Apports de la biochimie et de la protéomique dans l'étude de modifications du métabolisme cellulaire à travers deux exemples : l'amyloïdogénèse de différentes protéïnes de champignons ascomycètes et la caractérisation du protéome d'une plante invasive résistante à un stress environnemental

Abstract : A number of neurodegenerative illnesses such as Creutzfeld-Jacob disease in humans or the disease known as mad cow disease in bovine, are due to misfolding of a cellular protein called prion. These proteins are not pathogenic for human and can form amyloid fibers like mammalian prion. They are therefore a useful tool to study molecular events responsible for the emergence and propagation of prions. In S. cerevisiae, the Ure2p protein is associated with [URE3] prion phenotype and is aggregated in this cell. Initially, I developed the conditions to characterize Ure2p amyloid fibers by proteolysis and we showed that [URE3] aggregates obtained in vivo were different than amyloid fibers produced in vitro. In a second phase, the technicity acquired during the biochemical study of Ure2p allowed me to approach the study of an ortholog, Saccharomyces paradoxus Ure2p (Ure2p-Sp), which is not an "in vivo" prion. After showing that soluble forms of the two proteins have the same biochemical characteristics, I show that they have the same propensity to form amyloid fibers. In this study we show that these fibers are infectious in vivo, suggesting that the incapacity of Ure2p-Sp protein to switch into a prion form is rather due to a failure in prion propagation mechanism rather than differences in amyloid structure itself. Then using all technologies that I introduced in the laboratory, I studied the relationship between amyloid structure and toxicity in S. cerevisiae. We showed that it was possible to transform a non-toxic amyloid protein in a toxic form by changing only a few numbers of amino acids. An in vitro study has also shown that the toxic protein was organized into short amyloid fibers that could mimic the intermediates responsible for toxicity in neurodegenerative diseases. The last chapter of this manuscript focuses on research that I developed in the Laboratory of Ecotoxicology Interactions, Biodiversity, Ecosystems, Metz. Within this laboratory, we aim at identifying effects of disturbances and physico-chemical analysis of the mechanisms involved at different scales of observation, from organisms to ecosystems. Progress in genomes sequencing allows an exceptional development in post-genomic biochemistry and can highlight new proteins through functional studies. In order to better understand molecular events responsible for these responses, I introduce a differential technique of proteomics: a DiGE two-dimensional electrophoresis (Differential In-Gel Electrophoresis). I developed this technics in a proteome study of an invasive plant, the goldenrod Solidago canadensis, under metal stress. This proteomic study supplements a phyto-sociological study of plants competent in colonizing a very poor soil but also of biodiversity data, growth and measures of the antioxidant response of these plants. This analysis revealed that in polluted soils, the goldenrod achieves not only to produce energy for its growth but it also achieves to biosynthesize intermediates of glutathion and phytochelatins. Thus, the goldenrod is able to adapt to its environment, which allows it to be tolerant to pollution. My first results of post-genomic biochemistry provide new bases for understanding the molecular mechanisms behind environmental tolerances. These studies may help us to identify the most adapted plants to these environments and why they are. They may help us to understand the effects of these pollutants and allow the development of innovative technologies for phytoremediation to restore polluted soils
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http://docnum.univ-lorraine.fr/prive/DDOC_T_2013_0297_TORTEROTOT_IMMEL.pdf
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Submitted on : Thursday, March 29, 2018 - 12:51:27 PM
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Françoise Torterotot-Immel. Apports de la biochimie et de la protéomique dans l'étude de modifications du métabolisme cellulaire à travers deux exemples : l'amyloïdogénèse de différentes protéïnes de champignons ascomycètes et la caractérisation du protéome d'une plante invasive résistante à un stress environnemental. Biochimie, Biologie Moléculaire. Université de Lorraine, 2013. Français. ⟨NNT : 2013LORR0297⟩. ⟨tel-01750650⟩

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