Galectin

About: Galectin is a research topic. Over the lifetime, 2076 publications have been published within this topic receiving 103409 citations. The topic is also known as: IPR001079 & Galectin.

Glycan characterization of pregnancy-specific glycoprotein 1 and its identification as a novel Galectin-1 ligand.

Abstract: Pregnancy-specific beta 1 glycoprotein (PSG1) is secreted from trophoblast cells of the human placenta in increasing concentrations as pregnancy progresses, becoming one of the most abundant proteins in maternal serum in the third trimester. PSG1 has seven potential N-linked glycosylation sites across its four domains. We carried out glycomic and glycoproteomic studies to characterize the glycan composition of PSG1 purified from serum of pregnant women and identified the presence of complex N-glycans containing poly LacNAc epitopes with α2,3 sialyation at four sites. Using different techniques, we explored whether PSG1 can bind to galectin-1 (Gal-1) as these two proteins were previously shown to participate in processes required for a successful pregnancy. We confirmed that PSG1 binds to Gal-1 in a carbohydrate-dependent manner with an affinity of the interaction of 0.13 μM. In addition, we determined that out of the three N-glycosylation-carrying domains, only the N and A2 domains of recombinant PSG1 interact with Gal-1. Lastly, we observed that the interaction between PSG1 and Gal-1 protects this lectin from oxidative inactivation and that PSG1 competes the ability of Gal-1 to bind to some but not all of its glycoprotein ligands.

Glycosylation and Disease

Abstract: Glycosylation is the process of attachment of sugar molecules, usually in chains (oligosaccharides), to proteins and lipids to form the glycoproteins and glycolipids found in eukaryotic and some prokaryotic organisms. The presence of oligosaccharides on a protein can have substantial effects on its size, stability, charge and antigenicity. The varying structure, branching and substitution of the carbohydrates in an oligosaccharide results in much greater diversity than would be achieved for a peptide with an equivalent number of residues. Acquired alterations in glycosylation occur in cancer and inflammation and may have particularly important functional consequences when they affect mucosae. They also have the potential to affect pathogen–host and other cell–cell interactions. Congenital glycosylation disorders most commonly affect N-glycosylation and affect development in diverse ways. There is increasing evidence of the importance of interactions between carbohydrate structures and carbohydrate-binding proteins (lectins) which may be extrinsic (dietary or microbial) or intrinsic (mammalian galectins or siglecs). Key Concepts: Glycosylation occurs as N- and O-linked (mucin type) oligosaccharides (glycans) on glycoproteins and as glycolipids. Variation in sequence, linkage and substitution of carbohdrates in a glycan means that a relatively short glycan can have many more variations (glycoforms) than a peptide with an equivalent number of amino acids. Variations in glycan structure can result from a range of different mechanisms that include altered glycosyltransferase and glycosidase activity, Golgi acidification and structure, donor and acceptor availability. Cell–cell and cell–microbe interactions are often driven by interactions between lectins on one cell and the relevant carbohydrate (glycan) receptor on the other cell. Mucins are heavily glycosylated, particularly with O-linked glycans and this gives them their protective properties. Mammalian lectins include a family of galactose-binding lectins called galectins that interact with some of the glycans that show increased expression in epithelial cancers with increased cancer cell to endothelial adherence and increased metastasis as a consequence. Foodstuffs, particularly legumes, contain lectins some of which resist digestion and may have biologically significant interactions with the intestinal epithelium. A wide range of rare congenital dosorders of glycosylation have been recognised – these have many and varied developmental consequences. Some of the developmental glycosylation disorders can be screened for by isoelectric focusing of serum glycoproteins. Keywords: glycobiology; glycoproteins; glycolipids; mucins; blood groups; glycocalyx; cell–cell interaction; epithelial–microbe interaction

Signaling mechanisms in protozoa and invertebrates

Abstract: Evolutionary Significance of the Hormone Recognition Capacity in Unicellular Organisms. Development of Hormone Receptors.- 1 Introduction.- 2 Receptor Memory: Hormonal Imprinting.- 3 Problems of the Specificity of Imprinting.- 4 Time, Concentration, and Downregulation.- 5 Sugars of the Receptors.- 6 Cell Aging and Imprinting.- 7 Imprinting by Amino Acids and Oligopeptides.- 8 Receptors of the Nuclear Envelope.- 9 Possible Mechanisms of Imprinting.- 10 The Other Component: Hormones in Protozoa.- 11 Evolutionary Conclusions Based on the Unicellular Model.- References.- Studies on the Opioid Mechanism in Tetrahymena.- 1 Introduction to Opioid Mechanisms.- 1.1 Opioid Mechanisms in Invertebrate Metazoa.- 1.2 Opioid Mechanisms in Unicellular Organisms.- 2 The Opioid Mechanism in Tetrahymena.- 2.1 Pharmacological Characterization of the Endogenous Opioid.- 2.2 Pharmacological Characterization of the Opioid Receptor.- 2.3 Biochemical Characterization of the Signal Transduction Pathway.- 3 Conclusions.- References.- Adenylate and Guanylate Cyclases in Tetrahymena.- 1 Introduction.- 2 Cyclic Nucleotide Metabolism in Tetrahymena.- 2.1 Cell Growth- and Cycle-Associated Changes.- 2.2 Involvement in Biological Regulation.- 3 Cyclases Involved in Cell Metabolism and Functions.- 4 Regulatory Mechanisms of Cyclases.- 4.1 Adenylate Cyclase.- 4.2 Guanylate Cyclase.- 5 Structure and Intracellular Distribution of Calmodulin.- 6 Conclusion.- References.- Signal Peptide-Induced Sensory Behavior in Free Ciliates: Bioassays and Cellular Mechanisms.- 1 Introduction.- 2 Peptide Signals in Ciliates.- 2.1 Signal Peptides Found Intracellularly.- 2.2 Signal Peptides Having Sensory Effects.- 2.2.1 Physiological Effects of Insulin on Tetrahymena.- 3 Bioassays Measuring Peptide-Induced Changes of Cell Behavior and Ciliary Activity.- 3.1 Population Assays for Chemoattraction.- 3.2 Single Cell Assays for Chemoattraction.- 3.3 Assays of Ciliary Activity.- 4 Cellular Mechanisms Related to Peptide Action on Individual Cell Behavior.- 4.1 Adaptation.- 4.2 Persistence.- 5 Concluding Remarks.- References.- Ciliate Pheromones.- 1 Introduction.- 2 Background.- 3 Pheromone Notation and Origin.- 4 Pheromone Secretion and Purification.- 5 Pheromone Structure.- 6 Pheromone Genes.- 7 Pheromone Receptors.- 8 Competitive Pheromone Receptor-Binding Reactions.- 9 Pheromones as Growth Factors.- 10 Concluding Remarks.- References.- Cell-Surface GPI Expression in Protozoa. The Connection with the PI System.- 1 Introduction.- 1.1 The GPI Anchor.- 1.2 The GPI Anchor Biosynthesis.- 1.3 Enzymes with Specificities for GPI Anchors.- 1.4 The Inositol Phospholipids and Signal Transduction.- 2 The Cell-Surface Expression of GPI-Anchored Proteins in the Protozoa.- 2.1 GPI-Anchored Proteins in the Parasitic Protozoa.- 2.2 GPI-Anchored Proteins in the Free-Living Protozoa.- 3 Inositol Phospholipids in Tetrahymena pyriformis. The Possible Link Between the PI System and Synthesis of GPI.- References.- Cell Adhesion Proteins in the Nonvertebrate Eukaryotes.- 1 Introduction.- 1.1 History and Philosophy.- 1.2 Evolution.- 2 Approaches and Findings.- 3 Protista.- 3.1 Trypanosoma cruzi.- 3.2 Cellular Slime Molds.- 4 Higher Eukaryotes.- 5 An Alveolate: Plasmodium.- 6 Plants.- 6.1 Chlamydomonas.- 6.2 Volvox.- 6.3 Higher Plants.- 7 Fungi.- 7.1 Saccharomyces cerevisiae.- 7.2 Candida.- 8 Metazoa.- 8.1 Sponges.- 8.2 Cnidaria: Hydra.- 8.3 Tripoblasts.- 8.3.1 Pseudocoelatomates: Caenorhabditis elegans.- 8.4 Insects.- 8.5 Deuterostomes.- 8.5.1 Fertilization in Sea Urchins.- 9 Conclusions.- 10 Characteristics of Cell Adhesion Proteins.- 10.1 Modules.- 10.2 Cell Surface Association.- 10.3 Role of Ca2+.- 10.4 Binding Characteristics.- 11 Extracellular Matrix Interactions.- 12 Role of Lectins and Carbohydrates.- 13 Signal Transduction and Cytoplasmic Domains.- References.- Animal Lectins as Cell Surface Receptors: Current Status for Invertebrate Species.- 1 Introduction.- 2 Animal Lectins as Cell Membrane Receptors.- 3 Lectin Families in Invertebrate and Protochordate Species. Their Association with the Hemocyte Plasma Membrane.- 4 Summary and Prospects.- References.- Characterization of the Receptor Protein-Tyrosine Kinase Gene from the Marine Sponge Geodia cydonium.- 1 Introduction.- 2 Protein Kinases.- 3 Receptor Protein-Tyrosine Kinases.- 4 Receptor Protein-Tyrosine Kinase from the Sponge Geodia cydonium.- 4.1 Ligand-Binding Domain (Immunoglobulin-Like Domain).- 4.2 Intron/Exon.- 4.3 Transmembrane Domain.- 4.4 Juxtamembrane Region.- 4.5 Catalytic Domain.- 4.6 3?-Nontranslated Region.- 5 Proposed Function of the Sponge Receptor Protein-Tyrosine Kinase.- 6 Implication for Molecular Evolution of Metazoa.- 7 Summary and Perspectives.- References.

Blockage of Galectin-receptor Interactions by α-lactose Exacerbates Plasmodium berghei-induced Pulmonary Immunopathology.

Abstract: Malaria-associated acute lung injury (ALI) is a frequent complication of severe malaria that is often caused by "excessive" immune responses. To better understand the mechanism of ALI in malaria infection, here we investigated the roles of galectin (Gal)-1, 3, 8, 9 and the receptors of Gal-9 (Tim-3, CD44, CD137, and PDI) in malaria-induced ALI. We injected alpha (α)-lactose into mice-infected with Plasmodium berghei ANKA (PbANKA) to block galectins and found significantly elevated total proteins in bronchoalveolar lavage fluid, higher parasitemia and tissue parasite burden, and increased numbers of CD68(+) alveolar macrophages as well as apoptotic cells in the lungs after blockage. Additionally, mRNA levels of Gal-9, Tim-3, CD44, CD137, and PDI were significantly increased in the lungs at day 5 after infection, and the levels of CD137, IFN-α, IFN-β, IFN-γ, IL-4, and IL-10 in the lungs were also increased after α-lactose treatment. Similarly, the levels of Gal-9, Tim-3, IFN-α, IFN-β, IFN-γ, and IL-10 were all significantly increased in murine peritoneal macrophages co-cultured with PbANKA-infected red blood cells in vitro; but only IFN-α and IFN-β were significantly increased after α-lactose treatment. Our data indicate that Gal-9 interaction with its multiple receptors play an important role in murine malaria-associated ALI.