motif) sequences, they play an important part in regulating both innate and adaptive immune responses. The critical role of the SLAM immunoreceptors in mediating normal immune reactions was highlighted in recent findings that SAP, a SLAM-associated protein, modulates the activities of various immune cells through interactions with different members of the SLAM family expressed in these cells. Importantly, mutations or deletions of the sap gene in humans result in the X-linked lymphoproliferative syndrome. In this review, we summarize current knowledge and survey the latest developments in signal transduction events triggered by the activation of SLAM family receptors in different cell types.
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Affiliation(s)
- Elena A Ostrakhovitch
- Department of Biochemistry, Schulich School of Medicine and Dentistry, University of Western Ontario, London, ON N6A 5C1, Canada
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24
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Sandusky MM, Messmer B, Watzl C. Regulation of 2B4 (CD244)-mediated NK cell activation by ligand-induced receptor modulation. Eur J Immunol 2007; 36:3268-76. [PMID: 17111350 DOI: 10.1002/eji.200636146] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Natural killer (NK) cell activity can be stimulated by different surface receptors. 2B4 is a member of the signaling lymphocyte activation molecule (SLAM)-related receptor family and is important for stimulating human NK cell cytotoxicity and cytokine production. Here we show that stimulation of human NK cells by antibody-mediated 2B4 cross-linking or incubation with target cells expressing the 2B4 ligand CD48 results in a strong down-modulation of 2B4 surface expression. This down-modulation is observed in NK cell lines, purified human NK cells and NK cell clones, and is accompanied by an internalization of 2B4. The modulation of 2B4 is dependent on the activity of Src-family kinases, but independent of PI3 K activity or actin polymerization. Inhibitory receptors can interfere with 2B4-mediated signals and NK cell activation. However, co-engagement of inhibitory killer cell Ig-like receptors has no influence on the down-modulation of 2B4. This suggests that the modulation of 2B4 expression is independent of inhibitory receptors. The lower surface expression of 2B4 after ligand-induced down-modulation results in reduced 2B4-mediated NK cell activation and cytotoxicity. The modulation of activating surface receptors may therefore be another mechanism for the fine-tuning of NK cell activity and may lead to the adaptation of NK cell cytotoxicity in tissues with high ligand expression.
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MESH Headings
- Antigens, CD/biosynthesis
- Antigens, CD/metabolism
- Cell Line
- Cell Membrane/immunology
- Cell Membrane/metabolism
- Cytotoxicity, Immunologic
- Down-Regulation/immunology
- Humans
- Killer Cells, Natural/immunology
- Killer Cells, Natural/metabolism
- Ligands
- Lymphocyte Activation/immunology
- Receptors, Immunologic/antagonists & inhibitors
- Receptors, Immunologic/biosynthesis
- Receptors, Immunologic/metabolism
- Receptors, Immunologic/physiology
- Receptors, KIR
- Signaling Lymphocytic Activation Molecule Family
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Affiliation(s)
- Mina M Sandusky
- Institute for Immunology, University Heidelberg, Heidelberg, Germany
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25
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Endt J, Eissmann P, Hoffmann SC, Meinke S, Giese T, Watzl C. Modulation of 2B4 (CD244) activity and regulated SAP expression in human NK cells. Eur J Immunol 2007; 37:193-8. [PMID: 17171759 DOI: 10.1002/eji.200636341] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The adapter protein SAP is important for the signal transduction of the family of SLAM-related receptors (SRR), which have important immune-modulating functions. The importance of SAP and SRR for a functional immune reaction becomes obvious in patients suffering from X-linked lymphoproliferative disease, which is characterized by non-functional SAP. Here we investigate the regulation of SAP expression in human NK cells. We demonstrate that SAP mRNA expression and protein levels are low in freshly isolated resting NK cells. IL-2 stimulation leads to an up-regulation of SAP expression, which can be enhanced by IL-12, the stimulation of TLR3 by polyinosinic-polycytidylic acid (poly(I:C))and to a lesser extent by IFN-alpha. EAT-2, a SAP-related adapter protein, is already detectable in resting NK cells and does not change its expression after IL-2 stimulation. The regulation of SAP has functional consequences for the stimulation of NK cell cytotoxicity by 2B4. In resting NK cells, 2B4 stimulation can only enhance NK cell lysis when co-triggered with other activating NK cell receptors. In IL-2-activated NK cells with high SAP expression the triggering of 2B4 alone is sufficient to induce NK cell cytotoxicity, demonstrating a correlation between the regulated SAP expression and the function of 2B4.
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MESH Headings
- Antigens, CD/biosynthesis
- Antigens, CD/genetics
- Antigens, CD/metabolism
- Cell Line
- Cells, Cultured
- Cytotoxicity Tests, Immunologic
- Gene Expression Regulation/immunology
- Humans
- Interleukin-2/physiology
- K562 Cells
- Killer Cells, Natural/immunology
- Killer Cells, Natural/metabolism
- Lymphocyte Activation/immunology
- Receptors, Cell Surface/biosynthesis
- Receptors, Cell Surface/genetics
- Receptors, Cell Surface/metabolism
- Receptors, Immunologic/metabolism
- Signaling Lymphocytic Activation Molecule Family
- Signaling Lymphocytic Activation Molecule Family Member 1
- Transfection
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Affiliation(s)
- Johanna Endt
- Institute for Immunology, University Heidelberg, Heidelberg, Germany
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26
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Eissmann P, Watzl C. Molecular Analysis of NTB-A Signaling: A Role for EAT-2 in NTB-A-Mediated Activation of Human NK Cells. THE JOURNAL OF IMMUNOLOGY 2006; 177:3170-7. [PMID: 16920955 DOI: 10.4049/jimmunol.177.5.3170] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Engagement of NTB-A on human NK cells by homophilic interaction with NTB-A-expressing target cells can trigger NK cell cytotoxicity, cytokine production, and proliferation. To better understand how NTB-A can activate NK cells, we analyzed the molecular mechanisms of NTB-A signaling. We show that NTB-A is tyrosine phosphorylated in unstimulated human NK cells and associates with SLAM-associated protein (SAP) and EAT-2. This phosphorylation of NTB-A is mediated by Src family kinases and is most likely a result of the homophilic interaction of NTB-A among neighboring NK cells. Stimulation of NK cells by NTB-A-positive targets results in increased NTB-A phosphorylation. The cytoplasmic tail of NTB-A contains three tyrosines, two of which are embedded within an immunoreceptor tyrosine-based switch motif. We generated a NTB-A-negative NK cell line, in which we expressed different mutants of NTB-A. Functional studies showed that the second tyrosine is sufficient and essential for NTB-A-mediated cytotoxicity. EAT-2, but not SAP, is recruited to this second tyrosine, indicating that SAP may be dispensable for this NTB-A function. To further investigate this, we silenced SAP expression in NK cell lines. Functional analysis of these cells showed that NTB-A can mediate NK cell cytotoxicity in the absence of SAP, probably via EAT-2. In contrast, NTB-A-mediated IFN-gamma production was greatly reduced in the absence of SAP, demonstrating that cytokine production and cytotoxicity are differentially dependent on SAP and possibly EAT-2.
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Affiliation(s)
- Philipp Eissmann
- Institute for Immunology, University Heidelberg, Heidelberg, Germany
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