Ethanol shock and lysozyme aggregation

Nemzer, Louis R.; Flanders, Bret N.; Schmit, Jeremy D.; Chakrabarti, Amitabha; Sorensen, C. M.

doi:10.1039/c2sm27124a

Cited by 18 publications

(18 citation statements)

References 38 publications

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“…However, the role of ethanol in generating protein denaturation at physiological concentrations is uncertain (Navarro-Tapia et al, 2017). Although a certain degree of protein denaturation has been suggested at 15% of ethanol, or above (Nemzer et al, 2013), no protein denaturation has been described at 6% or 8% ethanol, at which we observed UPR activation (Navarro-Tapia et al, 2016, 2017. These data suggest that a different signal other than protein denaturation activates UPR response at these ethanol concentrations.…”

Section: Discussionmentioning

confidence: 55%

Membrane fluidification by ethanol stress activates unfolded protein response in yeasts

Navarro-Tapia

Querol

Pérez‐Torrado

2018

Microbial Biotechnology

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SummaryThe toxic effect of ethanol is one of the most important handicaps for many biotechnological applications of yeasts, such as bioethanol production. Elucidation of ethanol stress response will help to improve yeast performance in biotechnological processes. In the yeast Saccharomyces cerevisiae, ethanol stress has been recently described as an activator of the unfolded protein response (UPR), a conserved intracellular signalling pathway that regulates the transcription of ER homoeostasis‐related genes. However, the signal and activation mechanism has not yet been unravelled. Here, we studied UPR's activation after ethanol stress and observed the upregulation of the key target genes, like INO1, involved in lipid metabolism. We found that inositol content influenced UPR activation after ethanol stress and we observed significant changes in lipid composition, which correlate with a major membrane fluidity alteration by this amphipathic molecule. Then, we explored the hypothesis that membrane fluidity changes cause UPR activation upon ethanol stress by studying UPR response against fluidification or rigidification agents and by studying a mutant, erg2, with altered membrane fluidity. The results suggest that the membrane fluidification effects of ethanol and other agents are the signal for UPR activation, a mechanism that has been proposed in higher eukaryotes.

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Section: Discussionmentioning

confidence: 55%

Membrane fluidification by ethanol stress activates unfolded protein response in yeasts

Navarro-Tapia

Querol

Pérez‐Torrado

2018

Microbial Biotechnology

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“…Unless a certain degree of protein denaturation has been suggested in solutions with 15% of ethanol or above in vitro (Nemzer et al, 2013 ), no protein denaturation has been described at 6 or 8% ethanol in vivo , at which we observed UPR activation after 1 h (Navarro-Tapia et al, 2016 ). In fact, glycolytic enzymes like alcohol dehydrogenase, phosphoglucoisomerase, triose phosphate isomerase or phosphoglycerate mutase, which are the most abundant in the cell, have shown no signs of denaturation, not even in in solutions with 20% ethanol (Millar et al, 1982 ).…”

Section: Discussionmentioning

confidence: 79%

Ethanol Effects Involve Non-canonical Unfolded Protein Response Activation in Yeast Cells

2017

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The unfolded protein response (UPR) is a conserved intracellular signaling pathway that controls transcription of endoplasmic reticulum (ER) homeostasis related genes. Ethanol stress has been recently described as an activator of the UPR response in yeast Saccharomyces cerevisiae, but very little is known about the causes of this activation. Although some authors ensure that the UPR is triggered by the unfolded proteins generated by ethanol in the cell, there are studies which demonstrate that protein denaturation occurs at higher ethanol concentrations than those used to trigger the UPR. Here, we studied UPR after ethanol stress by three different approaches and we concluded that unfolded proteins do not accumulate in the ER under. We also ruled out inositol depletion as an alternative mechanism to activate the UPR under ethanol stress discarding that ethanol effects on the cell decreased inositol levels by different methods. All these data suggest that ethanol, at relatively low concentrations, does not cause unfolded proteins in the yeasts and UPR activation is likely due to other unknown mechanism related with a restructuring of ER membrane due to the effect of ethanol.

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“…28,44,45 At the ethanol molar fraction used in this experiment, the immediate aggregation of lysozyme at room temperature due to an "ethanol shock" does not occur. This shock effect was recently discussed by Nemzer and coworkers, 25 whose experiments led to the production of nonfibrous spherical clusters with a stochastic process that depends on pH and ethanol concentration. The experimental conditions selected in the present work (x EtOD = 0.15 and pH = 3.0) determined that the aggregation occurred at about 50°C, the produced aggregates were stable in a wide temperature range, and the study of fibrils formation was completely assessed in vitro.…”

Section: ■ Results and Discussionmentioning

confidence: 93%

Spectroscopic and Microscopic Studies of Aggregation and Fibrillation of Lysozyme in Water/Ethanol Solutions

et al. 2015

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The thermal aggregation of lysozyme has been analyzed in water/ethanol solutions at low pH to induce the specific protein aggregation pathway which leads to fibrillar structures in a few hours. In this solvating medium, the protein undergoes a conformational rearrangement promoting the formation of fibrils that are structurally similar to amyloid ones. As the process evolves with different steps, a multitechnique approach has been used by means of analytical probes that can be selectively sensitive in the detection of the different stages of protein association. Fourier transform infrared spectroscopy, intrinsic fluorescence, stationary fluorescence anisotropy, transmission electron microscopy (TEM), and atomic force microscopy (AFM) measurements have been carried out at different times to access and characterize the whole aggregation pathway. The data recorded with different experimental setups revealed different sensitivity to different stages of protein assembling. The whole set of data together with the direct visualization of different aggregate structures by use of TEM and AFM imaging enable to discuss a possible mechanism of fibrillation.

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Ethanol shock and lysozyme aggregation

Cited by 18 publications

References 38 publications

Membrane fluidification by ethanol stress activates unfolded protein response in yeasts

Membrane fluidification by ethanol stress activates unfolded protein response in yeasts

Ethanol Effects Involve Non-canonical Unfolded Protein Response Activation in Yeast Cells

Spectroscopic and Microscopic Studies of Aggregation and Fibrillation of Lysozyme in Water/Ethanol Solutions

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