title: Absence of α-galactosidase cross-correction in Fabry heterozygote cultured skin fibroblasts.
abstract: Fabry disease (FD) is an X-linked lysosomal storage disorder resulting from deficiency of α-galactosidase A (GLA). Traditionally, heterozygotes were considered asymptomatic carriers of FD, but it is now apparent that the asymptomatic female carrier is the exception and most heterozygotes suffer significant multisystemic disease. To determine why the process of cross-correction does not occur effectively in FD heterozygotes, we investigated GLA production and secretion in cultured skin fibroblasts as well as GLA levels in plasma. The maturation of GLA was similar in FD heterozygotes and control fibroblasts, confirming that both produce the 46kDa mature form; the same as that present in control plasma. However, the proportion of GLA secreted into the culture media was substantially less than eight other lysosomal proteins. Artificial generation of FD heterozygotes in cellulo, along with another lysosomal storage disorder, mucopolysaccharidosis type II, revealed no cross-correction in the FD system, whereas MPS II fibroblasts were able to cross-correct. In plasma, GLA was present as the 46kDa mature form, which lacks the mannose 6-phosphorylated moiety and is not able to be efficiently endocytosed by affected cells. Our evidence shows that fibroblasts secrete minimal amounts of GLA and consequently normal fibroblasts are unable to cross-correct FD fibroblasts. We suggest that symptomatic FD heterozygotes arise due to the secretion of primarily the mature form, with only small amounts of the mannose 6-phosphorylated form of GLA from unaffected cells. This limits capacity for enzyme cross correction of affected cells, despite uptake of exogenous recombinant GLA.
authors.affiliation: Genetics and Molecular Pathology, SA Pathology at Women's and Children's Hospital, North Adelaide, Australia; Department of Paediatrics, University of Adelaide, Australia. Electronic address: maria.fuller@adelaide.edu.au.
authors.forename: Maria
authors.initials: M
authors.lastname: Fuller
authors.affiliation: Baker IDI Heart and Diabetes Institute, Melbourne, Australia.
authors.forename: Natalie
authors.initials: N
authors.lastname: Mellett
authors.affiliation: SAHMRI, Adelaide, Australia.
authors.forename: Leanne K
authors.initials: LK
authors.lastname: Hein
authors.affiliation: University of South Australia, Adelaide, Australia.
authors.forename: Doug A
authors.initials: DA
authors.lastname: Brooks
authors.affiliation: Baker IDI Heart and Diabetes Institute, Melbourne, Australia.
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Meikle
mesh_terms: D002478:Cells, Cultured; D000795:Fabry Disease / Q000201:enzymology* / Q000235:genetics; D005347:Fibroblasts / Q000201:enzymology; D006579:Heterozygote; D006801:Humans; D008360:Mannosephosphates / Q000378:metabolism; D016532:Mucopolysaccharidosis II / Q000201:enzymology; D012867:Skin / Q000166:cytology / Q000201:enzymology; D014281:Trihexosylceramides / Q000378:metabolism; D000519:alpha-Galactosidase / Q000097:blood / Q000378:metabolism*
chemical_list: D008360:Mannosephosphates; D014281:Trihexosylceramides; C027693:mannose-6-phosphate; D000519:alpha-Galactosidase
keywords: Ceramide trihexoside; Cross correction; Fabry disease; Lysosomal enzyme; Lysosomal storage disorder; α-Galactosidase