A Liquid to Solid Phase Transition Underlying Pathological Huntingtin Exon1 Aggregation

Peskett, Thomas R.; Rau, Frédérique; O’Driscoll, Jonathan; Patani, Rickie; Lowe, Alan R.; Saibil, Helen R.

doi:10.1016/j.molcel.2018.04.007

Cited by 275 publications

(308 citation statements)

References 81 publications

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“…This approach could be extended to image young Q40 nematodes in larval stages at higher resolution, to find out if similar non-amyloid inclusions comprised of e.g. oligomeric 28 or liquid-like states 37 are visible as precursors in this system. For the longitudinal studies described here, we were able to perform the complete set of experiments in less than 2.5 h for each day of measurement (ca.…”

Section: Resultsmentioning

confidence: 99%

Fast fluorescence lifetime imaging reveals the aggregation processes of α-synuclein and polyglutamine in aging Caenorhabditis elegans

Laine

Sinnige

et al. 2018

Preprint

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The nematode worm Caenorhabditis elegans has emerged as an important model organism to study the molecular mechanisms of protein misfolding diseases associated with amyloid formation because of its small size, ease of genetic manipulation and optical transparency. Obtaining a reliable and quantitative read-out of protein aggregation in this system, however, remains a challenge. To address this problem, we here present a fast time-gated fluorescence lifetime imaging (TG-FLIM) method and show that it provides functional insights into the process of protein aggregation in living animals by enabling the rapid characterisation of different types of aggregates. More specifically, in longitudinal studies of C. elegans models of Parkinson's and Huntington's diseases, we observed marked differences in the aggregation kinetics and the nature of the protein inclusions formed by α-synuclein and polyglutamine.In particular, we found that α-synuclein inclusions do not display amyloid-like features until late in the life of the worms, whereas polyglutamine forms amyloid characteristics rapidly in early adulthood.Furthermore, we show that the TG-FLIM method is capable of imaging live and non-anaesthetised worms moving in specially designed agarose micro-chambers. Taken together, our results show that the TG-FLIM method enables high-throughput functional imaging of living C. elegans that can be used to study in vivo mechanisms of aggregation and that has the potential to aid the search for therapeutic modifiers of protein aggregation and toxicity. A variety of human diseases, including neurodegenerative disorders such as Parkinson's andAlzheimer's diseases, are characterised by the misfolding of protein species and their subsequent aggregation into amyloid fibrils 1,2 . The nematode Caenorhabditis elegans is a particularly useful model organism through which to study these diseases 3-8 and to screen for small molecule inhibitors of the protein aggregation process 9,10 . C. elegans has a simple body plan of 959 somatic cells, its genetics are well-characterised, and at least 40% of its genes have known human homologs 11 . Furthermore, it has a relatively short lifespan of only 2-3 weeks and is optically transparent, making it a highly suitable system for longitudinal imaging studies of protein aggregation. Despite these advantages, obtaining quantitative read-outs for amyloidogenic protein aggregation in vivo remains challenging 12 .Fluorescence intensity measurements are prone to artefacts, and classifying aggregates by counting protein inclusions relies on arbitrary choices for intensity and size cut-offs. Furthermore, reliable

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Section: Resultsmentioning

confidence: 99%

Fast fluorescence lifetime imaging reveals the aggregation processes of α-synuclein and polyglutamine in aging Caenorhabditis elegans

Laine

Sinnige

et al. 2018

Preprint

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“…While we know well how cells guard the structure of stably folded proteins [123][124][125][126][127], we know virtually nothing about the mechanisms that guard IDPs. IDPs, including IDPs related to degenerative diseases such as Huntington's disease and amyloid lateral sclerosis, and FG-Nups, can phase separate to form liquid-liquid demixed droplets [128] or hydrogels [129][130][131] or aggregate to form amyloid fibers [64][65][66][132][133][134][135][136].…”

Section: Maintenance Quiescent Muscle Cells Maintain Theirmentioning

confidence: 99%

Poor old pores—The challenge of making and maintaining nuclear pore complexes in aging

2020

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The nuclear pore complex (NPC) is the sole gateway to the nuclear interior, and its function is essential to all eukaryotic life. Controlling the functionality of NPCs is a tremendous challenge for cells. Firstly, NPCs are large structures, and their complex assembly does occasionally go awry. Secondly, once assembled, some components of the NPC persist for an extremely long time and, as a result, are susceptible to accumulate damage. Lastly, a significant proportion of the NPC is composed of intrinsically disordered proteins that are prone to aggregation. In this review, we summarize how the quality of NPCs is guarded in young cells and discuss the current knowledge on the fate of NPCs during normal aging in different tissues and organisms. We discuss the extent to which current data supports a hypothesis that NPCs are poorly maintained during aging of nondividing cells, while in dividing cells the main challenge is related to the assembly of new NPCs. Our survey of current knowledge points toward NPC quality control as an important node in aging of both dividing and nondividing cells. Here, the loss of protein homeostasis during aging is central and the NPC appears to both be impacted by, and to drive, this process.

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“…Relatively dry environments where phenomena equivalent to this can occur include the core of globular proteins 44 , the interior of cell membranes 45 , as well as amyloid fibrils, where hydrogen bonding interactions involving Gln and Asn side chains parallel to the fibril axis contribute to the stability of the quaternary structure 46 . In addition, it has been shown that both exon 1 of huntingtin 47 and the transactivation domain of the AR 48 form condensates that define environments of low dielectric constant, where electrostatic interactions may be strongly favored 49 . It will be interesting to address whether this phenomenon plays a role in the highly cooperative liquidliquid phase separation process of these and similar proteins, as has been proposed to be the case for protein folding, where considering the contextdependent strength of interresidue interactions proved important for reproducing the high cooperativity of protein folding in lattice simulations 50 .…”

Section: Discussionmentioning

confidence: 99%

Side chain to main chain hydrogen bonds stabilize a polyglutamine helix in the activation domain of a transcription factor

Escobedo¹,

Topal²,

Kunze³

et al. 2018

Preprint

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Polyglutamine (polyQ) tracts are regions of low sequence complexity of variable lengthfound in more than one hundred human proteins. These tracts are frequent in activation domains of transcription factors and their length often correlates with transcriptional activity. In addition, in nine proteins, tract elongation beyond specific thresholds causes polyQ disorders. To study the structural basis of the association between tract length, transcriptional activity and disease, here we addressed how the conformation of the polyQ tract of the androgen receptor (AR), a transcription factor associated with the polyQ disease spinobulbar muscular atrophy (SBMA), depends on its length. We found that the tract folds into a helical structure stabilized by unconventional hydrogen bonds between glutamine side chains and main chain carbonyl groups. These bonds are bifurcate with the conventional main chain to main chain hydrogen bonds stabilizing αhelices. In addition, since tract elongation provides additional interactions, the helicity of the polyQ tract directly correlates with its length. These findings suggest a plausible rationale for the association between polyQ tract length and AR transcriptional activity and have implications for establishing the mechanistic basis of SBMA.Polyglutamine (polyQ) tracts are lowcomplexity regions that are composed almost exclusively of Gln residues. They are frequent in the human proteome, particularly in the intrinsically disordered domains of proteins involved in the regulation of transcription, such as the activation domains of transcription factors 1 . The biological function of polyQ tracts is not wellunderstood, but it has been suggested that they regulate the activity of the proteins that harbor them by modulating the stability of the complexes that they form 2 . The lengths of polyQ tracts are variable because their coding DNA sequences tend to adopt secondary structures that hamper replication and repair 3 . Contractions and expansions in polyQ tracts can have functional consequences, and the lengths of the tracts may have been subject to natural selection 4 . As an example, it has been proposed that the length of the polyQ tract present in the protein huntingtin correlates with the intellectual coefficient 5 , presumably because it plays important although still not welldefined roles in neural plasticity 6 .For nine specific proteins, the variability in the lengths of polyQ tracts has pathogenic implications. Expansions beyond given thresholds are associated with nine rare hereditary neurodegenerative diseases known as polyQ diseases 7 . The mechanistic basis of this phenomenon is a matter of debate. Some authors have proposed that the expanded transcripts themselves are the neurotoxic species 8 due to their propensity to phase separate 9 , while others have suggested that expanded polyQ proteins are inherently neurotoxic 10 . However, it is widely believed that polyQ expansions cause neurotoxicity because they decrease protein solubility, which in turn leads to the formation of...

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A Liquid to Solid Phase Transition Underlying Pathological Huntingtin Exon1 Aggregation

Cited by 275 publications

References 81 publications

Fast fluorescence lifetime imaging reveals the aggregation processes of α-synuclein and polyglutamine in aging Caenorhabditis elegans

Fast fluorescence lifetime imaging reveals the aggregation processes of α-synuclein and polyglutamine in aging Caenorhabditis elegans

Poor old pores—The challenge of making and maintaining nuclear pore complexes in aging

Side chain to main chain hydrogen bonds stabilize a polyglutamine helix in the activation domain of a transcription factor

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