Medical Cell Biology Commons^™

The Role Of Bip Nucleotide Exchange Factor Sil1 In Immunoglobulin Biosynthesis, Tyler Sanford

Theses and Dissertations (ETD)

BiP is an essential endoplasmic reticulum resident molecular chaperone of the HSP70 family that binds exposed hydrophobic regions of unfolded proteins. Substrates bound by BiP are protected from dangerous non-specific interaction with other unfolded proteins via their aggregation prone exposed hydrophobic regions, which are normally buried in the native state, and act as BiP binding targets. For these substrates to mature into the native state, BiP must be released. Like all HSP70 family members, cycles of BiP binding and release are nucleotide dependent and facilitated by two genres of cochaperones, HSP40s, and nucleotide exchange factors (NEFs). HSP40s function in stimulating …

Cns Penetration Of Tyrosine Kinase Inhibitors In Mouse Models, Mohamed Elmeliegy

Theses and Dissertations (ETD)

For the past three decades, advances in the treatment of central nervous system (CNS) tumors such as malignant glioma have only been modest. One particular challenge facing treatment of brain tumors is the delivery of therapeutically effective concentrations of anti-cancer agents to the target site in the brain. The sanctuary of the brain is protected by several barrier systems such as the blood-brain barrier (BBB) and the blood-cerebrospinal fluid barrier (BCSFB). These barriers restrict the passage of anti-cancer drugs into the brain via several protective mechanisms.

In the present study, we used cerebral microdialysis sampling, a technique for sampling unbound …

Contribution Of The Unfolded Protein Response To Vegf Expression, Ethel Rose Pereira

Theses and Dissertations (ETD)

Tumor cells experience a limiting microenvironment due to inadequate vascularization that can affect the normal functioning of intracellular organelles. In the case of the endoplasmic reticulum, the limiting environment is further exacerbated by the high metabolic demands of the tumor cells, which together interfere with the proper maturation of nascent proteins synthesized there. The resultant accumulation of unfolded proteins activates a signal transduction pathway known as the Unfolded Protein Response, which serves primarily to protect the cell during stress and helps restore homeostasis to this organelle. As tumors expand resulting in regions that are a greater distance from functional blood …

Beta-2-Adrenergic Receptor Regulates Insulin Signaling To Reduce Cell Death In Müller Cells, Robert Jason Walker

Theses and Dissertations (ETD)

No abstract provided.

Characterization Of The Key Mouse Cochlear Developmental Genes For Auditory Hair Cell Regeneration, Zhiyong Liu

Theses and Dissertations (ETD)

Mammalian inner ear cochlear auditory hair cells (HCs) and adjacent supporting cells (SCs) are believed to derive from the same progenitors during development. However, unlike SCs of nonmammalian vertebrates, mammalian cochlear SCs cannot be converted into functional hair cells (HCs) after damage, thus leading to permanent deafness. To entitle mammals with the ability to restore hearing capacity after HC damage, we first achieved proliferation of SCs by acute ablation of p27 or Sox2. Secondly, we overactivated Notch1 signaling in the mouse inner ear at different developmental stages, and found that the ability of Notch signaling in generating new HCs declines …

The Biochemical Pathway Leading To Lpa Generation Upon Blood Coagulation, Alyssa Lynn Jefferson Bolen

Theses and Dissertations (ETD)

Platelet activation initiates an upsurge in 18:2 and 20:4 lysophosphatidic acid (LPA) production. The biochemical pathway responsible for LPA production during blood clotting is not fully understood. We have purified a phospholipase A₁ (PLA₁) from thrombin-activated human platelets using sequential chromatographic steps followed by fluorophosphonate‑biotin affinity labeling and proteomics. We identified acyl‑protein thioesterase 1 (aka. lysophospholipase A1, accession code O75608) as a novel PLA₁. Addition of this recombinant PLA₁ significantly increased the production of sn‑2‑esterified polyunsaturated LPCs and the corresponding LPAs in plasma. We next examined the regioisomeric preference of lysophospholipase …

Insights Into P53-Dependent Apoptotic Signaling And Cell Fate Vis-A-Vis Functional Cooperation Among Bcl-Xl, Cytoplasmic P53, And Puma, John C. Fisher

Theses and Dissertations (ETD)

Following DNA damage, nuclear p53 induces the expression of PUMA (p53 upregulated modulator of apoptosis), a BH3‑only protein that binds and inhibits the anti‑apoptotic BCL‑2 repertoire, including BCL‑xL. Structural investigations of PUMA and the BCL‑xL×PUMA BH3 domain complex by X‑ray crystallography and nuclear magnetic resonance (NMR) spectroscopy reveal a novel, PUMA‑induced, domain‑swapped dimerization of BCL‑xL that requires a π‑stacking interaction between PUMA W71 and BCL‑xL H113. PUMA is an intrinsically disordered protein, but upon interaction with BCL‑xL, PUMA W71 and the PUMA BH3 domain residues fold into an alpha helix and subtly remodel BCL‑xL to trigger its dimerization. Wild type …

Novel Insights Into Ubiquitin-Like Protein E1-E2 Interactions, Asad Taherbhoy

Theses and Dissertations (ETD)

Posttranslational modification of macromolecules by ubiquitin-like proteins (UBLs) such as ubiquitin, Sumo and NEDD8 regulate a vast array of processes in the cell. Transfer of UBLs to their target generally occurs by a series of molecular handoffs down an E1‑E2‑E3 cascade. We are interested in understanding how E1‑E2 pairs interact and mediate UBL transfer. To this effect, we studied two E1‑E2 pairs: the Sumo pathway (Sumo utilizes a canonical E1 and E2) and the Atg8 pathway (Atg8 is a UBL involved in autophagy that utilizes a non-canonical E1‑E2 pair).

Sumo conjugation is initiated by the heterodimeric Aos1‑Uba2 E1 enzyme (in …

Role Of Extracellular Signal-Regulated Kinase (Erk) In Regulation Of Intestinal Epithelial Tight Junctions, Sudhir Aggarwal

Theses and Dissertations (ETD)

Evidence indicates that MAP kinase (ERK1/2) is involved in regulation of epithelial tight junctions. There are different opinions expressed by investigators as to whether ERK disrupts the junctions or protects them. ERK has also been demonstrated to mediate the EGF-caused protection of the intestinal epithelial tight junctions (TJ) from hydrogen peroxide. Studies using pharmacological inhibitors have shown that EGF increases Thr-phosphorylation of occludin by a MAP kinase-dependent mechanism. This study aimed at looking at the role of ERK in regulation of tight junctions using pharmacological and molecular techniques.

Hypothesis: ERK protects tight junctions in differentiated Caco-2 cells, while it is …

D2r Dopamine Receptor Mediates Changes In Dual Specificity Phosphatase Expression In A Small Cell Lung Cancer Cell Line, Scott Lemar Lattimer

Theses and Dissertations (ETD)

Bromocriptine, a D2 dopamine receptor (D2R) agonist, is used clinically as a treatment for pituitary tumors of a lactotroph origin. Many questions remain unanswered about the mechanism of this effect. The antiproliferative effect has not been demonstrated in DMS 53 cell line, a Small Cell Lung Cancer (SCLC). In this thesis, we have shown that treatment with NPA (N‑propylnorapomorphine), a dopamine receptor agonist inhibits ERK phosphorylation and proliferation in DMS 53 cells. NPA treatment causes significant increases in DUSP‑1 (MKP‑1), DUSP‑4 (MKP‑2) and DUSP5 mRNA. NPA treatment also correlates with increases in DUSP5 (hVHR3) protein visualized using Western Blot. These …

Cd151 Reinforces Vascular Stability By Balancing Endothelial Cell Adhesion And Cytoskeletal Tension, Feng Zhang

Theses and Dissertations (ETD)

Tetraspanin CD151 is highly expressed in endothelial cells and regulates pathological angiogenesis. However, the mechanism by which CD151 promotes vascular morphogenesis and whether CD151 engages other vascular functions are unclear. We observed that CD151 is required for the maintenance of endothelial capillary-like structures formed in vitro and the integrity of lung endothelial cell-cell contacts in vivo. As a master regulator of endothelial cell-matrix and cell-cell adhesions, CD151 is needed for the optimal functions of various cell adhesion proteins such as integrin, cadherin, and CD44. The loss of CD151 elevates the cellular intrinsic contraction by upregulating RhoA signaling and downregulating of …

T-Cell Receptor Cdr3 Sequence But Not Recognition Characteristics Distinguish Autoreactive Effector And Foxp3+ Regulatory T-Cells, Xin Liu

Theses and Dissertations (ETD)

Regulatory T-cells (Treg) play an important role in maintaining immune tolerance to self-antigens and in suppressing excessive immune responses in the host. The source, specificity, and plasticity of the forkhead box transcription factor 3 (Foxp3⁺) Treg and conventional T (Tconv) cell populations active at sites of autoimmune pathology are not well characterized. To evaluate this, we combined global repertoire analyses and functional assessments of isolated T-cell receptors (TCR) from TCRa retrogenic mice with autoimmune encephalomyelitis (EAE). Treg and Tconv cell TCR repertoires were distinct, and autoantigen-specific Treg and Tconv cells were enriched in diseased tissue. Autoantigen sensitivity and …

Ns1 Of H5n1 Interacts With Sap-97 In A Pdz-Dependent Manner To Disrupt Epithelial Barrier Integrity, Veronica Garcia Conoley

Theses and Dissertations (ETD)

The ability of influenza A virus to cause global pandemics has been a great concern throughout history and poses a serious health risk worldwide. Pandemic outbreaks throughout history, such as the Spanish flu of 1918, have claimed the lives of millions of people worldwide. The current outbreak of avian influenza (H5N1) that began in 1997 is still claiming lives, and therefore efforts to understand the mechanisms of pathogenesis in this highly virulent virus are of the utmost importance. According to the World Health Organization, there have been 447 reported H5N1 human cases, resulting in 263 deaths. The pathology of H5N1 …

Structural Characterization Of The C-Terminus Of The Cochlear Motor Protein Prestin: Intrinsic Disorder Linked To Voltage Sensor Function, Michael S. Podgorski

Theses and Dissertations (ETD)

The sensitivity of mammalian hearing relies upon the ability to amplify sound. Outer hair cells (OHCs) in the cochlea have motile properties that support this function. The motor protein called prestin resides in the lateral wall of the OHCs. Prestin undergoes voltage-dependent conformational changes, which correlates to the movement of charge through the membrane or non-linear capacitance (NLC). This property underlies OHC electromotility. A mechanistic understanding of prestin’s function remains unknown. Previous research has tied prestin’s C-terminus (residues 499-799) to the voltage-dependent events that occur in the membrane. The folding and biochemical properties of prestin’s C-terminus were characterized. This information …

Identification Of The Downstream Effector Genes Involved In Hoxb4-Induced Expansion Of Hematopoietic Progenitor Cells, Jie Jiang

Theses and Dissertations (ETD)

Overexpression of HOXB4, a member of Homeobox transcription factor family, promotes expansion of hematopoietic stem and progenitor cells bothin vivo and in vitro. However, the molecular mechanisms underlying this effect are not well understood. In order to identify direct target genes of HOXB4 in primary murine hematopoietice progenitor cells, we induced HOXB4 function in lineage-negative, murine bone marrow cells, using a tamoxifen-inducibleHOXB4-ER^T2fusion protein. Seventy seven genes with differentially changed expression in early response to HOXB4 have been identified as candidate target genes. Among them, we show that Hemogen (Hemgn), encoding a nuclear protein specifically …

Regulation Of Pyruvate Dehydrogenase Kinase 4 By Thyroid Hormone / Role Of Peroxisome Proliferator Activated Receptor Gamma Coactivator-1 Alpha And Ccaat Enhancer Binding Protein, Ramy Naguib Attia

Theses and Dissertations (ETD)

Pyruvate dehydrogenase kinase 4 (PDK4) regulates pyruvate oxidation through the phosphorylation and inhibition of the pyruvate dehydrogenase complex (PDC). The PDC catalyzes the conversion of pyruvate to acetyl-CoA and it is an important control point in glucose and pyruvate metabolism. Previous studies had reported that PDK4 gene expression is induced by thyroid hormone (T3). These studies did not investigate the mechanisms by which T3 regulated PDK4 gene expression. I have examined the role of the thyroid hormone receptor (TR), transcriptional coactivators especially the peroxisome proliferator activated receptor gamma coactivator-1 (PGC-1α) and other transcription factors that act as accessory factors in …

Contribution Of Organic Cation Transporter 2 (Oct2) To Cisplatin-Induced Nephrotoxicity, Kelly K. Filipski

Theses and Dissertations (ETD)

Cisplatin is the most widely used anticancer agent; however, the cellular pharmacokinetics are poorly understood. Cisplatin is predominantly eliminated through the urine via active secretion and is associated with nephrotoxicity. Currently, prehydration therapy is employed to prevent toxic renal side effects; however it has not been completely ameliorated. The studies described herein aim to determine the mechanism in which cisplatin enters the kidney cell from the blood and how it is subsequently secreted into the urine. Organic cation transporter 2 (OCT2) and ABCC2 are highly expressed in the kidney on the basolateral and apical membrane, respectively. We determined the contribution …

Studying The Specificity Of Hpxr Antagonists Using A Panel Of Cell-Based Assays, Fang Lei

Theses and Dissertations (ETD)

The pregnane X receptor (PXR or SXR; NR1I2) is a member of the nuclear receptor superfamily. It activates the transcription of a large network of genes including cytochrome P450 (CYP) and Mdr1 which play critical roles in chemicals metabolism and transportation. Induction of CYPs contributes to adverse drug-drug interactions. Non-toxic, PXR-specific antagonists will be valuable in attenuating the adverse drug-drug interaction which is the cause of many treatment failures in clinic. However, few hPXR antagonists were reported particularly the specific ones. In this thesis a reporter gene assay was used to study the specificity of hPXR antagonists from a panel …

Insights Into Btb-Cul3 Ubiquitin Ligases From The Structures Of Spop-Substrate Complexes, Min Zhuang

Theses and Dissertations (ETD)

Cullin-Ring ubiquitin ligases (CRLs) are E3 complexes that specifically recognize substrates through substrate adaptors. In the largest CRL subfamily, Cul3 binds a BTB domain, and a protein-interaction domain such as MATH recruits substrates for ubiquitination. Here we present biochemical and structural analyses of the MATH and BTB domain containing protein, SPOP, which regulates diverse signaling pathways. First, we identified a conserved SPOP Binding Consensus (SBC) motif in the transcriptional regulator Ci, the protein phosphatase Puc, and the chromatin component MacroH2A. The SBC motif specifically binds the MATH domain of SPOP, and is required for Puc ubiquitination in vitro and in …

Structural And Kinetics Studies Of The Enzyme Dihydropteroate Synthase And The Implications For Antibiotic Resistance, Katherine A. Ayers

Theses and Dissertations (ETD)

The goal of this study is to develop small molecule inhibitors of DHPS for the treatment of a variety of infectious diseases. According to the World Health Organization (WHO), infectious diseases kill more than 13 million people worldwide every year making it the second leading cause of death behind cardiovascular disease. The sulfonamide class of drugs has been in use since the 1930’s to treat many infectious agents and act by targeting the enzyme dihydropteroate synthase (DHPS) of the prokaryotic and lower eukaryotic folate pathway.

DHPS is an ideal drug target because humans do not synthesize folate de novo and …

Regulation Of The Human Parainfluenza Virus (Hpiv3) Fusion Protein, Amanda Ruth Chapman

Theses and Dissertations (ETD)

Paramyxoviruses include a number of important human pathogens, including measles virus, mumps virus, and the human parainfluenza viruses (hPIV) 1-4, as well as several animal pathogens, such as Sendai virus, Nipah virus and Hendra virus. The creation of effective drugs and vaccines against this family of viruses would play an important role in decreasing the prevalence of these viruses and contributing to the health of both humans and animals worldwide. The purpose of this work was to determine how the fusion (F) protein is regulated with a focus on the heptad repeat B (HRB) region of the F protein located …

The Role Of Fgf Signaling In Retinal Development, Abbie A. Hartge

Theses and Dissertations (ETD)

The development of the retina is a precise balance between intrinsic competence and extrinsic factors. This interplay is known to regulate the generation of cell types in the developing retina and similar mechanisms have been found in other regions of the CNS. In the developing retina, FGFs are a large family of secreted polypeptide growth factors. Fgf15 is the major Fgf expressed during retinal development in mice. Fgf15 is an example of an FGF that has been shown to control proliferation, cell fate specification, differentiation and migration during development. In this thesis I used analysis of specific genes throughout retinal …

The Unfolded Protein Response Increases Production Of Pro-Angiogenic Factors By Tumor Cell Lines, Nan Liao

Theses and Dissertations (ETD)

The rapid growth and proliferation of tumor cells will be limited at a stage when they encounter inadequate levels of oxygen and nutrient supply within the poorly vascularized tumor mass. These severe conditions negatively affect the proper folding of nascent proteins in the endoplasmic reticulum (ER) and lead to accumulation of unfolded protein within ER which is referred to as ER stress. Consequently, it will trigger the unfolded protein response (UPR) signal pathway through ER membrane stress sensor proteins including activating transcription factor 6 (ATF6), inositol-requiring 1 (IRE1) and PKR-like ER localized kinase (PERK). The UPR is largely a cytoprotective …

Tetraspanin Kai1/Cd82 Inhibits Cell Migration-Related Cellular Events Via Reorganizing Actin Network, Wei Liu

Theses and Dissertations (ETD)

To determine how tetraspanin KAI1/CD82, a tumor metastasis suppressor, inhibits cell migration, we assessed which motility-related cellular events are altered by KAI1/CD82 and how KAI1/CD82 regulates these events. We found that KAI1/CD82-overexpressing cancer cells exhibit various morphologies but typically display elongated cellular extensions and a lack of lamellipodia. Live imaging demonstrated that the formation of lamellipodia and retraction of extensions were deficient upon KAI1/CD82 overexpression.

The deficiency in developing motility-related cellular events was accompanied by defects in actin cortical network and stress fiber formations. Notably, actin polymerization was attenuated by KAI1/CD82. Although Rac1 activity was diminished upon KAI1/CD82 expression, Rac1 …

Molecular Mechanism Of Tetraspanin Cd9 Mediated Cell Motility, Jayaprakash Kotha

Theses and Dissertations (ETD)

CD9, a member of the tetraspanin superfamily of proteins participates in the regulation of cell adhesive functions such as cell migration. The mechanisms underlying CD9 mediated cell migration are not known. In the current study, we investigated the molecular basis for the CD9 promoted cell migration. Our findings show that the phosphatidylinositol-3 kinase (PI-3K) inhibitors, wortamannin and LY294002 inhibited CD9 promoted cell motility in Chinese hamster ovary (CHO) cells. In contrast, inhibitors targeting protein kinase C or mitogen-activated protein kinase had no effect on CD9 driven CHO cell motility. Furthermore, inhibition of PI-3K activity in CHO cells by dominant/negative PI-3K …

Tyrosine Phosphorylation Of Villin: Effects On Actin Dynamics, Cell Morphology And Cell Migration, Alok Tomar

Theses and Dissertations (ETD)

Cell migration is a key aspect of many normal and abnormal biological processes, including embryonic development, defense against infections, wound healing, and tumor cell metastasis. In this study we demonstrate that an epithelial cell actin-binding protein, villin, plays a crucial role in the process of cell migration. Overexpression of villin in doxycyline-regulated HeLa Tet-off and MDCK Tet-off cells enhanced cell migration. We further demonstrate that tyrosine phosphorylation of villin by c-src is required for villin-induced cell migration. Previously, we identified four tyrosine phosphorylation sites in the amino-terminal domain of villin. I further identified six new sites in the carboxylterminal region …

Characterizing Erythrocyte Motions In Flowing Blood, Markos Leggas

Theses and Dissertations (ETD)

Characterizing the probabilistic motions of cells is a prerequisite for the development of a general model of transport and surface deposition of white cells and platelets (WBC/P). These phenomena differ greatly when red blood cells (RBC) are present at normal levels, but follow convective diffusion in dilute suspensions. A critical need is to understand and characterize dispersion and diffusion as they apply to red cells in suspension flow. The dispersive motions of
0.5-micrometer beads and fluorescently labeled human RBC flowing in dilute (0.003%) and concentrated (25%) RBC suspensions, respectively, were characterized using fluorescence videomicroscopy methods, and times for individual tracer …