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At least 595 records · Page 33Linked to original sources
PubMed1993

Characterization of a novel chicken heat shock transcription factor, heat shock factor 3, suggests a new regulatory pathway.

We have cloned three avian heat shock transcription factor (HSF) genes corresponding to a novel factor, HSF3, and the avian homologs of mammalian HSF1 and HSF2. The predicted amino acid sequence of HSF3 is approximately 40% related to the sequence of HSF1 and HSF2. The sequences for all three factors exhibit extensive identify in the DNA binding motifs and the heptad repeats of hydrophobic amino acids which are common to all eukaryotic HSFs. Despite these overall similarities, each avian HSF exhibits distinct DNA binding properties. HSF2 when expressed in vitro binds constitutively to the heat shock element promoter sequence, whereas neither HSF1 nor HSF3 expressed in vitro binds to DNA. HSF1 DNA binding is induced upon heat shock or treatment with nonionic detergents, whereas the DNA binding properties of HSF3 are not induced by these conditions in vitro. These results suggest that HSF3 activation may involve an induction pathway distinct from the traditional forms of heat shock gene induction. HSF3 DNA binding activity, however, is obtained when the carboxyl-terminal region including the distal heptad repeat is deleted, indicating the presence of negative cis-regulatory sequences. The HSF3 message, like HSF1 and HSF2 messages, is coexpressed during development and in most tissues, which suggests a general role for the regulatory pathway involving HSF3.

Age Factors↗
PubMed2004

Phosphorylation of the yeast heat shock transcription factor is implicated in gene-specific activation dependent on the architecture of the heat shock element.

Heat shock transcription factor (HSF) binds to the heat shock element (HSE) and regulates transcription, where the divergence of HSE architecture provides gene- and stress-specific responses. The phosphorylation state of HSF, regulated by stress, is involved in the activation and inactivation of the transcription activation function. A domain designated as CTM (C-terminal modulator) of the Saccharomyces cerevisiae HSF is required for the activation of genes containing atypical HSE but not typical HSE. Here, we demonstrate that CTM function is conserved among yeast HSFs and is necessary not only for HSE-specific activation but also for the hyperphosphorylation of HSF upon heat shock. Moreover, both transcription and phosphorylation defects due to CTM mutations were restored concomitantly by a set of intragenic suppressor mutations. Therefore, the hyperphosphorylation of HSF is correlated with the activation of genes with atypical HSE but is not involved in that of genes with typical HSE. The function of CTM was circumvented in an HSF derivative lacking CE2, a yeast-specific repression domain. Taken together, we suggest that CTM alleviates repression by CE2, which allows HSF to be heat-inducibly phosphorylated and presume that phosphorylation is a prerequisite for the activator function of HSF when it binds to an atypical HSE.

Amino Acid Sequence↗
PubMed2004

Expression of cytoprotective proteins, heat shock protein 70 and metallothioneins, in tissues of Ostrea edulis exposed to heat and heavy metals.

Heat shock proteins (Hsps) are constitutively expressed in cells and involved in protein folding, assembly, degradation, intracellular localization, etc, acting as molecular chaperones. However, their overexpression represents a ubiquitous molecular mechanism to cope with stress. Hsps are classified into families, and among them the Hsp70 family appears to be the most evolutionary preserved and distributed in animals. In this study, the expression of Hsp70 and the related messenger ribonucleic acid (mRNA) has been studied in Ostrea edulis after exposure to heat and heavy metals; moreover, levels of metallothioneins (MTs), another class of stress-induced proteins, have contemporaneously been assessed in the same animals. Thermal stress caused the expression of a 69-kDa inducible isoform in gills of O edulis but not in the digestive gland. Northern dot blot analysis confirmed that the transcription of Hsp69-mRNA occurs within 3 hours of stress recovery after oyster exposure at 32 and 35 degrees C. Hsp69-mRNA transcripts were not present in the gills of animals exposed to 38 degrees C after 3 hours of poststress recovery, but they were detected after 24 hours. The expression of the 69-kDa protein in O edulis exposed to 38 degrees C was rather low or totally absent, suggesting that the biochemical machinery at the base of the heat shock response is compromised. Together with the expected increase in MT content, the oysters exposed to Cd showed a significant enhancement of Hsp70, although there was no clear appearance of Hsp69. Interestingly, the levels of MT were significantly increased in the tissues of individuals exposed to thermal stress. Unlike oysters, heat did not provoke the expression of inducible Hsp isoforms in Mytilus galloprovincialis, Tapes philippinarum, and Scapharca inaequivalvis, although it significantly enhanced the expression of constitutive proteins of the 70-kDa family. The expression of newly synthesized Hsp70 isoforms does not seem therefore a common feature in bivalves exposed to thermal stress.

Animals↗
PubMed1999

Stress-induced activation of the heat-shock response: cell and molecular biology of heat-shock factors.

Exposure of cells to environmental and physiological stress leads to an imbalance in protein metabolism, which challenges the cell to respond rapidly and precisely to the deleterious effects of stress on protein homoeostasis. The heat-shock response, through activation of heat-shock transcription factors (HSFs) and the elevated expression of heat-shock proteins and molecular chaperones, protects the cell against the accumulation of non-native proteins. Activation of HSF1 involves a complex multi-step pathway in which the inert monomer oligomerizes to a DNA-binding, transcriptionally active, trimer which relocalizes within the the nucleus to form stress-induced HSF1 granules. Attenuation of the heat-shock response involves molecular chaperones which repress the HSF1 transactivation domain and HSF-binding protein 1 (HSBP1), which interacts with the HSF1 oligomerization domain of HSF1 to negatively regulate its activity, thus insuring that the expression of chaperones is precisely determined.

Animals↗
PubMed2003

Effect of hyperglycemia and nitric oxide synthase inhibition on heat tolerance and induction of heat shock protein 72 kDa in vivo.

Diabetes and nitric oxide synthase (NOS) inhibition both exacerbate mesenteric ischemia/ reperfusion injury. Heat shock protein 72 (HSP-72) protects against KDa ischemia/reperfusion damage in vivo. The effect of diabetes on HSP-72 expression in vivo is unknown. The aim of this study was to determine the effects of diabetes and NOS inhibition on HSP-72 induction in vivo. Rats were assigned to four groups: control (C), streptozotocin-induced diabetic (D), acute hyperglycemia (A), and L-N(omega)-nitro-L-arginine treated (L). Rats were subjected to hyperthermia and allowed to recover for 4 hours. Intestine and liver samples from heated (H) and nonheated (NH) rats were analyzed for HSP-72 by Western blot. HSP-72 levels were increased significantly in CH compared to CNH rats. No deaths occurred in CH rats; however, death rates were significant in AH, DH, and LH rats. DH rats died earlier than LH and AH rats. HSP-72 in liver and intestine was reduced significantly in LH rats. When compared with CH rats the surviving AH and DH rats exhibited similar HSP-72 levels in the liver. Diabetes, acute hyperglycemia, and L-N(omega)-nitro-L-arginine treatment lower heat stress tolerance. NOS is required for HSP-72 expression, but not survival. Diabetics who survive heat stress moderately express HSP-72. Characterization of altered thermotolerance and HSP-72 may provide mechanisms for the deranged diabetic stress response.

Acute Disease↗
PubMed1999

Presence of molecular chaperones, heat shock cognate (Hsc) 70 and heat shock proteins (Hsp) 40, in the postsynaptic structures of rat brain.

The synaptic localization of molecular chaperones, heat shock cognate protein 70 (Hsc70) and Hsp40, was investigated immunohistochemically in the normal rat brain. Postsynaptic density (PSD) fractions contained a constitutive form of HSP70, heat shock cognate protein 70 (Hsc70 or p73) but not inducible form of HSP70 (p72). The immunoreactivities of Hsc70 (p73) were distributed throughout the rat brain, in neuronal somata, dendrites and axons. Their immunoreactivity in neurons was localized in the cytoplasmic matrix, dendrites, and spines at the electron microscopic level. Presynaptic terminals, but less frequently than postsynaptic staining, were also reactive. Postsynaptic areas immediately beneath the synaptic contact or PSDs were immunoreactive for Hsc70. The Hsp40 was highly concentrated in PSD fractions. The staining of Hsp40 immunoreactivity was punctate and distributed widely in the brain. Hsp40 immunoreactivity was localized in dendritic spines, especially in the subsynaptic web, with weak staining of PSDs at the electron microscopic level. Double immunofluorescent staining and confocal microscopy revealed that Hsc70 and Hsp40 were co-localized on somata and neuronal processes of cultured cerebral neurons, on which synaptophysin immunoreactive spots were scattered. These results suggest that Hsp40 and Hsc70 are co-localized at postsynaptic sites and postsynaptic chaperone activity may be mediated by these two heat shock proteins.

Animals↗
PubMed1998

Interaction of heat stress glycoprotein GP50 with classical heat-shock proteins.

Cellular stress conditions are known to elevate heat-shock protein (HSP) synthesis and protein glycosylation, leading to the development of cellular thermotolerance. In the present study, we investigated the interaction of a major stress glycoprotein, GP50, with other cellular proteins during recovery from heat stress, using' mostly immunoprecipitation techniques. Parallel studies of heat-stressed CHO and M21 cells showed that both glycosylated and unglycosylated forms of GP50 interact with several members of the classical HSP families (e.g., HSP70 and HSP90) in an ATP-dependent manner. The specificity of HSP-stress glycoprotein interactions was confirmed by chemical crosslinking with a homobifunctional agent, 3,3'-dithiobis (succinimidyl propionate). Interaction of GP50 with denatured proteins was also demonstrated through binding to gelatin. Protein complexes formed between stress glycoproteins and HSPs were further characterized by gel filtration and showed an average molecular mass between 400 and 600 kDa. Overall, the consistent association of stress glycoproteins with nonglycosylated HSPs suggests a structural/functional role for protein chaperone complexes that consist of denatured proteins and the glycone/aglycone elements of cellular stress response.

Adenosine Triphosphate↗
PubMed2002

Exogenous expression of heat shock protein 90kDa retards the cell cycle and impairs the heat shock response.

The 90-kDa heat shock protein, HSP90, is an abundant molecular chaperone which functions in cellular homeostasis in prokaryotes and eukaryotes. It is well known that HSP90 plays a critical and indispensable role in regulating cell growth through modulations of various signal transduction pathways, but its roles in cell cycle control are not so well known. We transferred human HSP90 (wild-type or mutated types) expression vectors into NIH-3T3 cells in order to study certain functions of HSP90 in the cell cycle and cell growth under physiological conditions. We found that the exogenous expression of HSP90 (wild-type) induced a decrease in cell growth via retardation of the G1/S transition. The inhibition of cell growth was caused by reduced expressions of cyclin D3 and cyclin A mRNA and protein. On the other hand, no stable transfectants with the three types of mutated HSP90 were obtained. Unexpectedly, exogenous HSP90 expression impaired the heat shock response by inhibiting both heat shock transcription factor 1(HSF1) activation and transportation of HSF1 into the nucleus. The HSF1 function was disrupted by the direct association between HSF1 and exogenous HSP90, which was present as a monomer. These results reveal important roles of HSP90 in cell cycle control and in the stress response of nontransformed cells.

3T3 Cells↗
PubMed1996

Is heat shock protein re-induction during tolerance related to the stressor-specific induction of heat shock proteins?

The existence of stressor-specific induction programs of heat shock proteins (hsps) leads us to analyze the possible occurrence of a stressor-specific tolerance induced by either heat shock, arsenite, or cadmium. As a measure of this tolerance re-induction of hsps was studied. In this paper, we tested whether the refractory state is either valid for each specific hsp (implying independent regulation of every member of the heat shock protein family) or extends from small subsets of the hsp-family to even larger groups of proteins (indicating a more common denominator in their regulation). (re-)induction of hsps does not seem to be regulated at the level of each individual hsp since differences in induced synthesis of hsps between two stressor conditions are not supplemented systematically upon the sequential application of the two stressors. The most notable example in this respect is hsp60. A pretreatment with cadmium, which hardly induces synthesis of this hsp, does induce a tolerance to (re)-induction by heat shock, which normally induces hsp60. This suggests the existence of a more common denominator regulating the coordinate expression of at least some hsps. From our data we conclude that the degree, but not the pattern, of hsp re-induction is influenced by the type of stressor used in the pretreatment. The pattern of hsps induced by a secondary applied stressor still shows most of its stressor-specificity and seems to be independent of any pretreatment. The possible implications of stressor-specificity are discussed.

Animals↗
PubMed1992

Glutamine and glutamate metabolism in normal and heat shock conditions in Drosophila Kc cells: conditions supporting glutamine synthesis maximize heat shock polypeptide expression.

We have previously reported that Drosophila Kc cells require glutamine for maximal expression of heat shock proteins in stressed conditions (Sanders and Kon: J. Cell. Physiol. 146:180-190, 1991). The mechanism of this effect has been investigated by comparing the metabolic utilization of glutamine in conditions which support hsp expression with that of glutamate in conditions where up to 100-fold less hsp is synthesized. This comparison showed that free ammonia was generated by cells incubated in the presence of glutamine in 37 degrees C (heat shock) conditions, but not at 25 degrees C, and not in the presence of glutamate in either normal or heat shock conditions. There was no difference in the amount of [14C]O2 generated from either [14C]-labeled amino acid in the tricarboxylic acid cycle, but three- to four-fold more alanine was synthesized in cells incubated in glutamine than in glutamate. Treating the cells with aminotransferase inhibitors to artificially increase NH3 release raised hsp expression in the presence of glutamate to maximal levels characteristic of glutamine. This potentiation correlated with inhibition of alanine aminotransferase. Since only NH3 production correlated with hsp expression in heat shock conditions in the presence of glutamine, and NH3 addition to glutamate also resulted in maximal hsp expression, we measured glutamine production in glutamate plus NH3 and observed net glutamine synthesis. The supposition that glutamine itself is responsible for the regulatory changes supporting maximal hsp expression was supported by the finding that the glutamine analog, 6-diazo-5-oxo-L-norleucine (DON), mimicked the effects of glutamine. We conclude that glutamine imposes regulatory changes which alter nitrogen metabolism and support hsp expression in Kc cells.

Amino Acids↗
PubMed1992

Genetic differences in heat-induced tolerance to cadmium in cultured mouse embryos are not correlated with changes in a 68-kD heat shock protein.

Heat-induced cross-tolerance to cadmium was investigated in two inbred strains of mice, BALB/c and SWV, using a whole embryo culture system. Embryos were exposed to a pretreatment of 5 min at 43 degrees C and subsequently to an embryotoxic concentration of cadmium, 1.75 microM. The two types of embryos responded differently to the heat pretreatment, as cross-tolerance was induced in SWV but not in BALB/c mice. In SWV embryos, prior exposure to 43 degrees C for 5 min essentially eliminated the negative effects of cadmium on embryonic development and growth. However, in BALB/c embryos, no protection was observed. The variation in development of cross-tolerance in embryos from the two strains of mice was not correlated with differences in the induction of a 68-kD heat-shock protein (hsp68). There was a rapid increase in this protein in both strains after the initial heat exposure but not excess induction in the SWV strain that developed tolerance. The induction of hsp68 is therefore not sufficient to elicit cross-tolerance, and other mechanisms are likely to be important in the protective response of the embryo.

Animals↗
PubMed1994

Decrease of heat shock protein 27/28 with heat stress in HTLV-I-transformed cells.

We have previously reported an increase of human T-lymphotropic leukemia/lymphoma virus type I (HTLV-I) replication after heat treatment of MT-2 cells, an HTLV-I-transformed human lymphoid cell line. In this study, we investigated the effect of heat stress on the expression of Hsp27/28 in MT-2 cells. In contrast with previous studies of other cell types, a decrease of Hsp27/28 expression in MT-2 cells and an increase of Hsp70 family proteins in both MT-2 and uninfected lymphoid CEM cells were found following heat treatment at 42 degrees C. Furthermore, heat treatment resulted in an early rapid increase in the phosphorylated form of Hsp27/28 in both MT-2 and CEM cells. The results suggest that early post-translational phosphorylation of HSP27/28 could be a determinant of the ability of MT-2 cells to survive hyperthermia.

Blotting, Northern↗
PubMed1996

Heat shock elements are involved in heat shock promoter activation during tobacco seed maturation.

The soybean Gmhsp 17.3-B heat shock promoter is developmentally regulated in transgenic tobacco, as indicated by the constitutive expression of a beta-glucuronidase reporter in seeds [16]. In this paper, we show that both the heat shock promoter-driven beta-glucuronidase activity and the mRNA of the endogenous Nthsp18P gene accumulate coincident with the onset of seed desiccation. Deletions of the soybean Gmhsp17.3-B promoter, encompassing the heat shock element (HSE)-containing regions, revealed a co-localization of sequences responsible for heat induction and developmental expression. Moreover, synthetic HSEs fused to a TATA box sequence had the potential to stimulate the developmental expression of a GUS reporter gene in seeds of transgenic plants.

Base Sequence↗
PubMed1987

The use of operon fusions in studies of the heat-shock response: effects of altered sigma 32 on heat-shock promoter function in Escherichia coli.

Derivatives of lambda pF13 phage in which lacZ expression (beta-galactosidase synthesis) is directed by transcription initiated at a heat-shock promoter (PrpoDhs or PgroE) were constructed and used for analysis of the heat-shock response in Escherichia coli. A wild-type strain (MC4100) lysogenic for either of these phages exhibited typical transient induction of beta-galactosidase synthesis upon a temperature shift from 30 degrees to 42 degrees C or after addition of ethanol to the medium (4% to 5%) at 30 degrees C. In contrast, most amber rpoH (htpR) mutants tested (in a Su- background) failed to respond to a temperature shift, though some mutants affected in the carboxy-terminal region exhibited a partial response. All rpoH mutants tested showed a weak but significant response to ethanol. F' plasmids carrying each of six known nonsense suppressors were then introduced into each of four rpoH amber mutants lysogenic for lambda pF13-(Phs-lacZ), creating a set of F' strains that produce sigma 32 protein with a specific amino acid substitution at a known site. Some of these strains showed an essentially normal heat-shock response while others showed little response with either or both of the promoters. In some instances, the response was significantly delayed. These results point to the usefulness of the lambda pF13-derivative phages for quantitative and systematic analysis of heat-shock response in E. coli.

Bacterial Proteins↗
PubMed1992

Thermosensitization, heat shock protein synthesis and development of thermotolerance in M-14 human tumor cells subjected to step-down heating.

M-14 human tumor cells have been subjected to two regimens of step-down heating (SDH) consisting of a conditioning treatment at 42 degrees C for 1 h or at 44.5 degrees C for 20 min, immediately followed by heating at 40 degrees C. Both conditioning treatments thermosensitize the cells towards the subsequent heating at 40 degrees C; the thermosensitization ratio is 6.4 for cells conditioned at 42 degrees C for 1 h and 32.3 for cells conditioned at 44.5 degrees C for 20 min. The overall protein synthetic activity is reduced to 32.7% or 18.4% of control values following 1 h at 42 degrees C and 20 min at 44.5 degrees C, respectively; this inhibition is followed by a full recovery of the synthetic activity during the subsequent exposure at 40 degrees C. SDH-treated cells synthetize four heat shock proteins, with approximate molecular weights of 28, 64, 70 and 90 kDa. The pattern of HSPs induction observed in SDH-treated cells is similar to that found in cells subjected to single hyperthermic exposures. Cells subjected to the SDH sequence 42 degrees C/1 h-->40 degrees C/4 h develop thermotolerance, as indicated by a reduced sensitivity to further hyperthermic challenges.

Animals↗
PubMed1998

Metal chelator NNNNN-tetrakis-(2-pyridymethyl)ethylene diamine inhibits the induction of heat shock protein 70 synthesis by heat in cultured keratinocytes.

Heat shock protein (HSP) synthesis results from various types of injury, including heat shock (HS) and some oxidants. The intracellular signals leading to HSP synthesis are not yet fully elucidated. We have studied the influence of NNN'N'-tetrakis(2-pyridylmethyl)ethylene diamine (TPEN), a metal chelator known to induce cellular zinc and copper deprivation, on resistance to heat and on hsp70 synthesis in HaCaT keratinocytes. TPEN was shown to sensitize HaCaT cells to heat shock. The effect of TPEN was neutralized by equimolar Zn2+. By the use of sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis and Western blotting characterization of hsp70, it was shown that cultured HaCaT cells constitutively express the inducible form of hsp70. The application of TPEN alone slightly increases the level of hsp70 but inhibits its induction by HS. This inhibitory effect is related to metal deprivation, because it is eliminated when Cu2+ or Zn2+ ions are supplied together with TPEN. These results suggest that these metals are involved in the expression by keratinocytes of a stress protein which has a protective action against environmental stress.

Cell Survival↗
PubMed1997

Developmental control of heat shock and chaperone gene expression. Hsp 70 genes and heat shock factors during preimplantation phase of mouse development.

Heat shock genes are found in all organisms, and synthesis of heat shock proteins is induced by various stressors in nearly all the cells forming these organisms. However, a particular situation is noticed for hsp 70 genes in mouse embryos at the beginning of their development. First, spontaneous expression of hsp 70 is observed at the onset of zygotic genome activity. Second, inducible expression is delayed until morula or early blastocyst stages. A better understanding of both these points depends on a more careful analysis of hsp 70 expression in relation to their major regulators, the heat shock factors. In this review, we will see how the development of the preimplantation embryo highlights the complexity of heat shock gene regulation involving trans-cis interactions and the cellular and nuclear environment.

Animals↗
PubMed2005

Cancer immunotherapy based on intracellular hyperthermia using magnetite nanoparticles: a novel concept of "heat-controlled necrosis" with heat shock protein expression.

Heat shock proteins (HSPs) are highly conserved proteins whose syntheses are induced by a variety of stresses, including heat stress. Since the expression of HSPs, including HSP70, protects cells from heat-induced apoptosis, HSP expression has been considered to be a complicating factor in hyperthermia. On the other hand, recent reports have shown the importance of HSPs, such as HSP70, HSP90 and glucose-regulated protein 96 (gp96), in immune reactions. If HSP expression induced by hyperthermia is involved in tumor immunity, novel cancer immunotherapy based on this novel concept can be developed. In such a strategy, a tumor-specific hyperthermia system, which can heat the local tumor region to the intended temperature without damaging normal tissue, would be highly advantageous. To achieve tumor-specific hyperthermia, we have developed an intracellular hyperthermia system using magnetite nanoparticles. This novel hyperthermia system can induce necrotic cell death via HSP expression, which induces antitumor immunity. In the present article, cancer immunology and immunotherapy based on hyperthermia, and HSP expression are reviewed and discussed.

Animals↗