Proteomic consequences of expression and pathological conversion of the prion protein in inducible neuroblastoma N2a cells.

Neurodegenerative diseases are often associated with misfolding and deposition of specific proteins in the nervous system. The prion protein, which is associated with transmissible spongiform encephalopathies (TSEs), is one of them. The normal function of the cellular form of the prion protein (PrP(C)) is mediated through specific signal transduction pathways and is linked to resistance to oxidative stress, neuronal outgrowth and cell survival. In TSEs, PrP(C) is converted into an abnormally folded isoform, called PrP(Sc), that may impair the normal function of the protein and/or generate toxic aggregates. To investigate these molecular events we performed a two-dimensional gel electrophoresis comparison of neuroblastoma N2a cells expressing different amounts of PrP(C) and eventually infected with the 22L prion strain. Mass spectrometry and peptide mass fingerprint analysis identified a series of proteins with modified expression. They included the chaperones Grp78/BiP, protein disulfide-isomerase A6, Grp75 and Hsp60 which had an opposite expression upon PrPC expression and PrP(Sc) production. The detection of these proteins was coherent with the idea that protein misfolding plays an important role in TSEs. Other proteins, such as calreticulin, tubulin, vimentin or the laminin receptor had their expression modified in infected cells, which was reminiscent of previous results. Altogether our data provide molecular information linking PrP expression and misfolding, which could be the basis of further therapeutic and pathophysiological research in this field.