Showing papers on "Galectin published in 2006"

Galectin-1: A Small Protein with Major Functions

Abstract: Galectins are a family of carbohydrate-binding proteins with an affinity for beta-galactosides. Galectin-1 (Gal-1) is differentially expressed by various normal and pathological tissues and appears to be functionally polyvalent, with a wide range of biological activity. The intracellular and extracellular activity of Gal-1 has been described. Evidence points to Gal-1 and its ligands as one of the master regulators of such immune responses as T-cell homeostasis and survival, T-cell immune disorders, inflammation and allergies as well as host-pathogen interactions. Gal-1 expression or overexpression in tumors and/or the tissue surrounding them must be considered as a sign of the malignant tumor progression that is often related to the long-range dissemination of tumoral cells (metastasis), to their dissemination into the surrounding normal tissue, and to tumor immune-escape. Gal-1 in its oxidized form plays a number of important roles in the regeneration of the central nervous system after injury. The targeted overexpression (or delivery) of Gal-1 should be considered as a method of choice for the treatment of some kinds of inflammation-related diseases, neurodegenerative pathologies and muscular dystrophies. In contrast, the targeted inhibition of Gal-1 expression is what should be developed for therapeutic applications against cancer progression. Gal-1 is thus a promising molecular target for the development of new and original therapeutic tools.

Galectin-3 and galectin-1 bind distinct cell surface glycoprotein receptors to induce T cell death.

Abstract: Galectins are a family of mammalian β-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.

Exosomes released by EBV-infected nasopharyngeal carcinoma cells convey the viral Latent Membrane Protein 1 and the immunomodulatory protein galectin 9

Abstract: Background Nasopharyngeal carcinomas (NPC) are consistently associated with the Epstein-Barr virus (EBV). Their malignant epithelial cells contain the viral genome and express several antigenic viral proteins. However, the mechanisms of immune escape in NPCs are still poorly understood. EBV-transformed B-cells have been reported to release exosomes carrying the EBV-encoded latent membrane protein 1 (LMP1) which has T-cell inhibitory activity. Although this report suggested that NPC cells could also produce exosomes carrying immunosuppressive proteins, this hypothesis has remained so far untested.

Galectin-3 Induces Death of Candida Species Expressing Specific β-1,2-Linked Mannans

Abstract: Lectins play a critical role in host protection against infection. The galectin family of lectins recognizes saccharide ligands on a variety of microbial pathogens, including viruses, bacteria, and parasites. Galectin-3, a galectin expressed by macrophages, dendritic cells, and epithelial cells, binds bacterial and parasitic pathogens including Leishmania major, Trypanosoma cruzi, and Neisseria gonorrhoeae. However, there have been no reports of galectins having direct effects on microbial viability. We found that galectin-3 bound only to Candida albicans species that bear β-1,2-linked oligomannans on the cell surface, but did not bind Saccharomyces cerevisiae that lacks β-1,2-linked oligomannans. Surprisingly, binding directly induced death of Candida species containing specific β-1,2-linked oligomannosides. Thus, galectin-3 can act as a pattern recognition receptor that recognizes a unique pathogen-specific oligosaccharide sequence. This is the first description of antimicrobial activity for a member of the galectin family of mammalian lectins; unlike other lectins of the innate immune system that promote opsonization and phagocytosis, galectin-3 has direct fungicidal activity against opportunistic fungal pathogens.

Galectin Binding to Mgat5-Modified N-Glycans Regulates Fibronectin Matrix Remodeling in Tumor Cells

Abstract: Oncogenic signaling stimulates the dynamic remodeling of actin microfilaments and substrate adhesions, essential for cell spreading and motility. Transformation is associated with increased expression of beta1,6GlcNAc-branched N-glycans, products of Golgi beta1,6-acetylglucosaminyltransferase V (Mgat5) and the favored ligand for galectins. Herein we report that fibronectin fibrillogenesis and fibronectin-dependent cell spreading are deficient in Mgat5(-/-) mammary epithelial tumor cells and inhibited in Mgat5(+/+) cells by blocking Golgi N-glycan processing with swainsonine or by competitive inhibition of galectin binding. At an optimum dosage, exogenous galectin-3 added to Mgat5(+/+) cells activates focal adhesion kinase (FAK) and phosphatidylinositol 3-kinase (PI3K), recruits conformationally active alpha5beta1-integrin to fibrillar adhesions, and increases F-actin turnover. RGD peptide inhibits PI3K-dependent fibronectin matrix remodeling and fibronectin-dependent cell motility, while galectin-3 stimulates and overrides the inhibitory effects of RGD. Antibodies to the galectin-3 N-terminal oligomerization domain stimulate alpha5beta1 activation and recruitment to fibrillar adhesions in Mgat5(+/+) cells, an effect that is blocked by disrupting galectin-glycan binding. Our results demonstrate that fibronectin polymerization and tumor cell motility are regulated by galectin-3 binding to branched N-glycan ligands that stimulate focal adhesion remodeling, FAK and PI3K activation, local F-actin instability, and alpha5beta1 translocation to fibrillar adhesions.

Galectins are differentially expressed in supratentorial pilocytic astrocytomas, astrocytomas, anaplastic astrocytomas and glioblastomas, and significantly modulate tumor astrocyte migration.

Abstract: Galectins, a family of mammalian lectins with specificity to beta-galactosides, are involved in growth-regulatory mechanisms and cell adhesion. A relationship is assumed to exist between the levels of expression of galectins and the level of malignancy in human gliomas. A comparative study of this aspect in the same series of clinical samples is required to prove this hypothesis. Using computer-assisted microscopy, we quantitatively characterized by immunohistochemistry the levels of expression of galectins-1, -3 and -8 in 116 human astrocytic tumors of grades I to IV. Extent of transcription of galectins-1, -3, and -8 genes was investigated in 8 human glioblastoma cell lines by means of RT-PCR techniques. Three of these cell lines were grafted into the brains of nude mice in order to characterize in vivo the galectins-1, -3 and -8 expression in relation to the patterns of the tumor invasion of the brain. The role of galectin-1, -3 and -8 in tumor astrocyte migration was quantitatively determined in vitro by means of computer-assisted phase-contrast videomicroscopy. The data indicate that the levels of galectin-1 and galectin-3 expression significantly change during the progression of malignancy in human astrocytic tumors, while that of galectin-8 remains unchanged. These three galectins are involved in tumor astrocyte invasion of the brain parenchyma since their levels of expression are higher in the invasive parts of xenografted glioblastomas than in their less invasive parts. Galectin-3, galectin-1, and to a lesser extent galectin-8, markedly stimulate glioblastoma cell migration in vitro. Since bands for the transcripts of human galectins-2, -4 and -9 were apparently less frequent and intense in the 8 human glioblastoma cell lines, this system provides an excellent model to assign defined roles to individual galectins and delineate overlapping and distinct functional aspects.

Complex N-glycans are the major ligands for galectin-1, -3, and -8 on Chinese hamster ovary cells.

Abstract: Galectins are implicated in a large variety of biological functions, many of which depend on their carbohydrate-binding ability. Fifteen members of the family have been identified in vertebrates based on binding to galactose (Gal) that is mediated by one or two, evolutionarily conserved, carbohydrate-recognition domains (CRDs). Variations in glycan structures expressed on glycoconjugates at the cell surface may, therefore, affect galectin binding and functions. To identify roles for different glycans in the binding of the three types of mammalian galectins to cells, we performed fluorescence cytometry at 4 degrees C with recombinant rat galectin-1, human galectin-3, and three forms of human galectin-8, to Chinese hamster ovary (CHO) cells and 12 different CHO glycosylation mutants. All galectin species bound to parent CHO cells and binding was inhibited >90% by 0.2 M lactose. Galectin-8 isoforms with either a long or a short inter-CRD linker bound similarly to CHO cells. However, a truncated form of galectin-8 containing only the N-terminal CRD bound only weakly to CHO cells and the C-terminal galectin-8 CRD exhibited extremely low binding. Binding of the galectins to the different CHO glycosylation mutants revealed that complex N-glycans are the major ligands for each galectin except the N-terminal CRD of galectins-8, and also identified some fine differences in glycan recognition. Interestingly, increased binding of galectin-1 at 4 degrees C correlated with increased propidium iodide (PI) uptake, whereas galectin-3 or -8 binding did not induce permeability to PI. The CHO glycosylation mutants with various repertoires of cell surface glycans are a useful tool for investigating galectin-cell interactions as they present complex and simple glycans in a natural mixture of multivalent protein and lipid glycoconjugates anchored in a cell membrane.

A Guide to Signaling Pathways Connecting Protein-Glycan Interaction with the Emerging Versatile Effector Functionality of Mammalian Lectins

Abstract: The plasma membrane establishes the interface for the communication of cells with the environment. Thus, surface determinants govern the reactivity and capacity of cells to respond to external signals. Changes in their profi le, for example in malignant transformation, and manifestation of cell-type-specific features apparently hold inspiring lessons in store for us on how they are translated into cellular responses. But before turning to the signaling routes the biochemical modes for coding signals warrant a comment, as proteins are often unduly portrayed as the decisive hardware. In contrast, and actually prominent among the biochemical systems to store information, carbohydrate epitopes of cellular glycoconjugates favorably combine high-density coding with strategic positioning, rendering them readily accessible for interactions with adaptor molecules. The interaction with lectins is the ignition key to start glycoconjugate-mediated biosignaling. Several plant lectins, especially due to their mitogenicity, have become a popular type of laboratory tool to elicit cell responses and to analyze biochemical pathways leading from initial binding to measured activity such as enhanced proliferation. With emerging insights into the roles of mammalian (endogenous) lectins and the promising perspective for medical applications, emphasis in this area is shifting from model studies with plant proteins toward work with the physiological effectors. By targeting branch- end epitopes of glycan chains two classes of endogenous lectins, i.e. galectins and selectins, are remarkably well suited to establish initial contacts with the cell surface. Indeed, these lectins - in their interplay with certain cognate - in their interplay with certain cognate -

Synthetic lactulose amines: novel class of anticancer agents that induce tumor-cell apoptosis and inhibit galectin-mediated homotypic cell aggregation and endothelial cell morphogenesis

Abstract: Galectins, a family of structurally related carbohydrate-binding proteins, contribute to different events associated with cancer biology, including apoptosis, homotypic cell aggregation, angiogenesis and tumor-immune escape. To interfere with galectin-carbohydrate interactions during tumor progression, a current challenge is the design of specific galectin inhibitors for therapeutic purposes. Here, we report the synthesis of three novel low molecular weight synthetic lactulose amines (SLA): (1) N-lactulose-octamethylenediamine (LDO), (2) N,N'-dilactulose-octamethylenediamine (D-LDO), and (3) N,N'-dilactulose-dodecamethylenediamine (D-LDD). These compounds showed a differential ability to inhibit binding of galectin-1 and/or galectin-3 to the highly glycosylated protein 90K in solid-phase assays. In addition, each compound demonstrated selective regulatory effects in different events linked to tumor progression including tumor-cell apoptosis, homotypic cell aggregation, and endothelial cell morphogenesis. Our results suggest that galectin inhibitors with subtle differences in their carbohydrate structures may be potentially used to specifically block different steps of tumor growth and metastasis.

Anti-galectin compounds as potential anti-cancer drugs.

Abstract: Galectins form a family of carbohydrate-binding proteins defined by their affinity for beta-galactosides containing glycoconjugates. The carbohydrate recognition domain (CRD) is responsible for the specificity of galectins for saccharides. This binding may result in modulated cell proliferation, cell death and cell migration, three processes that are intimately involved in cancer initiation and progression. Galectins can also display protein-protein types of interactions with their binding partners. Certain galectins directly involved in cancer progression seem to be promising targets for the development of novel therapeutic strategies to combat cancer. Indeed, migrating cancer cells resistant to apoptosis still constitute the principal target for the cytotoxic drugs used to treat cancer patients. Reducing the levels of migration in apoptosis-resistant cancer cells can restore certain levels of sensitivity to apoptosis (and so to pro-apoptotic drugs) in restricted-migration cancer cells. Anti-galectin agents can restrict the levels of migration of several types of cancer cell and should therefore be used in association with cytotoxic drugs to combat metastatic cancer. We provide experimental proof in support of this concept. While the present review focuses on various experimental strategies to impair cancer progression by targeting certain types of galectins, it pays particular attention to glioblastomas, which constitute the ultimate level of malignancy in primary brain tumors. Glioblastomas form the most common type of malignant brain tumor in children and adults, and no glioblastoma patient has been cured to date.

Galectins in apoptosis.

Abstract: Galectins are a family of animal lectins with affinity for β‐galactosides. By using recombinant proteins, a number of galectins have been shown to interact with cell‐surface and extracellular matrix glycoconjugates through lectin–carbohydrate interactions. Through this action, they can affect a variety of cellular processes, and the most extensively documented function is induction of apoptosis. By using gene transfection approaches, galectins have been shown to regulate various cellular processes, including apoptosis. Evidence has been provided that some of these functions involve binding to cytoplasmic and nuclear proteins, through protein–protein interactions, and modulation of intracellular signaling pathways. Thus, some galectins are pro‐apoptotic, whereas others are anti‐apoptotic; some galectins induce apoptosis by binding to cell surface glycoproteins, whereas others regulate apoptosis through interactions with intracellular proteins. This review describes involvement of galectin‐1, ‐2, ‐3, ‐7, ‐8, ‐9, and ‐12 in apoptosis.

Repression of the Antiapoptotic Molecule Galectin-3 by Homeodomain-Interacting Protein Kinase 2-Activated p53 Is Required for p53-Induced Apoptosis

Abstract: Galectin 3 (Gal-3), a member of the -galactoside binding lectin family, exhibits antiapoptotic functions, and its aberrant expression is involved in various aspects of tumor progression. Here we show that p53-induced apoptosis is associated with transcriptional repression of Gal-3. Previously, it has been reported that phosphorylation of p53 at Ser46 is important for transcription of proapoptotic genes and induction of apoptosis and that homeodomain-interacting protein kinase 2 (HIPK2) is specifically involved in these functions. We show that HIPK2 cooperates with p53 in Gal-3 repression and that this cooperation requires HIPK2 kinase activity. Gene-specific RNA interference demonstrates that HIPK2 is essential for repression of Gal-3 upon induction of p53-dependent apoptosis. Furthermore, expression of a nonrepressible Gal-3 prevents HIPK2- and p53induced apoptosis. These results reveal a new apoptotic pathway induced by HIPK2-activated p53 and requiring repression of the antiapoptotic factor Gal-3. Gal-3 is a -galactoside-specific lectin belonging to a large family of carbohydrate-binding proteins, the galectins, characterized by the presence of at least one carbohydrate recognition domain. Gal-3 possesses a chimeric structure that together with the carbohydrate recognition domain comprises a repetitive collagen-like sequence and a short N-terminal domain regulated by posttranslational modifications (5, 23, 56). Gal-3 is widely expressed in epithelial and immune cells while an aberrant expression is present in a large number of human cancers (reviewed in references 37 and 38). Indeed, in the case of thyroid tumors, Gal-3 overexpression is regarded as a marker of malignancy, and it is currently used in the clinical practice for the preoperative characterization of thyroid nodules (6, 39). At the functional level, Gal-3 is involved in different biological events including pre-mRNA processing, cell

Galectin 7 (p53-induced gene 1): a new prognostic predictor of recurrence and survival in stage IV hypopharyngeal cancer.

Abstract: Eighty percent of hypopharyngeal squamous cell carcinoma patients have advanced stages (III and IV) of the disease, and biological markers are required to predict high-risk head and neck squamous cell carcinoma patients in need of highly aggressive treatments after surgery to improve the survival rate. We analyzed the potential prognostic value of galectin 7 in a series of 81 stage IV hypopharyngeal SCCs because galectin 7 is an emerging marker involved in the epidermal development of pluristratified epithelia and in epidermal cell migration. The immunohistochemical expression of galectin 7 was determined on a series of 81 stage IV hypopharyngeal SCCs and was compared with that of galectins 1 and 3. High levels of galectin 7 expression were associated with rapid recurrence rates and dismal prognoses in these 81 stage IV hypopharyngeal SCCs, a feature not observed with galectin 3 and one observed weakly, if at all, with galectin 1. These data suggest that the immunohistochemical determination of galectin 7 expression in the case of high-risk hypopharyngeal cancers is a meaningful tool to identify patients who should benefit from aggressive postsurgical adjuvant therapy after surgery, including not only radiotherapy, but also chemotherapy.

Characterization of Galectin-9-Induced Death of Jurkat T Cells

Abstract: Galectin-9, a mammalian lectin with affinity for β-galactosides, is known as an apoptosis inducer of activated T lymphocytes. In the present study, we examined the properties of galectin-9-mediated cell death of Jurkat T cells. Galectin-9NC (wild-type), consisting of two CRDs (N-terminal and C-terminal carbohydrate recognition domains), and derivatives of it, galectins-9-NN and -9-CC, induced Jurkat T-cell apoptosis. However, a single CRD (galectin-9NT or -CT) had no effect, suggesting the stable dimeric structure of two CRDs is required for the activity. The apoptosis was inhibited by pretreatment with an N-glycan synthesis inhibitor, indicating that the expression of N-glycans in the cells is essential for galectin-9-induced apoptosis. We previously showed that the apoptosis of MOLT-4 cell is mediated by galectin-9 via a Ca 2+ -calpain-caspase-1-dependent pathway. In Jurkat cells, the cell death by galectin-9, was insufficiently suppressed by caspase inhibitors, Ca 2+ -chelator or calpain inhibitor. Furthermore, we observed the loss of mitochondrial membrane potential and significant AIF release in galectin-9-treated cells. These findings suggest that caspase-dependent and-independent death pathways exist in Jurkat cells, and the main pathway might vary with the T-cell type.

Inhibition and detection of galectins

Abstract: More and more studies report on the roles that galectins play in numerous types of cancer. These roles can be varied, as has been shown particularly for galectin-3. These studies have created the need for inhibitors that can block unwanted effects, and the need to detect galectins in tissues, in order to better understand their role, and aid in diagnosis and prognosis. Since galectins bind beta-galactosides, monovalent galactose-derived inhibitors have been prepared but also peptidic ones have appeared. Since galectins often induce crosslinking and partake in aggregation phenomena, multivalency has been a successful design element in inhibitor development. Currently, there are no cheap and convenient solutions available for the detection of, ideally multiple, galectins in tissue samples, although antibody-based methods such as ELISA and Western blot analysis are being used. Besides these, a chemical probe-based method also shows potential as an alternative.

Galectin interactions with extracellular matrix and effects on cellular function.

Abstract: In vivo, cells exist within a complex mixture of glycoproteins and proteoglycans termed the extracellular matrix (ECM). The components of the ECM are secreted by the cells in that site, and the ECM provides not only a physical support but also outside-in signals that regulate many cellular functions, including cell proliferation, differentiation, migration, and survival. Altering the composition of the ECM can thus significantly alter cell behavior. Many types of cells, including normal and malignant epithelial and mesenchymal cells, secrete galectin-1, a member of the galectin family of lectins, into the ECM surrounding the cells. Galectin-1 is known to regulate many of these same cellular functions (i.e., proliferation, differentiation, migration, and death), so that the presence of galectin-1 in ECM will modify the effects of ECM on cells. In this chapter, we present three types of assays that allow interrogation of the effects of galectin-1 on cell adhesion to ECM, cell migration through ECM, and cell death in ECM, using T-cell lines as a model cell type.

Galectin-3 expression correlates with apoptosis of tumor-associated lymphocytes in human melanoma biopsies.

Abstract: The immune system recognizes diverse melanoma antigens. However, tumors can evade the immune response, therefore growing and progressing. It has been reported that galectin-3 and galectin-1 can induce apoptosis of activated lymphocytes. However, there is strong evidence indicating that the regulation of galectins function in the human tumor microenvironment is a complex process that is influenced by diverse biological circumstances. Here, we have investigated 33 biopsies (eight primary and 25 metastases) from 24 melanoma patients (15–72 years old) and describe the correlation between the expression of galectin-3 or galectin-1 and the level of apoptosis of tumor-associated lymphocytes using immunohistochemistry and an in situ nick translation assay. The range of galectin-3-positive tumor cells varied between 0% and 93% and that of galectin-1-positive tumor cells varied between 5% and 97%. In addition, 23 ± 27% of tumor-associated lymphocytes were apoptotic. Although our results show a correlation between galectin-3 expression and apoptosis of tumor-associated lymphocytes, we could not find such correlation with galectin-1. Considering the complex process of cancer immunoediting, various interacting factors must be considered.

Galectin-1 induces chemokine production and proliferation in pancreatic stellate cells

Abstract: Galectin-1 is a β-galactoside-binding lectin. Previous studies have shown that galectin-1 was expressed in fibroblasts of chronic pancreatitis and of desmoplastic reaction associated with pancreati...

A preliminary proteomic survey of the in vitro excretory/secretory products of fourth-stage larval and adult Teladorsagia circumcincta.

Abstract: The nature of the proteins which comprise the in vitro excretory/secretory products (ES) of the fourth-stage larva (L4) and adult Teladorsagia circumcincta are largely undefined, despite the fact that this nematode induces profound changes, in part related to parasite ES, in the cellular architecture of the glands lining the abomasal surface of infected sheep and goats. In this study, the protein components of L4 and adult ES were fractionated using 1D gel electrophoresis and the major protein bands, detected by Coomassie blue staining, excised from the gel and subjected to tryptic digest and subsequent mass spectrometric analysis. The resultant peptide mass fingerprints were used to identify 15 L4 and 13 adult ES proteins. Several proteins, such as globin and some metabolic enzymes, were present in both ES. L4 ES alone contained thioredoxin peroxidase, an enzyme that can detoxify free radicals resulting from host inflammatory responses to the parasite, a cysteine proteinase which may aid penetration of the gastric mucosa and 2 different galectins which may influence cell differentiation and morphogenesis. Adult ES contained a nucleoside diphosphate kinase homologue, an enzyme which has been linked to cellular changes and can affect liquid secretion and goblet cell degranulation.

Nuclear presence of adhesion-/growth-regulatory galectins in normal/malignant cells of squamous epithelial origin

Abstract: Cellular activities in the regulation of growth or adhesion/migration involve protein (lectin)-carbohydrate recognition at the cell surface. Members of the galectin family of endogenous lectins additionally bind distinct intracellular ligands. These interactions with protein targets explain the relevance of their nuclear and cytoplasmic presence. Expression profiling for galectins and accessible binding sites is a histochemical approach to link localization with cellular growth properties. Non-cross-reactive antibodies for the homodimeric (proto-type) galectins-1, -2 and -7 and the chimera-type galectin-3 (Gal-3) as well as the biotinylated lectins were tested. This analysis was performed with the FaDu squamous carcinoma cell line and long-term cultured human and porcine epidermal cells as models for malignant and normal cells of squamous cell epithelial origin. A set of antibodies was added for phenotypic cell characterization. Strong nuclear and cytoplasmic signals of galectins and the differential reactivity of labeled galectins support the notion of their individual properties. The length of the period of culture was effective in modulating marker expression. Cytochemical expression profiling is a prerequisite for the selection of distinct proteins for targeted modulation of gene expression as a step toward functional analysis.

Reduced Galectin-3 Expression is an Indicator of Unfavorable Prognosis in Gastric Cancer

Abstract: Background: Galectin-3 (gal-3) participates in a variety of biological events, including cell adhesion, proliferation, differentiation and apoptosis. The aim of this study was to determine the relationship of gal-3 expression with clinicopathological findings and prognosis in patients with gastric cancer. Patients and Methods: Gal-3 and Ki-67 expressions were assessed by immunohistochemistry in 115 patients with gastric cancer. PCR-single strand conformation polymorphism (SSCP)-sequence analysis and the levels of gal-3 mRNA were also examined. Results: The present study demonstrated that gal-3 expression was correlated with nodal status, lymphatic invasion, pathological stage and histological parameters. On the other hand, gal-3 expression did not correlate with the expression of Ki-67. Reduced expression of gal-3 was significantly associated with a poor prognosis and multivariate analysis showed that gal-3 expression was an independent prognostic factor. On PCR-SSCP-sequence analysis, 2 single nucleotide polymorphisms (SNPs) were detected in the gal-3 gene, but none showed mutations. Conclusion: Reduced gal-3 expression was associated with lymph node metastasis, advanced stage and tumor differentiation in gastric cancer. Gal-3 expression could be a useful prognostic factor in gastric cancer. Galectin-3 (gal-3), a member of the ‚-galactoside-binding proteins, has been associated with various biological processes, including cell adhesion, recognition, proliferation, differentiation, immunomodulation, angiogenesis and apoptosis. Gal-3 is located in both intracellular and extracellular spaces, such as the cell surface or the extracellular matrix, and its localization is dependent on the tissue, cell type, the proliferative state of the cells and level of differentiation (1). The Galectins are a family of proteins defined by having at least one characteristic carbohydrate-recognition domain (CRD) with an affinity for ‚-galactosides (2). Gal-3 has one CRD joined to a non-CRD domain, which is involved in the oligomerization of gal-3 (3-6). The gal-3 gene has been identified as the macrophage marker 2 protein mapped on human chromosome 14 (14q21-22). This gene is composed of 6 exons and 5 introns and codes for a soluble protein of 30 kDa (7). Exon 1 encodes the 5' untranslated sequence, exons 2-3 encode the N-terminal part of the protein, while exons 4-6 encode the CRD. In vitro, potential ligands for gal-3 include lysosomal-associated membrane proteins 1 and 2 (LAMP-1 and LAMP-2), IgE, laminin, the Mac-2- binding protein and mucin, reflecting the multifunctionality of this molecule (5, 8-10). Recent studies have demonstrated that gal-3 overexpression regulates changes in the expression levels of cell cycle regulators, including cyclin D1 (11) and that the gal-3 complex with beta-catenin activates Tcf-reporter activity and stimulates cyclin D1 (12). In many malignant tissues, the significance of gal-3 expression has been evaluated and some investigators have examined the efficacy of gal-3 as a prognostic marker (13-18). However, the results are unclear because of some conflicting data. In order to determine the relevance of gal-3 in gastric cancer, its expression was investigated by immuno- histochemistry and the prognostic value in patients with gastric cancer was assessed. Furthermore, to confirm the gal-3 expression identified immunohistochemically, the mRNA levels for gal-3 were analyzed. Mutations of LGALS3 (the gal-3 gene) were identified by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP)-sequence analysis, since it was hypothesized that mutations of the gal-3 gene may induce the up- regulation or down-regulation of gal-3 and may be associated with the development of a subset of malignancies. The present study is the first report providing details of a mutation screen for gal-3 in gastric cancer.

Galectin-8 and galectin-9 are novel substrates for thrombin.

Abstract: Galectin-8 and galectin-9, which each consist of two carbohydrate recognition domains (CRDs) joined by a linker peptide, belong to the tandem-repeat-type subclass of the galectin family. Alternative splicing leads to the formation of at least two and three distinct splice variants (isoforms) of galectin-8 and galectin-9, respectively, with tandem-repeat-type structures. The isoforms share identical CRDs and differ only in the linker region. In a search for differences in biological activity among the isoforms, we found that their isoforms with the longest linker peptide, that is, galectin-8L and galectin-9L (G8L and G9L), are highly susceptible to thrombin cleavage, whereas the predominant isoforms, galectin-8M and galectin-9M (G8M and G9M), and other members of human galectin family so far examined were resistant to thrombin. Amino acid sequence analysis of proteolytic fragments and site-directed mutagenesis showed that the thrombin cleavage sites (-IAPRT- and -PRPRG- for G8L and G9L, respectively) resided within the linker peptides. Although intact G8L stimulated neutrophil adhesion to substrate more efficiently than G8M, the activity of G8L but not that of G8M decreased on thrombin digestion. Similarly, thrombin treatment almost completely abolished eosinophil chemoattractant (ECA) activity of G9L. These observations suggest that G8L and G9L play unique roles in relation to coagulation and inflammation.

It Depends on the hinge: A structure-Functional Analysis of Galectin-8, a tandem-repeat type lectin

Abstract: Galectin-8, a member of the galectin family of mammalian lectins, is made of two carbohydrate-recognition domains (CRDs), joined by a "hinge" region. Ligation of integrins by galectin-8 induces a distinct cytoskeletal organization, associated with activation of the extracellular-regulated kinase (ERK) and phosphatidylinositol 3-kinase signaling cascades. We show that these properties of galectin-8 are mediated by the concerted action of its two CRDs and involve both protein-sugar and protein-protein interactions. Accordingly, the isolated N- or C-CRD domains of galectin-8 or galectin-8 mutated at selected residues implicated in sugar binding (E251Q; W85Y, W248Y, W[85,248]Y) exhibited reduced sugar binding, which was accompanied by severe impairment in the capacity of these mutants to promote the adhesive, spreading, and signaling functions of galectin-8. Other mutations that did not impair sugar binding (e.g. E88Q) still impeded the signaling and cell-adherence functions of galectin-8. Deletion of the "hinge" region similarly impaired the biological effects of galectin-8. These results provide evidence that cooperative interactions between the two CRDs and the "hinge" domain are required for the proper functioning of galectin-8.