Author: Christopher Sackmann
Publisher: Linköping University Electronic Press
ISBN: 917519015X
Category :
Languages : en
Pages : 76
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Book Description
Neurodegenerative diseases such as Alzheimer’s disease (AD), Parkinson’s disease (PD), frontotemporal lobar dementia (FTLD) and amyotrophic lateral sclerosis (ALS) are disorders characterized by the progressive deposition of proteinaceous inclusions throughout the brain in a predictable manner. Each disease is described by the involvement of different misfolded and aggregated proteins (AD, amyloid-? and tau; PD, ?-synuclein; ALS and FTLD, TDP-43) that spread between anatomically connected brain regions, causing cell death in previously healthy regions. Disease progresses as these aggregated proteins spread throughout the brain in a prion-like fashion. Oligomeric forms of these proteins (aggregates comprising of ?3-30 individual proteins) are thought to be the most relevant to disease, as they are capable of prion-like propagation and can cause cellular toxicity. The work in this thesis aims to elucidate the mechanisms by which different neurodegenerative disease related proteins (amyloid-?, ?-synuclein and TDP-43) are taken up and transferred between cells, and the effects exerted by these proteins on downstream cells. Paper I examined the uptake and cell to cell transmission of oligomeric ?-synuclein (?-syn). Using a 3D co-culture model, we determined that ?-syn (monomeric, oligomeric and fibrillar assemblies) were readily taken up and transferred between neuron-like cells, and that this transfer was mediated by an endosomal/lysosomal mechanism. It was also determined that larger ?-syn assemblies (oligomers and fibrils) were found in donor and acceptor cells more frequently than monomeric ?-syn, which we speculate is a due to the larger aggregates’ resistance to cellular proteases. In Paper II, we identified a novel mechanism for the uptake of oligomeric proteins, in the discovery that the gap junction channel protein connexin 32 mediates the uptake of ?-syn oligomers in a preferential manner. Gap junction proteins act as a means of communication between adjacent cells, forming a transmembrane pore to facilitate the passage of small molecules. Here, we determined that connexin 32 drives the preferential uptake of oligomeric ?-syn relative to monomeric and fibrillar ?-syn. This system was not exclusive to ?-syn however, as the preferential uptake of oligomeric amyloid-? (A?) was also observed. In addition to the uptake of oligomers, we observed that increased ?-syn expression elicited the increased expression of connexin 32, in a positive feedback mechanism. When connexin 32 was inhibited pharmacologically or knocked out using CRISPR/Cas9, the preferential uptake of oligomers was abolished. These phenomena were also observed in oligodendrocytes (the accumulation of oligomeric ?-syn in oligodendrocytes is a hallmark of Multiple Systems Atrophy), three different mouse models of ?-syn overexpression, as well as in post-mortem human tissues. Paper III undertook the investigation of cell to cell transfer of TDP-43. Although it was recently confirmed that TDP-43 propagates throughout the brain in a prion-like fashion, it remains unclear how post-translational modifications of TDP-43 affect its propensity to be transferred between cells. This leaves a gap in the understanding of how TDP-43 proteinopathies progress, as post-translationally modified TDP-43 is understood to be critical to pathogenesis. To study this, we generated several TDP-43 cell lines, expressing full-length TDP-43 or C-/N-terminally truncated fragments, known contributors to TDP-43 proteinopathies. Using the 3D co-culture model, we determined that preservation of the N-terminus of TDP-43 enhanced its ability to transmit between cells, whereas an intact the C-terminus reduced transfer. Additionally, since we have previously shown that both oligomeric A? and ?-syn are incorporated into extracellular vesicles (EVs) such as exosomes, and that these EVs can sufficiently mediate the transfer of protein oligomers to downstream cells, we investigated whether this was also true for TDP-43. We demonstrated that full-length TDP-43 and TDP-43 fragments could be found within EVs generated by these cells, but that these EVs were unable to propagate the protein to downstream cells. Instead, the transmission of TDP-43 occurs in a manner dependent upon physical proximity between cells, possibly across the synaptic cleft itself. Next, we studied the acute effects exerted by oligomeric A? upon healthy neurons in order to understand the earliest effects of oligomeric A? challenge. In Paper IV, we used iPSC-derived neurons generated from human donors expressing different amyloid-? precursor protein (APP) genes, one harbouring the familial AD-causing V717I London mutation, the other expressing WT APP. After differentiating these cells into functional neurons in vitro, the neurons were challenged with acute exposure to exogenous oligomeric A? and analyzed by LC-MS/MS to observe the early effects. By analyzing the proteome and phosphoproteome of these cells, we identified many proteins and phosphoproteins that were up- or down-regulated in response to oligomeric A? at this early timepoint. Among these changes, oligomeric A? caused the downregulation of TDP-43, heterogeneous nuclear ribonucleoproteins, and coatomer complex I proteins. Conversely, increases were observed in 20S proteasome subunits and vesicle associated proteins VAMP1/2. We also observed the differential phosphorylation of tau at serine 208, indicating that phosphorylation at this residue might be an important early event in tauopathy. Altogether, the work described in this thesis has provided new understanding as to how different neurodegenerative disease related proteins are taken up and transferred between cells. In doing so, we have identified some of the mechanisms by which this spreading occurs, and that the changes elicited by these toxic oligomeric proteins are rapid and widespread. By learning about these processes, we have identified novel targets that could be used in the development of disease modifying therapeutics.
Author: Hardy J. Rideout
Publisher: Springer
ISBN: 3319499696
Category : Medical
Languages : en
Pages : 280
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Book Description
This is the first book to assemble the leading researchers in the field of LRRK2 biology and neurology and provide a snapshot of the current state of knowledge, encompassing all major aspects of its function and dysfunction. The contributors are experts in cell biology and physiology, neurobiology, and medicinal chemistry, bringing a multidisciplinary perspective on the gene and its role in disease. The book covers the identification of LRRK2 as a major contributor to the pathogenesis of Parkinson's Disease. It also discusses the current state of the field after a decade of research, putative normal physiological roles of LRRK2, and the various pathways that have been identified in the search for the mechanism(s) of its induction of neurodegeneration.
Author: Mathias Jucker
Publisher: Springer Science & Business Media
ISBN: 3642354912
Category : Medical
Languages : en
Pages : 163
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Book Description
The misfolding and aggregation of specific proteins is an early and obligatory event in many of the age-related neurodegenerative diseases of humans. The initial cause of this pathogenic cascade and the means whereby disease spreads through the nervous system, remain uncertain. A recent surge of research, first instigated by pathologic similarities between prion disease and Alzheimer’s disease, increasingly implicates the conversion of disease-specific proteins into an aggregate-prone b-sheet-rich state as the prime mover of the neurodegenerative process. This prion-like corruptive protein templating or seeding now characterizes such clinically and etiologically diverse neurological disorders as Alzheimer ́s disease, Parkinson’s disease, Huntington’s disease, amyotrophic lateral sclerosis, and frontotemporal lobar degeneration. Understanding the misfolding, aggregation, trafficking and pathogenicity of the affected proteins could therefore reveal universal pathomechanistic principles for some of the most devastating and intractable human brain disorders. It is time to accept that the prion concept is no longer confined to prionoses but is a promising concept for the understanding and treatment of a remarkable variety of diseases that afflict primarily our aging society.
Author: Valerie Sackmann
Publisher: Linköping University Electronic Press
ISBN: 9175190125
Category :
Languages : en
Pages : 69
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Book Description
Alzheimer’s disease (AD) and Parkinson’s disease (PD) are the two most common neurodegenerative diseases with rates increasing along with the ageing global population. Despite best efforts, we still do not understand the etiopathogenesis of these diseases and there are no effective disease-modifying treatments. Cognitive deficiencies or motor complications that emerge during AD and PD are thought to be the result of the accumulation of misfolded, aggregate-prone proteins, such as amyloid-? (A?) and tau or ?-synuclein (?-syn), respectively. Growing evidence suggests that prefibrillar oligomers of A? and ?-syn (oA? and o?-syn) are key contributors to the progression of these diseases. The progressive accumulation of these proteins leads to a gradual spread of pathology throughout interconnected brain regions, but the mechanisms by which this spreading occurs are still largely unknown. Neuroinflammation has been recognised as an important contributor to neurodegenerative disease. It is hypothesised that a pro-inflammatory environment initiated by the innate immune system, either through activation from A? itself or indirectly through neuronal injury signals in AD. These phenomena are thought to either cause or accelerate AD, such that an anti-inflammatory approach may be neuroprotective. In paper I, we investigated whether different inflammatory environments affected the transfer of oA? between neuron-like cells, in addition to investigating inter- and intracellular protein changes. This study demonstrated that an anti-inflammatory environment reduces the transfer of oA? between cells. We also provide evidence that these cells begin to take on the “phenotype” of the inflammatory milieu, while also demonstrating that the expression profile of endosomal/lysosomal and protein trafficking proteins is altered during these conditions. Small extracellular vesicles called exosomes, which are key players in cell to cell communication, have been proposed to play an influential role in spreading neurodegenerative proteins between cells. Exosomes are small membranous vesicles that are formed by the inward budding of multivesicular bodies (MVBs). These MVBs can then merge with the plasma membrane to be released into the extracellular environment as vesicles, which serve as vehicles for transferring proteins, lipids, and mRNAs between cells. The ESCRT-dependent pathway is the most understood mechanism underlying exosome biogenesis. However, exosomes can also be formed through ESCRT-independent pathways, including through the hydrolysis of sphingomyelin by neutral sphingomyelinase 2 (nSMase2), which produces ceramide. Paper II investigated whether exosomes formed through an ESCRT-independent pathway plays a significant role in the transfer of o?-syn between neuron-like cells. As oxidative stress is a common feature in PD brains, which in turn dysregulates nSMase2 activity, we also tested our model under hypoxic conditions. Inhibition of nSMase2 significantly reduced the transfer of o?-syn between cells but also resulted in decreased ?-syn aggregation. Hypoxia did not influence o?-syn transfer, however, it significantly dysregulated the sphingolipid composition, which may be important for ?-syn binding to exosomes and exosome communication. During AD and PD, there is a noted reduction in the effectiveness of autophagy, a process critical to cellular proteostasis. Recent studies have uncovered shared regulatory mechanisms of exosome biogenesis and autophagy, suggesting that they are closely linked. Previous findings have shown that inhibition of autophagy in AD mice mediates A? trafficking through altering the secretion of A? in MVBs. To further study this effect, we investigated the interplay between autophagy and exosome secretion using ATG7 knock-out x APPNL-F knock-in AD mice in paper III. These autophagy-deficient AD mice had a reduced extracellular A? plaque load, but increased intracellular A?, which was found to be assembled into higher-ordered assemblies. While exosomal secretion was dysregulated in these mice, the amount of A? packaged into the exosomes was unchanged. Lastly, one of the biggest challenges in developing effective treatments for AD is the lack of early diagnosis of living patients. As the connection between exosomes and the spread of neurodegenerative proteins is still relatively new, there remains a diagnostic potential to be explored with exosomes. Paper IV aimed to develop a new diagnostic assay to detect oA? in exosomes isolated from human cerebrospinal fluid. Although exosomal oA? was readily detected in some of these samples, the assay’s sensitivity requires additional optimisation before it can be further validated for the clinic. In summary, the studies presented in this thesis have furthered our understanding of how inflammation, autophagy, and exosomes contribute to the intercellular transmission of AD and PD associated proteins. We have shown that an anti-inflammatory approach may slow down the progression of AD through reducing the transfer of oA? between cells. We also provide novel findings relating to the biogenesis of exosomes, which in turn affected the ability of exosomes to transmit neurodegenerative proteins between cells, and their association with autophagic processes. Finally, we have investigated the feasibility of exosomes as an early AD diagnostic marker. This work has helped to elucidate some of the mechanisms underlying the progression of neurodegenerative diseases, which may be useful targets for the investigation of new therapeutic avenues.
Author: Diana Fernandes Lázaro
Publisher: Frontiers Media SA
ISBN: 2889635074
Category :
Languages : en
Pages : 158
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Book Description
This eBook is a collection of articles from a Frontiers Research Topic. Frontiers Research Topics are very popular trademarks of the Frontiers Journals Series: they are collections of at least ten articles, all centered on a particular subject. With their unique mix of varied contributions from Original Research to Review Articles, Frontiers Research Topics unify the most influential researchers, the latest key findings and historical advances in a hot research area! Find out more on how to host your own Frontiers Research Topic or contribute to one as an author by contacting the Frontiers Editorial Office: frontiersin.org/about/contact.
Author: V.M.-Y. Lee
Publisher: Springer Science & Business Media
ISBN: 9783540671725
Category : Medical
Languages : en
Pages : 164
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Book Description
In this volume are contributions based on a meeting arranged by the WHO and the Fondation IPSEN. The scientists focus on neurodegenerative disorders like Alzheimer's Disease, Chromosome 17-Linked Dementia, Parkinson's Disease and disorders with tauopathies.
Author: Kim A. Staats
Publisher: Frontiers Media SA
ISBN: 288971182X
Category : Science
Languages : en
Pages : 183
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Book Description
Author: Jesus Avila
Publisher: Frontiers E-books
ISBN: 288919261X
Category : Medicine (General)
Languages : en
Pages : 114
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Book Description
Neurofibrillary tangles (NFTs) composed of intracellular aggregates of tau protein are a key neuropathological feature of Alzheimer’s Disease (AD) and other neurodegenerative diseases, collectively termed tauopathies. The abundance of NFTs has been reported to correlate positively with the severity of cognitive impairment in AD. However, accumulating evidences derived from studies of experimental models have identified that NFTs themselves may not be neurotoxic. Now, many of tau researchers are seeking a “toxic” form of tau protein. Moreover, it was suggested that a “toxic” tau was capable to seed aggregation of native tau protein and to propagate in a prion-like manner. However, the exact neurotoxic tau species remain unclear. Because mature tangles seem to be non-toxic component, “tau oligomers” as the candidate of “toxic” tau have been investigated for more than one decade. In this topic, we will discuss our consensus of “tau oligomers” because the term of “tau oligomers” [e.g. dimer (disulfide bond-dependent or independent), multimer (more than dimer), granular (definition by EM or AFM) and maybe small filamentous aggregates] has been used by each researchers definition. From a biochemical point of view, tau protein has several unique characteristics such as natively unfolded conformation, thermo-stability, acid-stability, and capability of post-translational modifications. Although tau protein research has been continued for a long time, we are still missing the mechanisms of NFT formation. It is unclear how the conversion is occurred from natively unfolded protein to abnormally mis-folded protein. It remains unknown how tau protein can be formed filaments [e.g. paired helical filament (PHF), straight filament and twisted filament] in cells albeit in vitro studies confirmed tau self-assembly by several inducing factors. Researchers are still debating whether tau oligomerization is primary event rather than tau phosphorylation in the tau pathogenesis. Inhibition of either tau phosphorylation or aggregation has been investigated for the prevention of tauopathies, however, it will make an irrelevant result if we don’t know an exact target of neurotoxicity. It is a time to have a consensus of definition, terminology and methodology for the identification of “tau oligomers”.
Author: Claudia Duran-Aniotz
Publisher: Frontiers Media SA
ISBN: 2889746070
Category : Science
Languages : en
Pages : 265
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Book Description
Author: Udo Rüb
Publisher: Springer
ISBN: 331919285X
Category : Medical
Languages : en
Pages : 154
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Book Description
This monograph describes the progress in neuropathological HD research made during the last century, the neuropathological hallmarks of HD and their pathogenic relevance. Starting with the initial descriptions of the progressive degeneration of the striatum as one of the key events in HD, the worldwide practiced Vonsattel HD grading system of striatal neurodegeneration will be outlined. Correlating neuropathological data with results on the functional neuroanatomy of the human brain, subsequent chapters will highlight recent HD findings: the neuronal loss in the cerebral neo-and allocortex, the neurodegeneration of select thalamic nuclei, the affection of the cerebellar cortex and nuclei, the involvement of select brainstem nuclei, as well as the pathophysiological relevance of these pathologies for the clinical picture of HD. Finally, the potential pathophysiological role of neuronal huntingtin aggregations and the most important and enduring challenges of neuropathological HD research are discussed.
