Cellular factors important for the de novo formation of yeast prions

2008 ◽  
Vol 36 (5) ◽  
pp. 1083-1087 ◽  
Author(s):  
Mick Tuite ◽  
Klement Stojanovski ◽  
Frederique Ness ◽  
Gloria Merritt ◽  
Nadejda Koloteva-Levine
Keyword(s):  
De Novo ◽  
Prion Diseases ◽  
Underlying Mechanism ◽  
Structural Form ◽  
Yeast Saccharomyces Cerevisiae ◽  
Yeast Prions ◽  
Cellular Factors ◽  
Jakob Disease ◽  
Protein Rich ◽  
Cis And Trans

Prions represent an unusual structural form of a protein that is ‘infectious’. In mammals, prions are associated with fatal neurodegenerative diseases such as CJD (Creutzfeldt–Jakob disease), while in fungi they act as novel epigenetic regulators of phenotype. Even though most of the human prion diseases arise spontaneously, we still know remarkably little about how infectious prions form de novo. The [PSI+] prion of the yeast Saccharomyces cerevisiae provides a highly tractable model in which to explore the underlying mechanism of de novo prion formation, in particular identifying key cis- and trans-acting factors. Most significantly, the de novo formation of [PSI+] requires the presence of a second prion called [PIN+], which is typically the prion form of Rnq1p, a protein rich in glutamine and aspartic acid residues. The molecular mechanism by which the [PIN+] prion facilitates de novo [PSI+] formation is not fully established, but most probably involves some form of cross-seeding. A number of other cellular factors, in particular chaperones of the Hsp70 (heat-shock protein 70) family, are known to modify the frequency of de novo prion formation in yeast.

Molecular biology and genetics of prion diseases

1994 ◽  
Vol 343 (1306) ◽  
pp. 447-463 ◽  
Keyword(s):  
Nucleic Acid ◽  
De Novo ◽  
Prion Diseases ◽  
Spongiform Encephalopathy ◽  
Species Barrier ◽  
Prolonged Incubation ◽  
Brain Extracts ◽  
Jakob Disease ◽  
Spongiform Degeneration ◽  
The Difference

Scrapie was thought for m any years to be caused by a virus. Enriching fractions from Syrian hamster (SHa) brain for scrapie infectivity led to the discovery of the prion protein (PrP). To date, no scrapie-specific nucleic acid has been found. As well as scrapie, prion diseases include bovine spongiform encephalopathy (BSE) of cattle, as well as Creutzfeldt-Jakob disease (CJD) and Gerstmann-Sträussler-Scheinker syndrome (GSS) of humans. Transgenic (Tg) mice expressing both SHa and mouse (Mo) PrP genes were used to probe the molecular basis of the species barrier and the mechanism of scrapie prion replication. The prion inoculum was found to dictate which prions are synthesized de novo , even though the cells express both PrP genes. Discovery of mutations in the PrP genes of humans with GSS and familial CJD established that prion diseases are both genetic and infectious. Tg mice expressing MoPrP with the GSS point mutation spontaneously develop neurologic dysfunction, spongiform degeneration and astrocytic gliosis. Inoculation of brain extracts prepared from these Tg(MoPrP-P101L) mice produced neurodegeneration in many of the recipient animals after prolonged incubation times. These and other results suggest that prions are devoid of foreign nucleic acid and are thus different from viruses and viroids. Studies on the structure of PrP Sc and PrP c suggest that the difference is conformational. Whether one or more putative a-helices in PrP c are converted into (β-sheets during synthesis of PrP Sc is unknown. Distinct prion isolates or ‘strains’ exhibit different patterns of PrP Sc accumulation which are independent of incubation times. Whether variations in PrP Sc conformation are responsible for prion diversity remains to be established. Prion studies have given new insights into the etiologies of infectious, sporadic and inherited degenerative diseases.

scholarly journals The Prion-Like Spreading of Alpha-Synuclein in Parkinson’s Disease: Update on Models and Hypotheses

2021 ◽  
Vol 22 (15) ◽  
pp. 8338
Author(s):  
Asad Jan ◽  
Nádia Pereira Gonçalves ◽  
Christian Bjerggaard Vaegter ◽  
Poul Henning Jensen ◽  
Nelson Ferreira
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Molecular Mechanisms ◽  
De Novo ◽  
Alpha Synuclein ◽  
Experimental Models ◽  
Cellular Factors ◽  
Recent Developments ◽  
Novel Targets ◽  
Presynaptic Protein

The pathological aggregation of the presynaptic protein α-synuclein (α-syn) and propagation through synaptically coupled neuroanatomical tracts is increasingly thought to underlie the pathophysiological progression of Parkinson’s disease (PD) and related synucleinopathies. Although the precise molecular mechanisms responsible for the spreading of pathological α-syn accumulation in the CNS are not fully understood, growing evidence suggests that de novo α-syn misfolding and/or neuronal internalization of aggregated α-syn facilitates conformational templating of endogenous α-syn monomers in a mechanism reminiscent of prions. A refined understanding of the biochemical and cellular factors mediating the pathological neuron-to-neuron propagation of misfolded α-syn will potentially elucidate the etiology of PD and unravel novel targets for therapeutic intervention. Here, we discuss recent developments on the hypothesis regarding trans-synaptic propagation of α-syn pathology in the context of neuronal vulnerability and highlight the potential utility of novel experimental models of synucleinopathies.

scholarly journals Extracellular Vesicles-Encapsulated Yeast Prions and What They Can Tell Us about the Physical Nature of Propagons

2020 ◽  
Vol 22 (1) ◽  
pp. 90
Author(s):  
Mehdi Kabani
Keyword(s):  
Protein Quality ◽  
Fluorescent Protein ◽  
Physical Nature ◽  
Dependent Manner ◽  
Yeast Saccharomyces Cerevisiae ◽  
Yeast Prions ◽  
Daughter Cells ◽  
Cytoplasmic Proteins ◽  
Green Fluorescent ◽  
Functionally Diverse

The yeast Saccharomyces cerevisiae hosts an ensemble of protein-based heritable traits, most of which result from the conversion of structurally and functionally diverse cytoplasmic proteins into prion forms. Among these, [PSI+], [URE3] and [PIN+] are the most well-documented prions and arise from the assembly of Sup35p, Ure2p and Rnq1p, respectively, into insoluble fibrillar assemblies. Yeast prions propagate by molecular chaperone-mediated fragmentation of these aggregates, which generates small self-templating seeds, or propagons. The exact molecular nature of propagons and how they are faithfully transmitted from mother to daughter cells despite spatial protein quality control are not fully understood. In [PSI+] cells, Sup35p forms detergent-resistant assemblies detectable on agarose gels under semi-denaturant conditions and cytosolic fluorescent puncta when the protein is fused to green fluorescent protein (GFP); yet, these macroscopic manifestations of [PSI+] do not fully correlate with the infectivity measured during growth by the mean of protein infection assays. We also discovered that significant amounts of infectious Sup35p particles are exported via extracellular (EV) and periplasmic (PV) vesicles in a growth phase and glucose-dependent manner. In the present review, I discuss how these vesicles may be a source of actual propagons and a suitable vehicle for their transmission to the bud.

Prionopathies and Prionlike Protein Aberrations in Neurodegenerative Diseases

Neurographics ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 127-148
Author(s):  
K.N. Anderson ◽  
W.B. Overcast ◽  
J.R. Brosch ◽  
B.D. Graner ◽  
M.C. Veronesi
Keyword(s):  
Neurodegenerative Diseases ◽  
Protein Misfolding ◽  
Clinical Presentation ◽  
Prion Diseases ◽  
Imaging Biomarkers ◽  
Amyloid Pet ◽  
Imaging Features ◽  
Jakob Disease ◽  
The Common ◽  
Neuro Imaging

Protein misfolding has been an area of intense research and is implicated in a number of neurodegenerative diseases. Key proteins in the brain lose their native ability to fold and instead assume abnormal conformations. Misfolded proteins cluster to form pathologic aggregates, which cause cellular dysfunction, neuronal death, and neurodegeneration. The prionopathies are best known among the neurodegenerative diseases for their ability to misfold, self-propagate, and infect other organisms. There is increasing evidence of a rationale for a prionlike mechanism of spread of other neurodegenerative diseases through a similar seeding mechanism. In this review, we detail the role of a key protein aberration known to the various prion diseases, including sporadic, variant, and iatrogenic Creutzfeldt-Jakob disease; variably protease-sensitive prionopathy; Gerstmann-Straussler-Scheinker disease; fatal familial insomnia; and kuru. We also discuss the clinical presentation, the available, and emerging imaging options for these diseases. In the second part of this review, we delineate how a prionlike seeding process may be driving the progression of other neurodegenerative diseases, including Parkinson disease, Alzheimer disease, and Huntington disease. A discussion of clinical presentation and imaging features of these example diseases follows to make a case for a common approach to developing imaging biomarkers and therapies of these diseases.Learning Objective: Upon completion of this article, one should be able to describe the various types of prion diseases, recognize and identify the common the neuro-imaging findings in prion diseases, describe seeding mechanism of prion disease, list the common amyloid PET tracers used for Alzheimer’s disease, and list common imaging biomarkers in neurodegenerative diseases.

scholarly journals Prion Disease Blood Test Using Immunoprecipitation and Improved Quaking-Induced Conversion

mBio ◽  
2011 ◽  
Vol 2 (3) ◽  
Author(s):  
Christina D. Orrú ◽  
Jason M. Wilham ◽  
Lynne D. Raymond ◽  
Franziska Kuhn ◽  
Björn Schroeder ◽  
...  
Keyword(s):  
Real Time ◽  
Blood Test ◽  
Prion Diseases ◽  
Proteinase K ◽  
Transmissible Spongiform Encephalopathies ◽  
Serum Samples ◽  
Spongiform Encephalopathies ◽  
Jakob Disease

ABSTRACT A key challenge in managing transmissible spongiform encephalopathies (TSEs) or prion diseases in medicine, agriculture, and wildlife biology is the development of practical tests for prions that are at or below infectious levels. Of particular interest are tests capable of detecting prions in blood components such as plasma, but blood typically has extremely low prion concentrations and contains inhibitors of the most sensitive prion tests. One of the latter tests is quaking-induced conversion (QuIC), which can be as sensitive as in vivo bioassays, but much more rapid, higher throughput, and less expensive. Now we have integrated antibody 15B3-based immunoprecipitation with QuIC reactions to increase sensitivity and isolate prions from inhibitors such as those in plasma samples. Coupling of immunoprecipitation and an improved real-time QuIC reaction dramatically enhanced detection of variant Creutzfeldt-Jakob disease (vCJD) brain tissue diluted into human plasma. Dilutions of 1014-fold, containing ~2 attogram (ag) per ml of proteinase K-resistant prion protein, were readily detected, indicating ~10,000-fold greater sensitivity for vCJD brain than has previously been reported. We also discriminated between plasma and serum samples from scrapie-infected and uninfected hamsters, even in early preclinical stages. This combined assay, which we call “enhanced QuIC” (eQuIC), markedly improves prospects for routine detection of low levels of prions in tissues, fluids, or environmental samples. IMPORTANCE Transmissible spongiform encephalopathies (TSEs) are largely untreatable and are difficult to diagnose definitively prior to irreversible clinical decline or death. The transmissibility of TSEs within and between species highlights the need for practical tests for even the smallest amounts of infectivity. A few sufficiently sensitive in vitro methods have been reported, but most have major limitations that would preclude their use in routine diagnostic or screening applications. Our new assay improves the outlook for such critical applications. We focused initially on blood plasma because a practical blood test for prions would be especially valuable for TSE diagnostics and risk reduction. Variant Creutzfeldt-Jakob disease (vCJD) in particular has been transmitted between humans via blood transfusions. Enhanced real-time quaking-induced conversion (eRTQ) provides by far the most sensitive detection of vCJD to date. The 15B3 antibody binds prions of multiple species, suggesting that our assay may be useful for clinical and fundamental studies of a variety of TSEs of humans and animals.

scholarly journals PO-193 Exercise training decreased lipid accumulation in murine skeletal muscle through Sestrin2-mediated SHIP2-JNK signaling pathway

2018 ◽  
Vol 1 (4) ◽  
Author(s):  
Tianyi Wang ◽  
Song Huang ◽  
Xiao Han ◽  
Sujuan Liu ◽  
Yanmei Niu ◽  
...  
Keyword(s):  
Insulin Resistance ◽  
Skeletal Muscle ◽  
Fatty Acid ◽  
Lipid Metabolism ◽  
Exercise Training ◽  
High Fat Diet ◽  
De Novo ◽  
Underlying Mechanism ◽  
Wild Type ◽  
High Fat

Objective Obesity is becoming increasingly prevalent and is an important contributor to the worldwide burden of diseases. It is widely accepted that exercise training is beneficial for the prevention and treatment of obesity. However, the underlying mechanism by which exercise training improving skeletal muscle lipid metabolism is still not fully described. Sestrins (Sestrin1-3) are highly conserved stress-inducible protein. Concomitant ablation of Sestrin2 and Sestrin3 has been reported to provoke hepatic mTORC1/S6K1 activation and insulin resistance even without nutritional overload and obesity, implicating that Sestrin2 and Sestrin3 have an important homeostatic function in the control of mammalian glucose and lipid metabolism. Our previous results demonstrated that physical exercise increased Sestrin2 expression in murine skeletal muscle, while the role of Sestrin2 in regulating lipid metabolism remains unknown.  SH2 domain containing inositol 5-phosphatase (SHIP2) acts as a negative regulator of the insulin signaling both in vitro and in vivo. An increased expression of SHIP2 inhibits the insulin-induced Akt activation, glucose uptake, and glycogen synthesis in 3T3-L1 adipocytes, L6 myotubes and tissues of animal models. Alterations of SHIP2 expression and/or enzymatic function appear to have a profound impact on the development of insulin resistance. However, the regulatory function of SHIP2 in lipid metabolism after exercise remains unclear. It has been reported that SHIP2 modulated lipid metabolism through regulating the activity of c-Jun N-terminal kinase (JNK) and Sterol regulatory element-binding protein-1 (SREBP-1). JNK is a subclass of mitogen-activated protein kinase (MAPK) signaling pathway in mammalian cells and plays a crucial role in metabolic changes and inflammation associated with a high-fat diet. Inhibition of JNK reduces lipid deposition and proteins level of fatty acid de novo synthesis in liver cells. It has been reported that Sestrin2 regulated the phosphorylation of JNK, however the underlying mechanism remains unclear. SREBP-1 is important in regulating cholesterol biosynthesis and uptake and fatty acid biosynthesis, and SREBP-1 expression produces two different isoforms, SREBP-1a and SREBP-1c. SREBP-1c is responsible for regulating the genes required for de novo lipogenesis and its expression is regulated by insulin. SREBP-1a regulates genes related to lipid and cholesterol production and its activity is regulated by sterol levels in the cell. Altogether, the purpose of this study was to explore the effect and underlying mechanism of Sestrin2 on lipid accumulation after exercise training. Methods Male wild type and SESN2−/− mice were divided into normal chow (NC) and high-fat diet (HFD) groups to create insulin resistance mice model. After 8 weeks the IR model group was then divided into HFD sedentary control and HFD exercise groups (HE). Mice in HE group underwent 6-week treadmill exercise to reveal the effect of exercise training on lipid metabolism in insulin resistance model induced by HFD. We explored the mechanism through which Sestrin2 regulated lipid metabolism in vitro by supplying palmitate, overexpressing or inhibiting SESNs, SHIP2 and JNK in myotubes. Results We found that 6-week exercise training decreased body weight, BMI and fat mass in wild type and SESN2-/- mice after high-fat diet (HFD) feeding. And exercise training decreased the level of plasma glucose, serum insulin, triglycerides and free fatty acids in wild type but not in Sestrin2-/- mice. Lipid droplet in skeletal muscle was also decreased in wild type but did not in Sestrin2-/- mice. Moreover, exercise training increased the proteins expression involved in fatty acid oxidation and decreased the proteins which related to fatty acid de novo synthesis. The results of oil red staining and the change of proteins related to fatty acid de novo synthesis and beta oxidation in myotubes treated with palmitate, Ad-SESN2 and siRNA-Sestrin2 were consisted with the results in vivo, which suggested that Sestrin2 was a key regulator in lipid metabolism. Exercise training increased Sestrin2 expression and reversed up-regulation of SHIP2 and pJNK induced by HFD in wild type mice but not in Sestrin2-/- mice. In parallel, overexpression of Sestrin2 decreased the level of SHIP2 and pJNK induced by palmitate while Sestrin2 knock down by siRNA-Sestrin2 treatment did not change the expression of SHIP2 and pJNK, which suggested that Sestrin2 modulated SHIP2 and JNK in the state of abnormal lipid metabolism. Inhibition of SHIP2 reduced the activity of JNK, increased lipid accumulation and the proteins of fatty acid synthesis after palmitate treatment and over expression of Sestrin2, which suggest that Sestrin2 modulated lipid metabolism through SHIP2/JNK pathway. Conclusions Sestrin2 plays an important role in improving lipid metabolism after exercise training, and Sestrin2 regulates lipid metabolism by SHIP2-JNK pathway in skeletal muscle.

scholarly journals Inherited variants in CHD3 demonstrate variable expressivity in Snijders Blok-Campeau syndrome

2021 ◽  
Author(s):  
Jet van der Spek ◽  
Joery den Hoed ◽  
Lot Snijders Blok ◽  
Alexander J. M. Dingemans ◽  
Dick Schijven ◽  
...  
Keyword(s):  
De Novo ◽  
Neurodevelopmental Disorder ◽  
Underlying Mechanism ◽  
Next Generation Sequencing Data ◽  
Sequencing Data ◽  
Human Phenotype ◽  
Variable Expressivity ◽  
Pathogenic Variants ◽  
Reduced Penetrance ◽  
Coding Variants

Interpretation of next-generation sequencing data of individuals with an apparent sporadic neurodevelopmental disorder (NDD) often focusses on pathogenic variants in genes associated with NDD, assuming full clinical penetrance with limited variable expressivity. Consequently, inherited variants in genes associated with dominant disorders may be overlooked when the transmitting parent is clinically unaffected. While de novo variants explain a substantial proportion of cases with NDDs, a significant number remains undiagnosed possibly explained by coding variants associated with reduced penetrance and variable expressivity. We characterized twenty families with inherited heterozygous missense or protein-truncating variants (PTVs) in CHD3, a gene in which de novo variants cause Snijders Blok-Campeau syndrome, characterized by intellectual disability, speech delay and recognizable facial features (SNIBCPS). Notably, the majority of the inherited CHD3 variants were maternally transmitted. Computational facial and human phenotype ontology-based comparisons demonstrated that the phenotypic features of probands with inherited CHD3 variants overlap with the phenotype previously associated with de novo variants in the gene, while carrier parents are mildly or not affected, suggesting variable expressivity. Additionally, similarly reduced expression levels of CHD3 protein in cells of an affected proband and of related healthy carriers with a CHD3 PTV, suggested that compensation of expression from the wildtype allele is unlikely to be an underlying mechanism. Our results point to a significant role of inherited variation in SNIBCPS, a finding that is critical for correct variant interpretation and genetic counseling and warrants further investigation towards understanding the broader contributions of such variation to the landscape of human disease.

scholarly journals Overexpression of quality control proteins reduces prion conversion in prion-infected cells

2018 ◽  
Vol 293 (41) ◽  
pp. 16069-16082 ◽  
Author(s):  
Simrika Thapa ◽  
Basant Abdulrahman ◽  
Dalia H. Abdelaziz ◽  
Li Lu ◽  
Manel Ben Aissa ◽  
...  
Keyword(s):  
Quality Control ◽  
De Novo ◽  
Prion Diseases ◽  
Neuroblastoma Cells ◽  
Cellular Prion Protein ◽  
Control Mechanisms ◽  
Cellular Mechanisms ◽  
Prion Propagation ◽  
Infected Cells

Prion diseases are fatal infectious neurodegenerative disorders in humans and other animals and are caused by misfolding of the cellular prion protein (PrPC) into the pathological isoform PrPSc. These diseases have the potential to transmit within or between species, including zoonotic transmission to humans. Elucidating the molecular and cellular mechanisms underlying prion propagation and transmission is therefore critical for developing molecular strategies for disease intervention. We have shown previously that impaired quality control mechanisms directly influence prion propagation. In this study, we manipulated cellular quality control pathways in vitro by stably and transiently overexpressing selected quality control folding (ERp57) and cargo (VIP36) proteins and investigated the effects of this overexpression on prion propagation. We found that ERp57 or VIP36 overexpression in persistently prion-infected neuroblastoma cells significantly reduces the amount of PrPSc in immunoblots and prion-seeding activity in the real-time quaking-induced conversion (RT-QuIC) assay. Using different cell lines infected with various prion strains confirmed that this effect is not cell type– or prion strain–specific. Moreover, de novo prion infection revealed that the overexpression significantly reduced newly formed PrPSc in acutely infected cells. ERp57-overexpressing cells significantly overcame endoplasmic reticulum stress, as revealed by expression of lower levels of the stress markers BiP and CHOP, accompanied by a decrease in PrP aggregates. Furthermore, application of ERp57-expressing lentiviruses prolonged the survival of prion-infected mice. Taken together, improved cellular quality control via ERp57 or VIP36 overexpression impairs prion propagation and could be utilized as a potential therapeutic strategy.

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