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Heat shock response, heat shock transcription factor and cell aging.

A characteristic feature of aging is a progressive impairment in the ability to adapt to environmental challenges. The purpose of this article is to review the evidence of an attenuated response to heat and physiological stresses in a number of mammalian aging model systems, including the human diploid fibroblasts in culture, whole animals and animal-derived cells and cell cultures, as well as peripheral blood mononuclear cells obtained from human donors. Analyses of the regulation and function of heat shock factor 1 (HSF1), a transcription factor that mediates the response to heat shock, showed that while the relative abundance of both the hsf1 transcript and the HSF1 protein did not change as a function of age, the responsiveness of HSF1 to heat-induced activation, as measured by its trimerization and ability to bind to the heat shock element consensus sequence, was inversely related to the age of the cells used. Given the fundamentally important role of heat shock proteins (HSPs) in many aspects of protein homeostasis and signal transduction it seems likely that the inability, or compromised ability, of aging cells and organisms to activate HSF1 and produce HSPs in response to stress would contribute to the well-known increase in morbidity and mortality of the aged when challenged.

Aging↗

PubMed2005

Melanoma-associated antigen tyrosinase but not Melan-A/MART-1 expression and presentation dissociate during the heat shock response.

Heat shock has been shown to have pleiotropic effects on tumor physiology besides a direct cytotoxic effect. In the present study, we address the question whether heat shock treatment has an impact on the antigenicity of human melanoma cells and their specific recognition by cytotoxic lymphocytes. The heat shock response was induced by treating the cells with two different thermal isoeffect doses, which resulted in equivalent clonogenic survival, mimicking doses achieved during clinical hyperthermia treatment of tumors. Antigen expression and immune recognition by cytotoxic T cells was studied using the human melanoma cell lines 624.38-MEL, SK-MEL23, WM115 and WM266-4, which naturally express, process and present tyrosinase and Melan-A/melanoma antigen recognized by T cells (MART)-1-derived peptides in the context of HLA-A2 molecules. We demonstrate that during the heat shock response following the two thermal doses, heat shock protein 70 (Mr 72 kDa) (HSP70) was induced with differential kinetics; tyrosinase protein and mRNA levels dissociated with a significant increase in tyrosinase protein and a decrease in transcript levels. A similar dissociation was not observed for Melan-A/MART-1. Furthermore, tyrosinase-specific T-cell recognition did not correlate with changes in HSP70 and antigen protein levels. These results suggest that caution has to be taken when considering protein levels as a marker for the antigenic status of a tumor. Moreover, these results document the maintenance of immunological homeostasis during recovery from heat treatment, thus challenging the view that tumor cells subjected to heat shock become resistant to CTL recognition.

Antigen Presentation↗

PubMed1995

Aspirin enhances thermotolerance in human erythroleukemic cells: an effect associated with the modulation of the heat shock response.

Heat shock protein (HSP) synthesis is induced by hyperthermia and other types of stress in mammalian cells in vitro and in vivo. In the present report we describe that in human erythroleukemic cells, aspirin (400 microM), when administered during or immediately after a hyperthermic treatment, causes an increase in the amount of HSP70 synthesized and prolongs HSP70 synthesis for a period of several hours. This effect is not due to increased HSP70 mRNA stability. In the presence of aspirin, the heat shock transcription factor is maintained in the activated DNA-binding state for a period twice as long as control, an effect which results in enhanced and prolonged HSP70 mRNA transcription. A different cyclooxygenase inhibitor, indomethacin (10(-7) M), also provokes similar effects. The modulation of the heat shock response by aspirin and indomethacin is associated with the ability of these drugs to potentiate the effect of hyperthermia and prolong thermotolerance for a period of 48 h. These results indicate that the use of aspirin and indomethacin should be carefully monitored in cancer patients undergoing hyperthermic treatment. On the other hand, the ability of aspirin to enhance HSP70 synthesis suggests that nonsteroidal anti-inflammatory drugs could potentiate the cytoprotective role of HSPs in pathological states, including fever, inflammation, and ischemia.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed1993

A small influence of HSP90 levels on the trehalose and heat shock element inductions of the yeast heat shock response.

Heat shock protein (HSP) induction is only one change elicited in yeast by heat shock. Trehalose is also accumulated, while declining intracellular pH stimulates plasma membrane ATPase activity. Recently the trehalose induction was shown to be regulated by levels of HSP70 and, to a lesser extent, HSP104. Another HSP which might contribute to regulation is HSP90, especially as HSP90 forms complexes with heat shock transcription factor and several of the regulatory proteins of eukaryotic cells. This possibility was investigated using isogenic yeast strains with normal, decreased or elevated HSP90. The results show HSP90 levels having a small negative influence over the heat inductions of trehalose and the heat shock element, a minor effect compared with the major regulation exerted by HSP70.

Genotype↗

PubMed1994

Heat shock response and heat shock protein antigens of Vibrio cholerae.

Sixteen heat shock proteins (Hsps) have been identified in the hypertoxinogenic strain 569B of Vibrio cholerae which are synthesized in response to small and large elevations of temperature. The induction of the Hsps is necessary for the cells to survive the deleterious effects of heat. There is no difference in the pattern of induction of the Hsps in V. cholerae strains varying in levels of toxinogenicity. One of the major low-molecular-mass Hsps, a 16-kDa protein, is preferentially degraded following shift down of temperature. This protein is induced at a much lower level at high temperatures in cells maintained in the laboratory for a prolonged period. The only Hsp located in the outer membrane of V. cholerae cells is a 23-kDa protein. Western immunoblot analysis with human immune sera collected from convalescent cholera patients revealed that this protein is markedly immunogenic. The human immune serum also reacted with the 69- and 16-kDa major Hsps and the 88-, 66-, and 46-kDa Hsps but not with the 61-kDa major Hsp identified as the groEL gene product. All major Hsps reacted with rabbit anti-V. cholerae sera. Ethanol stress leads to the induction of four of the major Hsps and three additional proteins.

Adaptation, Biological↗

PubMed1994

Weak acid preservatives block the heat shock response and heat-shock-element-directed lacZ expression of low pH Saccharomyces cerevisiae cultures, an inhibitory action partially relieved by respiratory deficiency.

Inhibition of microbial growth by weak acid preservatives increases with medium acidification, since these agents enter cells in the undissociated state. Many of the effects of these acids are due to the cytoplasmic acidification they cause as they dissociate in the higher pH environment of the cytosol. Sorbic and benzoic acids, two widely used preservatives, were found to exert pronounced effects on the heat shock response and thermotolerance of Saccharomyces cerevisiae. These effects were strongly influenced by the pH of the culture medium. In low pH cultures sorbate inhibited the induction of thermotolerance by sublethal heat shock, causing strong induction of respiratory-deficient petites among the survivors of heat treatment. However, when the culture pH was above 5.5 sorbate acted as a powerful chemical inducer of thermotolerance in the absence of any sublethal heat treatment. Sorbate and benzoate also inhibited heat induction of the major heat shock proteins in low pH yeast cultures. This appears to result from lack of induction of the heat shock element (HSE) promoter sequence since sorbate prevented heat induction of a HSE-lacZ fusion at low pH. The uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP) and the plasma-membrane-ATPase inhibitor diethylstilboestrol were identified as additional inhibitors of heat induction of heat shock proteins. Numerous chemicals induce the heat shock response in the absence of heat stress, but sorbate, benzoate, CCCP and diethylstilboestrol are the first compounds shown to act as selective inhibitors of heat-induced protein expression in yeast. In the presence of sorbate concentrations which, at low pH, totally inhibit both the heat shock response and growth of cells competent in respiration, respiratory-deficient petites still retain a limited capacity for growth and for heat induction of heat shock proteins. This restoration of a response to heat shock in acidified sorbate-treated cultures of petites might contribute to their higher capacity for growth in the presence of sorbate.

Adaptation, Physiological↗

PubMed2003

Role of BRCA1 in heat shock response.

The heat shock response is an evolutionarily conserved response to heat and other stresses that promotes the maintenance of key metabolic functions and cell survival. We report that exposure of human prostate (DU-145) and breast (MCF-7) cancer cells to heat (42 degrees C) caused a rapid disappearance of the breast cancer susceptibility gene-1 (BRCA1) protein, starting at approximately 1 h after the onset of heating and slightly lagging behind the increase in heat shock protein 70 (HSP70) levels. The heat-induced loss of BRCA1 occurred at the protein level, since: (1) BRCA1 mRNA expression was unaffected; and (2) the BRCA1 protein loss was also observed in DU-145 cells that expressed exogenous wild-type BRCA1 (wtBRCA1). In addition to heat regulation of BRCA1 protein levels, we also found that BRCA1 could modulate the heat shock response. Thus, wtBRCA1 overexpressing DU-145 cell clones showed significantly decreased sensitivity to heat-induced cytotoxicity; and Brca1 mutant mouse embryo fibroblasts showed increased sensitivity to heat. The DU-145 wtBRCA1 clones also showed increased expression of the small heat shock protein HSP27; and reporter assays revealed that wtBRCA1 stimulated a two to four-fold increase in HSP27 promoter activity, consistent with its ability to upregulate HSP27 mRNA and protein levels. In studies using epitope-tagged truncated BRCA1 proteins, the ability to stimulate the HSP27 promoter and to mediate heat-induced degradation required the amino-terminus but not the carboxyl-terminus of BRCA1. Although the heat-induced loss of BRCA1 appeared to be due to protein degradation, various protein metabolic agents (or combinations) failed to block this event, including: MG132 (a 26S proteasomal inhibitor), N-acetyl-leucyl-leucyl-norleucinal (a calpain inhibitor), z-VAD-fmk (a pan-caspase inhibitor), and ammonium chloride and chloroquine (which stabilize lysosomes). These findings suggest that in addition to its other functions, BRCA1 may participate in mammalian heat shock response pathways.

BRCA1 Protein↗

PubMed1995

Expression of iNOS in cultured rat pulmonary artery smooth muscle cells is inhibited by the heat shock response.

The heat shock response is a highly conserved stress response known to alter patterns of gene expression in many cell types. We hypothesized that interleukin-1 beta (IL-1 beta)-mediated inducible nitric oxide synthase (iNOS) gene expression would be inhibited after induction of the heat shock response in cultured rat pulmonary artery smooth muscle cells (RPASMC). Exposure of RPASMC to sodium arsenite or heat led to expression of heat shock protein-70 (HSP-70) in a time- and concentration-dependent manner. Prior induction of the heat shock response inhibited IL-1 beta-mediated iNOS gene expression in a time- and dose-dependent manner. The inhibitory effects were not due to cytotoxicity, since cell viability was not affected by either sodium arsenite, heat, IL-1 beta, or their combination. Transcriptional analysis via transient transfection of the murine macrophage iNOS promoter [-1592 and -367 base pairs (bp)], upstream from the reporter gene luciferase, revealed that the heat shock response did not affect IL-1 beta-mediated promoter activation, as measured by luciferase activity. We conclude that induction of the heat shock response inhibits IL-1 beta-mediated iNOS gene expression in cultured RPASMC.

Animals↗

PubMed1998

Requirement for Hsp90 and a CyP-40-type cyclophilin in negative regulation of the heat shock response.

The heat shock response is a highly conserved mechanism that allows cells to withstand a variety of stress conditions. Activation of this response is characterized by increased synthesis of heat shock proteins (HSPs), which protect cellular proteins from stress-induced denaturation. Heat shock transcription factors (HSFs) are required for increased expression of HSPs during stress conditions and can be found in complexes containing components of the Hsp90 molecular chaperone machinery, raising the possibility that Hsp90 is involved in regulation of the heat shock response. To test this, we have assessed the effects of mutations that impair activity of the Hsp90 machinery on heat shock related events in Saccharomyces cerevisiae. Mutations that either reduce the level of Hsp90 protein or eliminate Cpr7, a CyP-40-type cyclophilin required for full Hsp90 function, resulted in increased HSF-dependent activities. Genetic tests also revealed that Hsp90 and Cpr7 function synergistically to repress gene expression from HSF-dependent promoters. Conditional loss of Hsp90 activity resulted in both increased HSF-dependent gene expression and acquisition of a thermotolerant phenotype. Our results reveal that Hsp90 and Cpr7 are required for negative regulation of the heat shock response under both stress and nonstress conditions and establish a specific endogenous role for the Hsp90 machinery in S. cerevisiae.

Carrier Proteins↗

PubMed2025

Nuclear and cytosolic J-domain proteins provide synergistic control of Hsf1 at distinct phases of the heat shock response.

The heat shock response (HSR) is the major defense mechanism against proteotoxic stress in the cytosol and nucleus of eukaryotic cells. Initiation and attenuation of the response are mediated by stress-dependent regulation of heat shock transcription factors (HSFs). Saccharomyces cerevisiae encodes a single HSF (Hsf1), facilitating the analysis of HSR regulation. Hsf1 is repressed by Hsp70 chaperones under non-stress conditions and becomes activated under proteotoxic stress, directly linking protein damage and its repair to the HSR. J-domain proteins (JDPs) are essential for targeting of Hsp70s to their substrates, yet the specific JDP(s) regulating Hsf1 and connecting protein damage to HSR activation remain unclear. Here, we show that the yeast nuclear JDP Apj1 primarily controls the attenuation phase of the HSR by promoting Hsf1's displacement from heat shock elements in target DNA. In apj1Δ cells, HSR attenuation is significantly impaired. Additionally, yeast cells lacking both Apj1 and the major JDP Ydj1 exhibit increased HSR activation even in non-stress conditions, indicating their distinct regulatory roles. Apj1's role in both nuclear protein quality control and Hsf1 regulation underscores its role in directly linking nuclear proteostasis to HSR regulation. Together, these findings establish the nucleus as key stress-sensing signaling hub.

Saccharomyces cerevisiae Proteins↗

PubMed1996

The heat shock response and major heat shock proteins of Tritrichomonas mobilensis and Tritrichomonas augusta.

The responses to heat shock in Tritrichomonas mobilensis, a squirrel monkey parasite and Tritrichomonas augusta, an amphibian trichomonad, were evaluated by means of metabolic labeling with [35S]methionine. Electrophoretically separated trichomonad proteins synthesized at different temperatures were visualized by autoradiography and the label incorporation quantitated by a trichloroacetic acid precipitation procedure. A considerable difference in thermotolerance between the two species was found as the protein synthesis reached a maximum at 41 C in T. mobilensis and 37 C in T. augusta. The latter tolerated temperature increases 13 C above normal cultivation temperatures as compared to only 4 C thermotolerance range above normal in T. mobilensis. Major heat shock proteins (Hsps) were expressed in both T. mobilensis (with apparent Mr 94, 72, and 58 kDa) and T. augusta (Mr 94, 70, and 56 kDa) as revealed by autoradiography. Western blot analysis with polyclonal antibody against DnaK of Escherichia coli showed the presence of antigenic Hsp70 homologs in both trichomonads. Similarly, a polyclonal antibody against Hsp60 with broad interspecies cross-reactivity detected Hsp60 homologs in both T. mobilensis and T. augusta. The anti-DnaK antibody cross-reacted with a T. mobilensis protein localized in Golgi apparatus as demonstrated by immunoelectron microscopy. Immunocytochemistry on trichomonad frozen sections revealed the presence of the Hsp60 homolog in light-microscopic granules corresponding to hydrogenosomes.

Animals↗

PubMed1989

Characterization of the heat shock response in cultured sugarcane cells : I. Physiology of the heat shock response and heat shock protein synthesis.

Effect of heat shock on the growth of cultured sugarcane cells (Saccharum officinarum L.) was measured. Heat shock (HS) treatment at 36 to 38 degrees C (2 hours) induced the development of maximum thermotolerance to otherwise nonpermissive heat stress at 54 degrees C (7 minutes). Optimum thermotolerance was observed 8 hours after heat shock. Development of thermotolerance was initiated by treatments as short as 30 minutes at 36 degrees C. Temperatures below 36 degrees C or above 40 degrees C failed to induce maximum thermotolerance. In vivo labeling revealed that HS at 32 to 34 degrees C induced several high molecular mass heat shock proteins (HSPs). A complex of 18 kilodalton HSPs required at least 36 degrees C treatment for induction. The majority of the HSPs began to accumulate within 10 minutes, whereas the synthesis of low molecular mass peptides in the 18 kilodalton range became evident 30 minutes after initiation of HS. HS above 38 degrees C resulted in progressively decreased HSP synthesis with inhibition first observed for HSPs larger than 50 kilodaltons. Analysis of two-dimensional gels revealed a complex pattern of label incorporation including the synthesis of four major HSPs in the 18 kilodalton range and continued synthesis of constitutive proteins during HS.

Journal Article↗

PubMed2006

Feedback regulation of the heat shock response.

The heat shock response is triggered primarily by nonnative proteins accumulating in a stressed cell and results in increased expression of heat shock proteins (Hsps), i.e., of chaperones capable of participating in the refolding or elimination of nonnative proteins. Best known is the transcriptional part of this response that is mediated predominantly by heat shock factor 1 (HSF1). HSF1 activity is regulated at different levels by Hsps and co-chaperones and is modulated further by a number of mechanisms involving other stress-regulated aspects of cell metabolism.

Animals↗

PubMed2002

DnaK-sigma 32 interaction is temperature-dependent. Implication for the mechanism of heat shock response.

The heat shock response in bacteria is a complex phenomenon in which sigma 32 plays the central role. The DnaK/J chaperone system binds and promotes degradation of sigma 32 at lower temperatures. At heat shock temperatures, the DnaK/J-mediated degradation of sigma 32 is largely abolished by a mechanism, which is not yet fully understood. In this article we have shown that interaction of DnaK with sigma 32 is highly temperature-dependent. This interaction is completely abolished at 42 degrees C. To investigate the origin of such strong temperature dependence, we have monitored the structural changes that occur in the sigma 32 protein upon upshift of temperature and attempted to elucidate its functional roles. Upon a shift of temperature from 30 to 42 degrees C, the CD spectrum of sigma 32 becomes significantly more positive without significant change in either tryptophan fluorescence spectra or quenchability to external quenchers. 1,8-Anilinonaphthalene sulfonic acid binding at 42 degrees C is not significantly affected. The equilibrium guanidine hydrochloride denaturation of sigma 32 is biphasic. The first phase shifts to even lower guanidine hydrochloride concentrations at 42 degrees C, whereas the major phase remains largely unchanged. The sigma 32-core interaction remains unchanged as a function of temperature. This suggests that increased temperature destabilizes a structural element. We discuss the possible location of this temperature-sensitive structural element.

Amino Acid Sequence↗

PubMed1998

Potential protective role of the heat shock response in sepsis.

The heat shock response, a primitive and highly conserved cellular defense mechanism, has broad protective effects against sepsis-induced injury. In various models of sepsis, induction of the heat shock response protects against sepsis-induced mortality, organ injury, cardiovascular dysfunction, and apoptosis. The mechanisms by which the heat shock response protects against sepsis-induced injury are currently under investigation. One potential mechanism involves the ability of the heat shock response to inhibit proinflammatory responses. The heat shock response has been demonstrated to inhibit expression of the cytokines tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta. The heat shock response has also been demonstrated to inhibit cytokine-mediated expression of inducible nitric oxide synthase. Recent studies demonstrated that the heat shock response inhibits nuclear translocation of nuclear factor-kappaB (NF-kappaB), a transcription factor involved in the regulation of many proinflammatory responses. Heat shock response-mediated inhibition of NF-kappaB nuclear translocation involves stabilization of an NF-kappaB inhibitory protein called I-kappaBalpha. The heat shock response also increases expression of I-kappaBalpha, thus providing another potential mechanism by which the heat shock response can modulate proinflammatory responses. Future studies designed to further understand the protective role of the heat shock response against sepsis-induced injury may allow for the development of rational pharmacologic agents or gene therapy methods to safely induce the heat shock response as a strategy to treat patients with sepsis.

Cytokines↗

PubMed1993

Dual control of heat shock response: involvement of a constitutive heat shock element-binding factor.

Heat shock factor (HSF) has been implicated as the key regulatory protein in the heat shock response. Our studies on the response of rodent cells to heat shock or sodium arsenite indicate that a high level of HSF-DNA-binding activity, by itself, is not sufficient for the induction of hsp70 mRNA synthesis; furthermore, a high level of HSF binding is also not necessary for this induction. Analysis of the binding of protein factors to the heat shock element (HSE) in extracts of stressed rodent cells indicates that the regulation of heat shock response involves the heat-inducible HSF and a constitutive HSE-binding factor. Our results also suggest that overexpression of human hsp70 may decrease the level of heat-induced HSF-HSE-binding activity in rat cells.

Animals↗

PubMed2001

Genome-wide chromatin remodeling modulates the Alu heat shock response.

During heat shock recovery in Hela cells, the level of Alu RNA transiently increases with kinetics that approximately parallel the transient expression of heat shock protein mRNAs. Coincidentally, there is a transient increase in the accessibility of Alu chromatin to restriction enzyme cleavage suggesting that an opening and re-closing of chromatin regulates the Alu stress response. Similar changes occur in alpha satellite and LINE1 chromatin showing that heat shock induces a genome-wide remodeling of chromatin structure which is independent of transcription. The increased accessibility of restriction sites within these repetitive sequences is inconsistent with a simple lengthening of the nucleosome linker region but instead suggests a scrambling of nucleosome positions. Chromatin structure and its dynamics account for many of the principal features of SINE transcriptional regulation potentially providing a functional rationale for the dispersion and high copy number of SINEs.

Alu Elements↗

PubMed1990

Characterization of the heat shock response and identification of heat shock protein antigens of Borrelia burgdorferi.

The heat shock response of Borrelia burgdorferi B31 cells was characterized with regard to the heat shock proteins (Hsps) produced. Five to seven Hsps were detected by sodium dodecyl sulfate-gel electrophoresis and fluorography of proteins from cells labeled with [35S]methionine after shifts from 33 degrees C to 37 or 40 degrees C or from 20 degrees C to 33, 37, or 40 degrees C. Analysis of [35S]methionine-labeled Hsps by two-dimensional electrophoresis and autoradiography revealed 12 Hsps. Western immunoblot analysis with antisera to highly conserved Escherichia coli and Mycobacterium tuberculosis Hsps revealed a single 72-kilodalton (kDa) protein band that reacted with antibodies to E. coli DnaK and with antibodies to the M. tuberculosis 71-kDa Hsp homolog of E. coli DnaK. Two proteins with apparent molecular masses of 66 and 60 kDa reacted with antibodies against the M. tuberculosis 65-kDa Hsp homolog of E. coli GroEL. Human immune sera collected from patients with Lyme disease reacted with both the 66-kDa Hsp and the 60-kDa Hsp but failed to react with the 72-kDa Hsp. These data are discussed with regard to the possibility that host recognition of highly conserved epitopes of GroEL homologs of B. burgdorferi may result in autoimmune reactions causing arthritis and other pathologies.

Bacterial Proteins↗