Interaction of Hsp 70 with newly synthesized proteins: implications for protein folding and assembly

Slower skeletal muscle phenotypes are critical for constitutive expression of Hsp70 in overloaded rat plantaris muscle

Heat shock protein 72 (Hsp70) is constitutively expressed in rat hindlimb muscles, reportedly in proportion to their content of type I myosin heavy chain. This distribution pattern has been suggested to result from the higher recruitment and activity of such muscles and/or a specific relationship between myosin phenotype and Hsp70 content. To differentiate between these possibilities, the fiber-specific distribution of Hsp70 was examined in male Sprague-Dawley rat plantaris under control conditions, following a fast-to-slow phenotypic shift in response to surgically induced overload (O) and in response to O when the phenotypic shift was prevented by 3,5,3'-triiodo-dl-thyronine administration. Constitutive expression of Hsp70 was restricted to type I and IIa fibers in plantaris from control rats, and this fiber-specific pattern of expression was maintained following O of up to 28 days, although Hsp70 content in the O muscle doubled. When O (for 40 days) of the plantaris was combined with 3,5,3'-triiodo-dl-thyronine administration, despite typical hypertrophy in the overloaded plantaris, prevention of the normal phenotypic transformation also blocked the increased expression of Hsp70 observed in euthyroid controls. Collectively, these data suggest that chronic changes in constitutive expression of Hsp70 with altered contractile activity appear critically dependent on fast-to-slow phenotypic remodeling.

Purification and kinetic characterization of recombinant human mitogen-activated protein kinase kinase kinase COT and the complexes with its cellular partner NF-kappa B1 p105

Cancer osaka thyroid (COT), a human MAP 3 K, is essential for lipopolysaccharide activation of the Erk MAPK cascade in macrophages. COT 30--467 is insoluble, whereas low levels of COT 30--397 can be expressed, but this protein is unstable. However, both COT 30--467 and COT 30--397 are expressed in a soluble and stable form when produced in complex with the C-terminal half of p105. The k(cat) of COT 30--397 is reduced approximately 47--fold in the COT 30--467/p105 Delta N complex. COT prefers Mn(2+) to Mg(2+) as the ATP metal cofactor, exhibiting an unusually high ATP K(m) in the presence of Mg(2+). When using Mn(2+) as the cofactor, the ATP K(m) is reduced to a level typical of most kinases. In contrast, the binding affinity of COT for its other substrate MEK is cofactor independent. Our results using purified proteins indicate that p105 binding improves COT solubility and stability while down-regulating kinase activity, consistent with cellular data showing that p105 functions as an inhibitor of COT.

Molecular mechanisms responsible for alcohol-induced myopathy in skeletal muscle and heart

Chronic alcohol abuse has the potential to modulate striated muscle physiology and function. The skeletal muscle alcoholic myopathy is characterized by muscle weakness and difficulties in gait and locomotion, while chronic alcohol consumption ultimately leads to a decrease in cardiac contractility and output. In both tissues a loss of protein mass results in part from a decreased protein synthesis that initially manifests as a defect in translational efficiency. This review focuses on recent developments in understanding the cellular and molecular mechanisms by which alcohol impairs mRNA translation in skeletal and cardiac muscle, including identification of the signaling pathways and biochemical sites negatively impacted. Defective signaling potentially results from resistance to the normal stimulating effects of anabolic hormones (insulin and insulin-like growth factor-I) and nutrients (leucine) as well as increased production of several negative regulators of muscle mass. Overall, the biochemical mechanisms contributing to the pathogenesis of loss of skeletal and cardiac muscle are reviewed.

Oral administration of geranylgeranylacetone plus local somatothermal stimulation: A simple, effective, safe and operable preconditioning combination for conferring tolerance against ischemia-reperfusion injury in rat livers

AIM: To explore a simple, effective, safe and operable pretreatment for conferring tolerance against ischemia-reperfusion (I-R) injury in rat livers.

METHODS: Forty-five rats were divided into five groups (each group n = 9). Group C: control group; group G: geranylgeranylacetone (GGA) was administered without heat stress; group S: local heat stress alone; group WG: GGA plus whole-body heat stress; group SG: GGA administration plus local heat stress. After completion of the I-R procedure, the ischemic-reperfused liver lobes in five groups were resected and tested for heat shock protein (HSP70) by RT-PCR, Western blotting analysis and immunohistochemical staining. The blood samples were collected for ALT and AST measurement at the end of occlusion of blood supply, 30 min after reperfusion, 24, 48, 72 h after surgery from the inferior vena cava. Survival was monitored for 1 wk.

RESULTS: The production of HSP70 after I-R injury increased, the liver enzyme levels after reperfusion decreased rapidly, and the survival rates increased in groups C-SG.

CONCLUSION: The combination of GGA plus local somatothermal stimulation is a simple, effective, safe and operable pretreatment to induce HSP70 in patients with liver tumor and cirrhosis before hepatectomy and in donors before harvesting graft for liver transplantation.

[Heat shock proteins as molecular chaperones]

Exposure to different conditions or agents that destabilize cell homeostasis often alters protein folding. Depending on stress intensity irreversible protein aggregation and cell death can occur. Cells have developed a conserved defense mechanism aimed at reducing the deleterious effects induced by protein folding alteration. This mechanism is characterized by the expression of a small number of genes encoding specific proteins, named Hsps. Several of these proteins act as molecular chaperones through their ability to refold polypeptides with an altered conformation. Moreover, constitutive Hsps homologues have been characterized that participate in the folding of newly made polypeptides, in the assembly of protein complexes in the endoplasmic reticulum, in the translocation of polypeptides through membranes or in masking mutations that alter protein folding. Neurodegeneratives and cancereous diseases are discussed as examples where high levels of Hsp expression can be either beneficial or deleterious to the cells.

Retinal function following transpupillary thermotherapy for occult choroidal neovascularization in age-related macular degeneration: a short-term study by focal electroretinography

PURPOSE

To assess short-term changes in macular function after transpupillary thermotherapy (TTT) in patients with occult subfoveal choroidal neovascularization (CNV) secondary to age-related macular degeneration (AMD), using focal electroretinography (FERG).

METHODS

Twenty-five patients with occult subfoveal CNV due to AMD were treated with TTT delivered using an infrared (810 nm) diode laser (spot size 3.0 mm, laser power 400-600 mW, duration 60 seconds). All patients were clinically evaluated before, 1 and 6 weeks after treatment. Snellen visual acuity (VA) was measured at each visit. Fluorescein angiography (FA) was performed at baseline and 6 weeks after TTT. Focal ERGs were recorded in all patients immediately before and 1 week after TTT in response to an 18-degree diameter, 41 Hz flickering spot (630 nm) centred on the fovea, presented on a steady background in Maxwellian view. A subgroup of 12 patients was also re-tested by FERG at 6-weeks post-TTT.

RESULTS

No significant changes in mean FERG amplitude and phase were observed across the different recording sessions before and after TTT. One week after TTT, four patients had significant (> 2 SD from baseline variability) increases in FERG amplitude and/or phase advances, one had a decrease in amplitude and four had phase delays, compared to baseline. The remaining 15 patients had stable FERGs. Six weeks after TTT, four patients had significant increases in FERG amplitude and/or phase advances, four had decreases in amplitude and/or phase delays, and four had stable FERGs, compared to baseline. Improvement in FERG parameters after TTT was always associated with an improvement in VA and a decrease in exudation. Patients with post-TTT FERG deterioration had stable or deteriorated clinical pictures. At either 1 or 6 weeks post-TTT, the FERG amplitude increase was inversely correlated (p < 0.05) with the baseline FERG amplitude and VA.

CONCLUSIONS

Three major conclusions can be drawn: in a short-term follow-up, TTT was not found to be associated with significant changes in macular function; FERG improvement was associated with VA improvement, and the increase in FERG amplitude was greatest in patients with the worst baseline acuity.

Effect of mutation of amino acids 246-251 (KRKHKK) in HSP72 on protein synthesis and recovery from hypoxic injury

Heat shock protein (HSP)72, the inducible form of HSP70, protects cells against a variety of injuries, but underlying mechanisms are poorly defined. To investigate the protective effects of HSP72, multiple clones expressing wild-type (WT) HSP72 and two mutants with defective nucleolar and nuclear localization (M45 and 985A, respectively) were made with the tet-off system in C2C12 cells. Four different parameters of cell function/injury were examined after simulated ischemia: protein synthesis, polysome formation, DNA synthesis, and lactate dehydrogenase (LDH release). Overexpression of WT HSP72 was also compared to nontransfected C2C12 cells. As expected, overexpression of HSP72 protected against simulated ischemia and reoxygenation for all parameters. In contrast, both M45 and 985A showed abnormal protein synthesis and polysome formation, both after simulated ischemia and under control conditions. Total RNA was slightly reduced in M45 and 985A at baseline, but 1 h after hypoxia, RNA levels were protected in all clones but significantly decreased in nontransfected C2C12 cells. Clones expressing 985A had nuclear retention of mRNA, suggesting that HSP72 is needed for nuclear export of RNA. All clones, both WT and mutant, had protection of DNA synthesis compared to C2C12 cells, but 985A had greater release of LDH after injury than any other group. These results support a multifactoral protective effect of HSP72, some aspects dependent on nuclear localization with stress and some not. The protection of protein synthesis and polysome formation, and abnormalities in these with the mutants, support a role for HSP72 in these processes both in the normal cell and in injury.

Metabolomic and proteomic biomarkers for III–V semiconductors: Chemical-specific porphyrinurias and proteinurias

A pressing need exists to develop and validate molecular biomarkers to assess the early effects of chemical agents, both individually and in mixtures. This is particularly true for new and chemically intensive industries such as the semiconductor industry. Previous studies from this laboratory and others have demonstrated element-specific alterations of the heme biosynthetic pathway for the III-V semiconductors gallium arsenide (GaAs) and indium arsenide (InAs) with attendant increased urinary excretion of specific heme precursors. These data represent an example of a metabolomic biomarker to assess chemical effects early, before clinical disease develops. Previous studies have demonstrated that the intratracheal or subcutaneous administration of GaAs and InAs particles to hamsters produces the induction of the major stress protein gene families in renal proximal tubule cells. This was monitored by 35-S methionine labeling of gene products followed by two-dimensional gel electrophoresis after exposure to InAs particles. The present studies examined whether these effects were associated with the development of compound-specific proteinuria after 10 or 30 days following subcutaneous injection of GaAs or InAs particles in hamsters. The results of these studies demonstrated the development of GaAs- and InAs-specific alterations in renal tubule cell protein expression patterns that varied at 10 and 30 days. At the 30-day point, cells in hamsters that received InAs particles showed marked attenuation of protein expression, suggesting inhibition of the stress protein response. These changes were associated with GaAs and InAs proteinuria patterns as monitored by two-dimensional gel electrophoresis and silver staining. The intensity of the protein excretion patterns increased between the 10- and 30-day points and was most pronounced for animals in the 30-day InAs treatment group. No overt morphologic signs of cell death were seen in renal tubule cells of these animals. Western blot analyses of the urines with antibodies to the 32-, 70-, and 90-kDa stress protein families did not show the presence of these molecules, indicating that these proteins were not excreted in the urine samples. These data suggest that the observed proteinuria patterns were not a result of cell death and that the observed chemical-specific proteinurias were produced before marked cellular toxicity. These findings suggest a hypothesis involving GaAs and InAs interference with stress protein chaperoning of reabsorbed proteins for proteosomic degradation and the probable chaperoning of damaged intracellular proteins from renal proximal tubule cells into the urinary filtrate. Overall, the results of these studies provide further information on the nephrotoxicity of these semiconductor compounds. They also suggest the use of two-dimensional gel electrophoresis with silver staining of urinary protein patterns as a potentially useful proteomic approach to renal damage early in relation to intracellular proteotoxicity in kidney tubule cells.

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.

Geranylgeranylacetone ameliorates ischemic acute renal failure via induction of Hsp70

BACKGROUND

Heat shock proteins (HSPs) are well known as cytoprotective proteins. Geranylgeranylacetone (GGA), an antiulcer agent, has recently been shown to induce Hsp70. This study was performed to investigate the renoprotective properties of GGA.

METHODS

The effect of GGA on the induction of the major HSPs (Hsp90, Hsp70, Hsc70, Hsp60, and Hsp32) was studied in the rat kidney or rat primary cultures of tubular epithelial cells (R-TECs) by Western blot. Localization of Hsp70 was determined by immunohistochemistry. The renoprotective effects of GGA were studied using a rat model of ischemia/reperfusion (I/R) injury. GGA (400 mg/kg), GGA with quercetin pretreatment (100 mg/kg), or a vehicle was given to rats 24 hours and again 1 hour prior to the induction of I/R injury. Rats were sacrificed at 24 hours after reperfusion. Histologic analyses and terminal deoxynucleotidyl transferase (TdT)-mediated deoxyuridine triphosphate (dUTP) nick-end labeling (TUNEL) assay were performed. Blood urea nitrogen (BUN) and serum creatinine was also measured. The cytoprotective properties of GGA were also studied in vitro by treating R-TECs with GGA (10 mumol/L) or a vehicle, followed by incubation in culture medium with oxidative stress condition (0.5 mmol/L hydrogen peroxide) or ischemic condition (2 nmol/L NaCN and 20 mmol/L 2-deoxyglucose in the absence of medium glucose).

RESULTS

Oral administration of GGA induced Hsp70 expression in the kidney (which peaked at 24 hours) but did not induce Hsp90, Hsc70, Hsp60, or Hsp32. The induction of Hsp70 was blocked by quercetin. Immunohistochemistry showed that Hsp70 was localized mainly in the tubular epithelial cells. Preconditioning rats with GGA significantly decreased BUN and serum creatinine levels after I/R injury. Histologic examination revealed that GGA significantly attenuated tubular damage and macrophage infiltration. The number of TUNEL-positive cells also decreased significantly in the GGA group. Quercetin, an inhibitor of Hsp70 induction, eliminated these renoprotective effects of GGA. In in vitro study, GGA-induced Hsp70 in R-TECs, which peaked at 2 to 4 hours. Both oxidative stress and ischemic stimuli induced apoptosis in R-TECs. GGA significantly suppressed the number of apoptotic cells in both conditions.

CONCLUSION

The results support the hypothesis that GGA induces Hsp70, protects tubular epithelial cells from apoptosis, and thus ameliorates tubular damage by I/R injury. The present study suggests that GGA would be a useful tool in treating acute renal failure or preventing transplanted kidney damage in the clinical setting.

Possible role of calcineurin in heating-related increase of rat muscle mass

The purpose of this study was to investigate the contribution of calcineurin-related intracellular signal for heat-stress-associated muscle hypertrophy. Wistar strain male rats (7-week-old) were randomly divided into four groups: (1) control (CC, n=15), (2) control with the injection of cyclosporine A (CsA) (CA, n=15), (3) heat-stressed (HC, n=15), and (4) heat-stressed with the injection of CsA (HA, n=15). The heat-stress groups (HC and HA) were exposed to heat (41 degrees C for 60 min) in a controlled heat chamber without anesthesia. Soleus and extensor digitorum longus (EDL) muscles were dissected and weighed 1, 7, and 14 days after the exposure. Wet and dry weights of soleus were increased 7 days following heat exposure. The expressions of heat shock protein 72 (HSP72) and calcineurin in both muscles were also increased within 1 and 7 days following heat-stress, respectively. Administration of CsA, a specific inhibitor for calcineurin, depressed heat-stress-associated increase of muscle weight and calcineurin expression, especially in soleus. These observations suggest that a calcineurin-dependent signaling pathway may play an important role in the heat-stress-related skeletal muscular hypertrophy. Application of heat-stress to skeletal muscles may be a useful tool to gain muscular mass and force generation not only in athletes, but also in patients during rehabilitation.

Neuroprotective role of heat shock protein 70 in the rostral ventrolateral medulla during acute mevinphos intoxication in the rat

Heat shock protein (HSP) is a family of highly conserved proteins that respond to stress and participate actively in cytoprotection. Within the HSP family, HSP70 is the major inducible member that confers protection against cell death. This study investigated whether HSP70 plays a neuroprotective role at the rostral ventrolateral medulla (RVLM), the origin of sympathetic neurogenic vasomotor tone in the medulla oblongata where the organophosphate insecticide mevinphos (Mev) acts to elicit cardiovascular toxicity. Experiments were carried out in adult male Sprague-Dawley rats that were maintained under propofol anesthesia. Intravenous administration of Mev (960 microg/kg) induced a significant increase in the HSP70 level in the ventrolateral medulla during phase I ('pro-life' phase), and returned to baseline during phase II ('pro-death' phase) Mev intoxication. Compared to artificial cerebrospinal fluid, normal mouse serum (1:20), or sense hsp70 oligonucleotide (50 pmol) pretreatment, microinjection of an anti-HSP70 antiserum (1:20) or an antisense hsp70 oligonucleotide (50 pmol) bilaterally into the RVLM significantly increased mortality, shortened the duration of phase I intoxication and augmented the induced hypotension in rats that received Mev (960 microg/ kg, i.v.). These results suggest that HSP70 induced in the RVLM during Mev intoxication provides neuroprotection against the organophosphate poison via prevention of cardiovascular depression.

Cloning and molecular characterization of heat shock cognate 70 from tiger shrimp (Penaeus monodon)

We cloned the complementary deoxyribonucleic acid (cDNA) of the heat shock cognate 70 (hsc70) gene of tiger shrimp (Penaeus monodon). It was 2207 bp long and included a 1959-bp coding region, a 40-bp flanking region at the 5' end, and a 208-bp flanking region at the 3' end. The deduced, 652-amino acid sequence had a molecular mass of 71 481 Da and an estimated isoelectric point (pI) of 5.2. Based on phylogenetic analysis, the gene is clustered with the hsc70 proteins of invertebrates and vertebrates. In native gel electrophoresis, recombinant P. monodon hsc70 expressed in an Escherichia coli system is tightly associated with carboxymethylated alpha-lactalbumin (CMLA), which indicates that hsc70 probably functions as a chaperone. In an in vitro adenosine triphosphatase assay, recombinant hsc70 hydrolyzed adenosine triphosphate to adenosine-5'-diphosphate and increased hydrolysis activity by binding to unfolded peptide, CMLA. In situ hybridization using an antisense riboprobe revealed that the hsc70 gene was active in most tissues of unstressed shrimp. The expression of hsc70 messenger ribonucleic acid (mRNA) in hemocytes increased 2- to 3-fold at the first hour after shrimp experienced heat shock and 0.5-hour recovery. Hsc70 mRNA decreased gradually to the background level. Cloning and characterizing the P. monodon hsc70 gene is the first, crucial step in studying the relationship of heat shock proteins with the stress or immune responses of shrimp.

Heat stress facilitates the recovery of atrophied soleus muscle in rat

Effects of heat stress on the recovery of atrophied soleus muscle were studied in rats. Ten-week-old male Wistar rats were randomly divided into cage control (CC) and 5-day hindlimb suspension group (HS). The half of the rats in group HS was exposed to heat stress (41 degrees C for 60 min) in an incubator immediately after the hindlimb suspension (HS-H) and the other group of rats was not heat stressed (HS-C) prior to 10 days of ambulation recovery. One group of cage control rats (CH) was also exposed to heat similarly. The soleus muscles were dissected at four time points, i.e., immediately after the suspension (or heat stress), and 3, 5, and 10 days after the recovery (n=8 per group at each time point). The absolute wet weight and water and protein content of whole soleus muscle in group HS-C were approximately 36, 27, and 8 mg less than CC (p <0.05). Thus, the percentage contribution of water and protein loss to the decrease in muscle weight was 75 and 22%, respectively. Although water content, as well as muscle weight, was elevated within 3 days, the increase of protein was delayed. Heat exposure prior to recovery accelerated the increase in protein content even in the control group. These phenomena were closely associated with 72-kD heat shock protein (HSP72) content. It is suggested that heat stress applied at the end of hindlimb unloading facilitated the recovery of atrophied soleus muscle of rat, through possibly HSP72-related events of protein metabolism. The data also indicated that the combination of heat and mechanical stress evoked larger and long lasting HSP72 response than does heat or mechanical stress alone.

Heat Shock Proteins in Vascular Disease—A Review

INTRODUCTION

There is growing evidence that heat shock proteins (HSPs), a family of stress-inducible proteins may be involved in the pathogenesis of atherosclerotic vascular diseases. Here, we systematically review the evidence behind this notion.

METHODS

A detailed literature search and extensive bibliographic review of literature relating to HSPs and atherosclerotic vascular disease.

RESULTS

Atherosclerotic vascular disease is classified into four main areas of presentation: carotid, coronary, aortic and peripheral vascular disease, for consideration in this review. In each of these vascular diseases, the evidence linking HSPs and atherosclerosis is outlined in a systematic manner. Current evidence suggests that components of the immune system may be involved in the pathogenesis of atherosclerosis, with HSPs acting as auto-antigens in the immune response. HSPs are detected in atherosclerotic lesions and antibodies to HSPs are increased in patients with vascular disease; the rise often correlating with the severity of atherosclerosis. The levels of anti-HSP antibodies have been shown to be independent predictors of risk and have prognostic value.

CONCLUSION

There is a strong link between heat shock protein expression and the principal manifestations of atherosclerotic vascular diseases. A better understanding of this involvement could lead to the development of new and improved treatment strategies.

Human Mpp11 J protein: ribosome-tethered molecular chaperones are ubiquitous

The existence of specialized molecular chaperones that interact directly with ribosomes is well established in microorganisms. Such proteins bind polypeptides exiting the ribosomal tunnel and provide a physical link between translation and protein folding. We report that ribosome-associated molecular chaperones have been maintained throughout eukaryotic evolution, as illustrated by Mpp11, the human ortholog of the yeast ribosome-associated J protein Zuo. When expressed in yeast, Mpp11 partially substituted for Zuo by partnering with the multipurpose Hsp70 Ssa, the homolog of mammalian Hsc70. We propose that in metazoans, ribosome-associated Mpp11 recruits the multifunctional soluble Hsc70 to nascent polypeptide chains as they exit the ribosome.

Intracellular localization of constitutive and inducible heat shock protein 70 in rat liver after in vivo heat stress

The level and intracellular redistribution of the two nucleo-cytoplasmic members of 70 kDa heat shock protein family (constitutive, Hsc70 or Hsp73, and inducible, Hsp72) were studied in rat liver during a 24-h period after exposure of the animals to 41 degrees C whole body hyperthermic stress. The examined proteins were detected in the liver cytosol and nuclei by Western blotting and immunohistochemical staining of paraffin sections, as well as by immnocytochemical staining of isolated nuclear smears. All three techniques applied were based on the use of monoclonal antibodies recognizing both constitutive and inducible Hsp70 isoforms or only the inducible isoform, and gave consistent results. The exposure of the animals to in vivo heat stress was shown to induce the synthesis of otherwise non-existing Hsp72, rendering Hsc70 level unchanged in comparison to unstressed controls. However, immediately after the stress the intracellular redistribution of Hsc70, i.e. its nuclear accumulation, was observed. The maximal level of Hsp70 both in the cytoplasm and in the nuclei was registered 5 h after the stress, which coincided with the maximal level of Hsp72 induction. The alterations in the level and intracellular distribution of examined proteins were still noticeable 24 h after the stress. The results of this study could shed some more light on, as yet uncertain, differences between cellular functions of these two proteins, as well as on the role of the constitutive form under normal and stress conditions.

Long-term alcohol administration inhibits synthesis of both myofibrillar and sarcoplasmic proteins in heart

Alcohol decreases the rate of protein synthesis in cardiac muscle. We investigated the effects of feeding rats a diet containing alcohol for 16 weeks on the myocardial synthesis of myofibrillar and sarcoplasmic (non-myofibrillar) proteins. Alcohol administration decreased the overall rate of protein synthesis in cardiac muscle by 22% compared with controls (P < .05). The rate of synthesis of proteins in the myofibrillar and sarcoplasmic fractions was diminished proportionately after feeding a diet containing alcohol (P < .05). We examined the effects of diminished rates of protein synthesis on the expression of myofibrillar and non-myofibrillar proteins. The cellular content of actin and alpha -myosin heavy chain isoform was significantly reduced and there was an increase in the beta -myosin heavy chain isoform after feeding rats a diet containing alcohol. The reduced expression of myosin heavy chain isoform and actin did not result from a decreased abundance of messenger RNA for either of these proteins. The myocardial content of troponin C and T was unchanged whereas that of troponin I was increased. Ethanol administration reduced the expression of eEF2 and the inducible form of the 70-kDa heat shock protein, whereas the cognate form of the 70-kDa heat shock protein was unaffected in a non-myofibrillar-enriched fraction of cardiac muscle. These results suggest that (1) the reduced protein content observed in the heart after feeding a diet containing alcohol is a consequence of reduced synthesis of both myofibrillar and sarcoplasmic proteins, and (2) the expression of both actin and alpha-myosin heavy chain isoform is affected independently of the messenger RNA content of the proteins. We conclude that translational control mechanisms appear to be important in regulating the expression of myocardial proteins during long-term ethanol intoxication.

Protective Effect ofHeat Shock Proteins 70.1and70.3on Retinal Photic Injury after Systemic Hyperthermia

PURPOSE

This study aimed to determine the relationship between the heat shock protein 70 from hsps70.1 and 70.3 on retinal photic injury after systemic hyperthermia.

METHODS

Eight-week-old female C57BU6 mice were kept at a constant temperature of 41-42 degrees C for 25-30 minutes. After dark-adaptation for 8 hours, intense light of 11000 lux was maintained for 6 hours. Histology and immunohistochemistry for the inducible heat shock protein 70 (hsp70), the constitutive heat shock protein 70 (hsc70), and westem blot analysis, reverse transcriptase-polymerase chain reaction for hsp70.1 and hsp70.3 were performed just before photic injury and after 1, 4, 7, and 14 days.

RESULTS

Light-induced retinal degeneration was prevented by thermotolerance. After hyperthermia, hsp70 was densely expressed in the inner segment of the photoreceptor layer on the photic injury. Hsp70 expression increased for 4 days after photic injury and slowly decreased thereafter. mRNA from hsp70.3 was induced earlier than that of hsp70.1.

CONCLUSIONS

Retinal photic injury was prevented by hyperthermia-induced hsp70. Hsp70 from hsp70.3 may be a rapid and short-lived responder, and that from hsp70.1 is a slower and more sustained responder. Hsp70 from hsp70.3 may be an initial retinal chaperone while hsp70 from hsp70.1 may be a sustained chaperone.

Role of the C-terminal region of mouse inducible Hsp72 in the recognition of peptide substrate for chaperone activity

Here, we produced the C-terminal truncation variants of mouse inducible heat shock protein 72 (Hsp72) to elucidate the regulatory role of the C-terminal helical lid of Hsp70 for substrate recognition. All of the truncation variants containing the substrate binding domain bound a short-length peptide substrate CLLLSAPRR. When a large mass reduced carboxymethyl alpha-lactalbumin (RCMLA) as a substrate was used in gel filtration experiment, we observed the complex formation only for the truncation variants containing the long alpha-helix C in the helical lid. However, RCMLA binding occurred even for the variants lacking alpha-helix C when their C-terminal region was anchored onto a solid phase. Together with the finding that helix C is involved in the self-association of Hsp70, our present data suggest that the C-terminal region of Hsp70 modulates the substrate recognition and its kinetics may be substrate-mass dependent.

Pathways of chaperone-mediated protein folding in the cytosol

Cells are faced with the task of folding thousands of different polypeptides into a wide range of conformations. For many proteins, the folding process requires the action of molecular chaperones. In the cytosol of prokaryotic and eukaryotic cells, molecular chaperones of different structural classes form a network of pathways that can handle substrate polypeptides from the point of initial synthesis on ribosomes to the final stages of folding.

Fluoroalcohol-induced stabilization of the α-helical intermediates of lentil lectin: implication for non-hierarchical lectin folding

An intermediate state of lentil lectin was characterized at pH 1 having low content of secondary as well as tertiary structure. Far- and near-UV CD spectroscopy showed loss of structure when pH was lowered from 7 to 0.8 but the structure loss was less than that of the protein in presence of 6M GndHCl. Intrinsic tryptophan fluorescence studies, ANS binding, and acrylamide quenching experiments supported the existence of the intermediate at low pH. The unfolding process of lentil lectin at pH 1 was also studied by GndHCl denaturation monitored by intrinsic fluorescence spectroscopy. The non-cooperative unfolding at pH 1, in contrast to cooperative unfolding of the native protein further confirmed the presence of loose tertiary structure. The unfolded structure of the lectin at pH 1 was also shown by limited tryptic digestion studies. Further studies were performed on this intermediate state of lentil lectin obtained at low pH in presence of fluoroalcohols 2,2,2-trifluoroethanol (TFE) and 1,1,1,3,3,3-hexafluoroisopropanol (HFIP). Lentil lectin is mainly a beta-sheet protein, and both TFE and HFIP stabilized the acid unfolded structure by inducing alpha-helical contacts. Interestingly, it was observed that induction of the non-native structure resulted in regain of protein activity to some extent. At pH 1, loss in activity was found with both dextran and bromelain while the reported intermediate at the given pH was found to regain activity with bromelain in presence of HFIP and TFE. HFIP induced more structure as compared to TFE and hence a greater regain in activity of about 30% was observed with HFIP as compared to a 15% regain with TFE. Activity with dextran in presence of fluoroalcohols could not be determined as turbidity developed in the corresponding blank preparations. Our results presented here point out the possibility of the formation of a helical structure preceding the formation of the native beta-sheet structure and thus support the non-hierarchical model of protein folding for lentil lectin.

Heat shock protein expression in adenosine triphosphate depleted renal epithelial cells

BACKGROUND

In this study, the putative interactions between apoptosis and heat shock proteins disturbed as a result of ATP depletion were investigated as a hypoxia model.

METHODS

The direct cellular damages were assessed by the release of LDH from the cytoplasm of the human tubular epithelial cells (HK-2 cells) following ATP depletion. The Bcl-2/Bax mRNA expression ratio, used as an index to assess to what extent apoptosis contributed to tubular cell damage, and the expressions of HSP 90, 72 and 27 in relation to the Bcl-2/Bax ratio in the ischemic model, as parameters of their functional contributions to tubule cell damage, were also studied. Heat preconditioning (HS) was performed at 43 degrees C in a temperature-regulated water bath for 1 h.

RESULTS

The release of LDH due to ATP depletion was not significantly increased in HK-2 cells compared to the control, but was slightly increased in heat preconditioned cells compared to non heat preconditioned cells, but the difference was not statistically significant (6.33 +/- 0.57 U/L vs. 8.67 +/- 2.52 U/L, p>0.05). The Bcl-2/ Bax mRNA expression ratio increased progressively from the control to the heat preconditioned and ATP depleted cells (control; 100%, ATP depletion; 154 +/- 6%, heat preconditioning; 212 +/- 6%, heat preconditioning and ATP depletion; 421 +/- 8%). No contribution of heat preconditioning and ATP depletion was observed on the expressions of HSP90 and HSP27. However, HSP72 expression was prominent by ATP depletion, especially after heat preconditioning.

CONCLUSION

There may be a possibility that the preservation of cytolytic damage and an increase in the Bcl-2/Bax mRNA expression ratio is related to the increase of HSP72 in ATP depletion as a hypoxia model.

A field methodology to study effects of UV radiation on fish larvae

There is a considerable lack of in situ specific information about the effects of UV-B radiation on limnic animals studied in the field. We exposed larval pike (Esox lucius L.) in two types of cuvettes (glass and quartz) placed at different depths (5 or 15 cm) to natural solar UV or to artificially enhanced UV-B (lamps on 3 h per day), simulating the scenarios for coming decades. Dose realism and comparability with earlier laboratory experiments was the main purpose, and therefore UV-B irradiances to the surface as well as underwater irradiances were directly measured. Result showed that UV-B dose rates in natural waters are low even though DOC concentration was low (4.8 mg/l) in our study lake. A slight increase in ambient UV-B dose rates was enough to cause neurobehavioral symptoms in pike larvae. However, the dose rates applied were inadequate to affect superoxide dismutase (SOD) or HSP70. While assessing the suggested risks due to increased UV, conclusions emphasize the importance of conducting field UV studies as supplements to laboratory experiments. We also recommend direct measurements of UV-radiation at sites where the target organisms are actually exposed.

The second metal-binding site of 70 kDa heat-shock protein is essential for ADP binding, ATP hydrolysis and ATP synthesis

The chaperone activity of Hsp70 (70 kDa heat-shock protein) in protein folding and its conformational switch, including oligomeric and monomeric interconversion, are regulated by the hydrolysis of ATP and the ATP-ADP exchange cycle. The crystal structure of human ATPase domain shows two metal-binding sites, the first for ATP binding and a second, in close proximity to the first, whose function remains unknown [Sriram, Osipiuk, Freeman, Morimoto and Joachimiak (1997) Structure 5, 403-414]. In this study, we have characterized the second metal-binding motif by site-directed mutagenesis and the kinetics of ATP and ADP binding, and found that the second metal-binding site, comprising a loop co-ordinated by His-227, Glu-231 and Asp-232, participates both in ATP hydrolysis and ATP-synthetic activities, in co-operation with the first metal-binding site. The first metal-binding site, a catalytic centre, is essential for ATP binding and the second site for ADP binding in the reactions of ATP hydrolysis and ATP synthesis.

Expression and Localization of GRP75 in Human Epithelial Tumors and Normal Tissues

Using differential display mRNA techniques, the authors found cDNA of the heat shock 70 protein known as GRP75 overexpressed in ovarian cancer cell lines. In the current study, the authors used immunohistochemistry to characterize the expression pattern of GRP75 in ovarian carcinomas and compared it with epithelial tumors originating from the female reproductive tract, epithelial neoplasms from non-gynecologic sites (colon, pancreas, breast, and lung), and various normal tissues. The authors also developed an antigen capture ELISA assay to determine if GRP75 can be detected in tumors, ascites, or sera of patients with advanced mullerian adenocarcinomas. All epithelial tumors from the ovary and the female reproductive tract were positive for GRP75 expression with moderate to strong staining intensity; stromal expression of GRP75 was generally weak or absent. Adenocarcinomas from the colon, lung, pancreas, and breast also stained strongly positive for GRP75. The epithelial cells of all normal tissues examined were positive for GRP75, and strong staining was also seen in the corpora lutea, hepatocytes, enteric neural plexus of the esophagus and colon, and placental cytotrophoblast and syncytiotrophoblast, and in subpopulations of pancreatic acinar cells. The ELISA assay detected GRP75 in tumor lysates and ascitic fluid, but not sera, of patients with mullerian adenocarcinomas. The authors conclude that GRP75 is highly expressed in both benign and malignant epithelium, as well as cells of specialized function from a variety of tissues.

Protective role of heat stress in burn trauma*

OBJECTIVE

This study was designed to determine whether cutaneous burn injury up-regulated expression of myocardial heat shock protein (HSP)70 and to determine a potential cardioprotective role of inducible HSP70 (iHSP70) in postburn myocardial contractile function.

DESIGN

Experimental study.

SETTING

Research laboratory.

SUBJECTS

Adult Hartley guinea pigs.

INTERVENTIONS

The first set of studies determined whether heat stress (increasing body temperature to 42 degrees C for 20 mins) in adult Hartley guinea pigs would increase expression of myocardial iHSP70.

MEASUREMENTS AND MAIN RESULTS

Our model of heat stress increased expression of inducible HSP in the myocardium (Western blot), and this response persisted 1, 2, 4, and 24 hrs after the initial heat stress. We then determined whether burn trauma over 40% total body surface area (TBSA) increased myocardial expression of iHSP70. Time-matched sham and burned guinea pigs were killed 1, 2, 4, 12, 18, or 24 hrs postburn, and hearts were used either to examine myocardial iHSP70 expression by Western blot or to determine myocardial contractile function (Langendorff). Burn trauma produced a two-fold increase in myocardial iHSP70 that was evident as early as 1 hr postburn and persisted 24 hrs postburn; increased iHSP70 expression occurred despite only a modest and transient increase in body temperature after burn trauma. We then determined whether heat shock stress before burn trauma provided a protective or detrimental effect on cardiac function. Body temperature was increased to 42 degrees C for 20 mins, animals were allowed to recover, and body temperature returned to baseline; burn trauma was then produced (40% TBSA) either 1, 2, 4, or 24 hrs after the initial heat stress. Myocardial contraction and relaxation deficits were evident after burn trauma alone; however, heat stress 1 hr before burn trauma improved left ventricular developed pressure and positive or negative maximum change in pressure in time and shifted left ventricular function curves upward and leftward from those calculated for burn in the absence of heat stress, indicating improved ventricular performance. Increasing the time between the initial heat stress and burn injury decreased the cardioprotective effects of heat stress. Thus, organ protection was evident only when the time period between the initial heat stress and the second insult was brief (1 hr).

CONCLUSIONS

Our finding that the amount of myocardial iHSP70 remained constantly elevated after heat stress while the cardio-protective effect afforded by a prior heat stress declined with time suggested that the initial heat stress evoked several compensatory/adaptive mechanisms that may include modulation of autonomic nervous system responses, changes in metabolic function, modulation of pro/anti-inflammatory cytokine responses, and heat stress-related alterations in antioxidant capacity.

Preferential substrate binding orientation by the molecular chaperone HscA

HscA, a specialized bacterial hsp70-class chaperone, interacts with the iron-sulfur cluster assembly protein IscU by recognizing a conserved LPPVK sequence motif at positions 99-103. We have used a site-directed fluorescence labeling and quenching strategy to determine whether HscA binds to IscU in a preferred orientation. HscA was selectively labeled on opposite sides of the substrate binding domain with the fluorescent probe bimane, and the ability of LPPVK-containing peptides having tryptophan at the N or C terminus to quench bimane fluorescence was measured. Quenching was highly dependent on the position of tryptophan in the peptide and the location of bimane on HscA implying a strong directional preference for peptide binding. Similar experiments showed that full-length IscU binds in the same orientation as IscU-derived peptides and that binding orientation is unaffected by the co-chaperone HscB. The preferred orientation of the HscA-IscU complex is the reverse of that previously described for peptide complexes of Escherichia coli DnaK and rat Hsc70 substrate binding domain fragments establishing that hsp70 isoforms can bind peptide/polypeptide substrates in different orientations.

HSP70 interacts with ribosomal subunits of thermotolerant cells

The expression of heat shock or stress proteins (hsps) is a widespread response to stress that results in the protection of cells from subsequent insults, coined stress tolerance. Stress tolerance is apparently due to the preservation of several cellular structures and processes, such as translation. Protection of protein synthesis has been correlated with the presence of Hsp70. In the present study, Hsp70 was found to interact with translating ribosomes. This interaction is due to the preferential binding of Hsp70 to the 40S ribosomal subunit. Additionally, Hsp70 seems to interact weakly with nascent polypeptides within the 60S subunit. The interaction between Hsp70 and ribosomal subunits could also be observed in vitro conditions. Binding of Hsp70 to ribosomes was salt resistant, suggesting that this protein is not bound to transiently associated translational factors. Moreover, protection of protein synthesis requires new gene expression. We speculate that the binding of Hsp70 to ribosomes is part of a mechanism to guarantee the rapid and abundant protein synthesis during stress, particularly the translation of mRNAs encoding for hsps.

High sensitivity of northern pike larvae to UV-B but no UV-photoinduced toxicity of retene

In order to investigate whether increased UV-B radiation is a risk factor, a series of acute laboratory experiments was conducted with larval stages of the northern pike (Esox lucius L.), hatching in Nordic waters in May. Further, a comparative investigation on the acute phototoxicity of retene (7-isopropyl-1-methylphenanthrene), a PAH compound recently revealed to posses UV-B-induced phototoxicity in larval coregonids, was conducted with pike larvae. In semi-static experiment, larvae were pre-exposed to retene (3, 9, 30 and 82 microg/g), with relevant controls, for 24 h and then irradiated for 3 h once a day (two consecutive days) with three UV-B doses (CIE-weighted 1.0, 1.8 or 2.7 kJ/m2 per day) or with visible light only. In 3 days, the UV-B exposure alone increased mortality by 10-20% in all applied dose rates. Retene (up to 82 microg/l) had no direct UV-B-induced toxicity in pike. However, pike larvae were very sensitive to UV-B even in low doses, indicated as severe neurobehavioral disorders. Monitoring of pike with the neurobehavioral syndrome revealed substantial late mortality. As UV-B had no influence on CYP1A content in larval pike, retene (9-82 microg/l) induced this protein substantially with and without UV-B. In pike, the applied UV-B radiation and water retene alone both decreased HSP70 concentrations. Neither UV nor retene changed SOD activity significantly. Overall, data on pike suggest that only a minor increase in ambient UV-B coming to the earth's surface may cause lethal effects to larval fish.

Induction, modification and accumulation of HSP70s in the rat liver after acute exercise: early and late responses

Liver cells synthesize HSP72, the cytosolic highly stress-inducible member of the 70 kDa family of heat-shock proteins (HSP70s), in response to acute exercise. This study was aimed at obtaining further insight into the physiological relevance of the hepatic stress response to exercise by investigating the induction and long-term maintenance of increased levels of HSP70s of the HSP and glucose-regulated protein (GRP) families, their post-translational modifications during or after exercise and the possible relation of HSP induction to oxidative stress. In a running rat model, acute exercise activated the synthesis and accumulation of HSP72, GRP75 and GRP78 in liver cells, pointing towards a multifactorial origin of this response. A peak HSP72 accumulation was observed shortly after exercise as a result of transcriptional activation. HSP72 was reduced shortly after exercise preceding the disappearance of its mRNA. Two further waves of HSP72 accumulation peaked 8 and 48 h after exercise without transcriptional activation. A transient increase in the proportion of acidic variants of HSP72 and HSP73 was also observed shortly after exercise as a result, at least in part, of protein phosphorylation. Free and protein-bound lipid peroxidation derivatives (TBARS) showed a tendency to increase in the early post-exercise and the free-to-protein-bound TBARS ratio decreased significantly after 2 h. During the early post-exercise period, protein-bound TBARS correlated positively with HSP72 and 73, but not with GRP75 or GRP78. Altogether, the reported results indicate that the early induction and post-translational modification of HSP70s in liver cells following exercise is a preliminary step of a series of long-lasting HSP70-related events, possibly designed to preserve liver cell homeostasis and to help provide a concerted response of the whole organism to physical stress.

The 1.8-A resolution crystal structure of YDR533Cp from Saccharomyces cerevisiae: a member of the DJ-1/ThiJ/PfpI superfamily

The yeast gene YDR533C encodes a protein belonging to the DJ-1/ThiJ/PfpI superfamily. This family includes the human protein DJ-1, which is mutated in autosomal recessive early-onset Parkinson's disease. The function of DJ-1 and its yeast homologue YDR533Cp is unknown. We report here the crystal structure of YDR533Cp at 1.8-A resolution. The structure indicates that the closest relative to YDR533Cp is the Escherichia coli heat shock protein Hsp31 (YedU), which has both chaperone and protease activity. As expected, the overall fold of the core domain of YDR533Cp is also similar to that of DJ-1 and the bacterial protease PfpI. YDR533Cp contains a possible catalytic triad analogous to that of Hsp31 and an additional domain that is present in Hsp31 but is not seen in DJ-1 and other members of the family. The cysteine in this triad (Cys-138) is oxidized in this crystal structure, similar to modifications seen in the corresponding cysteine in the crystal structure of DJ-1. YDR533Cp appears to be a dimer both in solution and the crystal, but this dimer is formed by a different interface than that found in Hsp31 or other members of the superfamily.

Hsp70 and Hsp90--a relay team for protein folding

Molecular chaperones are a functionally defined set of proteins which assist the structure formation of proteins in vivo. Without certain protective mechanisms, such as binding nascent polypeptide chains by molecular chaperones, cellular protein concentrations would lead to misfolding and aggregation. In the mammalian system, the molecular chaperones Hsp70 and Hsp90 are involved in the folding and maturation of key regulatory proteins, like steroid hormone receptors, transcription factors, and kinases, some of which are involved in cancer progression. Hsp70 and Hsp90 form a multichaperone complex, in which both are connected by a third protein called Hop. The connection of and the interplay between the two chaperone machineries is of crucial importance for cell viability. This review provides a detailed view of the Hsp70 and Hsp90 machineries, their cofactors and their mode of regulation. It summarizes the current knowledge in the field, including the ATP-dependent regulation of the Hsp70/Hsp90 multichaperone cycle and elucidates the complex interplay and their synergistic interaction.

Heat-Stress Enhances Proliferative Potential in Rat Soleus Muscle

The effects of heat-stress on proliferative potential in vivo were studied in rat skeletal muscle. Male Wistar rats (7-weeks-old) were divided into two groups: control (n=24) and heat-stressed (n=24). Rats in the experimental group were exposed to environmental heat-stress (41 degrees C for 60 min) in a heat chamber without anesthesia. The soleus muscles were dissected 1, 7, and 14 days after the heat exposure. The wet and dry weights of soleus muscle relative to body weight in the heat-stressed group were significantly higher than controls 7 days after the exposure (10.1% and 17.5%, respectively, p <0.05). The distribution of 5-bromo-2'-deoxyuridine and proliferating cell nuclear antigen-positive nuclei, that are the indicators for the cell proliferation, were increased by 2.2 and 5.1 times, respectively 1 day after heating (p <0.05). The expressions of heat shock protein 72 (58.0%) and phosphorylated p70S6 kinase (52.3%) were increased 1 day following heat exposure (p <0.05). These results suggest that heat-stress could promote the cell proliferation and induce muscular hypertrophy.

TRiC/CCT cooperates with different upstream chaperones in the folding of distinct protein classes

The role in protein folding of the eukaryotic chaperonin TRiC/CCT is only partially understood. Here, we show that a group of WD40 beta-propeller proteins in the yeast cytosol interact transiently with TRiC upon synthesis and require the chaperonin to reach their native state. TRiC cooperates in the folding of these proteins with the ribosome-associated heat shock protein (Hsp)70 chaperones Ssb1/2p. In contrast, newly synthesized actin and tubulins, the major known client proteins of TRiC, are independent of Ssb1/2p and instead use the co-chaperone GimC/prefoldin for efficient transfer to the chaperonin. GimC can replace Ssb1/2p in the folding of WD40 substrates such as Cdc55p, but combined deletion of SSB and GIM genes results in loss of viability. These findings expand the substrate range of the eukaryotic chaperonin by a structurally defined class of proteins and demonstrate an essential role for upstream chaperones in TRiC-assisted folding.

Heat shock protein 70 binding inhibits the nuclear import of apoptosis-inducing factor

Heat shock protein 70 (HSP70) can inhibit apoptosis by neutralizing and interacting with apoptosis-inducing factor (AIF), a mitochondrial flavoprotein that translocates upon apoptosis induction to the nucleus, via the cytosol. Here, we show that only members of the HSP70 family interact with AIF. Systematic deletion mapping revealed the existence of three distinct functional regions in the AIF protein: (1) a region between amino acids 150 and 228 that binds HSP70, (2) a domain between residues 367 and 459 that includes a nuclear localization sequence (NLS) and (3) a C-terminal domain beyond residue 567 required for its chromatin-condensing activity. Deletion of the 150-268 domain completely abolished HSP70 binding and facilitated the nuclear import of AIF, resulting in a gain-of-function phenotype with enhanced AIF-mediated chromatin condensation as compared to wild-type AIF. This gain-of-function phenotype was observed in wild-type control cells (which express low but significant levels of HSP70), yet was lost when AIFDelta150-268 was introduced into HSP70 knockout cells, underscoring the functional importance of the AIF-HSP70 interaction. Altogether, our data demonstrate that AIF inhibition by HSP70 involves cytosolic retention of AIF. Moreover, it appears that endogenous HSP70 protein levels are sufficiently elevated to modulate the lethal action of AIF.

Gene Expression Profile Changes Are Commonly Modulated across Models and Species after Traumatic Brain Injury

Brain trauma is a major cause of morbidity and mortality, both in adult and pediatric populations. Much of the functional deficit derives from delayed cell death resulting from induction of neurotoxic factors that overwhelm endogenous neuroprotective responses. To identify the potential molecular mechanisms underlying such delayed responses, we compared gene expression patterns using high-density oligonucleotide arrays at 4, 8, 24, and 72 h after moderate levels of lateral fluid percussion-induced brain injury in rats and lateral controlled cortical impact injury in mice (a total of 47 profiles). Expression of 82 genes in 12 functional categories was significantly changed in both species after trauma. The largest number of gene expression changes were found in the functional groups related to inflammation (17%), transcription regulation (16%), and cell adhesion/extracellular matrix (15%). Fifty percent of genes similarly altered across models had not been previously implicated in traumatic brain injury. Of particular interest were expression changes in genes linked to neurodegeneration, such as ATF3 and lysosomal membrane glycoprotein 2, and to neuroprotection including lipocortin 1, calponin 3, gelsolin, Id-1, and p45 NF-E2. Gene expression profiling across species and models may help identify candidate molecular pathways induced by brain injury, some of which may provide novel targets for therapeutic intervention.

Expression of heat shock protein 70 induced by 4-aminopyridine through glutamate-mediated excitotoxic stress in rat hippocampus in vivo

The intrahippocampal administration of 4-aminopyridine (4-AP) induces epileptic seizures and neurodegeneration, due probably to stimulation of glutamate release from synaptic terminals. We have studied the time course of the neurodegenerative changes produced by 4-AP, perfused through microdialysis cannulas in rat hippocampus, and correlated them with the expression of the inducible heat shock protein 70 (HSP70), detected immunocytochemically. Electroencephalographic seizure activity appeared immediately after the beginning of 4-AP perfusion. The first signs of histological neuronal damage were observed in CA1 and CA3 subfields of the perfused hippocampus 3 h after treatment and progressed until reaching a maximal neuronal loss at 24 h. In 4-AP-treated rats HSP70 was expressed mainly in neurons of the contralateral hippocampus, with a time course and cellular distribution very similar to the neurodegeneration observed in the perfused hippocampus, but no neuronal damage was observed. The N-methyl-D-aspartate (NMDA) receptor antagonists MK-801 and (3-phosphonopropyl)-piperazine-2-carboxylic acid prevented the seizures, the neurodegeneration and the expression of HSP70. These data demonstrate that the 4-AP-induced release of endogenous glutamate overactivates NMDA receptors in the perfused hippocampus and that the resulting neuronal hyperexcitability propagates to the contralateral hippocampus, generating a glutamate-mediated neuronal stress sufficient to induce the expression of HSP70 but not to produce neurodegeneration. These findings provide a useful model for investigating the relationships between neuronal hyperexcitation, neurodegeneration and the role of HSP expression.

Role of substrate on larval development of the freshwater teleostPelvicachromis pulcher

It is known that, in an aquatic environment, the mineralogical composition of the substrate can affect the structure of settled communities. In marine environments, the presence of quartz negatively influences the formation of biofilm, as well as the selection and the colonization of the substrate by benthic organisms. Direct laboratory observation revealed that the freshwater teleost Pelivicachromis pulcher selects, when available, nonquartzitic brooding substrate. To monitor the effects of substrate on larvae development, ten lots of embryos were distributed in grid nurseries; carbonatic gravel was laid in five of the nurseries, while freshly fractured quartz gravel was used in the remaining ones. All the embryos laid in the two nurseries hatched, and 90% of the carbonate developing larvae reached adulthood, while 100% of those reared on quartz grain died 120 hr post hatching. Examination was made, both in larvae developed on carbonatic substrates and in those developed on quartz substrates, of the expression of the fetal growth factor, the insulin growth factor-II (IGF-II), of the molecular chaperone, the heat shock protein 70 (HSP70), which is involved in the folding of the nascent polypeptide chain, of the key enzyme of the glycolytic pathway, the glyceraldehyde-3-phosphate dehydrogenase (GADPH), and of the housekeeping gene, the beta-actin. All the data were normalized against 18S RNA expression. In larvae reared on quartz substrate, the genes IGF-II and the beta-actin showed a lower expression, while the GADPH was totally suppressed and the expression of HSP70 increased. In conclusion, the data presented in this article demonstrated, for the first time, that the presence of quarzitic substrates is sufficient to stop larvae development through the inhibition of gene transcription in this African cichlid, leading to its death.

HSP70-2 (HSPA1B) is associated with noncognitive symptoms in late-onset Alzheimer's disease

Neuropsychiatric manifestations are common in Alzheimer's disease (AD) and their phenotypic expression might be related to physiopathological and genetic causes. Multiple studies have implicated oxidative stress to the pathogenesis and possible etiology of AD. One of the mechanisms to protect cells from oxidative stress is the expression of heat-shock proteins (HSP). HSPA1B (alternatively known as HSP70-2) has been related to AD pathophysiology. In the present analysis, 77 AD patients were classified according to their cognitive status with the Neuropsychiatric Inventory and were genotyped for an insertion/deletion (A1/A2) polymorphism. The A2 allele conferred a significant increase of psychiatric morbidity in an allele-dose manner (P < .05). This pattern can be attributed to all AD stages and the severity of the behavioral disturbances was higher for those patients carrying one or two A2 alleles. These results indicate a possible association between the A2 allele and an overexpression of noncognitive symptoms in AD.

Clinically applicable thermal preconditioning attenuates leukocyte-endothelial interactions

BACKGROUND

We have previously demonstrated that clinically applicable thermal preconditioning induces heat shock protein 72 (HSP72) and protects against a subsequent ischemia-reperfusion (I/R) injury in an animal model. A core component of I/R injuries is the interaction between activated leukocytes and endothelial cells. We hypothesized that the effects of clinically applicable thermal preconditioning are mediated through attenuation of this leukocyte-endothelial (L-E) interaction.

STUDY DESIGN

Twenty-one male Sprague Dawley rats were divided into control, I/R, and preconditioning plus I/R groups. Preconditioning was done under general anesthesia and the animals' temperature raised by 1 degrees C for 15 minutes in a water bath. This was repeated once a day for 5 successive days. I/R injury was caused by occlusion of the superior mesenteric artery for 10 minutes followed by 1 hour of reperfusion. L-E interactions were analyzed using intravital microscopy of a mesenteric vessel in vivo. L-E interactions were determined using leukocyte velocity (which decreases as cells interact), and number of adherent and migrated leukocytes. HSP72 was assessed by Western blot.

RESULTS

Ischemia-reperfusion caused a decrease in leukocyte rolling velocity at all timepoints (p < 0.05 versus controls). Preconditioning attenuated the effects of I/R, and leukocyte rolling velocity was significantly improved versus I/R (p < 0.05) to levels similar to those in controls. Similarly, the number of adherent and migrating leukocytes increased significantly (p < 0.05) after I/R versus control at all time points, and preconditioning attenuated these to control levels, (p < 0.05 versus I/R) at both the 30- and 60-minute postischemia time points. Upregulation of HSP72 was demonstrated on Western blot.

CONCLUSIONS

These results demonstrate that the benefit of clinically applicable thermal preconditioning is at least partially because of an immunomodulatory role in attenuating leukocyte-endothelial interactions associated with an increased expression of HSP 72.

Overexpression of the cochaperone CHIP enhances Hsp70-dependent folding activity in mammalian cells

CHIP is a cochaperone of Hsp70 that inhibits Hsp70-dependent refolding in vitro. However, the effect of altered expression of CHIP on the fate of unfolded proteins in mammalian cells has not been determined. Surprisingly, we found that overexpression of CHIP in fibroblasts increased the refolding of proteins after thermal denaturation. This effect was insensitive to geldanamycin, an Hsp90 inhibitor, and required the tetratricopeptide repeat motifs but not the U-box domain of CHIP. Inhibition of Hsp70 chaperone activity abolished the effects of CHIP on protein folding, indicating that the CHIP-mediated events were Hsp70 dependent. Hsp40 competitively inhibited the CHIP-dependent refolding, which is consistent with in vitro data indicating that these cofactors act on Hsp70 in the ATP-bound state and have opposing effects on Hsp70 ATPase activity. Consistent with these observations, CHIP overexpression did not alter protein folding in the setting of ATP depletion, when Hsp70 is in the ADP-bound state. Concomitant with its effects on refolding heat-denatured substrates, CHIP increased the fraction of nascent chains coimmunoprecipitating with Hsc70, but only when sufficient ATP was present to allow Hsp70 to cycle rapidly. Our data suggest that, consistent with in vitro studies, CHIP attenuates the Hsp70 cycle in living cells. The impact of this effect on the fate of unfolded proteins in cells, however, is different from what might be expected from the in vitro data. Rather than resulting in inhibited refolding, CHIP increases the folding capacity of Hsp70 in eukaryotic cells.

Heat shock proteins, cellular chaperones that modulate mitochondrial cell death pathways

Stress or heat shock proteins (HSPs) are ubiquitous and highly conserved proteins whose expression is induced in response to a wide variety of physiological and environmental insults. They allow the cells to survive to otherwise lethal conditions. Various mechanisms have been proposed to account for the cytoprotective functions of HSPs. These proteins play an essential role in intracellular "house-keeping" by assisting the correct folding of nascent and stress-accumulated misfolded proteins and preventing their aggregation. Several HSPs have also demonstrated to directly interact with various components of the tightly regulated programmed cell death machinery, upstream, and downstream of the mitochondrial events. Finally, HSPs could play a role in the proteasome-mediated degradation of selected proteins under stress conditions. Altogether, these properties could make HSPs appropriate targets for modulating cell death pathways.

Ribosome-tethered molecular chaperones: the first line of defense against protein misfolding?

Folding of many cellular proteins is facilitated by molecular chaperones. Analysis of both prokaryotic and lower eukaryotic model systems has revealed the presence of ribosome-associated molecular chaperones, thought to be the first line of defense against protein aggregation as translating polypeptides emerge from the ribosome. However, structurally unrelated chaperones have evolved to carry out these functions in different microbes. In the yeast Saccharomyces cerevisiae, an unusual complex of Hsp70 and J-type chaperones associates with ribosome-bound nascent chains, whereas in Escherichia coli the ribosome-associated peptidyl-prolyl-cis-trans isomerase, trigger factor, plays a predominant role.

Sensitization of thermotolerant SCK cells to hyperthermia and freezing with reduction of intracellular pH: implications for cryosurgery

BACKGROUND AND OBJECTIVES

During cryosurgery, cells frozen slowly at the outer part of the ice ball undergo severe dehydration and are subject to solute effects injury, which may be caused in part by protein denaturation. This study was undertaken to determine whether heat shock proteins (HSPs), the molecular chaperones that stabilize proteins against denaturation, have a protective effect on cells during slow freezing. In addition, we aimed to determine whether acidic conditions, similar to those found in many solid tumors, would effect this protection.

METHODS

SCK cells were frozen at 5 degrees C/min to -10 degrees C or -20 degrees C before or after induction of thermotolerance, and at neutral or low pH conditions. Lethal damage was determined by clonogenics.

RESULTS

Clonogenic survival was decreased by 50% in thermotolerant cells frozen to -10 degrees C after culture in acidic conditions (pH 6.6) compared with non-thermotolerant cells cultured at neutral pH. Induction of thermotolerance alone or low pH alone did not significantly sensitize SCK cells to freezing. All treatment groups were equally susceptible to killing when frozen to -20 degrees C.

CONCLUSIONS

Our results show that induction of thermal tolerance does not protect SCK cells against subsequent freezing injury and that a low pH environment actually sensitizes these cells to freeze injury.

Determination of intracellular heat shock protein 70 using a newly developed cell lysate immunometric assay

Heat shock proteins (Hsp) have been associated to several clinical relevant conditions. Currently used methods to determine Hsp 70 possess certain drawbacks. Therefore, we developed a cell lysate immunometric assay (CLIA) for the quantification of intracellular Hsp 70. This CLIA uses a combination of two distinct monoclonal antibodies that recognize different epitopes on the Hsp 70 molecule. A recombinant human Hsp 70 was used as the standard material. The detection range of the CLIA was 4-4000 ng/ml. The intra- and interassay coefficients of variation were, on average, 5% and 12%, respectively. The recovery varied between 81% and 116%. The Hsp 70 levels assayed after serial dilution of cell lysates varied linearly with dilution (between 97% and 120%). The reliability of the CLIA was assessed by comparison with the values determined by flow cytometric procedure; these two sets of values showed a highly significant correlation (r=0.896, p<0.0001), indicating that the two methods are comparable. We conclude that this assay represents a low-cost alternative of the flow cytometric technique.