scholarly journals Exploring Novel Functions of the Small GTPase Ypt1p under Heat-Shock by Characterizing a Temperature-Sensitive Mutant Yeast Strain, ypt1-G80D

2019 ◽  
Vol 20 (1) ◽  
pp. 132 ◽  
Author(s):  
Chang Ho Kang ◽  
Joung Hun Park ◽  
Eun Seon Lee ◽  
Seol Ki Paeng ◽  
Ho Byoung Chae ◽  
...  

In our previous study, we found that Ypt1p, a Rab family small GTPase protein, exhibits a stress-driven structural and functional switch from a GTPase to a molecular chaperone, and mediates thermo tolerance in Saccharomyces cerevisiae. In the current study, we focused on the temperature-sensitive ypt1-G80D mutant, and found that the mutant cells are highly sensitive to heat-shock, due to a deficiency in the chaperone function of Ypt1pG80D. This defect results from an inability of the protein to form high molecular weight polymers, even though it retains almost normal GTPase function. The heat-stress sensitivity of ypt1-G80D cells was partially recovered by treatment with 4-phenylbutyric acid, a chemical chaperone. These findings indicate that loss of the chaperone function of Ypt1pG80D underlies the heat sensitivity of ypt1-G80D cells. We also compared the proteomes of YPT1 (wild-type) and ypt1-G80D cells to investigate Ypt1p-controlled proteins under heat-stress conditions. Our findings suggest that Ypt1p controls an abundance of proteins involved in metabolism, protein synthesis, cellular energy generation, stress response, and DNA regulation. Finally, we suggest that Ypt1p essentially regulates fundamental cellular processes under heat-stress conditions by acting as a molecular chaperone.

Author(s):  
Huili Zhang ◽  
Jianwei He ◽  
Yanyan Ji ◽  
Akio Kato ◽  
Youtao Song

AbstractWe cultured calnexin-disrupted and wild-type Saccharomyces cerevisiae strains under conditions of heat stress. The growth rate of the calnexin-disrupted yeast was almost the same as that of the wild-type yeast under those conditions. However, the induced mRNA level of the molecular chaperone PDI in the ER was clearly higher in calnexin-disrupted S. cerevisiae relative to the wild type at 37°C, despite being almost the same in the two strains under normal conditions. The western blotting analysis for PDI protein expression in the ER yielded results that show a parallel in their mRNA levels in the two strains. We suggest that PDI may interact with calnexin under heat stress conditions, and that the induction of PDI in the ER can recover part of the function of calnexin in calnexin-disrupted yeast, and result in the same growth rate as in wild-type yeast.


2013 ◽  
Vol 430 (4) ◽  
pp. 1259-1264 ◽  
Author(s):  
Masafumi Sakono ◽  
Arata Utsumi ◽  
Tamotsu Zako ◽  
Tetsuya Abe ◽  
Masafumi Yohda ◽  
...  

2021 ◽  
Author(s):  
Minsoo Kim ◽  
John D Swenson ◽  
Fionn McLoughlin ◽  
Elizabeth Vierling

Background: Heat Shock Protein 101 (HSP101) in plants and orthologs in bacteria (Caseinolytic peptidase B, ClpB) and yeast (Hsp104) are essential for thermotolerance. To investigate molecular mechanisms of thermotolerance involving HSP101, we performed a suppressor screen in Arabidopsis thaliana of a semi-dominant, missense HSP101 allele, hot1-4 (A499T). Plants carrying the hot1-4 mutation are more heat-sensitive than an HSP101 null mutant (hot1-3), indicating the toxicity of hot1-4 allele. Results: We report that one suppressor (shot2, suppressor of hot1-4 2) has a temperature-sensitive, missense mutation (E170K) in the CstF77 (Cleavage stimulation factor 77) subunit of the polyadenylation complex, which is critical for 3' end maturation of pre-mRNA. RNA-Seq analysis of total RNA depleted of ribosomes reveals that heat treatment causes transcriptional readthrough events in shot2, specifically in highly heat-induced genes, including the toxic hot1-4 gene. In addition, failure of correct transcript processing leads to reduced accumulation of many HSP RNAs and proteins, suppressing heat sensitivity of the hot1-4 mutant, due to reduction of the toxic mutant HSP101 protein. Notably, the shot2 mutation makes plants more sensitive to heat stress in the HSP101 null (hot1-3) and wild-type backgrounds correlated with the reduced expression of other heat-inducible genes required for thermotolerance. Conclusions: Our study reveals the critical function of CstF77 for 3' end formation of mRNA during heat stress, as well as the dominant role of HSP101 in dictating the outcome of severe heat stress in plants.


2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Linan Xu ◽  
Nitika ◽  
Naushaba Hasin ◽  
Daragh D. Cuskelly ◽  
Donald Wolfgeher ◽  
...  

Abstract Hsp70 is a highly conserved molecular chaperone critical for the folding of new and denatured proteins. While traditional models state that cells respond to stress by upregulating inducible HSPs, this response is relatively slow and is limited by transcriptional and translational machinery. Recent studies have identified a number of post-translational modifications (PTMs) on Hsp70 that act to fine-tune its function. We utilized mass spectrometry to determine whether yeast Hsp70 (Ssa1) is differentially modified upon heat shock. We uncovered four lysine residues on Ssa1, K86, K185, K354 and K562 that are deacetylated in response to heat shock. Mutation of these sites cause a substantial remodeling of the Hsp70 interaction network of co-chaperone partners and client proteins while preserving essential chaperone function. Acetylation/deacetylation at these residues alter expression of other heat-shock induced chaperones as well as directly influencing Hsf1 activity. Taken together our data suggest that cells may have the ability to respond to heat stress quickly though Hsp70 deacetylation, followed by a slower, more traditional transcriptional response.


Animals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 2407
Author(s):  
Abdelrazeq M. Shehata ◽  
Islam M. Saadeldin ◽  
Hammed A. Tukur ◽  
Walid S. Habashy

Heat stress is one of the most challenging environmental stresses affecting domestic animal production, particularly commercial poultry, subsequently causing severe yearly economic losses. Heat stress, a major source of oxidative stress, stimulates mitochondrial oxidative stress and cell dysfunction, leading to cell damage and apoptosis. Cell survival under stress conditions needs urgent response mechanisms and the consequent effective reinitiation of cell functions following stress mitigation. Exposure of cells to heat-stress conditions induces molecules that are ready for mediating cell death and survival signals, and for supporting the cell’s tolerance and/or recovery from damage. Heat-shock proteins (HSPs) confer cell protection against heat stress via different mechanisms, including developing thermotolerance, modulating apoptotic and antiapoptotic signaling pathways, and regulating cellular redox conditions. These functions mainly depend on the capacity of HSPs to work as molecular chaperones and to inhibit the aggregation of non-native and misfolded proteins. This review sheds light on the key factors in heat-shock responses for protection against cell damage induced by heat stress in chicken.


2013 ◽  
Vol 61 (10) ◽  
pp. 2385-2391 ◽  
Author(s):  
Fang Gan ◽  
Fei Ren ◽  
Xingxiang Chen ◽  
Chenhui Lv ◽  
Cuiling Pan ◽  
...  

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