Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P17931 (galectin-3)
 2,860 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Two carbohydrate-binding proteins with subunit molecular weight of about 17,500 and 16,500, respectively, were isolated from Triton X-100 extracts of rat kidney using a lactose affinity column. They did not require Ca2+ for the carbohydrate-binding nor reducing agents for maintaining their activity. The partial amino acid sequence of the 17.5-kDa protein (rkCBP-17.5), the main component, revealed that this protein is a novel member of a superfamily of beta-galactoside-binding animal lectins. The N-terminal amino acid sequence of the 16.5 kDa component (rkCBP-16.5) indicated that it is a fragment derived from the IgE-binding protein (IgEBP). Monoclonal antibodies to rkCBP-17.5 were prepared and used to examine the distribution of the lectin in various organs of adult rats. Immunoreactive protein with the same molecular weight was found in lung, spleen and liver, in lesser amounts in heart, and in trace amounts in brain and skeletal muscle. rkCBP-17.5 exhibits binding activity to various saccharides with the following order of affinity: N-acetyllactosamine > lactose > D-galactose > methyl alpha-D-galactopyranoside > N-acetyl-D-galactosamine > methyl beta-D-galactopyranoside. It binds to Engelbreth-Holm-Swarm(EHS) tumor laminin and rat plasma fibronectin, but does not bind to human plasma fibronectin.
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PMID:A novel beta-galactoside-binding lectin in adult rat kidney. 785 73

Galectin-3 (M(r) approximately 35,000) is a galactose/lactose-specific lectin found in association with ribonucleoprotein complexes in many animal cells. Cell-free-splicing assays have been carried out to study the requirement for galectin-3 in RNA processing by HeLa cell nuclear extracts by using 32P-labeled MINX as the pre-mRNA substrate. Addition of saccharides that bind galectin-3 with high affinity inhibited product formation in the splicing assay, while addition of carbohydrates that do not bind to the lectin did not inhibit product formation. Nuclear extracts depleted of galectin-3 by affinity adsorption on a lactose-agarose column were deficient in splicing activity. Extracts subjected to parallel adsorption on control cellobiose-agarose retained splicing activity. The activity of the galectin-3-depleted extract could be reconstituted by the addition of purified recombinant galectin-3, whereas the addition of other lectins, either with a similar saccharide binding specificity (soybean agglutinin) or with a different specificity (wheat germ agglutinin), did not restore splicing activity. The formation of splicing complexes was also sensitive to galectin-3 depletion and reconstitution. Together, these results define a requirement for galectin-3 in pre-mRNA splicing and identify it as a splicing factor.
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PMID:Identification of galectin-3 as a factor in pre-mRNA splicing. 786 63

The Mac-2 protein is a lectin specific for galactose-containing glycoconjugates. Present in some normal cells, it was also associated with the metastatic potential of some carcinoma cells. We studied Mac-2 expression in three human melanoma cell lines and in five variants and clones from one of them. By using the M3/38 rat monoclonal antibody, Mac-2 was demonstrated on cell surface by flow cytometry as well as in the cytoplasm and in the nucleus by confocal microscopy. The expression of Mac-2 was not correlated with that of terminal unsialylated Gal beta 1-3 GalNac structures on metastatic melanoma cell lines. However, the presence of extracellular Mac-2 containing vesicles was observed in cell lines with metastatic potency. Western blot analysis of cell lysates, in reducing or non-reducing conditions, revealed two bands of 34-36 and 93-98 kDa apparent M(r), also found in HL60 and P388.D1 cell lines used as positive controls.
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PMID:Expression of the galactose binding protein Mac-2 by human melanoma cell-lines. 801 32

In N mice, peripheral nerve injury is followed by the normal rapid progression of Wallerian degeneration: Schwann cells proliferate and lose their myelin, which is phagocytized and metabolized by blood-borne macrophages. The role of Schwann cells in myelin phagocytosis is debated. Additionally, the molecular mechanisms underlying myelin phagocytosis by the two cell types are not well understood. To elucidate the role of Schwann cells as phagocytes we studied, electron microscopically, in vivo and in vitro degenerating, frozen, and neuroma nerve segments. The major cell types composing these tissues differed: Schwann and macrophages in in vivo degenerating; Schwann in in vitro degenerating; macrophages in frozen; Schwann, macrophages, and fibroblasts in neuroma nerve segments. Both macrophages and Schwann cells phagocytized myelin. We further studied, by immunocytochemistry and immunoblot analysis, the expression of molecules that are characteristically displayed by inflammatory and mature murine macrophages: MAC-1 (the C3b complement receptor), MAC-2 (a galactose-specific lectin), the Fc receptor, and the F4/80 antigen. All were detected in the macrophage-rich, in vivo degenerating, frozen, and neuroma nerve segments. Surprisingly, MAC-2 was also expressed in the macrophage-scarce, Schwann-rich, in vitro degenerating nerve. Immunocytochemistry and immunoblot analysis of isolated non-neuronal cells revealed that both macrophages and Schwann cells displayed MAC-2 on their surface and in their cytoplasm. Morphometry unveiled that galactose and lactose specifically inhibited myelin phagocytosis, as predicted if MAC-2 was mediating myelin phagocytosis by lectinophagocytosis (lectin-mediated phagocytosis). The role of MAC-2 in mediating myelin phagocytosis was further supported by two observations made in W mice that display very slow progression of Wallerian degeneration. First, the failure to degenerate in vivo was associated with deficient MAC-2 production. Second, degeneration that occurred in vitro was associated with MAC-2 production. Furthermore, a strong positive correlation between levels of MAC-2 expression and the extent of myelin destruction by phagocytosis was observed over a wide range of values.
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PMID:Peripheral nerve injury induces Schwann cells to express two macrophage phenotypes: phagocytosis and the galactose-specific lectin MAC-2. 818 68

Macrophage cell-surface protein 2 (Mac-2), a galactose specific S-type lectin identified in inflammatory macrophages, presents a high degree of homology with the rat IgE-binding protein (epsilon BP). In the present study, we show by different experimental approaches that human eosinophils can express Mac-2/epsilon BP. Flow cytometry analysis revealed that a large proportion of eosinophilic patients expressing binding sites for IgE on their eosinophil membrane, were able to bind anti-Mac-2 monoclonal antibody (mAb). Northern blot performed with eosinophil RNA hybridized with the human Mac-2 or epsilon BP cDNA probes revealed that eosinophils presented a unique transcript at 1.2 kb. Immunoprecipitation of eosinophil extracts with anti-Mac-2 mAb revealed the presence of a molecule of 29 kDa corresponding to Mac-2 protein, as well as one additional molecule of 15 kDa, absent from control alveolar macrophages. The function of these molecules was investigated in a radiolabeled IgE binding assay. Anti-Mac-2 mAb as well as galactose and lactose saccharides significantly inhibited the binding of radiolabeled human myeloma IgE protein to eosinophils. Moreover, the dose-dependent inhibition by anti-Mac-2 mAb of IgE-dependent eosinophil-mediated cytotoxicity towards parasite targets indicated the role of these IgE-binding molecules in the function of human eosinophils. These results suggest that in addition to transmembrane receptors, lectin-type molecules can participate in the IgE-dependent effector function of eosinophils.
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PMID:IgE-binding molecules (Mac-2/epsilon BP) expressed by human eosinophils. Implication in IgE-dependent eosinophil cytotoxicity. 825 38

epsilon BP (IgE-binding protein) is a 31,000 M(r) protein originally identified in rat basophilic leukemia (RBL) cells. The protein is composed of two domains with the amino-terminal domain containing a highly conserved repetitive sequence and the carboxyl-terminal domain containing consensus sequences shared by other beta-galactoside-binding soluble lectins. The protein has wide tissue distribution, is found on cell surfaces and in extracellular milieu. By combined efforts from several research groups including ours a multifunctional nature of this lectin began to emerge. This review emphasizes the following characteristics of epsilon BP: (i) epsilon BP is secreted by cells such as macrophages; (ii) like many other lectins, epsilon BP functions at least bivalently; (iii) epsilon BP has specificity for distinct oligosaccharide structures that have a terminal galactose not masked by sialic acids; and (iv) in addition to binding IgE, epsilon BP binds to surfaces of various cell types via lectin-carbohydrate interaction. Importantly, epsilon BP binds to the IgE receptor on mast cells. We propose that epsilon BP can function as a modulatory protein on various cells by cross-linking critical cell surface glycoproteins. The proposed action of epsilon BP on mast cells is presented as a model.
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PMID:Expression and function of an IgE-binding animal lectin (epsilon BP) in mast cells. 828 40

Mac-2, a 30-35-kDa galactose-binding protein, is synthesized at similar levels in murine peritoneal exudate macrophages whether recruited in response to an intraperitoneal pathogen Mycobacterium microti, to sterile inflammatory stimuli such as thioglycollate broth, or to concanavalin A. In elicited or activated macrophages up to 30% of Mac-2 is constitutively secreted, and secretion is stimulated markedly by calcium ionophore A23187. Only thioglycollate-elicited macrophages express cell surface Mac-2, and binding is mostly (> 80%) a result of affinity for cell surface carbohydrate structures. Mac-2 surface expression is markedly reduced upon further activation of thioglycollate-elicited macrophages with bacterial lipopolysaccharide in vitro. Polylactosamine structures are present on all macrophage populations examined as determined by binding of Lycopersicon esculentum lectin, whereas alpha-galactosyl residues detected by Griffonia simplicifolia isolectin B4 are expressed only on the thioglycollate-elicited macrophages, indicating that these residues are the major determinants responsible for Mac-2 surface expression. Chemical cross-linking experiments have identified binding of endogenous cell-surface Mac-2 to three glycoproteins of molecular masses of 92, 125, and 180 kDa containing alpha-galactosyl and polylactosamine structures on thioglycollate-elicited macrophages. The restricted cell surface distribution of Mac-2 on thioglycollate-elicited peritoneal macrophages, a population of recently recruited monocytes, suggests a role(s) in early events of macrophage infiltration and tissue fixation such as extravasion and cell-matrix interactions.
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PMID:Regulation of secretion and surface expression of Mac-2, a galactoside-binding protein of macrophages. 830 13

The carbohydrate binding specificity of recombinant carbohydrate-binding protein 35 (rCBP35) has been investigated by quantitative precipitation using a series of glycoproteins and carbohydrate-protein conjugates and by inhibition of precipitation using well defined carbohydrate haptens. Synthetic glycoconjugates and glycoproteins containing terminal nonreducing galactosyl units in beta-linkage were capable of forming a precipitate with rCBP35. If the glycoprotein or glycoconjugate contained terminal Neu5Ac, or galactose in alpha-linkage, precipitate formation was not observed. We also found that murine laminin, which contains polylactosamine structures, reacted more strongly than did bovine fetuin. Using carbohydrate-bovine serum albumin (BSA) glycoconjugates, we found that the tetrasaccharide Gal beta 1, 4GlcNAc beta 1, 3Gal beta 1,4-GlcNAc-BSA reacted more strongly than the disaccharide Gal beta 1, 4GlcNAc-BSA conjugate, suggesting that the binding site accommodates carbohydrate ligands greater in size than a disaccharide. Equilibrium dialysis experiments using [3H]lactose showed that rCBP35 binds 1 mol (n = 0.84) of lactose/30,000 g atoms of protein, with an affinity constant of 2.07 x 10(4) M-1. The binding site on the polypeptide appears to contain four subsites that recognize the sequence Gal beta 1,4GlcNAc beta 1, Gal beta 1,X-. All disaccharides tested that contain a nonreducing beta-galactosyl unit behaved as inhibitors of precipitation at approximately the same concentration, suggesting that the reducing position of the tetrasaccharide does not play an important role in the specific binding to the fourth subsite. The reducing sugar may serve to hold the saccharide in a tunnel like binding pocket since methyl-beta-D-galactoside itself is an extremely poor inhibitor.
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PMID:Carbohydrate-binding protein 35. II. Analysis of the interaction of the recombinant polypeptide with saccharides. 832 71

The arrangement of carbohydrate molecules on surfaces of fungal cells may play an important role in nonself recognition of these microorganisms by potential invertebrate hosts. Changes in the ability of various galactose and mannose-specific lectins to bind to surface components on cell walls of the insect pathogen Paecilomyces farinosus were therefore examined during growth and differentiation of the fungus. Fluorescein isothiocyanate conjugates of concanavalin A (Con A, specific for alpha-D-mannose) and peanut agglutinin (PNA, beta-D-galactose) bound inconsistently to blastospores and weakly to mycelia except at apical regions where strong fluorescence was observed. Labeling patterns were similar on cells tested with a galactose-specific lectin purified from Spodoptera exigua (beet armyworm) hemolymph, but Bandeiraea simplicifolia lectin (BS-I alpha-D-galactose) bound only to mycelia. Electron microscopy using ferritin and gold probes showed that the galactomannans are located in a loosely bound coating on the cell wall surface. Variations in lectin binding patterns are apparently due to absence (e.g., by shedding) of the coat or to rearrangement of carbohydrate components in the coat. Staining of Western blots of dithiothreitol (DTT) cell wall extracts further indicated that the BS-I-binding entity is a unique component of the mycelial surface since, as in the fluorescence studies, blastospore preparations were not labeled. Staining of blastospore blots with other galactose-specific probes (e.g., PNA) was comparable to staining of mycelial blots.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Variations in the ability of galactose and mannose-specific lectins to bind to cell wall surfaces during growth of the insect pathogenic fungus Paecilomyces farinosus. 833 Jun 30

In vivo cells (hyphal bodies) of the hyphomycetous insect pathogen Beauveria bassiana collected from host Spodoptera exigua larval hemolymph were osmotically sensitive and lacked a well-defined cell wall. In light and electron microscope studies, a galactose-specific lectin purified from S. exigua hemolymph, concanavalin A (specific for alpha-mannose), and a polyclonal antibody to B. bassiana cell walls all bound to surfaces of in vitro-produced B. bassiana blastospores; however, none of these probes labelled the thin layer of extracellular material covering the plasma membranes of hyphal bodies. These cells were observed freely circulating in S. exigua hemolymph at 36 h postinfection, although immunocompetent hemocytes were known to be present. Additionally, association of hyphal bodies with hemocytes in monolayers was significantly less than for opsonized in vitro blastospores or submerged conidia. The absence of antigenically important galactomannan components on in vivo cells may therefore allow these cells to escape recognition and phagocytosis. Lack of structural components (e.g., chitin, as evidenced by the absence of binding of wheat germ agglutinin) may also be important with respect to evasion of host cellular defense mechanisms. Production of wall material resumed 48 to 60 h postinfection and therefore may coincide with loss of phagocytic capabilities of the hemocytes due to immunosuppressive effects of fungal metabolites. The protoplast-like cells may be formed by the action of hydrolytic enzymes in the hemocytes or by inhibition of fungal cell wall synthetases.
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PMID:Evasion of host defense by in vivo-produced protoplast-like cells of the insect mycopathogen Beauveria bassiana. 837 42


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