1,721,013 research outputs found
NMR studies of human prion proteins with inherited mutations
No full textPrion diseases are fatal neurodegenerative disorders caused by an aberrant accumulation of the misfolded cellular prion protein (PrPC) conformer, denoted as infectious scrapie isoform or PrPSc. Our understanding of the mechanisms by which mutations cause disease remains limited. In this work results of recent high-resolution NMR structural studies on human prion protein variants carrying pathological mutations are presented
Structural rearrangements at physiological pH: Nuclear magnetic resonance insights from the V210I human prion protein mutant
No full textA major focus in prion structural biology studies is unraveling the molecular mechanism leading to the structural conversion of PrP(C) to its pathological form, PrP(Sc). In our recent studies, we attempted to understand the early events of the conformational changes leading to PrP(Sc) using as investigative tools point mutations clustered in the open reading frame of the human PrP gene and linked to genetic forms of human prion diseases. In the work presented here, we investigate the effect of pH on the nuclear magnetic resonance (NMR) structure of recombinant human PrP (HuPrP) carrying the pathological V210I mutation responsible for familial Creutzfeldt-Jakob disease. The NMR structure of HuPrP(V210I) determined at pH 7.2 shows the same overall fold as the previously determined structure of HuPrP(V210I) at pH 5.5. It consists of a disordered N-terminal tail (residues 90-124) and a globular C-terminal domain (residues 125-231) comprising three α-helices and a short antiparallel β-sheet. Detailed comparison of three-dimensional structures of HuPrP(V210I) at pH 7.2 and 5.5 revealed significant local structural differences, with the most prominent pH-related structural variations clustered in the α(2)-α(3) interhelical region, at the interface of the β(1)-α(1) loop, in helices α(1) and α(3), and in the β(2)-α(2) loop region. The detailed analysis of interactions among secondary structure elements suggests a higher degree of structural ordering of HuPrP(V210I) under neutral-pH conditions, thus implying that spontaneous misfolding of PrP(C) may occur under acidic-pH conditions in endosomal compartments
Structural basis for the protective effect of the human prion protein carrying the dominant-negative E219K polymorphism
No full textThe most common form of prion disease in humans is sporadic Creutzfeldt-Jakob disease (sCJD). The naturally occurring E219K polymorphism in the human prion protein (HuPrP) is considered to protect against sCJD. To gain insights into the structural basis of its protective influence we have determined the NMR structure of the recombinant HuPrP (residues 90-231) carrying the E219K polymorphism. The structure of the HuPrP(E219K) protein consists of a disordered N-terminal tail (residues 90-124) and a well-structured C-terminal (residues 125-231) containing three a-helices and two short antiparallel b-strands. Comparison between NMR structures of the wild-type (WT) and HuPrPs with pathological mutations under identical experimental conditions revealed that, although the global architecture of the protein remains intact, Glu219 to Lys substitution introduces significant local structural changes. Our structural findings suggest that the protective influence of the E219K polymorphism is due to the alteration of surface charge distribution, in addition to subtle structural rearrangements localized within the epitopes critical for prion conversion
A single point mutation, a way to prion disease?
No full textPrion diseases or Transmissible Spongiform Encephalopathies (TSE) are a group of fatal neurodegenerative illnesses affecting humans and animals. They are classified into sporadic, genetic and infectious forms. Genetic prion diseases are caused by mutations in the human prion protein gene and include Gerstmann-Straussler-Scheinker (GSS) syndrome, Fatal Familial Insomnia and genetic Creutzfeldt-Jakob disease (CJD). Approximately 10-15% of all TSE cases in humans are associated with mutations. The development of TSEs is associated with the conversion of the cellular prion protein (PrPC) into a misfolded, pathogenic isoform (PrPSc). Our recent NMR studies were focused on structural characterization of different truncated recombinant human (Hu) PrPs carrying the pathological Q212P (90-231, M129) and V210I(90-231, M129) mutations, and protective E219K (90-231, M129) polymorphism. While Q212P mutation is linked to GSS, the V210I mutation is linked to genetic CJD. The naturally occurring E219K polymorphism in the HuPrP is considered to protect against sCJD. We have demonstrated that the determined structures of variants consist of unstructured N-terminal part (residues 90-124) and well defined C-terminal domain (residues 125-228). Analysis and comparison with the structure of the WT HuPrP revealed that although structures share similar global fold, mutations introduces several local structural differences. The observed differences are mostly clustered at the alpha2-alpha3 inter-helical interface and in the beta2-alpha2 loop region. The determined NMR structures offer new insights on the earliest events of the pathogenic conversion process and could be used for the development of antiprion drugs. More recently we have determined solution state structures of V210I (90-231, M129) pathogenic mutation at two different conditions with pH 5.5 and 7.2. The detailed comparison of three-dimensional structures of HuPrP(V210I) at two different pH values revealed that interactions among secondary structure elements have a higher degree of structural ordering under neutral pH conditions, thus implying that spontaneous misfolding of PrPC may occur under acidic-pH conditions in endosomal compartments
NMR Structural Studies of Human Cellular Prion Proteins
No full textPrion diseases or transmissible spongiform encephalopathies (TSEs) are fatal neurodegenerative disorders associated with the conformational conversion of the cellular prion protein, PrPC, into a pathological form known as prion or PrPSc. They can be classified into sporadic, inherited and infectious forms. Spontaneous generation of PrPSc in inherited forms of prion diseases is caused by mutations in the human prion protein gene (PRNP). A major goal in prion biology is unraveling the molecular mechanism by which PrPC misfolds and leads to development of diseases. Structural characterization of various human PrP (HuPrP) variants may be helpful for better understanding of the earliest stages of the conformational changes leading to spontaneous generation of prions. Here, we review the results of the recent high-resolution nuclear magnetic resonance (NMR) structural studies on HuPrPs with pathological Q212P and V210I mutations linked with Gerstmann-Sträussler-Scheinker (GSS) syndrome and familial Creutzfeldt-Jakob disease (fCJD), respectively, and HuPrP carrying naturally occurring E219K polymorphism considered to protect against sporadic CJD (sCJD). We describe subtle local differences between the three-dimensional (3D) structures of HuPrP mutants and the wild-type (WT) protein, providing new insights into the possible key structural determinants underlying conversion of PrPC into PrPSc. Also highlighted are the most recent findings from NMR studies about the effect of pH on the structural features of HuPrP with V210I mutation
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
NMR studies of human prion protein mutants in solution
No full textTransmissible spongiform encephalopathies (TSEs) are a rare group of rapidly progressive, invariably fatal neurodegenerative diseases affecting humans and animals. A hallmark of TSEs is the conformational conversion of the physiological cellular prion protein, PrPC, into a disease-associated form known as prion or PrPSc. A major focus in prion biology is unraveling the molecular mechanism leading to the structural conversion of PrPC to its pathological form PrPSc. In our recent studies, we tried to understand the early events of the conformational changes leading to PrPSc using as investigative tools point mutations clustered in the open reading frame of the human PrP gene and linked to genetic forms of human prion diseases. We have determined high-resolution solution-state NMR structures of the truncated recombinant human (Hu) PrP (residues 90-231) with pathological Q212P and V210I mutations linked to Gerstmann-Sträussler-Scheinker (GSS) syndrome and genetic Creutzfeldt–Jakob disease (CJD), respectively. In addition, we examined the NMR structure of the recombinant HuPrP (residues 90-231) carrying naturally occurring E219K polymorphism considered to protect against sporadic CJD (sCJD). 3D structures of HuPrP(Q212P), HuPrP(V210I) and HuPrP(E219K) proteins share similar global architecture with the WT HuPrP consisting of highly flexible N-terminal tail and a well-structured C-terminal domain, the latter containing three alpha-helices and a short antiparallel beta-sheet. Detailed inspection revealed that pathological Q212P and V210I mutations introduce some local structural variations with respect to the WT HuPrP which are mostly clustered at the alpha2-alpha3 interhelical interface and in the beta2-alpha2 loop region. Alteration of conformation of the beta2-alpha2 loop region and subsequent higher exposure of hydrophobic residues to solvent may facilitate intermolecular interactions involved in spontaneous generation of PrPSc in genetic TSEs. On contrary to the HuPrP(Q212P) and HuPrP(V210I), the structure of HuPrP(E219K) does not point to interruption of aromatic and hydrophobic interactions in the beta2-alpha2 loop region. Noteworthy, it seems that the beta2-alpha2 loop in HuPrP(E219K) is somewhat better defined in comparison to the same region in the WT protein and proteins with pathological Q212P and V210I mutations. In addition to such subtle structural rearrangements localized within the epitopes critical for prion conversion, replacement of Glu219 by Lys induces significant alteration of surface charge distribution with respect to the WT protein what may further account for protective influence of E219K polymorphism against sCJD
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Solution NMR structures of disease-linked human prion protein mutants
No full textPrion diseases or transmissible spongiform encephalopathies (TSEs) are a group of rare neuropathies characterized by a spongiform neurodegeneration of the central nervous system caused by prions. These disorders include Creutzfeldt–Jakob disease (CJD), Gerstmann-Sträussler-Scheinker (GSS) syndrome, Fatal Familial Insomnia and kuru in humans, bovine spongiform encephalopathy in cattle, scrapie in sheep and goats, and chronic wasting disease in elk, deer and moose. Prions are thought to consist solely of a misfolded isoform (PrPSc) of the normal, host-encoded cellular protein (PrPC), whose function is still unknown. Human (Hu) PrPC is a 209 residues long glycoprotein, tethered to the outer leaflet of the plasma membrane by a glycosylphosphatidylinositol (GPI) anchoring and its primary structure is highly conserved among mammals. According to the „protein-only hypothesis‟, during the course of prion diseases, PrPC is converted into the abnormal form by a conversion process whereby most α-helix motives are replaced by β-sheet secondary structures. One of the strongest arguments supporting the „protein-only hypothesis‟ is the link between inherited prion diseases and mutations in the PRNP gene. In our recent studies, we have determined the NMR solution-state structures of the truncated recombinant human (Hu) PrPs carrying the pathological Q212P (90-231, M129) 1 and V210I (90-231, M129) 2 mutations linked to GSS and genetic CJD, respectively. In order to determine high-resolution structures triple resonance (1H, 13C and 15N) NMR experiments were performed using 800 MHz NMR spectrometer. The determined structures of both mutants consist of unstructured N-terminal part (residues 90-124) and well-defined C-terminal domain (residues 125-228). The C-terminal part contains
- …
