Human PrP90-231-induced cell death is associated with intracellular accumulation of insoluble and protease-resistant macroaggregates and lysosomal dysfunction

Cell Death Dis. 2011 Mar 31;2(3):e138. doi: 10.1038/cddis.2011.21.


To define the mechanisms by which hPrP90-231 induces cell death, we analyzed its interaction with living cells and monitored its intracellular fate. Treatment of SH-SY5Y cells with fluorescein-5-isothiocyanate (FITC)-conjugated hPrP90-231 caused the accumulation of cytosolic aggregates of the prion protein fragment that increased in number and size in a time-dependent manner. The formation of large intracellular hPrP90-231 aggregates correlated with the activation of apoptosis. hPrP90-231 aggregates occurred within lysotracker-positive vesicles and induced the formation of activated cathepsin D (CD), indicating that hPrP90-231 is partitioned into the endosomal-lysosomal system structures, activating the proteolytic machinery. Remarkably, the inhibition of CD activity significantly reduced hPrP-90-231-dependent apoptosis. Internalized hPrP90-231 forms detergent-insoluble and SDS-stable aggregates, displaying partial resistance to proteolysis. By confocal microscopy analysis of lucifer yellow (LY) intracellular partition, we show that hPrP90-231 accumulation induces lysosome destabilization and loss of lysosomal membrane impermeability. In fact, although control cells evidenced a vesicular pattern of LY fluorescence (index of healthy lysosomes), hPrP90-231-treated cells showed diffuse cytosolic fluorescence, indicating LY diffusion through damaged lysosomes. In conclusion, these data indicate that exogenously added hPrP90-231 forms intralysosomal deposits having features of insoluble, protease-resistant aggregates and could trigger a lysosome-mediated apoptosis by inducing lysosome membrane permeabilization, followed by the release of hydrolytic enzymes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Apoptosis*
  • Cell Death
  • Cell Line, Tumor
  • Cytosol / chemistry
  • Cytosol / metabolism
  • Endopeptidase K / metabolism*
  • Humans
  • Lysosomes / chemistry
  • Lysosomes / metabolism*
  • PrPC Proteins / chemistry*
  • PrPC Proteins / genetics
  • PrPC Proteins / metabolism*
  • Prion Diseases / genetics
  • Prion Diseases / metabolism*
  • Prion Diseases / physiopathology
  • Solubility


  • PrPC Proteins
  • Endopeptidase K