| Co-Investigator(Kenkyū-buntansha) |
ITO Hidenori Institute for Developmental Research, Depatment of Neurobiology, Researcher, 究所・神経制御学部, 研究員 (40311443)
INAGUMA Yuaka Institute for Developmental Research, Depatment of Neurobiology, Senior Researcher, 究所・神経制御学部, 主任研究員 (10250250)
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| Research Abstract |
(1)Roles of phosphorylation of αB-crystallin and Hsp27 on the formation of inclusions in cells.
Exposure of cells to a proteasome inhibitor (MG-132) or prostaglandin J2 induced activation of heat shock factor (HSF) and accumulation of insoluble protein complexes composed of ubiquitinated proteins and phosphorylated forms of αB-crystalin and Hsp27 and formation of inclusion bodies, which subsequently induced cell death. However, when an inhibitor of protein synthesis (cycloheximide, anisomycin or puromycin) was coexisted, the above described responses were suppressed. The responses inducible by MG-132 or PGJ2 were significantly suppressed in cells in which the gene for HSF1 is disrupted as compared with the responses in wild type cells. These results suggest that mechanisms of formation of inclusions in cell are closely related to the activation stste of HSF.
(2)Disused soleus muscle induced by hindlimb suspension of rats showed similar phenomena observed in cells exposed to MG-132 and th
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ese responses were disappeared by a simultaneous denervation of ipsilateral sciatic nerve, indicating the responses are mediated by nerve stimuli.
(3)Oligomerization states of αB-crystallin and Hsp27 and their phosphorylation states
Three phosphorylation sites of αB-crystallin (Ser-19, Ser-45, Ser-59) were displaced with aspartic acid, and this mutant protein was expressed in E.coli or expressed in cells. The mutant αB-crystallin did not form a oligomer. The mutant αB-crystallin expressed in cells did not show the protective effects for stress.
Stress-induced dissociation of Hsp27 was suppressed by inhibitors of protein kinases, confirming the dissociation of Hsp27 is a result of phosphorylation.
(4)Phosphorylation of αB-crystallin at Ser-59 was found to be enhanced in centrosomes and midbodies of mitotic cells.
(5)Mechanisms of induction of Hsp27 in cells by several bioactive agents were clarified.
(6)We found that p20 and αB-crystallin in vascular smooth muscle cells act extracellularly as a modulator of platelet functions. Less
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