Glutamate-induced oxidative toxicity in HT22 cells and primary immature cortical cultures provides an excellent model system for studying oxidative stress-dependent neurodegeneration. Glutamate treatment leads to cysteine and subsequent glutathione depletion, followed by the steady accumulation of reactive oxygen species (ROS). This form of cell death depends upon the persistent activation, via phosphorylation, of extracellular signal regulated kinase (ERK) kinase-1/2 (ERK-1/2) that occurs during oxidative stress. However the mechanisms responsible for this chronic activation of ERK during oxidative stress have not been well characterized. In this thesis, I demonstrate that ERK activation is dependent upon the tonic activity of the phosphatidylinositol-3-kinase (PI3K)-Akt pathway and the subsequent activation of MEK. Furthermore, the persistent ERK activation that leads to cellular toxicity can be driven by the oxidative-dependent inactivation of ERK-phosphatases. Thus the balance of activating kinase activity and inactivating phosphatase activity dynamically regulates ERK-dependent signaling and is a major determinant of neuronal cell responses to oxidative stress. The overexpression of a negative regulator of the ERK MAPK pathway, the ERK-specific phosphatase MKP3, led to protection of both HT22 cells and primary immature cortical cultures from oxidative toxicity. Furthermore, a catalytically inactive form of MKP3 (MKP3 C293S) was shown to physically restrict activate ERK to the cytoplasm. Because overexpression of MKP3 C293S was also shown to be neuroprotective, translocation of active ERK to the nucleus, but not ERK activation alone, must be required for glutamate-induced oxidative toxicity. Collectively, these results clearly place ERK activation as a necessary event that leads to neuronal cell death during oxidative stress and have revealed some unique mechanisms by which ROS accumulation drives ERK activation.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-07112004-190700 |
| Date | 24 September 2004 |
| Creators | Levinthal, David Justin |
| Contributors | Dr. Edda Thiels, Dr. Teresa Hastings, Dr. Ian Reynolds, Dr. Donald DeFranco, Dr. Elias Aizenman, Rajiv Ratan |
| Publisher | University of Pittsburgh |
| Source Sets | University of Pittsburgh |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.pitt.edu/ETD/available/etd-07112004-190700/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Pittsburgh or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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