Cell Biology Commons^™

Chemical Damage To Mrna And Its Impact On Ribosome Quality-Control And Stress-Response Pathways In Eukaryotic Cells, Liewei Yan

Arts & Sciences Electronic Theses and Dissertations

Ribosome often faces defective adducts that disrupt its movement along the mRNA template. These adducts are primarily caused by chemical damage to mRNA and are highly detrimental to the decoding process on the ribosome. Hence, unless dealt with, chemical damage to RNA has been hypothesized to lead to the production of toxic protein products. Even more detrimental is the ability of damaged mRNA to drastically affect ribosome homeostasis through stalling. This in turn would lead to greatly diminished translation capacity of cells. Therefore, the inability of cells to recognize and resolve translational-stalling events is detrimental to proteostasis and could even …

Nonsense Mediated Rna Decay Promotes Survival Of Cells With Defective Splicing, Abigael Jeruto Cheruiyot

Arts & Sciences Electronic Theses and Dissertations

Nonsense mediated RNA decay (NMD) is an RNA surveillance pathway present in all eukaryotes that detects and degrades nonsense mRNAs, which contain pre-mature translation termination codons. Nonsense mRNAs are prevalent when pre-mRNA splicing is altered or defective. Interestingly, defective pre-mRNA splicing is emerging as a major driver of cancer development, including development of myelodysplastic syndrome (MDS), leukemia, and some solid tumors. Moreover, pre-mRNA splicing is also thought to enhance NMD in human cells, although itճ still unclear whether and how splicing or splicing factors promote NMD. The role of NMD in regulating mis-spliced mRNA and the link between NMD and …

Circadian Regulation Of Temozolomide Sensitivity In Glioblastoma, Emily A. Slat

Arts & Sciences Electronic Theses and Dissertations

The safety and efficacy of multiple cancer chemotherapeutics can vary as a function of when during the day they are delivered. This study aimed to improve the treatment of glioblastoma multiforme (GBM), the most common brain cancer, by testing the efficacy of the DNA alkylator Temozolomide (TMZ) on GBM in vitro and in vivo as a function of time of day. We found cell-intrinsic, daily rhythms in susceptibility of GBM tumor cells (mouse astrocytes deficient in NF1 and p53 signaling) to TMZ in vitro. The greatest TMZ-induced DNA damage response, activation of apoptosis and growth inhibition, occurred near the peak …

Regulation Of Epithelial Proliferation And Migration By Apical-Basal Polarity Proteins, Gregory Vincent Schimizzi

Arts & Sciences Electronic Theses and Dissertations

Epithelial cells line all the outside surfaces of the body where they perform essential roles in maintaining homeostasis. In addition, epithelial tissues are implicated in many disease processes and are the most common tissue type to give rise to human cancer. Therefore, a thorough understanding of epithelial development and homeostasis has broad implications for understanding human development, health, and disease. The establishment and maintenance of apical-basal polarity is a defining characteristic and essential feature of functioning epithelia. Proper apical-basal polarity (ABP) is required for epithelial tissues to carry out their functions, which include absorption, secretion, barrier formation, and collective migration. …

Mechanism Of Gene Regulation By Coding Polya Tracks, Laura Lea Arthur

Arts & Sciences Electronic Theses and Dissertations

Regulation of gene expression is essential for cellular development and survival. The great variety and complexity of regulatory mechanisms underscores this fact. Messenger RNA stability and translational efficiency are often key determinants of gene expression. mRNA surveillance pathways, discovered for their role in degradation of aberrant mRNA, are now known to be instrumental in the regulation of physiologically correct mRNA stability. Thus, the study of cis elements in a transcript that can induce mRNA surveillance pathways has become an area of particular interest.

Here I report on the mechanism of gene regulation by coding polyA tracks, defined as a sequence …

Characterization And Function Of Islet Antigen Presenting Cells During Nod Diabetes, Stephen Thomas Ferris

Arts & Sciences Electronic Theses and Dissertations

Here we characterized the initial antigen presenting cells (APCs) within the islet of Langerhans to ascertain their identity and functional role as it pertains to autoimmune diabetes. The activation of the adaptive immune system is induced by the innate immune system, and more specifically APCs. Therefore, it is crucial to identify the APCs that are initiating T1D in order to elucidate the break in tolerance and intervene in order to inhibit progression. We have found that there is a resident macrophage that is present in all strains of mice. This islet macrophage has a distinct transcriptional profile that is unique …

Factors That Contribute To De Novo Protein Misfolding And Prion Formation In Saccharomyces Cerevisiae, Kathryn Morgan Keefer

Arts & Sciences Electronic Theses and Dissertations

Protein misfolding is a common phenomenon that can have severe consequences on cellular and organismal health. Despite this, the causes of protein misfolding remain poorly understood. Prions are a class of proteins that, when misfolded, can convert other molecules into a heritable, non-native conformation. The yeast Saccharomyces cerevisiae naturally harbors several diverse prion-forming proteins; thus, it is an ideal model with which to investigate the factors that influence misfolding and aggregation.This thesis utilizes the yeast prions [PSI+] and [RNQ+] to investigate two distinct steps of the protein misfolding pathway: interactions with chaperones and their cofactors, and heterologous templating by other …

Mitochondrial Dynamics Controls T Cell Fate Through Metabolic Programming, Michael Buck

Arts & Sciences Electronic Theses and Dissertations

Activated effector T (TE) cells augment anabolic pathways of metabolism, such as aerobic glycolysis, while memory T (TM) cells engage catabolic pathways, like fatty acid oxidation (FAO). However, signals that drive these differences remain unclear. Mitochondria are metabolic organelles that actively transform their ultrastructure. Therefore, we questioned whether mitochondrial dynamics controls T cell metabolism. We show that TE cells have punctate mitochondria, while TM cells maintain fused networks. The fusion protein Opa1 is required for TM, but not TE cells after infection, and enforcing fusion in TE cells imposes TM cell characteristics and enhances antitumor function. Our data suggest that, …

Stochastic Models For Plant Microtubule Self-Organization And Structure, Ezgi Can Eren, Ram Dixit, Natarajan Gautam

Biology Faculty Publications & Presentations

One of the key enablers of shape and growth in plant cells is the cortical microtubule (CMT) system, which is a polymer array that forms an appropriately-structured scaffolding in each cell. Plant biologists have shown that stochastic dynamics and simple rules of interactions between CMTs can lead to a coaligned CMT array structure. However, the mechanisms and conditions that cause CMT arrays to become organized are not well understood. It is prohibitively time-consuming to use actual plants to study the effect of various genetic mutations and environmental conditions on CMT self-organization. In fact, even computer simulations with multiple replications are …

Migration In The Social Stage Of Dictyostelium Discoideum Amoebae Impacts Competition, Chandra N. Jack, Neil J. Buttery, Boahemaa Adu-Oppong, Michael Powers, Christopher R.L. Thompson, David Queller, Joan E. Strassmann

Biology Faculty Publications & Presentations

Interaction conditions can change the balance of cooperation and conflict in multicellular groups. After aggregating together, cells of the social amoeba Dictyostelium discoideum may migrate as a group (known as a slug) to a new location. We consider this migration stage as an arena for social competition and conflict because the cells in the slug may not be from a genetically homogeneous population. In this study, we examined the interplay of two seemingly diametric actions, the solitary action of kin recognition and the collective action of slug migration in D. discoideum, to more fully understand the effects of social competition …

Expressing And Characterizing Mechanosensitive Channels In Xenopus Oocytes, Grigory Maksaev, Elizabeth S. Haswell

Biology Faculty Publications & Presentations

The oocytes of the African clawed frog (Xenopus laevis) comprise one of the most widely used membrane protein expression systems. While frequently used for studies of transporters and ion channels, the application of this system to the study of mechanosensitive ion channels has been overlooked, perhaps due to a relative abundance of native expression systems. Recent advances, however, have illustrated the advantages of the oocyte system for studying plant and bacterial mechanosensitive channels. Here we describe in detail the methods used for heterologous expression and characterization of bacterial and plant mechanosensitive channels in Xenopus oocytes.

Serotonergic Signaling Pathways That Suppress Amyloid Beta In Mouse Models Of Ad, Jonathan Robert Fisher

All Theses and Dissertations (ETDs)

A diagnosis of Alzheimer's disease is one of the most devastating things one can hear. This terrible disease robs people of their ability to remember cherished events as their brains become riddled with beta amyloid plaques. Alzheimer's is especially terrifying because there currently are no effective treatments for slowing or stopping the disease. However, recent research has shown that plaque formation is correlated to concentrations of amyloid beta. This discovery suggests that limiting amyloid beta production could potentially halt the disease. One promising avenue for slowing amyloid beta production is serotonergic signaling.

This dissertation presents evidence for a direct sequence …

Microtubule Severing At Crossover Sites By Katanin Generates Ordered Cortical Microtubule Arrays In Arabidopsis, Quan Zhang, Erica Fishel, Tyler Bertroche, Ram Dixit

Biology Faculty Publications & Presentations

Highlights

• Severing primarily depolymerizes the overlying CMT at crossover sites
• Severing probability increases nonlinearly with crossover time
• Katanin localizes to crossover sites and is required for severing
• Loss of katanin activity prevents the formation of coaligned CMT arrays

Summary
The noncentrosomal cortical microtubules (CMTs) of land plants form highly ordered parallel arrays that mediate cell morphogenesis by orienting cellulose deposition [1, 2 and 3]. Since new CMTs initiate from dispersed cortical sites at random orientations [4], parallel array organization is hypothesized to require selective pruning of CMTs that are not in the dominant orientation. Severing of CMTs at crossover sites …

A Force Of Nature: Molecular Mechanisms Of Mechanoperception In Plants, Gabriele B. Monshausen, Elizabeth S. Haswell

Biology Faculty Publications & Presentations

The ability to sense and respond to a wide variety of mechanical stimuli-gravity, touch, osmotic pressure, or the resistance of the cell wall-is a critical feature of every plant cell, whether or not it is specialized for mechanotransduction. Mechanoperceptive events are an essential part of plant life, required for normal growth and development at the cell, tissue, and whole-plant level and for the proper response to an array of biotic and abiotic stresses. One current challenge for plant mechanobiologists is to link these physiological responses to specific mechanoreceptors and signal transduction pathways. Here, we describe recent progress in the identification …

Plant Cytoskeleton: Della Connects Gibberellins To Microtubules, Ram Dixit

Biology Faculty Publications & Presentations

A new study reveals that DELLA proteins directly interact with the prefoldin complex, thus regulating tubulin subunit availability in a gibberellin-dependent manner. This finding provides a mechanistic link between the growth-promoting plant hormone gibberellin and cortical microtubule organization.

Computer Simulation And Mathematical Models Of The Noncentrosomal Plant Cortical Microtubule Cytoskeleton, Ezgi Can Eren, Natarajan Gautam, Ram Dixit

Biology Faculty Publications & Presentations

There is rising interest in modeling the noncentrosomal cortical microtubule cytoskeleton of plant cells, particularly its organization into ordered arrays and the mechanisms that facilitate this organization. In this review, we discuss quantitative models of this highly complex and dynamic structure both at a cellular and molecular level. We report differences in methodologies and assumptions of different models as well as their controversial results. Our review provides insights for future studies to resolve these controversies, in addition to underlining the common results between various models. We also highlight the need to compare the results from simulation and mathematical models with …

Putting A Bifunctional Motor To Work: Insights Into The Role Of Plant Kch Kinesins, Ram Dixit

Biology Faculty Publications & Presentations

Comment on: A novel actin-microtubule cross-linking kinesin, NtKCH, functions in cell expansion and division. [New Phytol. 2012 Feb;193(3):576-89. doi: 10.1111/j.1469-8137.2011.03944.x. ]

Single-Molecule Analysis Of The Microtubule Cross-Linking Protein Map65-1 Reveals A Molecular Mechanism For Contact-Angle-Dependent Microtubule Bundling, Amanda Tulin, Sheri Mcclerklin, Yue Huang, Ram Dixit

Biology Faculty Publications & Presentations

Bundling of microtubules (MTs) is critical for the formation of complex MT arrays. In land plants, the interphase cortical MTs form bundles specifically following shallow-angle encounters between them. To investigate how cells select particular MT contact angles for bundling, we used an in vitro reconstitution approach consisting of dynamic MTs and the MT-cross-linking protein MAP65-1. We found that MAP65-1 binds to MTs as monomers and inherently targets antiparallel MTs for bundling. Dwell-time analysis showed that the affinity of MAP65-1 for antiparallel overlapping MTs is about three times higher than its affinity for single MTs and parallel overlapping MTs. We also …

Chapter 26 – Multiple Color Single Molecule Tirf Imaging And Tracking Of Maps And Motors, Jennifer L. Ross, Ram Dixit

Biology Faculty Publications & Presentations

Microtubules are part of a complex mechano-chemical network inside cells. In order to understand how the components of these systems work together, careful in vitro experiments must be performed with added complexity. These experiments can ideally image all the interacting species. In order to image these molecules, multiple-color fluorescence imaging can be performed. In this chapter, we describe some methods for performing multiple-color single molecule fluorescence imaging using total internal reflection fluorescence microscopy. We give several specific examples of species of microtubule-associate proteins and motors that can be examined with detailed protocols for labeling, purification, and imaging.

Chapter 27 – Studying Plus-End Tracking At Single Molecule Resolution Using Tirf Microscopy, Ram Dixit, Jennifer L. Ross

Biology Faculty Publications & Presentations

The highly dynamic microtubule plus-ends are key sites of regulation that impact the organization and function of the microtubule cytoskeleton. Much of this regulation is performed by the microtubule plus-end tracking (+TIP) family of proteins. +TIPs are a structurally diverse group of proteins that bind to and track with growing microtubule plus-ends in cells. +TIPs regulate microtubule dynamics as well as mediate interactions between microtubule tips and other cellular structures. Most +TIPs can directly bind to microtubules in vitro; however, the mechanisms for their plus-end specificity are not fully understood. Cellular studies of +TIP activity are complicated by the fact …