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Sega Ndiaye, doctorant. Crédits : ESPCI ParisTechThe use of proteomics and mass spectrometry has become essential for understanding the molecular level of many diseases. The amyloid beta peptide (Abeta) 1-42 plays a central role in the development of Alzheimer’s disease (AD). However, the mechanisms of toxicity induced by this peptide are still unknown. This work aims to identify different proteins partners of the fibrillar form of Abeta peptide in order to gain a better understanding of the molecular mechanisms induced by this peptide and to identify possible candidates as therapeutic targets for treatment against AD. For this we have implemented a strategy of co-precipitation of proteins interacting with the peptide Abeta 1-42 fibrillar form, using proteins extracted from rat synaptosomes. Identification of proteins co-precipitated with the fibrils is achieved by LC-MS/MS (Hesse et al. 2011) (ESI-LIT-FTICR). Using six independent experiments we have identified 172 proteins that specifically co-precipitated with beta amyloïd;. Among these proteins, 11 were identified in all biological replicates Ras-related protein Ral-A, Cytochrome b-c1, amine oxidase B, 3-hydroxyacyl-CoA dehydrogenase type 2, TOM70 mitochondrial import, Dynamin-like 120 kDa protein , succinate dehydrogenase, LETM1, EF-hand domain containing protein, Up-regulated during skeletal muscle growth and protein-residue succinyltransferase component Dihydrolipoyllysine of 2-oxoglutarate dehydrogenase complex. Some of these proteins are associated in the literature to control calcium homeostasis, or the organization of microtubules, which are disturbed in AD. In order to increase this list we have developed in the laboratory the coupling between liquid chromatography and mass spectrometers equipped with a MALDI source. This coupling gives to us additional analysis opportunities (Chiappetta et al. 2010) and a complementary analysis compared to conventional way (LC-ESI). To understand the protein and peptide complementarity of these two approaches (LC-MALDI and LC-ESI) we have studied various physico-chemical factors that can induce discrimination and preferential ionization.
Keywords: Alzheimer, amyloïd-beta 1-42, synaptosomes, proteomic, ESI, MALDI, complementarity, mass spectrometry.