Prion protein formation

Caughey WS, Raymond LD, Horiuchi M, Caughey B. Inhibition of protease-resistant prion protein formation by porphyrins and phthalocya-nines. Proc Natl Acad Sci USA 1998 95 12117-12122. 

The conformational plasticity supported by mobile regions within native proteins, partially denatured protein states such as molten globules, and natively unfolded proteins underlies many of the conformational (protein misfolding) diseases (Carrell and Lomas, 1997 Dobson et al., 2001). Many of these diseases involve amyloid fibril formation, as in amyloidosis from mutant human lysozymes, neurodegenerative diseases such as Parkinson s and Alzheimer s due to the hbrillogenic propensities of a -synuclein and tau, and the prion encephalopathies such as scrapie, BSE, and new variant Creutzfeldt-Jacob disease (CJD) where amyloid fibril formation is triggered by exposure to the amyloid form of the prion protein. In addition, aggregation of serine protease inhibitors such as a j-antitrypsin is responsible for diseases such as emphysema and cirrhosis. 

All fungal prion proteins have a so-called prion domain and a functional domain. The prion domain is a region of the polypeptide chain that is necessary and sufficient for prion formation and maintenance (Fig. 1 Wickner et al., 2002). For Ure2p and Sup35p, the functional domain is responsible for the cellular activity of the normal form of the protein. 

All fungal prion proteins readily form filaments in vitro (Dos Reis et al., 2002 Glover et al., 1997 Sondheimer and Lindquist, 2000 Taylor et al., 1999). In near-native buffer conditions, filament formation typically occurs in hours to days. Ure2p filaments assembled in vitro have a diameter of —20 nm and like the filaments observed in situ (Section III.A Fig. 4), they are not hollow. 

Chabry,J., Caughey, B., and Chesebro, B. (1998). Specific inhibition of in vitro formation of protease-resistant prion protein by synthetic peptides. /. Biol. Chem. 273, 13203-13207. 

DeMarco, M. L., and Daggett, V. (2004). From conversion to aggregation Protofibril formation of the prion protein. Proc. Natl. Acad. Sci. USA 101, 2293-2298. Diaz-Avalos, R., Long, C., Fontano, E., Balbirnie, M., Grothe, R., Eisenberg, D., and Caspar, D. L. D. (2003). Cross-beta structure of an amyloid-forming peptide studied by electron nano-crystallography. Fibre Diffract. Rev. 11, 79-86. 

Kocisko, D. A., Come, J. H., Priola, S. A., Chesebro, B., Raymond, G.J., Lansbury, P. T., and Caughey, B. (1994). Cell-free formation of protease-resistant prion protein. Nature 370, 471-474. 

Sokolowski, F., Modler, A. J., Masuch, R., Zirwer, D., Baier, M., Lutsch, G., Moss, D. A., Gast, K., and Naumann, D. (2003). Formation of critical oligomers is a key event during conformational transition of recombinant Syrian hamster prion protein. / Biol. Chem. 278, 40481-40492. 

Warwicker, J. (2000). Modeling a prion protein dimer Predictions for fibril formation. 

Pan, K. M., Baldwin, M., Nguyen, J., Gasset, M., Serban, A., Groth, D., Mehlhorn, I., Huang, Z., Fletterick, R. J., Cohen, F. E., and Prusiner, S. B. (1993). Conversion of alpha-helices into beta-sheets features in the formation of the scrapie prion proteins. Proc. Natl. Acad. Sci. USA 90, 10962-10966. 

Protein only" hypothesis for prion plaque formation,... 

What are the possible adverse consequences of accumulation of the A(3 protein It may cause inflammation by activation of microglia,1157 which may cause damage by release of NO.1206 A(3 may induce death of neurons by apoptosis.1201 1207-1209 A defect in protesomal degradation may be a factor.1208 Both Ap and the prion protein may promote oxidative damage. The brain derives most of its energy from oxidative metabolism, a major source of damaging radicals. Mitochondria are found in dendrites as well as cell bodies.1210 Methionine residues in glycine-rich parts of the AP and prion proteins are suspected as centers of free radical formation.1202 1211... 

Proske, D., Gilch, S., Wopfner, F., Schatzl, H.M., Winnacker, E.L. and Famulok, M. (2002) Prion-protein-specific aptamer reduces PrPSc formation, Chembiochem. 3, 717-725. 

The antimalarial drug quinacrine and some phenothiazine derivatives, acepro-mazine, chlorpromazine, and promazine, have been used for the treatment of prion diseases (Doh-ura et al., 2000 Korth et al., 2001 May et al., 2003). The molecular mechanism associated with the inhibition of PrPsc formation by quinacrine remains unknown. However, it is proposed that quinacrine binds with human prion protein at the Tyr-225, Tyr-226, and Gln-227 residues of helix 3 (Vogtherr et al., 2003) and provides neuroprotection. Quinacrine may also act as an antioxidant and reduce the toxicity of prP 6 (Turnbull et al., 2003). 

Brain tissue of a patient infected with vCJD. Note the formation of (white) vacuole spaces and (dark, irregular) plaques of prion protein. (Magnification 200X)... 

Prion protein aggregates do not show increase in Thioflavin T (ThT) fluorescence, indicating the formation of amorphous aggregates. In order to probe... 

As discussed earlier, conformational change/structural perturbation is a prerequisite for amyloid formation. Exposure to UV light did not initiate the fibril formation it led to amorphous aggregation of prion protein and no observable change to the other two proteins. We have employed conditions that are known to favor amyloid fibril formation and investigated the effect of UV light exposure of these proteins on their ability to form amyloid fibrils. 

Fig. 14.4. Effect of UV exposure on de novo amyloid fibril formation of prion protein, P2-microglobulin and a-synuclein. Amyloid fibril formation of (a) prion protein (b) p2-microglobulin and (c) a-synuclein. fn each panel, (filled square) represents proteins that are not exposed to UV light, and (filled circle) the UV-exposed protein. The fibril formation was monitored by ThT fluorescence. An aliquot of the sample was withdrawn at different time points and added to 0.5 ml of 10 pM ThT in 50 mM glycine-NaOH buffer (pH 8.5), and the fluorescence intensity at 485 nm with excitation wavelength set at 445 nm was measured using a Fluorolog FL3-22 fluorescence spectrophotometer. The UV-exposed proteins failed to form amyloid fibril de novo...

Fig. 14.6. De novo amyloid formation of prion protein at different concentrations. Different concentrations of unexposed prion protein (0.1, 0.25, 0.5, 0.75 and l.OmgmV1) and UV-exposed prion protein (l.Orngrnl ) were subjected to amyloid-forming conditions. The figure shows representative data at each concentration. Exposed represents UV-exposed prion protein...

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