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.

Glycosylation in immune cell trafficking.

Abstract: Leukocyte recruitment encompasses cell adhesion and activation steps that enable circulating leukocytes to roll, arrest, and firmly adhere on the endothelial surface before they extravasate into distinct tissue locations. This complex sequence of events relies on adhesive interactions between surface structures on leukocytes and endothelial cells and also on signals generated during the cell-cell contacts. Cell surface glycans play a crucial role in leukocyte recruitment. Several glycosyltransferases such as alpha1,3 fucosyltransferases, alpha2,3 sialyltransferases, core 2 N-acetylglucosaminlytransferases, beta1,4 galactosyltransferases, and polypeptide N-acetylgalactosaminyltransferases have been implicated in the generation of functional selectin ligands that mediate leukocyte rolling via binding to selectins. Recent evidence also suggests a role of alpha2,3 sialylated carbohydrate determinants in triggering chemokine-mediated leukocyte arrest and influencing beta1 integrin function. The recent discovery of galectin- and siglec-dependent processes further emphasizes the significant role of glycans for the successful recruitment of leukocytes into tissues. Advancing the knowledge on glycan function into appropriate pathology models is likely to suggest interesting new therapeutic strategies in the treatment of immune- and inflammation-mediated diseases.

Sweet 'n' sour: the impact of differential glycosylation on T cell responses

Abstract: The fate and functional activity of T lymphocytes depend largely on the precise timing of gene expression and protein production. However, it is clear that post-translational modification of proteins affects their functional properties. Although modifications such as phosphorylation have been intensely studied by immunologists, less attention has been paid to the impact that changes in glycosylation have on protein function. However, there is considerable evidence that glycosylation plays a key role in immune regulation. We will focus here on examples in which differential glycosylation affects the development, survival or reactivity of T cells.

A human lectin, galectin-3 (epsilon bp/Mac-2), stimulates superoxide production by neutrophils.

Abstract: A family of soluble animal lectins, galectins, with beta-galactoside-binding activity, is gaining increased attention. One member of this family, galectin-3, has been previously designated by this group as epsilon bp, for its IgE-binding activity. On the basis of the saccharide specificity and other biochemical characteristics of epsilon bp, it is possible that this lectin could have an important extracellular modulatory role, functioning through recognition of critical cell surface glycoproteins on many cell types. We present evidence here that recombinant human epsilon bp activates human neutrophils in a dose-dependent manner as demonstrated by superoxide production. The observed activity is dependent on the lectin property of epsilon bp intrinsic to its carboxyl-terminal domain, as it could be inhibited effectively by lactose, a known saccharide ligand of epsilon bp. However, the amino-terminal domain is also necessary for the observed activity, as epsilon bp-C (the carboxyl-terminal domain fragment) is devoid of neutrophil-activating activity, even though it retains the carbohydrate-binding property. Affinity purification of lysates from cell surface-radio-iodinated neutrophils revealed two major protein bands of M(r) 115,000 and M(r) 180,000 that are recognized by epsilon bp and preliminary data suggested that one of these proteins is NCA-160, a human carcinoembryonic Ag-related glycoprotein. This study thus lends further support to our view of an extracellular function for epsilon bp and suggests that this protein has an important role in inflammation and host defense through modulating the function of neutrophils.

Plasma membrane domain organization regulates EGFR signaling in tumor cells

Abstract: Macromolecular complexes exhibit reduced diffusion in biological membranes; however, the physiological consequences of this characteristic of plasma membrane domain organization remain elusive. We report that competition between the galectin lattice and oligomerized caveolin-1 microdomains for epidermal growth factor (EGF) receptor (EGFR) recruitment regulates EGFR signaling in tumor cells. In mammary tumor cells deficient for Golgi β1,6N-acetylglucosaminyltransferase V (Mgat5), a reduction in EGFR binding to the galectin lattice allows an increased association with stable caveolin-1 cell surface microdomains that suppresses EGFR signaling. Depletion of caveolin-1 enhances EGFR diffusion, responsiveness to EGF, and relieves Mgat5 deficiency–imposed restrictions on tumor cell growth. In Mgat5+/+ tumor cells, EGFR association with the galectin lattice reduces first-order EGFR diffusion rates and promotes receptor interaction with the actin cytoskeleton. Importantly, EGFR association with the lattice opposes sequestration by caveolin-1, overriding its negative regulation of EGFR diffusion and signaling. Therefore, caveolin-1 is a conditional tumor suppressor whose loss is advantageous when β1,6GlcNAc-branched N-glycans are below a threshold for optimal galectin lattice formation.