No description available.

Cerca de 20 % dos casos familiares de esclerose lateral amiotrófica (ELAf) são causados por mutações na enzima Cu,Zn-superóxido dismutase (SOD1). Inicialmente se supôs que as enzimas mutantes teriam a atividade SOD comprometida, entretanto isto não foi comprovado. Atualmente, considera-se que as enzimas mutantes adquiram propriedades tóxicas. Quais seriam estas propriedades e como levariam à degeneração do neurônio motor são questões ainda não respondidas. Neste trabalho, comparamos neuroblastomas humanos transfectados com SOD1 G93A associada à ELAf (SH-SY5YG93A), e SOD1 selvagem (SH-SY5YWT) com células parentais (SH-SY5Y) em relação ao crescimento, viabilidade, produção basal de oxidantes, atividades SOD e peroxidásica e modificações estruturais da SOD. As células transfectadas apresentaram aumento na taxa de crescimento e na produção basal de oxidantes. As células SH-SY5YWT e SH-SY5YG93A mantiveram a expressão de SOD1 e atividade consistente com o aumento esperado de duas vezes, em estágios iniciais de cultura. A atividade peroxidásica do homogenato da célula SH-SY5YG93A foi maior. Após quatro semanas, a linhagem SH-SY5YG93A manteve a expressão de SOD1, mas as atividades dismutásica e peroxidásica diminuíram. A expressão de SOD1 aumentou a proporção de formas alteradas de SOD1, como enzima reduzida, multímeros formados por ponte dissulfeto e formas insolúveis em detergente, particularmente na linhagem SH-SY5YG93A. Entre estas formas insolúveis, identificamos um dímero covalente de SOD. Estas formas alteradas provavelmente são responsáveis pela ativação do proteassomo e estresse do retículo endoplasmático, verificados nas células transfectadas. Concluindo, a superexpressão da SOD1 foi suficiente para elevar as formas imaturas e oligomerizadas de SOD1 e a oxidação basal, e a mutação G93A ressaltou estes processos. / Some familial ALS (fALS) are caused by mutations in the Cu,Zn-superoxide dismutase enzyme (SOD1). It was thought that the mutated enzymes would have impaired SOD activity, but this has not been corroborated so far. Presently, it is more accepted that the mutated enzymes acquire a new toxic function. What this new toxic function is and how it relates to the degeneration of motor neurons remains debatable. Here, we compared human neuroblastoma cells transfected with fALS mutant G93A (SH-SY5YG93A) or wild-type SOD1 (SH-SY5YWT) with parent cells (SH-SY5Y) in regard to growth, viability, basal oxidant production, SOD and peroxidase activities, and SOD forms. Transfected cells presented increased growth rate and basal oxidant production. SH-SY5YWT and SH-SY5YG93A cells in early culture stage showed SOD expression and activity consistent with the expected two-fold increase; SH-SY5YWT homogenates showed increased peroxidase activity. After four weeks, SH-SY5YG93A maintained SOD1 expression levels but peroxidase and dismutase activities were lower. SOD1 expression increased the levels of altered SOD1 forms such as the reduced enzyme, disulfide multimers and detergent-insoluble forms, particularly in SH-SY5YG93A cells. Among the insoluble forms a covalent SOD dimer was identified. These altered SOD forms are probably responsible for proteasome activation and endoplasmatic reticulum stress response verified in transfected cells. In conclusion, SOD1 over-expression was sufficient to increase intracellular immature and oligomerized SOD1 forms and basal oxidation and the G93A mutation enhanced these processes.

Die erfolgreiche Synthese und Faltung von Proteinen ist eine Voraussetzung der Zellfunktion und ein Versagen der Proteinhomöostase führt zu Krankheit oder Tod. In der Zelle sichern molekulare Chaperone die korrekte Faltung der Proteine oder tragen zur Entsorgung unwiederbringlich fehlgefalteter Proteinsubstrate bei. Unter diesen Chaperonen sind kleine Hitzeschockproteine (sHsp) ein ATP-unabhängiger Teil des Proteostasenetzwerks. In dieser Arbeit habe ich das bisher wenig erforschte sHsp HSP-17 aus C. elegans untersucht. Im Gegensatz zu anderen sHsps zeigte HSP-17 nur eine geringe Aktivität beim Verhindern der Aggregation von Proteinsubstraten. Stattdessen konnte ich in vitro zeigen, dass HSP-17 die Aggregation von Modellsubstraten fördert, was hier für Metazoen-sHsps erstmals gezeigt wurde. HSP-17 kopräzipitiert mit Substraten und modifiziert deren Aggregate möglicherweise. HSP-17 kolokalisiert in vivo mit Aggregaten, und seine aggregationsfördernde Aktivität konnte ich für das physiologische Substrat KIN-19 und heterolog exprimierte polyQ-Peptide validieren. Durch ex vivo Analysen konnte ich zeigen, dass die Aktivität von HSP-17 für die Fitness relevant ist  In einem zweiten Projekt habe ich zur Entwicklung eines neuen Modelles für Aß-Pathologie in C. elegans beigetragen, welches substöchiometrische Markierungen verwendet, um eine zeitnahe Visualisierung der Aß-Aggregation in spezifischen Zelltypen zu ermöglichen. Das Modell spiegelt bekannte Phänotypen der Aß-Proteotoxizität aus Menschen und bestehenden C. elegans Aß-Stämmen wider. Interessanterweise zeigt eine Untergruppe der Neuronen, die IL2-Neuronen, eine höhere Anfälligkeit für die Aggregation und Proteotoxizität von Aß1-42. Eine gezielte Reduktion von Aß1-42 in IL2 Neuronen führt zu einer systemischen Reduktion der Pathologie. Somit bietet das Modell eine neue Plattform, um die Bedeutung molekularer Chaperone, wie z. B. der sHsps, für Amyloidosen zu untersuchen, auch im Hinblick auf menschliche Erkrankungen. / Successful synthesis and folding of proteins is a prerequisite for cellular function and failure of protein homeostasis leads to disease or death. Within the cell, molecular chaperones ensure correct protein folding or aid in the disposal of terminally misfolded protein substrates. Among these chaperones, small heat shock proteins (sHsps) are ATP-independent members of the proteostasis network. In this work, I analyzed the so far under-researched C. elegans sHsp HSP-17. Unlike other sHsps, HSP-17 exhibited only weak activity in preventing aggregation of protein substrates. Instead, I could show in vitro that HSP-17 can promote the aggregation of protein substrates, which is the first demonstration for metazoan sHsps. HSP-17 co-precipitates with substrates and potentially modifies the aggregates.  HSP-17 colocalizes with aggregates and pro-aggregation activity is present in vivo, which I demonstrated for the physiological substrate KIN-19 and heterologously expressed amyloidogenic polyQ peptides. By physiological, biochemical and proteomic analysis I showed that HSP-17 activity is relevant for organismal fitness In a second project, I contributed to the development and characterization of a novel model of Aß pathology in C. elegans. This new AD model employs sub-stoichiometric labeling to allow live visualization of Aß aggregation in distinct cell types. The model mirrors known phenotypes of Aß proteotoxicity in humans and existing C. elegans Aß strains. Interestingly, a subset of neurons, the IL2 neurons, is shown to be more vulnerable to Aß proteotoxicity and targeted depletion of Aß in these neurons systemically ameliorates pathology. Thereby, the model presents a new platform to assess the relevance of molecular chaperones such as sHsps in amyloidosis with a perspective on human disease.

<p>QC 20110615</p>

Biologiska läkemedel har under det senaste århundradet utökats, och under de senaste 25 åren så har proportionen av godkända biologiska läkemedel har ökat för behandlingen av sjukdomar, vaccin, och diagnostik. Det finns flera olika mekanismer för protein aggregering, och en av dessa är seeding, vilket innebär aggregering inducerat av tillsatta aggregat eller förekomsten av strukturförändringar i proteinet. I detta examensarbete har två terapeutiska proteiner, Somatropin och en monoklonal antikropp, studerats i form av aggregering. Denna studie har utförts genom att värma en del av proteinlösningen för att bilda aggregat och strukturförändrat protein, och sedan blanda detta med nativt protein till olika volymprocent. Dessa lösningar förvarades i olika temperaturer, 4°C, RT och 40°C för att undersöka temperaturberoendet. Med Dynamic Light Scattering (DLS) mättes storleksfördelningen och medelstorleken på proteinet, vilket visade att de seedade proverna ökade i medelstorlek med tiden. Detta indikerar att seedingen inducerade aggregering med tiden. / Biological pharmaceuticals have expanded their use over the last decade, and during the recent 25 years, the proportion of approved biologics has increased for the treatment of diseases, vaccines, and diagnostics. There are several aggregation mechanisms, and one is seeding, i.e., aggregation induced by pre-formed aggregates or the presence of conformational changed proteins. In this master thesis, two therapeutic proteins, Somatropin and one monoclonal antibody have been studied in terms of aggregation. The study has been performed by heating a part of a protein solution to induce aggregation and mixing this with native protein in different volume percentages. These were stored in different temperatures, 4°C, RT, and 40°C, to investigate the temperature dependence. With Dynamic light scattering (DLS), the size distribution and the average-sized particles were measured. This showed that there was a growth of average size in the seeded samples with time. This indicates that the seeding induced aggregation with time.

Proteins are the center of all biochemical reactions in living organisms. Proteins need to be present at the right time, in the right place, with the correct concentration and have the right shape to carry their designated function. Protein homeostasis is when all proteins in the proteome are in functional balance, and such balance is maintained by synthesis, folding, and degradation machinery. When protein homeostasis is lost, organisms start to age and develop diseases. To truly unveil disease mechanisms and provide more efficient means for treatment and prevention, we need a holistic understanding of the mechanism of protein homeostasis. Currently, most biomarker studies focus on the quantity aspect of the proteome. The quality aspect has been neglected because of the difficulties in measuring quality in vivo with cellular context retained. This work first proposes a kinetic model of protein homeostasis, which can provide a holistic view, including both quantity and quality aspects, as well as monitor the complex protein interactions. Using mass spectrometry, the model quantifies the quality of proteome by linking the concentration of protein, mRNA, and the rate protein synthesis, folding, unfolding, misfolding, refolding, degradation of the correctly folded protein, and degradation of protein aggregation. We then applied the ideas within the kinetic model of protein homeostasis to study several proteins in human blood serum. We reviewed the current known mechanism of transthyretin mediated amyloidosis and proposed a study approach that can measure the quality difference between different transthyretin's mutation stages, as well as monitor if the transthyretin amyloidosis has been developed at the early stage. We also used mass-spectrometry to quantify the surface accessibility differences in human serum albumin (HSA) between patients with and without rheumatoid arthritis (RA). We found certain residues are less reactive in the RA group, indicating a structural change in HSA. Such structural changes, possibly caused by ligand binding, stabilized HSA and explained the heat denature curve shift we observed. In the end, we introduced a novel assay, Iodination Protein Stability Assay (IPSA). IPSA is used to quantify protein quality by measuring protein folding stability. We applied IPSA to human serum, and it is the first in situ study, to our best knowledge, that measure the protein folding stability of proteins from human serum. We confirmed that IPSA is sensitive to measuring the differences in protein folding stability between transferrin's different iron-binding states. Together, this dissertation conveys the importance of adding quality aspects to current quantity-focused research in curing diseases and improving the quality of human life.

A inibição do transporte axonal é um evento que ocorre prematuramente no curso das doenças neurodegenerativas, inclusive antes da formação dos agregados proteicos, os quais estariam envolvidos no processo fisiopatológico das doenças neurodegenerativas. No presente estudo avaliou-se a hipótese de que alterações no transporte de mitocôndrias ocorrem antes da formação dos agregados proteicos envolvidos em neurodegeneração, devido a desregulação dos níveis citoplasmáticos de Ca2+ e o envolvimento da modulação do transporte mitocondrial provido pela proteína Miro neste cenário. Utilizaram-se dois modelos experimentais: o primeiro utilizando a exposição à rotenona em culturas primárias de neurônios do locus coeruleus, hipocampo e substância negra de ratos, e o segundo utilizando neurônios derivados de células tronco de pluripotência induzida (iPSC), isogênicas humanas contendo mutações que levam à deleção do exon 9 da (deltaE9) no gene da presenilina 1 (PS1), o qual apresenta aumento da síntese do peptídeo beta-amiloide com 42 aminoácidos (Abeta42), sem a formação de agregados proteicos. Os resultados mostram disfunções nos níveis citoplasmáticos de Ca2+ em ambos modelos. A mobilidade mitocondrial alterou-se no hipocampo, locus coeruleus e substância negra após exposição à rotenona. No entanto, a direção das alterações observadas não se correlacionaram com os níveis de Ca2+, de acordo com o já descrito na literatura. Não houve alteração da mobilidade mitocondrial, nem nos níveis de Miro1, nos neurônios derivados de iPSC. Em conclusão, o presente estudo demonstrou que alterações nos níveis citoplasmáticos de Ca2+ ocorrem antes e durante a formação de agregados proteicos, o que pode ser importante para a etiologia de doenças neurodegenerativas. Foi também demonstrado que mudanças na mobilidade mitocondrial, acompanhadas por alterações nas concentrações intracelulares de Ca2+, em níveis fisiológicos, ocorrem de forma independente dos níveis da proteína Miro1 em culturas de células. Porém são necessários novos estudos a fim de relacionar alterações na mobilidade mitocondrial e a indução da neurodegeneração / The axonal transport impairment occurs early in neurodegenerative diseases, even before the formation of protein aggregates, which are related with the neuropathophysiology mechanism in neurodegenerative diseases. In this study, we evaluate the hypothesis that disruptions in mitochondria transport occurs before the formation of protein aggregate related with neurodegeneration, triggered by dysregulations in cytosolic Ca2+ levels and the involvement of Miro Ca2+ dependent mechanism of mitochondria trafficking modulation. We employed two experimental models, first using rotenone exposure in primary neuronal cell cultures from locus coeruleus, substantia nigra and hippocampus of newborn rats. Second, using isogenic human neurons derived from induced pluripotent stem cells (iPSCs), harboring mutations, those induce exon 9 deletion (deltaE9) in Presenilin 1 (PS1) gene, and showing increased synthesis of amyloid beta peptide with 42 amino acids (betaA42) without the formation of protein aggregates. We found abnormalities in cytosolic Ca2+ levels in both experimental models, mitochondria trafficking were altered in hippocampus, substantia nigra and locus coeruleus. However, the pattern of mitochondria trafficking alterations did not correlate with cytosolic Ca2+ levels, accordingly with the data that was already published. We did not find alterations in mitochondria trafficking or Miro1 levels in neurons derived from iPSC. In conclusion, our finds demonstrated aberrant cytosolic Ca2+ levels before and during protein aggregation, which may be important for the etiology of neurodegenerative diseases. In addition, this dysfunction in mitochondria trafficking happens after changes in cytosolic Ca2+ levels, in physiological range, independent of Miro1 levels in primary neurons cell cultures. Therefore, new studies need to be done, aiming to elucidate the relation between mitochondria trafficking dysfunctions and the induction of neurodegeneration process.

No description available.

A inibição do transporte axonal é um evento que ocorre prematuramente no curso das doenças neurodegenerativas, inclusive antes da formação dos agregados proteicos, os quais estariam envolvidos no processo fisiopatológico das doenças neurodegenerativas. No presente estudo avaliou-se a hipótese de que alterações no transporte de mitocôndrias ocorrem antes da formação dos agregados proteicos envolvidos em neurodegeneração, devido a desregulação dos níveis citoplasmáticos de Ca2+ e o envolvimento da modulação do transporte mitocondrial provido pela proteína Miro neste cenário. Utilizaram-se dois modelos experimentais: o primeiro utilizando a exposição à rotenona em culturas primárias de neurônios do locus coeruleus, hipocampo e substância negra de ratos, e o segundo utilizando neurônios derivados de células tronco de pluripotência induzida (iPSC), isogênicas humanas contendo mutações que levam à deleção do exon 9 da (deltaE9) no gene da presenilina 1 (PS1), o qual apresenta aumento da síntese do peptídeo beta-amiloide com 42 aminoácidos (Abeta42), sem a formação de agregados proteicos. Os resultados mostram disfunções nos níveis citoplasmáticos de Ca2+ em ambos modelos. A mobilidade mitocondrial alterou-se no hipocampo, locus coeruleus e substância negra após exposição à rotenona. No entanto, a direção das alterações observadas não se correlacionaram com os níveis de Ca2+, de acordo com o já descrito na literatura. Não houve alteração da mobilidade mitocondrial, nem nos níveis de Miro1, nos neurônios derivados de iPSC. Em conclusão, o presente estudo demonstrou que alterações nos níveis citoplasmáticos de Ca2+ ocorrem antes e durante a formação de agregados proteicos, o que pode ser importante para a etiologia de doenças neurodegenerativas. Foi também demonstrado que mudanças na mobilidade mitocondrial, acompanhadas por alterações nas concentrações intracelulares de Ca2+, em níveis fisiológicos, ocorrem de forma independente dos níveis da proteína Miro1 em culturas de células. Porém são necessários novos estudos a fim de relacionar alterações na mobilidade mitocondrial e a indução da neurodegeneração / The axonal transport impairment occurs early in neurodegenerative diseases, even before the formation of protein aggregates, which are related with the neuropathophysiology mechanism in neurodegenerative diseases. In this study, we evaluate the hypothesis that disruptions in mitochondria transport occurs before the formation of protein aggregate related with neurodegeneration, triggered by dysregulations in cytosolic Ca2+ levels and the involvement of Miro Ca2+ dependent mechanism of mitochondria trafficking modulation. We employed two experimental models, first using rotenone exposure in primary neuronal cell cultures from locus coeruleus, substantia nigra and hippocampus of newborn rats. Second, using isogenic human neurons derived from induced pluripotent stem cells (iPSCs), harboring mutations, those induce exon 9 deletion (deltaE9) in Presenilin 1 (PS1) gene, and showing increased synthesis of amyloid beta peptide with 42 amino acids (betaA42) without the formation of protein aggregates. We found abnormalities in cytosolic Ca2+ levels in both experimental models, mitochondria trafficking were altered in hippocampus, substantia nigra and locus coeruleus. However, the pattern of mitochondria trafficking alterations did not correlate with cytosolic Ca2+ levels, accordingly with the data that was already published. We did not find alterations in mitochondria trafficking or Miro1 levels in neurons derived from iPSC. In conclusion, our finds demonstrated aberrant cytosolic Ca2+ levels before and during protein aggregation, which may be important for the etiology of neurodegenerative diseases. In addition, this dysfunction in mitochondria trafficking happens after changes in cytosolic Ca2+ levels, in physiological range, independent of Miro1 levels in primary neurons cell cultures. Therefore, new studies need to be done, aiming to elucidate the relation between mitochondria trafficking dysfunctions and the induction of neurodegeneration process.

<div>Large protein molecules are abundant in biological cells but are very difficult to study in physiological conditions due to molecular disorder. For large proteins, most structural information is obtained in crystalline states which can be achieved in certain conditions at very low temperature. X-ray and neutron crystallography methods can then be used for determination of crystalline structures at atomic level. However, in solution at room or physiological temperatures such highly resolved descriptions cannot be obtained except in very few cases. Scattering methods that can be used to study this type of structures at room temperature include small-angle x-ray and neutron scattering. These methods are used here to study two distinct proteins that are both classified as glycoproteins, which are a large class of proteins with diverse biological functions. In this study, two specific plasma glycoproteins were used: Fibrinogen (340 kDa) and Alpha 1-Antitrypsin or A1AT (52 kDa). These proteins have been chosen based on the fact that they have a propensity to form very large molecular aggregates due to their tendency to polymerize. One goal of this project is to show that for such complex structures, a combination of scattering methods that include SAXS, SANS, and DLS can address important structural and interaction questions despite the fact that atomic resolution cannot be obtained as in crystallography. A1AT protein has been shown to have protective roles of lung cells against emphysema, while fibrinogen is a major factor in the blood clotting process. A systematic approach to study these proteins interactions with lipid membranes and other proteins, using contrast-matching small-angle neutron scattering (SANS), small angle x-ray scattering (SAXS) and dynamic light scattering (DLS), is presented here. A series of structural reference points for each protein in solution were determined by performing measurements under osmotic stress controlled by the addition of polyethylene glycol-1,500 MW (PEG 1500) in the samples. Osmotic pressure changes the free energy of the molecular mixture and has consequences on the structure and the interaction of molecular aggregates. In particular, the measured radius of gyration (Rg) for A1AT shows a sharp structural transition when the concentration of PEG 1500 is between 33 wt\% and 36 wt\%. Similarly, a significant structural change was observed for fibrinogen when the concentration of PEG 1500 was above 40 wt\%. This analysis is applied to a study of A1AT interacting with lipid membranes and to a study of fibrinogen polymerization in the presence of the enzyme thrombin, which catalyzes the formation of blood clots. The experimental approach presented here and the applications to specific questions show that an appropriate combination of scattering methods can produce useful information on the behavior and the interactions of large protein systems in physiological conditions despite the lower resolution compared to crystallography.</div>