Isolation and Characterisation of the Integral Glycosaminoglycan Constituents of Human AA and AL Amyloid Fibrils

Abstract

Amyloid fibrils were isolated by extraction in water from the livers and spleens of 4 patients who had died of monoclonal, AL-type, systemic amyloidosis and 1 with reactive systemic, AA-type amyloidosis. Each fibril preparation contained 1-2% by weight of glycosaminoglycan (GAG) which was tightly associated with the fibrils and not just co-isolated from the tissues with them. After exhaustive digestion of the fibrils with papain and pronase the GAGs were specifically precipitated with cetylpyridinium chloride and were identified by cellulose acetate electrophoresis and selective susceptibility to specific glycosidases. All the preparations contained approximately equal amounts of heparan sulphate and dermatan sulphate together with traces of heparin-like material. There was no evidence for the presence of chondroitin sulphate or other GAGs. Fine structural analysis by oligosaccharide mapping in gradient Polyacrylamide gels, following partial digestion with specific glycosidases, showed very similar structures among the heparan sulphates and the dermatan sulphates respectively. GAGs were also extracted by solubilising amyloid fibrils in 4 M guanidinium chloride followed by CsCI density gradient ultracentrifugation. Although a minor proportion of the GAG material obtained in this way was apparently in the form of proteoglycan molecules, most of it was free GAG chains. The presence in amyloid fibrils of different types, in different organs and from different patients of particular GAG classes with similar structures, supports the view that these molecules may be of pathogenetic significance.