OlympusEurogentecChemical BiologyAffinitioswel.gifIdeal

HomeLibraryBeagleSearchMedJobsMallDiscussionConfJoinSearch
Search
Feedback

There are several options for viewing an article. You can display Figures in the Text as - Quickest: Links Only, Medium: Thumbnails or Slowest: Full Figures (Current).
Curr Opin Struct Biol
The prion folding problem.
Review article

Paul M Harrison, Paul Bamborough, Valerie Daggett, Stanley B Prusiner and Fred E Cohen

Current Opinion in Structural Biology 1997, 7: 53-59.

Outline

Abstract

Prion diseases are neurodegenerative disorders in which dramatic conformational change in the structure of the prion protein is the fundamental event. This structural transition involves the loss of substantial alpha-helical content and the acquisition of ß-sheet structure. A convergence of recent biological and structural studies argues that the mechanism underlying the prion diseases is truly unprecedented.

Introduction

The prion diseases are caused by an aberrantly folded form of the prion protein, PrPSc, covalently indistinguishable but conformationally distinct from the normal form, PrPC. Formation of PrPSc from PrPC involves the conversion of alpha-helical to ß-sheet secondary structure [1] [2] [3]. Our challenge is to link the misfolding of the prion protein to the resulting cellular pathology in a way that explains how the prion diseases can occur in inherited, infectious and sporadic forms. The inherited prion diseases of humans, kuru, Creutzfeldt-Jakob disease (CJD), Gerstmann-Straussler-Scheinker (GSS) syndrome and fatal familial insomnia (FFI), have all been linked to specific point and insertional mutations in the prion protein sequence [4]. The infectious forms of the disease resulting from prion inoculation include iatrogenic CJD and kuru, which is spread through ritualistic cannibalism amongst the Fore tribe of New Guinea in humans, bovine spongiform encephalopathy (BSE), and scrapie in sheep. Sporadic CJD occurs in approximately one in one million humans. These individuals lack germ line mutations in their PrP genes.

Evidence is accumulating that a new prion strain has crossed the species barrier to humans from cattle with BSE. This disease in humans is called variant (v)CJD because of the unusual neuropathology and young age of the patients [5]. The economic and political impacts of these events are only beginning to be felt. Thus, research into the alpha-to-ß conformational transition that occurs during formation of the scrapie PrP isoform has taken on new urgency.

General prion biology has recently been reviewed [3] [4] [6•] [7] [8]. This review will focus on recent experimental and theoretical insights into the possible details of the alpha-to-ß conformational change upon PrPSc formation.

Structural insights into the possible details of the alpha-to-ß conversion

PrP is anchored by glycosylphosphatidyl-inositol (GPI) to the cell membrane [9] and has N-linked sialoglycosylation at two asparagines (residues 181 and 197) [10]. Edman sequencing and mass spectrometry of PrPSc have revealed no differences between its amino acid sequence and that translated from the PrPC nucleotide sequence [11]. Fig. 1 illustrates the PrP sequence, the GPI-anchor, glycosylation sites and the positions of key features for the prion diseases. Mammalian PrP contains five (and occasionally six) copies of a glycine-rich octarepeat (Fig. 1). No chemical modifications have yet been identified by which PrPC and PrPSc differ [11]. Fourier transform infrared (FTIR) and circular dichroism (CD) spectroscopy indicate that PrPC is substantially alpha-helical with little or no ß-sheet structure, whereas PrPSc has high ß-sheet content and less alpha-helical structure [1] [2] [12]. A proteinase-K resistant, insoluble fragment of 27-30 kDa (residues sim90-231), designated PrP 27-30 [13] [14], that has an N terminus approximately at residue 90 of PrP has been identified in PrP amyloid. Using a heuristic approach that combined multiple sequence information, the above experimental data, and a combinatorial algorithm for generating plausible tertiary structures for predictive secondary-structure profiles, PrPC was predicted to form a four alpha-helical bundle (Fig. 2) [15]. Secondary-structure profiles derived by experiment and by theoretical modelling for different PrPC and PrPSc fragments, and the terminology used to describe them in this review, are depicted in Fig. 2.

Figure 1 The key features of the PrP sequence that are of relevance to prion disease. Only the Ala 117rarrVal and Pro101 rarrLeu point mutations discussed in the text are indicated (*). For a discussion of the other point mutations associated with inherited diseases and of polymorphisms in the mammalian PrP genes see [6•] [11]. The GPI-anchor (231 GPI) and the N-linked glycosylation sites (N181, N197) are indicated. The helices determined experimentally by Riek et al. [28•] are depicted as boxes with a heavy outline and their N-terminal and C-terminal residue positions are labelled. The helix labels H3 and H4, which were used in the original PrPC structure predictions, are used in this figure to indicate the corresponding experimentally determined helices, with the H2.5 label representing the additional helix. The H1 and H2 helices from the original prediction are depicted in broken heavy outline with the termini of these helices labelled.

Return to Figure reference in text 1 , 2 , 3 , 4 , 5 , 6 , 7

Figure 2 PrP tertiary structures derived from both NMR and structure prediction, and PrP(90-145) secondary structure derived from NMR. The structure predictions of fragments of the cellular form, PrPC(109-217), and of the infectious form, PrPSc(108-217), of the prion protein are shown bottom left and right, respectively. The NMR-derived tertiary structure of PrP(121-231) and the NMR-derived secondary structure of PrP(90-145) are shown top right and left, respectively. In the NMR-derived structure, the strands are red and the helices are cyan. In the PrPC structure prediction, H1 is red and H2 is green (for the helix-numbering definition, see Fig. 1). In the PrPSc prediction, the corresponding strands are coloured similarly. Residues that are implicated in the prion disease species barriers are indicated on the PrPSc predictive structure, bottom right, and cluster on the outer face of the ß sheet.

Return to Figure reference in text 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10

PrP(109-122), the putative H1 region (see Fig. 1), is the most highly conserved region in the prion protein sequences across all species (from mammalian to avian) [6] [16]. Mutations in this region, such as Ala117rarrVal in GSS, cause inherited prion disease. In molecular dynamics simulations of PrP(109-122), modelled initially as an alpha helix, this GSS mutation was the only helix-destabilizing mutation amongst an array of hydrophobic replacements at the same position [17]. Under differing solvent conditions, FTIR spectroscopy showed that PrP(109-122) and the other three predicted alpha-helical regions, PrP(129-140), PrP(178-191) and PrP(202-217), plus the segments PrP(113-127) and PrP(113-120) (see Fig. 1), when isolated as peptides, displayed either alpha-helical or ß-sheet character [18]. The helix-promoting organic solvent hexafluoroisopropanol (HFIP) induced alpha-helical conformation in all four peptides; in aqueous solution, all except PrP(129-140) took on ß-sheet character and slowly precipitated from solution as amyloid fibrils. PrP(113-120), the AGAAAAGA (using amino acid single-letter code) palindrome, was the most amyloidogenic peptide.

A variety of data argue for the presence of a specific molecular interaction between PrPC and PrPSc during prion replication, for example, the existence of the species barrier, which has historically prevented the spread of sheep scrapie to humans [4], and the recent attempts to convert PrPC to PrPSc in vitro [19]. The molecular basis of the species barrier is also evident from studies in which transgenic mice that expressed both Syrian hamster (SHa) and host mouse PrP genes, and that were inoculated with either mouse or SHa prions, preferentially produced prions like those of the inoculum [20]. Recent data point to the PrP(109-122) region as being important in this PrPC-to-PrPSc conversion process. PrP(109-122), as an isolated peptide, can induce conformational changes in two other PrP fragments. Nguyen et al. [21] have shown that the fragments PrP(104-122) and PrP(129-141), the putative H2 region (see Fig. 1), of SHaPrPC, which have coil or alpha-helical structure in solution, were induced to form insoluble aggregates rich in ß-sheet structure by the addition of small amounts of PrP(109-122). Furthermore, this conversion was sequence-specific: mouse PrP(109-122), which differs from the corresponding region of the SHa protein at residues 109 and 122, did not convert SHaPrP(104-122) as efficiently. These results are suggestive of a heterodimerization interaction between PrPC and PrPSc and are consistent with PrP(109-122) acting as a trigger in the conformational transition.

In studies of several PrPC peptide fragments, PrP(109-122) appears to be the most highly structured region–thinsp as either alpha helix or ß sheet irrespective of its environment (solid state or in solution) or the nature of solvent conditions [22]. NMR-spectroscopic studies have shown that PrP(109-122) intrinsically prefers extended ß-sheet conformation to alpha-helical conformation in the solid state [23]. PrP(109-122) samples lyophilized from 50% acetonitrile/50% water showed ß-sheet conformation. An alpha-helical conformation was observed for residues 113-117 for such samples lyophilized from the helix-promotor HFIP. In addition, rotational-resonance experiments on samples lyophilized from water indicated an extended conformation (probably ß sheet) for PrP(109-122).

Investigations have concentrated on PrP(90-145) as a prime candidate for alpha-to-ß conversion, as residue 90 approximates the N terminus of Prp27-30 and 145 is the position of a stop-codon mutation causing prion disease [24]. Evidence for the conformational plasticity of this region continues to accumulate. NMR-spectroscopic studies of PrP(90-145) and PrP(109-141) indicate that regions of alpha-helical structure (109-122 and 129-141) corresponding to the predicted H1 and H2 regions can occur [25] (Fig. 2, Fig. 3). These experiments were performed in sodium dedecyl sulphate (SDS), in an attempt to simulate the membrane interface to which PrPC is normally anchored. PrP(90-145) was also shown by FTIR to form intermolecular ß sheets at physiological salt concentrations after a period of several weeks. X-ray diffraction studies have also been performed on ultrastructural prion rods formed from the PrP(90-145) fragment from SHa scrapie-infected brain, and from synthetic peptides for PrP(113-120) and PrP(109-122) [26]. Rods of SHaPrP(90-145) contained ß-sheet structure with inter-ß-sheet and hydrogen-bonding distances that were compatible with those observed for hydrated PrP27-30 prion rods. This indicates that PrP(90-145) can model the ß-sheet-forming tendency of PrPSc, and this is consistent with the FTIR-spectroscopic studies on the same fragment described above [25].

Figure 3 Schematic comparison of the secondary-structure profiles of various fragments of PrPC and PrPSc derived from experiment and from theoretical modelling. The references for each profile (numbered 1-5) are as follows 1 [15], 2 [25], 3 [28•], 4 [36], 5 [23]. Corresponding secondary structures in each profile are coloured the same (scarlet, green, cyan, yellow and red). The positions of the half cysteines forming the disulphide and the residue positions of the termini of each secondary structure are indicated in each profile. The alpha helices are labelled according to their correspondence with the original predicted helices for PrPC [15]. That is, in the NMR-derived structure of the PrP(121-231) fragment [28•], the first helix in the sequence is labelled H2.5, the second, H3, and the third, H4. ß Strands in the structural prediction for the PrPSc infectious fragment [36] and the PrP(121-231) NMR structure [28•] are shown in the colours of the corresponding helices in the PrPC prediction (see Fig. 2).

Return to Figure reference in text 1

Additional peptide studies can be used to localize the residues at the PrPC/PrPC interface that may provide the molecular basis of the prion-disease species barrier. When SHaPrP(90-145), in a non-ß conformation, is incubated in 5000-fold excess with SHaPrPC, a proteinase-resistant complex is formed [27]. This PrPC-SHaPrP(90-145) complex has increased ß-sheet content as judged by FTIR. Consistent with the known species barriers, mouse PrP(90-145) peptide could not promote this conversion in SHaPrPC. A SHaPrP(90-145) peptide with the Ala117rarrVal inherited mutation of GSS was the most efficient in achieving the conversion.

The NMR-derived tertiary structure of PrP(121-231) fragment and predicted PrP tertiary structures

The tertiary structure of a PrP C-terminal fragment, denoted PrP(121-231), has been resolved using two-dimensional NMR (Fig. 2) [28•]. This fragment corresponds to a normal PrP endosomal-degradation product [29] [30] but does not contain PrP(109-121), which in other investigations appears to be a key region for the alpha-to-ß conversion during PrPSc formation. What was unexpected, in view of the spectroscopic data on PrPC, was the existence of an antiparallel ß sheet that has two strands of four residues each (128-131 and 161-164) in PrP(121-231). In the absence of PrP(109-122), the putative H1 region, this structure may have characteristics of a conformation that is intermediate between PrPC and PrPSc, such as the PrP* conformation of the catalytic or template-assistance model for prion propagation ([31]; see below). PrP* is a partially unfolded intermediate arising from stochastic fluctuations in the PrPC conformation [31]. Distinct conformations that have characteristics intermediate between those of PrPC and PrPSc have been detected. These are insoluble yet proteinase-K sensitive [32] [33].

The most striking aspect of the PrP(121-231) structure is that there are distinct positively and negatively charged surfaces that are indicative of the orientation of the protein relative to the cell membrane. The predominantly negatively charged surface contains the two sialoglycosylation sites, the first helix in PrP(121-231) and four of the five residues (138, 143, 145, 155) that have been shown experimentally to be important in the species barrier between man and mouse [34•]. (PrP [121-231] is not sialoglycosylated, which would entail a substantial part of the protein surface for this negatively charged side, because the fragment is expressed in Escherichia coli.) Also of note is that positions 143 and 155 are serine and histidine, respectively, in both human and bovine PrPC, a similarity that may have implications for the vCJD occurring in the United Kingdom which is thought to be caused by BSE prions. The fifth position (166) associated with the human/mouse species barrier [34•] is remote from the other four and located on an opposing face of the structure, perhaps implying that PrPC-PrPSc interaction is not mediated at a specific local surface of PrPC. As anticipated from the computational studies [15] [35], six human inherited-disease point-mutation sites cluster in or around the two C-terminal helices, and three of them participate in the hydrophobic core (Fig. 1). The PrP(121-231) structure is thus consistent with a model of PrPSc formation in which the inherited-disease mutations disrupt the integrity of the PrPC structure and its hydrophobic core [15] [35]. The positions of species-barrier residues and the existence of such distinct charged surfaces put constraints on the possible surface complementarity of any putative PrPC-PrPSc dimer complex.

The PrPC structure prediction [15] compares favourably with this PrP(121-231) structure at the secondary-structure level (Fig. 2). The prediction of the two C-terminal alpha helices (Fig. 2) was correct to within ±2 residues at either end. The additional alpha helix (144-154) corresponds to a weakly predicted alpha-helical segment in the original secondary-structure prediction that was difficult to adjoin to the hydrophobic core. This helix appears to be peripheral to the structural core of PrP(121-231).

The structure of a fragment of PrPSc (residues 108-217) was predicted by a similar heuristic approach to that used in the PrPC prediction (Fig. 2) [36]. Plausible models were generated in which each possible pair of predicted helices was converted into four ß strands that have their ends at probable ß-strand-breaking residues (Fig. 2). A PrPSc model was chosen out of the short-list of plausible structures that maintained the clustering of residues implicated in the species barrier on the outer face of the ß sheet. In this case, the first two predicted helices were identified for conversion to ß sheet. This result is consistent with the maintenance of the disulphide in PrPSc [37], with the body of data on the conformational plasticity of PrP(90-145) described above, and with the disease-associated stop-codon mutation at position 145 referred to above [24]. In initial secondary-structure predictions that did not assume the fold class (i.e. alpha/alpha, ß/ß or alpha/ß) of the PrP chain, the PrP(179-217) region was more consistently predicted to be alpha-helical than the PrP(109-141) region [1]. This is the region of greater agreement between the PrPC prediction and the NMR-derived PrP(121-231). This further supports the choice of the PrP(109-141) region for conversion to ß sheet in the PrPSc infectious-fragment prediction (Fig. 2). Also notable is that the N terminus of one of the PrP(121-231) ß strands (128-131) coincides with the N terminus of a ß strand (128-135) in the PrPSc prediction.

Prion-propagation models-thinspdoes PrPSc formation require PrPSc polymers?

A conformational model for prion disease requires that one amino acid sequence can code for two (or more) conformations dependent on its complexation state and/or environment. In this regard, a key issue for PrPC-to-PrPSc conversion is whether the presence of PrPSc polymers/multimers is required or whether the formation of PrPSc aggregate is purely a consequence of PrPSc overproduction. In any model, there must also be adequate explanation of the three different forms of prion disease (infectious, inherited and sporadic). Two PrPSc-propagation models have been proposed that differ by whether the presence of PrP amyloid is needed for PrPSc formation: the catalytic or template-assistance model [31] [35] and the nucleated-polymerization model [38].

In the template-assistance model, a PrPSc monomer or dimer binds to one or two chains of PrPC or PrP*, a partially unfolded intermediate arising from stochastic fluctuations in PrPC conformation. This binding lowers the activation-energy barrier to the formation of new PrPSc from PrPC/PrP*, which itself then recruits further PrPC/PrP* for conversion. Infectious prion disease arises from exogenous PrPSc providing a template to initiate this process and inherited mutations destabilize PrPC and lower the activation-energy barrier to conversion in the presence of a template. Inherited 'point' mutations are postulated to disrupt the integrity of the hydrophobic core of PrPC, as noted above [15] [35]. Inherited 'insertional' mutations, which have either two or from four to nine extra octarepeats (e.g. [39] [40]), may relatively destabilize PrPC in conversion to PrPSc by an as yet unidentified mechanism. 'Sporadic' disease arises in the rare instances in which the stochastic fluctuations are sufficient to cross this activation barrier. (Somatic mutations that have the same effect as the inherited point mutations but that are rarer are also a possible explanation of sporadic disease.)

In the nucleated-polymerization model, the initial slow reversible formation of a nucleating PrPSc multimer leads to a seeding process –thinsp analogous to crystallization –thinspwherein PrP monomers are added to the growing polymer in a way that stabilizes an abnormal conformation (that we may term PrP*) [38]. The growing polymers break apart generating new seeds to fuel exponential growth in the total polymer. Nucleated polymerization is precedented in deoxyhaemoglobin-S fibril formation [6•] [38]. Normally the reversible-nucleation process is slow (in sporadic disease); however, infectious PrPSc acts as a ready-made nucleation seed and inherited mutations might increase the affinity of the abnormal conformation (PrP* and then PrPSc) for the polymer seed.

Using simulation, Bamborough et al. [6•] have shown that given most experimental data these two models are not easily differentiable kinetically. Consistent with the template-assistance model, ionizing-radiation data suggest that a dimer of PrPSc is the minimal infectious entity [41], that PrP aggregates are negligibly detectable in some prion diseases [42], and that infectivity increases moderately upon dispersion of prion rods in liposomes [43]. Wille et al. [44] used electron microscopy and differential binding of Congo-red dye to show that the specific PrPSc ß-sheet-rich structures responsible for prion infectivity can be distinguished from PrP amyloid, in opposition to the nucleated-polymerization model and consistent with the template-assistance model. The nucleated-polymerization model has been most successful in modelling peptide-conformation conversion data and has helped to direct in vitro attempts to convert PrPC to PrPSc [19] [45] [46]. To date, complexes of labelled PrPC and unlabelled PrPSc have been created in which the labelled PrP apparently acquires the proteinase-resistant phenotype of PrPSc. As the labelled PrPC cannot be released from the complex, it is unknown whether the proteinase resistance exhibited by labelled PrPC results from its binding to PrPSc, which provides protection from proteolytic digestion, or whether the structure of PrPC has been transformed into that of PrPSc. Distinguishing between these two alternatives is important in assessing the utility of this in vitro system, and in drawing conclusions from it concerning the mechanism of PrPSc formation.

The most obvious difference between the template-assistance model and the nucleated-polymerization model is the expected rate enhancement with increasing concentration of the monomer PrP. The rate of nucleated-polymerization depends upon the monomer concentration raised to the power of the number of monomers in the nucleus, whereas the rate-limiting step in the template-assistance model is presumed to be the conformational conversion of the monomer unit, a first order process. Transgenic-animal experiments can be developed that explore this issue. Mice with their endogenous PrP genes knocked out can be given an inherited prion disease through the addition of a transgene carrying the GSS mutation Pro101rarrLeu [47]. These mice develop spontaneous disease in sim 145 days. By mating the mice, a second generation is born that has twice the transgene copy number of the founder. If one assumes that gene copy number and PrPC monomer concentration are proportional, the template-assistance model predicts that a doubling of the concentration of monomers should halve the rate of disease development, whereas the nucleated-polymerization model anticipates a more dramatic shortening of the time to develop disease. Recent results demonstrate that mice homozygous for the mutant transgene array develop disease in sim85 days [47].

Prion strains have been identified that have different disease incubation times and neuropathology, despite, for example, being propagated in a single inbred PrP-homozygous mouse strain. Prion strains might be explained within the framework of the template-assistance model as resulting from induced fit to a particular PrPSc conformational variant and/or from a particular packing of the PrPSc in the dimer [48]. A PrPSc dimer rather than a monomer may be the best candidate for the infectious unit that propagates PrPSc conformation for this model [35], because it is easier to envisage an induced conformation as maintained in such a dimer.

Evidence of a host-specific prion-binding protein (protein X) of relevance to prion propagation has recently been obtained. Mice cannot be consistently infected by human prions and inoculation of mice carrying a human (Hu)PrP transgene with human prions produces disease in only < 10% of animals [34]. Mice lacking their endogenous mouse (Mo)PrP genes but expressing a HuPrP transgene, however, develop disease upon inoculation with human prions. This argues that the normal MoPrP-gene product interferes with the interaction of HuPrPC with HuPrPCJD or a host factor required for conversion to PrPSc/PrPCJD. As there is little evidence for a potent MoPrPC: HuPrPSc interaction, the hypothesis of a prion-binding protein X has been proposed. In an effort to localize the possible protein X binding site on PrPC, transgenic mice expressing a mouse/human/mouse chimeric PrP gene were inoculated with HuPrPCJD [34]. The chimaera based on the MoPrP sequence contained human residues at positions 90-167, a region suggested by peptide structural studies to contain critical components for the species barrier and conformational change upon conversion to PrPSc. As this chimaera supports infection with HuPrPCJD and residues 23-90 are not required for infectivity [49] [50], it is probable that protein X interacts with PrPC at the C terminus (167-231). As conversion of PrPC to PrPSc must involve substantial refolding, protein X may be a molecular chaperone fulfilling a role analogous to that of Hsp104 in the [PSI+)] non-mendelian inheritance phenomenon in yeast [51•].

Conclusions

Considerable evidence has accumulated in support of the importance of PrP(90-145) in the alpha-to-ß conversion during PrPC formation, and of PrP(109-122) in particular. Peptide studies have suggested that this region is key in mediating the interaction of PrPC and PrPSc during conversion of PrPC to PrPSc and have produced effects that are reminiscent of the prion-disease species barriers. The PrP(121-231) NMR-derived tertiary structure gives us some further clues about the possible structural details of the conversion process. The challenge remains to combine a framework for prion propagation with such structural details in a conformational prion-disease model that encompasses the existence of prion strains and host-dependent factors, and that thus provides an explanation of the prion folding problem.

References and recommended reading

Papers of particular interest, published within the annual period of review, have been highlighted as:

bball of special interest

bballbball of outstanding interest

  1. Pan K-M, Baldwin M, Nguyen J, Gasset M, Serban A, Groth D, Mehlhorn I, Huang Z, Fletterick RJ, Cohen FE, Prusiner SB: Conversion of alpha-helices into ß-sheets features in the formation of the scrapie prion protein. Proc Natl Acad Sci USA 1993, 90 : 10962-10966.
    2. [MEDLINE], Return to reference citation 1 , 2 , 3

  2. Baldwin MA, Pan K-M, Nguyen J, Huang Z, Groth D, Serban A, Gasset M, Mehlhorn I, Fletterick RJ, Cohen FE, Prusiner SB: Spectroscopic characterisation of conformational differences between PrPC and PrPSc: and alpha-helix to beta-sheet transition. Phil Trans R Soc Lond B 1994, 343 : 435-441.
    3. [MEDLINE], Return to reference citation 1 , 2

  3. Baldwin MA, Cohen FE, Prusiner SB: Prion protein isoforms a convergence of biological and structural investigations. J Biol Chem 1995, 270 : 19197-19200.
    4. [MEDLINE], Return to reference citation 1 , 2

  4. Prusiner SB: Molecular biology and genetics of prion disease. Phil Trans R Soc Lond B 1994, 343 : 447-463.
    5. [MEDLINE], Return to reference citation 1 , 2 , 3

  5. Will RG, Ironside JW, Zeidler M, Cousens SN: A new variant of Creutzfeldt-Jakob disease in the U.K. Lancet 1996, 347 : 921-925.
    6. Return to reference citation 1

  6. bball Bamborough P, Wille H, Telling GC, Yehiely F, Prusiner SB, Cohen FE: Prion protein structure and scrapie replication: theoretical, spectroscopic and genetic investigations. Cold Spring Harb Symp Quant Biol 1996, 61 : in press.
    A comprehensive review of many aspects of prion biology that also contains kinetic analysis of the two prion-propagation models (template-assistance and nucleated-polymerization). In addition, a striking sequence similarity between the putative H1 region and a repeat in a fibrous spider-silk protein is discussed.
    7. Return to reference citation 1 , 2 , 3 , 4 , 5

  7. Weissmann C: Molecular biology of transmissible spongiform encephalopathies. FEBS Lett 1996, 389 : 3-11.
    8. Return to reference citation 1

  8. Edited by Prusiner SB. Prion diseases. Seminars in Virology, vol 7. Philadelphia: Saunders Scientific Publications. 1996,
    9. Return to reference citation 1

  9. Stahl N, Borchelt D, Hsaio K, Prusiner SB: Scrapie prion protein contains a phosphatidylinositol glycolipid. Cell 1987, 51 : 229-240.
    10. [MEDLINE], Return to reference citation 1

  10. Endo T, Groth D, Prusiner SB, Kobata A: Diversity of oligosaccharide structures linked to asparagines of the scrapie prion protein. Biochemistry 1989, 28 : 8380-8388.
    11. [MEDLINE], Return to reference citation 1

  11. Stahl N, Baldwin MA, Teplow DB, Hood L, Gibson BW, Burlingame AL, Prusiner SB: Structural studies of the scrapie prion protein using mass spectrometry and amino acid sequencing. Biochemistry 1993, 32 : 1991-2002.
    12. [MEDLINE], Return to reference citation 1 , 2 , 3

  12. Safar J, Roller PP, Gadjusek DC, Gibbs CJ: Thermal stability and conformational transitions of scrapie amyloid (prion) protein correlate with infectivity. Protein Sci 1993, 2 : 2206-2216.
    13. [MEDLINE], Return to reference citation 1

  13. Prusiner SB, Bolton DC, Groth DF, Bowman KA, Cochran SP, McKinley MP: Further purification and characterization of scrapie prions. Biochemistry 1982, 21 : 6942-6950.
    14. [MEDLINE], Return to reference citation 1

  14. Oesch B, Westaway D, Walchli M, McKinley MP, Kent SBH, Aebersold R, Barry RA, Tempst P, Teplow DB, Hood LE, et al.: A cellular gene encodes scrapie PrP27-30 protein. Cell 1985, 40 : 735-746.
    15. [MEDLINE], Return to reference citation 1

  15. Huang Z, Gabriel J-M, Baldwin MA, Fletterick RJ, Prusiner SB, Cohen FE: Proposed three-dimensional structure for the cellular prion protein. Proc Natl Acad Sci USA 1994, 91 : 7139-7143.
    16. [MEDLINE], Return to reference citation 1 , 2 , 3 , 4 , 5 , 6 , 7

  16. Schatzl HM, Da Costa M, Taylor L, Cohen FE, Prusiner SB: Prion protein gene variation among primates. J Mol Biol 1995, 245 : 362-374.
    17. [MEDLINE], Return to reference citation 1

  17. Kazmirski SL, Alonso DOV, Cohen FE, Prusiner SB, Daggett V: Theoretical studies of sequence effects on the conformational properties of a fragment of the prion protein: implications for scrapie formation. Chem Biol 1995, 2 : 305-315.
    18. Return to reference citation 1

  18. Gasset M, Baldwin MA, Lloyd DH, Gabriel J-M, Holtzman DM, Cohen FE, Fletterick R, Prusiner SB: Predicted alpha-helical regions of the prion protein when synthesized as peptides form amyloid. Proc Natl Acad Sci USA 1992, 89 : 10940-10944.
    19. [MEDLINE], Return to reference citation 1

  19. Kocisko DA, Come JH, Priola SA, Chesebro B, Raymond GJ, Lansbury PT, Caughey B: Cell-free formation of proteaseresistant prion protein. Nature 1994, 370 : 471-474.
    20. [MEDLINE], Return to reference citation 1 , 2

  20. Prusiner SB, Scott M, Foster D, Pan K-M, Groth D, Mirenda C, Torchia M, Yang S-L, Serban D, Carlson GA, et al.: Transgenetic studies implicate interactions between homologous PrP isoforms in scrapie prion replication Cell 1990, 63 : 673-686.
    21. [MEDLINE], Return to reference citation 1

  21. Nguyen J, Baldwin MA, Cohen FE, Prusiner SB: Prion protein peptides induce alpha-helix to ß-sheet conformational transitions. Biochemistry 1995, 34 : 4186-4192.
    22. [MEDLINE], Return to reference citation 1

  22. Baldwin MA, Zhang H, Bekker T, Zhou S, Nguyen J, Kolbert AC, Heller J, James TL, Wemmer DE, Pines A, et al.: Synthetic peptides model alpha-helix/beta-sheet conformational change in the prion protein. In Peptides: Chemistry and Biology. Edited by Kaumaya TP, Hodges R. ESCOM: Leiden. 1996, 468-470.
    23. Return to reference citation 1

  23. Heller J, Kolbert A, Larsen R, Ernst M, Bekker T, Baldwin MA, Prusiner SB, Prines A, Wemmer DE: Solid-state studies of the prion protein H1 fragment. Protein Sci 1996, 5 : 1655-1661.
    24. Return to reference citation 1 , 2

  24. Kitamoto T, Iuzuka R, Tateishi I: An amber mutation of prion protein in Gerstmann-Sträussler syndrome with mutant PrP plaques. Biochem Biophys Res Commun 1993, 191 : 709-714.
    25. Return to reference citation 1 , 2

  25. Zhang H, Kaneko K, Nguyen JT, Livshits TL, Baldwin MA, Cohen FE, James TL, Prusiner SB: Conformational transitions in peptides containing two putative alpha-helices of the prion protein. J Mol Biol 1995, 250 : 514-526.
    26. [MEDLINE], Return to reference citation 1 , 2 , 3

  26. Nguyen JT, Inouye H, Baldwin MA, Fletterick RJ, Cohen FE, Prusiner SB, Kirschner DA: X-ray diffraction of scrapie prion rods and PrP peptides. J Mol Biol 1995, 252 : 412-422.
    27. Return to reference citation 1

  27. Kaneko K, Peretz D, Pan K-M, Blochberger TC, Wille H, Gabizon R, Griffith OH, Cohen FE, Baldwin MA, Prusiner SB: Prion protein (PrP) synthetic peptides induce cellular PrP to acquire properties of the scrapie isoform. Proc Natl Acad Sci USA 1995, 92 : 11160-11164.
    28. [MEDLINE], Return to reference citation 1

  28. bball Riek R, Hornemann S, Wider G, Billeter M, Glockshuber R, Wuthrich K: NMR structure of the mouse prion protein domain PrP(121-231). Nature 1996, 382 : 180-182.
    The NMR structure of a substantial PrP fragment that does not contain the putative H1 region is reported. Proteolytic degradation in the E. coli periplasm limited the possibility of studying N-terminal extensions of this fragment. This fragment folded reversibly and was stable.
    29. [MEDLINE], Return to reference citation 1 , 2 , 3 , 4 , 5

  29. Haraguchi T, Fisher S, Olofsson S, Endo T, Prusiner SB: Asparagine-linked glycosylation and cellular prion proteins. Arch Biochem Biophys 1989, 274 : 1-13.
    30. [MEDLINE], Return to reference citation 1

  30. Pan K-M, Stahl N, Prusiner SB: Purification and properties of the cellular prion protein from Syrian hamster brain. Protein Sci 1992, 1 : 1343-1352.
    31. [MEDLINE], Return to reference citation 1

  31. Cohen FE, Pan K-M, Huang Z, Baldwin MA, Fletterick RJ, Prusiner SB: Structural clues to prion replication. Science 1994, 264 : 530-531.
    32. [MEDLINE], Return to reference citation 1 , 2 , 3

  32. Priola SA, Caughey B, Wehrly K, Chesebro B: A 60-kDa prion protein (PrP) with properties of both the normal and scrapie-associated forms of PrP*. J Biol Chem 1995, 270 : 3299-3305.
    33. [MEDLINE], Return to reference citation 1

  33. Gabizon R, Telling GC, Meiner Z, Halimi M, Kahana I, Prusiner SB: Insoluble wild-type and protease-resistant mutant prion protein in brains of diseased patients with inherited prion disease. Nat Med 1996, 2 : 59-64.
    34. [MEDLINE], Return to reference citation 1

  34. bball Telling GC, Scott M, Mastrianni J, Gabizon R, Torchia M, Cohen FE, DeArmond SJ, Prusiner SB: Prion propagation in mice expressing human and chimaeric PrP transgenes implicates the interaction of cellular PrP with another protein. Cell 1995, 83 : 79-90.
    This article provides strong evidence for a host-specific phenomenon in prion propagation and a convincing line of reasoning that this phenomenon is a prion-binding protein required for conversion to the scrapie isoform. As the conversion of PrP must involve substantial refolding, the hypothesis that this protein is a molecular chaperone (which may be required in the normal processing of cellular PrP) is favoured.
    35. Return to reference citation 1 , 2 , 3 , 4

  35. Huang Z, Prusiner SB, Cohen FE: Structures of prion proteins and conformational models for prion diseases. In Prions Prions Prions. Edited by Prusiner SB. Springer-Verlag: New York. 1995, 49-67.
    36. Return to reference citation 1 , 2 , 3 , 4 , 5

  36. Huang Z, Prusiner SB, Cohen FE: Scrapie prions: a three-dimensional model of an infectious fragment. Fold Des 1995, 1 : 13-19.
    37. Return to reference citation 1 , 2 , 3

  37. Turk EY, Teplow DB, Hood LE, Prusiner SB: Purification and properties of the cellular and scrapie hamster prion forms. Eur J Biochem 1988, 176 : 21-30.
    38. [MEDLINE], Return to reference citation 1

  38. Lansbury PT, Caughey B: The chemistry of scrapie infection: implications of the ice 9 metaphor. Chem Biol 1995, 2 : 1-5.
    39. Return to reference citation 1 , 2 , 3

  39. Nicholl D, Windl O, De Silva R, Sawcer S, Dempster M, Ironside JW, Estibeiro JP, Yuill GM, Lathe R, Will RG: Inherited Creutzfeldt-Jakob disease in a British family associated with a novel 144-base pair insertion of the prion protein gene. J Neurol Neurosurg Psychiatry 1995, 58 : 65-69.
    40. [MEDLINE], Return to reference citation 1

  40. Campbell TA, Palmer MS, Will RG, Gibb WRG, Luthert PJ, Collinge J: A prion disease with a novel 96-base pair insertional mutation in the prion protein gene. Neurology 1996, 46 : 761-766.
    41. [MEDLINE], Return to reference citation 1

  41. Bellinger-Kawahara CG, Kempner E, Groth D, Gabizon R, Prusiner SB: Scrapie prion liposomes and rods exhibit target sizes of 55 000 Da. Virology 1988, 164 : 537-541.
    42. [MEDLINE], Return to reference citation 1

  42. Hsiao KK, Prusiner SB: Human prion diseases. Ann Neurol 1994, 35 : 385-395.
    43. [MEDLINE], Return to reference citation 1

  43. Gabizon R, McKinley MP, Prusiner SB: Purified prion proteins and scrapie infectivity copartition into liposomes. Proc Natl Acad Sci USA 1987, 84 : 4017-4021.
    44. [MEDLINE], Return to reference citation 1

  44. Wille H, Zhang GF, Baldwin MA, Cohen FE, Prusiner SB: Separation of scrapie prion infectivity from PrP amyloid polymers. J Mol Biol 1996, 259 : 608-621.
    45. [MEDLINE], Return to reference citation 1

  45. Bessen RA, Kocisko DA, Raymond GJ, Nandan S, Lansbury PT, Caughey B: Non-genetic propagation of strain-specific properties of scrapie prion protein. Nature 1995, 375 : 698-700.
    46. [MEDLINE], Return to reference citation 1

  46. Kocisko DA, Priola SA, Raymond GJ, Chesebro B, Lansbury PT, Caughey B: Species specificity in the cell-free conversion of prion protein to protease-resistant forms: a model for the scrapie species barrier. Proc Natl Acad Sci USA 1995, 92 : 3923-3927.
    47. [MEDLINE], Return to reference citation 1

  47. Telling GC, Haga T, Torchia M, Tremblay P, DeArmond SJ, Prusiner SB: Interactions between wild-type and mutant prion proteins modulate neurodegeneration in transgenic mice. Genes Dev 1996, 52 : 1736-1750.
    48. [MEDLINE], Return to reference citation 1 , 2

  48. Telling GC, Parchi P, DeArmond SJ, Cortelli P, Montagna P, Gabizon R, Lugaresi E, Gambetti P, Prusiner SB: Evidence for the conformation of the pathologic isoform of the prion protein enciphering and propagating prion diversity. Science 1996, 274 : 2079-2082.
    49. Return to reference citation 1

  49. Rogers M, Yehiely F, Scott M, Prusiner SB: Conversion of truncated and elongated prion proteins into the scrapie isoform in cultured cells. Proc Natl Acad Sci USA 1993, 90 : 3182-3186.
    50. [MEDLINE], Return to reference citation 1

  50. Fischer M, Rulicke T, Raeber A, Sailer A, Moser M, Oesch B, Brandner S, Aguzzi A, Weissmann C: Prion protein (PrP) with amino-proximal deletions restoring susceptibility of PrP knockout mice to scrapie. EMBO J 1996, 15 : 1255-1264.
    51. [MEDLINE], Return to reference citation 1

  51. bball Patino M, Liu J-J, Glover J, Lindquist S: Support for the prion hypothesis for inheritance of a phenotypic trait in yeast. Science 1996, 273 : 662-670.
    This article presents evidence that the [PSI+] non-mendelian inheritance phenomenon in yeast is a conformational prion condition reliant on conformational change in the endogenous yeast protein Sup35. For effective PSI propagation, intermediate concentrations of the yeast molecular chaperone Hsp 104 are required.
    52. [MEDLINE], Return to reference citation 1

Table of ContentsNextPrevious

Abbreviations

BSE–bovine spongiform encephalopathy;
CD–circular dichroism;
CJD–Creutzfeld-Jakob disease;
FFI–fatal familial insomnia;
FTIR–Fourier transform infrared;
GPI–glycosylphosphatidyl-inositol;
GSS–Gerstmann-Straussler-Scheinker;
HFIP–hexafluoroisopropanol;
Hu–human;
Mo–mouse;
PrP–prion protein;
PrPC–cellular PrP isoform;
PrPSc–scrapie PrP isoform;
PrP 27-30–protease-resistant fragment of PrPSc;
SHa–Syrian hamster;
v–variant.
Return to Title

Author Contacts

PM Harrison, P Bamborough, SB Prusiner and FE Cohen (corresponding author), University of California, Box Number 450, San Francisco, CA-94143, USA. V Daggett, Department of Medicinal Chemistry, University of Washington, Seattle, WA-98195, USA.
Return to author list

Publication Details

Publisher: Current Biology Ltd
London
Address: 34-42 Cleveland Street
London
W1P 6LB
UK
Phone: +44 171 580 8377
Fax: +44 171 580 8428
Email: cbl@cursci.co.uk

Article Information

ISSN: 0959-440X Electronic Identifier: 0959-440X-007-00053
Volume Id.: 7 Issue: 1 Cover Date: February 1997
Number of figures : 3 Number of references : 51 Number of pages : 7
Table of ContentsPrevious

Copyright

Copyright © 1997 Current Biology Ltd.


About BioMedNet / biomednet@cursci.co.uk