Die Fusionsreaktion des Coronavirus MHV wird vom S-Protein vermittelt. In der vorliegenden Arbeit wurde der Eintrittsweg von MHV-A59 in Mauszellen untersucht. Die Infektivität kann durch lysosomotrope Substanzen und Inhibitoren der Clathrin-abhängigen Endozytose gehemmt werden. Der Eintritt von MHV-A59 in Mauszellen erfolgt über die Clathrin-abhängige Endozytose und setzt die anschließende Fusion der viralen und zellulären Membran bei niedrigem pH-Wert voraus. Fluoreszenzmikroskopische Studien zur Interaktion fluoreszenzmarkierter MHV-A59 Partikel mit Mauszellen bestätigen, dass MHV-A59 über Endozytose aufgenommen wird. Nach Bindung der Viren an die Zellen und anschließende Erniedrigung des pH-Wertes kommt es zur Färbung der Plasmamembran. Die Erniedrigung des pH-Wertes in Abwesenheit des Rezeptors führt zu einer irreversiblen Konformationsumwandlung im viralen Fusionsprotein, die die Inaktivierung der Fusionsaktivität und den Verlust der Infektivität zur Folge hat. Die Ergebnisse deuten auf die Beteiligung des endozytotischen Weges für den viralen Eintritt von MHV-A59 hin. Ein niedriger pH-Wert eines zellulären endosomalen Kompartiments induziert vermutlich die Konformationsänderung im S-Protein und löst die Fusionsreaktion aus. Ein vorläufiges 3D-Modell des S-Proteins von MHV-A59 konnte erstellt werden. Darüber hinaus wurde die Struktur und Fusionsfähigkeit des S-Proteins von SARS-CoV analysiert. Ein Zell-Zell-Fusionsassay konnte nachweisen, dass die Fusion zwischen S-Protein und ACE2-exprimierenden Zellen sowohl abhängig vom pH-Wert als auch von der proteolytischen Spaltung in S1- und S2-Untereinheit ist und durch Erniedrigung des pH-Wertes zusätzlich verstärkt werden kann. Im abschließenden Teil der Arbeit wurde auf Basis theoretischer Untersuchungen eine Vorhersage des mutmaßlichen Fusionspeptids des S-Proteins von MHV-A59, welches alle wesentlichen Merkmale eines internen Fusionspeptids aufweist, vorgenommen. Es liegt nahe der "Heptad-Repeat" (HR) Domäne HR1. / Fusion of the Coronavirus MHV-A59 is mediated by the viral S-protein. The entry pathway of MHV-A59 into murine cells was studied in this work. Infection was strongly inhibited by lysosomotropic compounds and substances interfering with clathrin-dependent endocytosis, suggesting that MHV-A59 is taken up via endocytosis and delivered to acidic compartments. Fluorescence microscopy of labeled MHV-A59 confirmed that the virus is taken up via endocytosis. When the virus was bound to cells and the pH was lowered to 5.0, we observed a strong labeling of the plasma membrane. Electron microscopy revealed low pH triggered conformational alterations of the S-ectodomain. These alterations are likely to be irreversible because low pH-treatment of viruses caused an irreversible loss of fusion activity. The results imply that endocytosis plays a major role in MHV-A59 infection and that the acidic pH of the endosomal compartment triggers a conformational change of the S-protein mediating fusion. Furthermore the conformation of the trimeric spike protein of the murine hepatitis virus A59 was characterized by cryoelectron microscopy. A preliminary 3D-reconsruction of the native structure could be accomplished. Besides we studied the structure and fusion capability of the spike protein expressed by SARS-CoV. The cell-based fusion assay revealed that fusion of spike protein and ACE2-receptor expressing cells was strongly dependent on low pH and on proteolytic cleavage of the S-protein into S1 and S2 subunit. Additionally fusion could be significantly increased by lowering of the pH. The theoretical part of the thesis allowed the identification of the putative fusion peptide, which showed main characteristics of internal fusion peptides. It allows the heptad regions of the spike protein to assemble in the six-helix bundle structure (6HB). This structure is of great importance to initiate the approximation of viral and cellular membrane and thus to induce fusion.

Introdução: O fragmento amino-terminal do pró-peptídeo natriurético do tipo B (NT-proBNP) é um forte marcador de doença cardiovascular com evidências recentes de que a inflamação também pode influenciar seus valores. A diferenciação dessa variável de confusão é de particular interesse nas doenças reumáticas. Objetivos: Avaliar o comportamento dos valores de NT-proBNP em pacientes com espondilite anquilosante (EA) pré e pós uso de bloqueadores de TNF para determinar a possível associação entre os valores de NT-proBNP e os parâmetros inflamatórios. Métodos: Quarenta e cinco pacientes consecutivos com EA sem evidência prévia ou atual de doença cardiovascular ou disfunção miocárdica sistólica e que eram elegíveis para terapia anti-TNF foram incluídos prospectivamente. Todos os pacientes receberam bloqueadores de TNF e foram avaliados para concentrações circulantes de NT-proBNP, parâmetros clínicos e laboratoriais de atividade de doença, fatores de risco cardiovasculares tradicionais e ecodopplercardiografia convencional e tecidual no momento da inclusão e após seis meses de tratamento. Resultados: No momento da inclusão, todos os pacientes tinham EA ativa, os valores de NT-proBNP tinham uma mediana de 36 (20-72) pg/mL e 11% dos valores estavam altos mesmo na ausência de alteração miocárdica sistólica. A análise de regressão linear múltipla revelou que esse peptídeo estava independentemente correlacionado com o VHS (p < 0,001), com a idade dos pacientes (p = 0,01) e com a pressão de pulso (p = 0,01) no momento da inclusão. Após seis meses, todos os parâmetros relacionados a doença de base melhoraram e os valores de NT-proBNP se reduziram significativamente [24 (16-47) pg/mL, p = 0,037] quando comparados com os valores do momento da inclusão. As mudanças nos valores de NT-proBNP correlacionaram-se positivamente com as mudanças nos valores do VHS (r = 0,41, p = 0.006). Os fatores de risco cardiovasculares avaliados permaneceram estáveis durante o seguimento. Conclusão: As elevações nos valores de NT-proBNP devem ser interpretadas com cuidado nos pacientes com EA ativa e sem evidência de doença cardiovascular. A redução no curto prazo dos valores de NT-proBNP nesses pacientes recebendo terapia anti-TNF parece refletir uma melhora do estado inflamatório / Introduction: N-terminal pro-brain natriuretic peptide (NT-proBNP) is a strong marker of cardiovascular disease with recent evidence that inflammation may also influence its levels; discrimination of this confounding variable is of particular interest in rheumatic diseases. Objectives: to evaluate NT-proBNP in ankylosing spondylitis (AS) patients pre- and post-TNF blocker to determine the possible association between NT-proBNP levels and inflammatory parameters. Methods: Forty-five consecutive AS patients without previous/current cardiovascular disease or systolic myocardial dysfunction, who were eligible to anti-TNF therapy, were prospectively enrolled. All patients received TNF blockers and they were evaluated for circulating NT-proBNP levels, clinical and laboratory parameters of disease activity, traditional cardiovascular risk factors, and conventional and tissue Doppler imaging echocardiography at baseline (BL) and six months after (6M) treatment. Results: At BL, all patients had active AS, NT-proBNP levels had a median of 36 (20-72) pg/mL and 11% were high in spite of no systolic alteration. Multiple linear regression analysis revealed that this peptide, at BL, was independently correlated with ESR (p < 0.001), age (p = 0.01) and pulse pressure (p = 0.01). After 6M, all disease parameters improved and NT-proBNP levels were significantly reduced [24 (16-47) pg/mL, p = 0.037] compared to BL. Changes in NT-proBNP were positively correlated with ESR changes (r = 0.41, p = 0.006). Cardiovascular risk factors remained stable during follow-up. Conclusion: our data suggests that elevations of NT-proBNP should be interpreted with caution in active AS patients with no other evidence of cardiovascular disease. The short-term reduction of NT-proBNP levels in these patients receiving anti-TNF therapy appears to reflect an improvement in inflammatory status

Introdução: O fragmento amino-terminal do pró-peptídeo natriurético do tipo B (NT-proBNP) é um forte marcador de doença cardiovascular com evidências recentes de que a inflamação também pode influenciar seus valores. A diferenciação dessa variável de confusão é de particular interesse nas doenças reumáticas. Objetivos: Avaliar o comportamento dos valores de NT-proBNP em pacientes com espondilite anquilosante (EA) pré e pós uso de bloqueadores de TNF para determinar a possível associação entre os valores de NT-proBNP e os parâmetros inflamatórios. Métodos: Quarenta e cinco pacientes consecutivos com EA sem evidência prévia ou atual de doença cardiovascular ou disfunção miocárdica sistólica e que eram elegíveis para terapia anti-TNF foram incluídos prospectivamente. Todos os pacientes receberam bloqueadores de TNF e foram avaliados para concentrações circulantes de NT-proBNP, parâmetros clínicos e laboratoriais de atividade de doença, fatores de risco cardiovasculares tradicionais e ecodopplercardiografia convencional e tecidual no momento da inclusão e após seis meses de tratamento. Resultados: No momento da inclusão, todos os pacientes tinham EA ativa, os valores de NT-proBNP tinham uma mediana de 36 (20-72) pg/mL e 11% dos valores estavam altos mesmo na ausência de alteração miocárdica sistólica. A análise de regressão linear múltipla revelou que esse peptídeo estava independentemente correlacionado com o VHS (p < 0,001), com a idade dos pacientes (p = 0,01) e com a pressão de pulso (p = 0,01) no momento da inclusão. Após seis meses, todos os parâmetros relacionados a doença de base melhoraram e os valores de NT-proBNP se reduziram significativamente [24 (16-47) pg/mL, p = 0,037] quando comparados com os valores do momento da inclusão. As mudanças nos valores de NT-proBNP correlacionaram-se positivamente com as mudanças nos valores do VHS (r = 0,41, p = 0.006). Os fatores de risco cardiovasculares avaliados permaneceram estáveis durante o seguimento. Conclusão: As elevações nos valores de NT-proBNP devem ser interpretadas com cuidado nos pacientes com EA ativa e sem evidência de doença cardiovascular. A redução no curto prazo dos valores de NT-proBNP nesses pacientes recebendo terapia anti-TNF parece refletir uma melhora do estado inflamatório / Introduction: N-terminal pro-brain natriuretic peptide (NT-proBNP) is a strong marker of cardiovascular disease with recent evidence that inflammation may also influence its levels; discrimination of this confounding variable is of particular interest in rheumatic diseases. Objectives: to evaluate NT-proBNP in ankylosing spondylitis (AS) patients pre- and post-TNF blocker to determine the possible association between NT-proBNP levels and inflammatory parameters. Methods: Forty-five consecutive AS patients without previous/current cardiovascular disease or systolic myocardial dysfunction, who were eligible to anti-TNF therapy, were prospectively enrolled. All patients received TNF blockers and they were evaluated for circulating NT-proBNP levels, clinical and laboratory parameters of disease activity, traditional cardiovascular risk factors, and conventional and tissue Doppler imaging echocardiography at baseline (BL) and six months after (6M) treatment. Results: At BL, all patients had active AS, NT-proBNP levels had a median of 36 (20-72) pg/mL and 11% were high in spite of no systolic alteration. Multiple linear regression analysis revealed that this peptide, at BL, was independently correlated with ESR (p < 0.001), age (p = 0.01) and pulse pressure (p = 0.01). After 6M, all disease parameters improved and NT-proBNP levels were significantly reduced [24 (16-47) pg/mL, p = 0.037] compared to BL. Changes in NT-proBNP were positively correlated with ESR changes (r = 0.41, p = 0.006). Cardiovascular risk factors remained stable during follow-up. Conclusion: our data suggests that elevations of NT-proBNP should be interpreted with caution in active AS patients with no other evidence of cardiovascular disease. The short-term reduction of NT-proBNP levels in these patients receiving anti-TNF therapy appears to reflect an improvement in inflammatory status

Human α-N-Acetylglucosaminidase (Naglu) is a lysosomal acid hydrolase implicated in tthe rare metabolic storage disorder known as mucopolysaccharidosis type IIIB (MPS IIIB; also Sanfilippo syndrome B). Absence of this enzyme results in cytotoxic accumulation of heparan sulphate in the central nervous system, causing mental retardation and a shortened lifespan. Enzyme replacement therapy is not currently effective to treat neurological symptoms due to the inability of exogenous Naglu to access the brain. This laboratory uses a Spodoptera frugiperda (Sf9) insect cell system to express Naglu fused to a synthetic protein transduction domain with the intent to facilitate delivery of Naglu across the blood-brain barrier. The project described herein may be broken down into three main sections. Firstly, the impact of two cryptic splice sites on Naglu expression levels was analyzed in both transiently expressing Sf9 cultures and stably selected cell lines. Secondly, the effectiveness of the native Naglu secretion-signaling peptide in the Sf9 system was examined. Finally, purification of a Naglu fusion protein from suspension culture medium was performed using hydrophobic interaction chromatographic techniques. The ultimate goal of this research is to develop an efficient system for economical, large-scale production of a human recombinant Naglu fusion protein that has the potential to be successfully used for enzyme replacement therapy to treat MPS IIIB. / Graduate

Les systèmes d’efflux tripartite de type Resistance, Nodulation and cell-Division (RND) sont essentiels dans le maintien de phénotypes de résistance multidrogues et contre les métaux lourds dans nombreuses bactéries Gram-négatives. Le transport de ces composés toxiques hors de la cellule est permis par l’assemblage d’une protéine de type antiporteur cation/proton (unité RND) insérée dans la membrane interne, connectée à une protéine insérée dans la membrane externe, pour former un canal de sorti qui traverse l’entièreté de l’enveloppe cellulaire. Le troisième composant du système, la protéine de type membrane fusion protein (MFP) qui est aussi appelée periplasmic adaptor protein (PAP), est requis pour permettre l’assemblage de tout ce complexe à trois composants. Cependant, les MFPs sont supposées jouer un rôle important et actif dans le mécanisme d’efflux du substrat. Pour mieux comprendre le rôle des MFPs au sein des systèmes d’efflux de type RND, nous avons étudié les protéines ZneB (précédemment appelée HmxB) et SilB, les composants périplasmiques des systèmes ZneCBA et SilABC responsables de la résistance aux métaux lourds chez Cupriavidus metallidurans CH34. Nous avons identifié la spécificité de liaison au substrat de ces protéines, montrant leur capacité à fixer le zinc (ZneB), ou le cuivre et l’argent (SilB). De plus, nous avons résolu la structure cristalline de ZneB à une résolution de 2.8 Å dans la forme apo- et avec un ion zinc fixé. La structure de ZneB possède une architecture générale composée de quatre domaines caractéristiques des MFPs, et la présence du site de coordination au zinc dans une région très flexible à l’interface des domaines β-barrel et membrane proximal. Les modifications structurales que la protéine subit lors de la fixation du zinc on été observée dans le cristal mais aussi en solution, ce qui suggère un rôle actif des MFPs dans le mécanisme d’efflux des métaux, vraisemblablement via la fixation et le relargage de l’ion à l’antiporteur. Les études de sélectivité de transport des antiporteurs ZneA et SilA montre que ces dernières et leurs protéines périplasmiques respectives ont des affinités similaires pour les métaux lourds. De plus, les études de transport ont apportés des arguments en faveur de l’hypothèse de capture cytoplasmique du substrat par l’antiporteur, tandis que la capacité des protéines périplasmiques à fixer les métaux lourds a apporté des arguments en faveur de l’hypothèse de capture périplasmique du substrat par l’antiporteur. Les deux modes de capture pourraient en réalité coexister ;cependant, le débat autour du compartiment cellulaire de capture du substrat par l’antiporteur est complexe et requiert de plus amples efforts afin d’être cerné. / Tripartite resistance nodulation cell division (RND)-based efflux complexes are paramount for multidrug and heavy metal resistance in numerous Gram-negative bacteria. The transport of these toxic compounds out of the cell is driven by the inner membrane proton/substrate antiporter (RND protein) connected to an outer membrane protein to form an exit duct that spans the entire cell envelope. The third component, a membrane fusion protein (MFP) also called periplasmic adaptor protein, is required for the assembly of this complex. However, MFPs are also proposed to play an important active role in substrate efflux. To better understand the role of MFPs in RND-driven efflux systems, we studied ZneB (formerly HmxB) and SilB, the MFP components of the ZneCAB and SilABC heavy metal RND-driven efflux complexes from Cupriavidus metallidurans CH34. We have identified the substrate binding specificity of the proteins, showing their ability to selectively bind zinc (ZneB), or copper and silver cations (SilB). Moreover, we have solved the crystal structure of the apo- and the metal-bound forms of ZneB to 2.8 Å resolution. The structure of ZneB displays a general architecture composed of four domains characteristic of MFPs, and it reveals the metal coordination site at the very flexible interface between the β-barrel and the membrane proximal domains. Structural modifications of the protein upon zinc binding were observed in both the crystal structure and in solution, suggesting an active role of MFPs in substrate efflux possibly through binding and release. The selectivity assays of the antiporter proteins ZneA and SilA demonstrated similar specificities in relation to their cognate MFPs toward heavy metal cations. Moreover, antiporter transport assays provide evidence for cytoplasmic substrate capture by this protein, whereas MFP substrate binding provides evidence for periplasmic substrate capture. Therefore, both modes of capture might co-exist; nevertheless, the substrate capture issue is a complex topic still needing consequent efforts to understand it. / Doctorat en Sciences agronomiques et ingénierie biologique / info:eu-repo/semantics/nonPublished

Die für die Vermehrung der Paramyxoviren notwendige Freisetzung des Virusgenoms in die Wirtszelle findet nach einer Verschmelzung der Virushülle mit der Zellmembran statt. Die Membranfusion wird durch eine Konformationsänderung des membranständigen Fusionsproteins (F-Protein) der Paramyxoviren vermittelt. Der Auslöser der Strukturumwandlung des F-Proteins ist bislang unbekannt. Man nimmt an, daß eine Wechselwirkung mit dem zweiten membranständigen Protein der Hämagglutinin-Neuraminidase (HN-Protein) die Strukturumwandlung des F-Proteins induziert. Das F-Protein kann jedoch auch in Abwesenheit des HN-Proteins eine Membranfusion vermitteln. Für das Verständnis des Mechanismus der F-proteinvermittelten Fusion ist die Kenntnis der dreidimensionalen Struktur des F-Proteins notwendig. In der vorliegenden Arbeit wurden die F-Proteine der Paramyxoviren, Sendaivirus und Simianvirus 5, in fusionskompetenter Form isoliert und in kleine Lipidvesikel rekonstituiert, um deren Struktur mittels Kryoelektronenmikroskopie und Einzelpartikelanalyse aufzuklären. Die 3D-Struktur des Sendaivirus-F-Proteins konnte mit einer Auflösung von 16 Angström aufgeklärt werden. Es ist die erste 3D-Struktur des F-Proteins eines Paramyxovirus in der fusionskompetenten Form. Um geeignete Bedingungen herauszufinden, die das Auslösen der Konformationsänderung der F-Proteine bzw. das "Einfangen" von Strukturintermediaten während der Fusion ermöglichen, wurde das Fusionsverhalten von Sendaivirus und Simianvirus 5 bei unterschiedlichen Temperatur- und pH-Werten sowie in Anwesenheit von Lysolipiden mittels Fluoreszenzdequenchingassays untersucht. Ein signifikanter Anstieg der Fusionsaktivität der untersuchten Viren konnte durch eine Erhöhung der Temperatur erreicht werden. Mittels ESR-Spektroskopie unter Einsatz von spinmarkierten Lysolipiden konnte gezeigt werden, daß Lysolipide die proteinvermittelte Fusion von Hüllviren in einem späten lipidabhängigen Schritt hemmen. Diese Untersuchungen bilden damit eine Grundlage zur Aufklärung der 3D-Struktur des F-Proteins im fusionsaktiven Zustand. Desweiteren wurde die Rolle der transmembranalen und zytoplasmatischen Domäne des F-Proteins bei der Membranfusion und der Wechselwirkung mit dem HN-Protein mittels Fluoreszenzmikroskopie untersucht. Die Befunde der 3D-Strukturaufklärung und der fluoreszenzmikroskopischen Studien wurden unter anderem in Hinblick auf die Bedeutung der Wechselwirkung zwischen den F- und HN-Proteinen für die Fusion diskutiert. / Paramyxoviruses infect their host cells by fusion of the viral envelope with the cell membrane. The membrane fusion is mediated by a confomational change of a viral envelope glycoprotein called the fusion (F) protein. The trigger of the F protein conformational change is still unknown. It is suggested, that an interaction of the F protein with the second envelope glycoprotein hemagglutinin-neuraminase (HN) induces its conformational change. However the F protein can mediate membrane fusion in absense of HN. The knowledge of the three dimensional structure of the F protein is reqiured to understand the F mediated membrane fusion. In the present work the fusion competent form of the fusion proteins of the paramyxoviruses Sendai virus and Simian virus 5 were isolated and incorporated each of them into small lipid vesicles. The 3D-structure of the entire ectodomain of the Sendai virus F protein has been determined in fusion potential conformation by cryo electron microscopy of single molecules and 3D-reconstruction at a resolution of 16 Angström. To detect usefull conditions for triggering the conformational change of F, the fusion of Sendai virus and Simian virus 5 have been studied at different temperature and pH, respectively, using a fluorescence dequenching assay. A significant increase of virus fusion activity has been found due to temperature enhancement. Using ESR-spectroscopy and spin-labeled lysolipids it has been shown that lysolipids inhibit the protein mediated fusion of enveloped viruses at a late lipid-dependent intermediate. Thus lysolipids are capable to freeze a conformational intermediate of the F protein during fusion. Furthermore the role of the transmembrane and the cytoplasmic domain of the Sendai virus F protein for membrane fusion was investigated using fluorescence microscopy. The results of the fluorescence microscopy study and the detection of the 3D-structure have been discussed in view of the relevance of F-HN-interaction for membrane fusion.