| Summary: | 博士 === 國立清華大學 === 生命科學系 === 87 === Intermediate filaments are major components of cytoskeleton to maintain normal cell shape and cell function. Although there are several reports to describe the reorganization of intermediate filament organization during stress, the exact profile has not been elucidated completely. The main purpose of this thesis was to elucidate the involvement of intermediate filaments during stress conditions, mainly heat shock and protein phosphatase inhibitor treatment. That could help expedite understanding of intermediate filaments.
We have focused on the elucidation of the role of vimentin, one class of intermediate filaments which is expressed in almost all cell cultures and mesodermal cells, in the stress response. In Chapter II experiments are described confirming the reorganization of vimentin during heat shock stress. A hypothesis describing how vimentin initiate the mechanism of enhanced HSC70 expression during heat shock to protect cells is provided. In Chapter III we analyzed the characteristics of the okadaic acid-induced reorganization and hyperphosphorylation of intermediate filaments. We demonstrate a new vimentin kinase, mitogen-activated protein kinase-activated protein kinase-2 (MAPKAPK-2), would be involved in the hyperphosphorylation and reorganization of vimentin induced in okadaic acid treatment. Since MAPKAPK-2 is a new vimentin kinase, we further characterize the enzymatic activity toward vimentin, and the phosphorylation site as well as the alterations of assembly properties of MAPKAPK-2-phosphorylated vimentin in Chapter IV. Chapter V deals with the role of protein phosphatases in interphase as well as stressed cells. We demonstrate that type 2A protein phosphatase, but not type 1 protein phosphatase, would associate with vimentin intermediate filament to maintain the phosphate turnover as well as the low phosphate content of intermediate filaments.
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