Thesis (Ph. D.)--Florida State University, 2004. / Advisor: Dr. Randolph Rill, Florida State University, College of Arts and Sciences, Dept. of Chemistry and Biochemistry. Title and description from dissertation home page (viewed Jan. 13,2005). Includes bibliographical references.

Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009. / Committee Chair: William Hunt; Committee Member: Alfred Merrill, Jr.; Committee Member: John Petros; Committee Member: Peter Hesketh; Committee Member: Robert Butera. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Thesis (Ph. D.)--Michigan State University. Chemistry, 2008. / Title from PDF t.p. (viewed on Aug. 17, 2009) Includes bibliographical references (p. 185-210). Also issued in print.

Thesis (M.S.)--Brigham Young University. Dept. of Chemistry and Biochemistry, 2008. / Includes bibliographical references (p. 93-97).

Project (M.S.)--Brigham Young University. Dept. of Statistics, 2006. / Includes bibliographical references (p. 69-72).

Thesis (M.S.)--State University of New York at Binghamton, Department of Biological Sciences, 2004. / Includes bibliographical references.

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 153-163).

Neurofibromatosis type 2 (NF2) is an autosomal dominant inherited condition that predisposes individuals to develop multiple nervous system tumours, primarily schwannoma, meningioma and ependymoma. NF2 is characterised by loss of the tumour suppressor protein Merlin, caused by bi-allelic mutations of the encoding gene NF2 or by loss of heterozygosity. These tumours can occur either sporadically or as part of the NF2 condition. The majority are slow growing and display benign features, but this benignancy renders them largely unresponsive to classic chemotherapeutic agents leaving surgery and radiosurgery as the only remaining treatment options. Depending on their location, NF2-related tumours can cause a number of side effects, including nausea, balance problems, and in some cases hearing and/or vision loss. Phosphorylation is a key regulatory mechanism leading to changes in cell signalling. By identifying phosphoproteins that are significantly activated in tumour cells, novel therapies can be developed aiming to specifically target the phosphorylated status of these proteins thus ‘switching off’ the signalling cascade. The objective of this study is to identify and validate common targets in both Merlin-deficient meningioma and schwannoma to eventually exploit in novel therapeutic approaches. Using phosphoprotein purification followed by mass spectrometry analysis, we identified Signal Transducer and Activator of Transcription 1 (STAT1), phosphorylated at Serine (S) 727 and Tyrosine (Y) 701, PDZ and LIM domain protein 2 (PDLIM2), Heat Shock 70kDa Protein 1A (HSPA1A) and Filamin B (FLNB) as potential common, novel therapeutic targets. We validated these candidates in human primary meningioma and schwannoma tumour cells using a variety of techniques. We also showed that specific 7 knockdown of STAT1 and PDLIM2 was related to a significant decrease in cellular proliferation. Additionally, we performed co-immunoprecipitation using PDLIM2 as the bait protein and identified STAT1, HSPA1A and FLNB as binding partners, suggesting a novel interaction network involving all of the potential targets identified in this study. We also identified activation of several pathways and/ or biological processes in both tumour types that warrant further investigation i.e. endocytosis in schwannoma and the proteasome in meningioma. In conclusion, with our approach we substantially increased the overall body of knowledge regarding the proteome and phosphoproteome of meningioma and schwannoma. We generated a comprehensive set of data that highlighted several potential therapeutic targets and dysregulated pathways which will be further investigated.

Pt(II) based anticancer drugs—cisplatin, carboplatin, and oxaliplatin—are widely used in the treatment of a variety of cancers. Unfortunately, the clinical efficacy of these drugs is currently hindered by the development of undesirable side effects and resistance during treatment. The molecular mechanisms underlying these effects are still unclear. For decades, research has focused on DNA as the main cellular target of Pt(II) compounds. However, there is increasing interest in proteins as alternative targets of Pt(II) and contributors to cytotoxic and resistance mechanisms of cisplatin. In this work, I utilize Pt(II) compounds that have been functionalized to participate in the azide-alkyne cycloaddition ‘click’ reaction to study protein targets of platinum reagents. First, I describe the use of an azide-modified Pt(II) compound to fluorescently label and isolate Pt(II)-bound bovine serum albumin in vitro. Additionally, we discover that Pt(II) compounds form monofunctional adducts on BSA that can crosslink to DNA oligonucleotides. I then use the click-functionalized Pt(II) compound, azidoplatin, to enrich for Pt(II)-bound proteins in Saccharomyces cerevisiae using a biotin-streptavidin pull-down. I identified 152 proteins that are significantly enriched in AzPt-treated samples by LC-MS/MS analysis. A subset of these proteins are involved in proteostasis and ER stress, which I confirm is induced in both AzPt- and cisplatin-treated yeast. Of interest was the identification of the ER protein folding chaperone protein disulfide isomerase (PDI), which I observe is inhibited by Pt(II) binding in vitro. Finally, I investigate PDI activity in human cancer cell lines HeLa and MDA-MB-468 following treatment with Pt(II) compounds. Extracts from platinum-treated MDA-MB-468 cells show significant PDI inhibition at low concentrations of Pt(II), and these cells appear to have constitutive activation of the unfolded protein response. PDI activity in extracts from platinum-treated HeLa cells is inhibited only at high concentrations of Pt(II), and HeLa cells do not show significant XBP1 mRNA splicing during Pt(II) treatment. Additionally, MDA-MB-468 cells are nearly three times as sensitive to Pt(II) compounds than HeLa cells. From these data, I hypothesize that basal ER stress increases sensitivity to PDI inhibition by Pt(II) binding and that this interaction enhances Pt(II)-induced cell death. / 10000-01-01

Reversible protein phosphorylation, the best studied post-translational modification, regulates most cellular processes, including signaling, migration, cell cycle progression, DNA damage repair, stress response and modulaton of the activities of metabolic enzymes. Therefore, it has emerged as a key therapeutic target in diseases in which these processes are deregulated. Unlike kinases, protein phosphatase 1 (PP1) is a promiscuous enzyme that gains its substrate specificity from a large group of “regulatory subunits” with which it associates to form a range of holoenzyme complexes targeted to specific subcellular localizations and substrates. Inhibition of a specific dephosphorylation event therefore relies on targeting the regulatory rather than the catalytic subunit. The present study uses GFP as a molecular reporter to assess the localization of PP1c and identify the underlying binding events that govern it via a combination of fluorescence imaging, cellular fractionation, affinity purification and quantitative mass spectrometry. While there is some overlap in their targeting and intracellular roles, the three PP1 isoforms show distinct localizations based on relative preferences for particular regulatory subunits. In this study we assembled a comprehensive map of isoform- and compartment- specific phosphatase complexes in three different cultured human cell lines, using the data to extrapolate, with confidence, the distribution of each PP1 isoform between a large pool of known/predicted and novel regulatory subunits. Network analysis also highlighted key multiprotein complexes to which PP1 is targeted by these regulatory subunits, and identified a novel regulatory subunit that links phosphatase activity to regulation of protein degradation. Our work confirmed that Mypt1, the regulatory subunit that targets PP1 activity to the myosin light chain, preferentially associates with the beta isoform of PP1c. We further demonstrated that they are in complex in both the cytoplasm and nucleus, and represent ~30% of the total PP1β holoenzyme complexes in both interaphase and mitotic cells. Further investigation of these complexes led to the discovery of Specc1 and Specc1L, which associate with Mypt1/PP1β via direct binding to Mypt1. Specc1/1L are microtubule binding proteins that can also associate with actin filaments, and we demonstrated that they mediate the distribution of Mypt1/PP1β complexes between these two cytoskeletal networks. Given that disruption of this balance has been implicated in disease states including cancer and hypertension, the Specc1/L family represents a novel therapeutic target for the regulation of Mypt1/PP1 activity. With PP1 now emerging as a promising therapeutic target and the first PP1-targeted therapeutic drug, Sephin 1, in clinical trials, a better understanding of PP1’s in vivo distribution between holoenzyme complexes is essential. Our work establishes an initial “snapshot” of this distribution against which changes can be assessed, as we demonstrated here by showing its re-distribution in mitotic cells. Dynamic redistributions during specific cell processes such as differentiation or in response to perturbations or disease states can be assessed in a similar fashion in future, facilitating both identification of the relevant complexes and the design of specific strategies to target them therapeutically.