Glycoprotein storage in Gaucher disease: Lectin histochemistry and biochemical studies

Lectin histochemical studies were performed on formalin-fixed, frozen, and paraffin-embedded tissue sections from 19 patients with glucosylceramide lipidosis (i.e., Gaucher disease). Eleven different lectins were used to identify the specific carbohydrate residues in the undegraded stored compounds in the cytoplasm of Gaucher cells. In all cases studied, Gaucher cells stained with Concanavalia ensiformis agglutinin, Datura stramonium agglutinin, Lens culinaris, Ricinus communis agglutinin-I, and wheat germ agglutinin. These results demonstrated common carbohydrate residues in the undegraded material stored within Gaucher cells and indicated the presence of fucosylated N-linked complex oligosaccharides, and glycans containing N-acetyllactosamine repeating sequences, as well as nonreducing terminal β-galactosyl and sialyl residues. In order to confirm these findings using biochemical methods, livers and spleens from Gaucher patients and controls, and from a patient with Niemann-Pick disease type C (included for comparison) were digested with Pronase and the resulting glycopeptides separated by gel filtration into fractions with high and low molecular weight. In the high-molecular-weight fractions from livers of Gaucher patients, the levels of sugars corresponding to N-linked glycans, as measured by gas-liquid chromatography, were elevated over those in controls. In the high-molecular-weight fractions from spleens, the levels of the same sugars were elevated in both Gaucher and Niemann-Pick type C patients. Digestion of the glycopeptides with endo-β-galactosidase, which specifically cleaves polylactosaminoglycans, showed the presence of material containing N-acetyllactosamine repeating units in Gaucher liver glycopeptide fractions, but not in control and Niemann-Pick type C derived glycopeptide fractions. Our histochemical and biochemical studies demonstrated that in addition to glucosylceramide, affected tissues of patients with Gaucher disease accumulate glycoproteins. This accumulation could not have been predicted on the basis of the primary enzymatic defect.