γ-Secretase plays a pivotal role in the production of neurotoxic amyloid β-peptide (Aβ), the principal component of amyloid plaques present in Alzheimer’s disease. It consists of a core complex of presenilin (PS), nicastrin, anterior pharynx-defective 1 (Aph-1), and presenilin enhancer 2 (Pen-2) proteins. PS harbors the catalytic aspartates required for regulated intramembrane proteolysis and the paralogs (PS1 and PS2) contribute to the assembly of distinct subpopulations of γ-secretases that may fulfill distinct roles. To characterize the molecular environments of distinct γ-secretases complexes in-depth quantitative comparisons were performed on 1) wild-type PS1 and its derivative carrying point mutations known to cause heritable early-onset AD in mice, and 2) PS1- or PS2-containing γ-secretase complexes equipped with N-terminal tandem-affinity purification (TAP) tags on PS paralogs in HEK293 cells. Isobaric labeling of co-purifying peptides for quantitative mass spectrometry revealed that γ-secretase complexes interact with other protein networks, including the cellular catenin-cadherin network, the molecular machinery that targets and fuses synaptic vesicles to cellular membranes, and the H+-transporting lysosomal ATPase macro-complex. The study revealed mature γ-secretase complexes containing PS1 or mutant PS1 to be indistinguishable in their protein composition, confirmed several previously proposed γ-secretase interactors, identified many novel interactors and uncovered a subset of proteins which can engage in robust interactions with γ-secretase complexes in individual cell types but may escape detection when whole brains are used as biological source materials. Interestingly, signal peptide peptidase (SPP), a Type II TM cleaving aspartyl protease, was pre-dominantly found to co-purify with PS2-containing γ-secretase complexes and could be shown not to influence their maturation but to affect cleavage or release of cellular Aβ. A model emerged from this work that suggests PS1 and PS2 paralogs may divide up the task of handling a broad range of membrane stubs at least in part by associating with different molecular environments.

L’étude des interactions moléculaires au niveau des membranes biologiques est un enjeu capital pour le développement et le screening de nouvelles molécules médicamenteuses. La MA est la forme de démence sénile la plus répandue dans le monde et représente le principal problème socioéconomique en matière de soins de santé. L'apparition et la progression de cette maladie neurodégénérative sont associées à l'agrégation du peptide Aβ.Une stratégie thérapeutique contre la MA consiste à développer des molécules capables d'interférer à des étapes spécifiques de l’agrégation du peptide. Pour les identifier, des méthodes expérimentales sont nécessaires pour suivre et caractériser le peptide Aβ au cours de son processus de fibrillation. Ces méthodes doivent être suffisamment simples pour rester compatibles avec une démarche de drug discovery. Dans le présent travail de thèse, nous avons proposé de combiner des méthodes expérimentales pour permettre une caractérisation multiparamétrique de modulateurs potentiels de la fibrillation du peptide Aβ1-42, en y intégrant des liposomes de composition définie, comme membranes neuronales biomimétiques. Il est en effet établi que les lipides neuronaux sont un facteur important dans la formation des fibres amyloïdes et leur toxicité. Les liposomes ont été formulés par la méthode de réhydratation de film lipidique, et leurs propriétés physico-chimiques caractérisées par RMN, DLS, potentiel ζ.La détermination expérimentale du coefficient de partage de composés d’intérêt a pu être réalisée par spectrophotométrie, y compris de façon originale, par fluorescence, en utilisant ces liposomes, dans des tests miniaturisés. Des études cinétiques de l’agrégation du peptide Aβ1-42 ont été effectuées en présence de liposomes. La fluorescence de la ThT a été mesurée pour suivre la voie de la fibrillation du peptide Aβ, utilisé dans sa forme sauvage ou celle d’un mutant oligomérique, l’oG37C. Une analyse de fuite d’un fluorophore à partir des liposomes, appuyée par des mesures en DLS, a été réalisée afin d'évaluer l'impact des interactions entre le peptide et les membranes pour prévoir tout effet de déstabilisation. Les fibres toxiques formées par Aβ étant principalement organisées en feuillets β, les données ont été corrélées à l'analyse de la structure secondaire du peptide par spectroscopie ATR-FTIR. Après avoir mis en œuvre cette approche sur différentes molécules modèles et un hit d’intérêt potentiel dans le traitement de la MA, l’ensemble de ce travail a abouti à un test multiparamétrique permettant la caractérisation de l’interactome molécules/Aβ/membranes et la discrimination de modulateurs de l'agrégation du peptide Aβ1-42. Cette approche pourra être avantageusement transposée à d'autres maladies amyloïdes. / The study of molecular interactions at the level of biological membranes is a key issue for the screening and the development of new drugs. Alzheimer's disease (AD) is the most common form of senile dementia in the world and is the leading socio-economic problem in health care. The appearance and progression of this neurodegenerative disease are associated with the aggregation of the amyloid-β peptide (Aβ). A therapeutic strategy against AD consists in the development of molecules able to interfere with specific steps of Aβ aggregation. To identify such compounds, experimental methods are required to monitor and characterize the Aβ peptide during its fibrillation process. These methods must be simple enough to remain compatible with drug discovery. In this PhD project, we have proposed to combine experimental methods to allow a multiparametric characterization of potential Aβ1-42 fibrillation modulators, by integrating liposomes of defined composition as biomimetic neuronal membranes. It is indeed established that neuronal lipids are an important factor in the formation of amyloid fibers and their toxicity. The liposomes were formulated by the lipid film rehydration method, and their physicochemical properties characterized by NMR, DLS, ζ potential. The experimental determination of the compounds partition coefficient could be carried out by spectrophotometry, including in an original way, by fluorescence, these liposomes, in miniaturized tests. Kinetic studies of Aβ1-42 peptide aggregation were performed in the presence of liposomes.The ThT fluorescence was monitored to follow the Aβ peptide fibrillation pathway, used in its wild form or with an oligomeric mutant, oG37C. A fluorophore leakage analysis from liposomes, supported by DLS measurements, was performed to evaluate the impact of peptide/membranes interactions to predict any destabilization effects. The toxic fibers formed by Aβ being mainly organized in β-sheets, the data were correlated with the analysis of the peptide secondary structure by ATR-FTIR spectroscopy. After the implementation of this approach on different model molecules and a hit of potential interest in the AD treatment, all of this work has resulted in a multiparametric test allowing the molecules/Aβ/membranes interactome characterization and the discrimination of Aβ1-42 peptide aggregation modulators. This approach may be advantageously transposed to other amyloid diseases.

In certain neurodegenerative diseases such Dementia with Lewy Bodies (DLB), it is hypothesised that misfolded α-synuclein (α-syn) and β-amyloid both contribute to pathology. α-Syn and β-amyloid have been suggested to synergistically promote one another’s accumulation and aggregation, but the mechanisms are unknown. β-Amyloid is generated from β-/γ-secretase-mediated processing of the amyloid precursor protein (APP). This study investigated how α-syn overexpression in cells affects β-amyloid production from APP, using multiplex assays, luciferase reporter assays, and western blotting. Wildtype α-syn expression induces β-amyloid generation from APP in SH-SY5Y human neuroblastoma cells, and similar changes to APP processing occur in another neuronal cell model. Dominant-negative overexpression of α-syn mutants revealed that disrupting the N-terminal domain can increase APP amyloidogenic processing. Secretase enzymes that perform APP processing were next investigated. γ-Secretase activity, measured by a luciferase reporter, was not increased by α-syn overexpression. A higher ratio of β- to α-secretase processing was hypothesised, which led to expression and activity studies of the major β- and α-secretases, BACE1 and ADAM10 respectively. It was shown that the BACE1 protein expression is post-transcriptionally upregulated in α-syn cells, with increased APP cleavage in cells. ADAM10 protein expression is transcriptionally suppressed in wild-type α-syn cells, reducing total levels of catalytically active enzyme. However the change in ADAM10-mediated APP processing may be negligible since, critically, plasma membrane expression of ADAM10 appears to be maintained. To aid understanding of the mechanism that connects α-syn to APP processing, BACE1 expression was used in pharmacological studies of cell stress signalling. This approach revealed that in α-syn cells BACE1 lysosomal and/or proteasomal degradation may be disturbed. Additionally, BACE1 expression is induced by translational de-repression mediated by eIF2α ser-51 phosphorylation, which was increased in α-syn cells. Although preliminary, the data suggests a role for oxidative stress mediating the increased BACE1 expression in wild-type α-syn cells.

This thesis describes generation and characterization of Affibody molecules with future applications in proteomics research, protein structure determinations, therapeutic treatment of disease and medical imaging for in vivo diagnostics. Affibody molecules are engineered affinity proteins developed by combinatorial protein engineering from the 58-residue protein A-derived Z domain scaffold. Novel Affibody molecules targeting human proteins were selected from a combinatorial library using phage display technology. In the first two investigations, an Affibody molecule specifically targeting the high abundant human serum protein transferrin was generated. The intended future use of this Affibody ligand would be as capture ligand for depletion of transferrin from human samples in proteomics analysis. Strong and highly specific transferrin binding of the selected Affibody molecule was demonstrated by biosensor technology, dot blot analysis and affinity chromatography. Efficient Affibody-mediated depletion of transferrin in human plasma and cerebrospinal fluid (CSF) was demonstrated in combination with IgG and HSA removal. Furthermore, depletion of five high abundant proteins including transferrin from human CSF gave enhanced identification of proteins in a shotgun proteomics analysis. Two studies involved the selection and characterization of Affibody molecules recognizing Alzheimer’s amyloid beta (Abeta) peptides. Future prospect for the affinity ligands would primarily be for therapeutic applications in treatment of Alzheimer’s disease. The developed A-binding Affibody molecules were found to specifically bind to non-aggregated forms of Abeta and to be capable of efficiently and selectively capture Abeta peptides from spiked human serum. Interestingly, the Abeta-binding Affibody ligands were found to bind much better to Abeta as dimeric constructs, and with impressive affinity as cysteine-bridged dimers (KD~17 nM). NMR spectroscopy studies revealed that the original helix one, of the two Affibody molecules moieties of the cysteine-bridged dimers, was unfolded upon binding, forming intermolecular β-sheets that stabilized the Abeta peptide, enabling a high resolution structure of the peptide. Furthermore, the Abeta-binding Affibody molecules were found to inhibit Abeta fibrillation in vitro. In the last study, Affibody molecules directed to the interleukin 2 (IL-2) receptor alpha (CD25) were generated. CD25-binding Affibody molecules could potentially have a future use in medical imaging of inflammation, and possibly in therapeutic treatment of disease conditions with CD25 overexpression. The selected Affibody molecules were demonstrated to bind specifically to human CD25 with an apparent affinity of 130-240 nM. Moreover, the CD25-targeting Affibody molecules were found to have overlapping binding sites with the natural ligand IL-2 and an IL-2 blocking monoclonal antibody. Furthermore, the Affibody molecules demonstrated selective binding to CD25 expressing cells. / QC 20100729

One of the largest problems in current medicine is the shortage of organs for transplant due to technological limitations in the storage of organs for any length of time. A possible solution to this problem would involve cryopreservation. However, current cryopreservatives such as sucrose or DMSO have concerning cytotoxic issues that limit their possible applications. A major cause of cryoinjury is the uncontrolled recrystallization of inter and intra-cellular ice crystals that occurs during the thawing process leading to mechanical damage and dehydration. The Ben lab has thus been interested in the design of compounds that are capable of inhibiting this process but do not possess other undesirable properties found in the native compounds. These synthetic analogues have been shown to increase cellular viability post-thaw. A series of mixed α/β glycopeptides are prepared and analyzed for antifreeze properties. The results of this study imply that it is not the gross conformation of the glycopeptide that is responsible for activity, but rather that intramolecular relationships may be responsible for disrupting the reorganization of ice. A technique was devised for the incorporation of triazoles into the analogues to investigate the importance of the linker and to greatly simplify the synthesis of a library of glycoconjugates. It was found that the IRI activity of glycopeptides is very sensitive to the distance between carbohydrate and peptide backbone. The electron density at the anomeric oxygen is an important parameter with respect to intramolecular networks. A series of substituted galactosides is presented that modify the electronics of the anomeric oxygen. The results demonstrate that decreasing electron density at this position appears to improve IRI activity in a predictable manner. To better understand the remarkable IRI activity of a key analogue, it was systematically truncated. This study led to the serendipitous discovery of a series of very highly IRI active analogues that do not contain a peptide backbone. These compounds represent the first non-glycopeptides that can show very significant IRI activity even at very low concentrations. The final portion of the thesis reports the efforts towards the preparation of a carbasugar analogue of AFGP-8.

One of the largest problems in current medicine is the shortage of organs for transplant due to technological limitations in the storage of organs for any length of time. A possible solution to this problem would involve cryopreservation. However, current cryopreservatives such as sucrose or DMSO have concerning cytotoxic issues that limit their possible applications. A major cause of cryoinjury is the uncontrolled recrystallization of inter and intra-cellular ice crystals that occurs during the thawing process leading to mechanical damage and dehydration. The Ben lab has thus been interested in the design of compounds that are capable of inhibiting this process but do not possess other undesirable properties found in the native compounds. These synthetic analogues have been shown to increase cellular viability post-thaw. A series of mixed α/β glycopeptides are prepared and analyzed for antifreeze properties. The results of this study imply that it is not the gross conformation of the glycopeptide that is responsible for activity, but rather that intramolecular relationships may be responsible for disrupting the reorganization of ice. A technique was devised for the incorporation of triazoles into the analogues to investigate the importance of the linker and to greatly simplify the synthesis of a library of glycoconjugates. It was found that the IRI activity of glycopeptides is very sensitive to the distance between carbohydrate and peptide backbone. The electron density at the anomeric oxygen is an important parameter with respect to intramolecular networks. A series of substituted galactosides is presented that modify the electronics of the anomeric oxygen. The results demonstrate that decreasing electron density at this position appears to improve IRI activity in a predictable manner. To better understand the remarkable IRI activity of a key analogue, it was systematically truncated. This study led to the serendipitous discovery of a series of very highly IRI active analogues that do not contain a peptide backbone. These compounds represent the first non-glycopeptides that can show very significant IRI activity even at very low concentrations. The final portion of the thesis reports the efforts towards the preparation of a carbasugar analogue of AFGP-8.

One of the largest problems in current medicine is the shortage of organs for transplant due to technological limitations in the storage of organs for any length of time. A possible solution to this problem would involve cryopreservation. However, current cryopreservatives such as sucrose or DMSO have concerning cytotoxic issues that limit their possible applications. A major cause of cryoinjury is the uncontrolled recrystallization of inter and intra-cellular ice crystals that occurs during the thawing process leading to mechanical damage and dehydration. The Ben lab has thus been interested in the design of compounds that are capable of inhibiting this process but do not possess other undesirable properties found in the native compounds. These synthetic analogues have been shown to increase cellular viability post-thaw. A series of mixed α/β glycopeptides are prepared and analyzed for antifreeze properties. The results of this study imply that it is not the gross conformation of the glycopeptide that is responsible for activity, but rather that intramolecular relationships may be responsible for disrupting the reorganization of ice. A technique was devised for the incorporation of triazoles into the analogues to investigate the importance of the linker and to greatly simplify the synthesis of a library of glycoconjugates. It was found that the IRI activity of glycopeptides is very sensitive to the distance between carbohydrate and peptide backbone. The electron density at the anomeric oxygen is an important parameter with respect to intramolecular networks. A series of substituted galactosides is presented that modify the electronics of the anomeric oxygen. The results demonstrate that decreasing electron density at this position appears to improve IRI activity in a predictable manner. To better understand the remarkable IRI activity of a key analogue, it was systematically truncated. This study led to the serendipitous discovery of a series of very highly IRI active analogues that do not contain a peptide backbone. These compounds represent the first non-glycopeptides that can show very significant IRI activity even at very low concentrations. The final portion of the thesis reports the efforts towards the preparation of a carbasugar analogue of AFGP-8.

La maladie d’Alzheimer (MA) constitue la forme la plus commune de démence associée à une perte de mémoire et caractérisée par l’accumulation de plaques extracellulaires contenant des peptides bêta-amyloïdes (Aβ). Des études ont révélé une perte plus importante de synapses que ne peut l’expliquer la mort neuronale, suggérant qu’un déficit synaptique serait présent dès les stades initiaux de la maladie. Bien que le peptide Aβ fût identifié comme un composé des plaques amyloïdes extracellulaires dans les années 1980, des études plus récentes ont mis en évidence la présence intracellulaire de ce peptide. L’accumulation d’Aβ intracellulaire serait un événement antérieur à la formation des plaques séniles dans la pathogenèse de la MA et corrèlerait mieux avec les perturbations de mémoire et d’apprentissage caractéristiques de cette maladie. De plus, des données mettent en évidence la responsabilité des formes oligomériques solubles d’Aβ (Aβo) dans les évènements précoces de la MA. Ce projet vise à mieux comprendre et caractériser l’impact extracellulaire et intracellulaire des peptides Aβo et le lien fonctionnel de leurs effets sur les mécanismes moléculaires impliqués dans les processus mnésiques affectés dans la maladie d’Alzheimer. Dans ce contexte, il nous a paru essentiel d’étudier l’impact extracellulaire et intracellulaire des oligomères d’Aβ sur la transmission synaptique. Ces travaux ont été effectués sur culture primaire de neurones corticaux et sur tranche de cortex de souris par des méthodes d’électrophysiologie via la technique de patch-clamp.Nous avons analysé la fréquence et l’amplitude des courants post-synaptiques excitateurs spontanés (sEPSC) des principaux récepteurs impliqués dans la transmission glutamatergique et dans les mécanismes moléculaires à la base de la mémoire et de l’apprentissage : les récepteurs AMPA et NMDA. Nos données montrent que les peptides Aβo dans le milieu extracellulaire (eAβo) ou dans le milieu intracellulaire (iAβo), affectent spécifiquement les courants associés à l’activation des récepteurs NMDA au niveau postsynaptique sans altérer les courants AMPA. L’application dans le milieu extracellulaire d’Aβo réduit l’amplitude des courants NMDA. Ce phénomène n’est pas lié à la pénétration du peptide Aβo dans les neurones mais à l’activation par l’Aβo de la voie amyloïdogénique induisant une accumulation intrasynaptique d’Aβo responsable de la réduction des courants NMDA.L’ensemble de ces données suggère que l’Aβo perturbe le processing d’APP menant à une production intracellulaire d’Aβo responsable de la réduction de la transmission glutamatergique NMDA-dépendante. Une étape essentielle afin d’améliorer la compréhension des mécanismes moléculaires qui sont à la base des altérations synaptiques glutamatergiques dans la MA est d’approfondir le lien fonctionnel entre les effets extracellulaire et intracellulaire des peptides Aβo. / Alzheimer’s disease (AD) is the most common form of dementia associated with memory loss and characterized by an accumulation of extracellular plaques composed of amyloid-beta peptides (Aβ). Studies have revealed a greater loss of synapses than the neuronal death can explain, suggesting that a synaptic deficit would be present from the early stages of the disease. Although the Aβ peptide has been identified as a component of the extracellular amyloid plaques in the 1980s, recent studies have highlighted the intracellular presence of this peptide. The intracellular accumulation of Aβ precedes the appearance of amyloid plaques in the pathogenesis of AD and seems to be correlated with the memory and learning troubles, characteristic of this disease. Moreover, some data highlight the responsibility of the soluble oligomeric Aβ form (Aβo) in the early events of AD. This project aims to better understand and characterize the extracellular and intracellular impact of Aβo peptides and the functional link of their effects on the molecular mechanisms involved in memory processes affected in AD. In this context, it was essential to study the extracellular and intracellular impact of Aβ oligomers on synaptic transmission. This work was carried out on cultures of primary cortical neurons and mouse cortex slices using electrophysiological methods via the patch-clamp technique.We have recorded the spontaneous excitatory postsynaptic currents (sEPSC) frequency and amplitude from the main receptors implicated in the glutamatergic transmission and in the molecular mechanisms underlying memory and learning processes: AMPA and NMDA receptors. Our data show that external or internal application of Aβo peptides affect specifically the currents associated with NMDA receptors at a postsynaptic level without altering the AMPA currents. The external application of Aβo reduces the NMDA current amplitude. This phenomenon is not due to the penetration of the Aβo peptide into the neurons but rather to the activation of the amyloïdogenic pathway by Aβo inducing an intracellular accumulation of Aβo responsible of the NMDA current reduction.All these data suggest that Aβo perturb the processing of APP leading to an intracellular Aβo production responsible of the glutamatergic NMDA-dependent transmission reduction. An essential step in order to improve our understanding of the molecular mechanisms underlying the altered glutamatergic synaptic alterations found in AD is to deepen the functional link between the extracellular and intracellular effects of the Aβo peptides.

One of the largest problems in current medicine is the shortage of organs for transplant due to technological limitations in the storage of organs for any length of time. A possible solution to this problem would involve cryopreservation. However, current cryopreservatives such as sucrose or DMSO have concerning cytotoxic issues that limit their possible applications. A major cause of cryoinjury is the uncontrolled recrystallization of inter and intra-cellular ice crystals that occurs during the thawing process leading to mechanical damage and dehydration. The Ben lab has thus been interested in the design of compounds that are capable of inhibiting this process but do not possess other undesirable properties found in the native compounds. These synthetic analogues have been shown to increase cellular viability post-thaw. A series of mixed α/β glycopeptides are prepared and analyzed for antifreeze properties. The results of this study imply that it is not the gross conformation of the glycopeptide that is responsible for activity, but rather that intramolecular relationships may be responsible for disrupting the reorganization of ice. A technique was devised for the incorporation of triazoles into the analogues to investigate the importance of the linker and to greatly simplify the synthesis of a library of glycoconjugates. It was found that the IRI activity of glycopeptides is very sensitive to the distance between carbohydrate and peptide backbone. The electron density at the anomeric oxygen is an important parameter with respect to intramolecular networks. A series of substituted galactosides is presented that modify the electronics of the anomeric oxygen. The results demonstrate that decreasing electron density at this position appears to improve IRI activity in a predictable manner. To better understand the remarkable IRI activity of a key analogue, it was systematically truncated. This study led to the serendipitous discovery of a series of very highly IRI active analogues that do not contain a peptide backbone. These compounds represent the first non-glycopeptides that can show very significant IRI activity even at very low concentrations. The final portion of the thesis reports the efforts towards the preparation of a carbasugar analogue of AFGP-8.

La maladie d'Alzheimer est caractérisée par la présence de dégénérescences neurofibrillaires et l'accumulation de plaques amyloïdes dans le cerveau. Ces plaques contiennent principalement un peptide nommé amyloïde-β (Aβ) sous forme agrégée. Le processus d'agrégation des peptides Aβ en plaques amyloïdes représente une étape clé dans l'apparition de la pathologie, la coordination du cuivre, et également du zinc, favorisant la formation d'espèces agrégées impliquées dans la neurotoxicité. Notre objectif consiste à concevoir des complexes bifonctionnels avec d'une part un analogue de la Thioflavine T (ThT) et d'autre part un complexe de Ru(II), ce travail de thèse s'articule donc selon ces deux axes. I- Nous nous sommes d'abord intéressés à l'interaction entre le peptide Aβ et la Thioflavine T (ThT), fluorophore classiquement utilisé pour étudier l'agrégation du peptide Aβ. Cette interaction a été étudiée principalement par spectroscopie RMN. Les résultats obtenus ont permis d'identifier le site d'interaction de la ThT au peptide Aβ. Par la suite, les effets de la ThT et du Zn(II) sur l'agrégation du peptide Aβ ont été évalués en combinant la RMN et la spectroscopie de fluorescence. A partir des données obtenues, nous avons montré que la ThT et le Zn(II) ne sont pas inertes sur la cinétique d'agrégation du peptide Aβ. Les résultats ont également révélé des différences importantes concernant les informations apportées par la fluorescence et la RMN. II- La coordination du cuivre et du zinc implique principalement les noyaux imidazoles des résidus histidines. Afin d'empêcher la coordination de ces ions métalliques aux peptides Aβ, une stratégie thérapeutique innovante consiste en l'utilisation de complexes platinoïdes comportant des sites labiles et capables de se lier aux résidus histidines du Aβ. En raison de la toxicité des complexes de Pt(II), nous avons envisagé la synthèse de complexes de Ru(II), principalement basés sur le motif fac-Ru(CO)32+. Différents complexes avec des ligands de type glycinate, hydroxyquinolinate et éthylenediamine ont été synthétisés. L'étude de leur interaction avec le peptide Aβ a été réalisée par différentes techniques spectroscopiques (RMN, RPE, fluorescence, spectrométrie de masse). Les résultats obtenus ont montré, en particulier, que les complexes sont capables d'inhiber l'agrégation du peptide Aβ induite par le zinc. / The Alzheimer's disease is characterized by the presence of neurofibrillary tangles and amyloid plaques in the brain. These plaques are formed by aggregated amyloid-β (Aβ) peptide. The Aβ aggregation represents a key event in the appearance of the pathology, copper and zinc coordination favoring the formation of aggregated species involved in the neurotoxicity. Our objective consists in designing bifonctional complexes with, on one hand, a Thioflavine T (ThT) analog and, on the other hand, a Ru(II) complex : this thesis is thus centered around these two axes. I- In this context, we first investigated the interaction between Aβ and ThT, which is a classical dye commonly used to study the aggregation process. This interaction was mainly studied by NMR spectroscopy. Our first results allowed us to identify the interaction site of the ThT with the Aβ peptide. Then, the ThT and Zn(II) effects on the aggregation process were assessed by NMR and fluorescence spectroscopy. From the obtained data, we showed that ThT and Zn (II) are involved in the aggregation kinetic. The results also revealed important differences concerning the information brought by fluorescence and NMR. II- Copper and zinc coordination mainly implies imidazole ring of the histidine residues. In order to prevent the coordination of these metallic ions to Aβ, an innovative therapeutic strategy consists of the use of platinoid complexes containing labile sites which are able to bind the Aβ histidine residues. Because of Pt(II) complexes toxicity, we envisaged the synthesis of Ru(II) complexes, mainly based on fac-Ru(CO)32+ motive. Different complexes with glycinate, hydroxyquinolinate or ethylenediamine ligand were synthesized. The study of their interaction with the Aβ peptide was realized by various spectroscopy techniques (RMN, RPE, fluorescence, mass spectrometry and demonstrated that the complexes are able to prevent the Aβ aggregation induced by zinc.