| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
The Biomedical Research Centre, University of British Columbia, Vancouver, British Columbia, Canada
 |
Abstract |
|---|
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
|
Introduction |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
A focus of recent galectin reseach has suggested that galectin 1 may be used to regulate T cell immunity by inducing apoptosis in those activated T cells not destined for the memory pool. The hypothesis that galectin 1 is a physiological regulator of T cell death principally through binding core 2-branched lactosamine extensions on O-gylcans and thereby cross-linking specific cell surface glycoproteins was recently reviewed (3). This hypothesis is essentially based on: 1) the galectin 1-mediated killing of mitogen-activated, but not resting, human T cells (8); 2) the galectin 1-induced killing of a 
(1–6)N-acetyl glucosaminyl transferase I (C2GnT1)-transfected T cell line (9); 3) increased galectin 1-induced death in thymocytes from C2GnT1 transgenic mice (9); and 4) guilt by association insofar as galectins are expressed in activated T cells and in the thymus, where negative selection of CD4+8+ T cells occurs, and C2GnT1 is expressed preferentially in both cortical thymocytes (10) and mature T cells after activation in vitro (11) or in vivo (12).
Despite the array of observations that galectin 1 can promote death of both immature thymocytes and activated human T cells, the generality of these observations, the involvement of C2GnT1, and the conclusive evidence that galectin 1 is involved in these processes under physiological conditions is lacking. One would predict that conditions altering C2GnT1 activity or galectin 1 expression in vivo would adversely affect T cell homeostasis. However, mice lacking either galectin 1 (13) or the C2GnT1 enzyme (14) show no such deregulation; redundancy in the galectin/C2GnT multigene families and compensatory lactosamine-bearing extensions of core 1 glycans may obscure relevant functions in these knockout mice. Furthermore, Blaser et al. (15) reported that murine galectin 1 inhibited proliferation of Ag-specific activated murine CD8 T cells but did not report cytolytic effects, and Rabinovich et al. (16) reported that chicken galectin 1 induced apoptosis when included during primary Con A stimulation of rat lymphocytes. Novelli et al. (17) reported that human galectin 1 inhibited proliferation of human PHA-stimulated and IL-2-expanded PBLs, but, contrary to observations cited above (8), apoptosis was not observed. Most recently, Amano et al. (18) reported that ST6 sialyltransferase modification of CD45 N-glycans inhibited galectin-induced death of T cell lines, whereas Fajka-Boja et al. (19) confirmed galectin 1 binding to CD45, but concluded that CD45 does not mediate the apoptotic signal initiated by galectin. Clearly, the role of C2GnT-branched O-glycans in galectin-induced T cell death is not resolved.
During analysis of C2GnT1 expression in short-term cultures of activated CD8 T cells, we recently reported that C2GnT1 could be effectively regulated by cytokines (20). Supplementing cultures with IL-2 efficiently induced high levels of C2GnT1 enzyme activity, whereas IL-4 supplements supported T cell expansion comparably without inducing C2GnT1. This differential C2GnT1 enzyme induction activity was paralleled by differential glycosylation of known C2GnT1 substrates in activated CD8 T cells. Notably, the effects of these cytokines on C2GnT1 expression were manifested relatively quickly within a 4-day activation/expansion of T cells isolated from spleen or lymph node.
The ability to modify C2GnT1 activity in parallel primary cultures supplemented with IL-2 vs IL-4 afforded a simple method to test whether lactosamines on branched O-glycans would alter galectin 1-mediated killing in T cells. Lymphocytes from normal or C2GnT1-deficient mice together with the N-glycan inhibitor swainsonine were applied with this simple culture system to explore galectin 1 killing in primary cultured murine T cells. Specifically, our goal was to assess the contribution of O- or N-linked lactosamine extensions on galectin 1-mediated killing of activated murine CD8 T cells.
|
Materials and Methods |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Mice ages 9–16 wk were used for analyses. C57BL/6 mice were bred at the Biomedical Research Centre from founders obtained originally from The Jackson Laboratory (Bar Harbor, ME). CD43-/- mice (21) backcrossed for eight generations with C57BL/6 mice (22) were used. C2GnT1null mice were kindly provided by Drs. J. Marth and L. Ellies (Howard Hughes Medical Institute, University of California, San Diego, CA) (14).
Media
Cell suspensions were prepared in RPMI medium (Life Technologies, Burlington, Ontario, Canada) supplemented with 10% FCS, 5 x 10-5 M 2-ME, 100 U/ml penicillin, 100 U/ml streptomycin (StemCell Technologies, Vancouver, BC, Canada), and 2 mM glutamine (Sigma-Aldrich, St. Louis, MO). Staining with biotinylated reagents for flow analysis was performed in DMEM (Life Technologies) supplemented with 2.5% FCS.
Staining reagents and flow cytometry
Abs were obtained from the following sources: 1B11-PE (BD PharMingen, San Diego, CA; 09695A) and CD8
FITC (BD PharMingen; 01044D). For cell surface staining, cells were suspended in DMEM containing 5% (v/v) FCS and incubated with Abs for 20–40 min on ice in Nunclon 96-well round-bottom plates (VWR, West Chester, PA). Cells were washed twice and analyzed on a FACScan IV flow cytometer (BD Biosciences, Mountain View, CA). Human IgG1-P-selectin fusion protein (BD PharMingen; 28111A) was detected with biotinylated anti-human IgG (Jackson ImmunoResearch, West Grove, PA; 109-065-098) and CyChrome-conjugated steptavidin (BD PharMingen; 554062). Galectin 1 was conjugated with either biotin using polyethylene oxide-maleimide reagent (21901; Pierce, Rockford, IL) or AlexaFluor 488 C5 maleimide (A-10254; Molecular Probes, Eugene, OR), according to supplier’s instructions. For staining, 100 µl of 5–10 µM conjugated galectin was incubated with 105 cells in DMEM with 2 mM DTT (Sigma-Aldrich; D-5545), ± lactose where indicated, for 20 min at room temperature in a 96-well flat-bottom plate. When biotinylated galectin 1 was used, cells were resuspended to 300 µl, transferred to a 5-ml test tube, pelleted washed with 4 ml of DMEM + DTT, and incubated with SA-CyC in, DMEM + DTT for 5 min, followed by another 4-ml wash and flow analysis.
Lymphocyte cultures
Leukocyte cultures were performed, as previously described (20). Briefly, primary stimulations were conducted with spleen cells cultured at 106/ml in 4 µg/ml Con A (Sigma-Aldrich; C-0412) for 48 h at 37°C in 5% CO2. Cultures (2 or 10 ml) were prepared in 24-well Falcon 3047 plates or 6-well Falcon 3046 plates, respectively (BD Biosciences). After 48 h, cells were harvested, washed, counted, and replated in secondary cultures at 0.25 x 106/ml with 2.5% IL-2 supernatants or at 0.05 x 106/ml with 2.5% IL-4 supernatants for optimum differential induction of C2GnT1. IL-2 and IL-4 were obtained as conditioned medium from the myeloma X.653 transfected with the cDNAs for murine IL-2 and IL-4, respectively (F. Melchers; Basel Institute of Immunology, Basel, Switzerland).
Galectin purification
The cDNA for rat galectin 1 was kindly provided by H. Leffler (Lund University, Lund, Sweden) in Escherichia coli BL21 in pET3 days. For galectin 1 preparation, an individual ampicillin-resistant bacterial colony was inoculated into 50 ml in Luria-Bertani medium supplemented with ampicillin (70 µg/ml) and grown to late log phase. This culture was then used to inoculate 2 x 500-ml Luria-Bertani cultures containing 70 µg/ml ampicillin and grown overnight at 37°C. The next morning, cells were harvested by centrifugation for 15 min at 4°C, washed once, and resuspended in 30–40 ml of cold MEPBS (PBS plus 2 mM EDTA + 4 mM 2-ME). The suspension was then frozen at -70°C to facilitate cell lysis. Samples were thawed and sonicated 5 x 30 s in 4 x 10 ml in small glass beakers. Lysates were centrifuged for 20 min at 4°C in polycarbonate tubes in a SS-34 Sorvall rotor. Cleared lysates were passed through a 0.45-µm filter, and EDTA (4 mM final) and 2-ME (8 mM final) were added. Galectin 1 was purified by column chromatography with a lactose agarose matrix (Sigma-Aldrich; L7634) at 4°C. The lactosyl-Sepharose columns were equilibrated with PBS containing 4 mM EDTA and 8 mM 2-ME, and samples were passed through the column once. The column was briefly washed with 2-column volumes of PBS plus 4 mM EDTA and 8 mM 2-ME. Galectin 1 was eluted with water in 10 x 1-ml fractions. Columns were cleaned for reuse with MEPBS plus 100 mM lactose to elute residual bound material. Columns were then rinsed with water and re-equilibrated and stored in PBS plus 0.02% Na-azide. Protein concentration in fractions was measured by OD280, and the purity of galectin was assessed by SDS-PAGE (15%) and silver staining. Fractions containing a heavy enrichment of galectin 1 with minimal evidence of contaminating protein were pooled and dialyzed overnight in serum-free RPMI containing 3 mM DTT using Spectra/Pore dialysis membrane (25218038, molecular weight exclusion 6000–8000). Working concentrations of galectin 1 were specified based on the molecular mass of the dimer (28 kDa) and were generally used at concentrations of 10–20 µM for induction of annexin V ligand.
Galectin 1 treatment and annexin V assay and cell counting
Generally, 2 x 105 cells were plated per flat-bottom well in 96-well tissue culture plates with galectin for 8 h at 37°C and then subjected to staining with anti-CD8 Abs, galectin, and/or annexin V. Media in the 8-h culture included 2–3 mM DTT and 20–50 mM lactose, as indicated. Annexin V-PE staining (BD PharMingen; 65875X) was performed according to manufacturer’s instructions. Briefly, after the 8-h incubation with galectin, cells were transferred to U-bottom plates, diluted with an equal volume of PBS containing 100 mM lactose, washed once in PBS plus 100 mM lactose, and resuspended in 30 µl of 100 mM lactose in DMEM with CD8 FITC for 15 min. Cells were then washed once in PBS lactose, once in PBS, and then stained with annexin V-PE 1:20 in 50 µl of annexin V-binding buffer (10 mM HEPES/NaOH, pH 7.4, 140 mM NaCl, 2.5 mM CaCl2) plus 50 ng/ml propidium iodide (PI) for 20 min on ice. Annexin V staining was evaluated by FACS analysis. Where indicated, 100 µl of 10-µm latex beads (2-1000; Interfacial Dynamics, Portland, OR) diluted to 105/ml in annexin V-binding buffer was added to samples just before flow analysis to determine the ratio of events:beads. Because volumes were constant, this ratio was directly proportional to event count.
Swainsonine treatment and PHA-biotin staining
Where indicated, swainsonine (Sigma-Aldrich; S-9263) was included in the 48-h secondary culture medium at a concentration of 1 µg/ml from a sterile stock solution of 500 µg/ml in water. Staining with PHA-biotin was used to assess swainsonine efficacy. PHA-biotin (Sigma-Aldrich; L7019) was used for cell surface staining at 2 µg/ml in DMEM + BSA (1 mg/ml) and detected with CyChrome-conjugated steptavidin (BD PharMingen; 554062).
|
Results |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
To demonstrate that galectin 1 induction of annexin V ligand proceeded as had been reported in activated human T cells, day 4 murine Con A-activated CD8+ blasts were exposed to galectin 1 and assessed for annexin V staining. After 7.5- to 8-h incubation, the majority of CD8+ T cells became annexin V+ in the presence of both DTT and galectin 1, as shown in Fig. 1A. Annexin V ligand was not induced significantly by galectin in shorter 5-h assays. When lactose was included in the assay, both aggregation (data not shown) and formation of annexin V ligand were effectively blocked, demonstrating the carbohydrate dependence of ligand induction by galectin.
|
Cytokines modulate lactosamine-containing O-glycans, but do not affect annexin V ligand induction by galectin 1
Lactosamine sequences are considered to be the preferred ligands for galectin 1 and, when present in lymphocyte O-glycans, they reside in branched structures arising through the action of C2GnT1 (23). P-selectin (P-Sel) binding to activated T cells is dependent on C2GnT1 branching and subsequent modifications of P-selectin alycoprotein ligand-1 expressed on the T-cell surface. For example, C2GnT1null lymphocytes lack branched O-glycans (14, 24), and therefore lack the lactosamine sequences required for formation of P-selectin ligand (P-SelL) on activated CD8 T cells (20). As shown in Fig. 2A, P-SelL expression was influenced by cytokine exposure. IL-2 promoted significantly higher levels of P-SelL staining relative to IL-4, as described previously (20).
|
If galectin 1 induction of annexin V ligand on CD8 T cells occurs primarily through its affinity for lactosamine residues within branched O-glycans generated by C2GnT1, then activated CD8 T cells, cultured as described in Fig. 2B, should exhibit relative susceptibility to galectin 1. CD8 T cells cultured at high density for 4 days with IL-2 should be more susceptible to galectin 1 action than CD8 cells grown at low density in IL-4. As shown in Fig. 2C, cells grown in IL-4 and IL-2 exhibited comparable susceptibility to induction of annexin V ligand. Furthermore, C2GnT1null CD8 T cells from parallel IL-2-supplemented cultures retained comparable galectin 1 susceptibility. Thus, galectin 1 induction of annexin V ligand in activated murine CD8 T cells was not a simple correlate of C2GnT1 activity.
Annexin V induction by galectin 1 is paralleled by reduced viable cell recovery
To further characterize galectin impact on cell survival, we enumerated CD8+ events detected by flow cytometry that were distinguished by light scatter properties or staining with annexin V and PI. CD8+ T cells distinguished by these criteria were enumerated by a flow-counting assay whereby a known quantity of latex beads is combined with samples such that the ratio of events:beads was proportional to event concentration in the initial suspension (see Materials and Methods). As shown in Fig. 3, A and C, there was a significant increase in CD8+ annexin V+ PI- T cells after galectin 1 treatment for 8 h. There was also an increase in PI+ events, but this increase was less dramatic and less consistent when all cell types were considered, as summarized in Fig. 3H. Annexin V+ PI- events predominantly fell into the forward light scatter (FSC)high region shared with viable annexin- PI- events, while PI+ events exhibited reduced FSC properties, as expected (Fig. 3, C, E, F, and G). Thus, induction of annexin V ligand could be measured by applying gating based on either FSChigh or FSChigh + FSClow light scatter properties.
|
Blocking formation of N-glycan lactosamine extensions fails to alter galectin 1-induced annexin V ligand
In view of our failure to observe altered galectin-induced annexinV ligand expression in activated murine CD8 T cells when C2GnT1 activity was reduced or eliminated, we investigated whether inhibitors of lactosamine formation on N-glycans would affect relevant galectin ligands. Galectin ligands on N-glycans had been previously implicated in galectin-induced apoptosis of PHA-activated human T cells through use of the mannosidase II inhibitor swainsonine (8). Swainsonine partially blocks glycan extension from the mannose core structure such that cells treated with swainsonine express predominantly high mannose and hybrid N-glycans, but lack complex N-glycans (26). Cultures were supplemented with swainsonine throughout the 2-day secondary culture with either IL-2 or IL-4 and, as shown in Fig. 4A, the efficacy of swainsonine treatment was monitored by loss of PHA binding to cell surface complex N-glycans on day 4. Despite its efficacy in eliminating PHA staining, swainsonine had no significant impact on galectin 1-induced annexin V ligand expression by activated CD8 T cells, as shown in Fig. 4B.
|
Annexin V staining after galectin treatment suggested that CD8 T cells cultured in IL-4 exhibited marginally enhanced susceptibility to apoptosis relative to cells cultured in IL-2. This result was unexpected because previous studies demonstrated that IL-2 strongly promoted C2GnT1 expression and branched O-glycan formation on prototype cell surface mucins CD43, CD45, as well as P-selectin glycoprotein ligand 1; IL-4 supported C2GnT1 enzyme activity and function weakly, if at all. The high level of annexin V staining observed in IL-4-cultured cells after galectin treatment suggested that either these cells expressed comparable (or even increased) levels of total cell surface galectin ligand relative to cells cultured with IL-2, or that only the relevant galectin ligand involved in apoptosis was maintained, while total cell surface galectin ligand expression was reduced in parallel with changes induced in O- or N-glycans by cytokines or swainsonine. To determine which of these possibilities applied, direct assessment of galectin binding was used to measure relative quantities of ligand on cells cultured with cytokines or swainsonine. The results of galectin and PHA binding shown in Fig. 5A indicated that CD8 T cells maintained in IL-4 and exhibited high susceptibility to apoptosis also expressed uniformly high levels of galectin ligand. Swainsonine had no significant impact on galectin binding consistent with its failure to alter susceptibility to apoptosis. Thus, galectin 1 ligand expression appeared to be essentially independent both of O-glycan lactosamines substituted on branched O-glycans and of complex N-glycans.
|
|
Discussion |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
We observed that galectin 1 did indeed induce expression of annexin V ligand in activated murine CD8 T cells. This process was dependent on sufficient concentrations of DTT and was inhibited by lactose, thereby implicating the carbohydrate-binding specificity of galectin. However, neither in vitro modulation of C2GnT1 O-glycan-branching activity with cytokines nor genetic elimination of C2GnT1-branching activity altered the efficiency of annexin V ligand induction by galectin 1. These observations were consistent with the ability of galectin 1 to induce annexin V ligand on activated human T cells (8), but were not consistent with the general concept that C2GnT1-branched O-glycans constitute the relevant target of galectin 1, at least with respect to murine CD8 T cells. Our observations instead suggest that ligands other than C2GnT1-branched O-glycans are most relevant in action of galectin 1 on activated murine CD8 cells.
What then, are the relevant ligands for galectin on activated murine CD8 cells? The inhibition of galectin binding, the inhibition of annexin V ligand expression, and inhibition of aggregation (aggregation data not shown) that we observed with 20–100 mM lactose were consistent with the recognized specificity of galectin for lactose and lactosamine sequences (4). Another disaccharide, sucrose, failed to block galectin binding at similar 100 mM concentrations, thereby confirming that residues of lactose or some related structures are indeed relevant in galectin binding to the cell surface (data not shown). Although other unidentified carbohydrate ligands may be involved, these observations are most consistent with a simple model, whereby galectin bound lactose/lactosamine moieties residing on cell surface molecules and initiated signaling events leading to expression of annexin V ligand. The question of galectin ligand identity thus becomes focused on those structures known to carry lactosyl moieties.
In terms of O-glycans, activated murine CD8 T cells subcultured with IL-4 were marginally more susceptible to galectin binding and annexin V induction than parallel cultures supplemented with IL-2. Previous investigations have demonstrated that activated CD8 T cells cultured with IL-4 express much lower C2GnT1 enzyme activity and predominantly unbranched O-glycans on physiological substrates CD43 and CD45 in vivo (20). The only other potential sources of lactosamine residues in O-glycans would be those contained within core 1 extensions or in O-glycan branches generated by other C2GnT isoenzymes (C2GnT2 and C2GnT3). However, significant contributions of extended core 1 structures have not been detected in activated lymphocytes (23), although they have been observed in high endothelial venules of C2GnT1null mice (24), where they contribute to the L-selectin ligand formation and thereby support homing of naive T cells to lymphoid organs. To our knowledge, no evidence of residual C2GnT activity in mature C2GnT1null lymphocytes has been reported. Furthermore, C2GnT2 and C2GnT3 do not replace C2GnT1 to a detectable extent in either HEV (24) or splenocytes (14). Therefore, the failure of C2GnT1 to affect galectin 1 induction of annexin V in activated murine CD8 T cells is most easily explained by the irrelevance of core 2-branched O-glycans in this process.
One explanation to account for the discrepancy between this conclusion and previous observations (8) is that galectin 1 induction of apoptosis in activated human T cells is reported to be primarily determined through interactions with human CD7 (hCD7) 3 (27). Comparing sites of predicted O-glycan substitution using Net-O-Glycan (28), one finds that the extracellular portion of hCD7 may be extensively substituted at Ser/Thr36, Ser/Thr150, Ser/Thr157, Ser/Thr159, Ser/Thr168, Ser/Thr166, and Ser/Thr177 (transmembrane domain aa 178:200), whereas murine CD7 (mCD7) has a single juxtamembrane-predicted site of O-glycan modification at Ser139 (transmembrane domain aa 149:171). If O-glycans on CD7 are indeed relevant targets of galectin 1 in activated human T cells that are absent in mCD7, and these predicted sites of O-glycan modification in hCD7 and mCD7 reflect true glycosylation differences, this could account for both our failure to implicate O-glycans in annexin V induction by galectin 1 and the frank absence of data implicating O-glycans in galectin 1-induced apoptosis in primary activated murine T cells. To our knowledge, the only evidence that O-glycans support galectin 1-induced apoptosis in peripheral murine T cells is based upon C2GnT1 overexpression studies in murine T cell lines (9, 29).
Inhibition of complex N-glycans had no effect on ability of galectin to induce annexin V in our analysis. The failure of swainsonine to detectably alter susceptibility to annexin V induction in activated murine CD8 T cells described in this work contrasts with results reported for activated human T cells (8). The rationale for using swainsonine in both previous studies and our current study is that swainsonine is tolerated relatively well by cells and the drug is highly effective at blocking expression of complex N-glycans. However, interpretation of swainsonine inhibition data is compromised, as clear evidence exists that formation of hybrid N-glycans containing polylactosamine sequences is not impeded by this drug (30, 31). Hence, swainsonine in fact only partially prevents expression of lactosamine-containing N-glycans. Other drugs such as deoxymannojirimycin can fully prevent extensions off the mannose core structure, but its application may be limited by toxicity and interference with surface expression/secretion of particular proteins (31). The fact that no reduction in galectin 1 labeling was evident after treatment with swainsonine is consistent with its failure to affect annexin V induction and strongly suggests that those N-glycans blocked by swainsonine are not ligands for galectin 1 in murine CD8 T cells. Whether remaining N-glycan extensions represent relevant galectin ligands was not addressed in this study, but has found some support in recent observations by others (18).
Another potential ligand for galectin 1 on CD8 T cells is the glycolipid GM1, a ganglioside bearing the 2,3 sialylated lactosyl sequence and a known ligand of galectin 1 in other cell systems (32). GM1 cross-linking with B subunits of either E. coli enterotoxin (EtxB) or cholera toxin (Ctx) induces GM1 capping, and ETxB reportedly induces apoptosis in activated murine CD8 T cells (33). Importantly, Ctx binding of GM1 interferes with lectin-mediated stimulation of lymphocytes (34). We attempted to block galectin 1 (7 µM dimer) binding to CD8 T cells with Ctx (25 µM monomer, 5 µM pentamer) in efforts to implicate GM1 in the process of annexin V ligand induction. Ctx did not alter lactose-dependent galectin binding to activated CD8 T cells detectably (data not shown).
In summary, we have found that C2GnT1 modifications of O-glycans do not appear to affect galectin 1 binding or annexin V ligand induction in activated murine CD8 T cells. These results are difficult to reconcile with the proposal that contraction of the poststimulation T cell pool depends on apoptosis induced by endogenous galectin 1 binding to lactosyl sequences forming on branched O- or N-linked gylcans, at least in the murine model. Although our data demonstrate that galectin 1 can effectively promote annexin V ligand expression in activated murine CD8 T cells and that this process relies on lactosyl specificity of galectin, we have not identified the relevant lactosyl-bearing targets. Specifically, our data suggest that O-glycans are in fact not relevant in galectin 1 action because potential galectin ligands arising through formation of core 1 extensions are highly unlikely and C2GnT branching in activated murine T cells is apparently dispensable.
|
Acknowledgments |
|---|
|
Footnotes |
|---|
2 Address correspondence and reprint requests to Dr. Douglas A. Carlow, The Biomedical Research Centre, University of British Columbia, 2222 Health Sciences Mall, Vancouver, British Columbia V6T-1Z3 Canada. E-mail address: doug{at}brc.ubc.ca
3 Abbreviations used in this paper: hCD7, human CD7; Ctx, cholera toxin; FSC, forward light scatter; mCD7, murine CD7; P-SelL, •••; PI, propidium iodide; SSC, side scatter; C2GnT1, (1-6)N-acetyl glucosaminyl transferase I; P-SelL, P-selectin ligand.
Received for publication March 24, 2003. Accepted for publication September 3, 2003.
|
References |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
-galactosides. J. Biol. Chem. 261:10119.-galactoside-binding lectin in Chinese hamster ovary cells. I. Physical and chemical characterization. J. Biol. Chem. 270:5198.-galactoside-binding lectin. J. Biol. Chem. 266:23648.-Galactoside-binding protein secreted by activated T cells inhibits antigen-induced proliferation of T cells. Eur. J. Immunol. 28:2311.[Medline]
-galactoside-binding lectin. J. Biochem. 122:365.-galactoside binding protein ( GBP): induction of programmed cell death in leukemic cells. J. Cell. Physiol. 178:102.[Medline]
1, 3-N-acetylglucosaminyltransferase. Cell 105:957.[Medline]
This article has been cited by other articles:
|
|
 |
|
  S. R. Stowell, S. Karmakar, C. M. Arthur, T. Ju, L. C. Rodrigues, T. B. Riul, M. Dias-Baruffi, J. Miner, R. P. McEver, and R. D. Cummings Galectin-1 Induces Reversible Phosphatidylserine Exposure at the Plasma Membrane Mol. Biol. Cell, March 1, 2009; 20(5): 1408 - 1418. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. R. Stowell, M. Cho, C. L. Feasley, C. M. Arthur, X. Song, J. K. Colucci, S. Karmakar, P. Mehta, M. Dias-Baruffi, R. P. McEver, et al. Ligand Reduces Galectin-1 Sensitivity to Oxidative Inactivation by Enhancing Dimer Formation J. Biol. Chem., February 20, 2009; 284(8): 4989 - 4999. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Karmakar, S. R Stowell, R. D Cummings, and R. P McEver Galectin-1 signaling in leukocytes requires expression of complex-type N-glycans Glycobiology, October 1, 2008; 18(10): 770 - 778. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. R. Stowell, S. Karmakar, C. J. Stowell, M. Dias-Baruffi, R. P. McEver, and R. D. Cummings Human galectin-1, -2, and -4 induce surface exposure of phosphatidylserine in activated human neutrophils but not in activated T cells Blood, January 1, 2007; 109(1): 219 - 227. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
I. Camby, M. Le Mercier, F. Lefranc, and R. Kiss Galectin-1: a small protein with major functions Glycobiology, November 1, 2006; 16(11): 137R - 157R. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. K. Patnaik, B. Potvin, S. Carlsson, D. Sturm, H. Leffler, and P. Stanley Complex N-glycans are the major ligands for galectin-1, -3, and -8 on Chinese hamster ovary cells Glycobiology, April 1, 2006; 16(4): 305 - 317. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. A. Carlow, M. J. Williams, and H. J. Ziltener Inducing P-Selectin Ligand Formation in CD8 T Cells: IL-2 and IL-12 Are Active In Vitro but Not Required In Vivo J. Immunol., April 1, 2005; 174(7): 3959 - 3966. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Leppanen, S. Stowell, O. Blixt, and R. D. Cummings Dimeric Galectin-1 Binds with High Affinity to {alpha}2,3-Sialylated and Non-sialylated Terminal N-Acetyllactosamine Units on Surface-bound Extended Glycans J. Biol. Chem., February 18, 2005; 280(7): 5549 - 5562. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Sturm, M. Lensch, S. Andre, H. Kaltner, B. Wiedenmann, S. Rosewicz, A. U. Dignass, and H.-J. Gabius Human Galectin-2: Novel Inducer of T Cell Apoptosis with Distinct Profile of Caspase Activation J. Immunol., September 15, 2004; 173(6): 3825 - 3837. [Abstract] [Full Text] [PDF]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
