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- All Subjects: Biochemistry
- Creators: School of Molecular Sciences
- Resource Type: Text
Description
Transient Receptor Potential (TRP) ion channels are a diverse family of nonselective, polymodal sensors in uni- and multicellular eukaryotes that are implicated in an assortment of biological contexts and human disease. The cold-activated TRP Melastatin-8 (TRPM8) channel, also recognized as the human body's primary cold sensor, is among the few TRP channels responsible for thermosensing. Despite sustained interest in the channel, the mechanisms underlying TRPM8 activation, modulation, and gating have proved challenging to study and remain poorly understood. In this thesis, I offer data collected on various expression, extraction, and purification conditions tested in E. Coli expression systems with the aim to optimize the generation of a structurally stable and functional human TRPM8 pore domain (S5 and S6) construct for application in structural biology studies. These studies, including the biophysical technique nuclear magnetic spectroscopy (NMR), among others, will be essential for elucidating the role of the TRPM8 pore domain in in regulating ligand binding, channel gating, ion selectively, and thermal sensitivity. Moreover, in the second half of this thesis, I discuss the ligation-independent megaprimer PCR of whole-plasmids (MEGAWHOP PCR) cloning technique, and how it was used to generate chimeras between TRPM8 and its nearest analog TRPM2. I review steps taken to optimize the efficiency of MEGAWHOP PCR and the implications and unique applications of this novel methodology for advancing recombinant DNA technology. I lastly present preliminary electrophysiological data on the chimeras, employed to isolate and study the functional contributions of each individual transmembrane helix (S1-S6) to TRPM8 menthol activation. These studies show the utility of the TRPM8\u2014TRPM2 chimeras for dissecting function of TRP channels. The average current traces analyzed thus far indicate that the S2 and S3 helices appear to play an important role in TRPM8 menthol modulation because the TRPM8[M2S2] and TRPM8[M2S3] chimeras significantly reduce channel conductance in the presence of menthol. The TRPM8[M2S4] chimera, oppositely, increases channel conductance, implying that the S4 helix in native TRPM8 may suppress menthol modulation. Overall, these findings show that there is promise in the techniques chosen to identify specific regions of TRPM8 crucial to menthol activation, though the methods chosen to study the TRPM8 pore independent from the whole channel may need to be reevaluated. Further experiments will be necessary to refine TRPM8 pore solubilization and purification before structural studies can proceed, and the electrophysiology traces observed for the chimeras will need to be further verified and evaluated for consistency and physiological significance.
ContributorsWaris, Maryam Siddika (Author) / Van Horn, Wade (Thesis director) / Redding, Kevin (Committee member) / School of Molecular Sciences (Contributor) / Department of English (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
The primary objective of this project is to further the knowledge about SCL26 family of anion transporters. The goals of the experiment were to find the lowest sulfate concentration where the yeast without Sulp1 and Sulp2 is able to grow, but it grows very slowly, and to find a higher sulfate concentration where the yeast grows quickly, with or without the sulfate transporters. The lowest sulfate concentration where the yeast without the sulfate transporters is able to grow was determined to be 2-4 mM, however, this range can likely be refined by more quantitative analytical methods. At a sulfate concentration of 20 mM sulfate or higher, the yeast is able to grow quickly without high-affinity sulfate transporters. The next step in the project is to re-introduce the Sulp1 and Sulp2 genes into the yeast, so that growth in low and high sulfate conditions can be compared with and without the Sulp1 and Sulp2 proteins. The long-term goals of the project are to bring experience with yeast to Dr. Nannenga’s structural discovery lab, to determine if yeast sulfate transporters respond in the same way to drug candidates as human sulfate transporters, and to determine the structure of the proteins using cryo-electron microscopy.
ContributorsCall, Nicolas I (Author) / Nannenga, Brent (Thesis director) / Wang, Xuan (Committee member) / School of Molecular Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2019-05
Description
The aims of this project are: (i) to identify structural and molecular changes in the brains of 3xTg-AD mice and (ii) to determine whether decreasing S6K1 protects the brain from these changes. To achieve our goals, we decided to remove one copy of the S6K1 gene in 3xTg-AD mice by breeding them with S6K1 knockout mice (S6K1+/-). In previous studies, we have seen that reducing S6K1 levels in 3xTg-AD mice improved spatial memory and synaptic plasticity which was associated with reduced A and tau pathology. Here, we used a multiparametric MRI to assess volumetric and blood flow changes in the brain of 20-month-old 3xTg-AD mice. We found that 3xTg-AD/S6K1+/- mice had higher blood flow and cortical volume compared to 3xTg-AD mice. However, we saw no significant differences between 3xTg-AD mice and NonTg mice. We further found A levels and plaque numbers were significantly lower in 3xTg-AD/S6K1+/- mice compared to 3xTg-AD mice. This reduction in plaques could account for the improvement in blood flow in 3xTg-AD/S6K1+/- mice. To try to understand the reason behind the increase in cortical volume in the 3xTg-AD/S6K1+/- when compared to the 3xTg-AD, we measured markers of synaptic density, PSD95, and synaptophysin. We found that PSD95 levels were not different between the four groups. However, synaptophysin levels were significantly lower in 3xTg-AD mice compared to NonTg levels and returned to baseline levels in 3xTg-AD mice lacking one copy of the S6K1 gene. This difference in synaptophysin could explain, at least in part, the difference in volume between the four groups analyzed. Overall, this represents the first evidence showing that reducing mTOR signaling improves blood flow and cortical volume in a mouse model of AD.
ContributorsShukla, Prakriti (Author) / Oddo, Salvatore (Thesis director) / Caccamo, Antonella (Committee member) / Jankowsky, Joanna (Committee member) / School of Molecular Sciences (Contributor) / School of Public Affairs (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
Neuroinflammation is mediated by activated microglia, the chief immune response of the central nervous system. Mitochondrial 18kDa translocator protein (TSPO) is upregulated in activated microglia and has been used in PET scans to analyze peripheral and central inflammation with TSPO radioligand [18F]DPA-714. To test the hypothesis that TSPO is involved in microglial mediation of inflammatory responses to Aβ and other Alzheimer’s pathological elements, TSPO expression was evaluated in relation to microglia specific markers (IBA1 and LN3 antibodies) and markers for AD pathology, Aβ (6E10 antibody) and hyperphosphorylated tau (AT8 antibody). To test that TSPO is involved in inflammatory pathways, HEK cells transfected with TSPO plasmids were assessed for oxidative stress in response to Alzheimer’s disease pathogenic agents, β Amyloid (Aβ), and Parkinson’s disease α-synuclein (α-syn).
Fluorescence microscopy of TSPO transfected HEK cell cultures labeled with Carboxy-H2DCFDA and treated with Beta Amyloid (Aβ) and α-synuclein (α-syn) resulted in DAPI fluorescing Human Embryonic Kidney (HEK) nuclei in blue and Green Fluorescent Protein (GFP) fluorescing reactive oxygen species (ROS) or oxidative stress in cell cytoplasm in green. Preliminary study suggests TSPO transfected cells may be used to test oxidative stress with disease pathological elements (Aβ and α-synuclein). In IHC, TSPO immunoreactivity was observed in IBA1 and LN3 marked microglia with varying degrees of expression. Beaded structures were also observed with TSPO immunoreactivities, possibly representing microglia processes. TSPO immunoreactivity was observed in and surrounding amyloid plaques and p-tau immunoreactive neurites. This demonstrates that TSPO is predominantly expressed in microglia and are closely associated with Alzheimer’s disease pathological elements, suggesting involvement of TSPO-expressing microglia in neurodegenerative processes.
Fluorescence microscopy of TSPO transfected HEK cell cultures labeled with Carboxy-H2DCFDA and treated with Beta Amyloid (Aβ) and α-synuclein (α-syn) resulted in DAPI fluorescing Human Embryonic Kidney (HEK) nuclei in blue and Green Fluorescent Protein (GFP) fluorescing reactive oxygen species (ROS) or oxidative stress in cell cytoplasm in green. Preliminary study suggests TSPO transfected cells may be used to test oxidative stress with disease pathological elements (Aβ and α-synuclein). In IHC, TSPO immunoreactivity was observed in IBA1 and LN3 marked microglia with varying degrees of expression. Beaded structures were also observed with TSPO immunoreactivities, possibly representing microglia processes. TSPO immunoreactivity was observed in and surrounding amyloid plaques and p-tau immunoreactive neurites. This demonstrates that TSPO is predominantly expressed in microglia and are closely associated with Alzheimer’s disease pathological elements, suggesting involvement of TSPO-expressing microglia in neurodegenerative processes.
ContributorsWu, Michael (Author) / Lue, Lih-Fen (Thesis director) / Washo-Krupps, Delon (Committee member) / School of Life Sciences (Contributor) / School of Molecular Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
A prominent aspect of Alzheimer’s disease (AD) is the presence of neuroinflammation is mediated by the activation of microglial cells, which are the immune cells in the central nervous system (CNS) that express an array of cytokines that may promote an inflammatory response. The main cytokines produced are: tumor necrosis factor-alpha (TNF-), interleukin-1β (IL-1β), and interleukin-6 (IL-6). The presence of these cytokines in the CNS may lead to neuronal death, to the production of toxic chemicals (such as nitric oxide), and to the generation of amyloid beta (a major pathological feature of AD). Previous studies have shown that modulation of the inflammatory response in the nervous system can potentially prevent and/or delay the onset of neurodegenerative diseases such as AD. Therefore, it is important to identify the process that induces CNS inflammation. For example, mitochondrial lysates have been found to produce an inflammatory response due to their ability to stimulate TNF-, Aβ, and APP mRNA [10]. Interestingly, extracellular mitochondria have been detected in the brain due to neurons degrading old mitochondria extracellularly. Therefore, we set out to study the effect of whole mitochondria isolated by differential centrifugation from human neuroblastoma cells (BE(2)-M17 cells) on the neuroinflammatory response in a human microglia model (THP-1 cells). Despite our best efforts, in the end it was unclear whether the mitochondrial fraction or other cellular components induced the inflammatory response we observed. Thus, further work with an improved mitochondrial isolation method should be carried out to address this issue.
ContributorsStokes, Laura Jean (Author) / DeCourt, Boris (Thesis director) / Sweazea, Karen (Committee member) / Gonzales, Rayna (Committee member) / School of Molecular Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
The devastating 2014 Ebola virus outbreak in Western Africa demonstrated the lack of therapeutic approaches available for the virus. Although monoclonal antibodies (mAb) and other molecules have been developed that bind the virus, no therapeutic has shown the efficacy needed for FDA approval. Here, a library of 50 peptide based ligands that bind the glycoprotein of the Zaire Ebola virus (GP) were developed. Using whole virus screening of vesicular stomatitis virus pseudotyped with GP, low affinity peptides were identified for ligand construction. In depth analysis showed that two of the peptide based molecules bound the Zaire GP with <100 nM KD. One of these two ligands was blocked by a known neutralizing mAb, 2G4, and showed cross-reactivity to the Sudan GP. This work presents ligands with promise for therapeutic applications across multiple variants of the Ebola virus.
ContributorsRabinowitz, Joshua Avraam (Author) / Diehnelt, Chris (Thesis director) / Johnston, Stephen (Committee member) / School of Molecular Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12
Description
The parameters of microwave-assisted acid hydrolysis (MAAH) and 1H NMR highly affect the quantitative analysis of protein hydrolysates. Microwave-induction source, NMR spectral resolution, and data analysis are key parameters in the nuclear magnetic resonance – amino acid analysis (NMR-AAA) workflow where errors accrue due to lack of an optimized protocol. Hen egg white lysozyme was hydrolyzed using an 800W domestic microwave oven for varying time points between 10-25 minutes, showing minimal protein hydrolysis after extended time periods. Studies on paramagnetic doping with varying amounts of gadolinium chloride for increased NMR resolution resulted in little T1 reduction in a majority of amino acids and resulted in significant line broadening in concentrations above 1µM. The use of the BAYESIL analysis tool with HOD suppressed 1H-NMR spectra resulted in misplaced template peaks and errors greater than 1% for 10 of 13 profiled amino acids with the highest error being 7.6% (Thr). Comparatively, Chenomx NMR Suite (v7.1) analysis resulted in errors of less than 1% for 9 of 13 profiled amino acids with a highest error value of 3.6% (Lys). Using the optimized protocol, hen egg white lysozyme C was identified at rank 1 with a score of 64 in a Gallus gallus species wide AACompIdent search. This technique reduces error associated with sample handling relative to previously used amino acid analysis (AAA) protocols and requires no derivatization or additional processing of the sample prior to analysis.
ContributorsJordan, Jacob Smith (Author) / Yarger, Jeffery (Thesis director) / Van Horn, Wade (Committee member) / School of Molecular Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
Integrin is a protein in cells that manage cell adhesion. They are crucial to the biochemical functions of cells. L 2 is one type of integrin. Its I domain is responsible for ligand binding. Scientists understand how Alpha L I domain binds Mg2+ at a pH of 7 but not in acidic environments. Knowing the specificity of integrin at a lower pH is important because when tissues become inflamed, they release acidic compounds. We have cloned, expressed, and purified L I-domain and using NMR analysis, we determined that wild type Alpha L I domain does not bind to Mg2+ at a pH of 5.
ContributorsALAM, RAHAT (Author) / Wang, Xu (Thesis director) / Podolnikova, Nataly (Committee member) / School of Molecular Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
Gle1 is an mRNP export mediator with major activity localized to the nuclear pore complex in eukaryotic cells. The protein's high preservation across vast phylogenetic distances allows us to approximate research on the properties of yeast Gle1 (yGle1) with those of human Gle1 (hGle1). Research at Vanderbilt University in 2016, which provides the research basis of this thesis, suggests that the coiled-coil domain of yGle1 is best crystallized in dicationic aqueous conditions of pH ~8.0 and 10\u201420% PEG 8000. Further exploration of crystallizable microconditions revealed a favorability toward lower pH and lower PEG concentration. Following the discovery of the protein's native crystallography conditions, a comprehensive meta-analysis of scientific literature on Gle1 was conducted on the association of Gle1 mutations with neuron disease.
ContributorsGaetano, Philip Pasquale (Author) / Foy, Joseph (Thesis director) / Dawson, T. Renee (Committee member) / School of Molecular Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12
Description
Predicting the binding sites of proteins has historically relied on the determination of protein structural data. However, the ability to utilize binding data obtained from a simple assay and computationally make the same predictions using only sequence information would be more efficient, both in time and resources. The purpose of this study was to evaluate the effectiveness of an algorithm developed to predict regions of high-binding on proteins as it applies to determining the regions of interaction between binding partners. This approach was applied to tumor necrosis factor alpha (TNFα), its receptor TNFR2, programmed cell death protein-1 (PD-1), and one of its ligand PD-L1. The algorithms applied accurately predicted the binding region between TNFα and TNFR2 in which the interacting residues are sequential on TNFα, however failed to predict discontinuous regions of binding as accurately. The interface of PD-1 and PD-L1 contained continuous residues interacting with each other, however this region was predicted to bind weaker than the regions on the external portions of the molecules. Limitations of this approach include use of a linear search window (resulting in inability to predict discontinuous binding residues), and the use of proteins with unnaturally exposed regions, in the case of PD-1 and PD-L1 (resulting in observed interactions which would not occur normally). However, this method was overall very effective in utilizing the available information to make accurate predictions. The use of the microarray to obtain binding information and a computer algorithm to analyze is a versatile tool capable of being adapted to refine accuracy.
ContributorsBrooks, Meilia Catherine (Author) / Woodbury, Neal (Thesis director) / Diehnelt, Chris (Committee member) / Ghirlanda, Giovanna (Committee member) / Department of Psychology (Contributor) / School of Molecular Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05