Intracellular accumulation of a mild-denatured monomer of the human PrP fragment 90-231, as possible mechanism of its neurotoxic effects.
Because of high tendency of the prion protein (PrP) to aggregate, the exact PrP isoform responsible for prion diseases as well as the pathological mechanism that it activates remains still controversial. In this study, we show that a pre-fibrillar, monomeric or small oligomeric conformation of the human PrP fragment 90-231 (hPrP90-231), rather than soluble or fibrillar large aggregates, represents the neurotoxic species. In particular, we demonstrate that monomeric mild-denatured hPrP90-231 (incubated for 1 h at 53 degrees C) induces SH-SY5Y neuroblastoma cell death, while, when structured in large aggregates, it is ineffective. Using spectroscopic and cellular techniques we demonstrate that this toxic conformer is characterized by a high exposure of hydrophobic regions that favors the intracellular accumulation of the protein. Inside the cells hPrP90-231 is mainly compartmentalized into the lysosomes where it may trigger pro-apoptotic 'cell death' signals. The PrP toxic conformation, which we have obtained inducing a controlled in vitro conformational change of the protein, might mimic mild-unfolding events occurring in vivo, in the presence of specific mutations, oxidative reactions or proteolysis. Thus, in light of this model, we propose that novel therapeutic strategies, designed to inhibit the interaction of the toxic PrP with the plasmamembrane, could be beneficial to prevent the formation of intracellular neurotoxic aggregates and ultimately the neuronal death.
Chiovitti
Katia
K
Department of Biomedical Sciences, Section of Biochemistry, University G. D'Annunzio of Chieti, Italy.
Corsaro
Alessandro
A
Thellung
Stefano
S
Villa
Valentina
V
Paludi
Domenico
D
D'Arrigo
Cristina
C
Russo
Claudio
C
Perico
Angelo
A
Ianieri
Adriana
A
Di Cola
Domenico
D
Vergara
Alberto
A
Aceto
Antonio
A
Florio
Tullio
T
D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D006358:Hot Temperature / Q000009:adverse effects; D006801:Humans; D007424:Intracellular Fluid / Q000737:chemistry / Q000187:drug effects / Q000378:metabolism*; D009498:Neurotoxins / Q000032:analysis / Q000378:metabolism* / Q000633:toxicity*; D010446:Peptide Fragments / Q000032:analysis / Q000378:metabolism* / Q000633:toxicity*; D011328:Prions / Q000032:analysis / Q000378:metabolism* / Q000633:toxicity*; D011489:Protein Denaturation / Q000502:physiology; D020033:Protein Isoforms / Q000032:analysis / Q000378:metabolism / Q000633:toxicity
D009498:Neurotoxins; D010446:Peptide Fragments; D011328:Prions; D020033:Protein Isoforms; C507417:prion protein (90-231)