NR AWKB
AU Mehlhase,J.; Hammann,J.; Löwer,J.; Montrasio,F.
TI Possible prevention of cytosolic prion protein-induced neurotoxicity by HSC70-mediated translocation of cytosolic prion protein into EEA1-positive vesicles
QU International Conference - Prion 2006: Strategies, advances and trends towards protection of society - 3.10.-6.10.2006, Torino, Italy, Lingotto Conference Centre - Poster sessions CE-31
PT Konferenz-Poster
AB The molecular mechanisms of prion-mediated neurodegeneration are not yet fully understood. In the recent past, it has been proposed that neuronal death might be triggered by cytosolic accumulation of misfolded cellular prion protein (PrPc) due to impairment of proteasomal degradation. Cytosolic PrPc could result from either retrotranslocation via the endoplasmatic reticulum-associated degradation system (ERAD) or abortive translocation of PrPc into the ER. Indeed, expression of cytosolic PrPc both in vivo and in vitro was shown to be neurotoxic. However, conflicting results on cytosolic PrPcmediated neurotoxicity in cultured cells have been reported. In order to investigate the molecular mechanisms of cytosolic PrPc-mediated cytotoxicity, a process which may play a central role in the pathogenesis of prion diseases, we performed a detailed analysis of N2a cells conditionally expressing cytosolic PrPc (Cy-PrP(aa23-231)). We found that Cy-PrP expression per se is not sufficient to trigger cytotoxicity in N2a cells independently of proteasome inhibition. Furthermore, we show that Cy-PrP is degraded with kinetics resembling the degradation of cell membrane-anchored full length PrPc and that the 20/26S proteasomal system is responsible for Cy-PrP degradation but not for that of full length PrPc. Interestingly, Cy-PrP accumulates in fine foci when expressed at high levels and colocalises with the cytosolic chaperone Hsc70 in EEA-1 positive endocytic vesicles. We therefore propose that the chaperone Hsc70 acts as a regulator for the controlled formation of amorphous Cy-PrP aggregates and their transport to endosomal/lysosomal vesicles. This Hsc70dependent mechanism may confer protection to N2a cells against cytoplasmatic toxic accumulation of Cy-PrP.
AD Prion Research Group, Paul-Ehrlich-Institute,Langen, Germany. E-mail: monfa@pei.de
SP englisch
PO Italien