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Query: UNIPROT:P17931 (galectin-3)
 2,860 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Ricin B chain (RTB) is an N-glycosylated galactose-specific lectin which folds into two globular domains. Each domain binds one galactoside. The x-ray crystallographic structure has shown that the two binding sites are structurally similar and contain key binding residues which hydrogen bond to the sugar, and a conserved tripeptide, Asp-Val-Arg. We have used oligonucleotide site-directed mutagenesis to change either the binding residues or the homologous tripeptide in one or other or in both of the sites. The 5' signal sequence and RTB coding region were excised from preproricin cDNA and fused in frame to generate preRTB cDNA. Transcripts synthesized in vitro from wild-type or mutant preRTB cloned into the Xenopus transcription vector pSP64T using SP6 RNA polymerase, were microinjected into Xenopus oocytes. The recombinant products were segregated into the oocyte rough endoplasmic reticulum and core-glycosylated, and the N-terminal signal peptide was removed. Mutating sugar binding sites individually did not abrogate the lectin activity of RTB. When both sites were changed simultaneously, RTB was produced which was soluble and stable but no longer able to bind galactose. Changing the Asn residues of the two RTB N-glycosylation sites to Gln showed that oligosaccharide side chains were essential for both the stability and biological activity of recombinant RTB.
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PMID:Mutational analysis of the galactose binding ability of recombinant ricin B chain. 171 62

We investigated the early and late changes of the Golgi region under the influence of the fungal metabolite brefeldin A (BFA) by electron microscopy and lectin cytochemistry using the beta-galactose-specific lectin from the beetle Allomyrina dichotoma (Allo A). In control cells, Allo-A reactions were confined to trans-Golgi elements, the trans-Golgi network, and to endosomes and lysosomes; the nuclear envelope and endoplasmic reticulum were consistently free of Allo A reactions. Our findings with cells from three different lines (i.e., HepG2 hepatoma cells, WI38 fibroblasts, and L132 embryonic lung cells) showed tubular-reticular transformations of the Golgi stacks as early as 30 sec after application of BFA. The transformations started at the cis side and proceeded rapidly; after only a few minutes the Golgi apparatus was no longer apparent as an individual entity. Simultaneously, giant tubules grew out of the Golgi region and traversed the cytoplasm over micrometer-long distances. In part, they were reactive for Allo A. Reactions for beta-galactose occurred in cisternae of the endoplasmic reticulum after 4-5 min of BFA treatment; after 30 min the entire endoplasmic reticulum was intensely reactive for Allo A. At 5 min and later, the tubular-reticular transformations appeared more compact, forming glomerulus-like structures (glomerulini). These were closely associated with cisternae of the endoplasmic reticulum. Initially, glomerulini were mostly Allo A negative or showed peripheral Allo A-positive segments. The number of Allo A-positive glomerulini increased with the duration of treatment. Our findings identify the glomerulini as bipolar structures forming a link between the endoplasmic reticulum and the dissociating Golgi stacks.
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PMID:Early and late transformations occurring at organelles of the Golgi area under the influence of brefeldin A: an ultrastructural and lectin cytochemical study. 851 46

Galectin-3 is a beta-galactoside-binding protein that is secreted from many cells although the protein lacks a signal sequence for transfer into the endoplasmic reticulum and Golgi compartments and entry into classical secretory pathways. Previously it was shown that attachment of the first 120 amino acid residues of the N-terminal sequence of hamster galectin-3 to the cytoplasmic protein chloramphenicol acetyltransferase (CAT) supported the rapid secretion of the fusion protein from transiently transfected Cos cells under conditions in which CAT protein was not secreted. Here we report that progressive N-terminal truncation gradually reduced secretion of the fusion proteins, eventually to very low levels compared with the starting product, but did not totally eliminate secretion until a significant majority of the sequence was removed. Mutant CAT fusion proteins containing internal deletions in residues 97-120 of the galectin-3 N-terminal sequence were also secreted to a similar extent to the starting product, but further deletion of residues 89-96 abolished detectable secretion. Proline to alanine mutagenesis of the sequence YP(90)SAP(93)GAY in two secretion-competent CAT fusion proteins greatly reduced or abolished their secretion, whereas similar mutagenesis of proline pairings present elsewhere in the galectin-3 N-terminal segments of these proteins had no effect. The results indicate that this sequence is one essential determinant for secretion of galectin-3-CAT fusion proteins and by inference galectin-3, at least from transfected Cos cells. However, the short sequence of residues 89-96 by itself is insufficient to direct secretion of CAT fusion proteins and appears to be active only in the context of a larger portion of the galectin-3 N-terminal sequence.
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PMID:Determinants in the N-terminal domains of galectin-3 for secretion by a novel pathway circumventing the endoplasmic reticulum-Golgi complex. 1049 Nov 5

The subcellular plurilocalization of some lectins (galectin-1, galectin-3, galectin-10, calreticulin, etc.) is an intriguing problem, implying different partners according to their localization, and involvement in a variety of cellular activities. For example, the well-known lectin, galectin-3, a lactose-binding protein, can act inside the nucleus in splicing events, and at the plasma membrane in adhesion, and it was demonstrated that galectin-3 interacts in the cytoplasm with Bcl-2, an antiapoptotic protein. Some years ago, our group isolated a nuclear lectin CBP70, capable of recognizing N-acetylglucosamine residues. This lectin, first isolated from the nucleus of HL60 cells, was also localized in the cytoplasm. It has been demonstrated that CBP70 is a glycosylated lectin, with different types of glycosylation, comparing cytoplasmic and nuclear forms. In this article, we have studied the localization of CBP70 in undifferentiated HL60 cells by electron microscopy, immunofluorescence analysis, and subcellular fractionation. The results obtained clearly demonstrated that CBP70 is a plurilocalized lectin that is found in the nucleus, at the endoplasmic reticulum, the Golgi apparatus, and mitochondria, but not at the plasma membrane. Because CBP70, a nuclear glycoprotein, was found to be associated also with the endoplasmic reticulum and the Golgi apparatus where the glycosylation take place, it raised the question: where does the glycosylation of nuclear proteins occur?
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PMID:Glycosylated nuclear lectin CBP70 also associated with endoplasmic reticulum and the Golgi apparatus: does the "classic pathway" of glycosylation also apply to nuclear glycoproteins? 1086 61

CA125 is an ovarian cancer antigen whose recently elucidated primary structure suggests that CA125 is a giant mucin-like glycoprotein present on the cell surface of tumor cells. Here, we establish a functional link between CA125 and beta-galactoside-binding, cell-surface lectins, which are components of the extracellular matrix implicated in the regulation of cell adhesion, apoptosis, cell proliferation and tumor progression. On the basis of mass spectrometry and immunological analyses, we find that CA125 is a counter receptor for galectin-1, as both soluble and membrane-associated fragments of CA125 derived from HeLa cell lysates are shown to bind specifically to human galectin-1 with high efficiency. This interaction is demonstrated (1) to depend on beta-galactose-terminated, O-linked oligosaccharide chains of CA125, (2) to be preferential for galectin-1 versus galectin-3 and (3) to be regulated by the cellular background in which CA125 is expressed. Despite lacking a conventional signal peptide, a CA125 C-terminal fragment of 1148 amino acids, representing less than 10% of the full-length protein, retains the ability to integrate into secretory membranes such as the endoplasmic reticulum (ER) and the Golgi, and is targeted to the plasma membrane by conventional secretory transport. As demonstrated by a novel assay that reconstitutes non-conventional secretion of galectin-1 based on fluorescence-activated cell sorting (FACS), we find that tumor-derived HeLa cells expressing endogenous CA125 present more than ten times as much galectin-1 on their surface compared with non-tumor-derived, CA125-deficient CHO cells. Intriguingly, both the galectin-1 expression level and the cell-surface binding capacity for galectin-1 are shown to be similar in CHO and HeLa cells, suggesting that CA125 might be a factor involved in the regulation of galectin-1 export to the cell surface.
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PMID:The cancer antigen CA125 represents a novel counter receptor for galectin-1. 1261 72

Galectin-3 is a 31 kDa member of a growing family of beta-galactoside-binding animal lectins. This protein is expressed in a variety of tissues and cell types and is mainly found in the cytoplasm, although, depending on cell type and proliferative state, a significant amount of this lectin can also be detected in the nucleus, on the cell surface or in the extracellular environment. Galectin-3 is secreted from cells by a novel and incompletely understood mechanism that is independent of the classical secretory pathway through the endoplasmic reticulum/Golgi network. Galectin-3 exhibits pleiotropic biological function, playing a key role in many physiological and pathological processes.
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PMID:Galectin-3 as a multifunctional protein. 1521 11

Polarized distribution of plasma membrane transporters and receptors in epithelia is essential for vectorial functions of epithelia. This polarity is maintained by sorting of membrane proteins into apical or basolateral transport containers in the trans-Golgi network and/or endosomes followed by their delivery to the appropriate plasma membrane domains. Sorting depends on the recognition of sorting signals in proteins by specific sorting machinery. In the present review, we summarize experimental evidence for and against the hypothesis that N-glycans attached to the membrane proteins can act as apical sorting signals. Furthermore, we discuss the roles of N-glycans in the apical sorting event per se and their contribution to folding and quality control of glycoproteins in the endoplasmic reticulum or retention of glycoproteins in the plasma membrane. Finally, we review existing hypotheses on the mechanism of apical sorting and discuss the potential roles of the lectins, VIP36 and galectin-3, as putative apical sorting receptors.
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PMID:Role of N-glycosylation in trafficking of apical membrane proteins in epithelia. 1897 Dec 12

Cystic Fibrosis is caused by mutations in CFTR, with a deletion of a phenylalanine at position 508 (F508del-CFTR) representing the most common mutation. The F508del-CFTR protein exhibits a trafficking defect and is retained in the endoplasmic reticulum. Here we describe the development of a high-content screen based on a functional assay to identify proteins that correct the F508del-CFTR defect. Using a HEK293 MSR GripTite cell line that stably expresses F508del-CFTR, we individually co-expressed approximately 450 unique proteins fused to the Cl(-)-sensitive YFP(H148Q/I152L) mutant. We then tested correction of F508del-CFTR function by the CI(-)/l(-) exchange method following stimulation with forskolin/IBMX/genistein, using quantitative recordings in multiple individual cells with a high-content (high-throughput) Cellomics KSR imaging system. Using this approach, we identified several known and novel proteins that corrected F508del-CFTR function, including STAT1, Endothelin 1, HspA4, SAPK substrate protein 1, AP2M1, LGALS3/galectin-3, Trk-fused gene, Caveolin 2, PAP/REG3alpha, and others. The ability of these correctors to rescue F508del-CFTR trafficking was then validated by demonstrating their enhancement of maturation (appearance of band C) and by cell surface expression of F508del-CFTR bearing HA tag at the ectodomain using confocal microscopy and flow cytometry. These data demonstrate the utility of high-content analyses for identifying proteins that correct mutant CFTR and discover new proteins that stimulate this correction. This assay can also be utilized for RNAi screens to identify inhibitory proteins that block correction of F508del-CFTR, small molecule, and peptide screens.
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PMID:High-content functional screen to identify proteins that correct F508del-CFTR function. 1908 66

We found a malignant mesenchymal tumor with myofibrogenic differentiation in the liver of a 110-week-old female B6C3F1 mouse used for a carcinogenicity study. Sclerous white patches (maximum size: 20 x 14 mm) were observed mainly in the median lobe of the liver at necropsy. Histologically, the tumor was composed of interlacing fascicles of spindle-shaped cells with oval or elongated nuclei and lightly eosinophilic cytoplasm. Tumor cells metastasized to the lung, parapancreatic lymph node, and spleen. Special staining revealed individual tumor cells surrounded by reticulin fibers and an abundant collagenous matrix. Immunohistochemically, the tumor cells were positive for vimentin, alpha-smooth muscle actin, and desmin, but were negative for von Willebrand factor, Mac-2, S-100, and cytokeratin. Electron microscopic examination revealed that the tumor cells contained prominent rough endoplasmic reticulum and thin filaments in the cytoplasm, although they lacked basal lamina, focal densities, or lipid droplets. Collagenous fibers were observed in the intercellular matrix. Thus, detailed histopathological examination suggested the origin of the present tumor to possibly be Ito cells within the fibrous stroma. This report provides additional histopathological evidence of malignant hepatic nonepithelial tumors in mice.
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PMID:A primary hepatic malignant mesenchymal tumor with myofibrogenic differentiation in a B6C3F1 mouse. 1933 65

Cyclophilin C-associated protein (CyCAP) or Mac-2 binding protein has been identified as a binding protein for cyclophilin C in mice and for Mac-2 (galectin-3) in human, suggesting its multiple binding activity to proteins. In the present study, using specific anti-rat-CyCAP antibody, we found that CyCAP colocalizes with calnexin at the location near the nuclear envelope, however CyCAP does not have colocalization with calreticulin. In senescent fibroblasts and interferon-gamma (IFNgamma) treated fibroblasts, both calnexin and CyCAP form larger polymers and are released from the endoplasmic reticulum (ER) through the cellular membrane to the extracellular area. Immunoprecipitation studies further confirm that the release of calnexin is through binding to CyCAP. Further, we found that tissue transglutaminase (tTG) protein is decreased, however not at the RNA level, in CyCAP null fibroblasts, which suggests that CyCAP is involved in tTG post-translational modification. Our data give novel evidence that CyCAP regulates the post-translational modification of tTG through its colocalization with calnexin in ER.
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PMID:Cyclophilin C-associated protein/Mac-2 binding protein colocalizes with calnexin and regulates the expression of tissue transglutaminase. 2004 54


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