PhD, University of Cincinnati, 2022, Medicine: Toxicology (Environmental Health)

This dissertation focused on the role of the Stathmin (STMN1) oncoprotein in regulating epithelial mesenchyme transition (EMT). EMT is implicated in cancer progression and understanding the mechanisms of EMT is necessary in developing approaches for preventing or treating metastasis. STMN1 levels and STMN1 serine 25 (S25) phosphorylation are upregulated in many cancers, correlating with cancer progression and poor patient survival; yet the role(s) of STMN1 phosphorylation in driving metastasis remains unclear. As p38/mitogen-activated protein kinase (MAPK) signaling up-regulates metastasis, and p38 phosphorylates STMN1 S25, we hypothesized that p38-mediated phosphorylation of S25 promoted EMT. Utilizing the prostate cancer (PCa) DU-145 cell line, treatment with anisomycin induced p38 and S25 phosphorylation which was inhibited by the p38 inhibitor SB203580 (SB), suggesting S25 was a target of p38 signaling. Unexpectedly, both anisomycin and AEBSF, and the p38 inhibitor SB, inhibited DU-145 cell migration. Consequently, we were unable to address our hypothesis with these chemicals. Therefore, we utilized hepatocyte growth factor (HGF) to determine whether HGF-induced p38 signaling regulated STMN1 S25 phosphorylation and promoted EMT. We provide the first evidence that treatment with HGF promotes STMN1 S25 phosphorylation in PCa cells. Furthermore, both extracellular regulated kinase (ERK) and p38 were activated by HGF and contributed to S25 phosphorylation. With HGF treatment, inhibition of ERK alone reduced pS25, while inhibition of both ERK and p38 abolished pS25, suggesting these kinases converge to phosphorylate STMN1 S25. HGF-treated DU-145 cells also exhibited increased migration and invasion and presented an EMT phenotype in vitro. A novel finding showed HGF-mediated EMT involved both ERK and p38 pathways, where p38 promoted cell migration while ERK promoted cytoskeletal rearrangements and loss of cell-cell junctions. We also demonstrated that cotreatment of H (open full item for complete abstract)

Committee: Susan Kasper Ph.D. (Committee Member); Ying Xia Ph.D. (Committee Member); Saulius Sumanas Ph.D. (Committee Member); Katherine Burns Ph.D. (Committee Member) Subjects: Organismal Biology

PhD, University of Cincinnati, 2021, Medicine: Molecular Genetics, Biochemistry, and Microbiology

The transforming growth factor beta (TGFß) family consists of over 30 dimeric ligands that play distinct roles throughout biology, from development to homeostasis. These processes include wound-healing, reproductive health, adipogenesis, muscle and cardiac maintenance, and bone growth, among others. Three classes of TGFß have emerged: the TGFßs, the activins and the bone morphogenetic proteins (BMPs), separated based on sequence identity, receptor binding repertoires and biological functions. To signal, each ligand forms a hexameric complex with four receptors: two of the type II variant, of which there are five available, and 2 of the type I variant, of which there are seven available. The ratio of ligands to signaling receptors creates a receptor utilization bottleneck, where key differences in each ligand/receptor generate specificity and dictate interaction partners. In addition, different mechanisms of receptor assembly have emerged for the TGFß and BMP classes, where the positional assembly of ligand/receptor complex differs fundamentally. However, prior to our work, little structural information existed characterizing activin/receptor interactions, particularly for the type I receptor. Here, we present both biochemical and structural studies extending our understanding of the activin class. We have solved 4 unique structures within the activin class: 1) the structure of apo-GDF11, 2) the structure of GDF11 in complex with ActRIIB and Alk5, 3) the structure of GDF11 in complex with an ActRIIB-Alk4 fusion, and 4) the structure of ActA in complex with the ActRIIB-Alk4 fusion. Through this work, we presented the first structure of an activin class member bound by both the cognate type II and type I receptors, which bind independently. A composite interface is built from surfaces on both ligand monomers, where the majority of receptor ß4ß5 loop is engaged and a conserved knob-in-hole moiety is used to anchor the binding. Furthermore, through these studies, we have (open full item for complete abstract)

Committee: Thomas Thompson Ph.D. (Committee Chair); Andrew Herr Ph.D. (Committee Member); Rhett Kovall Ph.D. (Committee Member); John Monaco Ph.D. (Committee Member); Aaron Zorn Ph.D. (Committee Member) Subjects: Biochemistry

Master of Science, The Ohio State University, 2017, Comparative and Veterinary Medicine

Laminitis is a debilitating, often fatal disease of the equine foot which, specifically, refers to the loss of integrity of the digital lamellae, commonly termed the suspensory apparatus of the distal phalanx. Causes of laminitis can be separated into three broad categories: sepsis related laminitis, equine metabolic syndrome associated laminitis, and supporting limb laminitis. Although the anamneses of patients afflicted by these disparate types of laminitis can be varied, many similarities can be drawn between the ultrastructural changes seen in the lamellar tissue of the affected animals: namely, stretching of the lamellar basal and parabasal epithelial cells, loss of hemidesmosomal integrity in the basal epithelial cells, and lengthening of the secondary epidermal lamellae. Recent investigations into the pathogenesis of sepsis related laminitis have implicated inflammatory signaling as a causative agent for the lamellar damage seen in acute sepsis related laminitis, and, more importantly, these investigations have discovered a decrease in lamellar inflammatory signaling with the institution of therapeutic digital hypothermia. Therapeutic digital hypothermia is the only therapy demonstrated to not only treat but prevent the lamellar damage documented to occur in sepsis related laminitis. Therefore, the aims of the first two investigations outlined in this thesis were to characterize the effect of digital hypothermia instituted after the onset of lameness on gene expression of inflammatory mediators in the oligofructose model of sepsis related laminitis. Interestingly, both experiments 1 and 2 demonstrated that, although the histopathology scores demonstrated profound cryoprotection of the lamellar tissue treated with digital hypothermia, this protection did not correlate with a decrease in lamellar inflammatory signaling. These data indicated that the increase in lamellar inflammation long noted to be present in acute sepsis related laminitis may not be (open full item for complete abstract)

Committee: James Belknap (Advisor) Subjects: Veterinary Services