INCREASED EXPRESSION OF BETA-HEXOSAMINIDASE ALPHA-CHAIN IN CULTURED SKIN FIBROBLASTS FROM PATIENTS WITH CARBOHYDRATE-DEFICIENT GLYCOPROTEINSYNDROME TYPE-I

Carbohydrate-deficient glycoprotein (CDG) syndrome type I is an autoso mal recessive multisystem disorder characterized by multiple serum gly coproteins with deficient oligosaccharide chains. This characteristic under-glycosylation is found in several serum glycoproteins. We studie d secreted forms of lysosomal enzymes, beta-hexosaminidase and alpha-f ucosidase, in serum from the patients and media of cultured fibroblast s. Both beta-hexosaminidase and alpha-fucosidase activities were incre ased in sera from three CDG patients. The enzyme activity staining usi ng the fluorogenic strate-4-methylumbelliferyl-alpha-L-fucopyranoside after polyacrylamide gel isoelectric focusing revealed abnormal cathod al bands in sera from CDG patients. On the other hand, no abnormal sec reted forms of beta-hexosaminidase and alpha-fucosidase were detected in media from cultured CDG fibroblasts by isoelectric focusing and sod ium-dodecyl sulfate-polyacrylamide gel electrophoresis. However, SDS-p olyacrylamide gel electrophoresis and Western blotting analysis of bet a-hexosaminidase using anti-beta-hexosaminidase A (anti-alpha + beta c hains) antibody, showed an increase of a 55-kDa mature form of the alp ha chain. Northern blotting analysis identified an increase in mRNA le vels of beta-hexosaminidase alpha chain in CDG fibroblasts. Although u nder-glycosylated fractions of these lysosomal enzymes were not detect ed in cultured fibroblasts, it was suggested that intracellular proces sing of these lysosomal enzymes in CDG patients might be altered. (C) 1998 Elsevier Science B.V. All rights reserved.