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Shoshana Levy - One of the best experts on this subject based on the ideXlab platform.
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Tetraspanins regulate the protrusive activities of cell membrane.
Biochemical and Biophysical Research Communications, 2011Co-Authors: Rafijul Bari, Yanhui H. Zhang, Eldon E. Giesert, Shoshana Levy, Jie Zheng, Xin A. ZhangAbstract:Tetraspanins have gained increased attention due to their functional versatility. But the universal cellular mechanism that governs such versatility remains unknown. Herein we present the evidence that tetraspanins CD81 and CD82 regulate the formation and/or development of cell membrane protrusions. We analyzed the ultrastructure of the cells in which a tetraspanin is either overexpressed or ablated using transmission electron microscopy. The numbers of microvilli on the cell surface were counted, and the radii of microvillar tips and the lengths of microvilli were measured. We found that tetraspanin CD81 promotes the microvillus formation and/or extension while tetraspanin CD82 inhibits these events. In addition, CD81 enhances the outward bending of the plasma membrane while CD82 inhibits it. We also found that CD81 and CD82 proteins are localized at microvilli using immunofluorescence. CD82 regulates microvillus morphogenesis likely by altering the plasma membrane curvature and/or the cortical actin cytoskeletal organization. We predict that membrane protrusions embody a common morphological phenotype and cellular mechanism for, at least some if not all, tetraspanins. The differential effects of tetraspanins on microvilli likely lead to the functional diversification of tetraspanins and appear to correlate with their functional propensity.
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Enhanced B cell activation in the absence of CD81.
International immunology, 2009Co-Authors: Mrinmoy Sanyal, Rosemary Fernandez, Shoshana LevyAbstract:CD81 is a component of the CD19/CD21 co-receptor complex in B cells. However, the role of CD81 in B cell activation has not been clearly elucidated. Here, we demonstrate that CD81 -/- B cells stimulated via their B cell receptor fluxed higher intracellular-free calcium ion along with increased phosphorylation of spleen tyrosine kinase and phospholipase gamma 2. Additionally, CD81 -/- B cells responded to toll like receptor 4 stimulation with increased nuclear factor-kappa B activation, cell proliferation and antibody secretion compared with wild-type B cells. CD81 -/- mice also mounted a significantly higher immune response to T-independent antigens than their wild-type counterparts. Finally, analysis of CD81 -/- B cells that were generated by bone marrow transplantation into Rag1 -/- mice confirmed that the hyperactive phenotype is not dependent on the CD81-deficient environment. Taken together, these results indicate that CD81 plays a negative role in B cell activation in vitro and in vivo.
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Critical Role for CD81 in B Cell Activation.
Blood, 2007Co-Authors: Mrinmoy Sanyal, Rosemary Fernandez, Shoshana LevyAbstract:CD81 is a component of the CD19/CD21 signaling complex in B cells. CD81 was originally discovered as target of an anti-proliferative antibody in a human B cell lymphoma. However, the exact role of CD81 in B cell function is not known. Here we studied B cells from CD81 knockout mice. We demonstrate that upon BCR induction these B cells flux higher intracellular free calcium ion; increase the phosphorylation of BCR-related proximal and distal substrates and increase their proliferation. Similarly, polyclonal activation of CD81-deficient B cells with LPS induced increased proliferation and antibody secretion. Consistent with these intrinsic B cell capabilities, CD81-deficient mice mounted significantly higher immune response upon antigenic stimulation. In addition, bone marrow perisinusoidal B cells (IgM+IgD+) capable of mounting T-independent immune responses against blood-borne pathogens were over represented in CD81-deficient mice. These cells also displayed increased calcium influx kinetics as splenic B cells and produced higher amounts of antibody after polyclonal stimulation. Taken together, these results suggest that CD81 is involved in suppressing B cell activation.
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Absence of CD81 Paradoxically Results in a Hyper-IgM and IgG Response to T-Independent Antigens.
Blood, 2006Co-Authors: Mrinmoy Sanyal, Tsipi Shoham, Rosemary Fernandez, Shoshana LevyAbstract:Abstract The tetraspanin CD81 is required for numerous biological functions including fertilization, infection, cell migration and cellular interactions in the nervous and immune systems. In B cells CD81 is a component of the CD19/CD21 signaling complex. CD81 was shown to facilitate the redistribution of the B cell receptor (BCR) complex and CD21 into lipid rafts in response to co-engagement, and to modulate BCR signaling. In addition, CD81-deficient mice express low levels of cell surface CD19, thereby potentially altering signaling by the CD19/CD21 co-receptor complex. Interestingly, the onset of CD81 expression coincides with the onset of CD19 expression during B cell development. The foregoing observations suggest that CD81 might reduce the in vivo response of B cells to antigenic stimulation. To test this hypothesis we compared the response of CD81-deficient and wild type mice to T-independent (TNP-LPS) and T-dependent (TNP-KLH) antigens. Surprisingly, CD81-deficient mice mounted significantly higher IgM responses against both types of antigens. Moreover, the IgG response of CD81-deficient mice was stronger and persistent in response to T-independent antigen. We further found that CD81-deficient mice have an increase in bone marrow perisinusoidal B cells (IgM+IgD+). These cells are primarily responsible for mounting T-independent immune responses against blood-borne pathogens. In addition, CD81-deficient spleenic B cells have an intrinsic ability to produce higher amounts of IgM. These surprising results suggest that CD81 is involved in modulating B cell activation, particularly in response to infection.
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the tetraspanin CD81 is necessary for partitioning of coligated cd19 cd21 b cell antigen receptor complexes into signaling active lipid rafts
Journal of Immunology, 2004Co-Authors: Anu Cherukuri, Shoshana Levy, Robert H. Carter, Stephen R. Brooks, Tsipi Shoham, Hae Won T Sohn, Susan K. PierceAbstract:Tetraspanins have been hypothesized to facilitate the organization of functional multimolecular membrane complexes. In B cells the tetraspanin CD81 is a component of the CD19/CD21 complex. When coligated to the B cell Ag receptor (BCR), the CD19/CD21 complex significantly enhances BCR signaling in part by prolonging the association of the BCR with signaling-active lipid rafts. In this study CD81 is shown to associate with lipid rafts upon coligation of the BCR and the CD19/CD21 complex. Using B cells from CD81-deficient mice we demonstrate that in the absence of CD81, coligated BCR and CD19/CD21 complexes fail to partition into lipid rafts and enhance BCR signaling from rafts. Furthermore, a chimeric CD19 protein that associates only weakly if at all with CD81 fails to promote the association of coligated BCR with lipid rafts. The requirement for CD81 to promote lipid raft association may define a novel mechanism by which tetraspanins function as molecular facilitators of signaling receptors.
Eric Rubinstein - One of the best experts on this subject based on the ideXlab platform.
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the tetraspanin CD81 regulates the expression of cd19 during b cell development in a postendoplasmic reticulum compartment
Journal of Immunology, 2003Co-Authors: Tsipi Shoham, Claude Boucheix, Eric Rubinstein, Thomas F Tedder, Ranjani Rajapaksa, Shoshana LevyAbstract:CD81 is a widely expressed tetraspanin that associates in B cells with CD19 in the CD19-CD21-CD81 signaling complex. CD81 is necessary for normal CD19 expression; CD81 −/− B cells express lower levels of CD19, especially CD81 −/− small pre-BII cells, which are almost devoid of surface CD19. The dependence of CD19 expression on CD81 is specific to this particular tetraspanin since cd9 −/− B cells express normal levels of CD19. Furthermore, expression of human CD81 in mouse CD81 −/− B cells restored surface CD19 to normal levels. Quantitative analysis of CD19 mRNA demonstrated normal levels, even in CD81 −/− pre-BII cells. Analysis of CD19 at the protein level identified two CD19 glycoforms in both wild-type and CD81 −/− B cells. The higher M r glycoform is significantly reduced in CD81 −/− B cells and is endoglycosidase H (endo-H) resistant. In contrast, the low M r glycoform is comparably expressed in CD81 −/− and in wild-type B cells and is endo-H sensitive. Because endo-H sensitivity is tightly correlated with endoplasmic reticulum localization, we suggest that the dependency of CD19 expression on CD81 occurs in a postendoplasmic reticulum compartment where CD81 is necessary for normal trafficking or for surface membrane stability of CD19.
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CD19 Is Linked to the Integrin-associated Tetraspans CD9, CD81, and CD82
The Journal of biological chemistry, 1998Co-Authors: György Horváth, Valérie Serru, Denis Clay, Martine Billard, Claude Boucheix, Eric RubinsteinAbstract:The CD19-CD21-CD81 complex regulates signal transduction events critical for B lymphocyte development and humoral immunity. CD81, a molecule with 4 transmembrane domains, member of the tetraspan superfamily, is engaged, together with other tetraspans such as CD9, CD53, CD63, and CD82, in multimolecular complexes containing beta1 integrins and major histocompatibility complex antigens. Here we demonstrate that two other tetraspans, CD82 and the early B cell marker CD9, are coimmunoprecipitated with CD19 from Brij97 lysates of B cell lines. Moreover, CD9 was coprecipitated from lysates of purified CD10(+) early B cells. These associations were confirmed by the cocapping of CD19 with CD9 or CD82. The CD9/CD19 association was disrupted in the presence of digitonin, contrary to the CD81/CD19 association, indicating that CD9 and CD81 interact with CD19 in different ways. The CD9/CD81 association is also disrupted in the presence of digitonin, suggesting that CD9 associates with CD19 only through CD81. To characterize the regions involved in the CD81/CD19 association, two reciprocal CD9/CD81 chimeric molecules were tested for the association with CD19, but none of them could be coprecipitated with CD19 in digitonin, indicating that the domain of CD81 responsible for its association with CD19 is complex. Finally, engagement of CD9 could induce the tyrosine phosphorylation of different proteins, including CD19 itself, suggesting that the CD9/CD19 association is functionally relevant. Thus, a physical and functional link is formed between the CD19-CD21-CD81 complex and the integrin-tetraspan complexes, which is dynamically modulated in the process of B cell differentiation.
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functional analysis of four tetraspans cd9 cd53 CD81 and cd82 suggests a common role in costimulation cell adhesion and migration only cd9 upregulates hb egf activity
Cellular Immunology, 1997Co-Authors: Cecile Lagaudrieregesbert, Martine Billard, Claude Boucheix, Francois Le Naour, Helene Conjeaud, Sophie Lebelbinay, Emmanuel Lemichez, Patrice Boquet, Eric RubinsteinAbstract:Abstract Molecules of the tetraspan superfamily are engaged in multimolecular complexes containing other proteins such as β1 integrins and MHC antigens. Although their functions are not clear, they have been suggested to play a role in cell adhesion and migration, signal transduction, and costimulation We have in this paper directly compared the functional properties of four tetraspans, CD9, CD53, CD81, and CD82. mAbs to any of these molecules were able to deliver a costimulatory signal for CD3-mediated activation of the T cell line Jurkat. CD82 mAbs were the most efficient in triggering this effect. Moreover, engagement of CD9, CD81, and CD82 induced the homotypic agregation of the megakaryocytic cell line HEL, and inhibited the migration of this cell line. Similar results were obtained with the preB cell line NALM-6 using the CD9 and CD81 mAbs. The CD81 mAb 5A6 produced the strongest effects. Therefore, the tetraspans are recognized by mAbs which produce similar effects on the same cell lines. This is consistent with the tetraspans being included in large molecular complexes and possibly forming a tetraspan network (the tetraspan web). We also demonstrate that the tetraspans are likely to keep specific functional properties inside this network. Indeed, we have demonstrated that the human CD9 is able, like the monkey molecule, to upregulate the activity of the transmembrane precursor of heparin-binding EGF as a receptor for the diphtheria toxin when cotransfected in murine LM cells. Neither CD81, nor CD82 had such activity. By using chimeric CD9/CD81 molecules we demonstrate that this activity requires the second half of CD9, which contains the large extracellular loop, the fourth transmembrane region, and the last short cytoplasmic domain.
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cd9 cd63 CD81 and cd82 are components of a surface tetraspan network connected to hla dr and vla integrins
European Journal of Immunology, 1996Co-Authors: Eric Rubinstein, Martine Billard, Francois Le Naour, Cecile Lagaudrieregesbert, Helene Conjeaud, Claude BoucheixAbstract:CD9, CD63, CD81, and CD82 are glycoproteins of unknown function which belong to the tetraspan superfamily. These molecules have short cytoplasmic sequences, four transmembrane domains and two unequal extracellular regions. Here, we show that these molecules are associated with each other on cell surface and with other glycoproteins such as very late antigen (VLA) integrins and HLA-DR antigens. Moreover, the VLA integrins and HLA-DR antigens were also found to be associated. The interactions of these molecules were analyzed by transfection experiments. It is demonstrated that overexpression of CD9 antigen in Raji cells leads to a lower efficiency of precipitation of CD81 and CD82, suggesting a direct interaction between these molecules. In these cells, the coprecipitation of CD81 and CD82 was not modified, suggesting that these tetraspans did not compete for association. However, in COS-7 cells, transfection of both CD81 and CD82 led to a marked reduction of the number of CD9/CD81 or CD9/CD82 complexes compared to single-transfected cells, and this was associated with the appearance of CD81/CD82 complexes. Therefore, in this cellular system, CD9 competes with CD81 and CD82 for association with the other tetraspan proteins. Finally, the tetraspans do not compete for the association with integrins or HLA-DR. Indeed, when CD9 was expressed in Raji cells, it was incorporated into the pre-existing complexes of these molecules with CD81 and CD82. These data suggest the existence of a tetraspan network which, by connecting several molecules, may organize the positioning of cell surface proteins and play a role in signal transduction, cell adhesion, and motility.
Claude Boucheix - One of the best experts on this subject based on the ideXlab platform.
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the tetraspanin CD81 regulates the expression of cd19 during b cell development in a postendoplasmic reticulum compartment
Journal of Immunology, 2003Co-Authors: Tsipi Shoham, Claude Boucheix, Eric Rubinstein, Thomas F Tedder, Ranjani Rajapaksa, Shoshana LevyAbstract:CD81 is a widely expressed tetraspanin that associates in B cells with CD19 in the CD19-CD21-CD81 signaling complex. CD81 is necessary for normal CD19 expression; CD81 −/− B cells express lower levels of CD19, especially CD81 −/− small pre-BII cells, which are almost devoid of surface CD19. The dependence of CD19 expression on CD81 is specific to this particular tetraspanin since cd9 −/− B cells express normal levels of CD19. Furthermore, expression of human CD81 in mouse CD81 −/− B cells restored surface CD19 to normal levels. Quantitative analysis of CD19 mRNA demonstrated normal levels, even in CD81 −/− pre-BII cells. Analysis of CD19 at the protein level identified two CD19 glycoforms in both wild-type and CD81 −/− B cells. The higher M r glycoform is significantly reduced in CD81 −/− B cells and is endoglycosidase H (endo-H) resistant. In contrast, the low M r glycoform is comparably expressed in CD81 −/− and in wild-type B cells and is endo-H sensitive. Because endo-H sensitivity is tightly correlated with endoplasmic reticulum localization, we suggest that the dependency of CD19 expression on CD81 occurs in a postendoplasmic reticulum compartment where CD81 is necessary for normal trafficking or for surface membrane stability of CD19.
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CD19 Is Linked to the Integrin-associated Tetraspans CD9, CD81, and CD82
The Journal of biological chemistry, 1998Co-Authors: György Horváth, Valérie Serru, Denis Clay, Martine Billard, Claude Boucheix, Eric RubinsteinAbstract:The CD19-CD21-CD81 complex regulates signal transduction events critical for B lymphocyte development and humoral immunity. CD81, a molecule with 4 transmembrane domains, member of the tetraspan superfamily, is engaged, together with other tetraspans such as CD9, CD53, CD63, and CD82, in multimolecular complexes containing beta1 integrins and major histocompatibility complex antigens. Here we demonstrate that two other tetraspans, CD82 and the early B cell marker CD9, are coimmunoprecipitated with CD19 from Brij97 lysates of B cell lines. Moreover, CD9 was coprecipitated from lysates of purified CD10(+) early B cells. These associations were confirmed by the cocapping of CD19 with CD9 or CD82. The CD9/CD19 association was disrupted in the presence of digitonin, contrary to the CD81/CD19 association, indicating that CD9 and CD81 interact with CD19 in different ways. The CD9/CD81 association is also disrupted in the presence of digitonin, suggesting that CD9 associates with CD19 only through CD81. To characterize the regions involved in the CD81/CD19 association, two reciprocal CD9/CD81 chimeric molecules were tested for the association with CD19, but none of them could be coprecipitated with CD19 in digitonin, indicating that the domain of CD81 responsible for its association with CD19 is complex. Finally, engagement of CD9 could induce the tyrosine phosphorylation of different proteins, including CD19 itself, suggesting that the CD9/CD19 association is functionally relevant. Thus, a physical and functional link is formed between the CD19-CD21-CD81 complex and the integrin-tetraspan complexes, which is dynamically modulated in the process of B cell differentiation.
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functional analysis of four tetraspans cd9 cd53 CD81 and cd82 suggests a common role in costimulation cell adhesion and migration only cd9 upregulates hb egf activity
Cellular Immunology, 1997Co-Authors: Cecile Lagaudrieregesbert, Martine Billard, Claude Boucheix, Francois Le Naour, Helene Conjeaud, Sophie Lebelbinay, Emmanuel Lemichez, Patrice Boquet, Eric RubinsteinAbstract:Abstract Molecules of the tetraspan superfamily are engaged in multimolecular complexes containing other proteins such as β1 integrins and MHC antigens. Although their functions are not clear, they have been suggested to play a role in cell adhesion and migration, signal transduction, and costimulation We have in this paper directly compared the functional properties of four tetraspans, CD9, CD53, CD81, and CD82. mAbs to any of these molecules were able to deliver a costimulatory signal for CD3-mediated activation of the T cell line Jurkat. CD82 mAbs were the most efficient in triggering this effect. Moreover, engagement of CD9, CD81, and CD82 induced the homotypic agregation of the megakaryocytic cell line HEL, and inhibited the migration of this cell line. Similar results were obtained with the preB cell line NALM-6 using the CD9 and CD81 mAbs. The CD81 mAb 5A6 produced the strongest effects. Therefore, the tetraspans are recognized by mAbs which produce similar effects on the same cell lines. This is consistent with the tetraspans being included in large molecular complexes and possibly forming a tetraspan network (the tetraspan web). We also demonstrate that the tetraspans are likely to keep specific functional properties inside this network. Indeed, we have demonstrated that the human CD9 is able, like the monkey molecule, to upregulate the activity of the transmembrane precursor of heparin-binding EGF as a receptor for the diphtheria toxin when cotransfected in murine LM cells. Neither CD81, nor CD82 had such activity. By using chimeric CD9/CD81 molecules we demonstrate that this activity requires the second half of CD9, which contains the large extracellular loop, the fourth transmembrane region, and the last short cytoplasmic domain.
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cd9 cd63 CD81 and cd82 are components of a surface tetraspan network connected to hla dr and vla integrins
European Journal of Immunology, 1996Co-Authors: Eric Rubinstein, Martine Billard, Francois Le Naour, Cecile Lagaudrieregesbert, Helene Conjeaud, Claude BoucheixAbstract:CD9, CD63, CD81, and CD82 are glycoproteins of unknown function which belong to the tetraspan superfamily. These molecules have short cytoplasmic sequences, four transmembrane domains and two unequal extracellular regions. Here, we show that these molecules are associated with each other on cell surface and with other glycoproteins such as very late antigen (VLA) integrins and HLA-DR antigens. Moreover, the VLA integrins and HLA-DR antigens were also found to be associated. The interactions of these molecules were analyzed by transfection experiments. It is demonstrated that overexpression of CD9 antigen in Raji cells leads to a lower efficiency of precipitation of CD81 and CD82, suggesting a direct interaction between these molecules. In these cells, the coprecipitation of CD81 and CD82 was not modified, suggesting that these tetraspans did not compete for association. However, in COS-7 cells, transfection of both CD81 and CD82 led to a marked reduction of the number of CD9/CD81 or CD9/CD82 complexes compared to single-transfected cells, and this was associated with the appearance of CD81/CD82 complexes. Therefore, in this cellular system, CD9 competes with CD81 and CD82 for association with the other tetraspan proteins. Finally, the tetraspans do not compete for the association with integrins or HLA-DR. Indeed, when CD9 was expressed in Raji cells, it was incorporated into the pre-existing complexes of these molecules with CD81 and CD82. These data suggest the existence of a tetraspan network which, by connecting several molecules, may organize the positioning of cell surface proteins and play a role in signal transduction, cell adhesion, and motility.
Holden T Maecker - One of the best experts on this subject based on the ideXlab platform.
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CD81 tapa 1 a molecule involved in signal transduction and cell adhesion in the immune system
Annual Review of Immunology, 1998Co-Authors: Shoshana Levy, Scott C Todd, Holden T MaeckerAbstract:▪ Abstract CD81 (TAPA-1) is a widely expressed cell-surface protein involved in an astonishing variety of biologic responses. It has been cloned independently several times for different functional effects and is reported to influence adhesion, morphology, activation, proliferation, and differentiation of B, T, and other cells. On B cells CD81 is part of a complex with CD21, CD19, and Leu13. This complex reduces the threshold for B cell activation via the B cell receptor by bridging Ag specific recognition and CD21-mediated complement recognition. Similarly on T cells CD81 associates with CD4 and CD8 and provides a costimulatory signal with CD3. In fetal thymic organ culture, mAb to CD81 block maturation of CD4−CD8− thymocytes, and expression of CD81 on CHO cells endows those cells with the ability to support T cell maturation. However, CD81-deficient mice express normal numbers and subsets of T cells. These mice do exhibit diminished antibody responses to protein antigens. CD81 is also physically and fun...
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normal lymphocyte development but delayed humoral immune response in CD81 null mice
Journal of Experimental Medicine, 1997Co-Authors: Holden T Maecker, Shoshana LevyAbstract:CD81 is a cell surface molecule expressed on many cell types and associated with the CD19/ CD21/Leu13 signal-transducing complex on B cells. A recent report implies that CD81 expression on thymic stromal cells is important in the maturation of thymocytes from CD4− CD8− to CD4+CD8+. However, we have produced CD81-null mice by gene targeting, and find that they undergo normal development of thymocytes and express normal numbers of T cells. B cells are also found in normal numbers in the spleen, blood, and peritoneal cavity of CD81-null mice, but they express a lower level of CD19 compared to heterozygous littermates. Finally, early antibody responses to the protein antigen ovalbumin are weaker in CD81null mice compared to their heterozygous littermates. This is consistent with the proposed role of the CD19/CD21/CD81-signaling complex in lowering the threshold for B cell responses. These results show that CD81 is not required for maturation of T cells, but is important for optimal expression of CD19 on B cells and optimal stimulation of antibody production.
Martine Billard - One of the best experts on this subject based on the ideXlab platform.
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CD19 Is Linked to the Integrin-associated Tetraspans CD9, CD81, and CD82
The Journal of biological chemistry, 1998Co-Authors: György Horváth, Valérie Serru, Denis Clay, Martine Billard, Claude Boucheix, Eric RubinsteinAbstract:The CD19-CD21-CD81 complex regulates signal transduction events critical for B lymphocyte development and humoral immunity. CD81, a molecule with 4 transmembrane domains, member of the tetraspan superfamily, is engaged, together with other tetraspans such as CD9, CD53, CD63, and CD82, in multimolecular complexes containing beta1 integrins and major histocompatibility complex antigens. Here we demonstrate that two other tetraspans, CD82 and the early B cell marker CD9, are coimmunoprecipitated with CD19 from Brij97 lysates of B cell lines. Moreover, CD9 was coprecipitated from lysates of purified CD10(+) early B cells. These associations were confirmed by the cocapping of CD19 with CD9 or CD82. The CD9/CD19 association was disrupted in the presence of digitonin, contrary to the CD81/CD19 association, indicating that CD9 and CD81 interact with CD19 in different ways. The CD9/CD81 association is also disrupted in the presence of digitonin, suggesting that CD9 associates with CD19 only through CD81. To characterize the regions involved in the CD81/CD19 association, two reciprocal CD9/CD81 chimeric molecules were tested for the association with CD19, but none of them could be coprecipitated with CD19 in digitonin, indicating that the domain of CD81 responsible for its association with CD19 is complex. Finally, engagement of CD9 could induce the tyrosine phosphorylation of different proteins, including CD19 itself, suggesting that the CD9/CD19 association is functionally relevant. Thus, a physical and functional link is formed between the CD19-CD21-CD81 complex and the integrin-tetraspan complexes, which is dynamically modulated in the process of B cell differentiation.
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functional analysis of four tetraspans cd9 cd53 CD81 and cd82 suggests a common role in costimulation cell adhesion and migration only cd9 upregulates hb egf activity
Cellular Immunology, 1997Co-Authors: Cecile Lagaudrieregesbert, Martine Billard, Claude Boucheix, Francois Le Naour, Helene Conjeaud, Sophie Lebelbinay, Emmanuel Lemichez, Patrice Boquet, Eric RubinsteinAbstract:Abstract Molecules of the tetraspan superfamily are engaged in multimolecular complexes containing other proteins such as β1 integrins and MHC antigens. Although their functions are not clear, they have been suggested to play a role in cell adhesion and migration, signal transduction, and costimulation We have in this paper directly compared the functional properties of four tetraspans, CD9, CD53, CD81, and CD82. mAbs to any of these molecules were able to deliver a costimulatory signal for CD3-mediated activation of the T cell line Jurkat. CD82 mAbs were the most efficient in triggering this effect. Moreover, engagement of CD9, CD81, and CD82 induced the homotypic agregation of the megakaryocytic cell line HEL, and inhibited the migration of this cell line. Similar results were obtained with the preB cell line NALM-6 using the CD9 and CD81 mAbs. The CD81 mAb 5A6 produced the strongest effects. Therefore, the tetraspans are recognized by mAbs which produce similar effects on the same cell lines. This is consistent with the tetraspans being included in large molecular complexes and possibly forming a tetraspan network (the tetraspan web). We also demonstrate that the tetraspans are likely to keep specific functional properties inside this network. Indeed, we have demonstrated that the human CD9 is able, like the monkey molecule, to upregulate the activity of the transmembrane precursor of heparin-binding EGF as a receptor for the diphtheria toxin when cotransfected in murine LM cells. Neither CD81, nor CD82 had such activity. By using chimeric CD9/CD81 molecules we demonstrate that this activity requires the second half of CD9, which contains the large extracellular loop, the fourth transmembrane region, and the last short cytoplasmic domain.
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cd9 cd63 CD81 and cd82 are components of a surface tetraspan network connected to hla dr and vla integrins
European Journal of Immunology, 1996Co-Authors: Eric Rubinstein, Martine Billard, Francois Le Naour, Cecile Lagaudrieregesbert, Helene Conjeaud, Claude BoucheixAbstract:CD9, CD63, CD81, and CD82 are glycoproteins of unknown function which belong to the tetraspan superfamily. These molecules have short cytoplasmic sequences, four transmembrane domains and two unequal extracellular regions. Here, we show that these molecules are associated with each other on cell surface and with other glycoproteins such as very late antigen (VLA) integrins and HLA-DR antigens. Moreover, the VLA integrins and HLA-DR antigens were also found to be associated. The interactions of these molecules were analyzed by transfection experiments. It is demonstrated that overexpression of CD9 antigen in Raji cells leads to a lower efficiency of precipitation of CD81 and CD82, suggesting a direct interaction between these molecules. In these cells, the coprecipitation of CD81 and CD82 was not modified, suggesting that these tetraspans did not compete for association. However, in COS-7 cells, transfection of both CD81 and CD82 led to a marked reduction of the number of CD9/CD81 or CD9/CD82 complexes compared to single-transfected cells, and this was associated with the appearance of CD81/CD82 complexes. Therefore, in this cellular system, CD9 competes with CD81 and CD82 for association with the other tetraspan proteins. Finally, the tetraspans do not compete for the association with integrins or HLA-DR. Indeed, when CD9 was expressed in Raji cells, it was incorporated into the pre-existing complexes of these molecules with CD81 and CD82. These data suggest the existence of a tetraspan network which, by connecting several molecules, may organize the positioning of cell surface proteins and play a role in signal transduction, cell adhesion, and motility.