| Co-Investigator(Kenkyū-buntansha) |
YAMADA Hiroshi Okayama University, Graduate School of Medicine and Dentistry, Assistant, 大学院・医歯学総合研究科, 助手 (80325092)
KINUTA Masahiro Okayama University, Graduate School of Medicine and Dentistry, Lecturer, 大学院・医歯学総合研究科, 講師 (40135942)
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| Research Abstract |
Establishment of in vitro cell-free system: In order to elucidate molecular mechanisms involved in endocytosis, vesicle formation in endocytosis was reconstituted in vitro. Incubation of large liposomes, larger than 1 μm in diameter, with brain cytosol resulted in massive formation of small vesicles, smaller than 100 nm in diameter. The vesicle formation required both ATP and GTP. Vesicle formation was drastically reduced when liposomes were incubated with dynamin 1 -depleted cytosol, indicating that vesicle formation in this experimental system represents endocytic vesicle formation. The vesicle formed during the incubation can be analyzed quantitatively and qualitatively by dynamic light scattering.
Functions and Kinetics of membrane lipids: Functions of membrane lipids were studied by analyzing vesicle formation from liposomes of with various compositions. Vesicle formation increased as phosphatidylinositol-4.5-bisphosphate (PIP_2) concentration in liposomes was increased. Furthermore, PIP_2 was degraded to phosphatidylinositol-4-bisphosphate, then to phosphatidylinositol. Next, PIP_2 synthesis during the reaction was analyzed by addition of neomycin, inhibitor for PIP_2 degradation, in the reaction mixture. PIP_2 synthesis was increased by active form of ADP-ribosylation factor 6 (Arf6). It was suggested that increase of membrane recruitment of AP2, clathrin adaptor protein, by Arf6 might attribute to the increase of PIP_2 synthesis.
Kinetics of membrane lipids in culture cells: Degradation of PTP_2 synthesis upon endocytosis was examined in culture cells. Metabolically labeled HeLa cells were stimulated for endocytosis and the amount of PIP_2 was analyzed. Similar PIP_2 degradation as that observed in the cell-free system was observed.
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