Small heat shock proteins and adaptation of various Drosophila species to hyperthermia

The dynamics and the level of accumulation of small heat shock proteins (sHSP group 21–27) after a heat exposure were studied in three Drosophila species differing in thermotolerance. The southern species Drosophila virilis, having the highest thermotolerance, surpassed thermosensitive D. lummei and D. melanogaster in the level of sHSPs throughout the temperature range tested. The results suggest an important role of sHSPs in the molecular mechanisms of adaptation to adverse environmental conditions, particularly to hyperthermia.     

Temperature Sensitivity of Bacteriolysis Induced by β-Lactam Antibiotics in Amino Acid-Deprived Escherichia coli

The temperature-sensitive penicillin tolerance response previously reported in amino acid-deprived Escherichia coli (W. Kusser and E. E. Ishiguro, J. Bacteriol. 169:2310–2312, 1987) was not due to the induction of the heat shock response resulting from a temperature upshift and was therefore unrelated to the findings of another report (J. K. Powell and K. D. Young, J. Bacteriol. 173:4021–4026, 1991) indicating a positive correlation between the expression of heat shock proteins and penicillin tolerance. The thermosensitive event occurred in the lysis induction stage.     

Biotechnical applications of small heat shock proteins from bacteria

The stress responses of most bacteria are thought to involve the upregulation of small heat shock proteins. We describe here some of the most pertinent aspects of small heat shock proteins, to highlight their potential for use in various applications. Bacterial species have between one and 13 genes encoding small heat shock proteins, the precise number depending on the species considered. Major efforts have recently been made to characterize the protein protection and membrane stabilization mechanisms involving small heat shock proteins in bacteria. These proteins seem to be involved in the acquisition of cellular heat tolerance. They could therefore potentially be used to maintain cell viability under unfavorable conditions, such as heat shock or chemical treatments. This review highlights the potential roles of applications of small heat shock proteins in stabilizing overproduced heterologous proteins in Escherichia coli, purified bacterial small heat shock proteins in protein biochip technology, proteomic analysis and food technology and the potential impact of these proteins on some diseases. This article is part of a Directed Issue entitled: Small HSPs in physiology and pathology.     

Analysis of the heat-shock response displayed by two Chaetomium species originating from different thermal environments.

Three features of the heat shock response, reorganization of protein expression, intracellular accumulation of trehalose, and alteration in unsaturation degree of fatty acids were investigated in the thermophilic fungus Chaetomium thermophile and compared to the response displayed by a closely related mesophilic species, C. brasiliense. Thermophilic heat shock response paralleled the mesophilic response in many respects like (i) the temperature difference observed between normothermia and the upper limit of translational activity, (ii) the transient nature of the heat shock response at the level of protein expression including both the induction of heat shock proteins (HSPs) as well as the repression of housekeeping proteins, (iii) the presence of representatives of high-molecular-weight HSPs families, (iv) intracellular accumulation of trehalose, and finally (v) modifications in fatty acid composition. On the other hand, a great variability between the two organisms was observed for the proteins expressed during stress, in particular a protein of the HSP60 family that was only observed in C. thermophile. This peptide was also present constitutively at normal temperature and may thus fulfil thermophilic functions. It is shown that accumulation of trehalose does not play a part in thermophily but is only a stress response. C. thermophile contains less polyunsaturated fatty acids at normal temperature than C. brasiliense, a fact that can be directly related to thermophily. When subjected to heat stress, both organisms tended to accumulate shorter and less unsaturated fatty acids.     

Biosynthetic cause of in vivo acquired thermotolerance of photosynthetic light reactions and metabolic responses of chloroplasts to heat stress

Thermotolerance of photosynthetic light reactions in vivo is correlated with a decrease in the ratio of monogalactosyl diacylglycerol to digalactosyl diacylglycerol and an increased incorporation into thylakoid membranes of saturated digalactosyl diacylglycerol species. Although electron transport remains virtually intact in thermotolerant chloroplasts, thylakoid protein phosphorylation is strongly inhibited. The opposite is shown for thermosensitive chloroplasts in vivo. Heat stress causes reversible and irreversible inactivation of chloroplast protein synthesis in heat-adapted and nonadapted plants, respectively, but doe not greatly affect formation of rapidly turned-over 32 kilodalton proteins of photosystem II. The formation on cytoplasmic ribosomes and import by chloroplasts of thylakoid and stroma proteins remain preserved, although decreased in rate, at supraoptimal temperatures. Thermotolerant chloroplasts accumulate heat shock proteins in the stroma among which 22 kilodalton polypeptides predominate. We suggest that interactions of heat shock proteins with the outer chloroplast envelope membrane might enhance formation of digalactosyl diacylglycerol species. Furthermore, a heat-induced recompartmentalization of the chloroplast matrix that ensures effective transport of ATP from thylakoid membranes towards those sites inside the chloroplast and the cytoplasm where photosynthetically indispensable components and heat shock proteins are being formed is proposed as a metabolic strategy of plant cells to survive and recover from heat stress.     

Analysis of the Heat-Shock Response Displayed by Two Chaetomium Species Originating from Different Thermal Environments

Three features of the heat shock response, reorganization of protein expression, intracellular accumulation of trehalose, and alteration in unsaturation degree of fatty acids were investigated in the thermophilic fungus Chaetomium thermophile and compared to the response displayed by a closely related mesophilic species, C. brasiliense. Thermophilic heat shock response paralleled the mesophilic response in many respects like (i) the temperature difference observed between normothermia and the upper limit of translational activity, (ii) the transient nature of the heat shock response at the level of protein expression including both the induction of heat shock proteins (HSPs) as well as the repression of housekeeping proteins, (iii) the presence of representatives of high-molecular-weight HSPs families, (iv) intracellular accumulation of trehalose, and finally (v) modifications in fatty acid composition. On the other hand, a great variability between the two organisms was observed for the proteins expressed during stress, in particular a protein of the HSP60 family that was only observed in C. thermophile. This peptide was also present constitutively at normal temperature and may thus fulfil thermophilic functions. It is shown that accumulation of trehalose does not play a part in thermophily but is only a stress response. C. thermophile contains less polyunsaturated fatty acids at normal temperature than C. brasiliense, a fact that can be directly related to thermophily. When subjected to heat stress, both organisms tended to accumulate shorter and less unsaturated fatty acids.     

Molecular mechanisms underlying thermal adaptation of xeric animals

For many years, we and our collaborators have investigated the adaptive role of heat shock proteins in different animals, including the representatives of homothermic and poikilothermic species that inhabit regions with contrasting thermal conditions. Adaptive evolution of the response to hyperthermia has led to different results depending upon the species. The thermal threshold of induction of heat shock proteins in desert thermophylic species is, as a rule, higher than in the species from less extreme climates. In addition, thermoresistant poikilothermic species often exhibit a certain level of heat shock proteins in cells even at a physiologically normal temperature. Furthermore, there is often a positive correlation between the characteristic temperature of the ecological niche of a given species and the amount of Hsp70-like proteins in the cells at normal temperature. Although in most cases adaptation to hyperthermia occurs without changes in the number of heat shock genes, these genes can be amplified in some xeric species. It was shown that mobile genetic elements may play an important role in the evolution and fine-tuning of the heat shock response system, and can be used for direct introduction of mutations in the promoter regions of these genes.     

Synaptic thermoprotection in a desert‐dwelling Drosophila species

Synaptic transmission is a critical mechanism for transferring information from the nervous system to the body. Environmental stress, such as extreme temperature, can disrupt synaptic transmission and result in death. Previous work on larval Drosophila has shown that prior heat‐shock exposure protects synaptic transmission against failure during subsequent thermal stress. This induced thermoprotection has been ascribed to an up‐regulation of the inducible heat‐shock protein, Hsp70. However, the mechanisms mediating natural thermoprotection in the wild are unknown. We compared synaptic thermosensitivity between D. melanogaster and a desert species, D. arizonae. Synaptic thermosensitivity and the functional limits of the related locomotor behavior differed significantly between closely related, albeit ecologically distinct species. Locomotory behavior of wandering third instar D. arizonae larvae was less thermosensitive and the upper temperature limit of locomotory function exceeded that of D. melanogaster by 6°C. Behavioral results corresponded with significantly lower synaptic thermosensitivity at the neuromuscular junction in D. arizonae. Prior heat‐shock protected only D. melanogaster by increasing relative excitatory junctional potential (EJP) duration, the time required for EJP failure at 40°C, and the incidence of EJP recovery following heat‐induced failure. Hsp70 induction profiles following heat‐shock demonstrate up‐regulation of inducible Hsp70 in D. melanogaster but not in D. arizonae. However, expression of Hsp70 under control conditions is greater in D. arizonae. These results suggest that the mechanisms of natural thermoprotection involve an increase in baseline Hsp70 expression. © 2005 Wiley Periodicals, Inc. J Neurobiol, 2005     

Evolution of the response to heat shock in genus Drosophila

Thermotolerance was studied in a wide spectrum of Drosophila species and strains originating from different climatic zones and considerably differing from one another in the ambient temperature of their habitats. The species that lived in hot climate have a higher thermotolerance. Most species of the virilis group exhibited positive correlation between the HSP70 accumulation after heat exposure and thermotolerance; however, this correlation was absent in some species and strains. For example, the D. melanogaster Oregon R strain, which had the highest sensitivity to heat shock (HS) among all strains and species studied, displayed the maximum level of HSP70 proteins after HS. The patterns of induction of various heat shock protein (HSP) families after heat exposure in a wide spectrum of Drosophila species were compared. The results obtained suggest that the HSP40 and low-molecular-weight HSPs (lmwHSPs) play a significant role in thermotolerance and adaptation to hot climate. Polymorphism in hsp70 gene clusters of Drosophila and variation in the numbers of gene copies and hsp70 isoforms in group virilis were found. The evolutionary role of the variation in the number of hsp70 gene copies observed in the strains and species of genus Drosophila is discussed.     

Heat shock proteins: functions and role in adaptation to hyperthermia

The results are generalized of many-year studies into the adaptive role of heat shock proteins in different animals, including the representatives of cold- and warm-blooded species that inhabit regions with different thermal conditions. Adaptive evolution of the response to hyperthermia can lead to different results depending on the species. The thermal threshold of induction of the heat shock proteins in desert thermophylic species is, as a rule, higher than in the moderate climate species. In addition, thermoresistant species are often characterized by a certain level of heat shock proteins in cells even at a physiologically normal temperature. Although adaptation to hyperthermia is achieved in most cases without changes in the number of heat shock genes, they can be amplified in some cases in termophylic species. The role of mobile elements in evolution of the heat shock genes was shown and approach was developed for directional introduction of mutations in the promoter regions of these genes.     

Heat shock and cold shock in Deinococcus radiodurans

On the basis of acquired thermotolerance and cryotolerance, the optimal heat shock and cold shock temperatures have been determined for Deinococcus radiodurans. A heat shock at 42°C maximized survival at the lethal temperature of 52°C and a cold shock at 20°C maximized survival after repeated freeze-thawing. Enhanced survival from heat shock was found to be strongly dependent on growth stage, with its greatest effect shortly after phase. Increased synthesis of a total of 67 proteins during heat shock and 42 proteins during cold shock were observed by two-dimensional polyacrylamide gel electrophoresis (2D PAGE) and autoradiography. Eight of the most highly induced heat shock proteins shown by 2D PAGE were identified by MALDI-MS as Hsp20, GroEL, DnaK, SodA, Csp, Protease I and two proteins of unknown function.     

Global whole-cell FTICR mass spectrometric proteomics analysis of the heat shock response in the radioresistant bacterium Deinococcus radiodurans

The results of previous studies indicated that D. radiodurans mounts a regulated protective response to heat shock, and that expression of more than 130 genes, including classical chaperones such as the groESL and dnaKJ operons and proteases such as clpB are induced in response to elevated temperature. In addition, previous qualitative whole-cell mass spectrometric studies conducted under heat shock conditions indicated global changes in the D. radiodurans proteome. To enable the discovery of novel heat shock inducible proteins as well as gain greater biological insight into the classical heat shock response at the protein level, we undertook the global whole-cell FTICR mass spectrometric proteomics study reported here. We have greatly increased the power of this approach by conducting a large number of replicate experiments in addition to taking a semiquantitative approach to data analysis, finding good reproducibility between replicates. Through this analysis, we have identified with high confidence a core set of classical heat shock proteins whose expression increases dramatically and reproducibly in response to elevated temperature. In addition, we have found that the heat shock proteome includes a large number of induced proteins that have not been identified previously as heat responsive, and have therefore been designated as candidate responders. Finally, our results are consistent with the hypothesis that elevated temperature stress could lead to cross-protection against other related stresses.     

Accumulation of a specific subset of D. melanogaster heat shock mRNAs in normal development without heat shock

During normal development in D. melanogaster, messenger RNAs for three of the seven heat shock proteins (hsp83, hsp28 and hsp26) accumulate in adult ovaries and are abundant in embryos until blastoderm. The three mRNAs appear to originate in nurse cells and subsequently pass, during stages 10-11, into the oocyte. Little if any of the four other heat shock mRNAs is present in unshocked ovaries or embryos at any time examined. Pre-blastoderm embryos fail to accumulate these heat shock mRNAs even if subjected to heat shock. The accumulation in normal oogenesis of mRNAs for only three of the seven heat shock proteins indicates the existence of differential, possibly multiple controls of heat shock gene expression, and suggests that heat shock proteins hsp83, hsp28 and hsp26 function in the oocyte or early embryo.     

Heat shock response in psychrophilic and psychrotrophic yeast from Antarctica

The response to heat stress in six yeast species isolated from Antarctica was examined. The yeast were classified into two groups: one psychrophilic, with a maximum growth temperature of 20°C, and the other psychrotrophic, capable of growth at temperatures above 20°C. In addition to species-specific heat shock protein (hsp) profiles, a heat shock (15°C–25°C for 3 h) induced the synthesis of a 110-kDa protein common to the psychrophiles, Mrakia stokesii, M. frigida, and M. gelida, but not evident in Leucosporidium antarcticum. Immunoblot analyses revealed heat shock inducible proteins (hsps) corresponding to hsps 70 and 90. Interestingly, no proteins corresponding to hsps 60 and 104 were observed in any of the psychrophilic species examined. In the psychrotrophic yeast, Leucosporidium fellii and L. scottii, in addition to the presence of hsps 70 and 90, a protein corresponding to hsp 104 was observed. In psychrotrophic yeast, as observed in psychrophilic yeast, the absence of a protein corresponding to hsp 60 was noted. Relatively high endogenous levels of trehalose which were elevated upon a heat shock were exhibited by all species. A 10 Celsius degree increase in temperature above the growth temperature (15°C) of psychrophiles and psychrotrophs was optimal for heat shock induced thermotolerance. On the other hand, in psychrotrophic yeast grown at 25°C, only a 5 Celsius degree increase in temperature was necessary for heat shock induced thermotolerance. Induced thermotolerance in all yeast species was coincident with hsp synthesis and trehalose accumulation. It was concluded that psychrophilic and psychrotrophic yeast, although exhibiting a stress response similar to mesophilic Saccharomyces cerevisiae, nevertheless had distinctive stress protein profiles. Received: August 7, 1997 / Accepted: October 22, 1997     

Is hsp70 the cellular thermometer?

Cells respond to an increase in temperature by inducing the synthesis of the heat shock proteins, which are a small set of evolutionarily conserved proteins. We review the evidence leading us to suggest that the free pool of one of these proteins, hsp70, serves as a cellular thermometer that regulates the expression of all heat shock proteins.     

Small heat shock proteins in Drosophila may confer thermal tolerance

The four small heat shock proteins in Drosophila melanogaster are genetically linked and simultaneously synthesized, both in response to high temperature and, developmentally, during puparium formation. In tissue culture cells their synthesis is inducible by the molting hormone, ecdysterone. We show here that accompanying their induction and accumulation, the cells and animals acquire thermal tolerance.     

Heat Shock Proteins: Functions and Role in Adaptation to Hyperthermia

The results are generalized of many-year studies into the adaptive role of heat shock proteins in different animals, including the representatives of cold- and warm-blooded species that inhabit regions with different thermal conditions. Adaptive evolution of the response to hyperthermia can lead to different results depending on the species. The thermal threshold of induction of the heat shock proteins in desert thermophylic species is, as a rule, higher than in the moderate climate species. In addition, thermoresistant species are often characterized by a certain level of heat shock proteins in cells even at a physiologically normal temperature. Although adaptation to hyperthermia is achieved in most cases without changes in the number of heat shock genes, they can be amplified in some cases in termophylic species. The role of mobile elements in evolution of the heat shock genes was shown and approach was developed for directional introduction of mutations in the promoter regions of these genes.__________Translated from Ontogenez, Vol. 36, No. 4, 2005, pp. 265–273.Original Russian Text Copyright © 2005 by Evgen’ev, Garbuz, Zatsepina.