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The link between altered glucosylceramide composition and membrane properties : from membrane biophysics to gaucher disease
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Resumo(s)
Lipids are one of the most abundant molecules in a cell and are involved in the regulation of cell events. One of the mechanisms by which lipids control cell signaling is by altering membrane biophysical properties. Therefore, the biophysical properties of several lipids have been thoroughly characterized. However, some bioactive lipids like glucosylceramide (GlcCer) still have their properties poorly studied. GlcCer is a lipid involved in several cell processes. A deregulation in its metabolism triggers damaging signaling pathways ultimately leading to the development of a pathologic state, such as Gaucher Disease (GD). This disease results from the abnormal accumulation of GlcCer in cells, mainly in the lysosomes. Even though the biochemistry and biology context of GD is a subject of intensive research, the molecular mechanisms that underlie this disease remain elusive, likely due to the inherent complexity and heterogeneity of the disease. An underexplored branch of research, related to the understanding of the biophysical impact of increased levels of GlcCer in biological membranes, might provide additional insight into the mechanisms underlying this complex disease. Therefore, research that aims to characterize the biophysical features of GlcCer and its interaction with other membrane lipids is required. Using complementary techniques, including fluorescence microscopy and spectroscopy, a thorough biophysical characterization of GlcCer was performed. This comprised the study of the effect of increasing molar fractions of GlcCer in the biophysical properties and morphology in a variety of model membranes containing different lipid composition, as well as in wild type and Gaucher Diseasederived fibroblasts. Since GlcCeris present at higher abundance in the plasma membrane (PM) and in the lysosome, the studies were performed in conditions mimicking the pH environment of those cellular sites. This detailed study revealed that: I) GlcCer increases the order of fluid membranes, II) GlcCer promotes membrane morphological alterations, such as tubules, III) GlcCer effect in membrane properties is pH sensitive, promoting an higher packing at neutral pH, IV) GlcCer impact in the membrane is modulated by cholesterol (Chol) in a concentration dependent manner, V) fibroblasts from GD patients, which are enriched in GlcCer, have a higher global membrane order in comparison to wild type fibroblasts, coherent with the observations in model membranes. These conclusions indicate that GlcCer accumulation in cells alter the biophysical properties of its membranes, possibly affecting protein activity and trafficking. These alterations could underlie some of the effects triggered by GlcCer that might contribute to the development of Gaucher Disease.
Descrição
Tese de doutoramento, Farmácia (Tecnologia Farmacêutica), Universidade de Lisboa, Faculdade de Farmácia, 2015
Palavras-chave
Teses de doutoramento - 2015