Prion Protein Protects against Renal Ischemia/Reperfusion Injury.

The cellular prion protein (PrPC), a protein most noted for its link to prion diseases, has been found to play a protective role in ischemic brain injury. To investigate the role of PrPC in the kidney, an organ highly prone to ischemia/reperfusion (IR) injury, we examined wild-type (WT) and PrPC knockout (KO) mice that were subjected to 30-min of renal ischemia followed by 1, 2, or 3 days of reperfusion. Renal dysfunction and structural damage was more severe in KO than in WT mice. While PrP was undetectable in KO kidneys, Western blotting revealed an increase in PrP in IR-injured WT kidneys compared to sham-treated kidneys. Compared to WT, KO kidneys exhibited increases in oxidative stress markers heme oxygenase-1, nitrotyrosine, and Nε-(carboxymethyl)lysine, and decreases in mitochondrial complexes I and III. Notably, phosphorylated extracellular signal-regulated kinase (pERK) staining was predominantly observed in tubular cells from KO mice following 2 days of reperfusion, a time at which significant differences in renal dysfunction, histological changes, oxidative stress, and mitochondrial complexes between WT and KO mice were observed. Our study provides the first evidence that PrPC may play a protective role in renal IR injury, likely through its effects on mitochondria and ERK signaling pathways.

Synthetic Aß peptides acquire prion-like properties in the brain.

In transmission studies with Alzheimer's disease (AD) animal models, the formation of Aß plaques is proposed to be initiated by seeding the inoculated amyloid ß (Aß) peptides in the brain. Like the misfolded scrapie prion protein (PrPSc) in prion diseases, Aß in AD shows a certain degree of resistance to protease digestion while the biochemical basis for protease resistance of Aß remains poorly understood. Using in vitro assays, histoblotting, and electron microscopy, we characterize the biochemical and morphological features of synthetic Aß peptides and Aß isolated from AD brain tissues. Consistent with previous observations, monomeric and oligomeric Aß species extracted from AD brains are insoluble in detergent buffers and resistant to digestions with proteinase K (PK). Histoblotting of AD brain tissue sections exhibits an increased Aß immunoreactivity after digestion with PK. In contrast, synthetic Aß40 and Aß42 are soluble in detergent buffers and fully digested by PK. Electron microscopy of Aß40 and Aß42 synthetic peptides shows that both species of Aß form mature fibrils. Those generated from Aß40 are longer but less numerous than those made of Aß42. When spiked into human brain homogenates, both Aß40 and Aß42 acquire insolubility in detergent and resistance to PK. Our study favors the hypothesis that the human brain may contain cofactor(s) that confers the synthetic Aß peptides PrPSc-like physicochemical properties.

Comparative Study of Prions in Iatrogenic and Sporadic Creutzfeldt-Jakob Disease.

Differentiating iatrogenic Creutzfeldt-Jakob disease (iCJD) from sporadic CJD (sCJD) would be useful for the identification and prevention of human-to-human prion transmission. Currently, the diagnosis of iCJD depends on identification of a recognized source of contamination to which patients have been exposed, in addition to fulfilling basic requirements for the establishment of diagnosis of CJD. Attempts to identify differences in clinical manifestations, neuropathological changes and pathological prion protein (PrPSc) between iCJD and sCJD have been unsuccessful. In the present study, using a variety of more sophisticated methods including sucrose step gradient sedimentation, conformational stability immunoassay, protein misfolding cyclic amplification (PMCA), fragment-mapping, and transmission study, we show no significant differences in gel profiles, oligomeric state, conformational stability and infectivity of PrPSc between iCJD and sCJD. However, using PMCA, we find that convertibility and amplification efficiency of PrPSc is greater in iCJD than in sCJD in a polymorphism-dependent manner. Moreover, two protease-resistant PrP C-terminal fragments (termed PrP-CTF12/13) were detected in all 9 cases of sCJD but not in 6 of 8 cases of iCJD tested in this study. The use of fragment mapping- and PMCA-based assays thus provides a means to distinguish most cases of iCJD from sCJD.