The APOE gene is of profound importance regarding the onset of Alzheimer's disease (AD). From the small physical differences among the protein products of the isoforms of this gene arises a profound difference in their physiologies. For example, the APOE2 isoform confers resistance to AD, the APOE3 isoform confers neutral susceptibility to AD, and the APOE4 isoform confers proneness to AD. L-cysteine is an amino acid that has several anti-AD properties, among which are its ability to sequester iron and form glutathione – a powerful antioxidant – and therefore may be a promising potential dietary supplement for ameliorating AD pathology. In our experiment, we fed Mus musculus (mice) homozygous for APOE2, APOE3, and APOE4 either a control diet or a diet high in L-cysteine. Using Western blotting analysis, we quantified Amyloid β (Aβ), hyper-phosphorylated Tau (HP-Tau), and the three APOE proteins that we extracted from post-mortem brains of APOE2, APOE3, and APOE4 homozygous mice of 3-, 6-, 9-, and 12-month ages. We calculated a three-way ANOVA on a sample of 86 mice to examine the effect of age, genotype, and diet on protein quantities. We found that administration of L-cysteine trends towards lowering levels of Aβ in each cohort, but this effect is statistically insignificant. On the other hand, L-cysteine caused a significant decrease in APOE production with regard to diet [F(1,62) = 6.17, p=0.02], indicating that less APOE is produced due to the decrease in Aβ burden. Furthermore, administration of L-cysteine revealed no significant impact on or trends regarding HP-Tau deposition between diet types for each cohort. However, we observed that L-cysteine appeared to nullify the increasing trend in HP-Tau deposition between APOE2 and APOE4 cohorts. Thus, L-cysteine may be weakly affecting HP-Tau deposition via its ability to somewhat reduce Aβ burden and consequently prevent the shutdown of the proteosomes responsible for the degradation and clearance of HP-Tau. Taken together, these data suggest that L-cysteine should be considered as an intervention for AD pathology.

Diagnosing disease in equine neonates poses a challenge for the equine industry because of the nonspecific manifestations of many diseases and the rapid deterioration that occurs. The differential diagnostic procedure requires many laboratory tests, whose results take days to receive. Serum amyloid A (SAA) is the only major acute phase protein identified in the horse; it exists in low levels in the healthy horse and increases over 100 fold in response to inflammatory stimulus 6-8 hours post stimulus. A point of care test allows veterinarians to obtain a SAA concentration within minutes that indicates the existence of infection. Being able to test and quantify this protein at the onset of illness may reduce the time before treatment is initiated and therefore increase the chance of survival for the equine neonate, which would greatly help a large problem in the industry.

Alzheimer’s disease is the most common form of dementia among older adults, and directly contributes to the third leading cause of death in the United States. Although amyloid plaques and tau-loaded neurofibrillary tangles have been identified as the main pathological features of Alzheimer’s disease for more than one hundred years, the molecular mechanism is still poorly understood and treatments are limited to palliative care. Oligomeric Amyloid beta plays a crucial synaptotoxic role in Alzheimer’s disease, and hyperphosphorylated tau facilitates Amyloid beta toxicity, but the link between the two remains controversial. Since tau is a microtubule associated protein and microtubules are critical for neuronal functions, regulation of dynamic microtubules may serve as the link between Amyloid beta and tau. Here I propose a model in which Amyloid beta can induce changes in MT dynamics in dendrites and axons that are primary to tau hyperphosphorylation, while these MT changes are sufficient to cause tau hyperphosphorylation and necessary for Amyloid beta synaptotoxicity through tau. My thesis work further characterizes mammalian excitatory presynaptic boutons as hotspots for activity-dependent dynamic microtubule nucleation that is required for synaptic transmission during neuronal activation or Amyloid beta-induced neuronal injury through tau.

Although transition metals are essential for life, misregulation of redox-active metal uptake, delivery, storage, and excretion has been linked with a series of neurodegenerative disorders. Alzheimer's disease (AD) is considered an epidemic and is the most widespread of all forms of dementia. Copper ions found in large concentrations localized in amyloid-ß plaques in the brain of AD patients have been linked with the generation of reactive oxygen species which are suspected to be the culprits leading to neuronal cell death. Herein a series of mechanistic and spectroscopic studies elucidate the chemistry about the metal-centered oxidation of biomolecules, including catecholamine neurotransmitters and some analogues by copper-complexes of amyloid-ß peptide. Transition metals can also be useful tools for characterization of metalloproteins due to their unique chemical and spectroscopic features. Herein a series of studies of the native Zn²+ and Cu²+-derivative of recombinant Blastula Protease 10 (BP10) from the sea urchin Paracentrotus lividus are presented in order to elucidate its catalytic mechanism, with the use of enzymology, metal substitution, and electronic absorption spectroscopy.

A recent epidemiological study suggested that higher caffeine intake reduces the risk of Alzheimer's disease (AD). Caffeine, a widely consumed stimulatory drug, is a non-selective adenosine receptor antagonist that has been shown to increase plasma adenosine levels in rodents. To determine any long-term protective effects of caffeine in a controlled longitudinal study, caffeine was added to the drinking water of APPsw transgenic (Tg) mice between 4 and 9 1/2 months of age, with behavioral testing done during the last 6 weeks of treatment. The average daily intake of caffeine per mouse (1.5 mg) was the human equivalent of 5 cups of coffee/day. Across multiple cognitive tasks of spatial learning/reference memory, working memory, and recognition/identification, Tg mice given caffeine (Tg+Caff) performed significantly better than Tg control mice and similar to non-transgenic controls. Discriminant Function Analysis involving multiple cognitive measures clearly showed the superior overall cognitive performance of Tg+Caff mice compared to Tg controls. Analysis of Aβ in the hippocampus by ELISA revealed Tg+Caff mice had significantly less soluble Aβ1-40 and insoluble Aβ1-42. In a follow-up study involving neurochemical analysis only, caffeine was added to the drinking water of 17 month old APPsw mice for 18 days. In this study, Tg+Caff mice also showed a significant reduction of insoluble Aβ1-42 in the hippocampus. In contrast to the reduced extracellular brain levels of adenosine in Tg controls, caffeine treatment normalized brain adenosine levels in Tg mice to that of non-transgenic controls. Analysis of amyloidogenic secretase activity revealed the reduction in Αβ is likely because of a reduction in gamma secretase activity as a result of increased SAM silencing of PS1 expression. This study suggest that a modest, long-term caffeine intake of approximately 500 mg per day (5 cups of coffee) may reduce considerably the risk of AD by decreasing amyloidogenesis.

Alzheimer's disease (AD) is characterized by anterograde amnesia followed by a progressive decline in cognitive function. Post mortem examination of forebrain tissue from sufferers reveals the presence of extracellular amyloid-beta plaques, intracellular neurofibrillary tangles, activation of glial cells and massive neuron loss. Transgenic mice expressing mutated forms of the amyloid precursor protein (APP) and presenilin-1 (PS1) genes develop neuritic amyloid plaques, glial cell activation and memory deficits, without the formation of intracellular tangles and neurodegeneration. The mechanisms by which these transgenic mice develop mnemonic deficiencies are unclear. Gene expression of aged memory-deficient APP+PS1 mice compared with non-transgenic littermates measured by microarray and subsequent quantitative real-time PCR (qRT-PCR) analysis revealed 6 inducible immediated-early genes (IEGs) and 5 other more stably expressed plasticity-related genes (PRGs) that were significantly down-regulated in amyloid-containing hippocampus, but not down-regulated in amyloid-free cerebellum. Other genes linked to memory remained stably expressed in both regions. Analysis of forebrain AD tissue revealed that all genes measured were down-regulated presumably due to neurodegeneration, while the amyloid-free region maintained stable expression. IEG expression in APP+PS1 mice was sensitive to lower levels of amyloid. However, only in the presence of a substantially larger amyloid burden, when memory deficits reliably persist, were both PRGs and IEGs down-regulated. Importantly, we found that IEG expression was decreased in APP+PS1 mice following exposure to a novel environment, indicating that the induction of these IEGs was impaired, rather than the basal expression of resting mice. Na+/K+ ATPase, an enzyme critical for the maintenance of membrane potential, was identified as a down-regulated PRG. We found that activity of this enzyme was both impaired in the hippocampi of APP+PS1 mice and specifically inhibited by high concentrations of amyloid-beta. Na+/K+ ATPase immunostaining revealed decreased protein in the area surrounding the amyloid plaque, where dystrophic neurites were visible, indicating amyloid may disrupt ionic gradients resulting in neuritic dystrophia. These findings suggest that amyloid accumulation may result in the impairment of IEG induction and disruption of the Na+/K+ ATPase, possibly eliciting the memory loss developed in APP+PS1 mice.

Mild Cognitive Impairment is a condition that affects an individual's thinking and decision making capabilities. Specifically, it is one where an individual's capabilities of memorizing, thinking and decision making are less efficient when compared to others. In order to diagnose this condition, a conventional method is to provide the subject with a small challenge they should be completed using pen and paper. This thesis focuses on how this method can be converted to a computer based test. A data visualization tool named Processing has been used to develop a system that runs a game-like test, which is completed by individuals using a mouse. The system then saves the individual's mouse movements in the form of a CSV file. This files are used for further analyzed using JMP Pro on how this data can be used for determining cognitive abilities via computing a metric called Fractal, and what conclusions can be drawn. In order to achieve comparable results, readings from two diverse age groups have been collected. The results using a total of 12 subjects are convincing in that the tool can be used to as a marker for detecting cognitive impairment.

Peptidomimetics are synthetic oligomers that resemble the activities of peptides. Their advantages over peptides include high stability towards proteolysis and enormous chemical diversity. Over the past two decades, there have been extensive efforts to develop peptide mimics, such as beta-peptides, peptoids, D-peptides, etc. The research on peptidomimetics have led to many important applications in both medicinal and material science. In order to explore new functions, the discovery of peptidomimetics with novel frameworks is essential. We reported the synthesis and evaluation of a new class of peptidomimetics, termed as gamma-AApeptides. Previous studies of gamma-AApeptides have revealed that gamma-AApeptides are highly resistant to proteolysis, and are highly amendable to chemical diversification. However, new biological activities and folding properties of gamma-AApeptides still need to be explored. In order to expand the potential of gamma-AApeptides in chemical biology and medicinal chemistry, I have been focusing on the development of new methods to synthesize linear and cyclic gamma-AApeptides, development of one-bead-one-compound (OBOC) gamma-AApeptide libraries for the discovery of inhibitors against beta-amyloid aggregation, exploring new helical foldamers for the rational design of protein-protein interaction (PPI) inhibitors, and studying cyclic gamma-AApeptides for antimicrobial development.

Le repliement et la stabilité des protéines dépendent des conditions physico-chimiques de leur environnement. En particulier, le pH, la température, l’agitation et les interactions avec d’autres macromolécules ou avec les interfaces (liquide–surfaces des matériaux ; air-liquide ; etc.) sont connues pour induire des phénomènes de dénaturation et d’agrégation des protéines.Le contrôle de la stabilité des protéines thérapeutiques représente un enjeu médical et économique pour l’industrie pharmaceutique. L’insuline, qui est la protéine thérapeutique la plus produite, est connue in vitro pour former des fibres amyloïdes induites par les surfaces hydrophobes. Les agrégations amyloïdes sont également impliquées dans un certain nombre de pathologies, notamment humaines et animales présentant de forts enjeux de santé publique et économiques.Cette thèse traite en particulier de l’agrégation amyloïde à la surface des matériaux en utilisant l’insuline comme protéine modèle. Les travaux précédents réalisés par notre équipe ont démontré que des peptides de courte longueur avaient la capacité de modifier très significativement la cinétique d’agrégation induite par la surface des matériaux, et ce à des concentrations sub-stœchiométriques par rapport à l'insuline. En particulier les peptides adoptant une conformation secondaire en feuillet beta une fois adsorbés sur les surfaces hydrophobes, induisent une réduction drastique de la durée de nucléation de fibres amyloïdes d’insuline.Dans les travaux présentés ici nous avons découvert des séquences peptidiques présentant, toujours à des concentrations sub-stœchiométriques, deux effets antagonistes sur la cinétique de l’agrégation amyloïde de l’insuline. Le premier effet, coopératif et localisé à la surface de matériaux hydrophobes, résulte en une accélération de la nucléation. A l’inverse le second effet provient des peptides en solution et résulte en une puissante inhibition à la fois de la nucléation et de l’élongation des fibres.Nous avons premièrement caractérisé quantitativement ces effets pour un ensemble de peptides possédant des séquences de type (LK)nL, et investigué les mécanismes à l’origine du phénomène accélérateur. Des mesures quantitatives de fluorescence (Thioflavine T, marquage fluorescent du peptide) ont permis de montrer que l’adsorption coopérative des peptides sur la surface du matériau était responsable de l’accélération de la vitesse de nucléation. Pour l’effet inhibiteur, provenant des peptides en solution, nous avons démontré que cet effet résulte de la liaison des peptides sur l’insuline fibrillaire et qu’il est médié par les charge.De surcroit nous avons étudié la localisation de la nucléation et de l’apparition des premiers agrégats par microscopie à fluorescence. Nous avons observé que les zones situées à l’interface triple matériau-air-solution et subissant une contrainte de cisaillement élevé étaient les sites préférentiels d’apparition des premiers agrégats amyloïdes et donc très probablement les régions dominantes en termes de nucléation.Nous avons enfin développé une technique permettant une croissance localisée, patternable et induite par la lumière d’agrégats amyloïde d’insuline sur une surface de verre. Cette voie d’agrégation singulière ne présente pas de phase de nucléation apparente et dépend strictement de la présence de Thioflavine T. Nous avons montré que la Thioflavine T insérée entre les feuillets béta et qui peut être excitée à 440 nm fournit localement l’énergie nécessaire pour la transition de conformation de l’insuline native adsorbée vers l’état agrégé. Cette méthode permet d’obtenir une croissance différentielle entre des zones de surface hydrophile et hydrophobe. / The folding and stability of proteins depend on the physico-chemical conditions of their environment. Especially pH, temperature, stirring and interactions with other macromolecules or with interfaces (liquid-material surfaces; air-liquid; etc.) are known to induce protein denaturation and aggregation phenomena.The control of therapeutic protein stability represents a medical and economic challenge for the pharmaceutic industry. For instance insulin, which is the most s model produced therapeutic protein, is known to form amyloid aggregates in vitro induced by hydrophobic surfaces. Amyloid aggregates are also involved in several pathologies including human and animal diseases of high economic and public health impact.This thesis focuses on amyloid aggregation at material surfaces using insulin as a model protein. Previous work from our team have demonstrated that short peptides have the ability to significantly interfere with the kinetics of surface-driven amyloid aggregation and this at sub-stoichiometric concentrations with respect to insulin. In particular peptides adopting a beta-sheet secondary structure when adsorbed on hydrophobic surfaces, were able to reduce the nucleation time of insulin aggregation.In the present work we have discovered peptide sequences presenting, again at sub-stoichiometric concentrations, two antagonistic effects on insulin aggregation kinetics. The first consists in a cooperative reduction of the nucleation time and operates via peptides bound to the material surface. The second, on the other hand, results in a powerful inhibition of both nucleation and fiber elongation via peptides remaining in solution.We have first quantitatively characterized these effects on a set of peptides presenting alternate primary sequences of the type (LK)nL, and investigated the underlying mechanisms promoting insulin nucleation. Quantitative fluorescence measurements (Thioflavin T, fluorescent labelling of the peptide) have shown that the cooperative adsorption of peptides on hydrophobic material surfaces was responsible for the reduction of the insulin nucleation time. We have then shown that the inhibitory effect results from the binding of peptides in solution to fibrillar insulin aggregates and that this effect is mediated by charges.In addition we studied the localization of the insulin nucleation and of the appearance of the first aggregates using fluorescence microscopy. We observed the preferential appearance of the first ThT positive aggregates at the solid-liquid-air triple interface undergoing high shear stress, making these regions the predominant nucleation sites.We eventually developed a technique allowing a localized and patterned growth of light-induced insulin aggregates on glass surfaces. This atypical aggregation pathway does not present any observable lag time and depends strictly on Thioflavin T. We have shown that the ThT inserted between the cross beta-sheets and which can be excited at 440 nm locally provides the energy required for the conformational transition of the native insulin into the aggregated one. This method can be used to obtain a differential amyloid growth between surface area of different hydrophobicity.

Structural and mechanistic complexities of copper-dioxygen systems have attracted much attention in the field of bioinorganic chemistry, both in model systems and trapped protein intermediates. The research presented herein is focused on model and naturally occurring metallopeptide systems, from its design to catalysis. Copper is used as the coordinating metal ion, with cobalt and zinc as probes for metal binding. The bioinorganic chemistry of copper proteins and its coordination and spectroscopic properties are briefly discussed in chapter 1. The next two chapters are centered on the de novo design of a minimalistic metallopeptide system with an amino acid sequence of RHHPPHHE. Structural characterization of the peptide by means of CD and NMR spectroscopy techniques are presented in chapter 2, suggesting a characteristic beta-turn structure in its apo and di-metal bound form. The designed metallopeptide exhibits catecholase activity, which is presented in chapter 3. The data suggest the presence of two mononuclear copper active sites, exhibiting specificity towards the oxidation of catecholamine substrates. Similarly, the catecholase activity has been previously observed in copper complexes of Alzheimer's disease related peptide beta-amyloid, exhibiting metal-centered redox chemistry. The metallo-(beta-amyloid); complexes are the hallmark Alzheimer's disease and have been attributed to the generation of reactive oxygen species causing oxidative stress. Thus, inhibition of the observed oxidative activities was investigated. Probing the role of phosphate moieties in various compounds as potential inhibitors against the induced oxidative stress is presented in chapter 4. The phosphate analogs of the studied compounds exhibit more pronounced potency, where mutation of the beta amyloid peptide at Arg-5 and Lys-16 give insight into the interactions of the side chains of Arg and Lys with the phosphate moiety. 31P NMR relaxation studies further support the binding/interaction of phosphate with the Cu(II)-(beta-amyloid); complexes. The correlation of phosphate moiety binding/activity will allow for the design of more potent inhibitors toward the Cu(II)-(beta-amyloid); induced oxidative stress.