Probing Sialic Acid Binding Ig-Like Lectins (Siglecs) with Sulfated Oligosaccharides

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E. M. Rapoport¹, G. V. Pazynina¹, M. A. Sablina¹, P. R. Crocker², and N. V. Bovin^1*

¹Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, ul. Miklukho-Maklaya 16/10, 117997 Moscow, Russia; fax: (7-495) 330-5592; E-mail: bovin@carbohydrate.ru

²The Wellcome Trust Biocentre, School of Life Sciences, University of Dundee DD1 5EH, Scotland, UK; E-mail: p.r.crocker@dundee.ac.uk

^* To whom correspondence should be addressed.

Received December 1, 2005; Revision received February 3, 2006

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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-Le^c displayed two-fold weaker binding to siglec-1 and siglec-4 than 3'SiaLe^c. 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-SiaLe^x, 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-SiaLe^x displayed affinity to cell-bound siglecs-1 and -5; its isomer 6-O-Su-SiaLe^x bound more strongly to siglecs-1, -5, and -9 than SiaLe^x.

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KEY WORDS: sialic acid, siglecs, sulfated oligosaccharides, carbohydrate specificity

DOI: 10.1134/S0006297906050051

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