Increased expression of beta-hexosaminidase alpha chain in cultured skin fibroblasts from patients with carbohydrate-deficient glycoprotein syndrome type I.
Carbohydrate-deficient glycoprotein (CDG) syndrome type I is an autosomal recessive multisystem disorder characterized by multiple serum glycoproteins with deficient oligosaccharide chains. This characteristic under-glycosylation is found in several serum glycoproteins. We studied secreted forms of lysosomal enzymes, beta-hexosaminidase and alpha-fucosidase, in serum from the patients and media of cultured fibroblasts. Both beta-hexosaminidase and alpha-fucosidase activities were increased in sera from three CDG patients. The enzyme activity staining using the fluorogenic substrate-4-methylumbelliferyl-alpha-L-fucopyranoside after polyacrylamide gel isoelectric focusing revealed abnormal cathodal bands in sera from CDG patients. On the other hand, no abnormal secreted forms of beta-hexosaminidase and alpha-fucosidase were detected in media from cultured CDG fibroblasts by isoelectric focusing and sodium-dodecyl sulfate-polyacrylamide gel electrophoresis. However, SDS-polyacrylamide gel electrophoresis and Western blotting analysis of beta-hexosaminidase using anti-beta-hexosaminidase A (anti-alpha + beta chains) antibody, showed an increase of a 55-kDa mature form of the alpha chain. Northern blotting analysis identified an increase in mRNA levels of beta-hexosaminidase alpha chain in CDG fibroblasts. Although under-glycosylated fractions of these lysosomal enzymes were not detected in cultured fibroblasts, it was suggested that intracellular processing of these lysosomal enzymes in CDG patients might be altered.
Ichisaka
S
S
Department of Neurobiology, Tottori University Faculty of Medicine, Yonago, Japan.
Ohno
K
K
Yuasa
I
I
Nanba
E
E
Sakuraba
H
H
Suzuki
Y
Y
D015152:Blotting, Northern; D015153:Blotting, Western; D002478:Cells, Cultured; D002648:Child; D002675:Child, Preschool; D018981:Congenital Disorders of Glycosylation / Q000097:blood / Q000201:enzymology*; D004591:Electrophoresis, Polyacrylamide Gel; D005347:Fibroblasts / Q000201:enzymology; D006801:Humans; D007525:Isoelectric Focusing; D012333:RNA, Messenger / Q000378:metabolism; D012867:Skin / Q000201:enzymology* / Q000473:pathology; D005644:alpha-L-Fucosidase / Q000378:metabolism; D001619:beta-N-Acetylhexosaminidases / Q000097:blood / Q000235:genetics / Q000378:metabolism*
D012333:RNA, Messenger; D005644:alpha-L-Fucosidase; D001619:beta-N-Acetylhexosaminidases