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- Chen, Xin, 1980, et al.
(författare)
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Amyloid-beta peptide-induced cytotoxicity and mitochondrial dysfunction in yeast
- 2015
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Ingår i: FEMS Yeast Research. - : Oxford University Press (OUP). - 1567-1356 .- 1567-1364. ; 15:6
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Tidskriftsartikel (refereegranskat)abstract
- Alzheimer's disease (AD) is the most common neurodegenerative disease, characterized by deposits of amyloid-beta(A beta) peptides. However, the underlying molecular mechanisms of neuron cell dysfunction and cell death in AD still remain poorly understood. Yeast Saccharomyces cerevisiae shares many conserved biological processes with all eukaryotic cells, including human neurons. Thanks to relatively simple and quick genetic and environmental manipulations, the large knowledge base and data collections, this organism has become a valuable tool to unravel fundamental intracellular mechanisms underlying neurodegeneration. In this study, we have used yeast as a model system to study the effects of intracellular A beta peptides and we found that cells constitutively producing native A beta directed to the secretory pathway exhibited a lower growth rate, lower biomass yield, lower respiratory rate, increased oxidative stress, hallmarks of mitochondrial dysfunction and ubiquitin-proteasome system dysfunction. These findings are relevant for better understanding the role of A beta in cell stress and cell damage.
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| 3. |
- Chen, Xin, 1980, et al.
(författare)
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Interplay of Energetics and ER Stress Exacerbates Alzheimer's Amyloid-beta (A beta) Toxicity in Yeast
- 2017
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Ingår i: Frontiers in Molecular Neuroscience. - : Frontiers Media SA. - 1662-5099. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Alzheimer's disease (AD) is a progressive neurodegeneration. Oligomers of amyloid-beta peptides (A beta) are thought to play a pivotal role in AD pathogenesis, yet the mechanisms involved remain unclear. Two major isoforms of A beta associated with AD are A beta 40 and A beta 42, the latter being more toxic and prone to form oligomers. Here, we took a systems biology approach to study two humanized yeast AD models which expressed either A beta 40 or A beta 42 in bioreactor cultures. Strict control of oxygen availability and culture pH, strongly affected chronological lifespan and reduced variations during cell growth. Reduced growth rates and biomass yields were observed upon A beta 42 expression, indicating a redirection of energy from growth to maintenance. Quantitative physiology analyses furthermore revealed reduced mitochondria' functionality and ATP generation in A beta 42 expressing cells, which matched with observed aberrant mitochondria' structures. Genome-wide expression level analysis showed that A beta 42 expression triggered strong ER stress and unfolded protein responses. Equivalent expression of A beta 40, however, induced only mild ER stress, which resulted in hardly affected physiology. Using AD yeast models in well controlled cultures strengthened our understanding on how cells translate different A beta toxicity signals into particular cell fate programs, and further enhance their potential as a discovery platform to identify possible therapies.
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| 4. |
- Chen, Xin, 1980, et al.
(författare)
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Role of frameshift ubiquitin B protein in Alzheimer's disease
- 2016
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Ingår i: Wiley Interdisciplinary Reviews: Systems Biology and Medicine. - : Wiley. - 1939-5094 .- 1939-005X. ; 8:4, s. 300-313
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Forskningsöversikt (refereegranskat)abstract
- Alzheimer's disease (AD) is the most common neurodegenerative disease and is characterized by accumulation of misfolded and aggregated proteins. Since the ubiquitin-proteasome system (UPS) is the major intracellular protein quality control (PQC) system in eukaryotic cells, it is likely involved in the etiology of AD. The frameshift form of ubiquitin (Ubb+1) accumulates in the neuritic plaques and neurofibrillary tangles in patients with AD. Ubb+1 accumulates in an age-dependent manner as a result of RNA-polymerase mediated molecular misreading during transcription, which allows the formation of mutant proteins in the absence of gene mutations. The accumulation of the Ubb+1 protein may act as an endogenous reporter for proteasome dysfunction and a growing number of studies have shown that Ubb+1 may play more important pathogenic roles in AD etiology than previously hypothesized. The yeast Saccharomyces cerevisiae shares many conserved biological processes with all eukaryotic cells, including human neurons. This organism has been regarded as a model system for investigating the fundamental intracellular mechanisms, including those underlying neurodegeneration. We propose here that yeast systems biology approaches, combined with cell and molecular biology approaches will increase the relevant knowledge needed for advancement and elucidation of mechanisms and complex traits, which could provide new targets for therapeutic intervention in AD. WIREs Syst Biol Med 2016, 8:300–313. doi: 10.1002/wsbm.1340. For further resources related to this article, please visit the WIREs website.
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| 5. |
- Johansson, Magnus, 1983, et al.
(författare)
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PUFA-induced cell death is mediated by Yca1p-dependent and -independent pathways, and is reduced by vitamin C in yeast
- 2016
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Ingår i: FEMS Yeast Research. - : Oxford University Press (OUP). - 1567-1356 .- 1567-1364. ; 16:2
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Tidskriftsartikel (refereegranskat)abstract
- Polyunsaturated fatty acids (PUFA) such as linoleic acid (LA, n-6, C18:2) and gamma-linolenic acid (GLA, n-6, C18: 3) are essential and must be obtained from the diet. There has been a growing interest in establishing a bio-sustainable production of PUFA in several microorganisms, e.g. in yeast Saccharomyces cerevisiae. However, PUFAs can also be toxic to cells because of their susceptibility to peroxidation. Here we investigated the negative effects of LA and GLA production on S. cerevisiae by characterizing a strain expressing active Delta 6 and Delta 12 desaturases from the fungus Mucor rouxii. Previously, we showed that the PUFA-producing strain has low viability, down-regulated genes for oxidative stress response, and decreased proteasome activity. Here we show that the PUFA strain accumulates high levels of reactive oxygen species (ROS) and lipid peroxides, and accumulates damaged proteins. The PUFA strain also showed great increase in metacaspase Yca1p activity, suggesting cells could die by caspase-mediated cell death. When treated with antioxidant vitamin C, ROS, lipid peroxidation and protein carbonylation were greatly reduced, and the activity of the metacaspase was significantly decreased too, ultimately doubling the lifespan of the PUFA strain. When deleting YCA1, the caspase-like activity and the oxidative stress decreased and although the lifespan was slightly prolonged, the phenotype could not be fully reversed, pointing that Yca1p was not the main executor of cell death.
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| 6. |
- Muñoz Arellano, Ana Joyce, 1983, et al.
(författare)
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Different expression levels of human mutant ubiquitin B+1 (UBB+1) can modify chronological lifespan or stress resistance of saccharomyces cerevisiae
- 2018
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Ingår i: Frontiers in Molecular Neuroscience. - : Frontiers Media SA. - 1662-5099. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- The ubiquitin-proteasome system (UPS) is the main pathway responsible for the degradation of misfolded proteins, and its dysregulation has been implicated in several neurodegenerative diseases, including Alzheimer’s disease (AD). UBB+1, a mutant variant of ubiquitin B, was found to accumulate in neurons of AD patients and it has been linked to UPS dysfunction and neuronal death. Using the yeast Saccharomyces cerevisiae as a model system, we constitutively expressed UBB+1to evaluate its effects on proteasome function and cell death, particularly under conditions of chronological aging. We showed that the expression of UBB+1caused inhibition of the three proteasomal proteolytic activities (caspase-like (β1), trypsin-like (β2) and chymotrypsin-like (β5) activities) in yeast. Interestingly, this inhibition did not alter cell viability of growing cells. Moreover, we showed that cells expressing UBB+1at lower level displayed an increased capacity to degrade induced misfolded proteins. When we evaluated cells during chronological aging, UBB+1expression at lower level, prevented cells to accumulate reactive oxygen species (ROS) and avert apoptosis, dramatically increasing yeast life span. Since proteasome inhibition by UBB+1has previously been shown to induce chaperone expression and thus protect against stress, we evaluated our UBB+1model under heat shock and oxidative stress. Higher expression of UBB+1caused thermotolerance in yeast due to induction of chaperones, which occurred to a lesser extent at lower expression level of UBB+1(where we observed the phenotype of extended life span). Altering UPS capacity by differential expression of UBB+1protects cells against several stresses during chronological aging. This system can be valuable to study the effects of UBB+1on misfolded proteins involved in neurodegeneration and aging.
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| 7. |
- Souza-Moreira, Tatiana M., et al.
(författare)
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Screening of 2A peptides for polycistronic gene expression in yeast
- 2018
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Ingår i: FEMS Yeast Research. - : Oxford University Press (OUP). - 1567-1356 .- 1567-1364. ; 18:5
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Tidskriftsartikel (refereegranskat)abstract
- A complexity of pathway expression in yeast compared to prokaryotes is the need for separate promoters and terminators for each gene expressed. Single transcript expression and separated protein production is possible via the use of 2A viral peptides, but detailed characterization to assess their suitability and applications is needed. The present work aimed to characterize multiple 2A peptide sequences to determine suitability for metabolic engineering applications in Saccharomyces cerevisiae. We screened 22 peptides placed between fluorescent protein sequences. Cleaving efficiency was calculated by western blot intensity of bands corresponding to the cleaved and uncleaved forms of the reporter. Three out of the 22 sequences showed high cleavage efficiency: 2A peptide from Equine rhinitis B virus (91%), Porcine teschovirus-1 (85%) and Operophtera brumata cypovirus-18 (83%). Furthermore, expression of the released protein was comparable to its monocistronic expression. As a proof-of-concept, the triterpene friedelin was successfully produced in the same yeast strain by expressing its synthase with the truncated form of HMG1 linked by the 2A peptide of ERBV-1, with production titers comparable to monocistronic expression (via separate promoters). These results suggest that these peptides could be suitable for expression and translation of multiple proteins in metabolic engineering applications in S. cerevisiae.
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