Enhanced binding of the neural siglecs, myelin-associated glycoprotein and Schwann cell myelin protein, to Chol-1 (alpha-series) gangliosides and novel sulfated Chol-1 analogs.
Extended glycoconjugate binding specificities of three sialic acid-dependent immunoglobulin-like family member lectins (siglecs), myelin-associated glycoprotein (MAG), Schwann cell myelin protein (SMP), and sialoadhesin, were compared by measuring siglec-mediated cell adhesion to immobilized gangliosides. Synthetic gangliosides bearing the alpha-series determinant (NeuAc alpha2,6-linked to GalNAc on a gangliotetraose core) were tested, including GD1alpha (IV(3)NeuAc, III(6)NeuAc-Gg(4)OseCer), GD1alpha with modified sialic acid residues at the III(6)-position, and the "Chol-1" gangliosides GT1aalpha (IV(3)NeuAc, III(6)NeuAc, II(3)NeuAc-Gg(4)OseCer) and GQ1balpha (IV(3)NeuAc, III(6)NeuAc, II(3)(NeuAc)(2)-Gg(4)OseCer). The alpha-series gangliosides displayed enhanced potency for MAG- and SMP-mediated cell adhesion (GQ1balpha > GT1aalpha, GD1alpha > GT1b, GD1a >> GM1 (nonbinding)), whereas sialoadhesin-mediated adhesion was comparable with alpha-series and non-alpha-series gangliosides. GD1alpha derivatives with modified sialic acids (7-, 8-, or 9-deoxy) or sulfate (instead of sialic acid) at the III(6)-position supported adhesion comparable with that of GD1alpha. Notably, a novel GT1aalpha analog with sulfates at two internal sites of sialylation (NeuAcalpha2,3Galbeta1,4GalNAc-6-sulfatebeta1, 4Gal3-sulfatebeta1,4Glcbeta1,1'ceramide) was the most potent siglec-binding structure tested to date (10-fold more potent than GT1aalpha in supporting MAG and SMP binding). Together with prior studies, these data indicate that MAG and SMP display an extended structural specificity with a requirement for a terminal alpha2, 3-linked NeuAc and great enhancement by nearby precisely spaced anionic charges.
Collins
B E
BE
Department of Pharmacology, The Johns Hopkins School of Medicine, Baltimore, Maryland 21205, USA.
Ito
H
H
Sawada
N
N
Ishida
H
H
Kiso
M
M
Schnaar
R L
RL
D000818:Animals; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D005732:Gangliosides / Q000378:metabolism*; D051379:Mice; D009185:Myelin Proteins / Q000378:metabolism*; D018992:Myelin-Associated Glycoprotein / Q000378:metabolism*; D011485:Protein Binding; D011784:Quail; D051381:Rats; D011956:Receptors, Cell Surface / Q000378:metabolism*; D013431:Sulfates / Q000378:metabolism
D015815:Cell Adhesion Molecules; D005732:Gangliosides; D009185:Myelin Proteins; D018992:Myelin-Associated Glycoprotein; D011956:Receptors, Cell Surface; C104891:SMP protein, Schwann cell, Coturnix coturnix; D013431:Sulfates; C092488:sialic acid receptor