Development of a high-pressure treatment for amyloidosis

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1. A disulfide-deficient variant of hen lysozyme self-associates into a 17-S assemblage that contains intermolecular beta-structure. Upon prolonged incubation over weeks to months, amyloid-like fibrils are spontaneously formed. No specific, partially unfolded conformer is involved, and fibrils are formed starting from an intrinsically unfolded monomeric state and passing through a precursor with a spontaneous build-up of intermolecular beta-structure.2. The 17-S precursor reversibly dissociates under hydrostatic pressure of several hundred to two thousand bars. It is characterized with a Gibbs energy for association of -23.3 kJ and a volume increase of 52.7 ml per mol of monomer unit, and involves interaction of hydrophobic residues in the initial association step.3. By carrying out two-dimensional NMR measurements under variable pressure, a metastable conformer of the normal cellular isoform of prion protein (PrP^c) has been found to occur at a population of 1 %, in which helices B an … More d C are disordered. This metastable conformer is most logically PrP^* that is implicated in the step for transformation of PrP^c to the infectious prion protein (PrP^<Sc>) via interaction with a template PrP^<Sc>. On the other hand, the conformational characteristics of a fibril-forming fragment of the mouse prion protein have been investigated by using hydrogen-deuterium exchange measurements and molecular dynamics simulations. Fibril formation was shown to involve polyalanine stacking.4. There exists a correlation for prion protein between the residue-wise stability determined by high-pressure NMR spectroscopy and slow fluctuations determined by the CPMG method at ambient pressure. This indicates that the metastable conformer revealed by high-pressure NMR can be acquired through slow conformational fluctuations under physiological conditions. Cavities exist at the site of large fluctuation, which strongly suggests that the screening for the molecules that bind to the cavity leads to the development of drugs for the treatment of prion disease or amyloidosis. Less