Structural and immunocytochemical studies on alpha-N-acetylgalactosaminidase deficiency (Schindler/Kanzaki disease).
Alpha-N-acetylgalactosaminidase (alpha-NAGA) deficiency (Schindler/Kanzaki disease) is a clinically and pathologically heterogeneous genetic disease with a wide spectrum including an early onset neuroaxonal dystrophy (Schindler disease) and late onset angiokeratoma corporis diffusum (Kanzaki disease). In alpha-NAGA deficiency, there are discrepancies between the genotype and phenotype, and also between urinary excretion products (sialyl glycoconjugates) and a theoretical accumulated material (Tn-antigen; Gal NAcalpha1-O-Ser/Thr) resulting from a defect in alpha-NAGA. As for the former issue, previously reported genetic, biochemical and pathological data raise the question whether or not E325K mutation found in Schindler disease patients really leads to the severe phenotype of alpha-NAGA deficiency. The latter issue leads to the question of whether alpha-NAGA deficiency is associated with the basic pathogenesis of this disease. To clarify the pathogenesis of this disease, we performed structural and immunocytochemical studies. The structure of human alpha-NAGA deduced on homology modeling is composed of two domains, domain I, including the active site, and domain II. R329W/Q, identified in patients with Kanzaki disease have been deduced to cause drastic changes at the interface between domains I and II. The structural change caused by E325K found in patients with Schindler disease is localized on the N-terminal side of the tenth beta-strand in domain II and is smaller than those caused by R329W/Q. Immunocytochemical analysis revealed that the main lysosomal accumulated material in cultured fibroblasts from patients with Kanzaki disease is Tn-antigen. These data suggest that a prototype of alpha-NAGA deficiency in Kanzaki disease and factors other than the defect of alpha-NAGA may contribute to severe neurological disorders, and Kanzaki disease is thought to be caused by a single enzyme deficiency.
Sakuraba
Hitoshi
H
Department of Clinical Genetics, The Tokyo Metropolitan Institute of Medical Science, Tokyo Metropolitan Organization for Medical Research, 3-18-22 Honkomagome, Bunkyo-ku, Tokyo 113-8613, Japan. sakuraba@rinshoken.or.jp.
Matsuzawa
Fumiko
F
Celestar Lexico-Sciences, MTG D-17, 1-3, Nakase, Mihama-ku, Chiba 261-8501, Japan.
Aikawa
Sei-Ichi
SI
Celestar Lexico-Sciences, MTG D-17, 1-3, Nakase, Mihama-ku, Chiba 261-8501, Japan.
Doi
Hirofumi
H
Celestar Lexico-Sciences, MTG D-17, 1-3, Nakase, Mihama-ku, Chiba 261-8501, Japan.
Kotani
Masaharu
M
Department of Clinical Genetics, The Tokyo Metropolitan Institute of Medical Science, Tokyo Metropolitan Organization for Medical Research, 3-18-22 Honkomagome, Bunkyo-ku, Tokyo 113-8613, Japan.
Nakada
Hiroshi
H
Department of Biotechnology, Faculty of Engineering, Kyoto Sangyo University, Kamigamo-Motoyama, Kita-ku, Kyoto 603-8555, Japan.
Fukushige
Tomoko
T
Department of Dermatology, Faculty of Medicine, Kagoshima University, 8-35-1 Sakuragaoka, Kagoshima 890-8520, Japan.
Kanzaki
Tamotsu
T
Department of Dermatology, Faculty of Medicine, Kagoshima University, 8-35-1 Sakuragaoka, Kagoshima 890-8520, Japan.
D015703:Antigens, CD / Q000378:metabolism; D015295:Antigens, Tumor-Associated, Carbohydrate / Q000378:metabolism; D003461:Crystallography; D000795:Fabry Disease / Q000201:enzymology / Q000235:genetics*; D005347:Fibroblasts / Q000378:metabolism; D006596:Hexosaminidases / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D051907:Lysosomal Membrane Proteins; D008958:Models, Molecular; D019150:Neuroaxonal Dystrophies / Q000235:genetics*; D017434:Protein Structure, Tertiary / Q000235:genetics; D040681:Structural Homology, Protein; D048809:alpha-N-Acetylgalactosaminidase
D015703:Antigens, CD; D015295:Antigens, Tumor-Associated, Carbohydrate; D051907:Lysosomal Membrane Proteins; C040286:Tn antigen; D006596:Hexosaminidases; C482722:NAGA protein, human; D048809:alpha-N-Acetylgalactosaminidase