Trafic de la protéine prion dans les cellules MDCK polarisées

Abstract : The Prion Protein (PrP) is a ubiquitously expressed glycosylated membrane protein attached to the external leaflet of the plasma membrane via a glycosylphosphatidylinositol anchor (GPI). While the misfolded PrPSc scrapie isoform is the infectious agent of “prion diseases” the cellular isoform (PrPC) is an enigmatic protein with unclear function. Prion protein has received considerable attention due to its central role in the development of Transmissible Spongiform Encephalopathies (TSEs) known as “prion diseases”, in animals and humans. Understanding the trafficking, the processing and degradation of PrP is of fundamental importance in order to unravel the mechanism of PrPSc mediated pathogenesis, its spreading and cytotoxicity. The available data regarding PrP trafficking are contradictory. To investigate PrP trafficking and sorting we used polarized MDCK cells (two-dimensional and tree-dimensional cultures) where the intracellular traffic of GPI-anchored proteins (GPI-APs) is well characterized. GPI-APs that are sorted in the Trans Golgi Network follow a direct route from the Golgi apparatus to the apical plasma membrane. The exception to direct apical sorting of native GPI-APs in MDCK cells is represented by the Prion Protein. Of interest, PrP localization in polarized MDCK cells is highly controversial and its mechanism of trafficking is not clear. We found that full-length PrP and its cleavage fragments are segregated in different domains of the plasma membrane in polarized cells in both 2D and 3D cultures and that the C1/PrP full-length ratio increases upon MDCK polarization. We revealed that differently from other GPI-APs, PrP undergoes basolateral-to-apical transcytosis in fully polarized MDCK cells and is α-cleaved during its transport to the apical surface. This study not only reconciles and explains the different findings in the previous literature but also provides a better picture of PrP trafficking and processing, which has been shown to have major implications for its role in prion disease.
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Alexander Arkhipenko. Trafic de la protéine prion dans les cellules MDCK polarisées. Médecine humaine et pathologie. Université Paris-Saclay, 2015. Français. ⟨NNT : 2015SACLS228⟩. ⟨tel-01424172⟩

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