Heat shock protein 70 purification and characterization from Cyprinion macrastomus macrastomus and Garra rufa obtusa

Heat preadaptation improved the ability of Zygosaccharomyces rouxii to salt stress: a combined physiological and transcriptomic analysis

Zygosaccharomyces rouxii plays important roles in the brewing process of fermented foods such as soy sauce, where salt stress is a frequently encountered condition. In this study, effect of heat preadaptation on salt tolerance of Z. rouxii and the protective mechanisms underlying heat preadaptation were investigated based on physiological and transcriptomic analyses. Results showed that cells subjected to heat preadaptation (37 °C, 90 min) prior to salt stress aroused many physiological responses, including maintaining cell surface smooth and intracellular pH level, increasing Na⁺/K⁺-ATPase activity. Cells subjected to heat preadaptation increased the amounts of unsaturated fatty acids (palmitoleic C16:1, oleic C18:1, linoleic C18:2) and decreased the amounts of saturated fatty acids (palmitic C16:0, stearic C18:0) which caused the unsaturation degree (unsaturated/saturated = U/S ratio) increased by 2.4 times when compared with cells without preadaptation under salt stress. Besides, salt stress led to increase in contents of 5 amino acids (valine, proline, threonine, glycine, and tyrosine) and decrease of 2 amino acids (serine and lysine). When comparing the cells pre-exposed to heat preadaptation followed by challenged with salt stress and the cells without preadaptation under salt stress, the serine, threonine, and lysine contents increased significantly. RNA sequencing revealed that the metabolic level of glycolysis by Z. rouxii was weakened, while the metabolic levels of the pentose phosphate pathway and the riboflavin were enhanced in cells during heat preadaptation. Results presented in this study may contribute to understand the bases of adaptive responses in Z. rouxii and rationalize its exploitation in industrial processes.Key points• Heat preadaptation can improve high salinity tolerance of Z. rouxii.• Combined physiological and transcriptomic analyses of heat preadaptation mechanisms.• Provide theoretical support for the application of Z. rouxii.

Isolation and characterization of Heat Shock Protein 100-Batu1 from Toxoplasma gondii RH strain

Toxoplasma gondii is an intracellular parasitic protozoon which infects human and most warm-blooded animals. Almost one-third of the world's population is affected by life-threatening infection of T. gondii tachyzoites form. Slow growing, transmissible and encysted bradyzoites forms are composed after tachyzoites stage. Cellular and environmental stresses induce conversion of tachyzoites from bradyzoites and this condition is associated with Heat Shock Protein (Hsps) family. Hsp100 is a member of this protein family, and coordinates to disassemble protein aggregates with Hsp70 and Hsp40 in an ATP dependent manner. Several proteins are involved during this stage differentiation and Hsp100 may help them to be in their native soluble form to perform their function as observed in other organisms. For this purpose, Hsp100-Batu1 was isolated from T. gondii RH strain to characterize its biochemical properties in this current study. Hsp100 proteins play a role in survival and virulence of pathogens as shown in the literature. Therefore, manipulation of protein-protein interaction may perturb T. gondii infection and impair conversion to tachyzoites by inhibiting Hsp100 function. Therefore, results of this work present a potential route for vaccination or immunotherapy.

Natural thermal adaptation increases heat shock protein levels and decreases oxidative stress

Heat shock proteins (HSPs), originally identified as heat-inducible gene products, are a family of highly conserved proteins that respond to a wide variety of stress including oxidative stress. Although both acute and chronic oxidative stress have been well demonstrated to induce HSP responses, little evidence is available whether increased HSP levels provide enhanced protection against oxidative stress under elevated yet sublethal temperatures. We studied relationships between oxidative stress and HSPs in a physiological model by using Garra rufa (doctor fish), a fish species naturally acclimatized to different thermal conditions. We compared fish naturally living in a hot spring with relatively high water temperature (34.4±0.6°C) to those living in normal river water temperature (25.4±4.7°C), and found that levels of all the studied HSPs (HSP70, HSP60, HSP90, HSC70 and GRP75) were higher in fish living in elevated water temperature compared with normal river water temperature. In contrast, indicators of oxidative stress, including protein carbonyls and lipid hydroperoxides, were decreased in fish living in the elevated temperature, indicating that HSP levels are inversely associated with oxidative stress. The present results provide evidence that physiologically increased HSP levels provide protection against oxidative stress and enhance cytoprotection.

Hsp70 from Cyprinion macrostomus macrostomus and Garra rufa obtuse: stability and stability-dependent activity

Two fish species, Cyprinion macrostomus macrostomus and Garra rufa obtuse, tolerate adverse conditions in the Kangal hot springs and cope with multiple stressors such as food deprivation, extreme temperature, toxins, protein degradation, hypoxia, and microbial damage. These fish have evolved strategies to counteract the stressors including the induction of heat shock proteins (Hsps). Hsps play an essential role in maintaining cellular homeostasis, and one of the key proteins in the mechanism is Hsp70. Hsp70 itself is exposed to the same stressors as all other proteins, and, hence, the stability of Hsp70 was investigated. For this purpose, Hsp70 ATPase activity was determined at different urea concentrations. It was found that the protein maintains considerable ATP hydrolysis activity at higher denaturant conditions. Temperature effects on the substrate peptide binding showed that Hsp70s bind prominently at elevated temperatures. Furthermore, temperature effects on Hsp70 aggregation indicated that the presence of nucleotides decreases the aggregation process. The present work has determined the stability and activity of cmHsp70 and grHsp70 themselves under extreme conditions. The stability of the Hsp70 proteins maintains substrate proteins in the native state, which may aid in the adaptation of the fish species to the hot spring environment.