2004 Fiscal Year Final Research Report Summary
Analysis of Intracellular Signal Transduction mediated by Death-inducing Receptors
| Project/Area Number |
14370245
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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 |
Pediatrics
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| Research Institution | Mie University |
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Principal Investigator |
KOMADA Yoshihiro Mie University, Faculty of Medicine, Professor, 医学部, 教授 (80186791)
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| Co-Investigator(Kenkyū-buntansha) |
AZUMA Eiichi Mie University, Universty Hospital, Associate Professor, 医学部附属病院, 助教授 (50211008)
HORI Hirroki Mie University, Faculty of Medicine, Associate Professor, 医学部, 助教授 (40252366)
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| Project Period (FY) |
2002 – 2004
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| Keywords | Apoptosis / Fas receptor / TRAIL receptor / Inhibitory Protein of Apoptosis / Caspase / Leukemia / Neuroblastoma |
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| Research Abstract |
We investigated Tumor necrosis factor-related apoptosis-inducing ligand(TRAIL) sensitivity and TRAIL-induced apoptosis signaling pathway in a panel of leukemia cell lines. TRAIL receptor-2 (DR5) plays an important role in transducing apoptosis signals. DR5 was internalized into the cytoplasm where it recruited Fas-associating protein with death domain/FADD under TRAIL stimulation in both sensitive and resistant cells. However, active form of caspase-8 was recruited to FADD and there was increased caspase-8 activity upon TRAIL stimulation only in sensitive cells. Caspase-8 specific inhibitor Z-IETD completely abrogated TRAIL-induced apoptosis. These results suggest that TRAIL resistance is due to negative regulation at the level of caspase-8 activation and caspase-8 activation is an indispensable process in TRAIL induced apoptosis. However, FLICE inhibitory protein was similarly expressed and down-regulated after TRAIL stimulation in both sensitive and resistant cells. Interestingly, in
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some cell lines, TRAIL sensitivity and caspase-8 activity could be enhanced or restored with the treatment of cycloheximide(CHX). In addition, the levels of XIAP decreased significantly and rapidly following treatment with CHX. Down-regulation of X-linked inhibitor of apoptosis/XIAP may be responsible for enhancement or restoration of TRAIL sensitivity after CHX treatment in leukemia cells.
We also evaluated sensitivity of a series of neuroblastoma(NB) cell lines to Fas ligand induced-cell death. Sensitivity did not correlate with the expression of Fas but was directly associated with the pattern of caspase 8 protein expression. Majority of NB cell lines lacked caspase 8 expression and these cell lines were invariably resistant to Fas-mediated cell death. In contrast, cell lines expressing normal caspase 8 protein were quite sensitive to Fas-mediated cell death. More interestingly, a group of cell lines expressing distinct short form of caspase 8 with splicing out of exon 3 consistently showed moderate sensitivity to Fas-mediated cell death. These results indicate that the profile of caspase 8 expression is an important determinant of the response of NB cells to Fas-mediated cell death. Less
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