Fantasy of a "virus" from the inorganic world: pathogenesis of cerebral amyloidoses by polymer nucleating agents and/or "viruses"

The cellular prion protein and its role in Alzheimer disease

The cellular prion protein (PrP(C)) is a membrane-bound glycoprotein especially abundant in the central nervous system (CNS). The scrapie prion protein (PrP(Sc,) also termed prions) is responsible of transmissible spongiform encephalopathies (TSE), a group of neurodegenerative diseases which affect humans and other mammal species, although the presence of PrP(C) is needed for the establishment and further evolution of prions. The present work compares the expression and localization of PrP(C) between healthy human brains and those suffering from Alzheimer disease (AD). In both situations we have observed a rostrocaudal decrease in the amount of PrP(C) within the CNS, both by immunoblotting and immunohistochemistry techniques. PrP(C) is higher expressed in our control brains than in AD cases. There was a neuronal loss and astogliosis in our AD cases. There was a tendency of a lesser expression of PrP(C) in AD cases than in healthy ones. And in AD cases, the intensity of the expression of the unglycosylated band is higher than the di- and monoglycosylated bands. With regards to amyloid plaques, those present in AD cases were positively labeled for PrP(C), a result which is further supported by the presence of PrP(C) in the amyloid plaques of a transgenic line of mice mimicking AD. The work was done according to Helsinki Declaration of 1975, and approved by the Ethics Committee of the Faculty of Medicine of the University of Navarre.

Spontaneous generation of infectious nucleating amyloids in the transmissible and nontransmissible cerebral amyloidoses

The unconventional viruses of the transmissible subacute spongiform encephalopathies (kuru-CJD-GSS-FFI-scrapie-BSE) are nucleants spontaneously generated from host precursor proteins altered to beta-pleated sheet configuration that polymerize into insoluble infectious amyloid fibrils. The de novo conversion to infectious amyloids is facilitated or accelerated by many different point mutations causing amino acid changes, a stop codon, or octapeptide inserts that increase the likelihood of spontaneous conversion to infectious configuration by many orders of magnitude. Similar nucleating induction of configurational change to amyloid probably occurs in other amyloidoses of brain and in systemic amyloidoses. Thus, all amyloids, particularly so-called fibrillar amyloid enhancing factors, may be considered to be infectious scrapie-like agents. These events probably occur extracellularly, thus we are attempting to reproduce them in vitro, even from synthetic polypeptides.

The transmissible amyloidoses: genetical control of spontaneous generation of infectious amyloid proteins by nucleation of configurational change in host precursors: kuru-CJD-GSS-scrapie-BSE

Kuru, Creutzfeld-Jakob disease, Gerstmann-Sträussler syndrome, scrapie, and bovine spongiform encephalopathy are caused by so-called unconventional viruses which are really replicating proteins which induce by auto nucleation and autopatterning a configurational change in the precursor protein to produce an infectious amyloid form. Crystallography and NMR may eventually determine how amyloid precursor protein is converted to this infectious form by configurational changes in all tertiary and quaternary structure of the normal precursor. Most sporadic cases of CJD arise by de novo spontaneous conversion of the normal precursor to the infectious form, a rare event occurring at the frequency of one per million persons per year (the annual incidence of CJD throughout the world). In the familial forms of CJD and GSS, where the occurrence is an autosomal dominant trait, each family has one of five different mutations causing a single amino acid change or one of five insertions of 5, 6, 7, 8 or 9 octapeptide repeats. Each mutation causes a million-fold increased probability of the spontaneous configurational change to an infectious polypeptide, and appears as an autosomal dominant trait. Thus, the behavior of the transmissible brain amyloidosis parallels completely that of the transthyretin amyloidoses causing familial amyloidotic polyneuropathy, in which there are 19 different point mutations, each one of which increases enormously the likelihood of configurational change of transthyretin prealbumin to amyloid.