| Budget Amount *help |
¥14,800,000 (Direct Cost: ¥14,800,000)
Fiscal Year 2006: ¥4,300,000 (Direct Cost: ¥4,300,000)
Fiscal Year 2005: ¥10,500,000 (Direct Cost: ¥10,500,000)
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| Research Abstract |
A. Analysis of signaling mechanism of autophagy by amino acids
1) Analysis of LC3 as a target of amino acid signaling
It was demonstrated that the transformation of LC3, a marker protein for macroautophagy formation, was transformed from a precursor form LC3-I to an active and membrane-bound form LC-II, and regulated by amino acids, proving that this molecule on the autophagosomal membrane is a target of amino acid signaling. Through subcellular factionation study, a new form of LC3-II, termed as LC3-IIs, was found in the cytosol. When the hydrophobicity was tested by phase-partitioning with Triton X-114 and the lipidation were investigated by hAtg4B treatment, it was concluded that cytosolic LC3-IIs was hydrophilic and delipidated, and was different from a typical LC3-II.
B. Regulation of autophagy by food components
1) Mechanism of autophagy by vitamin C
Stimulating effect of vitamin C (Ascorbic Acid, AsA) was demonstrated only with amino acids, indicating that both effectors may have a common mechanism. From the results that dehydroascorbic acid also exhibited an equal effect as AsA, the anti-oxidative function of AsA may not be related to the effect on autophagy. In ODS rats, defective of AsA synthesis and devoid of AsA in the liver, it still kept the potency to stimulate autophagy. Even when the cells were inhibited at the transport of AsA by choline chloride, the potency of AsA was not disappeared, which strongly suggests that AsA acts through extracellularly.
2) Relationship of autophagy and anti-oxidants
Anti-oxidant vitamin E also exhibited the stimulating effect, but did not need amino acid co-existence. Epigallocatechin gallate from tea, also exhibited a similar effect as vitamin E. In contrast, vitamin B6 showed inhibitory effect on autophagy. All these results strongly suggest that there may be many compounds to control autophagy in foodstuffs.
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