Predisposition of prion protein homozygotes to Creutzfeldt-Jakob disease can be explained by a nucleation-dependent polymerization mechanism

164

194

Protein deposition as amyloid fibrils underlies many debilitating human disorders. The complexity and size of disease-related polypeptides, however, often hinders a detailed rational approach to study effects that contribute to the process of amyloid formation. We report here a simplified peptide sequence successfully designed de novo to fold into a coiled-coil conformation under ambient conditions but to transform into amyloid fibrils at elevated temperatures. We have determined the crystal structure of the coiled-coil form and propose a detailed molecular model for the peptide in its fibrillar state. The relative stabilities of the two structural forms and the kinetics of their interconversion were found to be highly sensitive to small sequence changes. The results reveal the importance of specific packing interactions on the kinetics of amyloid formation and show the potential of this exceptionally favorable system for probing details of the molecular origins of amyloid disease.

Section: Resultsmentioning

confidence: 82%

Exploring amyloid formation by a de novo design

Kammerer

Kostrewa²,

Zurdo³

et al. 2004

164

194

“…Genetic studies have indicated that the PrP genotype strongly influences the host susceptibility of TSE agents from different species (15)(16)(17). Other studies have indicated that compatibility between PrPc and PrPsc molecules is required for efficient PrPsc accumulation (18)(19)(20)(21)(22). This compatibility requirement suggested that PrPsc and PrPc may interact during PrPsc formation as had been proposed earlier (3,23,24).…”

mentioning

confidence: 70%

Species specificity in the cell-free conversion of prion protein to protease-resistant forms: a model for the scrapie species barrier.

Kocisko¹,

Priola²,

Raymond³

et al. 1995

311

210

Scrapie is a transmissible neurodegenerative disease that appears to result from an accumulation in the brain of an abnormal protease-resistant isoform of prion protein (PrP) called PrPsc. Conversion of the normal, protease-sensitive form of PrP (PrP9) to protease-resistant forms like PrPsc has been demonstrated in a cell-free reaction composed largely of hamster PrPc and PrPsc. We now report studies of the species specificity of this cell-free reaction using mouse, hamster, and chimeric PrP molecules. Combinations of hamster PrPc with hamster PrPsc and mouse PrPc with mouse PrPsc resulted in the conversion of PrPc to proteaseresistant forms. Protease-resistant PrP species were also generated in the nonhomologous reaction of hamster PrPc with mouse PrPsc, but little conversion was observed in the reciprocal reaction. Glycosylation of the PrPc precursors was not required for species specificity in the conversion reaction.The relative conversion efficiencies correlated with the relative transmissibilities of these strains of scrapie between mice and hamsters. Conversion experiments performed with chimeric mouse/hamster PrPc precursors indicated that differences between PrPC and PrPsc at residues 139, 155, and 170 affected the conversion efficiency and the size of the resultant protease-resistant PrP species. We conclude that there is species specificity in the cell-free interactions that lead to the conversion of PrPc to protease-resistant forms. This specificity may be the molecular basis for the barriers to interspecies transmission of scrapie and other transmissible spongiform encephalopathies in vivo.

“…This raises the questions of whether the preferred intermediates contain one or both variants and whether one variant can inhibit fibrillization of another. This issue has been approached experimentally for other amyloidogenic proteins by using peptide models of A␤ variants and the polymorphic forms of the prion protein (27,44). The kinetic data discussed above could be reconciled with the genetic data by a mechanism in which a nonfibrillar pathogenic oligomer accumulates in both mixed incubations.…”

Section: Discussionmentioning

confidence: 99%

“…Both methods of fibril quantitation showed a distinct lag phase for fibril formation, which is typical of amyloid fibrillizations and suggests that fibril formation may be nucleation-dependent ( Fig. 1) (22)(23)(24)(25)(26)(27). Consistent with that proposal, addition of preformed ␣-synuclein fibrils comprising WT, A53T, or A30P (1-2% by moles) to an incubation containing the identical protein resulted in a significant reduction in the lag time for appearance of a Thio T signal (lag time for A53T at 200 M is ca.…”

Section: Fibril Formation Is Nucleation-dependent and Can Be Seeded Bymentioning

confidence: 99%

Acceleration of oligomerization, not fibrillization, is a shared property of both α-synuclein mutations linked to early-onset Parkinson's disease: Implications for pathogenesis and therapy

Conway

Lee

Rochet

et al. 2000

Self Cite

1,450

1,283

The Parkinson's disease (PD) substantia nigra is characterized by the presence of Lewy bodies containing fibrillar ␣-synuclein. Earlyonset PD has been linked to two point mutations in the gene that encodes ␣-synuclein, suggesting that disease may arise from accelerated fibrillization. However, the identity of the pathogenic species and its relationship to the ␣-synuclein fibril has not been elucidated. In this in vitro study, the rates of disappearance of monomeric ␣-synuclein and appearance of fibrillar ␣-synuclein were compared for the wild-type (WT) and two mutant proteins, as well as equimolar mixtures that may model the heterozygous PD patients. Whereas one of the mutant proteins (A53T) and an equimolar mixture of A53T and WT fibrillized more rapidly than WT ␣-synuclein, the other (A30P) and the corresponding equimolar mixture with WT fibrillized more slowly. However, under conditions that ultimately produced fibrils, the A30P monomer was consumed at a comparable rate or slightly more rapidly than the WT monomer, whereas A53T was consumed even more rapidly. The difference between these trends suggested the existence of nonfibrillar ␣-synuclein oligomers, some of which were separated from fibrillar and monomeric ␣-synuclein by sedimentation followed by gel-filtration chromatography. Spheres (range of heights: 2-6 nm), chains of spheres (protofibrils), and rings resembling circularized protofibrils (height: ca. 4 nm) were distinguished from fibrils (height: ca. 8 nm) by atomic force microscopy. Importantly, drug candidates that inhibit ␣-synuclein fibrillization but do not block its oligomerization could mimic the A30P mutation and thus may accelerate disease progression.amyloid ͉ aggregation ͉ protofibril ͉ atomic force microscopy (AFM) P arkinson's disease (PD) is an age-related neurodegenerative disorder characterized by difficulty in initiating movements, rigidity, and resting tremor (1). In PD, neuronal death is localized to dopaminergic neurons in the substantia nigra region of the brain stem and precedes appearance of symptoms; ca. 70% of neurons may have died by the time symptoms become apparent (1). The postmortem PD substantia nigra is characterized by sporadic intraneuronal cytoplasmic inclusions known as Lewy bodies (LB), the fibrous portion of which contains the protein ␣-synuclein (2, 3). Lewy bodies themselves could be neurotoxic, analogous to the proposed toxicity of amyloid plaques in Alzheimer's disease (AD) (4); the frequency of cortical Lewy bodies correlates with the severity of the AD-like dementia diffuse Lewy body disease (5). Alternatively, Lewy bodies may be an epiphenomenon, induced by neuronal death. Finally, it is possible that Lewy bodies are an inert end point of a process that, early on, produces a neurotoxic species. This scenario would predict that Lewy body formation may protect against neuronal death by sequestering the toxic species. Two neuropathological observations may be relevant to this issue.First, inclusion-bearing neurons appear to be more healthy than neighboring ...