1991 Fiscal Year Final Research Report Summary
Induction mechanism and physiological role of autophagy in yeast and plant cell.
| Project/Area Number |
02454009
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
植物生理学
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| Research Institution | The University of Tokyo |
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Principal Investigator |
OHSUMI Yoshinori The University of Tokyo, College of Arts and Sciences, Assistant Proffessor, 教養学部, 助教授 (30114416)
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| Project Period (FY) |
1990 – 1991
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| Keywords | Yeast / autophagy / vacuole / acidic compartment / protein turnover / cell cycle |
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| Research Abstract |
It was first shown that yeast, Saccharomyces cerevisiae, shows extensive autophagic activity. It provides a good model system for understanding autophagy at molecular level. Summary of research in these two years are follows. (1) By using vacuolar proteinases-deficient mutants autophagy was demonstrated with light microscope ; under various nutrient-defifient conditions spherical bodies containing cytosolic components, named autophagic bodies, accumulated in the vacuoles within 3-4 hours. (2) Dynamic behavior of intracellular membranes in the cell under nutrientdeficient condition was investigated by electron microscope using rapidfreezing and freeze-substitution methods. Then we proposed a model for autophagy in yeast cells. (3) By using mutants of cAMP-signal pathway cAMP was shown to be a negative regulator of autophagic process in yeast. (4) Mutants of vacuolar membrane proton ATPase still accumulated autophagic bodies under nutrient starvation into their vacuoles. It was concluded that in contrast to animal cell acidification of vacuole (lysosome) was not essential to autophagy in yeast. (5) Vacuolar proteinase B was shown to be the most responsible enzymes to degrade the autophagic bodies in the vacuoles by biochemical and molecular genetical analyses. (6) Under nitrogen starvation condition wild type cell proceed its cell cycle to Gl. However, vacuolar proteinase-deficient cells or mutants cell activated CAMP pathway failed to arrest to G1 and rapidly lost their viability. It was suggested that bulk turnover of proteins by autophagy is obligatory to provide amino acids to proceed their cell cycle. (7) Mutants difective with autophagic process were isolated under light microscope. Various genes involved in the whole process of autophagy may be identified.
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