67(P-45) 植物細胞のモノテルペノイドによるアポトーシス : アポトーシスの際に変化する細胞内蛋白質(ポスター発表の部)

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Recently, it was demonstrated that geraniol has potent apoptosis-inducing activity in various plant cells. In order to clarify the mechanism responsible for induction of apoptosis in plant cells by geraniol, we examined quantitative and qualitative alterations of proteins in the cultured cells of Nicotiana tabacum that had been treated with geraniol. Change of the proteins in the initial stage of apoptosis We demonstrated that the expression of the 53-kDa protein was markedly decreased prior to the induction of DNA fragmentation by geraniol in the cultured cells of N. tabacum. A homology search using the amino acid sequencer of the 53-kDa protein revealed that the sequences were identical to those of two regions of calreticulin. These findings suggest that decreases in levels of calreticulin might be associated with the induction of apoptosis by geraniol in the cultured cells. Protease which digests calreticulin To clarify the digestion process of calreticulin, a protease which increased in the initial stage of apoptosis was searched from the cytoplasm of the cells which treated with geraniol. A cysteine protease was purified by anion-exchange and molecular sieve chromatography; it was 450-fold pure against the cytoplasm fraction. When calreticulin is incubated with this cystein protease, a new peptide fragment at 3520Da was observed by MALDI TOF-MS. Since calreticulin possesses a short import signal for endoplasmic reticulum at the C-terminal, this cleavage indicates that the modified calreticulin cannot return to endoplasmic reticulum any longer. In general, calreticulin is a Ca^<2+>-binding molecular chaperone of the lumen of the endoplasmic reticulum. Therefore, inflow of calreticulin and/or Ca^<2+> promotes the apoptosis in the plant cells by changing Ca^<2+> signaling pathway. These findings indicate a novel mechanism by which cytoplasmic Ca^<2+> signaling is modulated to cause apoptosis by a resident protein of the endoplasmic reticulum, calreticulin.
天然有機化合物討論会の論文
2002-09-01

67(P-45) 植物細胞のモノテルペノイドによるアポトーシス : アポトーシスの際に変化する細胞内蛋白質(ポスター発表の部)

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