Cellular mechanisms in prion-mediated neurodegeneration

Prion diseases are fatal neurodegenerative disorders of both humans and other animals. The cause of prion-mediated neurodegeneration by conversion of the normal cellular prion protein (PrPC) to the disease-related isoform (PrPSc) remains unknown. Increasing evidence suggests a role for the ubiquitin proteasome system (UPS) in prion disease. PrPC and PrPSc isoforms have been shown to accumulate in cells after proteasome inhibition, leading to increased cell death. The aim of this thesis was to investigate the role of cellular degradation systems, such as the UPS and autophagy, in prion-mediated cell death. In UPS-mediated degradation poly-ubiquitinated substrates get degraded by the 26S proteasome, which comprises a 20S hydrolytic core and a 19S regulatory particle. Using a variety of biochemical methods, I report that abnormal beta-sheet-rich PrP isoforms inhibit the catalytic activity of the 26S proteasome, by specifically inhibiting its beta1 and beta5 proteolytic subunits. Pre-incubating these PrP isoforms with an antibody raised against aggregation intermediates abrogates the inhibitory effect seen, consistent with an ‘oligomeric’ inhibitory species. Using open-gated yeast 20S proteasome mutants and conserved 19S ATPase C-terminal peptides containing an essential motif for gate-opening, this thesis describes findings supporting an inhibitory effect on proteasomal gating rather than a direct inhibitory effect on the active sites of the 20S proteasome. These C-terminal peptides open the gate in a ‘key in a lock’ fashion by docking into inter-subunit pockets in the alpha-ring of the 20S proteasome. In this system, the inhibitory effect of the beta-sheet-rich PrP isoforms may be due to abnormal PrP competing with the C-terminal peptides for the inter-subunit pockets, thereby preventing gate-opening. Proteins are also degraded by autophagy, a degradation pathway that has not been adequately characterised in prion disease. This thesis investigates potential roles autophagy may play in prion disease. Data presented here suggest that a) prions are cleared by autophagy, b) prion-infected cells have higher numbers of autophagosomes compared to uninfected controls, c) induction of autophagy ameliorates cell death after proteasome inhibition, indicating cross-talk between the two protein-degradation pathways, and d) it is up-regulated in vivo at end-stage prion disease

The structure of blocks with a Klein four defect group

We prove Erdmann’s conjecture [16] stating that every block with a Klein four defect group has a simple module with trivial source, and deduce from this that Puig’s finiteness conjecture holds for source algebras of blocks with a Klein four defect group. The proof uses the classification of finite simple groups

Proteomic analysis of FOXP proteins reveals interactions between cortical transcription factors associated with neurodevelopmental disorders

FOXP transcription factors play important roles in neurodevelopment, but little is known about how their transcriptional activity is regulated. FOXP proteins cooperatively regulate gene expression by forming homo- and hetero-dimers with each other. Physical as

Blocks with transitive fusion systems

Suppose that all nontrivial subsections of a $p$-block $B$ are conjugate (where $p$ is a prime). By using the classification of the finite simple groups, we prove that the defect groups of $B$ are either extraspecial of order $p^3$ with $p \in \{3,5\}$ or elementary abelian

Shaman, Sage, Priest, Prophet and Magician: Exploring the Architecture of the Religious Wise Man

Little attention has been given to the archetype of the wise old man, both by Carl G. Jung and by contemporary scholars indebted to his methodology. This is especially relevant when compared to other common Jungian archetypes such as the ‘hero’, the ‘mother’ and the ‘trickster.’ As such, the wise man can be viewed as a neglected or overlooked figure whose image is so familiar and recognisable that his purpose and representations have not currently received the depth of analysis and explanation that has been given to other archetypal images. This thesis identifies the religious wise man as an important figure within the contexts of culture and religion. Its aim is to not only to explore the ‘archetype’ of the wise man, but to go beyond that rather superficial – and indeed, academically problematic – notion, and determine what I term the ‘architecture’ of the wise man. This architecture consists of the structural elements (social, institutional, historical) and identifiers (costume, calling, education), that separate the wise man, and in particular the religious wise man, from other male ‘archetypal’ figures. In using the term ‘architecture’ I aim to identify the arrangement of concrete elements and characteristics - rather than psychological or inner ‘essences’ - which are significant in the construction and maintenance of the religious wise man figure in specific cultural contexts. The dissertation presents five possible categories of the religious wise man - the shaman, sage, priest, prophet and magician – identifying common elements and distinguishing features that may then be redesigned and adapted in different and unique forms appropriate to each manifestation of the religious wise man. Once these key characteristics are identified, they create a schema that can be employed to classify a range of religious wise man figures into the appropriate category

The Brauer complex and its applications to the Chevalley groups

This thesis, is concerned with the determination of the connected centralizers of semi-simple elements in a Chevalley group. To deal with this problem we shall use the recent work of R. Carter [6] and a new tool for the study of algebraic groups - the so called Brauer complex. This complex has been first defined by J. Humphreys [11] in the context of the modular representation theory of the finite Chevalley groups of universal type. Now, in our version, the Brauer complex can be also used for the ordinary representation theory of the finite Chevalley groups of adjoint type. For, Deligne and Lusztig in their fundamental work [9] have constructed for these groups certain families of irreducible complex representations whose degrees can be obtained if we know what subgroups of the finite Chevalley groups are the connected centralizers of semi-simple elements

Overlapping SETBP1 gain-of-function mutations in Schinzel-Giedion syndrome and hematologic malignancies

Schinzel-Giedion syndrome (SGS) is a rare developmental disorder characterized by multiple malformations, severe neurological alterations and increased risk of malignancy. SGS is caused by de novo germline mutations clustering to a 12bp hotspot in exon 4 of SETBP1. Mutations in this hotspot disrupt a degron, a signal for the regulation of protein degradation, and lead to the accumulation of SETBP1 protein. Overlapping SETBP1 hotspot mutations have been observed recurrently as somatic events in leukemia. We collected clinical information of 47 SGS patients (including 26 novel cases) with germline SETBP1 mutations and of four individuals with a milder phenotype caused by de novo germline mutations adjacent to the SETBP1 hotspot. Different mutations within and around the SETBP1 hotspot have varying effects on SETBP1 stability and protein levels in vitro and in in silico modeling. Substitutions in SETBP1 residue I871 result in a weak increase in protein levels and mutations affecting this residue are significantly more frequent in SGS than in leukemia. On the other hand, substitutions in residue D868 lead to the largest increase in protein levels. Individuals with germline mutations affecting D868 have enhanced cell proliferation in vitro and higher incidence of cancer compared to patients with other germline SETBP1 mutations. Our findings substantiate that, despite their overlap, somatic SETBP1 mutations driving malignancy are more disruptive to the degron than germline SETBP1 mutations causing SGS. Additionally, this suggests that the functional threshold for the development of cancer driven by the disruption of the SETBP1 degron is higher than for the alteration in prenatal development in SGS. Drawing on previous studies of somatic SETBP1 mutations in leukemia, our results reveal a genotype-phenotype correlation in germline SETBP1 mutations spanning a molecular, cellular and clinical phenotype

Molecular evidence of adenosine deaminase linking adenosine A2A receptor and CD26 proteins

Adenosine is an endogenous purine nucleoside that acts in all living systems as a homeostatic network regulator through many pathways, which are adenosine receptor (AR)-dependent and -independent. From a metabolic point of view, adenosine deaminase (ADA) is an essential protein in the regulation of the total intracellular and extracellular adenosine in a tissue. In addition to its cytosolic localization, ADA is also expressed as an ecto-enzyme on the surface of different cells. Dipeptidyl peptidase IV (CD26) and some ARs act as binding proteins for extracellular ADA in humans. Since CD26 and ARs interact with ADA at opposite sites, we have investigated if ADA can function as a cell-to-cell communication molecule by bridging the anchoring molecules CD26 and A2AR present on the surfaces of the interacting cells. By combining site-directed mutagenesis of ADA amino acids involved in binding to A2AR and a modification of the bioluminescence resonance energy transfer (BRET) technique that allows detection of interactions between two proteins expressed in different cell populations with low steric hindrance (NanoBRET), we show direct evidence of the specific formation of trimeric complexes CD26-ADA-A2AR involving two cells. By dynamic mass redistribution assays and ligand binding experiments, we also demonstrate that A2AR-NanoLuc fusion proteins are functional. The existence of this ternary complex is in good agreement with the hypothesis that ADA could bridge T-cells (expressing CD26) and dendritic cells (expressing A2AR). This is a new metabolic function for ecto-ADA that, being a single chain protein, it has been considered as an example of moonlighting protein, because it performs more than one functional role (as a catalyst, a costimulator, an allosteric modulator and a cell-to-cell connector) without partitioning these functions in different subunits

Macroporous silicon filters, a versatile platform for NDIR spectroscopic gas sensing in the MIR

© The Author(s) 2019. Published by ECS. This is an open access article distributed under the terms of the Creative CommonsAttribution 4.0 License (CC BY,http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in anymedium, provided the original work is properly cited.This paper describes the spectroscopic detection of gases using macroporous silicon photonic crystals as narrow filters. The study begins by demonstrating the feasibility of photoelectrochemical etching to fabricate narrow filters along the mid infrared band. Next, we focus on the filter centered on the carbon dioxide fingerprint. The filter response is described for three different cell lengths and concentrations below 1%. Results show a concordance with the reformulated Beer-Lambert law. This can be used to predict the response of the filter for longer path lengths and higher concentrations, showing broad working ranges and compact sizes for CO2. In addition, optical robustness to external variations and long-term stability are also reported. Results are extrapolated to other macroporous silicon filters centered on the absorption spectra of N2O, OCS, NO2 and SO2. Finally, high sensitivity and selectivity is demonstrated by comparing them with some commercial filters.Postprint (published version