Expression of hsp 90 in the human kidney and in proximal tubule cells exposed to heat, sodium arsenite and cadmium chloride

Bio-indicators in cadmium toxicity: Role of HSP27 and HSP70

Heat shock proteins (HSPs) are a family of proteins that are expressed by cells in reply to stressors. The changes in concentration of HSPs could be utilized as a bio-indicator of oxidative stress caused by heavy metal. Exposure to the different heavy metals may induce or reduce the expression of different HSPs. The exposure to cadmium ion (Cd²⁺) could increase HSP70 and HSP27 over 2- to 10-fold or even more. The in vitro and in vivo models indicate that the HSP70 family is more sensitive to Cd intoxication than other HSPs. The analyses of other HSPs along with HSP70, especially HSP27, could also be useful to obtain more accurate results. In this regard, this review focuses on examining the literature to bold the futuristic uses of HSPs as bio-indicators in the initial assessment of Cd exposure risks in defined environments.

Identification of co-chaperone Cdc37 in Penaeus monodon: coordination with Hsp90 can reduce cadmium stress-induced lipid peroxidation

Cell division cycle 37 (Cdc37) is an important cytoplasmic phosphoprotein, which usually functions as a complex with heat shock protein 90 (Hsp90), to effectively reduce the damage caused by heavy metals, such as cadmium (Cd), in aquatic animals. The high toxicity of Cd in aquatic systems generally has a deleterious effect on healthy farming of shrimps. In the present study, a novel Cdc37 gene from Penaeus monodon was identified and designated as PmCdc37. Following exposure to Cd stress, the expression levels of PmCdc37 were upregulated at the transcriptional level in both the hepatopancreas and hemolymph. RNA interference and recombinant protein injection experiments were carried out to determine the function of PmCdc37 in P. monodon following Cd exposure. To clarify the correlations between PmCdc37 and PmHsp90, the respective recombinant proteins were expressed in vitro, and the ATPase activity of PmHsp90, with or without PmCdc37, was assessed. Moreover, a pull-down assay was conducted to detect the correlation between PmCdc37 and PmHsp90. After analyzing the expression patterns of PmHsp90 following Cd challenge, whether PmHsp90 can promote the ability of PmCdc37 to resist Cd stress or not was investigated. The results showed that formation of a PmHsp90/PmCdc37 complex protected shrimp against Cd stress-induced damage. Moreover, we also confirmed that PmSOD is involved in Cd stress, and that the PmHsp90/PmCdc37 complex can regulate SOD enzymatic activity. PmSOD was involved in decreasing the MDA content in shrimp hemolymph caused by Cd stress. We concluded that during exposure to Cd, the PmHsp90/PmCdc37 complex increases SOD enzyme activity, and in turn decreases the MDA content, thereby protecting shrimp against the damage caused by Cd stress. The present studies contribute to understanding the molecular mechanism underlying resistance to Cd stress in shrimp.

Intrauterine Exposure to Cadmium Reduces HIF-1 DNA-Binding Ability in Rat Fetal Kidneys

During embryonic development, some hypoxia occurs due to incipient vascularization. Under hypoxic conditions, gene expression is mainly controlled by hypoxia-inducible factor 1 (HIF-1). The activity of this transcription factor can be altered by the exposure to a variety of compounds; among them is cadmium (Cd), a nephrotoxic heavy metal capable of crossing the placenta and reaching fetal kidneys. The goal of the study was to determine Cd effects on HIF-1 on embryonic kidneys. Pregnant Wistar rats were exposed to a mist of isotonic saline solution or CdCl₂ (D_Del = 1.48 mg Cd/kg/day), from gestational day (GD) 8 to 20. Embryonic kidneys were obtained on GD 21 for RNA and protein extraction. Results show that Cd exposure had no effect on HIF-1α and prolyl hydroxylase 2 protein levels, but it reduced HIF-1 DNA-binding ability, which was confirmed by a decrease in vascular endothelial growth factor (VEGF) mRNA levels. In contrast, the protein levels of VEGF were not changed, which suggests the activation of additional regulatory mechanisms of VEGF protein expression to ensure proper kidney development. In conclusion, Cd exposure decreases HIF-1-binding activity, posing a risk on renal fetal development.

Receptor-interacting protein 140 as a co-repressor of Heat Shock Factor 1 regulates neuronal stress response

Heat shock response (HSR) is a highly conserved transcriptional program that protects organisms against various stressful conditions. However, the molecular mechanisms modulating HSR, especially the suppression of HSR, is poorly understood. Here, we found that RIP140, a wide-spectrum cofactor of nuclear hormone receptors, acts as a co-repressor of heat shock factor 1 (HSF1) to suppress HSR in healthy neurons. When neurons are stressed such as by heat shock or sodium arsenite (As), cells engage specific proteosome-mediated degradation to reduce RIP140 level, thereby relieving the suppression and activating HSR. RIP140 degradation requires specific Tyr-phosphorylation by Syk that is activated in stressful conditions. Lowering RIP140 level protects hippocampal neurons from As stress, significantly it increases neuron survival and improves spine density. Reducing hippocampal RIP140 in the mouse rescues chronic As-induced spatial learning deficits. This is the first study elucidating RIP140-mediated suppression of HSF1-activated HSR in neurons and brain. Importantly, degradation of RIP140 in stressed neurons relieves this suppression, allowing neurons to efficiently and timely engage HSR programs and recover. Therefore, stimulating RIP140 degradation to activate anti-stress program provides a potential preventive or therapeutic strategy for neurodegeneration diseases.

Thermal stress in Danio rerio: a link between temperature, light, thermo-TRP channels, and clock genes

It is believed that the biological systems perceiving temperature and light daily cycles were subjected to the simultaneous selective pressures, which resulted in their co-evolutionary association. We investigated the influence of 1h 33°C heat shock on the expression of clock and heat shock protein genes, as well as the role of the thermo-TRP channel, TRPV1, in ZEM-2S cells of the teleost Danio rerio, in constant dark (DD) or light-dark cycles (LD). After heat shock, we observed an acute increase of hsp90 aa1 levels in both DD and LD conditions. Interestingly, the expression of hsp90 aa1 was two-fold lower in LD than in DD, what suggests an antagonistic effect of white light on heat shock action. Regarding clock genes, no effect was found in cells subjected to the heat shock in DD. When cells were kept in LD, the expression of per1, per2, cry1a, and cry1b increased in response to heat shock, indicating that heat shock only affects clock core of LD-synchronized ZEM-2S cells. We then evaluated whether TRPV1 played a role in heat-mediated hsp90 aa1 and per2 responses: hsp90 aa1 increase was unaffected whereas per2 increase was partially blocked by TRPV1 inhibitor, demonstrating the channel participation in clock gene regulation by heat shock. Taken together, our results open a novel investigative perspective regarding the relationship between temperature and clock genes, placing a new player in the regulation of this phenomenon: the TRPV1 channel.

Immune response of the bay scallop, Argopecten irradians, after exposure to the algicide palmitoleic acid

Palmitoleic acid (PA) is an effective algicide against the toxin-producing dinoflagellate Alexandrium tamarense; however, its effects on the immune system of the edible bay scallop Argopecten irradians are unclear. Therefore, we investigated the effects of PA on the immune response in A. irradians by assessing total haemocyte counts (THC), alkaline phosphatase activity (ALP), nitrite oxide (NO), glutathione (GSH), and lactate dehydrogenase (LDH) levels, as well as the expression of immune-related genes (FREP, PGRP, HSP90, MnSOD, and Cu/ZnSOD) at various hours post-exposure (hpe) to the compound. THC decreased in PA-treated groups, whereas ALP increased significantly in all of the PA treatment groups at 3 hpe, after which it significantly decreased. The LDH and NO levels were significantly enhanced in the high and medium concentration group. Notably, the GSH level increased in all PA treatment groups at each time interval. Our study revealed that after treatment with different concentrations of PA, variable effects on the expression of genes involved in the immune system response were observed. The results of our study demonstrate that immersing scallops in PA at effective concentrations could result in differential effects on immune system responses and expression of immune-related genes. Specifically, PA may disrupt the endocrine system or affect signal transduction pathways in the scallops. Therefore, the present study highlights the potential risk of using the PA as an algicide to control algal bloom outbreaks in the marine environment.

Short-term cadmium exposure induces stress responses in frog (Pelophylax bergeri) skin organ culture

There have been a few studies on the negative effects of pollutants on amphibian skin, the first structural barrier that interacts with the environment and its potential contaminants. In this study an ex vivo skin organ culture from the amphibian Pelophylax bergeri was used to evaluate cell stress responses induced by short-term exposure to cadmium (Cd), a toxic heavy metal known to be an environmental hazard to both humans and wildlife. Histopathological studies were carried out on skin explants using light microscopy and changes in the expression of stress proteins, such as Metallothionein (MT) and Heat shock proteins (HSPs), were investigated by Real-time RT-PCR. Results revealed that amphibian skin reacts to Cd-induced stress by activating biological responses such as morphological alterations and dose- and time-dependent induction of Mt and Hsp70 mRNA expression, suggesting their potential role as biomarkers of exposure to Cd. This work provides a basis for a better understanding of the tissue-specific responses of amphibian skin as a target organ to Cd exposure and its in vitro use for testing potentially harmful substances present in the environment.

Molecular characterization of heat-shock protein 90 gene and its expression in Gobiocypris rarus juveniles exposed to pentachlorophenol

Heat-shock protein 90 (HSP90) is an abundant and highly conserved molecular chaperone, and it fulfills a housekeeping function in contributing to the folding, maintenance of structural integrity, and proper regulation of a subset of cytosolic proteins. In this study, the full-length 2693-bp cDNA of HSP90 was cloned by rapid amplification of cDNA ends (RACE) technique from the liver of rare minnow (Gobiocypris rarus) for the first time, designated as GrHSP90. The complete coding sequence of GrHSP90 is 2181 bp in length, which encodes a polypeptide of 726 amino acids with a predicted molecular mass of 83.4 kDa and a theoretical isoelectric point of 4.90. Phylogenetic tree analysis indicated that deduced protein GrHSP90 had extensive sequence similarities to other fish HSP90s. Tissue distribution showed that GrHSP90 was constitutively expressed in a wide range of tissues including gill, blood, brain, fin, gonad, heart, intestine, kidney, liver, muscle, spleen, skin, and swim bladder. The highest expression was found in the gonad. Furthermore, significant increase in GrHSP90 mRNA in the liver was observed after exposure to pentachlorophenol ≥8 µg/L (p < 0.05). Our results suggest that GrHSP90 is indeed an ortholog of the HSP90 family and may be act as a biomarker to assess the effect of environmental contaminant.

Middle domain of human Hsp90 isoforms differentially binds Aha1 in human cells and alters Hsp90 activity in yeast

Hsp90 is an essential chaperone for more than 200 client proteins in eukaryotic cells. The human genome encodes two highly similar cytosolic Hsp90 proteins called Hsp90α and Hsp90β. Most of the client proteins can interact with either Hsp90 protein; however, only a handful client proteins and one co-chaperone that interact specifically with one of the Hsp90 isoforms were identified. Structural differences underlying these isoform-specific interactions were not studied. Here we report for the first time that the Hsp90 co-chaperone Aha1 interacts preferentially with Hsp90α. The distinction depends on the middle domain of Hsp90. The middle domain of Hsp90α is also responsible for the slow growth phenotype of yeasts that express this isoform as a sole source of Hsp90. These results suggest that differences in the middle domain of Hsp90α and Hsp90β may be responsible for the isoform-specific interactions with selected proteins. Also shown here within, we determine that preferential chaperoning of cIAP1 by Hsp90β is mediated by the N-terminal domain of this isoform.

Short and long term gene expression variation and networking in human proximal tubule cells when exposed to cadmium

Cadmium (Cd²⁺) is a known nephrotoxin causing tubular necrosis during acute exposure and potentially contributing to renal failure in chronic long-term exposure. To investigate changes in global gene expression elicited by cadmium, an in-vitro exposure system was developed from cultures of human renal epithelial cells derived from cortical tissue obtained from nephrectomies. These cultures exhibit many of the qualities of proximal tubule cells. Using these cells, a study was performed to determine the cadmium-induced global gene expression changes after short-term (1 day, 9, 27, and 45 μM) and long-term cadmium exposure (13 days, 4.5, 9, and 27 μM). These studies revealed fundamental differences in the types of genes expressed during each of these time points. The obtained data was further analyzed using regression to identify cadmium toxicity responsive genes. Regression analysis showed 403 genes were induced and 522 genes were repressed by Cd²⁺ within 1 day, and 366 and 517 genes were induced and repressed, respectively, after 13 days. We developed a gene set enrichment analysis method to identify the cadmium induced pathways that are unique in comparison to traditional approaches. The perturbation of global gene expression by various Cd²⁺ concentrations and multiple time points enabled us to study the transcriptional dynamics and gene interaction using a mutual information-based network model. The most prominent network module consisted of INHBA, KIF20A, DNAJA4, AKAP12, ZFAND2A, AKR1B10, SCL7A11, and AKR1C1.

The protection of selenium against cadmium-induced cytotoxicity via the heat shock protein pathway in chicken splenic lymphocytes

Cadmium (Cd) is a heavy metal that poses a hazard to animal health due to its toxicity. Selenium (Se) is an important nutritional trace element. However, the potential protective effects of Se against Cd-induced toxicity remain to be elucidated. To investigate the cytotoxicity of Cd on bird immunocytes in vitro and the protective effects of Se against exposure to Cd, chicken splenic lymphocytes received Cd (10⁻⁶ mol/L), Se (10⁻⁷ mol/L), and the mixture of 10⁻⁷ mol/L Se and 10⁻⁶ mol/L Cd and were incubated for 12 h, 24 h, 36 h, 48 h, respectively. The transcription of heat shock protein (HSP) 27, HSP40, HSP60, HSP70 and HSP90 mRNA was tested by fluorescence quantitative PCR. The results showed that the mRNA expression of HSPs exposed to 10⁻⁶ mol/L Cd showed a sustained decrease at 12–48 h exposure. A statistically significant increase in the mRNA expression of HSPs in the case of Se group was observed, as compared to the control group of chicken splenic lymphocytes. Concomitantly, treatment of chicken splenic lymphocytes with Se in combination with Cd enhanced the mRNA expression of HSPs which were reduced by Cd treatment. This indicated that the protective effect of Se against the toxicity of Cd might, at least partially, be attributed to stimulation of the level of HSPs.

Alteration of Phascolosoma esculenta heat shock protein 90 expression under heavy metal exposure and thermal stress

The full-length complementary DNA (cDNA) of heat shock protein 90 was cloned from Phascolosoma esculenta (PeHSP90) using expressed sequence tag and rapid amplification of cDNA end approaches. The cDNA of PeHSP90 was 2521 bp including a 5'-untranslated region of 110 bp, a 3'-untranslated region of 230 bp, and an open reading frame of 2181 bp. All of the characteristic motifs of the HSP90 family were completely conserved in the deduced amino acid of PeHSP90. The expression of PeHSP90 was induced by 3 heavy metals or elevated temperature, under which Zn²⁺ displayed effects were more toxic than those of Cd²⁺ and Cu²⁺. The polyclonal antibodies generated from the recombinant product of PeHSP90 were specifically identified not only in the recombinant product but also in the native protein from hemocytes. These results strongly suggested that PeHSP90 was involved in heavy metal challenge and thermal stress regulation in P. esculenta.

Cloning and characterization of the HSP90 beta gene from Tanichthys albonubes Lin (Cyprinidae): effect of copper and cadmium exposure

Heat shock protein 90 (HSP90) is a highly conserved molecular chaperone important in the maturation of a broad spectrum of proteins. In order to evaluate the effect of copper (Cu(2+)) and cadmium (Cd(2+)) on the expression of HSP90 from Tanichthys albonubes (designated TaHSP90), the full-length complementary DNA (cDNA) of TaHSP90 was cloned using reverse transcription PCR and rapid amplification of cDNA ends (RACE) techniques. A 2,687-bp sequence was sequenced and consisted of an open reading frame (ORF) of 2,181 bp encoding a polypeptide of 727 amino acids with five HSP90 family signatures. Homologous analysis revealed that TaHSP90 gene shared high similarity with other known HSP90 genes and belonged to HSP90β subtype. Fluorescent real-time quantitative PCR was used to examine the expression pattern of TaHSP90β mRNA in different tissues (liver, muscle, gill, fin, eye, ovary, intestine and brain), and the result indicated that TaHSP90β was widely expressed in all examined tissues at different levels. Sensitivity of TaHSP90β to copper and cadmium was examined by exposing fish to different concentrations of Cu(2+) (0, 13.50 and 27.00 μg/L) and Cd(2+) (0, 1.15, 2.31 mg/L) for 24, 48, 72 and 96 h, respectively. The copper treatment induced TaHSP90β expression slight increase only at 24 and 48 h, while cadmium treatment caused slight down-regulation of TaHSP90β only 72 and 96 h. Our data suggest that the cloning and expression analysis of T. albonubes HSP90β gene provided useful molecular information of T. albonubes responses in stress conditions and potential ways to monitor the chronic stressors in T. albonubes culture environments.

Cloning of a heat shock protein 90 (HSP90) gene and expression analysis in the ridgetail white prawn Exopalaemon carinicauda

Heat shock protein 90 (HSP90) is a highly conserved molecular chaperone contributing to the folding, maintenance of structural integrity and proper regulation of a subset of cytosolic proteins. In this study, a heat shock protein 90 cDNA named EcHSP90 was cloned from the hepatopancreas of ridgetail white prawn Exopalaemon carinicauda by reverse transcription polymerase chain reaction (RT-PCR) coupled with rapid amplification of cDNA ends (RACE) approaches. The full-length cDNA of EcHSP90 was of 2695 bp, including an open reading frame (ORF) of 2163 bp encoding a polypeptide of 720 amino acids with an estimated molecular mass of 82.73 kDa and an estimated isoelectric point of 4.83. BLAST analysis revealed that the EcHSP90 shared high similarity (87.6%-75.24%) with other known HSP90s. The five conserved amino acid blocks defined as HSP90 protein family signatures were also identified in EcHSP90, which indicated that EcHSP90 should be a cytosolic member of the HSP90 family. Quantitative real-time RT-PCR analysis revealed that EcHSP90 transcript could be detected in all the tested tissues, and strongly expressed in ovary of E. carinicauda. The transcript of EcHSP90 in hepatopancreas of E. carinicauda showed different expression profiles after pH and ammonia-N stresses. The results indicated that EcHSP90 was a constitutive and inducible expressed protein and could be induced by various stresses from environment.

Activation of transcriptional activity of HSE by a novel mouse zinc finger protein ZNFD specifically expressed in testis

Zinc finger proteins (ZFPs) that contain multiple cysteine and/or histidine residues perform important roles in various cellular functions, including transcriptional regulation, cell proliferation, differentiation, and apoptosis. The Cys-Cys-His-His (C(2)H(2)) type of ZFPs are the well-defined members of this super family and are the largest and most complex proteins in eukaryotic genomes. In this study, we identified a novel C(2)H(2) type of zinc finger gene ZNFD from mice which has a 1,002 bp open reading frame and encodes a protein with 333 amino acid residues. The predicted 37.4 kDa protein contains a C(2)H(2) zinc finger domain. ZNFD gene is located on chromosome 18qD1. RT-PCR analysis revealed that the ZNFD gene was specifically expressed in mouse testis but not in other tissues. Subcellular localization analysis demonstrated that ZNFD was localized in the nucleus. Reporter gene assays showed that overexpression of ZNFD in the COS7 cells activates the transcriptional activities of heat shock element (HSE). Overall, these results suggest that ZNFD is a member of the zinc finger transcription factor family and it participates in the transcriptional regulation of HSE. Many heat shock proteins regulated by HSE are involved in testicular development. Therefore, our results suggest that ZNFD may probably participate in the development of mouse testis and function as a transcription activator in HSE-mediated gene expression and signaling pathways.

Expression pattern of heat shock protein 90 gene of humphead snapper Lutjanus sanguineus during pathogenic Vibrio harveyi stress

The full-length cDNA of heat shock protein 90 (HSP90) of humphead snapper Lutjanus sanguineus, designated as rsHSP90, was cloned by rapid amplification of complementary (c)DNA ends (RACE) techniques with the primers designed from the known expressed sequence tag (EST) sequence identified from the subtracted cDNA library of the head kidney of L. sanguineus. Sequence analysis showed that the full-length cDNA of rsHSP90 was 2745 bp, containing a 5' terminal untranslated region (UTR) of 99 bp, a 3' terminal UTR of 471 bp and an open reading frame (ORF) of 2175 bp encoding a polypeptide of 725 amino acids. On the basis of the deduced amino acid sequence, the theoretical molecular mass of rsHSP90 was calculated to be 83·18 kDa with an isoelectric point of 4·79. Moreover, five classical HSP90 family signatures were found in the amino acids sequence of rsHSP90 by PredictProtein. Basic local-alignment search-tool (BLAST) analysis revealed that the amino acids sequence of rsHSP90 had the highest similarity of 97% when compared with other HSP90s. Fluorescent real-time quantitative reverse-transcription (RT)-PCR was used to examine the expression pattern of rsHSP90 in eight kinds of tissues and organs of L. sanguineus challenged with Vibrio harveyi. There was a clear time-dependent expression pattern of rsHSP90 in head kidney, spleen and thymus after bacterial challenge and the expression of messenger (m)RNA reached the maximum level at the time points of 9, 15 and 24 h, respectively. The up-regulated mRNA expression of rsHSP90 in L. sanguineus after bacterial challenge indicated that rsHSP90 was inducible and might be involved in immune response.

Metabolic and osmoregulatory changes and cell proliferation in gilthead sea bream (Sparus aurata) exposed to cadmium

The impact of cadmium on metabolism and osmoregulation was assessed in gilthead sea bream (Sparus aurata). Seawater acclimated fish were injected intraperitoneally with a sublethal dose of cadmium (1.25 mg Cd/kg body wt). After 7 days, half of the injected fish were sampled. The remaining fish were transferred to hypersaline water and sampled 4 days later. Gill and kidney Na(+)/K(+)-ATPase activities, plasma levels of cortisol, several metabolites and osmolytes, as well as osmolality were measured. Hepatosomatic index and condition factor were calculated. The expression levels of Na(+)/K(+)-ATPase, heat shock proteins (HSP70, HSP90) and proliferating cell nuclear antigen was assessed by western blotting. Cadmium treatment adversely affected the Na(+)/K(+)-ATPase activity, although, there was no perturbation in ion homeostasis and the animals were not compromised following transfer to hypersaline water. Increased cell proliferation and Hsp90 expression likely contributed to the attenuation of the deleterious effects of cadmium exposure.

Microarray analysis of gene expression patterns in human proximal tubule cells over a short and long time course of cadmium exposure

Numerous studies showed that renal proximal tubules cells are the cell type critically affected by chronic exposure to cadmium (Cd(2+)). The aim of the present study was to apply global gene expression technology and a human renal epithelial cell culture model (HPT) to determine whether time of exposure to Cd(2+) exerts a major influence on the resulting pattern of global gene expression. HPT cells were exposed to Cd(2+) for a short, 1-d, period of exposure (9, 27, and 45 μM) versus a longer, 13-d, period (4.5, 9, and 27 μM), with the hypothesis being that the stress response of the cells would be more active during the short time of exposure. The results showed that the differential expression of genes was very extensive for HPT cells exposed to Cd(2+) for 1 d, with more than 1848 genes displaying alterations compared to control and with the major categories of genes being involved in stress responses; cell death; checkpoint arrest, DNA repair, and the cell cycle; inflammatory responses; and cell adhesion, motion and differentiation. In contrast, HPT cells exposed to Cd(2+) for 13 d showed 923 genes to be differentially expressed, with a marked reduction in the number of differentially expressed stress response genes and a significant increase in the number of genes involved in development and differentiation. There were 387 differentially expressed genes common to both times of exposure. Data suggest that unless one is actively seeking to study the acute stress response, global gene expression technology should not be applied within an early time course of toxicant exposure.

Arsenite stabilizes HIF-1α protein through p85α-mediated up-regulation of inducible Hsp70 protein expression

Hypoxia-inducible factor-1α (HIF-1α) has been reported to regulate over 100 gene expressions in response to hypoxia and other stress conditions. In the present study, we found that arsenite could induce HIF-1α protein accumulation in both mouse epidermal Cl41 cells and mouse embryonic fibroblasts (MEFs). Knockout of p85α, a regulatory subunit of PI-3K, in MEFs (p85α(-/-)) dramatically decreased the arsenite-induced HIF-1α accumulation, indicating that p85α is crucial for arsenite effects on the stabilization of HIF-1α protein. Our further studies suggest that arsenite could induce inducible Hsp70 expression, and transfection of inducible Hsp70 into p85α(-/-) MEFs could restore HIF-1α protein accumulation. Moreover, the results using EMSA and Supershift assays indicate that p85α is crucial for arsenite-induced activation of the heat-shock transcription factor 1 (HSF-1), which is responsible for transcription of inducible Hsp70. Taken together, p85α-mediated HIF-1α stabilization upon arsenite exposure is specifically through HSF-1 activation and subsequent up-regulation of the inducible Hsp70 expression.

Cloning of an orange-spotted grouper Epinephelus coioides heat shock protein 90AB (HSP90AB) and characterization of its expression in response to nodavirus

The heat shock proteins (HSPs) family which consists of HSP90, HSP70, and low molecular mass HSPs are involved in chaperone activity. Here, we report the cloning and characterization of HSP90AB gene from orange-spotted grouper, Epinephelus coioides. The full-length of grouper HSP90AB was 727 amino acids and possessed an ATPase domain as well as an evolutionarily conserved molecular chaperone. The HSP90AB-green fluorescent protein fusion protein was evenly distributed in the cytoplasm. Immunohistochemistry (IHC) and real-time polymerase chain reaction (PCR) analyses indicated that the expression of grouper HSP90AB was marginally increased following nodavirus infection. Grouper E. coioides that received HSP90 inhibitor geldanamycin (GA) showed an increase in HSP90AB expression and growth of nodavirus supporting nodavirus replication.

Characterization of orchardgrass p23, a flowering plant Hsp90 cohort protein

p23 is a heat shock protein 90 (Hsp90) co-chaperone and stabilizes the Hsp90 heterocomplex in mammals and yeast. In this study, we isolated a complementary DNA (cDNA) encoding p23 from orchardgrass (Dgp23) and characterized its functional roles under conditions of thermal stress. Dgp23 is a 911 bp cDNA with an open reading frame predicted to encode a 180 amino acid protein. Northern analysis showed that expression of Dgp23 transcripts was heat inducible. Dgp23 has a well-conserved p23 domain and interacted with an orchardgrass Hsp90 homolog in vivo, like mammalian and yeast p23 homologs. Recombinant Dgp23 is a small acidic protein with a molecular mass of approximately 27 kDa and pI 4.3. Dgp23 was also shown to function as a chaperone protein by suppression of malate dehydrogenase thermal aggregation. Differential scanning calorimetry thermograms indicated that Dgp23 is a heat-stable protein, capable of increasing the T (m) of lysozyme. Moreover, overexpression of Dgp23 in a yeast p23 homolog deletion strain, Deltasba1, increased cell viability. These results suggest that Dgp23 plays a role in thermal stress-tolerance and functions as a co-chaperone of Hsp90 and as a chaperone.

Molecular cloning, characterization and expression of heat shock protein 90 gene in the haemocytes of bay scallop Argopecten irradians

Heat shock protein 90 (HSP90) is a highly conserved molecular chaperone that plays key roles in the folding, maintenance of structural integrity and regulation of a subset of cytosolic proteins. In the present study, the cDNA of Argopecten irradians HSP90 (designated AiHSP90) was cloned by the combination of homology cloning and rapid amplification of cDNA ends (RACE) approaches. The full-length cDNA of AiHSP90 was of 2669 bp, including an open reading frame (ORF) of 2175 bp encoding a polypeptide of 724 amino acids with predicted molecular weight of 83.08 kDa and theoretical isoelectric point of 4.81. BLAST analysis revealed that AiHSP90 shared high similarity with other known HSP90s, and the five conserved amino acid blocks defined as HSP90 protein family signatures were also identified in AiHSP90, which indicated that AiHSP90 should be a cytosolic member of the HSP90 family. Fluorescent real-time quantitative PCR was employed to examine the expression pattern of AiHSP90 mRNA in haemocytes of scallops challenged by Gram-negative bacteria Vibrio anguillarum and Gram-positive bacteria Micrococcus luteus. In both bacterial challenged groups, the relative expression level of AiHSP90 transcript was up-regulated and reached maximal level at 9h after injection, and then dropped progressively to the original level at about 48 h post challenge. The results indicated that AiHSP90 was potentially involved in the immune responses against bacteria challenge in scallop A. irradian.

cDNA cloning and mRNA expression of heat shock protein 90 gene in the haemocytes of Zhikong scallop Chlamys farreri

Heat shock protein 90 (HSP90) is a highly conserved molecular chaperone contributing to the folding, maintenance of structural integrity and proper regulation of a subset of cytosolic proteins. The full-length cDNA of Zhikong scallop Chlamys farreri HSP90 (designated CfHSP90) was cloned by EST and rapid RACE techniques. It was of 2710 bp, including an open reading frame (ORF) of 2181 bp encoding a polypeptide of 726 amino acids with all the five HSP90 family signatures. BLAST analysis revealed that the CfHSP90 gene shared high similarity with other known HSP90 genes. Fluorescent real-time quantitative RT-PCR was used to examine the expression pattern of CfHSP90 mRNA in haemocytes of scallops exposed to Cd2+, Pb2+ and Cu2+ for 10 and 20 days, respectively. All the three heavy metals could induce CfHSP90 expression. There was a clear dose-dependent expression pattern of CfHSP90 after heavy metals exposure for 10 days or 20 days. Different concentrations of the same metal resulted in different effects on CfHSP90 expression. The results indicated that CfHSP90 responded to various heavy metal stresses with a dose-dependent expression pattern as well as exposure time effect, and could be used as a molecular biomarker in a heavy metal polluted environment.

Metallothionein and hsp70 expression in HepG2 cells after prolonged cadmium exposure

Cadmium is a widely distributed industrial and environmental pollutant. Principle target organs are soft tissues such as the liver, where cadmium accumulates with a biological half-life of approximately 20-30 years causing a variety of toxic responses. In HepG2, CdCl(2) exposure for short periods (from 1 to 24h) induces differential expression of stress proteins, including MT and hsp70. However, less is known about the stress response during a prolonged exposure to this metal. MTT assay showed a low cytotoxicity of CdCl(2) (0.1, 0.5, 1, 2, 5, 10microM), over a period of 72h. Cadmium uptake by ICP-AES technique and the corresponding expression of stress proteins (MT, hsp70) during the same prolonged time were also analysed. Results show that Cd was continuously and increasingly accumulated, at the highest of the concentrations tested. Metallothionein expression was up-regulated with a saturation curve at 48 as well as 72h after CdCl(2) exposure. High levels of MT probably confer an acquired tolerance to the stress and protection against cell injury as demonstrated by low cytotoxicity values. On the contrary, the unchanged pattern of hsp70 expression suggests that this protective mechanism, unlike other members of the family, is less involved during CdCl(2) prolonged exposure.

Phenotypic anchoring of arsenic and cadmium toxicity in three hepatic-related cell systems reveals compound- and cell-specific selective up-regulation of stress protein expression: implications for fingerprint profiling of cytotoxicity

Exposure of cells to toxic chemicals is known to up-regulate the expression of a number of stress proteins (SPs), including metallothionein (MT) and members of the heat shock protein (HSP) family, and this response may allow the development of a fingerprint profile to identify mechanisms of toxicity in an in vitro toxicology setting. To test this hypothesis, three hepatic-derived cell culture systems (rat hepatoma FGC4 cell line, rat hepatocytes, human hepatoma HepG2 cell line) were exposed to cadmium (as CdCl2) and arsenic (as NaAsO2), two compounds believed to exert their toxicity through an oxidative stress mechanism, under conditions of phenotypic anchoring defined as minimal and mild toxicity (approximately 5 and 25% reduction in neutral red uptake, respectively). The expression of six SPs--MT, HSP25/27, HSP40, HSP60, HSP70, and HSP90--was then determined by ELISA. Expression of four of these SPs--MT, HSP25/27, HSP40 and HSP70--was up-regulated in at least one experimental condition. However, the patterns of expression of these four SPs varied across the experimental conditions, according to differences in toxicant concentration and/or level of toxicity, cell-type and toxicant itself. This lack of uniformity in response of a focussed set of mechanistically defensible targets suggests that similar problems may emerge when using more global approaches based on genomics and proteomics, in which problems of redundancy in targets and uncertain mechanistic relevance will be greater.

Metal ions induced heat shock protein response by elevating superoxide anion level in HeLa cells transformed by HSE-SEAP reporter gene

The aim of this work is to define the relationship between heat shock protein (HSP) and reactive oxygen species (ROS) in the cells exposed to different concentrations of metal ions, and to evaluate a new method for tracing the dynamic levels of cellular reactive oxygen species using a HSE-SEAP reporter gene. The expression of heat shock protein was measured using a secreted alkaline phosphatase (SEAP) reporter gene transformed into HeLa cell strain, the levels of superoxide anion (O(2)(-)) and hydrogen peroxide (H(2)O(2)) were determined by NBT reduction assay and DCFH staining flow cytometry (FCM), respectively. The experimental results demonstrated that the expression of heat shock protein induced by metal ions was linearly related to the cellular superoxide anion level before cytotoxic effects were observed, but not related to the cellular hydrogen peroxide level. The experimental results suggested that metal ions might induce heat shock protein by elevating cellular superoxide anion level, and thus the expression of heat shock protein indicated by the HSE-SEAP reporter gene can be an effective model for monitoring the dynamic level of superoxide anion and early metal-induced oxidative stress/cytotoxicity.

Upregulation and intrarenal redistribution of heat shock proteins 90alpha and 90beta by low-sodium diet in the rat

Two genes encoding isoforms heat shock protein (Hsp) 90alpha and Hsp90beta constitute the Hsp90 subfamily. In addition to their role in regulating mineralocorticoid and glucocorticoid receptors, these proteins have been associated with nitric oxide production. However, little is known regarding Hsp90 isoform expression and regulation in kidney. In this study we characterized the expression and localization of Hsp90 isoforms and evaluated the influence of low-sodium intake on their expression and distribution in kidney by using reverse transcription-polymerase chain reaction, Western blot, and immunohistochemistry techniques. We found that Hsp90alpha and Hsp90beta were expressed abundantly in both the renal cortex and the medulla; however, Hsp90 isoform expression was higher in the medulla than in the cortex. Immunohistochemistry of Hsp90alpha and Hsp90beta showed intense staining in the apical membrane of proximal and distal tubules. In the outer cortex these proteins were localized intracytosolically, whereas in the inner renal medulla they were restricted mainly to the basolateral membrane. Expression of Hsp9alpha and Hsp90beta was upregulated in the renal cortex during sodium restriction. In addition, both proteins exhibited redistribution from the cytoplasm to the basolateral side in thick ascending limb cells when rats were fed with a low-salt diet. Our results showed that Hsp90alpha and Hsp90beta were expressed abundantly in renal tissue. Expression and localization patterns under normal and salt-restricted intake were different between the cortex and the medulla, suggesting that these proteins may be involved in different processes along the nephron. Hsp90alpha and Hsp90beta upregulation induced by a low-sodium diet together with redistribution in thick ascending limb cells suggests that Hsp90 plays a role in the modulation of sodium reabsorption under these circumstances.

Hsp27, Hsp70, and metallothionein in MDCK and LLC-PK1 renal epithelial cells: effects of prolonged exposure to cadmium

Cadmium is a widely distributed industrial and environmental toxin. The principal target organ of chronic sublethal cadmium exposure is the kidney. In renal epithelial cells, acute high-dose cadmium exposure induces differential expression of proteins, including heat shock proteins. However, few studies have examined heat shock protein expression in cells after prolonged exposure to cadmium at sublethal concentrations. Here, we assayed total cell protein, neutral red uptake, cell death, and levels of metallothionein and heat shock proteins Hsp27 and inducible Hsp70 in cultures of MDCK and LLC-PK1 renal epithelial cells treated with cadmium for 3 days. Treatment with cadmium at concentrations equal to or greater than 10 microM (LLC-PK1) or 25 microM (MDCK) reduced measures of cell vitality and induced cell death. However, a concentration-dependent increase in Hsp27 was detected in both cell types treated with as little as 5 microM cadmium. Accumulation of Hsp70 was correlated only with cadmium treatment at concentrations also causing cell death. Metallothionein was maximally detected in cells treated with cadmium at concentrations that did not reduce cell vitality, and further increases were not detected at greater concentrations. These results reveal that heat shock proteins accumulate in renal epithelial cells during prolonged cadmium exposure, that cadmium induces differential expression of heat shock protein in epithelial cells, and that protein expression patterns in epithelial cells are specific to the cadmium concentration and degree of cellular injury. A potential role for Hsp27 in the cellular response to sublethal cadmium-induced injury is also implicated by our results.