1993 Fiscal Year Final Research Report Summary
Molecular mechanism of abnormal hemolysis in paroxysmal nocturnal hemoglobinuria
| Project/Area Number |
04671530
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
Hematology
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| Research Institution | Kumamoto University |
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Principal Investigator |
NAKAKUMA Hideki Kumamoto University school of Medicine, Lecturer, 医学部, 講師 (90207746)
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| Project Period (FY) |
1992 – 1993
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| Keywords | PNH / Hemolysis / GPI anchor / GlcNAc / T cell lines |
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| Research Abstract |
Paroxysmal nocturnal hemoglobinuria (PNH) is currently accepted as being due to a somatic mutation of stem cells that is clonal in nature and that leads to an increaased susceptibility of the affected blood cells to autologous complement. The increase in sensitivity is mainly explained by a deficiency in such complement regulatory membrane proteins as decay-accelerating factor (DAF) and CD59. These proteins are covalently attached to the cell membrane by glycosylphosphatidylinositol (GPI)-anchor structures and share a common carbohydrate structure (core sequence). Regarding the step at which mutation may affect the biosynthesis or breakdown of this GPI-anchor, or the anchoring process of the proteins, recent investigations suggest a defect in the anchor synthesis in affected cells. We then prepared sufficient affected cells by establishing cultured T cell lines with PNH phenotype using human T-lymphotropic virus type 1 (HTLV-1). Using the cultured T cells, we soon examined the interruption site in the synthesis of the anchor by biochemical analysis. An results, metabolic labeling with [^3H]sugars in vivo or [^3H]sugar nucleotides in vitro of the GPI-anchor precursors showed a synthetic defect of the GPI-anchor. Among the precursors, phosphatidylinositol (PI) was normally produced, while glucosaminyl-PI and subsequent mannolipids were not synthesized. The defect in the synthesis of GPI-anchor in PNH is thus attributed to interrupted glycosylation (impaired trasfer of N-acetylglucosamine) in the core structure of the anchor.
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