| Project/Area Number |
05680570
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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 |
Biophysics
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| Research Institution | TOHOKU UNIVERSITY |
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Principal Investigator |
KOBAYASHI Toshihide TOHOKU UNIVERSITY,FAC.OF SCIENCE,DEPT.OF PHYSICS,ASSOCIATE PROFESSOR, 理学部, 助教授 (60162004)
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| Co-Investigator(Kenkyū-buntansha) |
OHKI Kazuo TOHOKU UNIVERSITY,FAC.OF SCIENCE,DEPT.OF PHYSICS,PROFESSOR, 理学部, 教授 (80115394)
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| Project Period (FY) |
1993 – 1994
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| Project Status |
Completed (Fiscal Year 1994)
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| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1994: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1993: ¥1,700,000 (Direct Cost: ¥1,700,000)
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| Keywords | Flip-flop / Flippase / Membrane lipid asymmetry / Endocytosis / CHO cell / Plasma membrane / Fluorescent lipid analog / Phosphatidylserine / CHO |
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| Research Abstract |
Flippases are membrane proteins which catalyze transbilayr movement (flip-flop) of membrane lipids. Structure of flippases are not well understood. Up to now several flippases have been reported. Among them, plasma membrane flippase has been studied well. This protein catalyzes transbilayr movement of cell surface phosphatidylserine in ATP-dependent manner. The function of cell surface flippase is not known. It has been proposed that plasma membrane flippase is involved in the maintenance of plasma membrane lipid asymmetry and/or endocytosis.
Previously we have suggested that exogenous phosphatidylserine is internalized via cell surface flippase (Kobayashi, T.and Arakawa, Y.(1991) J.CellBiol., 113,235-244). In the course of studying the internalization of exogenous phosphatidylserine into cells, we found that phosphatidylserine which has unsaturated fatty acid has cytotoxicity. Assuming that phosphatidylserine-resistant cells are defective in the first step of internalization of phosphatidylserine i.e.flip-flop on the plasma membrane, we have isolated phosphatidylserine-resistant mutants. 40% of phosphatidylserine-resistant cells were defective in transbilayr movement of cell surface phosphatidylserine. Using these mutants, we have measured 1) asymmetry of membrane lipids and 2) activity of endocytosis. Phosphatidylserine-resistant mutants retained lipid asymmetry. On the other hand, endocytosis activity of mutant cells, measured by using lucifer yellow and horse radish peroxidase (HRP), was about half of that of wild type CHO cells. Our results suggest that flip-flop of membrane phospholipids are involved in endocytosis.
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