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The network of adhesion/growth-regulatory galectins in chicken (chicken galectin, CG) has only one tandemrepeat-type protein, CG8. Using a cell-based assay and probing galectin reactivity with a panel of fluorescent neoglycoconjugates (glycoprobes), its glycan-binding profile was determined. For internal validation, human galectin-8 (HG8) was tested. In comparison to HG8, CG8 showed a rather similar specificity: both galectins displayed high affinity to blood group ABH antigens as well as to 3′-sialylated and 3′-sulfated lactosamine chains. The most remarkable difference was found to be an ability of HG8 (but not CG8) to bind the disaccharide Galβ1-3GlcNAc (Le) as well as branched and linear oligolactosamines. The glycan-binding profile was shown to be influenced by glycocalix of the cell, where the galectin is anchored. Particularly, glycosidase treatment of galectin-loaded cells led to the change of the profile. Thus, we suppose the involvement of cis-glycans in the interaction of cell-anchored galectins with external glycoconjugates. [ABSTRACT FROM AUTHOR]

Soluble siglecs-1,-4,-5,-6,-7,-8,-9, and-10 were probed with polyacrylamide glycoconjugates in which: 1) the Neu5Ac residue was substituted by a sulfate group (Su); 2) glycoconjugates contained both Su and Neu5Ac; 3) sialoglycoconjugates contained a tyrosine-O-sulfate residue. It was shown that sulfate derivatives of LacNAc did not bind siglecs-1,-4,-5,-6,-7,-8,-9, and-10; binding of 6′-O-Su-LacNAc to siglec-8 was stronger than binding of 3′SiaLacNAc. The relative affinity of 3′-O-Su-TF binding to siglecs-1,-4, and-8 was similar to that of 3′SiaTF. 3′-O-Su-Lec displayed two-fold weaker binding to siglec-1 and siglec-4 than 3′SiaLec. The interaction of soluble siglecs with sulfated oligosaccharides containing sialic acid was also studied. It was shown that siglecs-1,-4,-5,-6,-7,-9, and-10 did not interact with these compounds; binding of 6-O-Su-3′SiaLacNAc and 6-O-Su-3′SiaTF to siglec-8 was weaker than that of the corresponding sulfate-free sialoside probes. Siglec-8 displayed affinity to 6′-O-Su-LacNAc and 6′-O-Su-SiaLex, and defucosylation of the latter compound led to an increase in the binding. Sialoside probes containing tyrosine-O-sulfate residue did not display increased affinity to siglecs-1 and-5 compared with glycoconjugates containing only sialoside. Cell-bound siglecs-1,-5,-7, and-9 did not interact with 6-O-Su-3′SiaLacNAc, whereas the sulfate-free probe 3′SiaLacNAc demonstrated binding. In contrast, the presence of sulfate in 6-O-Su-6′SiaLacNAc did not affect binding of the sialoside probe to siglecs. 6′-O-Su-SiaLex displayed affinity to cell-bound siglecs-1 and-5; its isomer 6-O-Su-SiaLex bound more strongly to siglecs-1,-5, and-9 than SiaLex. [ABSTRACT FROM AUTHOR]