Date of Award

2010

Level of Access Assigned by Author

Campus-Only Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Interdisciplinary Program

Advisor

Joseph M. Verdi

Second Committee Member

Samuel T. Hess

Third Committee Member

Keith W. Hutchison

Abstract

We created a small peptide that can inhibit NF-KB activation and apoptosis in P19 neural progenitor cells. NF-KB is a ubiquitous protein complex found in almost all mammalian cell types that regulates transcription of genes in response to inflammation, immunological insults, cell proliferation, and apoptosis. Apoptosis is a form of programmed cell death, which is the death of a cell by any means that is mediated by an intracellular program. This process is used in normal growth and development of organisms by removing cells that are unhealthy or by reducing a surplus of an unnecessary population as in shaping organs. However, uncontrolled apoptosis is the basis of many diseases that can endanger survival of the organism. For example, it can be overcompensating causing too much cell death as in neurodegenerative disorders such as Parkinson's and Alzheimer's diseases or under compensating allowing too much cell proliferation as in some cancers. Here, we investigated the interaction between neurotrophin receptor-interacting melanoma-associated antigen (NRAGE) protein and X-linked inhibitor of apoptosis (XIAP) protein in a specific apoptotic cell signaling pathway that is mediated by bone morphogenetic protein (BMP). We used fluorescence resonance energy transfer (FRET) to conclude that a direct interaction is very likely occurring between XIAP and the NRAGE domain consisting of 25 hexameric amino acid repeats of tryptophan-glutamine-x-proline-x-x (x=any amino acid). FRET is a microscopy technique in which a fluorescent donor molecule transfers its energy to a fluorescent acceptor molecule if the molecules are within 10 nanometers of each other (along with other satisfied parameters) strongly suggesting a direct interaction. The repeat domain in NRAGE, which is not found in any other protein except for NRAGE homologs in human, mouse, and rat, was used to create a peptide mimetic that inhibits apoptosis from BMP signaling. Additionally, it was also found to inhibit NF-KB activation precluding transcription of NF-KB target proteins. NRAGE-XIAP interaction in BMP signaling for apoptosis may be a candidate pathway to inhibit in certain diseases in which there is too much cell death and initiates an immune response from NF-KB activation. One such disease is multiple sclerosis which is an autoimmune neurodegenerative disease where the myelin sheaths around the axons in the central nervous system are damaged due to the apoptosis of oligodendrocytes.

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