Heat shock induced changes in the gene expression of terminally differentiating avian red blood cells

Reticulocytes, purified from the blood of quail and chickens recovering from anaemia, respond to heat shock by the new and (or) enhanced synthesis of heat-shock protein (HSPs) with relative molecular masses of greater than 400,000, 90,000, 70,000, and 26,000 (quail) or 24,000 (chicken) and the depressed synthesis of many proteins normally produced at a control temperature. The synthesis of these HSPs is noncoordinate since the expression of each protein depends upon the particular temperature and duration of the time at that temperature. Separation of proteins from quail reticulocytes into Triton X-100 soluble and insoluble fractions demonstrates that the 70,000 and 26,000 Da HSPs are found in both fractions, whereas the greater than 400,000 and 90,000 Da HSPs are located only in the detergent-soluble fraction. Triton X-100 fractionation also reveals that there are three isoelectric variants of the 70,000 Da HSP and that they are constitutively synthesized and selectively partitioned between cellular compartments. Heat shock induced synthesis of the 90,000, 70,000, and 26,000 Da quail HSPs is prevented by actinomycin D, while enhanced synthesis of the greater than 400,000 Da HSP is unaffected by this inhibitor. These results demonstrate that nucleated, terminally differentiating avian red blood cells are capable of responding to heat stress by rapid changes in their highly restricted "program" of gene expression.     

Detailed characterization of heat shock protein synthesis and induced thermotolerance in seedlings of Sorghum bicolor L.

Tolerance of both protein synthesis and seedling growth to apreviously lethal high temperature can be induced by prior exposureto a sub-lethal temperature during which the synthesis of heatshock proteins (HSPs) occurs. In this study, a thermal gradientbar was used to measure the physiological effects of temperatureon seedlings of sorghum (Sorghum bicolor L.) in conjunctionwith studies of gene expression. The duration of HSP synthesis,both during continued high temperature treatment or on returnto normal temperatures, was found to be very finely modulatedand was dependent on the severity of the initial heat shock.The synthesis of heat shock proteins and the induction of thermotolerancewere rapid, reversible and reinducible phenomena. Maximal thermotolerancewas obtained after treatments that induced the full complementof HSPs. Subsequent treatments that repressed HSP synthesis,also abolished thermotolerance. The presence of HSPs, however,was not sufficient for the tissue to be in a thermotolerantstate and the results suggest that either their de novo synthesis,or some other factor, is required for the induction of thermotolerance.Pre-existing HSPs did not inhibit the synthesis of new HSPs.Although the kinetics of the synthesis of HSPs and the developmentof thermotolerance show a tight correlation, the kinetics ofthe decay of thermotolerance and the degradation of HSPs werenot linked. The functional state or distribution of HSPs maywell change during the recovery process. Key words: Heat shock, thermotolerance, Sorghum bicolor, growth, protein synthesis     

Increased thermostability of thermotolerant CHL V79 cells as determined by differential scanning calorimetry

Heat shock denatures cellular protein and induces both a state of acquired thermotolerance, defined as resistance to a subsequent heat shock, and the synthesis of a category of proteins referred to as heat-shock proteins (HSPs). Thermotolerance may be due to the stabilization of thermolabile proteins that would ordinarily denature during heat shock, either by HSPs or some other factors. We show by differential scanning calorimetry (DSC) that mild heat shock irreversibly denatures a small fraction of Chinese hamster lung V79-WNRE cell protein (i.e., the enthalpy change, which is proportional to denaturation, on scanning to 45 degrees C at 1 degree C/min is approximately 2.3% of the total calorimetric enthalpy). Thermostability, defined by the extent of denaturation during heat shock and determined from DSC scans of whole cells, increases as the V79 cells become thermotolerant. Cellular stabilization appears to be due to an increase in the denaturation temperature of the most thermolabile proteins; there is no increase in the denaturation temperatures of the most thermally resistant proteins, i.e., those denaturing above 65 degrees C. Cellular stabilization is also observed in the presence of glycerol, which is known to increase resistance to heat shock and to stabilize proteins in vitro. A model is presented, based on a direct relationship between the extent of hyperthermic killing and the denaturation or inactivation of a critical target that defines the rate-limiting step in killing, which predicts a transition temperature (Tm) of the critical target for control V79-WNRE cells of 46.0 degrees C and a Tm of 47.3 degrees C for thermotolerant cells. This shift of 1.3 degrees C is consistent with the degree of stabilization detected by DSC.     

Tissue-specific expression of sunflower heat shock proteins in response to water stress

Accumulation of mRNA and synthesis of low-molecular-weight heat shock proteins (LMW HSPs) was investigated in water-stressed sunflower, under experimental conditions resulting in little or no thermal stress. Using probes and antibodies derived from developmentally expressed LMW HSPs, it was shown that homologous mRNAs and proteins accumulate in the stem and root of water-stressed plants. This expression is quantitatively comparable with the response to heat shock: protein and mRNA accumulate to similar, high, levels and persist for comparable times during recovery from either environmental stress. However, it is shown that LMW HSPs with different molecular weights and isoelectric points are expressed in response to heat shock or water stress. Furthermore in situ localizations show a differential tissue-specificity for the water-stress- and heat-shock-induced LMW HSPs. Whereas the latter are localized mostly around the xylem vessels in the stem, the water-stress-induced proteins accumulate in the fascicular and interfascicular cambium. The possible functional implications for this specific expression are discussed.     

Heat shock gene expression in Xenopus laevis A6 cells in response to heat shock and sodium arsenite treatments

Continuous exposure of a Xenopus laevis kidney epithelial cell line, A6, to either heat shock (33 degrees C) or sodium arsenite (50 microM) resulted in transient but markedly different temporal patterns of heat-shock protein (HSP) synthesis and HSP 70 and 30 mRNA accumulation. Heat-shock-induced synthesis of HSPs was detectable within 1 h and reached maximum levels by 2-3 h. While sodium arsenite induced the synthesis of some HSPs within 1 h, maximal HSP synthesis did not occur until 12 h. The pattern of HSP 70 and 30 mRNA accumulation was similar to the response observed at the protein level. During recovery from heat shock, a coordinate decline in HSPs and HSP 70 and 30 mRNA was observed. During recovery from sodium arsenite, a similar phenomenon occurred during the initial stages. However, after 6 h of recovery, HSP 70 mRNA levels persisted in contrast to the declining HSP 30 mRNA levels. Two-dimensional polyacrylamide gel electrophoresis revealed the presence of 5 HSPs in the HSP 70 family, of which two were constitutive, and 16 different stress-inducible proteins in the HSP 30 family. In conclusion, heat shock and sodium arsenite induce a similar set of HSPs but maximum synthesis of the HSP is temporally separated by 12-24 h.     

昆虫的热休克反应和热休克蛋白

热休克（热激heatshock）是指短暂、迅速地向高温转换所诱导出的一种固定的应激反应。诱导该反应的温度在种与种之间有所不同。热休克反应最明显的特征是：伴随着正常蛋白质合成的抑制,一部分特殊蛋白质的诱导和表达增加,即为热休克蛋白（heatshockproteins,HSPs）。尽管热休克蛋白的合成也能被其它形式的应激反应所诱导,将它们认为是应激蛋白可能更恰当,但人们习惯上仍将这类蛋白质称为热休克蛋白。由于热休克反应和热休克蛋白是在果蝇（Drosophiliamelanogaster）中最初发现的,故在昆虫中,特别是果蝇等双翅目昆虫中研究得较深入…     

Heat shock proteins and effects of heat shock in plants

Soybean seedlings when exposed to a heat shock respond in a manner very similar to that exhibited by cultured cells, and reported earlier [2]. Maximum synthesis of heat shock proteins (HSPs) occurs at 40C. The heat shock response is maintained for a relatively short time under continuous high temperature. After 2.5 hr at 40 C the synthesis of HSPs decreases reaching a very low level by 6 hr. The HSPs synthesized by cultured cells and seedlings are identical and there is a large degree of similarity in HSPs synthesized between the taxonomically widely separated species, soybean and corn. Storage protein synthesis in the developing soybean embryo is not inhibited but is actually stimulated during a heat shock, unlike most other non-HSPs, whose synthesis is greatly reduced. Seedlings respond differently to a gradual increase in temperature than they do a sudden heat shock. There is an upward shift of several degrees in the temperature at which maximum protein synthesis occurs and before it begins to be inhibited. In addition, there appears to be a protection of normal protein synthesis from heat shock inhibition when the temperature increase is gradual. An additional function of the heat shock phenomenon might be the protection of seedlings from death caused by extreme heat stress. The heat shock response appears to have relevance to plants in the field.     

Thermal stress and neural function: adaptive mechanisms in insect model systems

Neural circuit function is vulnerable to hyperthermic failure but can be protected by stress pretreatments, such as exposure to a brief, sub-lethal high temperature (heat shock, HS), by increasing the time to failure and decreasing the time to recover.

Insects provide excellent model systems to investigate potential mechanisms underlying thermotolerant operation.

Induced thermotolerance is mediated by increased expression of heat shock proteins, HSPs, notably HSP70. Enhanced expression of HSP70 by increasing the gene dosage does not improve HS-induced thermotolerance of larval locomotion or locomotor central pattern generation in Drosophila.

Prior stress down-regulates neuronal K⁺ currents and this is associated with adaptive increases in the duration of action potentials.

Hyperthermic failure and recovery of the ventilatory central pattern generator in locusts is tightly correlated with a catastrophic increase in extracellular K⁺ concentration and its subsequent restoration.

These, and other data, suggest that neural circuit function can be protected by a stress-induced upregulation of HSPs that stabilize the cytoskeleton and preserve the operation of important membrane proteins such as ion channels, receptors and the Na⁺/K⁺-ATPase.     

玉米胚发育过程中热激蛋白的合成

35S-Met标记玉米胚蛋白合成结果表明,热激处理(42℃)与对照(25℃)的蛋白合成趋势相近,热激抑制16 DAP的蛋白合成,增加22和34 DAP蛋白合成.SDS-PAGE自显影图谱表明,热激诱导16DAP的胚合成86.4、80.0、73.2 kD等3种分子量较高的热激蛋白,22DAP后热激诱导合成86.4、80.0、73.2、24.4、18.2、16.8和13.6 kD等7种分子量的热激蛋白.2D-PAGE自显影图谱进一步显示,热激诱导22和28 DAP的胚合成近20种热激蛋白,其中超过10种为小分子热激蛋白.特异热激蛋白BiP(HsP70)、PDI(HsP60)Western blot表明,这2种热激蛋白在玉米胚发育过程均有高水平的表达,热激对其合成影响不明显.     

Heat shock protein expression in thermotolerant and thermosensitive lines of cotton

The expression of heat shock proteins (HSPs) was compared between genetically characterized heat tolerant and heat sensitive lines of cotton (Gossypium hirsutum andG. barbadense) using electrophoretic analysis ofin vivo labelled proteins. No differences were observed between the two lines with regard to: the temperature at which HSP synthesis was induced (37°C); the temperature at which HSP synthesis was maximal (45°C); the rates of recovery from HSP synthesis; the duration of HSP synthesis; or the major size classes of HSPs expressed in these two lines. Several HSPs were identified on 2D gels which were expressed uniquely in either the tolerant or sensitive cotton line. However, the HSP pattern displayed in a heat tolerant BC-3 individual was that of the heat sensitive parent.Abbreviations HSPs heat shock proteins - IEF isoelecticfocusing     

Expression of heat shock proteins and heat shock protein messenger ribonucleic acid in human prostate carcinoma in vitro and in tumors in vivo

Heat shock proteins (HSPs) are thought to play a role in the development of cancer and to modulate tumor response to cytotoxic therapy. In this study, we have examined the expression of hsf and HSP genes in normal human prostate epithelial cells and a range of prostate carcinoma cell lines derived from human tumors. We have observed elevated expressions of HSF1, HSP60, and HSP70 in the aggressively malignant cell lines PC-3, DU-145, and CA-HPV-10. Elevated HSP expression in cancer cell lines appeared to be regulated at the post-messenger ribonucleic acid (mRNA) levels, as indicated by gene chip microarray studies, which indicated little difference in heat shock factor (HSF) or HSP mRNA expression between the normal and malignant prostate cell lines. When we compared the expression patterns of constitutive HSP genes between PC-3 prostate carcinoma cells growing as monolayers in vitro and as tumor xenografts growing in nude mice in vivo, we found a marked reduction in expression of a wide spectrum of the HSPs in PC-3 tumors. This decreased HSP expression pattern in tumors may underlie the increased sensitivity to heat shock of PC-3 tumors. However, the induction by heat shock of HSP genes was not markedly altered by growth in the tumor microenvironment, and HSP40, HSP70, and HSP110 were expressed abundantly after stress in each growth condition. Our experiments indicate therefore that HSF and HSP levels are elevated in the more highly malignant prostate carcinoma cells and also show the dominant nature of the heat shock-induced gene expression, leading to abundant HSP induction in vitro or in vivo.     

Induction of acquired thermotolerance in Tetrahymena thermophila: effects of protein synthesis inhibitors.

When Tetrahymena thermophila cells growing at 30 degrees C are shifted to either 40 or 43 degrees C, the kinetics and extent of induction of heat shock mRNAs in both cases are virtually indistinguishable. However, the cells shifted to 40 degrees C show a typical induction of heat shock protein (HSP) synthesis and survive indefinitely (100% after 24 h), whereas those at 43 degrees C show an abortive synthesis of HSPs and die (less than 0.01% survivors) within 1 h. Cells treated at 30 degrees C with the drugs cycloheximide or emetine, at concentrations which are initially inhibitory to protein synthesis and cell growth but from which cells can eventually recover and resume growth, are after this recovery able to survive a direct shift from 30 to 43 degrees C (ca. 70% survival after 1 h). This induction of thermotolerance by these drugs is as efficient in providing thermoprotection to cells as is a prior sublethal heat treatment which elicits the synthesis of HSPs. However, during the period when drug-treated cells recover their protein synthesis ability and simultaneously acquire the ability to subsequently survive a shift to 43 degrees C, none of the major HSPs are synthesized. The ability to survive a 1-h, 43 degrees C heat treatment, therefore, does not absolutely require the prior synthesis of HSPs. But, as extended survival at 43 degrees Celsius depends absolutely on the ability of cells to continually synthesize HSPs, it appears that a prior heat shock as well as the recovery from protein synthesis inhibition elicits a change in the protein synthetic machinery which allows the translation of HSP mRNAs at what would otherwise be a nonpermissive temperature for protein synthesis.