published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

Tsang, Chi Keung. / "November 2011." / Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 103-116). / Abstracts in English and Chinese. / Abstract --- p.I / 摘要 --- p.III / Acknowledgement --- p.IV / Table of content --- p.V / List of Figures --- p.VIII / List of Tables --- p.XI / Abbreviations --- p.XII / Chapter Chapter 1: --- INTRODUCTION --- p.1 / Chapter 1.1. --- Hepatocellular carcinoma --- p.2 / Chapter 1.1.1. --- Etiological factors --- p.11 / Chapter 1.1.1.1. --- Chronic Hepatitis and Liver Cirrhosis --- p.13 / Chapter 1.1.1.2. --- HBV --- p.13 / Chapter 1.1.1.3. --- HCV --- p.17 / Chapter 1.1.1.4. --- Male gender --- p.20 / Chapter 1.1.1.5. --- Aflatoxin B1 exposure --- p.21 / Chapter 1.2. --- Genomic abnormalities in HCC --- p.23 / Chapter 1.3. --- GEF-H1 --- p.24 / Chapter 1.4. --- RhoA --- p.26 / Chapter 1.5. --- Epithelial-Mesenchymal Transition (EMT) --- p.29 / Chapter 1.6. --- Aims of Thesis --- p.31 / Chapter Chapter 2: --- MATERIALS AND METHODS --- p.32 / Chapter 2.1. --- Materials --- p.33 / Chapter 2.1.1. --- Chemicals and Reagents --- p.33 / Chapter 2.1.2. --- Buffers --- p.35 / Chapter 2.1.3. --- Cell Culture --- p.37 / Chapter 2.1.4. --- Nucleic Acids --- p.38 / Chapter 2.1.5. --- Enzymes --- p.39 / Chapter 2.1.6. --- Equipments --- p.40 / Chapter 2.1.7. --- Kits --- p.41 / Chapter 2.1.8. --- Antibodies --- p.42 / Chapter 2.1.9. --- Software and Web Resources --- p.43 / Chapter 2.2. --- Fluorescence In Situ Hybridization (FISH) --- p.44 / Chapter 2.2.1. --- Probe Preparation --- p.44 / Chapter 2.2.1.1. --- Human Bacterial Artificial Chromosome (BAC) probe preparation --- p.44 / Chapter 2.2.1.2. --- Nick translation --- p.44 / Chapter 2.2.2. --- Hybridization --- p.45 / Chapter 2.3. --- Genomic DNA extraction --- p.47 / Chapter 2.4. --- Copy number analysis --- p.48 / Chapter 2.5. --- Exon Sequencing analysis --- p.49 / Chapter 2.5.1. --- PCR amplification of GEF-H1 exons --- p.49 / Chapter 2.5.2. --- Cycle sequencing --- p.49 / Chapter 2.6. --- Ectopic expression of GEF-H1 in immortalized hepatocyte cell line --- p.52 / Chapter 2.6.1. --- Construction of GEF-H1 expressing vector --- p.52 / Chapter 2.6.2. --- Sub-cloning --- p.52 / Chapter 2.6.3. --- Transfection and clonal selection --- p.53 / Chapter 2.7. --- Gene Expression Analysis by Quantitative RT-PCR --- p.55 / Chapter 2.7.1. --- Total RNA extraction --- p.55 / Chapter 2.7.2. --- qRT-PCR analysis for gene expression --- p.55 / Chapter 2.8. --- Western blot --- p.58 / Chapter 2.9. --- Functional Analysis --- p.60 / Chapter 2.9.1. --- Cell viability (MTT) assay --- p.60 / Chapter 2.9.2. --- Cell proliferation assays (BrdU-incorporation) --- p.60 / Chapter 2.9.3. --- Mitomycin C treatment --- p.61 / Chapter 2.9.4. --- Migration and Invasion assays --- p.63 / Chapter 2.9.5. --- Wound healing assay --- p.65 / Chapter 2.9.6. --- Transient knock-down of RhoA --- p.65 / Chapter 2. --- 10. Immuno-fluorescent imaging --- p.66 / Chapter 2. --- 11. In vivo tumorigenic study of GEF-H1 by subcutaneous injection --- p.68 / Chapter 2. --- 12. Statistical analysis --- p.69 / Chapter Chapter 3: --- RESULTS --- p.70 / Chapter 3.1. --- Verifying copy number gain of GEF-H1 in high GEF-H1 expressing HCC --- p.71 / Chapter 3.2. --- Verifying if there is any GEF-H1 exon point mutation in HCC --- p.75 / Chapter 3.3. --- Functional roles of GEF-H1 in HCC --- p.77 / Chapter 3.4. --- GEF-Hl-induced functions were RhoA independent --- p.83 / Chapter 3.5. --- GEF-H1 Induction of Epithelial-mesenchymal transition in HCC --- p.88 / Chapter 3.6. --- GEF-H1 induced tumorigenicity of MIHA cells --- p.95 / Chapter Chapter 4: --- DISCUSSIONS --- p.96 / Chapter 4.1. --- GEF-H1 in HCC and other cancers --- p.97 / Chapter 4.2. --- GEF-H1 promotes cell motility --- p.98 / Chapter 4.3. --- GEF-H1 induced tumorigenicity --- p.100 / Chapter Chapter 5: --- CONCLUSIONS AND PROPOSED FUTURE INVESTIGATIONS --- p.101 / Chapter Chapter 6: --- REFERENCES --- p.103

Indiana University-Purdue University Indianapolis (IUPUI) / Intrinsically disordered proteins (IDPs) are abundant in nature, being more prevalent in the proteomes of eukaryotes than those of bacteria or archaea. As introduced in Chapter I, these proteins, or portions of these proteins, lack stable equilibrium structures and instead have dynamic conformations that vary over time and population. Despite the lack of preformed structure, IDPs carry out many and varied molecular functions and participate in vital biological pathways. In particular, IDPs play important roles in cellular signaling that is, in part, enabled by the ability of IDPs to mediate molecular recognition. In Chapter II, the role of intrinsic disorder in molecular recognition is examined through two example IDPs: p53 and 14-3-3. The p53 protein uses intrinsically disordered regions at its N- and C-termini to interact with a large number of partners, often using the same residues. The 14-3-3 protein is a structured domain that uses the same binding site to recognize multiple intrinsically disordered partners. Examination of the structural details of these interactions highlights the importance of intrinsic disorder and induced fit in molecular recognition. More generally, many intrinsically disordered regions that mediate interactions share similar features that are identifiable from protein sequence. Chapter IV reviews several models of IDP mediated protein-protein interactions that use completely different parameterizations. Each model has its relative strengths in identifying novel interaction regions, and all suggest that IDP mediated interactions are common in nature. In addition to the biologic importance of IDPs, they are also practically important in the structural study of proteins. The presence of intrinsic disordered regions can inhibit crystallization and solution NMR studies of otherwise well-structured proteins. This problem is compounded in the context of high throughput structure determination. In Chapter III, the effect of IDPs on structure determination by X-ray crystallography is examined. It is found that protein crystals are intolerant of intrinsic disorder by examining existing crystal structures from the PDB. A retrospective analysis of Protein Structure Initiative data indicates that prediction of intrinsic disorder may be useful in the prioritization and improvement of targets for structure determination.

Indiana University-Purdue University Indianapolis (IUPUI) / Giant axonal neuropathy (GAN) is a rare genetic disease that causes progressive damage to the nervous system. Neurons in GAN patients develop an abnormal organization of cytoskeletal proteins called intermediate filaments (IFs), which normally provide strength and support for the overall cell structure. The irregular IF structure in GAN patient neurons leads to a progressive loss of motor skills in children and subsequent death in adolescence. GAN is caused by reduced levels of the gigaxonin (Giga) protein. Giga functions to control the degradation of other cellular proteins, and the loss of Giga in GAN cells results in significantly elevated levels of the galectin-1 (Gal-1) protein. Gal-1 stabilizes the active form of the Ras signaling protein, which functions as a molecular switch to regulate the phosphorylation and subsequent organization of IFs. The connection between these pathways led us to propose that Giga regulates IF phosphorylation and structure by modulating Ras signaling through the degradation of Gal-1. Using GAN patient cells, we demonstrated that restoring Giga reduced Gal-1 protein levels, decreased IF phosphorylation, and reestablished normal IF organization. Similar effects of reduced IF phosphorylation and improved IF structure were also obtained in GAN cells by directly decreasing the protein levels of either Gal-1, or downstream Ras signaling proteins. Taken together, these results demonstrate that the loss of Giga induces Gal-1 mediated activation of Ras signaling, thereby leading to the increased IF phosphorylation and abnormal IF structure observed in GAN cells. Identification of aberrant Ras signaling is significant because it is the first to specify a mechanism by which the loss of Giga leads to the development of GAN and provides targets for novel drug therapies for the treatment of this currently immedicable genetic disease.

Indiana University-Purdue University Indianapolis (IUPUI) / Sequestration at the aggresome and degradation through autophagy are two approaches by which a cell can counteract the toxic effect of misfolded proteins. Tuberous sclerosis (TS) and cancer cells can become dependent on autophagy for survival due to the high demand for protein synthesis, thus making protein clearance a potential therapeutic target. Because of its histone deacetylase (HDAC) inhibitory activity, we hypothesized that 4-phenylbutyrate (4-PBA) inhibits HDAC6 and aggresome formation to induce TS cell death. We found that 4-PBA treatment increases cell death and reduces bortezomib-induced aggresome formation. To link these results with HDAC inhibition we used two other HDAC inhibitors, trichostatin A (TSA) and tubastatin, and found that they also reduce bortezomib-induced protein aggregation. Because tubulin is a target of HDAC6, we next measured the effect of the HDAC inhibitors and 4-PBA treatment on tubulin acetylation. As expected, tubastatin increased tubulin acetylation but surprisingly TSA and 4-PBA did not. Because 4-PBA did not significantly inhibit HDAC6, we next hypothesized that 4-PBA was alternatively inducing autophagy and increasing aggresome clearance. Surprisingly, autophagy inhibition did not prevent the 4-PBA-induced reduction in protein aggregation. In conclusion, we found 4-PBA to induce cell death and reduce aggresome levels in TS cells, but we found no link between these phenomena. We next hypothesized that loss of the Ral guanine nucleotide exchange factor Rgl2 induces cell death via autophagy inhibition in pancreatic adenocarcinoma (PDAC) cells. KRas is mutationally activated in over 90% of PDACs and directly activates Rgl2. Rgl2 activates RalB, a known regulator of autophagy, and Rgl2 has been shown to promote PDAC cell survival. We first confirmed that loss of Rgl2 does increase cell death in PDAC cells. Initial experiments using doubly tagged fluorescent p62 and LC3 (autophagy markers) suggested that loss of Rgl2 inhibited autophagosome accumulation, but after developing a more sophisticated quantitation method we found loss of Rgl2 to have no effect. We also measured endogenous LC3 levels, and these experiments confirmed loss of Rgl2 to have no effect on autophagy levels. Therefore, loss of Rgl2 increases cell death in PDAC cells, but does not have a significant effect on autophagy.