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* Department of Pathology and Laboratory Medicine, Jonsson Comprehensive Cancer Center, University of California Los Angeles (UCLA) School of Medicine, Los Angeles, CA 90095;
Department of Dermatology, University of California Davis School of Medicine, Sacramento, CA 95817;
Departments of Molecular Pharmacology, and Microbiology and Immunology, Albert Einstein College of Medicine, Bronx, NY 10461; and
Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada
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Abstract |
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-galactoside-binding proteins that positively and negatively regulate T cell death. Extracellular galectin-1 directly induces death of T cells and thymocytes, while intracellular galectin-3 blocks T cell death. In contrast to the antiapoptotic function of intracellular galectin-3, we demonstrate that extracellular galectin-3 directly induces death of human thymocytes and T cells. However, events in galectin-3- and galectin-1-induced cell death differ in a number of ways. Thymocyte subsets demonstrate different susceptibility to the two galectins: whereas galectin-1 kills double-negative and double-positive human thymocytes with equal efficiency, galectin-3 preferentially kills double-negative thymocytes. Galectin-3 binds to a complement of T cell surface glycoprotein receptors distinct from that recognized by galectin-1. Of these glycoprotein receptors, CD45 and CD71, but not CD29 and CD43, appear to be involved in galectin-3-induced T cell death. In addition, CD7 that is required for galectin-1-induced death is not required for death triggered by galectin-3. Following galectin-3 binding, CD45 remains uniformly distributed on the cell surface, in contrast to the CD45 clustering induced by galectin-1. Thus, extracellular galectin-3 and galectin-1 induce death of T cells through distinct cell surface events. However, as galectin-3 and galectin-1 cell death are neither additive nor synergistic, the two death pathways may converge inside the cell. |
Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionDisclosuresReferences |
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The galectins are a family of mammalian proteins that positively and negatively regulate cell death (4, 5, 6). The galectins are unique in that different family members, including galectin-1, -2, -3, -7, -8, -9, and -12, can regulate cell death either inside or outside the cell (7, 8, 9, 10, 11, 12, 13). As galectins are carbohydrate-binding proteins, galectins that act extracellularly to induce cell death do so by binding specific glycoproteins in a saccharide-dependent manner. For example, galectin-1, which kills human thymocytes and activated peripheral T cells (14, 15), binds CD7, CD43, and CD45 on T cells (16). All three glycoproteins are involved in regulating susceptibility to galectin-1, and specific oligosaccharide modifications of CD43 and CD45 control galectin-1 binding and T cell susceptibility to death (17, 18).
Although galectin-1 regulates T cell death only via the extracellular route, and galectin-7 acts only intracellularly to promote epithelial cell apoptosis (10, 19), galectin-3 regulates cell death from both outside and inside the cell (9, 20). Moreover, galectin-3 is the only family member with both pro- and antiapoptotic activity (5). Cytoplasmic galectin-3 antagonizes apoptosis by associating with the mitochondrial membrane to maintain mitochondrial membrane integrity and antagonize the release of cytochrome c (9, 21, 22). In contrast, extracellular galectin-3 directly induces T cell death (20).
Galectin-1 and galectin-3 are the most ubiquitously expressed members of the galectin family. In some tissues, only galectin-1 or galectin-3 is expressed; galectin-1 is expressed in skeletal and cardiac myocytes, hepatocytes, and prostate stromal cells, while galectin-3 is expressed in epithelial cells of the digestive and respiratory tracts (23). In many immune cells and tissues, galectin-1 and galectin-3 are coexpressed, these include T cells, B cells, NK cells, macrophages, dendritic cells, endothelial cells, and fibroblasts, with high levels of both galectins in thymus and lymph nodes (5, 24, 25, 26).
Both galectin-1 and galectin-3 can bind to T cells and trigger T cell death (14, 20); however, these two lectins likely recognize discrete sets of oligosaccharide ligands expressed on distinct glycoprotein backbones bearing these ligands. Although both galectin-1 and galectin-3 recognize the disaccharide galactose-1,4-N-acetylglucosamine as a minimal saccharide ligand, the two galectins differ in fine specificities for modified oligosaccharide ligands, due to structural differences in the carbohydrate-recognition domain (27, 28, 29, 30, 31).
As thymocytes and T cells will encounter galectin-1 and galectin-3 in normal and inflamed tissues, it is critical to identify similarities and differences between the galectin-1 and galectin-3 T cell death pathways, to understand the distinct roles of the galectins in vivo and the effects of administering exogenous galectins as immunosuppressive agents. For example, while both galectin-3 and galectin-1 are immunosuppressive in models of autoimmune disease, administration of galectin-3 results in suppression of Th2-type cytokines, while administration of galectin-1 results in suppression of Th1-type cytokines (4, 32, 33). Understanding the mechanisms that regulate susceptibility of T cell populations to the different galectins will allow precise modulation of T cell responses by specific galectins.
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Materials and Methods |
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Human T cell lines MOLT-4, Jurkat E6-1, J45.01 (American Type Culture Collection), CEM, CEM.DKO (Ref.34 ; a gift from Dr. B. Ardman, New England Medical Center, Boston, MA), Jurkat A-11, and the CD29-deficient derivative (Ref.35 ; a gift from Dr. Y. Shimizu, University of Minnesota, Minneapolis, MN) were maintained in complete RPMI (RPMI 1640 (Invitrogen Life Technologies) supplemented with 2 mM glutamine, 10% FBS, and 10 mM HEPES) in 5% CO2 at 37°C. J45.01 cells reconstituted with murine CD45RABC were previously described (36). Murine T cell lines BW5147 and CD45–/– derivative (Ref.17 ; a gift from Dr. K. Bottomly, Yale University, New Haven, CT) were maintained in Iscove’s modified DMEM (Invitrogen Life Technologies) supplemented with 10% FBS and 0.1% 2-ME in 10% CO2 at 37°C.
The following mAbs were obtained from the indicated suppliers: CD43 (DFT1), CD45 (leukocyte common Ag), CD4-PE (MT310), CD8-allophycocyanin (DK25), and mouse IgG1- and IgG2a-negative control Abs from DakoCytomation; CD45 (F10-89-4) and CD29-FITC (TDM29) from Southern Biotechnology Associates; CD7 (M-T701), CD71 (M-A712), and anti-mouse CD45 (30F11) from BD Pharmingen; CD29 (4B7R) from Serotech; anti-galectin-3 (Mac-2; M3/38) from Boehringer Mannheim. Secondary detection reagents were obtained from the indicated supplier: goat anti-mouse IgG-FITC (DakoCytomation); streptavidin (SA)3-FITC (Jackson ImmunoResearch Laboratories); SA-HRP and rabbit anti-mouse IgG-HRP (Zymed Laboratories); goat anti-rabbit IgG-HRP (Bio-Rad); Alexa Fluor 568 goat anti-mouse IgG and SA-Oregon green (Molecular Probes).
Recombinant human galectin-1 and galectin-3 were prepared as previously described (37, 38). Anti-galectin-1 and anti-galectin-3 polyclonal rabbit sera were previously described (39, 40).
Tissue immunostaining
Five-micrometer sections of paraffin-embedded human tonsil or thymus on glass slides were heated at 60°C for 30 min, deparaffinized with xylene and ethanol, rinsed with dH2O, and fixed with 3% H2O2 for 5 min. Slides were blocked with 20% goat serum in PBS for 20 min before addition of 1/1000 dilution of anti-galectin-1 serum, anti-galectin-3 serum, or nonimmune rabbit serum in 2% goat serum/PBS. For immunohistochemistry, bound primary Ab was detected with mouse anti-rabbit IgG-HRP diluted 1/1000 in PBS and developed with 3-amino-9-ethylcarbazole (Biomedia) for 10 min at 37°C. Slides were counterstained with hematoxylin for 1–2 min, washed with PBS, and mounted with Faramount (DakoCytomation). For immunofluorescence studies, galectin-1 and galectin-3 were detected with rabbit polyclonal anti-galectin-1 and mouse monoclonal anti-galectin-3 Abs, followed by goat anti-rabbit IgG-Texas Red and goat anti-mouse IgG-FITC. Primary cultures of human thymic epithelial cells were cultured and cells were stained with anti-galectin-1 and anti-galectin-3 polyclonal antisera and bound Ab detected with goat anti-rabbit IgG-FITC as previously described (39). Images were collected on an Olympus AX70 microscope for immunohistochemistry, an Axioskop 2 plus fluorescent microscope, or an Olympus IX70 confocal microscope, and analyzed using Spot Advanced Version 4.0.4 software (Diagnostic Instruments) or Fluoview 2.0 software (Olympus).
Determination of galectin cell surface binding
Binding of biotinylated galectin-1 or galectin-3 to T cells or thymocytes was performed as described (18). Briefly, 5 x 105 cells were incubated for 30 min at 4°C with increasing concentrations of biotinylated galectin-1 or galectin-3 to construct binding curves, and galectin concentrations that gave 
50% maximal binding (5.5 µM galectin-1 and 0.67 µM galectin-3) were used for inhibition-binding assays with 0.1 M -lactose. Binding assays were performed at 4°C to minimize cell death. For galectin-3/galectin-1 competition-binding studies, cells were incubated with 10 µM biotinylated galectin-1 in the presence of 10 µM unlabeled galectin-3. Cells were washed two times with PBS and stained with 3 µg of SA-FITC and 0.6 µg of 7-aminoactinomycin D (Molecular Probes) to detect galectin binding and dead cells, respectively. Flow cytometry data were acquired using a BD Biosciences BD-LSR I Analytic Flow Cytometer and analyzed with CellQuest software (BD Biosciences).
T cell death assays
T cell death assays were performed as previously described (37). Briefly, 2 x 105 cells were incubated in 200 µl of complete RPMI with the indicated final concentration of galectin-1, galectin-3, both galectin-1 and galectin-3, or buffer control with or without 0.1 M -lactose for 4 h at 37°C. Galectin was dissociated with 0.1 M -lactose and cell death detected by labeling with Annexin VGFP and propidium iodide (PI; Molecular Probes). For detection of cells containing subdiploid DNA, fixed permeabilized cells were stained with PI and DNA content was determined as previously described (15, 37). All death assays were performed in triplicate and data was acquired using a BD Biosciences BD-LSR I Analytic Flow Cytometer and analyzed with CellQuest software (BD Biosciences). The percentage of cell death of T cell lines was determined as: ((percent annexin V–, PI– cells in control-treated sample) – (percent annexin V–, PI– cells in galectin-treated sample))/(percent annexin V–, PI– cells in control-treated sample). The percentage of cell loss of T cell lines was determined as described below for thymocytes.
Thymocyte cell loss
Human thymocytes were isolated from surgical specimens as previously described and cultured overnight in serum-free medium (AT-IMDM) consisting of IMDM (Omega Scientific) supplemented with 1100 µg/ml delipidated BSA (Sigma-Aldrich), 85 µg/ml transferrin (Sigma-Aldrich), 2 mM glutamine, and 25 U/25 µg/ml penicillin/streptomycin (15). The following day, 106 cells in 200 µl were incubated with the indicated concentration of galectin-1, galectin-3, or buffer control (DTT or PBS/glycerol) in AT-IMDM for 3–5 h at 37°C. Galectin was dissociated with 0.1 M -lactose and cells were washed with PBS before staining with CD4-PE and CD8-allophycocyanin for 45 min at 4°C. Cells were analyzed on a BD Biosciences FACScan Flow Cytometer using CellQuest software. As we have previously found that there is high baseline binding of annexin V binding to thymocytes isolated in this manner, thymocytes were assessed for viability based on forward vs side scatter and absence of 7-aminoactinomycin D permeability, as we have previously described (17, 37). Loss of viable thymocytes from each population was determined as: percent cell loss = 100 x ((number of viable control-treated cells) – (number of viable galectin-treated cells))/(number of viable control-treated cells).
Isolation of galectin-3-binding proteins by affinity chromatography
Galectin-3 was conjugated to cyanogen bromide-activated Sepharose 4B (Sigma-Aldrich). Cell surface proteins on 3 x 108 cells were labeled with Sulfo-NHS-biotin (Pierce), plasma membrane preparations were isolated and solubilized in 0.1% Tween 20, and the extract was applied to the galectin-3 column as previously described (16).
After washing extensively with PBS, 0.1% Triton X-100, 0.02% sodium azide (wash buffer), bound proteins were eluted with 0.1 M -lactose in wash buffer (elute buffer). Fractions were collected, resolved by reducing 10% SDS-PAGE, transferred to nitrocellulose, and detected with SA-HRP. Proteins were visualized by ECL (Amersham).
Identification of galectin-3-binding proteins
Glycoproteins eluted from the galectin-3 affinity column were concentrated on a YM-3 Centricon (Millipore) and resolved by electrophoresis on 10% SDS-PAGE. Separated proteins were visualized by Coomassie Brilliant Blue (Sigma-Aldrich) and the relevant portions of the gel were excised for polypeptide sequence analysis. Sequence analysis was performed at the Harvard Microchemistry Facility (Cambridge, MA) by microcapillary reverse-phase HPLC nanoelectrospray tandem mass spectrometry on a Finnigan LCQ DECA XP Plus quadruple ion trap mass spectrometer (Thermo Electron). To confirm the identity of glycoproteins in the sample eluted from the galectin-3 column, candidate Abs were used for immunoprecipitation or immunoblotting. For immunoprecipitation with anti-CD29, biotin-labeled T cell glycoproteins eluted from the galectin-3 column, or total biotin-labeled membrane proteins as a control, were immunoprecipitated with anti-CD29, separated by 10% SDS-PAGE, and electroblotted onto nitrocellulose membrane (Hybond C-extra; Amersham). The membrane was blocked with 5% skim milk in PBS, probed with SA-HRP, and washed extensively with 0.1% Tween 20 in PBS. Proteins were visualized by ECL.
Alternatively, total membrane proteins or membrane proteins specifically eluted from the galectin-3 column were resolved by SDS-PAGE, electroblotted, and probed with anti-CD43, anti-CD45, or anti-CD71 primary Abs followed by HRP-conjugated rabbit anti-mouse IgG. Bound Ab was detected by ECL.
Characterization of receptor localization following galectin-3 treatment
A total of 107 CEM cells were incubated with 5 µM galectin-3 in PBS with 10% glycerol, or PBS/glycerol alone, for 2 h at 37°C with 5% CO2. Cells were cooled to 4°C, and bound galectin-3 dissociated with ice-cold 0.1 M -lactose. Cells were stained with biotin-annexin V (Molecular Probes) for 30 min on ice and fixed with 2% paraformaldehyde for 30 min on ice. The reaction was quenched with 0.2 M glycine for 5 min, followed by staining with mouse anti-human CD45 leukocyte common Ag or mouse anti-human CD71, for 1 h on ice. After washing, bound annexin V was detected with SA-Oregon green, and bound Ab was detected with Texas Red-conjugated goat anti-mouse IgG for 1 h at 4°C. Cells were washed and mounted on glass microscope slides using Prolong Anti-fade mounting media (Molecular Probes). Isotype control-stained and single-stained cells were used to control for nonspecific staining and compensation between fluorescent channels, respectively. Fluorescently labeled cells were analyzed using the x100 objective on a Leica CLSM confocal laser scanning microscope. Cells were scanned by dual excitation of Oregon green and Alexa Fluor 568 (red) fluorescent probes. Dual emission fluorescent images were collected in separate channels at 0.5-µm optical slices. Images were processed using Leica Confocal Software. Areas of red and green overlapping fluorescence were represented with a yellow signal. Clustering was defined as receptor aggregation in one, two, or three large patches on the cell surface. Clustering was analyzed on groups of images containing 30–80 cells. A total of 90 PBS/glycerol-treated and 90 galectin-3-treated cells stained with anti-CD45, and 140 PBS/glycerol-treated and 240 galectin-3-treated cells stained with anti-CD71 were analyzed.
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Results |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionDisclosuresReferences |
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Both galectin-1 and galectin-3 are expressed in lymphoid tissues such as thymus and lymph node, so that T cells could encounter either or both galectin-1 and galectin-3 at different anatomic sites (4, 5). To demonstrate the coexpression of galectin-1 and galectin-3 in lymphoid tissue, sections of human thymus and tonsil were labeled with polyclonal rabbit anti-human galectin-1 or rabbit anti-human galectin-3. As shown in Fig. 1, galectin-3 was detected throughout the thymus, in the capsular, cortical, and medullary regions; galectin-3 was detected surrounding thymocytes and intracellular galectin-3 was abundant in epithelial cells in both cortical and medullary regions as determined by morphology and anatomic localization (Fig. 1C). A similar pattern was observed for galectin-1 immunoreactivity (Fig. 1B), as we have previously described (39). As galectin-1 and galectin-3 can be localized both intracellularly and extracellularly, we confirmed that thymic epithelial cells secrete the two galectins onto the cell surface. Primary cultures of human thymic epithelial cells were fixed and intact cells were stained with the polyclonal rabbit antisera used for immunohistochemistry. Primary human thymic epithelial cells demonstrated robust cell surface staining with anti-galectin-1, as we have previously observed (39), and also with anti-galectin-3, while control antiserum showed no significant nonspecific immunofluorescence (Fig. 1). Thus, thymic epithelial cells express and externalize both galectin-1 and galectin-3, indicating that developing thymocytes would be exposed to both galectin-1 and galectin-3 in the thymus.
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Like galectin-1, galectin-3 has been reported to kill T cell lines, although the mechanism of galectin-3-induced death is not well understood (20). We compared the ability of galectin-3 and galectin-1 to trigger T cell death. To demonstrate that galectin-3 binding to T cells is carbohydrate dependent, biotinylated galectin-3 was bound to T cells in the presence or absence of lactose (Fig. 3A). Binding of galectin-3, like binding of galectin-1, was inhibited by lactose, demonstrating that galectin-3 binds to glycan ligands on the T cell surface.
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Although galectin-3 is expressed in human thymus, the susceptibility of human thymocytes to galectin-3-induced death is unknown. We added galectin-3 or galectin-1 to total human thymocytes and analyzed loss of viable cells from different thymocyte subsets. As shown in Fig. 4, galectin-3 induced loss of both CD4CD8 double-negative (DN) and double-positive (DP) thymocytes, with negligible loss of CD4 or CD8 single-positive thymocytes (data not shown). Increasing concentrations of galectin-3 resulted in increased loss of cells in both DN and DP subsets. However, DN thymocytes were more susceptible to galectin-3, as shown in Fig. 4A. Treatment with 5 µM galectin-3 resulted in an 25% loss of viable DN thymocytes and treatment with 20 µM galectin-3 resulted in a loss of >60% of DN thymocytes. In contrast, we observed a <10% cell loss of DP thymocytes treated with 5 µM galectin-3, and maximal loss of DP thymocytes with 20 µM galectin-3 was <30%. The relative selectivity of galectin-3 for DN thymocytes is very different from the effects of galectin-1 on thymocyte subpopulations. As we have previously shown (21), human DN and DP thymocytes were both susceptible to galectin-1 (Fig. 4B). Thus, while thymocytes would encounter both galectin-3 and galectin-1 in the thymic stroma, the two galectins may have distinct effects on different thymic subsets in vivo.
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Although both galectin-3 and galectin-1 bind to T cells in a carbohydrate-dependent manner (Fig. 3A), the saccharide ligands preferentially recognized by the two galectins are expressed on numerous T cell surface glycoproteins. As galectin-3 and galectin-1 have very distinct structural features, with galectin-3 (which is primarily a monomer in solution) forming a pentamer, joined by flexible N termini, when the C-terminal-binding domains bind to clustered saccharide ligands, and galectin-1 forming a noncovalent rigid homodimer (28, 41, 42), galectin-3 and galectin-1 may recognize similar saccharides on distinct glycoprotein backbones. To investigate whether galectin-3 and galectin-1 bind to different glycoprotein receptors, we asked whether galectin-3 and galectin-1 compete for binding to receptors on the T cell surface. Biotinylated galectin-1 (10 µM) was bound to T cells in the absence or presence of increasing concentrations of unlabeled galectin-3 at 4°C, and bound galectin-1 detected with SA-FITC. Galectin-3 only partially inhibited galectin-1 binding to the T cell surface; maximal inhibition of galectin-1 binding by galectin-3 was 50% (Fig. 6). These results indicated that galectin-3 and galectin-1 preferentially recognize distinct repertoires of T cell surface glycoprotein receptors.
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chain. Notably, CD7, an important TCR for galectin-1 (7), was not identified in the material eluted from the galectin-3 column. To examine T cell glycoprotein receptors that could participate in galectin-3-induced death, we focused on CD29, CD43, CD45, and CD71, all of which have been previously implicated in T cell death (20, 45, 46, 47, 48, 49). We confirmed the presence of these four glycoproteins in the eluate from the galectin-3 affinity matrix by immunoprecipitation or Western blotting. As shown in Fig. 7, CD29, CD43, CD45, and CD71 glycoproteins were four of the predominant bands isolated from the galectin-3 affinity column.
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Although identification of T cell surface glycoproteins that bound galectin-3 was a critical step in defining the glycoproteins involved in galectin-3-mediated death, it is important to note that T cell glycoproteins modified with the appropriate glycans may bind to galectin-3, yet not be required for T cell death. This has previously been demonstrated for galectin-1; while galectin-1 binds CD2 and CD3, neither of these glycoproteins are required to trigger galectin-1-induced T cell death (7, 14).
To determine the roles of CD29, CD43, and CD45 in galectin-3-induced T cell death, we examined a panel of cell lines with pairs of cells expressing or lacking the indicated glycoprotein. Cells were treated with 5 µM galectin-3 and cell death was determined by annexin V. As shown in Fig. 8A, CD29null Jurkat cells were susceptible to galectin-3-induced death. Similarly, CD43null CEM cells were susceptible to galectin-3-induced death (Fig. 8A). Thus, neither CD29 nor CD43 are required for galectin-3-induced T cell death.
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To examine the role of CD71 in galectin-3 cell death, we attempted to reduce CD71 expression in Jurkat E6–1 and CEM T cells by small-interfering RNA. Although we were able to decrease CD71 expression in Jurkat E6–1 cells by 50%, as detected by mean fluorescent intensity of CD71 staining, we observed no difference in cell death induced by galectin-3 in small-interfering RNA-treated cells compared with control transfected cells (data not shown). The fact that transferrin is a survival factor for many cell types (50) may explain why we were unable to reduce CD71 expression by >50%, and the partial reduction in CD71 expression that we could achieve may not have been sufficient to affect T cell susceptibility to galectin-3.
Galectin-3 and galectin-1 trigger death via different cell surface receptors
Our laboratory previously demonstrated a requirement for CD7 in galectin-1-induced cell death (7), and previous work using blocking Abs suggested a role for CD7 in galectin-3-induced T cell death (20). However, we did not detect CD7 among the T cell membrane glycoproteins that specifically bound to galectin-3 (Table I). To specifically address the role of CD7 in galectin-3 cell death, we examined the effect of galectin-3 on CD7null Hut78 T cells. Hut78 cells are resistant to galectin-1-induced death, while expression of CD7 in Hut78 cells rendered the cells susceptible to galectin-1 (7). As shown in Fig. 8C, while Hut78 cells were resistant to cell death induced by galectin-1, we observed significant death of Hut78 cells after addition of galectin-3. These data demonstrate that galectin-3 and galectin-1 induce T cell death via binding to different cell surface glycoproteins; galectin-1 T cell death requires CD7, while galectin-3 T cell death does not, and CD45 is not required for galectin-1-induced death, while CD45 appears to be required for galectin-3-induced death (Fig. 8).
Galectin-3 induces clustering of CD71, but not CD45, on the T cell surface
Our laboratory has previously shown that galectin-1 binding results in clustering of CD45 and colocalization of CD45 with phosphatidylserine on apoptotic blebs during galectin-1-induced T cell death (16). As shown above, galectin-3, like galectin-1, binds to CD45, and CD45 may contribute to galectin-3 induced cell death (Figs. 7 and 8). However, as galectin-3 and galectin-1 have distinct structural features (5, 27, 28), the two galectins may have different effects on glycoprotein localization after binding. Thus, we determined the effect of galectin-3 binding on CD45 localization on the surface of CEM T cells. Before galectin-3 treatment, CD45 was diffusely distributed on the T cell surface, as demonstrated by immunofluorescence (data not shown). After galectin-3 binding, CD45 remained diffusely distributed on the T cell surface (Fig. 9A). To confirm that the T cells exposed to galectin-3 were undergoing cell death, cells were also labeled with annexin V. As shown in Fig. 9A, annexin V binding was concentrated in patches on apoptotic blebs of dying cells, as we observed during galectin-1 T cell death (16). However, unlike galectin-1, galectin-3 did not induce redistribution of CD45 to apoptotic blebs on dying cells.
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Discussion |
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Numerous examples of similarities and differences in galectin-3 and galectin-1 functions have been described. Although both galectin-3 and galectin-1 participate in RNA splicing in the nucleus (52), only intracellular galectin-3 prevents apoptosis triggered by a variety of agents, by localizing to the mitochondria and preventing cytochrome c release (22, 53). Although both galectin-3 and galectin-1 can interact with the Fas-mediated death pathway, extracellular galectin-1 augments Fas-induced death (54), while intracellular galectin-3 directs the death pathway triggered by Fas binding (55). Although both galectin-3 and galectin-1 can mediate binding of pathogens to host cells, only galectin-1 promotes attachment of HIV-1 to target cells, while galectin-3 inhibits galectin-1-facilitated HIV attachment (56, 57). Although both galectin-3 and galectin-1 bind to T cells to trigger T cell death, we show here that the galectins differ with respect to cell surface receptors, receptor localization after binding, and requirements for specific receptors to trigger T cell death. Although administration of both galectin-3 and galectin-1 were immunosuppressive in several animal models of inflammatory disease, and both galectin-3 and galectin-1 influence the threshold of TCR signaling (58, 59), galectin-1 treatment reduces Th1-type cytokine production (5, 32, 60), while galectin-3 treatment reduces Th2-type cytokine production (33, 61). Moreover, galectin-3 and galectin-1 knockout mice have distinct phenotypes. Galectin-3-deficient mice have attenuated neutrophil recruitment, while galectin-1-deficient mice have increased neutrophil recruitment compared with wild-type mice in a model of peritoneal inflammation (J. C. Paulson, Consortium for Functional Glycomics: 
www.teleimpac.com/glycomics/publicdata/phenotyping.jsp. 
and Ref.62), consistent with observations that galectin-1 antagonizes neutrophil adhesion to endothelium, while galectin-3 promotes neutrophil adhesion to endothelium (63, 64). Thus, there is ample evidence that galectin-3 and galectin-1 have overlapping but distinct functions in immune regulation.
Our data clearly demonstrate that galectin-3 and galectin-1 require distinct cell surface glycoprotein receptors to trigger T cell death. Galectin-1 binds to and requires CD7 expression to trigger T cell death (7), but galectin-3 does not bind CD7 nor require CD7 to trigger T cell death. Furthermore, the major T cell glycoproteins recognized by galectin-3 differ from those recognized by galectin-1. As galectin-3 and galectin-1 bind distinct sets of oligosaccharide ligands (29, 30, 31), these ligands may be differentially displayed on specific T cell glycoproteins. Both galectin-1 and galectin-3 bind CD29, CD43, and CD45, but only galectin-3 binds CD71, and only galectin-1 binds CD7 and CD2 (7, 16, 65). Not only do galectin-3 and galectin-1 bind distinct complements of glycoprotein receptors, galectin-3 and galectin-1 also induce distinct patterns of clustering of these receptors on the T cell surface. Although both galectin-3 and galectin-1 bind CD45, CD45 clustering occurs after galectin-1 binding (16), while CD45 clustering was not observed during galectin-3-induced cell death. However, galectin-3 did induce clustering of CD71 on dying cells (Fig. 9), and we observed no death of cells that did not cluster CD71 after galectin-3 binding. Thus, CD71 clustering may be involved in the galectin-3 death pathway. Intriguingly, both DN and DP thymocyte subsets express CD45 and CD71, yet we observed differential susceptibility to galectin-3 between these two subsets (Fig. 4). Additional factors, such as differences in glycosylation between these thymocyte subsets (4), may determine the relative susceptibility of the cells to galectin-3. For example, different isoforms of CD45 are differentially glycosylated, and specific CD45 isoforms can be modified by glycosyltransferases expressed in different thymocyte subsets (17, 18); while the present work only determined that the CD45RABC isoform was sufficient to render Jurkat cells susceptible to galectin-3, ongoing studies in our laboratory are examining the roles of different CD45 isoforms and differential CD45 glycosylation in regulating cell susceptibility to galectin-3.
The precise oligosaccharide ligands that regulate galectin-3-induced T cell death remain undefined. However, our observation that galectin-3 kills BW5147 T cells indicates that galectin-3 and galectin-1 also have different requirements for cell surface glycosylation. BW5147 cells lack expression of the core 2 N-acetylglucosaminyltransferase (C2GnT) that is required for galectin-1 cell death (17). As BW5147 cells died in response to galectin-3, the specific glycans made by C2GnT are not required for galectin-3 cell death. Differences in recognition of or requirement for specific oligosaccharide ligands may reflect differences in the carbohydrate recognition domains of the two galectins or may result from structural differences between galectin-3 and galectin-1 that dictate how the different galectins can interact with glycan ligands on the cell surface.
Galectin-3 and galectin-1 have several structural features that may contribute to differential receptor recognition and clustering of cell surface glycoproteins. Galectin-1 is a rigid noncovalent homodimer, with a Kd in the low micromolar range (42). We have demonstrated that the dimeric form of galectin-1 is required for cell death, and the rigid homodimer may be critical for the galectin-1 pattern of receptor binding and homogeneous receptor clustering on the T cell surface (16). In contrast, galectin-3, that is a monomer in solution, forms pentamers via the flexible N-terminal domains after binding to saccharide ligands on an immobilized surface, such as the surface of a T cell, and forms heterogenous cross-linked complexes of multivalent glycoconjugates (41). Structural differences between flexible pentameric galectin-3 vs rigid dimeric galectin-1 likely account for the distinct effects on receptor clustering, as well as the different amounts of the two galectins required to kill cells. Although 20 µM galectin-1 was required for 50% death of Jurkat and MOLT-4 T cells, 1–5 µM galectin-3 was sufficient to induce 50% cell death. The pentameric form of galectin-3 may allow binding and cross-linking of greater numbers of T cell surface receptors. Alternatively, as carbohydrate-protein interactions are low affinity but high avidity, pentameric galectin-3 may have a higher average time of occupancy on saccharide ligands attached to a polypeptide backbone, compared with galectin-1. All these factors may contribute to the lower concentration of galectin-3 required to trigger T cell death compared with galectin-1. These results imply that, in tissue with both galectin-3 and galectin-1 expression, galectin-3 effects may predominate at sites where the concentrations of the two galectins are equivalent.
As shown in Table I, several T cell glycoproteins were eluted from the galectin-3 affinity column. The precise roles of these glycoproteins in galectin-3-induced cell death remain unknown. Four glycoproteins that bound galectin-3, CD29, CD43, CD45, and CD71, have been implicated in T cell apoptosis. Specifically, Ab cross-linking of CD43, CD45, or CD71, or CD29 cross-linking by the Yersinia protein Invasin all induce T cell apoptosis (45, 46, 47, 48, 49). However, while CD29 Abs blocked galectin-3-induced T cell apoptosis (20), our data indicate that CD29 expression is not absolutely required for cell death (Fig. 8). Similarly, while CD43 contributes to galectin-1-induced cell death (J. Hernandez and L. G. Baum, unpublished data), CD43 expression was not required for galectin-3-induced cell death (Fig. 8). As we have also observed that galectin-3 kills murine BW5147 cells that do not express the TCR complex, this implies that the TCR chain that was isolated on the galectin-3 affinity matrix (Table I) is also not required for galectin-3-induced cell death. Instead, our data suggest that CD45 is involved in triggering galectin-3-mediated cell death, as cells that lack CD45 expression were not susceptible to galectin-3, and restoration of CD45 expression restored susceptibility to galectin-3 (Fig. 8). Moreover, we observed galectin-3-induced clustering of CD71 (Fig. 9), suggesting that galectin-3 binding to CD71 is also involved in sending a death signal. Further work is required to elucidate the precise roles of CD45 and CD71 in galectin-3-induced death.
Identification of galectin-3 TCRs and characterization of receptor clustering not only have important implications for the galectin-3 death pathway, but also suggest a mechanism by which galectin-3 may restrict TCR recruitment to the immunological synapse (58). As we also isolated TCR from the galectin-3 affinity column (Table I), galectin-3 interaction with TCR may contribute to setting the threshold for TCR response to Ag. Similarly, as localization of CD71 to the peripheral ring of the immunological synapse occurs during T cell activation (66), galectin-3 clustering of CD71, preventing CD71 recruitment to the synapse, may also contribute to the inhibitory effect of galectin-3 on TCR signaling. Alternatively, galectin-3 may form a lattice that cross-links and restricts movement of many different receptors, including CD29, CD43, CD45, CD71, and TCR, to antagonize formation of the immune synapse.
Although upstream glycoprotein receptors for galectin-3 and galectin-1 are distinct, downstream mechanisms of cell death may be common, as we observed that T cell death induced by galectin-3 and galectin-1 was neither additive nor synergistic (Fig. 4). This is in contrast to the additive or synergistic effects of galectin-1 in cell death induced by CD3 or Fas cross-linking (15, 54). Commonality of galectin-3 and galectin-1 intracellular functions following distinct upstream events is not unusual. Similar findings were reported for the induction of neutrophil respiratory burst by galectin-3 and galectin-1. Although both galectins induce NADPH oxidase activity of primed neutrophils with similar kinetics, galectin-1 and galectin-3 bound distinct subsets of receptors on neutrophils to trigger a respiratory burst (67).
Why do galectin-1 and galectin-3 both kill T cells? Both galectin-1 and galectin-3 are abundantly expressed in several tissues, including thymus and lymph nodes (4, 24, 39, 57, 68, 69). Although a recent report noted that the amount of galectin-3 protein in total lymph node tissue is much lower than the amount of galectin-1 (57), this quantification did not distinguish expression by distinct cell types. For example, Fig. 2 demonstrates that, as we have previously described, galectin-1 is abundantly expressed by endothelial cells as well other cells in the lymph node (68), while galectin-3 is not expressed by endothelial cells. However, in the vicinity of follicular dendritic cells, T cells will encounter abundant galectin-3 and galectin-1. Moreover, while secreted, galectins typically concentrate on the cell surface and the local matrix, raising the local concentration of a galectin above that detected in tissue homogenates (70). Yet, while T cells will encounter both galectins at various tissue sites, we have now shown that galectin-3 and galectin-1 recognize different oligosaccharide ligands and T cell surface glycoproteins. Thus, subtle distinctions in receptor expression, stoichiometry, or glycosylation, as well as differences between galectin-1 and galectin-3 multimeric structures and cell-specific patterns of expression, may allow for greater selectivity in induction of cell death in specific T cell populations by galectin-1 and galectin-3.
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1 This work was supported by National Institutes of Health (NIH) Grant GM63281 (to L.G.B.) and NIH National Research Service Award Predoctoral Fellowships T32 AI52031 and CA09056 (to B.N.S.). 
2 Address correspondence and reprint requests to Dr. Linda G. Baum, Department of Pathology and Laboratory Medicine, UCLA School of Medicine, 10833 Le Conte Avenue, Los Angeles, CA 90095. E-mail address: lbaum{at}mednet.ucla.edu
3 Abbreviations used in this paper: SA, streptavidin; PI, propidium iodide; DN, double negative; DP, double positive.
Received for publication June 6, 2005. Accepted for publication October 27, 2005.
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-Galactoside-binding protein secreted by activated T cells inhibits antigen-induced proliferation of T cells. Eur. J. Immunol. 28: 2311-2319. [Medline]-galactoside-binding protein. Proc. Natl. Acad. Sci. USA 91: 1428-1432. -galactoside-binding lectins from human lung. J. Biol. Chem. 262: 7383-7390. 1 integrin-deficient human T cell to identify 1 integrin cytoplasmic domain sequences critical for integrin function. Mol. Biol. Cell 9: 2715-2727. -galactoside-binding lectin, in human monocytes and macrophages. Am. J. Pathol. 147: 1016-1028. [Abstract]-galactoside-binding lectin in Chinese hamster ovary cells. I. Physical and chemical characterization. J. Biol. Chem. 270: 5198-5206. -1 integrins by breast carcinoma cells. Biochem. Biophys. Res. Commun. 289: 845-850. [Medline]1-integrin. Eur. J. Immunol. 32: 1129-1138. [Medline]
-chain phosphorylation and antagonizes processive TCR signal transduction. J. Immunol. 165: 3722-3729. -1 subunit of integrin. Biochem. Biophys. Res. Commun. 310: 1010-1016. [Medline]This article has been cited by other articles:
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 |
|
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|
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|
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|
|
|
|
|
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|
|
|
|
 |
|
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|
|
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|
|
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|
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|
|
|
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|
|
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|
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|
|
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|
|
|
|
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|
|
|
|
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|
|
|
|
|
|
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|
|
|
|
|
|
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|
|
|
|
 |
|
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|
|
|
|
|
|
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|
|
|
|
 |
|
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|
|
|
|
|
|
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|
|
|
|
|
|
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|
|
|
|
|
|
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, buffer control; 
, galectin-3). Cells transfected with vector alone (45.0 vector) remained resistant to galectin-3. C, Hut78, a T cell line lacking CD7, was treated with galectin-1 or galectin-3 and cell death determined by annexin V binding. Galectin-3, but not galectin-1, induced death of Hut78 T cells. Dotted and black lines represent annexin V binding to cells treated with buffer control and galectin, respectively. Data shown are from one representative of three independent experiments.