Date of Award

5-2006

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Science (MS)

Department

Biochemistry

Advisor

Joseph M. Verdi

Second Committee Member

Douglas Spicer

Third Committee Member

Lucy Liaw

Abstract

The Neurotrophins and Bone Morphogenic Proteins (BMP) have both been implicated in the maintenance of cellular proliferation and apoptosis in the developing nervous system. Downstream of both signaling pathways is NRAGE, a member of the Melanoma Antigen (MAGE) gene family and, under BMP stimulation, activates p38 leading to caspase 3 cleavage. NRAGE possesses a highly conserved MAGE Homology Domain (MHD) and a second, less well conserved MHD (denoted MHD2) as well as a unique 25 tandem WQXPXX hexapeptide repeat region. Binding partners for the MHD and hexapeptide repeat regions have been identified but their cellular consequences have not been defined. Therefore, a structure-function analysis of NRAGE was performed to identify whether it is the MHD or the repeat region that tranduces the apoptotic signal. Nine NRAGE deletion mutants were built to isolate the identified regions and expressed in PI9 cells, a neural development model system. Through Annexin V staining, it was found that the MHD is essential for apoptotic function and the hexapeptide repeat region does decrease the degree of cellular death. The MHD region also induces p38 activation and caspase 3 cleavage, as well as apoptosis. Overall, these studies ascribe yet another function to the highly conserved MHD and give further insight into the mechanisms governing neural progenitor cell apoptosis.

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