Defective high-affinity thiamine transporter leads to cell death in thiamine-responsive megaloblastic anemia syndrome fibroblasts
| Autor: | Ellis J. Neufeld, Judith C. Fleming, Amy Stagg, Massayuki Sakamoto, Meghan A Baker, Nadine Cohen |
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| Rok vydání: | 1999 |
| Předmět: |
Cellular pathology
Anemia Megaloblastic Apoptosis Deafness Article Diabetes mellitus genetics Diabetes Mellitus medicine Thiamine transporter Humans Thiamine Megaloblastic anemia Cells Cultured biology Thiamine transport food and beverages Syndrome General Medicine Fibroblasts medicine.disease Molecular biology Biochemistry Mutation biology.protein SLC19A2 Carrier Proteins human activities |
| Zdroj: | Journal of Clinical Investigation. 103:723-729 |
| ISSN: | 0021-9738 |
| Popis: | We have investigated the cellular pathology of the syndrome called thiamine-responsive megaloblastic anemia (TRMA) with diabetes and deafness. Cultured diploid fibroblasts were grown in thiamine-free medium and dialyzed serum. Normal fibroblasts survived indefinitely without supplemental thiamine, whereas patient cells died in 5–14 days (mean 9.5 days), and heterozygous cells survived for more than 30 days. TRMA fibroblasts were rescued from death with 10–30 nM thiamine (in the range of normal plasma thiamine concentrations). Positive terminal deoxynucleotide transferase–mediated dUTP nick end-labeling (TUNEL) staining suggested that cell death was due to apoptosis. We assessed cellular uptake of [3H]thiamine at submicromolar concentrations. Normal fibroblasts exhibited saturable, high-affinity thiamine uptake (Km 400–550 nM; Vmax 11 pmol/min/106 cells) in addition to a low-affinity unsaturable component. Mutant cells lacked detectable high-affinity uptake. At 30 nM thiamine, the rate of uptake of thiamine by TRMA fibroblasts was 10-fold less than that of wild-type, and cells from obligate heterozygotes had an intermediate phenotype. Transfection of TRMA fibroblasts with the yeast thiamine transporter gene THI10 prevented cell death when cells were grown in the absence of supplemental thiamine. We therefore propose that the primary abnormality in TRMA is absence of a high-affinity thiamine transporter and that low intracellular thiamine concentrations in the mutant cells cause biochemical abnormalities that lead to apoptotic cell death. J. Clin. Invest. 103:723–729 (1999). |
| Databáze: | OpenAIRE |
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