In response to extra-cellular cues, cells activate signal transduction pathways to elicit a biological response. Cell surface growth factor receptors such as the Met receptor tyrosine kinase (RTK) activate signals that result in cellular proliferation, survival, migration, as well as epithelial morphogenesis. In order for signal transduction to occur, docking proteins are recruited to the activated RTK, become phosphorylated on tyrosine residues, which then serve as docking sites for the recruitment of other signaling proteins. Docking proteins function to diversify the signal by assembling multi-protein complexes. The Gab1 docking protein is the most tyrosine phosphorylated protein upon Met receptor activation and is required for Met mediated signaling and biology. / Gab1 belongs to a family of docking proteins including the highly related Gab2 protein. Gab1 promotes signals for epithelial morphogenesis downstream of the Met receptor, however Gab2 is unable to do so. Insertion of the Gab1 Met binding Motif (MBM) which confers direct binding to the Met receptor, as well as membrane targeting of Gab2 is sufficient to switch the capacity of Gab2 to activate the morphogenic program, cell scatter and lamellipodia formation. This is achieved via activation of sustained signaling pathways, and redistribution of the Gab protein, and associated molecules to sites of lamellipodia formation at the peripheral edge of the cell. / Activation of the Met RTK, promotes the formation of dorsal ruffles on the apical surface of epithelial cells. The Met receptor, Gab1 and Gab1 associated molecules Shp2, Crk, and p8S subunit of PI3K, are localized to these structures, however only the Gab1erk complex is required to drive dorsal ruffle formation. Gab1 is required for Met induced dorsal ruffles as well as downstream the PDGF and EGF RTKs. These are a signaling micro-environment which results in enhanced receptor degradation. Inhibition or enhancement of Met mediated dorsal ruffle formation correlates with receptor stability. / Dorsal ruffle formation downstream of Met requires the enzymatic activity of PI3K and PLCgamma, both enzymes that metabolize PIP2, and form complexes with Gab1 downstream of Met. PLCgamma and the PIP3 lipid product of PI3K are co-localized with Gab1 in dorsal ruffles. Gab1 engages with elements of the cytoskeleton, actin and cortactin, providing a link between growth factor signaling and remodeling of the actin cytoskeleton. Gab1 is localized to membrane protrusions of the basal surface in organoid cultures and is required for actin protrusions of the basal surface of breast cancer cells.

Oligodendrocyte progenitors are highly sensitive to oxidative insults. Among the factors postulated to contribute to this susceptibility are high levels of intracellular iron and low antioxidant content. During ischemia, the neurotransmitter dopamine (DA) is released and may contribute to oxidative stress and oligodendrocyte injury in the hypomyelinating disorder, periventricular leucomalacia (PVL). In this thesis, I investigated the role of iron in DA-induced toxicity in primary cultures of oligodendrocyte progenitors, and assessed the contribution of the antioxidant defenses (glutathione (GSH), glutathione peroxidase (GPx) and superoxide dismutase (SOD)) and other survival factors (heat shock proteins and the protein kinase Akt) in determining the response of the cells to DA. / Addition of iron to cultures increased DA-induced expression of the stress protein heme oxygenase-1 (HO-1), and toxicity as assessed by mitochondrial activity, cellular release of lactate dehydrogenase, nuclear condensation and caspase-3 activation. In contrast, an iron chelator reduced these events. Furthermore, DA induced accumulation of superoxide, which was also reduced by the iron chelator. Surprisingly, a mimetic of the superoxide detoxifying enzyme, SOD potentiated DA toxicity, suggesting that generation of hydrogen peroxide via superoxide dismutation may be contributing to toxicity. Both a mimetic of the peroxide-scavenging enzyme, GPx and a GSH analog blocked DA-induced superoxide accumulation, HO-1 expression and caspase-3 activation. In addition, the GPx mimetic blocked caspase-3 activation induced by the combination of DA with iron. In contrast, an inhibitor of glutathione synthesis potentiated DA-induced HO-1 expression and cell death. / Finally, in further examining the cellular defense mechanisms, I found that various heat shock proteins increased in expression levels during oligodendroglial differentiation, however only heat shock protein-90 (HSP-90) was detected in oligodendrocyte progenitors. An HSP-90 inhibitor decreased activated Akt levels, induced caspase-3 activation, increased nuclear condensation, reduced oligodendrocyte progenitor viability, and potentiated DA-induced apoptosis. In addition, an Akt inhibitor alone exacerbated DA toxicity and in combination with the HSP-90 inhibitor caused synergistic potentiation of DA toxicity by enhancing caspase-3 activation. / In conclusion, elevated levels of iron, superoxide, deficient detoxification of peroxides by glutathione peroxidase and inadequate defense by glutathione contribute to the susceptibility of oligodendrocyte progenitors to DA-induced toxicity. On the other hand, HSP-90 alone or in concert with Akt play important roles in oligodendrocyte progenitors survival following an insult that produces oxidative stress.

The HPV E6-p53 interaction is well-understood, but not for all high-risk HPV types. In addition, HPV E6 p53-independent functions are gaining recognition for their importance in cellular transformation but require clarification. Thus, the aim of this study was two-fold: (1) to gain insight into the p53-E6 interaction for high-risk HPV-33 and, (2) to explore how high-risk HPV E6 proteins targets cellular MAGI-3 for degradation. / In vivo and in vitro results indicated that E6 from HPV types 18 and 33 interacted similarly with p53 although, variants of the HPV-33 E6 prototype demonstrated interesting disparities. Of note was HPV-33 E6 variant 2, which degraded p53 more efficiently than prototype HPV-33 E6 and HPV-18 E6. The E6 protein from HPV types 18 and 33 also potently degraded MAGI-3 via a different pathway than that used for p53. Specifically, proteasome inhibition did not interfere with MAGI-3 degradation and MAGI-3 was not ubiquitinated in the presence of the E6 protein. / Therefore, the results described herein enhance our understanding of high-risk HPV type 33 E6 and the E6-MAGI-3 interaction.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2007. / Härtill 5 uppsatser.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2007. / Härtill 4 uppsatser.

Thesis (Ph.D. in Immunology) -- University of Colorado at Denver and Health Sciences Center, 2006. / Typescript. Includes bibliographical references (leaves 131-146). Free to UCD Anschutz Medical Campus. Online version available via ProQuest Digital Dissertations;

Dissertation (Ph.D.)--University of South Florida, 2007. / Title from PDF of title page. Document formatted into pages; contains 104 pages. Includes vita. Includes bibliographical references.

Thesis (M.Sc.). / Written for the Dept. of Chemistry. Title from title page of PDF (viewed 2009/06/23). Includes bibliographical references.

Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (p. 68-76).

Thesis--University of Oklahoma. / Bibliography: leaves 71-78.