Dissertation > Excellent graduate degree dissertation topics show

Effects of Proteasome Inhibition on Microtubule-associated Protein Tau Phosphorylation and the Underlying Mechanism

Author: ChangJunLi
Tutor: LiaoXiaoMei
School: Central China Normal University
Course: Zoology
Keywords: Proteasome tau GSK-3β Akt Hsp90
CLC: R749.16
Type: Master's thesis
Year: 2011
Downloads: 78
Quote: 0
Read: Download Dissertation

Abstract

Hyperphosphorylated tau protein aggregation and the formation of neurofibrillary tangles (neurofibrillary tangles, NFTs) of Alzheimer's disease (Alzheimer's disease, AD) and chromosome 17 frontotemporal dementia and Parkinson's disease (Parkinson's disease , one of the main neuropathological features of PD) and other tau-related diseases. But so far, led to tau hyperphosphorylation and the formation of NFTs mechanism has not yet been fully elucidated. Not only tau protein phosphorylation, and its ubiquitination may also promote the formation of NFTs. Ubiquitin - proteasome system (ubiquitin-proteasome system, UPS) E3 ubiquitin ligase phosphorylation of tau protein ubiquitin, and proteasome activity is reduced tau-related diseases, that UPS may affect tau protein over- phosphorylation. In addition, glycogen synthase kinase-3β (glycogen synthase kinase-3β, GSK-3β) and protein kinase B (protein kinase B, of PKB / Akt) is also abnormal tau protein phosphorylation plays a key role, Akt GSK- 3β upstream kinase, and heat shock protein 90 (heat shock protein 90, of Hsp90) and Akt between changes in the degree of integration can regulate Akt protein content and activity change. This article with stable expression human tau441 isomer human Wilms tumor cell line (human embryonic kidney 293 cells, HEK293/tau441) as the basic material, with a specific inhibitor of the 20S proteasome lactacystin and protein synthesis inhibitors actinomycetes ketone ( cycloheximide, CHX), the cells were treated for 24 h, phosphorylation sites of tau protein by immunoblotting, immunofluorescence and co-immunoprecipitation to detect proteasome inhibition, protein kinase GSK-3β of Akt and heat shock protein and protease the interaction between the body with GSK-3β and proteasome and Akt, to investigate the mechanisms of proteasome inhibition may lead to hyperphosphorylation of tau protein, the results are as follows: (1) inhibition of proteasome activity of total tau protein and phosphorylated the degree of the impact of proteasome inhibition can induce increased total tau protein, tau-Thr231 in the brain, Ser396, Thr205 and Ser195/198/199/202 bit of the degree of phosphorylation increased, suggesting that tau and phosphorylated tau protein are protease substrate body Degradation. But after proteasome inhibition decline in the degree of phosphorylation of tau-Ser214 sites. (2) the proteasome and the relationship between GSK-3β GSK-3β is one of the major kinases regulate tau protein phosphorylation, proteasome inhibition caused by tau protein hyperphosphorylation modification sites (Thr231 in the brain, Ser396 both Thr205 and Ser195/198/199/202), regulation of GSK-3β sites To illustrate the activity of the proteasome inhibition mechanism induced tau phosphorylation degree, this experiment detected the system of GSK-3β content and The change in activity. The results showed that the inhibition of the proteasome reduce the degree of phosphorylation of GSK-3β-Ser9 sites, Since this locus extent of phosphorylation of GSK-3β activity was negatively correlated, so the results show that proteasome inhibition activity of GSK-3β liter high, proteasome inhibition the tau-Thr231, Ser396, Thr205, and Ser195/198/199/202 sites hyperphosphorylation of consistent, indicating that proteasome indirect regulation of tau phosphorylation by regulating the activity of GSK-3p. Also detected the activity of the proteasome inhibition of GSK-3p elevated protein content, and immunofluorescence and immunoprecipitation detected the intracellular 20S proteasome and GSK-3p between colocalization and coprecipitation relationship, suggesting that cells inner GSK-3p may be proteasome substrate. (3) the relationship between the proteasome and Akt Akt both GSK-3p upstream kinases are also sites of tau-Ser214 phosphorylation regulated kinase, this study further examined proteasome inhibition of Akt protein kinase content and activity the impact. Found that proteasome activity is inhibited Akt's Ser473 and Thr308 sites of the degree of phosphorylation with increasing lactacystin concentration decreased Akt's Ser473 and Thr308 regulatory sites of Akt activity, these two sites phosphorylated minimize that Akt activity down the degree of phosphorylation of GSK-3β-Ser9 and tau-Ser214 sites with inhibition of proteasome activity to reduce consistent, suggesting that proteasome activity inhibition of to indirectly regulate tau protein by regulating the activity of Akt phosphorylation . The study also found that when the proteasome activity was inhibited, the intracellular Akt protein content increased, while the immunofluorescence and immunoprecipitation both 20Sproteasome and Akt in the intracellular co-localization and co-precipitation relationship, which results demonstrate that Akt may also proteasome substrate. (4) the activity of the proteasome to inhibit the change in the level of the influence of heat shock protein Hsp90 and Akt combination can regulate the activity of Akt, and therefore cause Akt activity downward adjustment mechanism in order to further detect the inhibition of the proteasome activity, the present assay intracellular proteasome inhibition of Hsp90 and Hsp70 content. The results found that inhibition of proteasome activity in the cells of heat shock protein family members Hsp90 and Hsp70 levels increased. Therefore speculated that when the proteasome degradation system is hindered, the abnormal accumulation of the protein will stimulate cellular stress leading to cell heat shock protein rapidly produce, to restore the normal function of the proteins of these aggregates. But the content proteasome inhibition induced increase of Hsp90 and Akt how to change the degree of integration needed into an experimental study. In conclusion, proteasome inhibition on regulation of tau phosphorylation by the following means: ① proteasome degradation of tau protein and phosphorylated tau protein; ② proteasome indirect regulation by regulation of GSK-3p and Akt activity tau phosphorylation; the ③ proteasome inhibition can induce Hsp90 and Hsp70 content. Proteasome inhibition causes increased Hsp90 content may be involved in the regulation of Akt activity, but how to adjust the need for further experimental studies.

Related Dissertations

CLC: > Medicine, health > Neurology and psychiatry > Psychiatry > Cerebral organic mental disorder > Elderly as early as possible the old disorder
© 2012 www.DissertationTopic.Net Mobile