O carrapato bovino, Rhipicephalus (Boophilus) microplus, é um artrópode hematófago, responsável por importantes perdas na pecuária. Durante o desenvolvimento do embrionário do carrapato a cisteíno endopeptidase degradadora de vitelina (VTDCE) participa do processo de hidrólise de vitelina (Vt), a principal fonte de energia e aminoácidos durante esse período. Devido à sua importância na fisiologia do parasita, a VTDCE é um alvo potencial para o desenvolvimento de vacinas anti-carrapatos. Estudos anteriores demonstraram que a VTDCE nativa, purificada de ovos confere proteção contra R. microplus, desencadeada pela resposta imune dos bovinos após a administração deste antígeno. Entretanto, o extenso e dispendioso processo de purificação desta proteína, acrescido do baixo rendimento e fonte escassa de material (ovos de carrapato) inviabiliza a utilização da proteína nativa para fins comerciais. Tais dificuldades podem ser ultrapassadas por meio do uso de uma proteína recombinante. O presente trabalho tem por objetivo a expressão, purificação e caracterização da VTDCE recombinante (rVTDCE). Parte da sequência de aminoácidos da VTDCE nativa foi obtida por sequenciamento de edman e pela análise por especrometria de massas de petídeos obtidos pelo tratamento da proteína com tripsina e. As sequências obtidas assim obtidas foram utilizadas para buscar a sequência da ORF da VTDCE em um banco de cDNA. Por meio de PCR, a ORF da enzima foi clonada em vetor de clonagem e posteriormente de expressão. A rVTDCE expressa em Escherichia coli foi purificada por cromatografia de afinidade e utilizada para determinar algumas de suas propriedades, como atividade enzimática e antimicrobiana. A atividade enzimática foi avaliada através de ensaios fluorimétricos, onde a rVTDCE mostrou características similares à VTDCE nativa. Ensaios antimicrobianos foram realizados para avaliar a possível atividade sugerida após análise da sequencia da ORF da VTDCE. A análise molecular mostrou que a sequência da VTDCE apresenta semelhança com peptídeos antimicrobianos, fato comprovado através de ensaios antimicrobianos. Efetivamente, a VTDCE apresentou atividade antimicrobiana tanto na sua forma nativa como na forma desnaturada desprovida de atividade peptidásica, demonstrando que ambas as atividades são independentes. Foram feitos também ensaios imunológicos, onde anticorpos policlonais anti-rVTDCE foram produzidos em coelhos e bovinos. Por Western blot foi observado que os anticorpos policlonais produzidos contra VTDCE recombinante reconheceram a VTDCE nativa, e o inverso também, indicando que a forma recombinante pode ser utilizada para experimentos de vacinação. / The cattle tick, Rhipicephalus (Boophilus) microplus is a hematophagous arthropod, responsible for significant losses in livestock. During the tick embryo the vitellin-degrading cysteine endopeptidase (VTDCE) participates in the vitellin (Vt) hydrolysis, the main energy source and amino acids during this period. Due to the importance of this enzyme in parasite physiology the VTDCE is a potential target for development of anti-tick vaccine. In previous studies, the immunization with native VTDCE, purified from tick egg, conferred protection against R. microplus. However, the extensive and expensive purification process, plus the low achievement precludes the use of the native protein for commercial purposes. This difficulty can be overcome by the expression of a recombinant protein in heterologous organism. This work aims the expression, purification and characterization of recombinant VTDCE (rVTDCE). Part of the native VTDCE amino acid sequence was determined by Edman sequencing. Native protein was also trypsinized and peptides sequenced by mass spectrometry. The sequences obtained from mass spectrometry and Edman sequencing were used to search the ORF sequence of VTDCE in a tick cDNA library. Through PCR enzyme ORF was cloned into a cloning vector and further into an expression vector. The rVTDCE expressed in Escherichia coli was purified by affinity chromatography and used to determine some of its properties such as antimicrobial and enzyme activity. The enzymatic activity was measured using fluorimetric assays, where rVTDCE had similar characteristics to VTDCE. Antimicrobial assays were performed to evaluate the possible activity suggested after sequence analysis. Molecular analysis showed that the sequence of VTDCE shows similarity with antimicrobial peptides, which was proven through antimicrobial assays. Effectively, the VTDCE presented antimicrobial activity even when the protein didn’t present enzymatic activity, demonstrating that both activities are independent. Immunological assays were also performed. Polyclonal anti-rVTDCE serum were produced in rabbits and cattle. Western blot showed that the polyclonal antibodies raised against recombinant VTDCE recognized the native form, indicating that the recombinant form may be used for vaccination experiments.

The aim of this thesis was to study the regulation of proteinase secretion by epithelial cells (E-cells) derived from the epithelial cell rests of Malassez. Since these epithelial cell rests are present only in small numbers in-vivo, E-cells derived from porcine cell rests were cultured according to Brunette et al. (1976) and conditions chosen so that detectable amounts of the proteinases, neutral proteinase and plasminogen activator, could be obtained. The regulation of the secretion of these enzymes was investigated by varying the cell population density, adding E.Coli lipopolysaccharide to the cultures and altering the shape of the E-cells by both chemical and physical means. Cell population density modulated both neutral proteinase and plasminogen activator secretion. Neutral proteinase secretion was highest at low cell population densities and the activity decreased with increasing cell population density. Plasminogen activator secretion followed a similar pattern. Escherichia coli lipopolysaccharide (E.coli LPS) stimulated both neutral proteinase and plasminogen activator secretion. LPS extracted by the phenol method and LPS extracted by the trichloroacetic acid method caused similar increases in neutral proteinase activity but the increase in plasminogen activator activity was greater when the trichloroacetic acid extracted LPS was used. These findings support the proposal that bacterial LPS in contact with periapical tissues could stimulate the epithelial cell rests into increased production of proteinases, thereby contributing to the degradation of connective tissue associated with dental cyst formation. E-cell shape was altered by physical and chemical means. Addition of cholera toxin and dibutyryl cAMP caused E-cells to flatten. Phorbol myristate acetate, however, caused the cells to retract slightly. Mechanical stretching was applied to the cells to cause cell flattening, and cell rounding was effected by mechanical relaxation. Another method made use of E-cells grown on a substrate with V-shaped grooves which caused the cells to adopt a rounder shape more frequently than cells grown on a flat substrate. In addition, dishes coated with increasing concentrations of poly(HEMA) solution, which altered dish adhesivity to the cell, caused the cells to become less well-spread. In all experiments, a more flattened cell shape correlated with a reduced level of neutral proteinase and plasminogen activator secretion while a more rounded shape correlated with increased amounts of neutral proteinase and plasminogen activator secretion. / Dentistry, Faculty of / Graduate

La protéine BACE (?-site APP Cleaving Enzyme) joue un rôle clé dans la production du peptide amyloïde ? (A?) à l'origine de l'établissement de la maladie d'Alzheimer. À cause de son rôle central dans la maladie, BACE représente une cible potentielle dans le développement de thérapies. Récemment, un premier rôle physiologique pour BACE a été identifié, remettant en doute les approches thérapeutiques visant son inhibition. Des stratégies alternatives ciblant des modulateurs de l'activité de BACE pourraient représenter une approche plus sécuritaire pour traiter la maladie. Dans cette étude, nous avons tenté de développer un essai pour cribler des modulateurs de l'activité de BACE en utilisant deux systèmes différents : le système raporteur luciférase et un système basé sur le Bioluminescence Resonance Energy Transfert 2 (BRET2). Malgré les nombreuses optimisations réalisées, nous n'avons pas réussi à mettre au point un essai efficace permettant de cribler des modulateurs de l'activité de BACE.

La MMP2 est une protéinase stromale qui dégrade plusieurs éléments de la matrice extracellulaire et qui active d’autres MMPs dont la MMP9. La MMP14 active la MMP2 via l’inhibiteur de la pro-MMP2, le TIMP2. Cette étude avait pour buts de démontrer l’association entre la surexpression de la MMP2 et la récidive du CaP, d’évaluer l’influence de la MMP9, de la MMP14 et du TIMP2 sur cette association, puis de tester par un modèle murin l’influence de la MMP14 stromale sur la croissance tumorale. Nous avons analysé immunohistochimiquement 204 cas de CaP (T3NxM0) et avons étudié séparément les cellules cancéreuses, stromales et épithéliales bénignes (CEB), notamment selon le pourcentage d’expression des marqueurs (< 10% ou ≥ 10%). Le suivi médian est de 4,61 ans. La surexpression de la MMP9 dans les cellules cancéreuses est associée à un score de Gleason élevé (8-10) (p = 0,0009). Dans les CEB, la surexpression la MMP14 est associée au niveau de PSA sérique initial bas (≤ 20 ng/ml) (p = 0,0027). Le TIMP2 est protecteur (RR = 0,573, p = 0,0233) lorsque fortement exprimé dans les cellules stromales. La MMP2 augmente le risque de récidive lorsqu’exprimée par les cellules cancéreuses (RR = 1,549, p = 0,0027, test de tendance). L’étude de la croissance de tumeurs injectées à des souris nues/nues suggère que la MMP14 est associée à l’implantation tumorale. La MMP9 et la MMP14 seraient impliquées dans l’évolution du CaP alors que la MMP2 et le TIMP2 peuvent servir de marqueurs pronostiques pour les CaP T3NxM0. / Introduction: The matrix metalloproteinase 2 (MMP2) is associated with poor prognosis in many neoplasms. MMP14 activates MMP2 using pro-MMP2 specific inhibitor TIMP2 as a receptor. Activated MMP2 degrades extracellular matrix components such as collagen and gelatin, and activates other MMPs including MMP9 (gelatinase B). We therefore tested the influence of MMP9, MMP14 and TIMP2 expression on prostate cancer (Pca) disease-free survival and the association between MMP2, MMP9, MMP14 and TIMP2. Stromal MMP14 involvement in tumor growth was also tested. Material and methods: By immunohistochemistry, we analyzed 200 T3NxM0 Pca cases. We evaluated marker expression separately in cancer, stromal and benign epithelial (BE) cells according to a percentage scale (0, < 10, 10-50 and ≥ 50%) and to low (< 10%) or high (≥ 10%) expression of the markers. MCF7 cells were injected subcutaneously to nu/nu mice with MMP14 -/- fibroblasts and their growth was compared to MCF7 + MMP14 +/+ fibroblasts tumors. Results: Median follow-up was 4.61 years. MMP9 overexpression in cancer cells was associated with high Gleason score (8-10) (p = 0.0009). Low initial PSA serum levels (≤ 20ng/ml) were indirectly associated with MMP14 overexpression in BE cells (p = 0.0027) and with MMP9 overexpression in stromal (p = 0.0050) and BE cells (p = 0.0056). There was a decreased risk of Pca recurrence with high (≥ 10%) TIMP2 expression in stromal cells (hazard ratio (HR) = 0.573, p = 0.0233) and an increased risk of Pca recurrence with MMP2 expression by > 50% of BE cells (HR = 3.006, p = 0.0387). Increased risk of Pca recurrence was also observed with high MMP2 expression (HR = 1.549, p = 0.0027, trend test) and with the following combinations: low TIMP2 in stromal cells and high MMP2 in BE cells (HR = 4.121, p < 0.0001); high MMP2 in stromal cells and low TIMP2 in cancer cells (HR = 2.742, p = 0.0171). MCF7 studies suggest MMP14 stromal involvement in Pca implantation. Conclusions: MMP9 and MMP14 are involved mostly in Pca implantation. MMP2 and TIMP2 might be used as predictors of disease-free survival in T3NxM0 Pca.

Serina endopeptidases de insetos, principalmente tripsinas e quimotripsinas, estão envolvidas na digestão inicial de proteínas. Genes codificadores para estas enzimas estão organizados em famílias multigênicas tendo expressão diferencial de acordo com a dieta do inseto, estando envolvidos no desenvolvimento de resistência a diferentes metabólitos secundários vegetais. Para uma melhor compreensão desta interação, fez-se necessário o isolamento destas enzimas para insetos de diferentes ordens, bem como a caracterização de suas especificidades por duas abordagens: (a) caracterização cinética dos subsítios componentes do sítio de ligação de tripsinas e quimotripsinas, utilizando diferentes substratos, modificadores químicos e inibidores e (b) estudos estruturais por modelagem molecular, clonagem, expressão e cristalização destas enzimas de insetos. Além disso, estudos evolutivos por análise de distância possibilitaram uma caracterização inicial da interação insetoplanta. Estas determinações permitiram verificar que tripsinas de insetos apresentam diferenças de especificidade tanto dentre as diferentes ordens de insetos quanto em relação às tripsinas de vertebrados, sendo que as tripsinas da ordem Lepidóptera apresentam troca de especificidade primária hidrolisando preferencialmente substratos P1 Lys. Foram também observadas diferenças de hidrofobicidade para os subsítios caracterizados sendo que estes apresentam hidrofobicidades crescentes segundo o grau de complexidade dos insetos na sua escala evolutiva. A troca de especificidade e o aumento da hidrofobicidade podem permitir a hidrólise dos inibidores vegetais protéicos. A análise das sequências de tripsinas de insetos por Neighbor Joining (NJ) compõe uma árvore de distâncias topologicamente semelhante à árvore de relações filogenéticas determinadas por morfologia. A sobreposição de estruturas pré -determinadas de tripsina complexada a diferentes inibidores permite a identificação de posições de interação enzima-inibidor que justificam a classificação em grupos distintos de enzimas sensíveis ou resistentes a presença de inibidores na dieta de insetos. Da mesma forma: a caracterização da especificidade das quimotripsinas de insetos permitiu a separação de grupos distintos de quimotripsinas. Estes grupos são sustentados pela substituição do resíduo 59 em insetos polífagos que alimentam-se de plantas que contêm cetonas naturais reativas. Estas caracterizações demonstram a importância de um estudo detalhado da especificidade de serina endopeptidases possibilitando o desenho de moléculas apropriadas para inibição destas e desenvolvimento de estratégias de controle de insetos. / Insect serine endopeptidases, mairily trypsin and chymotrypsin are involved in initial protein digestion. Genes that encode these proteins are members of complex multigene families and are differentially expressed according to insects diet , thus being involved with resistance to plant metabolites. Purification of trypsins from different insect orders and chymotrypsins, as well as, characterization of their specificity are essential to a better understanding of this interaction. Characterization relied on two approaches: (a) kinetic characterization of the binding subsities of trypsins and chymotrypsins using different substrates, chemical modification and inhibition assays and (b) study of protein structure by molecular modelling and cloning, expression and crystallization of these enzymes. Besides that, evolutionary studies performed through distance analysis, permitted the investigation of plantinsect interaction. These characterizations showed that insect trypsins, in terms of specificity, are quite different from vertebrate trypsins and among insect orders. Lepidopterans trypsins have a distinct primary specificity, since they hydrolyses preferentially P1 Lys substrates, and present a crescent subsite hydrophobicity, which is directly correlated with the evolutionary scale. Both, the specificity exchange and the crescent hydrophobicity can allow the hydrolysis of vegetal proteic inhibitors. The analysis of trypsin sequences in Neighbor-Joining (NJ) algorithm yield a distance tree that is coherent with morphological phylogenetic relationships. The superposition of predicted structures of trypsins-inhibitors complexes permits to observe amino acid residues of interaction between enzyme-inhibitor, which support the distinction of different groups between sensitive and insensitive trypsins to the presence of inhibitors on insect diet. Similarly, characterization of insect chymotrypsins according to their specificity allowed us to classify these enzymes into different groups. These groups are supported by residue 59 replacements in polyphagous insects, which feed on plants bearing natural reactive ketones. These studies show the irnportance of a detailed study of serine endopeptidases, which may help in the development of better insect control strategies.

Ip Lai Fong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 81-92). / Abstracts in English and Chinese. / Table of Contents --- p.1 / Abbreviations --- p.4 / Chapter Chapter 1 --- Introduction and Background --- p.5 / Chapter 1.1 --- Endothelin system --- p.5 / Chapter 1.1.1 --- Endothelins --- p.5 / Chapter 1.1.2 --- Endothelin converting enzyme (ECE) isoforms --- p.12 / Chapter 1.1.3 --- Endothelin receptors --- p.24 / Chapter 1.2 --- Signal-transduction mechanisms in ET system --- p.27 / Chapter 1.3 --- The aim of the present thesis --- p.31 / Chapter Chapter 2 --- Materials and Methods --- p.32 / Chapter 2.1 --- Primer Design --- p.32 / Chapter 2.2 --- Total RNA Isolation --- p.33 / Chapter 2.3 --- Reverse transcriptase polymerase chain reaction (RT-PCR) --- p.34 / Chapter 2.3.1 --- First Strand cDNA Synthesis --- p.34 / Chapter 2.3.2 --- PCR reaction --- p.34 / Chapter 2.4 --- Agarose gel electrophoresis --- p.35 / Chapter 2.5 --- Ligation of PCR inserts to cloning vector by TA cloning method --- p.35 / Chapter 2.6 --- Competent cell preparation --- p.36 / Chapter 2.7 --- Transformation and Screening --- p.37 / Chapter 2.8 --- Plasmid DNA Extraction --- p.38 / Chapter 2.9 --- DNA sequencing --- p.38 / Chapter 2.10 --- DIG RNA Labeling --- p.38 / Chapter 2.10.1 --- Plasmid Linearization --- p.38 / Chapter 2.10.2 --- Transcription --- p.39 / Chapter 2.10.3 --- Probe purification --- p.39 / Chapter 2.11 --- In situ hybridizaion --- p.40 / Chapter 2.11.1 --- Tissue preparation and slide mounting --- p.40 / Chapter 2.11.2 --- Non-radioactive in situ hybridization --- p.41 / Chapter 2.12 --- Whole Mount non-radioactive in situ hybridization --- p.42 / Chapter 2.12.1 --- Dissection and fixation --- p.42 / Chapter 2.12.2 --- Hybridization --- p.43 / Chapter 2.12.3 --- Antibody incubation --- p.43 / Chapter 2.12.4 --- Histochemistry --- p.44 / Chapter Chapter 3 --- Results --- p.46 / Chapter 3.1 --- The molecular cloning of ECE-2 from rat brain --- p.46 / Chapter 3.2 --- Sequence characteristics of rat ECE-2 --- p.52 / Chapter 3.3 --- Comparison of rat ECE-2 with bovine and human ECE-2 and with the rat ECE-1 --- p.53 / Chapter 3.4 --- Tissue distribution of ECE-2 in rat and localization in C6 glial cells by RT-PCR --- p.60 / Chapter 3.5 --- ECE-2 in rat embryos at different gestation stages by RT-PCR --- p.60 / Chapter 3.6 --- ECE-2 distribution in C6 glioma cells --- p.63 / Chapter 3.7 --- ECE-2 distribution in rat embryo E15.5 --- p.63 / Chapter 3.8 --- ECE-2 distribution in rat brain sections --- p.63 / Chapter Chapter 4 --- p.74 / Discussion --- p.74 / References --- p.81

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2006. / Härtill 3 uppsatser.

Serina endopeptidases de insetos, principalmente tripsinas e quimotripsinas, estão envolvidas na digestão inicial de proteínas. Genes codificadores para estas enzimas estão organizados em famílias multigênicas tendo expressão diferencial de acordo com a dieta do inseto, estando envolvidos no desenvolvimento de resistência a diferentes metabólitos secundários vegetais. Para uma melhor compreensão desta interação, fez-se necessário o isolamento destas enzimas para insetos de diferentes ordens, bem como a caracterização de suas especificidades por duas abordagens: (a) caracterização cinética dos subsítios componentes do sítio de ligação de tripsinas e quimotripsinas, utilizando diferentes substratos, modificadores químicos e inibidores e (b) estudos estruturais por modelagem molecular, clonagem, expressão e cristalização destas enzimas de insetos. Além disso, estudos evolutivos por análise de distância possibilitaram uma caracterização inicial da interação insetoplanta. Estas determinações permitiram verificar que tripsinas de insetos apresentam diferenças de especificidade tanto dentre as diferentes ordens de insetos quanto em relação às tripsinas de vertebrados, sendo que as tripsinas da ordem Lepidóptera apresentam troca de especificidade primária hidrolisando preferencialmente substratos P1 Lys. Foram também observadas diferenças de hidrofobicidade para os subsítios caracterizados sendo que estes apresentam hidrofobicidades crescentes segundo o grau de complexidade dos insetos na sua escala evolutiva. A troca de especificidade e o aumento da hidrofobicidade podem permitir a hidrólise dos inibidores vegetais protéicos. A análise das sequências de tripsinas de insetos por Neighbor Joining (NJ) compõe uma árvore de distâncias topologicamente semelhante à árvore de relações filogenéticas determinadas por morfologia. A sobreposição de estruturas pré -determinadas de tripsina complexada a diferentes inibidores permite a identificação de posições de interação enzima-inibidor que justificam a classificação em grupos distintos de enzimas sensíveis ou resistentes a presença de inibidores na dieta de insetos. Da mesma forma: a caracterização da especificidade das quimotripsinas de insetos permitiu a separação de grupos distintos de quimotripsinas. Estes grupos são sustentados pela substituição do resíduo 59 em insetos polífagos que alimentam-se de plantas que contêm cetonas naturais reativas. Estas caracterizações demonstram a importância de um estudo detalhado da especificidade de serina endopeptidases possibilitando o desenho de moléculas apropriadas para inibição destas e desenvolvimento de estratégias de controle de insetos. / Insect serine endopeptidases, mairily trypsin and chymotrypsin are involved in initial protein digestion. Genes that encode these proteins are members of complex multigene families and are differentially expressed according to insects diet , thus being involved with resistance to plant metabolites. Purification of trypsins from different insect orders and chymotrypsins, as well as, characterization of their specificity are essential to a better understanding of this interaction. Characterization relied on two approaches: (a) kinetic characterization of the binding subsities of trypsins and chymotrypsins using different substrates, chemical modification and inhibition assays and (b) study of protein structure by molecular modelling and cloning, expression and crystallization of these enzymes. Besides that, evolutionary studies performed through distance analysis, permitted the investigation of plantinsect interaction. These characterizations showed that insect trypsins, in terms of specificity, are quite different from vertebrate trypsins and among insect orders. Lepidopterans trypsins have a distinct primary specificity, since they hydrolyses preferentially P1 Lys substrates, and present a crescent subsite hydrophobicity, which is directly correlated with the evolutionary scale. Both, the specificity exchange and the crescent hydrophobicity can allow the hydrolysis of vegetal proteic inhibitors. The analysis of trypsin sequences in Neighbor-Joining (NJ) algorithm yield a distance tree that is coherent with morphological phylogenetic relationships. The superposition of predicted structures of trypsins-inhibitors complexes permits to observe amino acid residues of interaction between enzyme-inhibitor, which support the distinction of different groups between sensitive and insensitive trypsins to the presence of inhibitors on insect diet. Similarly, characterization of insect chymotrypsins according to their specificity allowed us to classify these enzymes into different groups. These groups are supported by residue 59 replacements in polyphagous insects, which feed on plants bearing natural reactive ketones. These studies show the irnportance of a detailed study of serine endopeptidases, which may help in the development of better insect control strategies.

by Chung Wilson. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 126-149). / Abstracts in English and Chinese. / Acknowledgements --- p.i / Abstract (English) --- p.ii / Abstract (Chinese) --- p.v / Content --- p.vii / Abbreviations --- p.xii / List of Figures --- p.xv / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Alzheimer's disease --- p.1 / Chapter 1.1.1 --- History of Alzheimer's disease --- p.1 / Chapter 1.1.2 --- Definition of Alzheimer's disease --- p.2 / Chapter 1.1.3 --- Symptoms of Alzheimer's disease --- p.6 / Chapter 1.1.3.1 --- Memory deficit --- p.6 / Chapter 1.1.3.2 --- Difficulty in learning --- p.6 / Chapter 1.1.3.3 --- Language difficulties --- p.7 / Chapter 1.1.3.4 --- Decline in ability to perform routine tasks --- p.7 / Chapter 1.1.4 --- Prevalence of Alzheimer's disease --- p.8 / Chapter 1.2 --- Present treatment of Alzheimer's disease --- p.9 / Chapter 1.2.1 --- Acetylcholine and dementia --- p.9 / Chapter 1.2.2 --- Tacrine as first drug approved by US Food and Drug Administration --- p.9 / Chapter 1.3 --- Proposed theory of Alzheimer's disease formation --- p.10 / Chapter 1.3.1 --- The amyloid cascade hypothesis --- p.10 / Chapter 1.3.1.1 --- The amyloid precursor protein --- p.10 / Chapter 1.3.1.2 --- The processing of amyloid precursor protein --- p.12 / Chapter 1.3.1.3 --- Neurotoxic effect of amyloid plaque --- p.15 / Chapter 1.3.1.4 --- Genetic factors --- p.15 / Chapter 1.3.1.4.1 --- The amyloid precursor protein --- p.15 / Chapter 1.3.1.4.2 --- Apolipoprotein E (ApoE) --- p.16 / Chapter 1.3.1.4.3 --- Presenilin genes --- p.17 / Chapter 1.3.2 --- Tau and tangle hypothesis --- p.19 / Chapter 1.3.2.1 --- Tau protein --- p.19 / Chapter 1.3.2.2 --- Paired helical filaments (PHF) --- p.20 / Chapter 1.3.2.3 --- Tau protein kinase --- p.20 / Chapter 1.3.2.3.1 --- Glycogen synthase kinase-3 (GSK-3) --- p.21 / Chapter 1.3.2.3.2 --- Cyclin-dependent kinase 5 (CDK5) --- p.21 / Chapter 1.3.2.4 --- Tangle leads to dementia --- p.22 / Chapter 1.4 --- Cross-talk between the two hypotheses --- p.24 / Chapter 1.5 --- β -secretase (BACE) --- p.24 / Chapter 1.5.1 --- Discovery of β-secretase (BACE) --- p.24 / Chapter 1.5.2 --- Detailed structure of BACE --- p.25 / Chapter 1.5.3 --- Comparsion of human and mouse BACE --- p.27 / Chapter 1.5.4 --- Comparsion of BACE-1 with BACE-2 --- p.27 / Chapter 1.5.5 --- Properties of BACE-1 --- p.28 / Chapter 1.5.6 --- Expression of BACE in E.coli --- p.29 / Chapter 1.5.7 --- Expression of BACE in mammalian cells --- p.30 / Chapter 1.6 --- Objectives of the present study --- p.32 / Chapter Chapter 2 --- Materials and Methods --- p.34 / Chapter 2.1 --- Recombinant DNA techniques --- p.34 / Chapter 2.1.1 --- Amplification of genes by PCR techniques --- p.34 / Chapter 2.1.2 --- Agarose gel electrophoresis --- p.34 / Chapter 2.1.3 --- Extraction of DNA from agarose gel --- p.35 / Chapter 2.1.4 --- Digestion of various vectors and inserts --- p.36 / Chapter 2.1.5 --- Ligation of DNA fragments --- p.36 / Chapter 2.1.6 --- Preparation of Escherichia coli competent cells --- p.37 / Chapter 2.1.7 --- Bacterial transformation --- p.38 / Chapter 2.1.8 --- Minipreparation of plasmid DNA --- p.38 / Chapter 2.1.9 --- Large scale preparation of plasmid DNA --- p.39 / Chapter 2.1.10 --- Strain storage and revival --- p.40 / Chapter 2.1.11 --- Plasma DNA purification by High Pure plasmid isolation kit --- p.41 / Chapter 2.1.12 --- DNA sequencing --- p.42 / Chapter 2.1.13 --- Quantitation of DNA by spectrophotometric method --- p.43 / Chapter 2.2 --- Prokaryotic protein expression --- p.43 / Chapter 2.2.1 --- Selection of appropriate clones for recombinant protein expression using conventional method --- p.43 / Chapter 2.2.2 --- Selection of appropriate clones for recombinant protein expression using modified method --- p.44 / Chapter 2.2.3 --- Large -scale expression of recombinant human BACE protein using modified method --- p.45 / Chapter 2.2.4 --- Preparation of inclusion body from the bacterial expression culture --- p.46 / Chapter 2.2.5 --- Refolding of human BACE --- p.47 / Chapter 2.2.6 --- Purification of recombinant human BACE by immobilized metal ion affinity chromatography (IMAC) --- p.47 / Chapter 2.2.7 --- Protein concentration determination --- p.48 / Chapter 2.2.8 --- Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) --- p.48 / Chapter 2.2.9 --- Western blotting --- p.50 / Chapter 2.2.10 --- Plasmid stability test --- p.50 / Chapter 2.3 --- Mammalian cell expression --- p.51 / Chapter 2.3.1 --- Transient transfection --- p.51 / Chapter 2.3.2 --- Measuring transfection efficiency --- p.52 / Chapter 2.3.3 --- Stable transfection --- p.52 / Chapter 2.3.4 --- Preparation of membrane extracts from CHO cells --- p.53 / Chapter 2.4 --- HPLC analysis --- p.53 / Chapter 2.4.1 --- Preparation of samples --- p.53 / Chapter 2.4.2 --- Reverse phase HPLC --- p.54 / Chapter 2.5 --- Fluorometric assay --- p.54 / Chapter 2.6 --- Immunohistochemistry --- p.55 / Chapter 2.7 --- Reagents and buffers --- p.55 / Chapter 2.7.1 --- Medium for bacterial culture --- p.56 / Chapter 2.7.2 --- Reagents for preparation of plasmid DNA --- p.56 / Chapter 2.7.3 --- Buffers for agarose gel electrophoresis --- p.57 / Chapter 2.7.4 --- Buffers for SDS-PAGE --- p.58 / Chapter 2.7.5 --- Buffer for purification of protein --- p.60 / Chapter 2.7.6 --- Buffer for Western Blotting --- p.61 / Chapter 2.7.7 --- Culturing medium of CHO cells --- p.62 / Chapter 2.7.8 --- Solutions for estimating transfection efficiency --- p.63 / Chapter 2.7.9 --- Reagents for HPLC --- p.64 / Chapter 2.7.10 --- Reagents for fluorometric assays --- p.65 / Chapter 2.7.11 --- Reagents for Immunohistochemistry --- p.66 / Chapter Chapter 3 --- Results --- p.67 / Chapter 3.1 --- Expression of BACE in E. coli --- p.67 / Chapter 3.1.1 --- Cloning of truncated human and mouse BACE into pRSET --- p.67 / Chapter 3.1.2 --- Expression of BACE in BL21(DE3)LysS cells --- p.70 / Chapter 3.1.2.1 --- Expression of truncated mouse and human BACEin BL21(DE3)LysS cells using conventional method --- p.70 / Chapter 3.1.2.2 --- Expression of truncated mouse and human BACEin BL21(DE3)LysS cells using modified method --- p.72 / Chapter 3.1.3 --- Analysis of BACE activity of purified recombinant proteins --- p.76 / Chapter 3.1.3.1 --- Fluorometric analysis --- p.76 / Chapter 3.2 --- Expression of BACE in mammalian cells --- p.81 / Chapter 3.2.1 --- "Cloning of full length mouse and human BACE into pCDNA3, pCDNA4HisMax" --- p.81 / Chapter 3.2.2 --- Transient transfection --- p.84 / Chapter 3.2.2.1 --- Western blot analysis --- p.86 / Chapter 3.2.2.2 --- Fluorometric analysis --- p.88 / Chapter 3.2.2.3 --- HPLC --- p.91 / Chapter 3.2.3 --- Stable transfection --- p.100 / Chapter 3.2.3.1 --- Western blot analysis --- p.101 / Chapter 3.2.3.2 --- Fluorometric analysis --- p.103 / Chapter 3.2.3.3 --- HPLC --- p.105 / Chapter 3.2.3.4 --- Immunohistochemistry --- p.112 / Chapter Chapter 4 --- Discussion --- p.115 / References --- p.126 / Appendix --- p.i / Chapter A1 --- Vector circle map --- p.i / Chapter A1-1 --- Vector circle map of pBluescript II- --- p.i / Chapter A1-2 --- Vector circle map of pCDNA3 --- p.ii / Chapter A1-3 --- Vector circle map of pCDNA4HisMax --- p.iii / Chapter A1-4 --- Vector circle map of pRSET --- p.iv / Chapter A2 --- Primer lists --- p.v / Chapter A3 --- Chemical structure of fluorophore and quench used in fluorometric assay --- p.vi

L'objectif était d'effectuer la première synthèse total de Cyclothéonamide C (CTC), un pentapeptide macrocyclique, inhibiteur puissant des sérine protéases. Il a plusieurs motifs structuraux uniques, comprenant un vinylogue de déshydrotyrosine (V-deltaTyr) et une alpha-Cétohomoarginine (K-Arg). Le plus grand défi résidait à créer le résidu K-Arg ou un précurseur approprié alpha-Hydroxyhomoarginine (H-Arg) dans des intermédiaires peptidiques avancés. On propose trois stratégies différentes pour y parvenir : "Passerini-Acyl Migration" (PAM), "Masked Acyl Cyanide" (MAC) et "alpha-Keto-Acyl Cyanide" (KAC) . Une préparation préalable de peptides électrophiles et nucléophiles (aldéhydes et alpha-cétocyanophosphoranes ; amines et isonitiles) est nécessaire pour l'exécution des différentes stratégies. Les trois stratégies sont alors développées pour fournir des pentapeptides linéaires transformés ensuite en macrocycliques. Les étapes de déprotection et d'oxydation finissent formellement la synthèse de CTC