MODIFICATIONS OF CELL-SURFACE SIALIC ACIDS MODULATE CELL-ADHESION MEDIATED BY SIALOADHESIN AND CD22

An increasing number of mammalian cell adhesion molecules, including s ialoadhesion, CD22 and the family of selectins, have been found to bin d cell surface glycoconjugates containing sialic acids. Here we descri be how the structural diversity of this sugar influences cell adhesion mediated by the related molecules sialoadhesin and CD22 in murine mac rophages and B-cells respectively. We show that the 9-0-acetyl group o f Neu5,9Ac(2) and the N-glycoloyl residue of NeuSGc interfere with sia loadhesin binding. In contrast, CD22 binds more strongly to NeuSGc com pared to Neu5Ac. Of two synthetic sialic acids tested, only CD22 bound the N-formyl derivative, whereas a N-trifluoroacetyl residue was acce pted by sialoadhesin. The potential significance for the regulation of sialic acid dependent cell adhesion phenomena is discussed.