2000 Fiscal Year Final Research Report Summary
Analysis of intracellular regulatory signaling for apoptosis induction
| Project/Area Number |
11480208
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| Research Category |
Grant-in-Aid for Scientific Research (B).
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Cell biology
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
YONEHARA Shin Kyoto University, Institute for Virus Research, Professor, ウイルス研究所, 教授 (00124503)
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| Co-Investigator(Kenkyū-buntansha) |
LEE Kyung-won Kyoto University, Institute for Virus Research, Instructor, ウイルス研究所, 助手 (50303912)
SAKAMAKI Kazuhiro Kyoto University, Institute for Virus Research, Associate Professor, ウイルス研究所, 助教授 (20271017)
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| Project Period (FY) |
1999 – 2000
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| Keywords | Fas / cell death / apoptosis / Ras / MAP kinase / caspase / FLASH / Tax |
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| Research Abstract |
We analyzed molecular mechanisms of intracellular signaling of Fas-mediated apoptosis and its regulation.
1. We cloned a cDNA encoding a novel 220 kDa protein, designated FLASH, that interacts with the death effector domain (DED) of either caspase-8 or FADD through its DED-like region. Association of Fas and FLASH was observed following stimulation of Fas, indicating that FLASH is a component of DISC.Transient expression of FLASH promoted the activation of caspase-8.
2. By an expression cloning method using Fas-transgenic Balb3T3 cells, we identified proto-oncogene c-k-ras to inhibit Fas-mediated apoptosis. Transient expression of K-Ras mutants revealed that oncogenic mutant K-Ras (RasV12) strongly inhibited, whereas dominant-inhibitory mutant K-Ras (RasN17) enhanced, Fas-mediated apoptosis by inhibitinz Fas-triggered activation of caspases without affecting an expression level of Fas. Among the target molecules of Ras, only constitutive active form of Raf could inhibit Fas-mediated apoptosis. Further analyses clearly indicate that the activation of MAPK and then CREB through Ras inhibits Fas-mediated apoptosis in Balb3T3 cells, which may play a role in oncogenesis.
3. p40Tax, an oncogene product of HTLV-1, was shown to inhibit Fas-mediated apoptosis in Balb3T3 cells through activating CREB by analyses with various mutants of Tax and dominant-negative CREB.Surprisingly, in T lymphoma cell line, p40Tax inhibits Fas-mediated apoptosis through activating NF-kB but not CREB.Thus, p40Tax negatively regulates Fas-mediated apoptosis by different molecular mechanisms (activation of CREB or NF-kB) in different cells.
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