Intracellular sorting of galectin-8 based on carbohydrate fine specificity.

Galectin-8 has two carbohydrate recognition domains (CRDs), both of which bind beta-galactosides, but have different fine specificity for larger saccharides. Previously we found that both CRDs were needed for efficient cell surface binding and signaling by soluble galectin-8, but unexpectedly binding of the N-CRD to its best ligands, alpha2-3-sialylated galactosides, was not needed. In search for another role for this fine specificity, we now compared endocytosis of galectin-8 in Chinese hamster ovary (CHO) cells and in a mutant (Lec2) lacking sialylated glycans, by fluorescence microscopy.

Affinity of galectin-8 and its carbohydrate recognition domains for ligands in solution and at the cell surface.

Galectin-8 has two different carbohydrate recognition domains (CRDs), the N-terminal Gal-8N and the C-terminal Gal-8C linked by a peptide, and has various effects on cell adhesion and signaling. To understand the mechanism for these effects further, we compared the binding activities of galectin-8 in solution with its binding and activation of cells. We used glycan array analysis to broaden the specificity profile of the two galectin-8 CRDs, as well as intact galectin-8s (short and long linker), confirming the unique preference for sulfated and sialylated glycans of Gal-8N.

Synthesis of a 3'-naphthamido-LacNAc fluorescein conjugate with high selectivity and affinity for galectin-3.

Described is the synthesis of a fluorescent LacNAc derivative appended with a 3'-deoxy-3'-naphthamido functionality, 2-(fluorescein-5/6-amido)ethyl 3-deoxy-3-(2-naphthamido)-beta-D-galactopyranosyl-(1-->4)-2-acetamido-2-deoxy-beta-D-glucopyranoside, which confers high affinity (Kd 170 nM) and selectivity for galectin-3 via a stacking interaction with Arg144. Its use as a selective and sensitive galectin-3 probe is demonstrated with fluorescence polarization measurements.

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

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.

Synthesis of a phenyl thio-beta-D-galactopyranoside library from 1,5-difluoro-2,4-dinitrobenzene: discovery of efficient and selective monosaccharide inhibitors of galectin-7.

The galectins are a family of [small beta]-galactoside-binding proteins that have been implicated in cancer and inflammation processes. Herein, we report the synthesis of a library of 28 compounds that was tested for binding to galectins-1, -3, -7, -8N and -9N. An aromatic nucleophilic substitution reaction between 1,5-difluoro-2,4-dinitrobenzene and a galacto thiol gave 5-fluoro-2,4-dinitrophenyl 2,3,4,6-tetra-O-acetyl-1-thio-beta-D-galactopyranoside.

Introduction to galectins.

Good evidence suggest roles of galectins in cancer, immunity and inflammation, and development, but a unifying picture of their biological function is lacking. Instead galectins appear to have a particularly diverse, bewildering but intriguing array of activities both inside and outside cells--"clear truths and mysteries are inextricably twined". Fortunately this has not discouraged but rather enthused a large number of good galectin researchers, some of which have contributed to this special issue of Glycoconjugate Journal to provide a personal, critical status of the field.

Efficient and expedient two-step pyranose-retaining fluorescein conjugation of complex reducing oligosaccharides: galectin oligosaccharide specificity studies in a fluorescence polarization assay.

Fluorescence labeling of naturally occurring saccharides provides a tool for studying lectins. A practical and efficient two-step protocol for fluorescence labeling of reducing sugars without disrupting their pyranose structure has been developed, consisting of generation of the amino sugar using NH(4)HCO(3)(s)/NH(3)(aq, concentrated) followed by BOP-mediated acylation with derivatives of 5- or 6-carboxyfluorescein. The acylated conjugates were subsequently run against galectins-1, -3, and -8, beta-galactoside recognizing lectins of current interest, in a fluorescence polarization binding assay.