Affinity binding of glycosaminoglycans with β2-microglobulin

Background. A constant finding in beta(2)-microglobulin (beta2m) amyloidosis is an increase in tissue heparan sulfate (HS) and chondroitin sulfate (CS) proteoglycans (PGs) at sites of amyloid deposits. However, the binding characteristics of PGs with beta2m have not been elucidated yet. Methods: Using affinity retardation chromatography, beta2m- and glycosaminoglycan (GAG)-anchored columns, an affinity between beta2m and GAGs was analyzed. Five peptides which spanned the entire beta2m amino acid sequence were prepared, and an affinity between these peptides and heparin (HP) was examined. Furthermore, the specific binding of biotinylated beta2m peptide for AA amyloid deposits via GAGs was examined on tissue sections. Results: Using beta2m-anchored column, HP showed the smallest dissociation constant (K-d), i.e. the strongest affinity, among the GAGs examined. At 0.4 M NaCl, the K(d)s of beta2m relative to BSA-anchored columns for HP, HS, CS-A, CS-B, and CS-C were 94,620,130,660 and 190 muM, respectively. Using GAG-anchored columns, at 0.15 M NaCl, pH 7.4, beta2m also showed an affinity for HP, with the Kd relative to a reference column being 370 muM. Under the latter conditions, no beta2m affinity for CSA was demonstrated. Among the five peptides, peptide-1, which is composed of residues 1-24, showed the highest affinity for HP, the K-d being 190 muM. Peptides analogous to peptide-1, in which each basic amino acid was individually replaced by alanine, showed a remarkable decrease in affinity for HP. The specific binding of biotinylated beta2m peptide for AA amyloid deposits via HS and CS was confirmed in situ by pretreatment with heparitinase and chondroitinase ABC. Conclusion: The present data indicate that HP/HS is effective in the binding of the beta2m monomer, and the anatomic localization of P2m amyloid precursor protein. Copyright (C) 2002 S. KargerAG, Basel.