Structural-Based Study of Intact Human Particulate Guanylyl Cyclase Receptor A (pGC-A) and Biophysical Characterization

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Description
Particulate Guanylyl Cyclase Receptor A (pGC-A) is an atrial natriuretic peptide receptor, which plays a vital role in controlling cardiovascular, renal, and endocrine functions. The extracellular domain of pGC-A interacts with natriuretic peptides and triggers the intracellular guanylyl cyclase domain

Particulate Guanylyl Cyclase Receptor A (pGC-A) is an atrial natriuretic peptide receptor, which plays a vital role in controlling cardiovascular, renal, and endocrine functions. The extracellular domain of pGC-A interacts with natriuretic peptides and triggers the intracellular guanylyl cyclase domain to convert GTP to cGMP. To effectively develop a method that can regulate pGC-A, structural information regarding its intact form is necessary. Currently, only the extracellular domain structure of rat pGC-A has been determined. However, structural data regarding the transmembrane domain, as well as functional intracellular domain regions, need to be elucidated.This dissertation presents detailed information regarding pGC-A expression and optimization in the baculovirus expression vector system, along with the first purification method for purifying functional intact human pGC-A. The first in vitro evidence of a purified intact human pGC-A tetramer was detected in detergent micellar solution. Intact pGC-A is currently proposed to function as a homodimer. Upon analyzing my findings and acknowledging that dimer formation is required for pGC-A functionality, I proposed the first tetramer complex model composed of two functional subunits (homodimer). Forming tetramer complexes on the cell membrane increases pGC-A binding efficiency and ligand sensitivity. Currently, a two-step mechanism has been proposed for ATP-dependent pGC-A signal transduction. Based on cGMP functional assay results, it can be suggested that the binding ligand also moderately activates pGC-A, and that ATP is not crucial for the activation of guanylyl cyclase. Instead, three modulators can regulate different activation levels in intact pGC-A. Crystallization of purified intact pGC-A was performed to determine its structure. During the crystallization condition screening process, I successfully selected seven promising initial crystallization conditions for intact human pGC-A crystallization. One selected condition led to the formation of excellent needle-shaped crystals. During the serial crystallography diffraction experiment, five diffraction patterns were detected. The highest diffraction resolution spot reached 3 Å. This work will allow the determination of the intact human pGC-A structure while also providing structural information on the protein signal transduction mechanism. Further structural knowledge may potentially lead to improved drug design. More precise mutation experiments could help verify the current pGC-A signal transduction and activation mechanism.
Date Created
2021
Agent

Structural and Biophysical Studies of Pathological Determinants in Cancer and Infectious Diseases

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Description
This work advances structural and biophysical studies of three proteins important in disease. First protein of interest is the Francisella tularensis outer membrane protein A (FopA), which is a virulence determinant of tularemia. This work describes recombinant expression in Escherichia

This work advances structural and biophysical studies of three proteins important in disease. First protein of interest is the Francisella tularensis outer membrane protein A (FopA), which is a virulence determinant of tularemia. This work describes recombinant expression in Escherichia coli and successful purification of membrane translocated FopA. The purified protein was dimeric as shown by native polyacrylamide gel electrophoresis and small angle X-ray scattering (SAXS) analysis, with an abundance of β-strands based on circular dichroism spectroscopy. SAXS data supports the presence of a pore. Furthermore, protein crystals of membrane translocated FopA were obtained with preliminary X-ray diffraction data. The identified crystallization condition provides the means towards FopA structure determination; a valuable tool for structure-based design of anti-tularemia therapeutics.

Next, the nonstructural protein μNS of avian reoviruses was investigated using in vivo crystallization and serial femtosecond X-ray crystallography. Avian reoviruses infect poultry flocks causing significant economic losses. μNS is crucial in viral factory formation facilitating viral replication within host cells. Thus, structure-based targeting of μNS has the potential to disrupt intracellular viral propagation. Towards this goal, crystals of EGFP-tagged μNS (EGFP-μNS (448-605)) were produced in insect cells. The crystals diffracted to 4.5 Å at X-ray free electron lasers using viscous jets as crystal delivery methods and initial electron density maps were obtained. The resolution reported here is the highest described to date for μNS, which lays the foundation towards its structure determination.

Finally, structural, and functional studies of human Threonine aspartase 1 (Taspase1) were performed. Taspase1 is overexpressed in many liquid and solid malignancies. In the present study, using strategic circular permutations and X-ray crystallography, structure of catalytically active Taspase1 was resolved. The structure reveals the conformation of a 50 residues long fragment preceding the active side residue (Thr234), which has not been structurally characterized previously. This fragment adopted a straight helical conformation in contrast to previous predictions. Functional studies revealed that the long helix is essential for proteolytic activity in addition to the active site nucleophilic residue (Thr234) mediated proteolysis. Together, these findings enable a new approach for designing anti-cancer drugs by targeting the long helical fragment.
Date Created
2020
Agent

The Simian Barrier Dilemma: Improving Gene Vaccines for the Future

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Description
Since its inception in the early 1990s, the concept of gene vaccines, particularly DNA vaccines, has enticed researchers across the board due to its simple design, flexible modification, and overall inexpensive cost of manufacturing. However, the past three decades have

Since its inception in the early 1990s, the concept of gene vaccines, particularly DNA vaccines, has enticed researchers across the board due to its simple design, flexible modification, and overall inexpensive cost of manufacturing. However, the past three decades have proven to be less fruitful than anticipated as scientists have yet to tackle the issue of inducing a strong enough response in humans and non-human primates to protect against foreign pathogens, an issue that has since been coined as the “simian barrier.” This appears to be a human/primate barrier as protective vaccines have been produced for other mammals. Despite millions of dollars in research along with some of the world’s brightest minds chipping in to resolve this, there has yet to be any truly viable solution to overcoming this barrier. With current research illustrating effective applications of RNA vaccines in humans, these studies may be uncovering the solution to the largely unsolved simian barrier dilemma. If vaccines using RNA, the transcribed version of DNA, are effective in humans, the problem may be inefficient transcription of the DNA. This may be attributable to a DNA promoter that has insufficient activity in primates. Additionally, with DNA vaccines being even cheaper and easier to manufacture than RNA vaccines, along with having no required cold chain for distribution, this concept remains more promising than RNA vaccines that are further along in clinical trials.
Date Created
2020-12
Agent

Cancer Type Specific FrAmeShifT (FAST) Vaccine

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Description
In this study, we demonstrate the effectiveness of a cancer type specific FrAmeShifT (FAST) vaccine. A murine breast cancer (mBC) FAST vaccine and a murine pancreatic cancer (mPC) FAST vaccine were tested in the 4T1 breast cancer syngeneic mouse model.

In this study, we demonstrate the effectiveness of a cancer type specific FrAmeShifT (FAST) vaccine. A murine breast cancer (mBC) FAST vaccine and a murine pancreatic cancer (mPC) FAST vaccine were tested in the 4T1 breast cancer syngeneic mouse model. The mBC FAST vaccine, both with and without check point inhibitors (CPI), significantly slowed tumor growth, reduced pulmonary metastasis and increased the cell-mediated immune response. In terms of tumor volumes, the mPC FAST vaccine was comparable to the untreated controls. However, a significant difference in tumor volume did emerge when the mPC vaccine was used with CPI. The collective data indicated that the immune checkpoint blockade therapy was only beneficial with suboptimal neoantigens. More importantly, the FAST vaccine, though requiring notably less resources, performed similarly to the personalized version of the frameshift breast cancer vaccine in the same mouse model. Furthermore, because the frameshift peptide (FSP) array provided a strong rationale for a focused vaccine, the FAST vaccine can theoretically be expanded and translated to any human cancer type. Overall, the FAST vaccine is a promising treatment that would provide the most benefit to patients while eliminating most of the challenges associated with current personal cancer vaccines.
Date Created
2019-05
Agent

Early Detection of Lung Cancer Using Low Dose Computed Tomography Screening, Thin Section Computed Tomography Screening, And Computer Aided Diagnosis

Description
The goal of this paper is to discuss the most efficient method to achieve early detection in lung cancers by reducing the occurrences of false-positive readings. Imaging techniques (computed tomography screenings) have greater impact than non-imaging techniques in

The goal of this paper is to discuss the most efficient method to achieve early detection in lung cancers by reducing the occurrences of false-positive readings. Imaging techniques (computed tomography screenings) have greater impact than non-imaging techniques in early detection for lung cancer. On the other hand, positron emission tomography and non-imaging techniques, such as liquid biopsy, are better at distinguishing cancer stages. Therefore, these techniques are not suitable early detection methods for lung cancer. Based on literature reviews, the combination that is most capable of early lung cancer detection incorporate low-dose computed tomography screenings, thin-section computed tomography screenings, and computer-aided diagnosis. Low-dose computed tomography screenings has lower radiation-associated risks compared to the standard-dose computed tomography. This technique can be used as both at the first examination and the follow-up examinations. Thin-section computed tomography screenings can be used as a supplement to check if there is any nodules that have not yet been discovered. Computer-aided diagnosis is an add-on method to make sure the computed tomography screenings images are being correctly labeled. Identifying other contributing factors to the effectiveness of the early lung cancer detection, such as the amount of forced expiratory volume, forced vital capacity, and the presence of emphysema, could also decrease the percentage of false positive outcomes.
Date Created
2019-05
Agent

Use of large, immunosignature databases to pose new questions about infection and health status

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Description
Immunosignature is a technology that retrieves information from the immune system. The technology is based on microarrays with peptides chosen from random sequence space. My thesis focuses on improving the Immunosignature platform and using Immunosignatures to improve diagnosis for diseases.

Immunosignature is a technology that retrieves information from the immune system. The technology is based on microarrays with peptides chosen from random sequence space. My thesis focuses on improving the Immunosignature platform and using Immunosignatures to improve diagnosis for diseases. I first contributed to the optimization of the immunosignature platform by introducing scoring metrics to select optimal parameters, considering performance as well as practicality. Next, I primarily worked on identifying a signature shared across various pathogens that can distinguish them from the healthy population. I further retrieved consensus epitopes from the disease common signature and proposed that most pathogens could share the signature by studying the enrichment of the common signature in the pathogen proteomes. Following this, I worked on studying cancer samples from different stages and correlated the immune response with whether the epitope presented by tumor is similar to the pathogen proteome. An effective immune response is defined as an antibody titer increasing followed by decrease, suggesting elimination of the epitope. I found that an effective immune response usually correlates with epitopes that are more similar to pathogens. This suggests that the immune system might occupy a limited space and can be effective against only certain epitopes that have similarity with pathogens. I then participated in the attempt to solve the antibiotic resistance problem by developing a classification algorithm that can distinguish bacterial versus viral infection. This algorithm outperforms other currently available classification methods. Finally, I worked on the concept of deriving a single number to represent all the data on the immunosignature platform. This is in resemblance to the concept of temperature, which is an approximate measurement of whether an individual is healthy. The measure of Immune Entropy was found to work best as a single measurement to describe the immune system information derived from the immunosignature. Entropy is relatively invariant in healthy population, but shows significant differences when comparing healthy donors with patients either infected with a pathogen or have cancer.
Date Created
2018
Agent

Characterization of Zika Virus Inactivated by Ultrashort Pulsed Laser as a Source for Vaccine Development

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Description
The objective of this thesis was to determine whether Zika Virus (ZIKV) can be effectively inactivated by Selective Photonic Disinfection (SEPHODIS) and determine whether key proteins involved in the infection process are preserved, making SEPHODIS a possible source for vaccine

The objective of this thesis was to determine whether Zika Virus (ZIKV) can be effectively inactivated by Selective Photonic Disinfection (SEPHODIS) and determine whether key proteins involved in the infection process are preserved, making SEPHODIS a possible source for vaccine development. As of January 2018, there have been 3,720 confirmed cases of Congenital Zika Syndrome in infants, making a Zika Vaccine a high priority (Mitchell, 2018). SEPHODIS is a process that involves prolonged exposure of an object to a pulsing laser which can render it ineffective. Initially, ZIKV was subjected to laser inactivation for 6 hours, then a plaque assay was performed on both laser-treated and control samples. ZIKV was inactivated two-fold? after laser treatment, when compared with control, as indicated by the plaque assay results. Additionally, both samples were submitted to ELISA to evaluate antigenicity with a panel of monoclonal and human sera. As a second control, virus inactivated by formaldehyde (2%) was used. ELISA results showed that antigenicity of some proteins were preserved while others were probably disturbed. However, ELISA results show that ZIKV envelope protein (E-protein), the protein responsible for viral entry into cells, was effectively preserved after laser-treatment, implying that if laser parameters were tweaked to obtain more complete inactivation, then SEPHODIS may be an appropriate source for the development of a vaccine.
Date Created
2018-05
Agent

A Simple Platform for the Rapid Development of Antimicrobials

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Description

Recent infectious outbreaks highlight the need for platform technologies that can be quickly deployed to develop therapeutics needed to contain the outbreak. We present a simple concept for rapid development of new antimicrobials. The goal was to produce in as

Recent infectious outbreaks highlight the need for platform technologies that can be quickly deployed to develop therapeutics needed to contain the outbreak. We present a simple concept for rapid development of new antimicrobials. The goal was to produce in as little as one week thousands of doses of an intervention for a new pathogen. We tested the feasibility of a system based on antimicrobial synbodies. The system involves creating an array of 100 peptides that have been selected for broad capability to bind and/or kill viruses and bacteria. The peptides are pre-screened for low cell toxicity prior to large scale synthesis. Any pathogen is then assayed on the chip to find peptides that bind or kill it. Peptides are combined in pairs as synbodies and further screened for activity and toxicity. The lead synbody can be quickly produced in large scale, with completion of the entire process in one week.

Date Created
2017-12-14
Agent

Peptide Sequencing Directly on Solid Surfaces Using MALDI Mass Spectrometry

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Description

There are an increasing variety of applications in which peptides are both synthesized and used attached to solid surfaces. This has created a need for high throughput sequence analysis directly on surfaces. However, common sequencing approaches that can be adapted

There are an increasing variety of applications in which peptides are both synthesized and used attached to solid surfaces. This has created a need for high throughput sequence analysis directly on surfaces. However, common sequencing approaches that can be adapted to surface bound peptides lack the throughput often needed in library-based applications. Here we describe a simple approach for sequence analysis directly on solid surfaces that is both high speed and high throughput, utilizing equipment available in most protein analysis facilities. In this approach, surface bound peptides, selectively labeled at their N-termini with a positive charge-bearing group, are subjected to controlled degradation in ammonia gas, resulting in a set of fragments differing by a single amino acid that remain spatially confined on the surface they were bound to. These fragments can then be analyzed by MALDI mass spectrometry, and the peptide sequences read directly from the resulting spectra.

Date Created
2017-12-19
Agent

Entropy is a Simple Measure of the Antibody Profile and is an Indicator of Health Status: A Proof of Concept

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Description

We have previously shown that the diversity of antibodies in an individual can be displayed on chips on which 130,000 peptides chosen from random sequence space have been synthesized. This immunosignature technology is unbiased in displaying antibody diversity relative to

We have previously shown that the diversity of antibodies in an individual can be displayed on chips on which 130,000 peptides chosen from random sequence space have been synthesized. This immunosignature technology is unbiased in displaying antibody diversity relative to natural sequence space, and has been shown to have diagnostic and prognostic potential for a wide variety of diseases and vaccines. Here we show that a global measure such as Shannon’s entropy can be calculated for each immunosignature. The immune entropy was measured across a diverse set of 800 people and in 5 individuals over 3 months. The immune entropy is affected by some population characteristics and varies widely across individuals. We find that people with infections or breast cancer, generally have higher entropy values than non-diseased individuals. We propose that the immune entropy as measured from immunosignatures may be a simple method to monitor health in individuals and populations.

Date Created
2017-12-22
Agent