Human beta-galactosidase and alpha-neuraminidase deficient mucolipidosis: genetic complementation analysis of the neuraminidase deficiency

Mechanism-based Fluorescent Labeling of β-Galactosidases

(4-N-5-Dimethylaminonaphthalene-1-sulfonyl-2-difluoromethylphenyl)-beta-d-galactopyranoside was synthesized and successfully tested on beta-galactosidases from Xanthomonas manihotis (Wong-Madden, S. T., and Landry, D. Glycobiology (1995) 5, 19-28 and Taron, C. H., Benner, J. S., Hornstra, L. J., and Guthrie, E. P. (1995) Glycobiology 5, 603-610), Escherichia coli (Jacobson, R. H., Zhang, X. J., DuBose, R. F., and Matthews, B. W. (1994) Nature 369, 761-766), and Bacillus circulans (Fujimoto, H., Miyasato, M., Ito, Y., Sasaki, T., and Ajisaka, K. (1988) Glycoconj. J. 15, 155-160) for the rapid identification of the catalytic site. Reaction of the irreversible inhibitor with enzymes proceeded to afford a fluorescence-labeled protein suitable for further high throughput characterization by using antidansyl antibody and matrix-assisted laser desorption ionization time-of-flight/time-of-flight (MALDI-TOF/TOF). Specific probing by a fluorescent aglycon greatly facilitated identification of the labeled peptide fragments from beta-galactosidases. It was demonstrated by using X. manihotis beta-galactosidase that the Arg-58 residue, which is located within a sequence of 56IPRAYWKD63, was labeled by nucleophilic attack of the guanidinyl group. This sequence including Arg-58 (Leu-46 to Tyr-194) was similar to that (Met-1 to Tyr-151) of Thermus thermophilus A4, which is the first known structure of glycoside hydrolases family 42 (Hidaka, M., Fushinobu, S., Ohtsu, N., Motoshima, H., Matsuzawa, H., Shoun, H., and Wakagi, T. (2002) J. Mol. Biol. 322, 79-91). A catalytic glutamic acid (Glu-537) of E. coli beta-galactosidase was proved to be labeled by the same procedure, suggesting that the modification site with this irreversible substrate might depend both on the nucleophilicity of the amino acids and their spatial arrangement in the individual catalytic cavity. Similarly, a Glu-259 in 257TLEE260 was selectively labeled using B. circulans beta-galactosidase, indicating that Glu-259 is one of the nucleophiles in the active site. The present method can be readily extended to other glycosidases and should greatly aid the high throughput proteomics of many glycoside hydrolases showing both retaining- and inverting-type mechanisms.

Juvenile galactosialidosis in a white male: a new variant

We describe a 19-year-old white male with juvenile galactosialidosis. He presented with hip arthralgia and was found to have facial "coarseness," corneal clouding, mitral and aortic insufficiency, and hepatosplenomegaly. Ultrastructural studies of skin biopsy and peripheral blood lymphocytes showed membrane-bound inclusions containing sparse fibrillogranular material. Biochemical analysis showed elevated urinary sialyloligosaccharides and no free sialic acid. Fibroblast enzyme analysis showed low activities of both alpha-neuraminidase and beta-galactosidase. To date, most patients with juvenile galactosialidosis have been Japanese. However, unlike those patients, our patient did not have macular cherry-red spots, neurologic abnormalities, or mental retardation. We speculate that this young man represents a new subtype of juvenile galactosialidosis with a potentially different molecular defect from that of the Japanese variant.

Sialidosis and galactosialidosis: chromosomal assignment of two genes associated with neuraminidase-deficiency disorders

The inherited human disorders sialidosis and galactosialidosis are the result of deficiencies of glycoprotein-specific alpha-neuraminidase (acylneuraminyl hydrolase, EC 3.2.1.18; sialidase) activity. Two genes were determined to be necessary for expression of neuraminidase by using human-mouse somatic cell hybrids segregating human chromosomes. A panel of mouse RAG-human hybrid cells demonstrated a single-gene requirement for human neuraminidase and allowed assignment of this gene to the (pter----q23) region of chromosome 10. A second panel of mouse thymidine kinase (TK)-deficient LM/TK- -human hybrid cells demonstrated that human neuraminidase activity required both chromosomes 10 and 20 to be present. Analysis of human neuraminidase expression in interspecific hybrid cells or polykaryocytes formed from fusion of mouse RAG (hypoxanthine/guanine phosphoribosyltransferase deficient) or LM/TK- cell lines with human sialidosis or galactosialidosis fibroblasts indicated that the RAG cell line complemented the galactosialidosis defect, but the LM/TK- cell line did not. This eliminates the requirement for this gene in RAG-human hybrid cells and explains the different chromosome requirements of these two hybrid panels. Fusion of LM/TK- cell hybrids lacking chromosome 10 or 20 (phenotype 10+,20- and 10-,20+) and neuraminidase-deficient fibroblasts confirmed by complementation analysis that the sialidosis disorder results from a mutation on chromosome 10, presumably encoding the neuraminidase structural gene. Galactosialidosis is caused by a mutation in a second gene required for neuraminidase expression located on chromosome 20.

Analysis of neuraminidase isozyme phenotypes in mammalian tissues: an electrophoretic approach

A simple cellulose acetate electrophoretic method for visualizing mammalian neuraminidase isozymes has been developed. Application of the method with rat and mouse liver extracts reveals the presence of two distinct isozymes in each species. Each isozyme exhibits tremendous variation in activity between inbred strains. The two isozymes vary independently of one another suggesting that their activities are controlled by different genes. The neuraminidase phenotypes detected in these inbred strains via electrophoresis are consistent with published accounts of neuraminidase phenotypes determined fluorometrically in whole liver homogenates, but also indicate the presence of a second isozyme not perceived by this other procedure.

Lysosomal enzymes in ataxia: discovery of two new cases of late onset hexosaminidase A and B deficiency (adult Sandhoff disease) in French Canadians

We have measured in leukocytes the following lysosomal enzymes in 11 Friedreich disease cases, 11 "atypical" recessive ataxias, 13 neurological controls and 16 normal controls: hexosaminidase A and B; beta-galactosidase and neuraminidase (labile and cold stable, or A and B). The lysosomal enzyme deficiencies known to produce certain forms of spinocerebellar degeneration were not present in Friedreich's disease or the Charlevoix-Saguenay syndrome. The very small scale survey of "atypical" recessive ataxias revealed 3 cases of severe deficiencies in hexosaminidase activity. Two adult brothers presenting with the clinical phenotype of Kugelberg-Welander disease (one also with ataxia), were shown to have a severe deficiency of both HEX A and HEX B activity (Sandhoff biochemical pattern). This is the first such report. A further adult female patient, unrelated to the others, had a severe isolated deficiency of HEX B and presented with a very slowly progressive and mild ataxia with severe internal strabismus. These patients and their families are being studied clinically and biochemically in greater detail and will be reported elsewhere. However these preliminary findings justify screening for such lysosomal defects in all cases of "atypical" recessive ataxia.

Combined sialidase (neuraminidase) and beta-galactosidase deficiency. Clinical, morphological and enzymological observations in a patient

A patient with combined deficiency of sialidase and beta-galactosidase is described. This now 39-year-old man, who is of Japanese origin, showed gradually progressive clinical features from the age of six years. Many of these features are commonly found in sialidosis type 2 or in GM1-gangliosidosis. Both sialidase and beta-galactosidase activities were deficient in leucocytes and cultured fibroblasts. Leucocytes of his mother showed activities of both enzymes in the lower limit of the control range. Morphologically, the pattern of storage products in a skin biopsy resembled in many respects that seen in GM1-gangliosidosis. Moreover, storage products which could be typical of sialidosis were also observed. Since the patient showed angiokeratomata, the morphological findings were compared with those specific to Fabry's disease, but no similarities were found. An enzymological diagnosis of the disease is most reliable on cultured fibroblasts, discriminating it from sialidosis type 2 and GM1-gangliosidosis. In view of recent findings, leucocytes seem to be less suitable for the establishment of the diagnosis galactosialidosis.

Apparent allelism of the Hurler, Scheie, and Hurler/Scheie syndromes

The Hurler, Scheie, and Hurler/Scheie syndromes are clinically distinct disorders due to inherited deficiencies of lysosomal alpha-iduronidase activity. The genetic relationship of these disorders was investigated by complementation analysis using a heterokaryon enrichment procedure. Fusions between fibroblasts derived from Hurler, Scheie, or Hurler/Scheie subjects in any combination resulted in no detectable correction of alpha-iduronidase activity, indicating that they form a single complementation group. Control fusions between these fibroblasts and mucolipidosis II or III cells, which are also alpha-iduronidase deficient due to an enzyme processing defect, resulted in restoration of up to 57% of normal alpha-iduronidase activity. These results also suggest allelism of the Hurler, Scheie, and Hurler/Scheie syndromes. However, the genetic make-up of the Hurler/Scheie syndrome was not resolved.

Carrier detection of sialidosis with partial beta-galactosidase deficiency by the assay of lysosomal sialidase in lymphocytes

Lysosomal and plasma membrane sialidase activities in lymphocytes were studied in four patients with sialidosis with partial beta-galactosidase deficiency, four obligate heterozygotes, and three siblings of a patient. Lysosomal sialidase activity in homozygotes was absent, and that in heterozygotes was significantly decreased to 70% of control level. The results indicate that carriers can be detected by the assay of lysosomal sialidase activity of lymphocytes.

Mucolipidosis II and III. The genetic relationships between two disorders of lysosomal enzyme biosynthesis

The genetic relationships between the multiple variants of mucolipidosis II (I-cell disease) and mucolipidosis III (pseudo-Hurler polydystrophy) were investigated with a sensitive genetic complementation analysis procedure. These clinically distinct disorders have defects in the synthesis of a recognition marker necessary for the intracellular transport of acid hydrolases into lysosomes. Both disorders are associated with an inherited deficiency of a uridine diphosphate-N-acetyl-glucosamine: lysosomal enzyme precursor N-acetyl-glucosamine-phosphate transferase activity. We had previously shown that both disorders are genetically heterogeneous. Complementation analysis between mucolipidosis II and III fibroblasts indicated an identity of mucolipidosis II with one of the three mucolipidosis III complementation groups (ML IIIA), suggesting a close genetic relationship between these groups. The presence of several instances of complementation within this group suggested an intragenic complementation mechanism. Genetic complementation in heterokaryons resulted in increases in N-acetyl-glucosamine-phosphate transferase activity, as well as in the correction of lysosomal enzyme transport. This resulted in increases in the intracellular levels of several lysosomal enzymes and in the correction of the abnormal electrophoretic mobility pattern of intracellular beta-hexosaminidase. The findings demonstrate that a high degree of genetic heterogeneity exists within these disorders. N-acetyl-glucosamine-phosphate transferase is apparently a multicomponent enzyme with a key role in the biosynthesis and targeting of lysosomal enzymes.

A severe infantile sialidosis (beta-galactosidase-alpha-neuraminidase deficiency) mimicking GM1-gangliosidosis type 1

We observed a 3-month-old Japanese female infant with severe psychomotor retardation, coarse facial appearance, hepatosplenomegaly, and dysostosis multiplex. Only beta-galactosidase was found to be deficient when the routine lysosomal hydrolase assay was performed on the patient's lymphocytes at 6 months of age. At first GM1-gangliosidosis type 1 seemed the most likely diagnosis. Later, however, additional studies (hydrolase assay in cultured skin fibroblasts, urinary oligosaccharide analysis, genetic complementation study, etc.) revealed that biochemical data of this case were in agreement with those of severe infantile sialidosis. The only important exception was that alpha-neuraminidase in the patient's lymphocytes showed normal activity but abnormal pH dependence toward 4-methylumbellyferyl substrate. In addition, a severely damaged kidney suggested that his case may be classified as a unique type of severe infantile sialidosis (possible nephrosialidosis). These observations stress the importance of careful biochemical diagnosis of a case with GM1-gangliosidosis type 1 phenotype.

Gene for glutathione S-transferase-1 (GST1) is on human chromosome 11

The glutathione S-transferases (GST) are a group of related enzymes that can detoxify potentially carcinogenic electrophiles by conjugating them with reduced glutathione (GSH). The chromosomal location of one of the enzyme forms, GST1, reported recently to be polymorphic, was determined utilizing man-mouse somatic cell hybrids segregating human chromosomes. The expression of GST1 by hybrid clones was compared with that of 34 enzyme markers representing 23 chromosomes, and karyotypes of selected cell hybrids were analyzed. The evidence indicated that GST1 is assigned to chromosome 11 in humans. Utilizing and X/11 translocation segregating in hybrids, GST1 was localized to the p13 leads to qter region of chromosome 11.