The fine-tuning of gene expression is critical for all cellular processes; aberrations in this activity can lead to pathology, and conversely, resilience. As their role in coordinating organismal ...responses to both internal and external factors have increasingly come into focus, small non-coding RNAs have emerged as an essential component to disease etiology. Using Systemic RNA interference Defective (SID) mutants of the nematode Caenorhabditis elegans, deficient in gene silencing, we examined the potential consequences of dysfunctional epigenomic regulation in the context of Parkinson's disease (PD). Specifically, the loss of either the sid-1 or sid-3 genes, which encode a dsRNA transporter and an endocytic regulatory non-receptor tyrosine kinase, respectively, conferred neuroprotection to dopaminergic (DA) neurons in an established transgenic C. elegans strain wherein overexpression of human α-synuclein (α-syn) from a chromosomally integrated multicopy transgene causes neurodegeneration. We further show that knockout of a specific microRNA, mir-2, attenuates α-syn neurotoxicity; suggesting that the native targets of mir-2-dependent gene silencing represent putative neuroprotective modulators. In support of this, we demonstrated that RNAi knockdown of multiple mir-2 targets enhanced α-syn-induced DA neurodegeneration. Moreover, we demonstrate that mir-2 overexpression originating in the intestine can induce neurodegeneration of DA neurons, an effect that was reversed by pharmacological inhibition of SID-3 activity. Interestingly, sid-1 mutants retained mir-2-induced enhancement of neurodegeneration. Transcriptomic analysis of α-syn animals with and without a sid-1 mutation revealed 27 differentially expressed genes with human orthologs related to a variety of diseases, including PD. Among these was pgp-8, encoding a P-glycoprotein-related ABC transporter. Notably, sid-1; pgp-8 double mutants abolished the neurodegeneration resulting from intestinal mir-2 overexpression. This research positions known regulators of small RNA-dependent gene silencing within a framework that facilitates mechanistic evaluation of epigenetic responses to exogenous and endogenous factors influencing DA neurodegeneration, revealing a path toward new targets for therapeutic intervention of PD.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Based on current CERN infrastructure, an electron–proton collider is proposed at a centre-of-mass energy of about 9 TeV. A 7 TeV LHC bunch is used as the proton driver to create a plasma wakefield ...which then accelerates electrons to 3 TeV, these then colliding with the other 7 TeV LHC proton beam. Although of very high energy, the collider has a modest projected integrated luminosity of 10–100 pb
-
1
. For such a collider, with a centre-of-mass energy 30 times greater than HERA, parton momentum fractions,
x
, down to about
10
-
8
are accessible for photon virtualities,
Q
2
, of 1 GeV
2
. The energy dependence of hadronic cross sections at high energies, such as the total photon–proton cross section, which has synergy with cosmic-ray physics, can be measured and QCD and the structure of matter better understood in a region where the effects are completely unknown. Searches at high
Q
2
for physics beyond the Standard Model will be possible, in particular the significantly increased sensitivity to the production of leptoquarks. These and other physics highlights of a very high energy electron–proton collider are outlined.
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Calcineurin (CN) is a highly conserved Ca ²⁺–calmodulin (CaM)-dependent phosphatase that senses Ca ²⁺ concentrations and transduces that information into cellular responses. Ca ²⁺ homeostasis is ...disrupted by α-synuclein (α-syn), a small lipid binding protein whose misfolding and accumulation is a pathological hallmark of several neurodegenerative diseases. We report that α-syn, from yeast to neurons, leads to sustained highly elevated levels of cytoplasmic Ca ²⁺, thereby activating a CaM-CN cascade that engages substrates that result in toxicity. Surprisingly, complete inhibition of CN also results in toxicity. Limiting the availability of CaM shifts CN's spectrum of substrates toward protective pathways. Modulating CN or CN's substrates with highly selective genetic and pharmacological tools (FK506) does the same. FK506 crosses the blood brain barrier, is well tolerated in humans, and is active in neurons and glia. Thus, a tunable response to CN, which has been conserved for a billion years, can be targeted to rebalance the phosphatase’s activities from toxic toward beneficial substrates. These findings have immediate therapeutic implications for synucleinopathies.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
α-Synuclein (α-syn), a protein of unknown function, is the most abundant protein in Lewy bodies, the histological hallmark of Parkinson's disease (PD). In yeast α-syn inhibits endoplasmic reticulum ...(ER)-to-Golgi (ERrightward arrowGolgi) vesicle trafficking, which is rescued by overexpression of a Rab GTPase that regulates ERrightward arrowGolgi trafficking. The homologous Rab1 rescues α-syn toxicity in dopaminergic neuronal models of PD. Here we investigate this conserved feature of α-syn pathobiology. In a cell-free system with purified transport factors α-syn inhibited ERrightward arrowGolgi trafficking in an α-syn dose-dependent manner. Vesicles budded efficiently from the ER, but their docking or fusion to Golgi membranes was inhibited. Thus, the in vivo trafficking problem is due to a direct effect of α-syn on the transport machinery. By ultrastructural analysis the earliest in vivo defect was an accumulation of morphologically undocked vesicles, starting near the plasma membrane and growing into massive intracellular vesicular clusters in a dose-dependent manner. By immunofluorescence/immunoelectron microscopy, these clusters were associated both with α-syn and with diverse vesicle markers, suggesting that α-syn can impair multiple trafficking steps. Other Rabs did not ameliorate α-syn toxicity in yeast, but RAB3A, which is highly expressed in neurons and localized to presynaptic termini, and RAB8A, which is localized to post-Golgi vesicles, suppressed toxicity in neuronal models of PD. Thus, α-syn causes general defects in vesicle trafficking, to which dopaminergic neurons are especially sensitive.
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Due to environmental insult or innate genetic deficiency, protein folding environments of the mitochondrial matrix are prone to dysregulation, prompting the activation of a specific organellar ...stress-response mechanism, the mitochondrial unfolded protein response (UPR
). In
, mitochondrial damage leads to nuclear translocation of the ATFS-1 transcription factor to activate the UPR
After short-term acute stress has been mitigated, the UPR
is eventually suppressed to restore homeostasis to
hermaphrodites. In contrast, and reflective of the more chronic nature of progressive neurodegenerative disorders such as Parkinson's disease (PD), here, we report the consequences of prolonged, cell-autonomous activation of the UPR
in
dopaminergic neurons. We reveal that neuronal function and integrity decline rapidly with age, culminating in activity-dependent, non-apoptotic cell death. In a PD-like context wherein transgenic nematodes express the Lewy body constituent protein α-synuclein (αS), we not only find that this protein and its PD-associated disease variants have the capacity to induce the UPR
, but also that coexpression of αS and ATFS-1-associated dysregulation of the UPR
synergistically potentiate dopaminergic neurotoxicity. This genetic interaction is in parallel to mitophagic pathways dependent on the
homolog, which is necessary for cellular resistance to chronic malfunction of the UPR
Given the increasingly recognized role of mitochondrial quality control in neurodegenerative diseases, these studies illustrate, for the first time, an insidious aspect of mitochondrial signaling in which the UPR
pathway, under disease-associated, context-specific dysregulation, exacerbates disruption of dopaminergic neurons
, resulting in the neurodegeneration characteristic of PD.
Disruptions or alterations in the activation of pathways that regulate mitochondrial quality control have been linked to neurodegenerative diseases due in part to the central role of mitochondria in metabolism, ROS regulation, and proteostasis. The extent to which these pathways, including the mitochondrial unfolded protein response (UPR
) and mitophagy, are active may predict severity and progression of these disorders, as well as sensitivity to compounding stressors. Furthermore, therapeutic strategies that aim to induce these pathways may benefit from increased study into cellular responses that arise from long-term or ectopic stimulation, especially in neuronal compartments. By demonstrating the detrimental consequences of prolonged cellular activation of the UPR
, we provide evidence that this pathway is not a universally beneficial mechanism because dysregulation has neurotoxic consequences.
Genomic multiplication of the locus-encoding human α-synuclein (α-syn), a polypeptide with a propensity toward intracellular misfolding, results in Parkinson's disease (PD). Here we report the ...results from systematic screening of nearly 900 candidate genetic targets, prioritized by bioinformatic associations to existing PD genes and pathways, via RNAi knockdown. Depletion of 20 gene products reproducibly enhanced misfolding of α-syn over the course of aging in the nematode Caenorhabditis elegans. Subsequent functional analysis of seven positive targets revealed five previously unreported gene products that significantly protect against age- and dose-dependent α-syn-induced degeneration in the dopamine neurons of transgenic worms. These include two trafficking proteins, a conserved cellular scaffold-type protein that modulates G protein signaling, a protein of unknown function, and one gene reported to cause neurodegeneration in knockout mice. These data represent putative genetic susceptibility loci and potential therapeutic targets for PD, a movement disorder affecting ≈2% of the population over 65 years of age.
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Parkinson's Disease (PD) is the second-most common neurodegenerative disease in the world, yet the fundamental and underlying causes of the disease are largely unknown, and treatments remain sparse ...and impotent. Several biological systems have been employed to model the disease but the nematode roundworm
shows unique promise among these to disinter the elusive factors that may prevent, halt, and/or reverse PD phenotypes. Some of the most salient of these
models of PD are those that position the misfolding-prone protein alpha-synuclein (α-syn), a hallmark pathological component of PD, as the primary target for scientific interrogation. By transgenic expression of human α-syn in different tissues, including dopamine neurons and muscle cells, the primary cellular phenotypes of PD in humans have been recapitulated in these
models and have already uncovered multifarious genetic factors and chemical compounds that attenuate dopaminergic neurodegeneration. This review describes the paramount discoveries obtained through the application of different α-syn models of PD in
and highlights their established utility and respective promise to successfully uncover new conserved genetic modifiers, functional mechanisms, therapeutic targets and molecular leads for PD with the potential to translate to humans.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Parkinson's disease (PD) is defined by the loss of dopaminergic neurons in the substantia nigra and the formation of Lewy body inclusions containing aggregated α-synuclein. Efforts to explain ...dopamine neuron vulnerability are hindered by the lack of dopaminergic cell death in α-synuclein transgenic mice. To address this, we manipulated both dopamine levels and α-synuclein expression. Nigrally targeted expression of mutant tyrosine hydroxylase with enhanced catalytic activity increased dopamine levels without damaging neurons in non-transgenic mice. In contrast, raising dopamine levels in mice expressing human A53T mutant α-synuclein induced progressive nigrostriatal degeneration and reduced locomotion. Dopamine elevation in A53T mice increased levels of potentially toxic α-synuclein oligomers, resulting in conformationally and functionally modified species. Moreover, in genetically tractable Caenorhabditis elegans models, expression of α-synuclein mutated at the site of interaction with dopamine prevented dopamine-induced toxicity. These data suggest that a unique mechanism links two cardinal features of PD: dopaminergic cell death and α-synuclein aggregation.
Parkinson's disease (PD), the second most prevalent neurodegenerative disorder, is characterized by the degeneration of dopamine (DA) neurons and age-dependent formation of protein inclusions that ...contain the α-synuclein (α-syn) protein. RNA interference (RNAi) screening using Caenorhabditis elegans identified RTCB-1, an uncharacterized gene product, as one of several significant modifiers of α-syn protein misfolding. RTCB-1 is the worm ortholog of the human HSPC117 protein, a component of RNA trafficking granules in mammalian neurons. Here we show that RTCB-1 protects C. elegans DA neurons from age-dependent degeneration induced by human α-syn. Moreover, neuronal-specific RNAi depletion of rtcb-1 enhanced α-syn-induced degeneration. Similar results were obtained when worms were exposed to the DA neurotoxin 6-hydroxydopamine. HSPC117 has been characterized recently as an essential subunit of the human tRNA splicing ligase complex. tRNA ligases have alternative functions in RNA repair and nonconventional mRNA splicing events. For example, in yeast, unconventional splicing of HAC1, a transcription factor that controls the unfolded protein response (UPR), is mediated by a tRNA ligase. In C. elegans, we demonstrate that RTCB-1 is necessary for xbp-1 (worm homolog of HAC1) mRNA splicing. Moreover, using a RNA ligase-dead mutant, we determine that the ligase activity of worm RTCB-1 is required for its neuroprotective role, which, in turn, is mediated through XBP-1 in the UPR pathway. Collectively, these studies highlight the mechanistic intersection of RNA processing and proteostasis in mediating neuroprotection.
On the 15th Anniversary of Disease Models & Mechanisms as a trailblazing venue for the dissemination of discoveries pertaining to human health involving model systems, we celebrate the journey of ...this journal, as mirrored through the evolution of research using the nematode roundworm, Caenorhabditis elegans. Driven by the exponential growth of genomic data, worms have advanced from a basic research tool to precise and elegant models for disease and have yielded substantive insights into numerous human disorders. A harbinger of functional genomic analysis since the inception of RNA interference screening, the directed application of C. elegans for identification of disease-modifying factors has revealed new pathways and therapeutic targets to accelerate translational outcomes. Together with advances in gene editing, worm models are now ushering in the era of precision medicine with characteristic expedience.
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