| Research Abstract |
For these ten years we have studied the pathogenetic mechanism of globoid cell leukodystrophy, a genetic demyelinating disorder deficient in galctosylceramidase I activity, and reported that galactosylsphingosine, a lyso compound of galactosylceramide, accumulates in the tissue of the patients and suggested that the cytotoxicity of the acumulated lysocompound leads to the cell death and subsequent demyelination. We have also the accumulation of lysocompounds in other lipid storage diseases such as GM1 gangliosidosis and metachromatic leukodystrophy. For one of the treatment of these lipid storage diseases we hypothesized if we could detoxicate the accumulated lysosphingolipids, and we obtained some data on this project as follows :
1. In 1994, we examined the synthetic pathway of the lysosphingolipid, When conduritol B epoxide (CBE), a competitive inhibitor of beta-glucosidase, was included in the medium of cultured fibroblasts, the accumulation of glucosylsphingosine, a lysocompound of
… More
glocosylceramide, was observed. The accumulated glucosylsphingosine was dependent on the dose of added CBE.Next, we added in the medium both CBE and PDMP, an inhibitor of glucosylceramide synthesis, and found the deceased accumulation of glucosylsphingosine. From these data we concluded that the synthesis of glucosylsphingosine is catalyzed not only by the glucosylation of sphingosine but also by the deacylation of glucosylceramide.
2. In 1995, we examined the degradative pathway of the lysospingolipid. For this purpose, we characterized molecular properties of galactosylceramidase I, a degrading enzyme of galactosylsphingosine and found mutations in adult patients with globod cell leukodystrophy. We obtained cDNA fragments of the gene after amplification by PCR from the patients and sequenced the total nucleotides in the amino acid coding region. In the 4 patients, we found new point mutations which replace evolutionally-conserved amino acids to others. We are now atempting to confirm that the mutations found in the patients are causative for the deficiency of the enzyme activity by expression of the mutated cDNA in eucaryotic cells. Less
|
