Biochemistry, Biophysics, and Structural Biology Commons^™

High-Throughput Robotic Ethanol Inhibition Assays For Engineered Thermophilic Biofuel Strains, Kevin He, Daniel Olson, Marybeth Maloney, Anthony Lanahan

Wetterhahn Science Symposium Posters

Ethanol stress assays are commonly used to evaluate microbial tolerance, metabolic adaptation, and fermentation performance. However, manual liquid handling introduces variability across replicate wells and small-volume pipetting steps, limiting reproducibility and throughput. This study developed an automated OT-2 robotic workflow to generate replicated ethanol concentration gradients for high-throughput inhibition assays in engineered thermophilic biofuel strains. Kinetic plate-reader measurements were used to quantify ethanol-dependent growth responses under anaerobic fermentation conditions. The reasearch question is: How do engineered thermophilic biofuel strains differ in ethanol-dependent growth inhibition under anaerobic fermentation conditions, and can automated robotic assays improve the reproducibility of these measurements? Can …

Understanding The Role Of Toxs As A Bile Sensing Component Of The Toxrs Virulence Regulatory System In Vibrio Spp., Minje Kim

Dartmouth College Ph.D Dissertations

Pathogenic Vibrio bacteria, such as V. cholerae and V. parahaemolyticus, colonize in the human small intestine to cause severe gastrointestinal disease. During the infection, these bacteria encounter bile salts, antimicrobial cholesterol metabolites secreted into the intestine. Pathogenic Vibrio species have evolved to utilize bile salts as signals to regulate virulence. The signaling depends in part on ToxRS, a conserved co-component transmembrane transcription regulator. ToxRS consists of the transcription factor ToxR and its membrane-tethered binding partner ToxS. ToxS is required for ToxR stability and full transcriptional activity. Although bile salts are known to influence ToxRS-dependent virulence gene expression, the molecular …

Quantitative Proteomics For The Investigation Of Phosphoprotein Phosphatase 1 And 3 Substrate Specificities, Galini Poimenidou

Dartmouth College Ph.D Dissertations

Reversible phosphorylation is a crucial post-translational modification (PTM) that modulates a variety of signaling pathways intracellularly, with aberrant protein phosphorylation being a hallmark of many human diseases. Kinases, which catalyze phosphorylation of their substrates, have been extensively studied in the context of the signaling pathways they regulate and their effects on cellular processes. In contrast, phosphoprotein phosphatases (PPPs), which catalyze the removal of phosphate groups from substrate proteins, have only recently come to the research spotlight. For a long time, protein phosphatases were deemed unspecific housekeeping enzymes, but they are now known to display exquisite substrate specificity. Phosphoprotein phosphatase 1 …

Fluorescent Protein Imaging Approaches Uncover Dynamic Subcellular Distribution Of Core Clock Proteins In Neurospora Crassa, Ziyan Wang

Dartmouth College Ph.D Dissertations

Circadian clocks are endogenous self-sustained timekeeping systems that allow organisms to anticipate and adapt to daily environmental cycles. Found in diverse forms of life, these molecular clocks regulate the expression of ~ 40% of the genome in animals, fungi, and plants. In animals and fungi, circadian oscillators are built on transcription-translation feedback loops (TTFLs), in which positive regulators drive the expression of negative regulators which, once synthesized and imported into the nucleus, inhibit their own activators. This precisely regulated negative feedback incorporates multiple steps of delays that are essential for generating ~24-hour rhythms. Through these mechanisms, circadian clocks temporally coordinate …

Proteomic Approaches To Investigate Pp2a-B55 Substrates And Cellular Function, Brennan C. Mcewan

Dartmouth College Ph.D Dissertations

Cell division is controlled in large part by reversible protein phosphorylation. The phosphorylation state of proteins during mitosis and other phases of the cell cycle represents a careful balance of activity between kinases and opposing phosphatases. The phosphoprotein phosphatase (PPP) family is responsible for the majority of serine and threonine dephosphorylation. Members of the PPP family are composed of a catalytic subunit paired with a regulatory subunit that targets them towards specific substrates.

The most abundant PPP, PPP2A, paired with its regulatory B55 subunit, is thought to be the phosphatase responsible for the dephosphorylation of substrates during mitotic exit. Despite …

Structural And Functional Lessons Learned About Regulation Of Enterotoxigenic E. Coli Virulence Regulatory Factor, Rns, Jessica Dianne Tolbert

Dartmouth College Ph.D Dissertations

Antibiotic resistance has exacerbated the global health crisis of diarrheal diseases caused by enteric bacterial pathogens. Investigating pathogens, such as Enterotoxigenic Escherichia coli (ETEC) and Vibrio cholerae (cholera), helps to uncover mechanisms for the inhibition of virulence gene expression. A notable member of the AraC transcription factor family in ETEC, Rns, regulates virulence factors including pili and fimbriae, which are essential for adherence and colonization of the intestinal epithelial layer. This microbe–host interaction initiates the release of toxins, leading to the water and ion loss in clinically diagnosed as diarrhea.

In the canonical N-terminal domain of Rns, mutagenesis of the …

Metabolite Analysis To Understand Factors Limiting Microbial Fermentation At High Substrate Concentrations, Bishal D. Sharma

Dartmouth College Ph.D Dissertations

Clostridium thermocellum, a thermophilic anaerobic bacterium, holds promise as a biocatalyst for conversion of lignocellulosic biomass into biofuels. This microbe has been subjected to various metabolic engineering strategies, including the deletion of genes encoding secondary fermentation products such as H₂, formate, acetate, and lactate, as well as the expression of heterologous genes to redirect carbon flux toward ethanol production. Despite these efforts, achieving economically viable ethanol titers remains a challenge. We hypothesized that studying how intracellular metabolite concentrations change as fermentation stops could reveal metabolic bottlenecks or regulatory mechanisms limiting ethanol production at high titers. However, metabolomics studies at …

Biochemical And Structural Insights Into The Yersinia Effector Yopm And Its Negative Regulation Of The Pyrin Inflammasome, Bethany Wairimu Mwaura

Dartmouth College Ph.D Dissertations

Bacteria utilize sophisticated secretion systems to inject effectors into host cells in order to facilitate their survival and replication in the host. Some pathogenic species of Gram-negative bacteria use a conserved contact-dependent T3SS to inject a wide array of effectors. While the effectors diverge in their structures, functions and cell-localization, the T3SS is well conserved. Several effectors discussed in this thesis target key host inflammasome responses. The focus of this work is how the Yersinia effector YopM inhibits the pyrin inflammasome. During Yersinia infection, two effectors, YopE and YopT inadvertently activate the pyrin inflammasome while targeting RhoA to avoid phagocytosis. …

Proteomic-Based Strategies To Determine Aberrant Signaling In Cancer, Natasha Chipman Mariano

Dartmouth College Ph.D Dissertations

Proteomics and phosphoproteomics have emerged as powerful tools to elucidate the intricate molecular underpinnings that drive cancer development by quantifying changes in protein and post-translational modification abundances. Throughout my thesis work, I have advanced these techniques to map cancer signaling networks on a global scale. Among breast cancer subtypes, triple-negative (TNBC) remains the most challenging to treat, with poorer clinical outcomes attributed to tumor heterogeneity and yet unidentified, oncogenic driver proteins for therapeutic targeting. To identify potential targeted treatment strategies, we employed mass spectrometry-based quantitative proteomics to analyze 55 formalin-fixed paraffin- embedded TNBC tumor specimens. Unsupervised hierarchical clustering of relative …

Mechanisms Of Macrophage Metabolic Activation And Paracrine Wnt Signaling In The Pathogenesis Of Systemic Sclerosis, Emily Ann Morris

Dartmouth College Ph.D Dissertations

Systemic sclerosis (SSc) is a chronic autoimmune disease of unknown etiology. We have previously shown that macrophages (MØs) play a critical role in its pathogenesis; however, the mechanisms driving MØ activation in SSc remain poorly understood. This dissertation investigates the molecular signaling pathways and biochemical mechanisms underlying profibrotic MØ activity in SSc.

First, I identify a novel MØ-specific effect of mycophenolate mofetil (MMF), the standard-of-care treatment for SSc. While MMF is a well characterized lymphostatic, my findings demonstrate that its active metabolite, mycophenolic acid (MPA), is also capable of directly inhibiting myeloid viability and profibrotic MØ activation by suppressing de …

The Lc3-Interacting Region Of Nbr1 Is A Protein Interaction Hub Enabling Optimal Flux, Brian Joseph North

Dartmouth College Ph.D Dissertations

Autophagy is a highly conserved pathway that maintains cell health by breaking down and recycling cellular components such as protein aggregates or damaged organelles. During autophagy, potentially toxic cargo is enveloped by a newly formed autophagosome and trafficked to the lysosome for degradation. Ubiquitinated protein aggregates, a key target for autophagy, are identified by multiple autophagy receptors. NBR1 is an archetypal autophagy receptor and an excellent model for deciphering the role of the multivalent, heterotypic interactions made by cargo-bound receptors. Using NBR1 as a model, we find that three critical binding partners—ATG8-family proteins, FIP200, and TAX1BP1—each bind to a short …

Characterization Of The Erv41-Erv46 Complex As A Retrograde Receptor For Misfolded Secretory Proteins, John Andrew Fuesler

Dartmouth College Ph.D Dissertations

The Endoplasmic Reticulum (ER), the site of secretory protein biosynthesis

provides a favorable environment to promote polypeptide folding, protein

oligomerization and export. Although the ER contains many chaperones and other

factors that assist in protein folding, this process is error prone. Eukaryotes have

evolved protein quality control checkpoints to maintain homeostasis in the secretory

pathway, however these processes are imperfect and may result in proteotoxicity

when toxic levels or aggregates of proteins arise. Mutations in proteins involved in

trafficking in the early secretory pathway are closely associated with disease states.

Therefore, it is of great interest to further understand how …

Targeting The Cholesterol Storage Enzyme Acat1/Soat1 In Brain Cells And Mouse Model: A Novel Approach To Address Aging And Apoe4-Related Neuroinflammation, Thao Nguyen Phuong Huynh Krumeich

Dartmouth College Ph.D Dissertations

Alzheimer’s Disease (AD) is a progressive neurodegenerative disease that significantly impacts nearly 7 million people in the United States. AD is characterized by the deposition of amyloid beta (Ab) plaque, tau neurofibrillary tangles (NFTs), lipids granules, and neuroinflammation. Age and apolipoprotein E4 (APOE4) are the two biggest risk factors for AD. Recent AD therapeutic development has mostly benefited the patient population with milder symptoms while causing serious side effects in APOE4 carriers, leaving the most impacted patients’ group - aged APOE4 carriers with no treatment option. With the increasing aging population, there is an urgent need for a …

Characterization Of Stealth Liposome-Based Nanoparticles Encapsulating Acat1/Soat1 Inhibitor F26: Potential Therapeutics For Niemann-Pick Type C And Other Neurodegenerative Diseases., Junghoon Lee

Dartmouth College Ph.D Dissertations

Cholesterol dysregulation is implicated in neurodegenerative diseases such as Alzheimer's disease (AD), Parkinson’s disease (PD), Huntington’s disease (HD) and Niemann-Pick type C disease (NPCD). This study focused on evaluating the potent ACAT1 inhibitor, F26, as a therapeutic strategy for NPCD. F26 demonstrated superior ACAT1 inhibition and efficacy compared to the previously studied inhibitor, F12511, both in vitro and in vivo. Notably, F26 exhibited enhanced pharmacokinetic properties, including prolonged duration of action and better brain retention, making it a more promising candidate for treating neurodegenerative diseases.

F26 was encapsulated in a liposome-based nanoparticle system, DSPE-PEG2000 with phosphatidylcholine (PC), for enhancing its …

Computational Modelling And Design Of Antibodies: Benefits From Analysis Of Their Unique Structural Motifs, Katherine M. Mccoy

Dartmouth College Ph.D Dissertations

The complexes that antibodies make with their binding partners, or antigens, are especially valuable to be able to predict and modify due to their unique role in the immune system. Yet, they present significant challenges to computational methods of both modelling and design. Antibodies are unlike most other proteins in that they are composed of a scaffold region, which is a highly conserved structure that is largely the same between antibodies of the same class, and Complementary Determining Regions (CDRs), which are comprised of hypervariable loops that largely determine their binding motifs. Additionally, antibodies and their antigens do not co-evolve …

Role Of Sds-22/Pp1 Phosphatase In Polarizing The Germplasm Of Caenorhabditis Elegans Embryo, Aparna Nurni Ravi

Dartmouth College Ph.D Dissertations

During asymmetric cell division, cell polarity and cell cycle are tightly coupled to ensure robust segregation of cell fate determinants and generation of cellular diversity. In the one-cell C. elegans embryo, multiple cell cycle kinases regulate cell polarization and posterior segregation of germline fate determinants (germplasm). For example, PLK-1 kinase inhibits the retention of its germplasm substrate POS-1 in the anterior, driving POS-1 segregation to the posterior (Han et al., 2018). Additionally, MBK-2 kinase disassembles P granules in the anterior through phosphorylation of the P granule scaffold MEG-3, helping to drive P granule segregation to the posterior (Wang et al., …

Wee1 And Cell Size Control In Fission Yeast By The Protein Kinase Cdr2, Rachel Berg-Murante

Dartmouth College Ph.D Dissertations

The mechanisms that govern cell size have long been topics of study in the field of cell biology. In eukaryotic cells this size control is tied to checkpoints, a set threshold of minimum necessary growth linked to cyclin dependent kinase activity regulation. In the fission yeast Schizosaccharomyces pombe, the Cdk1 regulatory network is conserved, and G2/M represents the major size checkpoint. Prior to mitosis, Cdk1 is inhibited by phosphorylation applied by Wee1 during G2 phase. Once S. pombe cells have satisfied the size checkpoint, Cdk1 is activated through dephosphorylation by Cdc25. Wee1 is a dose-dependent regulator of mitotic entry …

Establishment Of Bacteroides In The Gut And Its Role In The Cystic Fibrosis Gut-Lung Axis, Rebecca A. Valls

Dartmouth College Ph.D Dissertations

In the quest to understand the complex interplay between the gut microbiota and cystic fibrosis (CF), a disease characterized by chronic upper respiratory complications and an exacerbated proinflammatory response, our lab engaged in a collaborative study with Dartmouth-Hitchcock Medical Center (DHMC) to characterize the gut microbiota of pediatric CF patients. Initial analyses established a connection between gut microbial composition and respiratory health, particularly highlighting a scarcity of Bacteroides species compared to healthy controls. In following investigations, we utilized random forest models to understand how stool microbiota may influence clinical outcomes of these pediatric CF patients, including: age, upper respiratory infections, …

Quantitative Proteomic Strategies To Determine Substrate Specificities Of Phosphoprotein Phosphatases, Hieu Trung Nguyen

Dartmouth College Ph.D Dissertations

Reversible phosphorylation is a crucial regulatory mechanism of cellular signaling pathways. Being the most prevalent post-translational modification (PTM) in the cells, with over 75% of all proteins detected to be phosphorylated, phosphorylation regulates a significant number of important cellular processes that have implications in various diseases. Phosphorylation is carried out by protein kinases, which have been extensively studied. However, the opposite reaction, carried out by protein phosphatases, has lagged significantly, exposing a gap of knowledge that is required to be investigated to delineate the kinase-substrate-phosphatase relationship. Phosphoprotein phosphatase family (PPPs), containing seven members of phospho-Serine (pS) and phospho-Threonine (pT) phosphatases, …

Understanding The Non-Canonical Regulation Of Srebp In Aspergillus Fumigatus, Muhammad Abubakar Khan

Dartmouth College Ph.D Dissertations

Aspergillus fumigatus is an opportunistic fungal pathogen causing invasive pulmonary aspergillosis (IPA), with high mortality rates in immunocompromised individuals. Adaptation to the hypoxic microenvironment of IPA is crucial for fungal virulence. The transcription factor SrbA, a Sterol Regulatory Element-Binding Protein (SREBP) homolog, plays a key role in this hypoxic response and regulates genes involved in hypoxic growth, sterol biosynthesis, and azole resistance, making it an attractive therapeutic target.

However, SrbA activation in A. fumigatus lacks critical components of the canonical SREBP pathway, such as SCAP, Site-1 protease (S1P), and Site-2 protease (S2P). Instead, the rhomboid protease RbdB, signal peptide peptidase …

Structure-Based Targeting Of The Nemo:Ikk Interaction For Canonical Nf-Κb Inhibition, Amy Kennedy

Dartmouth College Ph.D Dissertations

The NF-κB pathway is important for cell survival and proliferation, inflammation, and innate immunity, and its dysregulation is a common theme in many cancers, autoimmune disorders, and other disease states. The protein-protein interaction between the scaffolding protein NEMO and the kinase IKK in the NF-κB pathway represents a compelling target for selective NF-κB inhibition because it occurs only in the canonical branch of the NF-κB pathway. Disruption of the NEMO:IKK interaction has been established for decades in the literature as a safe and effective way to selectively inhibit overactivation of the canonical branch of the NF-κB pathway. The benchmark in …

Mitochondrial Quality Control By Tail-Anchored Proteins, Jose M. Delgado

Dartmouth College Ph.D Dissertations

Autophagy is a lysosome-mediated pathway responsible for the degradation of unwanted cytosolic content. During autophagy, cytoplasmic components are enveloped by a newly generated vesicle (the autophagosome), trafficked to the lysosome, and degraded. The power of autophagy lies in its ability to selectively target specific substrates for degradation—a phenomenon known as selective autophagy.

Specialized proteins known as selective autophagy receptors play a crucial role in identifying and targeting autophagy cargo. Although historically overlooked as potential regulators, our understanding of autophagy receptors is evolving beyond the assumption that receptors merely bridge targets to pre-formed autophagosomal membranes. Previous insights were often based on …

Exploring 3d Genome Interaction And Epigenetic Regulation Via Swi/Snf Complex And Deep Learning Models, Ruoyun Wang

Dartmouth College Ph.D Dissertations

The three-dimensional organization of the genome is fundamental in regulating gene expression and maintaining cellular function. This organization's complexities, influenced by epigenetic marks and chromatin remodeling complexes, are crucial for understanding genomic regulation. Among these, the SWI/SNF complexes are key, facilitating chromatin accessibility and regulating gene activity across cell types. The first part of my dissertation focuses on SWI/SNF complexes, exploring their role in chromatin remodeling and their impact on 3D genome architecture. Utilizing next-generation sequencing (NGS) techniques, this section investigates the interplay between these complexes and chromatin structure. During my research on the SWI/SNF complex, I was intrigued by …

Molecular Mechanisms Regulating Prometaphase And Metaphase States For Faithful Chromosome Segregation, Sarah Yvette Valles

Dartmouth College Ph.D Dissertations

Cells progress through different stages of the cell cycle as they ultimately prepare to divide during mitosis. Mitosis relies on many interconnected networks to carry out the coordinated events required for faithful chromosome segregation. When a cell enters mitosis, chromosomes are highly condensed and sister chromatids are held together by cohesion. Kinetochores assemble at the constricted regions on each chromosome. The kinetochore is a large macromolecular structure composed of many proteins that form the binding site for microtubules of the mitotic spindle to attach. These kinetochore-microtubule (k-MT) attachments serve to align chromosomes at the center of the cell and are …

Proteomic Approaches To Identify Unique And Shared Substrates Among Kinase Family Members, Charles Lincoln Howarth

Dartmouth College Ph.D Dissertations

Protein phosphorylation is a reversible post-translational modification that is a critical component of almost all signaling pathways. Kinases regulate substrate proteins through phosphorylation, and nearly all proteins are phosphorylated to some extent. Crucially, breakdown in phosphorylation signaling is an underlying factor in many diseases, including cancer. Understanding how phosphorylation signaling mediates cellular pathways is crucial for understanding cell biology and human disease.

Targeted protein degradation (TPD) is a strategy to rapidly deplete a protein of interest (POI) and is applicable to any gene that is amenable to CRISPR-Cas9 editing. One TPD approach is the auxin-inducible degron (AID) system, which relies …

Regulation Of The Wnt/Wingless Receptor Lrp6/Arrow By The Deubiquitylating Complex Usp46, Zachary T. Spencer

Dartmouth College Ph.D Dissertations

The evolutionarily conserved Wnt/Wingless signal transduction pathway is critical for the proper development of all animals and implicated in numerous diseases in adulthood. Upon binding of the Wnt/Wingless ligand, a cascade of events culminates in inactivation of the destruction complex, a negative regulator of the pathway, and the subsequent formation of singalosomes which mediate pathway activation. A critical component of signalosome formation is the Wnt/Wingless receptor LRP6/Arrow. Upon canonical pathway activation, LRP6/Arrow undergoes activation via phosphorylation by several kinases and complexes with another Wnt/Wingless receptor Frizzled, along with several cytoplasmic components. While many studies have investigated the regulatory mechanisms of …

The Molecular And Cellular Response To Acat1/Soat1 Inhibition, Taylor C. Harned

Dartmouth College Ph.D Dissertations

Cholesterol is an important component of all mammalian cell membranes. It governs the membrane’s physical properties and creates the membrane order and heterogeneity required for complex membrane-related processes. Tight regulation of cholesterol levels and distribution are necessary for maintaining proper cell health. Likewise, disruptions in cholesterol homeostasis have been implicated in a variety of diseases, including Alzheimer’s disease (AD). Our lab, and others, have demonstrated the benefits of blocking acyl-CoA:cholesterol acyltransferase1/sterol O:acyltransferase 1 (ACAT1/SOAT1) in AD models by genetic ablation or pharmacological inhibition. We understand that blocking ACAT1/SOAT1 activity reduces amyloid and tau pathology, and that this is, at least …

Structural Files For The Etr1 Ethylene-Receptor Dimer Based On Computational Modeling, Beenish J. Azhar, Safdar Abbas, Sitwat Aman, Maria V. Yamburenko, Wei Chen, Lena Muller, Buket Uzun, David A. Jewell, Jian Dong, Samina N. Shakeel, Georg Groth, Brad M. Binder, Gevorg Grigoryan, G. Eric Schaller

Dartmouth Scholarship

Structural models for the ETR1 homodimer were generated with AlphaFold-Multimer. Coppers were modeled under two potential coordinations involving Cys65 and His69 of the ETR1 homodimer, one in which the two coppers are bound independently and do not share an interaction with each other, and another where they are closely bonded.

See the following publication for details: Azhar, B.J., Abbas, S., Aman, S., Yamburenko, M.V., Chen, W., Müller, L., Uzun, B., Jewell, D.A., Dong, J., Shakeel, S.N., Groth, G., Binder, B.M., Grigoryan, G., Schaller, G.E. (2023) Basis for high-affinity ethylene binding by the ethylene receptor ETR1 of Arabidopsis. Proc. Natl. Acad. …

Molecular Mechanisms Of Wild-Type And Mutant Prion Formation, Daniel J. Walsh

Dartmouth College Ph.D Dissertations

Prion diseases are a class of infectious neurodegenerative disorders which affect humans and many other mammalian species. The causative agent is a unique pathogen known as a prion or PrPSc, a misfolded form of a host-encoded glycoprotein which replicates by templated conformational change. Distinct strains of prions with unique phenotypic and pathologic presentations appear to be encoded by subtle conformational changes within the misfolded protein. While the general manner of prion transmission is known, our detailed understanding of these mechanisms remains incomplete, limiting efforts for the discovery or design of therapeutic treatments for these fatal diseases. In vitro synthesis of …

Interactomics And Targeted Protein Degradation For Kinase Substrate Discovery, Juan C. Mercado Del Valle

Dartmouth College Ph.D Dissertations

Reversible phosphorylation is one of the most important post translational modifications that has allowed us as a species to quickly adapt to changing molecular environments due to external stimulation. This process is only capable through the activity of kinases to carry out the targeting of specific substrates defined by their recognition motif allowing for selective phosphorylation and activation and inactivation of distinct pathways as well as other changes that permit cell survival. By being so important for the maintenance of the cells disruption often leads to worsening of the cells, leading to various diseases like cancer, immunological and neurodegenerative disorders. …