Role of beta-galactosidase and elastin binding protein in lysosomal and nonlysosomal complexes of patients with GM1-gangliosidosis.
G(M1)-gangliosidosis is a lysosomal storage disorder caused by a deficiency of beta-galactosidase (GLB1). The GLB1 gene gives rise to the GLB1 lysosomal enzyme and to the elastin binding protein (EBP), involved in elastic fiber deposition. GLB1 forms a complex with protective protein cathepsin A (PPCA), alpha neuraminidase (NEU1), and galactosamine 6-sulphate sulfatase (GALNS) inside lysosomes, while EBP binds to PPCA and NEU1 on the cell surface. We investigated the function of the GLB1 and EBP mutated proteins by analyzing the clinical, genetic, and cellular data of 11 G(M1)-gangliosidosis patients. Their molecular analysis, followed by expression studies, lead to the identification of four new and 10 known GLB1 mutations. Some common amino acid substitutions [c.1445G>A (p.Arg482H), c.622C>T (p.Arg208His), c.175C>T (p.Arg59Cys) and c.176G>A (p.Arg59His)] were present in the GLB1 enzyme of several patients, all of Mediterranean origin, suggesting a common origin. Western blotting analyses against GLB1, EBP, and PPCA proteins showed that the identified mutations affect GLB1 enzyme activity and/or stability. The c.1445G>A (p.Arg482His), c.175C>T (p.Arg59Cys), c.733+2T>C, c.1736G>A (p.Gly579Asp), and c.1051C>T (p.Arg351X) GLB1 mutations, affect the stabilization of PPCA probably because they hamper the interaction between GLB1/EBP and PPCA within the multiprotein complex. The amount of EBP was normal, but the detection of impaired elastogenesis in such patients suggests an alteration in its function. We conclude that the presence of genetic lesions in both GLB1 and EBP coding region does not directly predict impaired elastogenesis and that elastic fiber assembly has to be evaluated specifically in each case. Nevertheless, the degree of EBP involvement may be linked to specific clinical findings.
Caciotti
Anna
A
Department of Pediatrics, University of Florence, Meyer Hospital, Florence, Italy.
Donati
Maria Alice
MA
Boneh
Avihu
A
d'Azzo
Alessandra
A
Federico
Antonio
A
Parini
Rossella
R
Antuzzi
Danielas
D
Bardelli
Tiziana
T
Nosi
Daniele
D
Kimonis
Virginia
V
Zammarchi
Enrico
E
Morrone
Amelia
A
D000328:Adult; D017398:Alternative Splicing; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D019556:COS Cells; D043402:Cathepsin A / Q000737:chemistry; D002478:Cells, Cultured / Q000378:metabolism; D002522:Chlorocebus aethiops; D004547:Elastic Tissue / Q000648:ultrastructure; D005260:Female; D005347:Fibroblasts / Q000378:metabolism; D016537:Gangliosidosis, GM1 / Q000145:classification / Q000235:genetics* / Q000473:pathology; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008247:Lysosomes / Q000201:enzymology; D008297:Male; D008969:Molecular Sequence Data; D046912:Multiprotein Complexes; D020125:Mutation, Missense; D010641:Phenotype; D011485:Protein Binding; D017510:Protein Folding; D025941:Protein Interaction Mapping; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D014162:Transfection; D001616:beta-Galactosidase / Q000737:chemistry / Q000235:genetics / Q000502:physiology*
D046912:Multiprotein Complexes; D011956:Receptors, Cell Surface; C054901:elastin-binding proteins; C061901:GLB1 protein, human; D001616:beta-Galactosidase; D043402:Cathepsin A