| Project/Area Number |
63560292
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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 |
基礎獣医学
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| Research Institution | University of Osaka Prefecture |
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Principal Investigator |
OHISHI Iwao University of Osaka Prefecture, College of Agriculture Associate Professor, 農学部, 助教授 (50081592)
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| Project Period (FY) |
1988 – 1989
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| Project Status |
Completed (Fiscal Year 1989)
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| Budget Amount *help |
¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 1989: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1988: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Keywords | Botulinum toxin / Botulinum C_2 toxin / Nonmuscle actin / ADP-ribosylation / Tissue-cultured cells / Cytoskeleton / C_2毒素 / アクチン |
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| Research Abstract |
Botulinum C_2 toxin, elaborated by Clostridium botulinum types C and D, is composed of two dissimilar unassociated proteins, designated components I and II. Component I catalyzes ADP-ribosylation of nonmuscle actin but not of muscle actin. The purpose of present study was to clarify the mechanism of action of the toxin by examining the response of tissue-cultured cells to the toxin and by characterizing ADP-ribosylated nonmuscle actin.
The morphology of tissue-cultured cells exposed to C_2 toxin changed markedly although it varied depending on the strain of the cells and the dose of the toxin. This morphological change in the cells was parallel to the ADP- ribosylation of the intracellular actin by the toxin. The fluorescence staining of cytoplasmic actin showed that the stressfibers in tissue-cultured cells exposed to the toxin were disassembled and thereafter disappeared. The maximal level of ADP-ribosylation of purified nonmuscle actin was about 1.0 mole of ADP-ribose/mol of actin. In addition to the inactivation of self-polymerization ability, the ADP-ribosylated actin affected neither the initial rate nor the final extent of polymerization of unmodified actin as monitored by the increase in fluorescence intensity. These results indicate that the introduction of one ADP-ribose residue into the beta/gamma-actin molecule by component I inactivated the actin, preventing not only the self-assembly of the modified actins but also the interaction with-unmodified actin. The present study suggest that ADP- ribosylation of intracellular actin by C_2 toxin inactivates interaction between unmodified and modified actins and shifts the dynamic equilibrium between the monomeric and polymeric forms to the depolymeried state, thereby leading to the disintegration of cytoskeletal matrix, and consequently to the death of the cells.
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