Chaperoning signaling pathways: molecular chaperones as stress-sensing`heat shock' proteins

Characterization of Hsp70 gene in Chironomus riparius: expression in response to endocrine disrupting pollutants as a marker of ecotoxicological stress

We characterized the Hsp70 cDNA in Chironomus riparius and evaluated its expression profile under different environmental stressors. It is highly conserved, at both DNA and protein levels, displaying many of the hallmarks of Hsps and sharing 80-96% of overall amino acid identities with homologous sequences from other diptera. The changes are mainly concentrated in the C-terminal domain of the protein. Phylogenetic analysis was consistent with the known classification of insects. The Hsp70 gene was located by in situ hybridization in region III-3A at the third polytene chromosome, a locus activated upon heat shock as shown by RNA pol II binding. As C. riparius is widely used in aquatic ecotoxicology testing, we studied Hsp70 gene induction in fourth instar aquatic larvae submitted to heat shock and selected environmental pollutants classified as potential endocrine disruptors. RT-PCR analysis showed that Hsp70 mRNA levels increased significantly (p<0.05) after short-term acute exposures to a temperature shift (HS), cadmium chloride (Cd), butyl benzyl phthalate (BBP), diethylhexyl phthalate (DEHP), bisphenol A (BPA), 4-nonylphenol (NP) and ethinylestradiol (EE). However, neither pentachlorophenol (PCP) nor tributyltin (TBTO) treatments were able to activate the Hsp70 gene. The cognate form, Hsc70, was also analysed and, unlike Hsp70, was not altered by any of the different treatments assayed. Moreover, at the times tested, there was no significant mortality of the larvae. The rapid upregulation of the Hsp70 gene suggests that it is sensitive and selective for different environmental pollutants, and could be used as an early molecular endpoint in ecotoxicological studies.

N-terminal domain of human Hsp90 triggers binding to the cochaperone p23

The molecular chaperone Hsp90 is a protein folding machine that is conserved from bacteria to man. Human, cytosolic Hsp90 is dedicated to folding of chiefly signal transduction components. The chaperoning mechanism of Hsp90 is controlled by ATP and various cochaperones, but is poorly understood and controversial. Here, we characterized the Apo and ATP states of the 170-kDa human Hsp90 full-length protein by NMR spectroscopy in solution, and we elucidated the mechanism of the inhibition of its ATPase by its cochaperone p23. We assigned isoleucine side chains of Hsp90 via specific isotope labeling of their δ-methyl groups, which allowed the NMR analysis of the full-length protein. We found that ATP caused exclusively local changes in Hsp90's N-terminal nucleotide-binding domain. Native mass spectrometry showed that Hsp90 and p23 form a 22 complex via a positively cooperative mechanism. Despite this stoichiometry, NMR data indicated that the complex was not fully symmetric. The p23-dependent NMR shifts mapped to both the lid and the adenine end of Hsp90's ATP binding pocket, but also to large parts of the middle domain. Shifts distant from the p23 binding site reflect p23-induced conformational changes in Hsp90. Together, we conclude that it is Hsp90's nucleotide-binding domain that triggers the formation of the Hsp90(2)p23(2) complex. We anticipate that our NMR approach has significant impact on future studies of full-length Hsp90 with cofactors and substrates, but also for the development of Hsp90 inhibiting anticancer drugs.

Characterisation of hookworm heat shock factor binding protein (HSB-1) during heat shock and larval activation

When hookworm infective L3s infect their mammalian host, they undergo a temperature shift from that of the ambient environment to that of their endothermic host. Additionally, L3s living in the environment can be exposed to temperature extremes associated with weather fluctuations. The heat shock response (HSR) is a conserved response to heat shock and other stress that involves the expression of protective heat shock proteins (HSPs). The HSR is controlled by heat shock factor-1 (HSF-1), a conserved transcription factor that binds to a heat shock element in the promoter of HSPs, causing their expression. HSF-1 is negatively regulated in part by a HSF binding protein (HSB-1) that binds to and removes HSF-1 trimers bound to HSP gene promoters, resulting in attenuation of the HSR. Herein we describe an HSB-1 orthologue, Ac-HSB-1, from the hookworm Ancylostoma caninum. The Ac-hsb-1 cDNA encodes a 79 amino acid protein that is 71% identical to the Caenorhabditis elegans HSB-1, and is predicted to share the characteristic coiled-coil structural motif comprised of two interacting alpha helices. Recombinant Ac-HSB-1 immunoprecipitated Ce-HSF-1 expressed in mammalian cells that had been heat shocked for 1h at 42°C, but not from cells incubated at 37°C, indicating that HSB-1 only bound to the active DNA binding form of HSF-1. Expression of Ac-hsb-1 transcripts decreased following 1h of heat shock, but increased when L3s were incubated at 37°C for 1h. Activation of hookworm L3s induces a five-sixfold increase in Ac-hsb-1 expression that peaks at 12h, coincident with L3 feeding, but that subsequently decreases to two-threefold above control at 24h. Recombinant Ac-HSB-1 immunoprecipitates greater amounts of 70 and 40kDa proteins from extracts of activated L3s than from non-activated L3s. We propose that an increase in Ac-hsb-1 levels early in activation allows feeding to resume, but that a subsequent decrease in expression permits a HSR that protects non-developing L3s at host-like temperatures. Further investigations of the HSR will clarify the role of HSB-1 and HSF-1 in hookworm infection.

Chemistry and biochemistry of lipid peroxidation products

Oxidative stress and resulting lipid peroxidation is involved in various and numerous pathological states including inflammation, atherosclerosis, neurodegenerative diseases and cancer. This review is focused on recent advances concerning the formation, metabolism and reactivity towards macromolecules of lipid peroxidation breakdown products, some of which being considered as 'second messengers' of oxidative stress. This review relates also new advances regarding apoptosis induction, survival/proliferation processes and autophagy regulated by 4-hydroxynonenal, a major product of omega-6 fatty acid peroxidation, in relationship with detoxication mechanisms. The use of these lipid peroxidation products as oxidative stress/lipid peroxidation biomarkers is also addressed.

The hyperthermia-enhanced association between tropoelastin and its 67-kDa chaperone results in better deposition of elastic fibers

The results of our in vitro experiments indicate that exposing cultured human aortic smooth muscle cells and dermal fibroblasts to 39 to 41 °C induces a significant up-regulation in the net deposition of elastic fibers, but not of collagen I or fibronectin, and also decreases the deposition of chondroitin sulfate-containing moieties. We further demonstrate that mild hyperthermia also rectifies the insufficient elastogenesis notable in cultures of fibroblasts derived from the stretch-marked skin of adult patients and in cultures of dermal fibroblasts from children with Costello syndrome, which is characterized by the accumulation of chondroitin 6-sulfate glycosaminoglycans that induce shedding and inactivation of the 67-kDa elastin-binding protein. We have previously established that this protein serves as a reusable chaperone for tropoelastin and that its recycling is essential for the normal deposition of elastic fibers. We now report that hyperthermia not only inhibits deposition of chondroitin 6-sulfate moieties and the consequent preservation of elastin-binding protein molecules but also induces their faster recycling. This, in turn, triggers a more efficient preservation of tropoelastin, enhancement of its secretion and extracellular assembly into elastic fibers. The presented results encourage using mild hyperthermia to restore elastic fiber production in damaged adult skin and to enhance elastogenesis in children with genetic elastinopathies.

Activating transcription factor-3 (ATF3) functions as a tumor suppressor in colon cancer and is up-regulated upon heat-shock protein 90 (Hsp90) inhibition

Background

Activating transcription factor-3 (ATF3) is involved in the complex process of cellular stress response. However, its exact role in cancer is discussed controversially because both tumor suppressive and oncogenic effects have been described. Here we followed-up on our previous observation that inhibition of Hsp90 may increase ATF3 expression and sought to determine the role of ATF3 in colon cancer.

Methods

Regulation of ATF3 was determined in cancer cells using signaling inhibitors and a heat-shock protein-90 (Hsp90) antagonist. Human HCT116 cancer cells were stably transfected with an ATF3-shRNA or a luciferase-shRNA expression plasmid and alterations in cell motility were assessed in migration assays. The impact of ATF3 down-regulation on cancer growth and metastasis were investigated in a subcutaneous tumor model, a model of hepatic tumor growth and in a model of peritoneal carcinomatosis. Human colon cancer tissues were analyzed for ATF3 expression.

Results

The results show that therapeutic Hsp90 inhibition substantially up-regulates the expression of ATF3 in various cancer cells, including colon, gastric and pancreatic cancer. This effect was evident both in vitro and in vivo. RNAi mediated knock-down of ATF3 in HCT116 colon cancer cells significantly increased cancer cell migration in vitro. Moreover, in xenogenic mouse models, ATF3 knock-down promoted subcutaneous tumor growth and hepatic metastasis, as well as peritoneal carcinomatosis. Importantly, ATF3 expression was lower in human colon cancer specimens, as compared to corresponding normal surrounding tissues, suggesting that ATF3 may represent a down-regulated tumor suppressor in colon cancer.

Conclusion

In conclusion, ATF3 down-regulation in colon cancer promotes tumor growth and metastasis. Considering that blocking Hsp90 induces ATF3 expression, Hsp90 inhibition may represent a valid strategy to treat metastatic colon cancer by up-regulating this anti-metastatic transcription factor.

Transcripts analysis of infective larvae of an intestinal nematode, Strongyloides venezuelensis

Free-living infective larvae of Strongyloides nematodes fulfill a number of requirements for the successful infection. They need to endure a long wait in harsh environmental conditions, like temperature, salinity, and pH, which might change drastically from time to time. Infective larvae also have to deal with pathogens and potentially hazardous free-living microbes in the environment. In addition, infective larvae must recognize the adequate host properly, and start skin penetration as quickly as possible. All these tasks are essentially important for the survival of Strongyloides nematodes, however, our knowledge is extremely limited in any one of these aspects. In order to understand how Strongyloides infective larvae meet these requirements, we examined transcripts of infective larvae by randomly sequencing cDNA clones constructed from S. venezuelensis infective larvae. After assembling successfully sequenced clones, we obtained 162 unique singletons and contigs, of which 84 had been significantly annotated. Annotated genes included those for respiratory enzymes, heat-shock proteins, neuromuscular proteins, proteases, and immunodominant antigens. Genes for lipase, small heat-shock protein, globin-like protein and cytochrome c oxidase were most abundantly transcribed, though genes of unknown functions were also abundantly transcribed. There were no hits found against NCBI or NEMABASE4 for 37 (22.3%) EST out of the total 162 EST. Although most of the transcripts were not infective larva-specific, the expression of respiration related proteins was most actively transcribed in the infective larva stage. The expression of astacin-like metalloprotease, small heat-shock protein, S. stercoralis L3Nie antigen homologue, and one unannotated and 2 novel genes was highly specific for the infective larva stage.

Increased expression of co-chaperone HOP with HSP90 and HSC70 and complex formation in human colonic carcinoma

Co-chaperone HOP (also called stress-inducible protein 1) is a co-chaperone that interacts with the cytosolic 70-kDa heat shock protein (HSP70) and 90-kDa heat shock protein (HSP90) families using different tetratricopeptide repeat domains. HOP plays crucial roles in the productive folding of substrate proteins by controlling the chaperone activities of HSP70 and HSP90. Here, we examined the levels of HOP, HSC70 (cognate of HSP70, also called HSP73), and HSP90 in the tumor tissues from colon cancer patients, in comparison with the non-tumor tissues from the same patients. Expression level of HOP was significantly increased in the tumor tissues (68% of patients, n = 19). Levels of HSC70 and HSP90 were also increased in the tumor tissues (95% and 74% of patients, respectively), and the HOP level was highly correlated with those of HSP90 (r = 0.77, p < 0.001) and HSC70 (r = 0.68, p < 0.01). Immunoprecipitation experiments indicated that HOP complexes with HSC70 or HSP90 in the tumor tissues. These data are consistent with increased formation of co-chaperone complexes in colon tumor specimens compared to adjacent normal tissue and could reflect a role for HOP in this process.

Effects of 50-Hz magnetic field exposure on superoxide radical anion formation and HSP70 induction in human K562 cells

Epidemiological studies suggest a correlation between exposure to low-level extremely low-frequency (ELF) magnetic fields (MF) and certain cancers and neurodegenerative diseases. Experimental studies have not provided any mechanism for such effects, although at flux density levels significantly higher than the ones encountered in epidemiological studies, radical homoeostasis and levels of stress response proteins can be affected. Here, we report on the influence of MF exposure (50-Hz sine wave; 1 h; 0.025-0.10 mT; vertical or horizontal MF exposure direction) on different cellular parameters (proliferation, cell cycle distribution, superoxide radical anion, and HSP70 protein levels) in the human leukaemia cell line K562. The positive control heat treatment (42°C, 1 h) did not affect either cell proliferation or superoxide radical anion production but caused accumulation of cells in the G2 phase and increased the stress protein HSP70. MF exposure (0.10 mT, 1 h) did not affect either cell cycle kinetics or proliferation. Both vertical and horizontal MF exposures for 1 h caused significantly and transiently increased HSP70 levels (>twofold), at several flux densities, compared to sham controls and also compared to heat treatment. This exposure also increased (30-40%) the levels of the superoxide radical anion, comparable to the positive control PMA. Addition of free radical scavengers (melatonin or 1,10-phenantroline) inhibited the MF-induced increase in HSP70. In conclusion, an early response to ELF MF in K562 cells seems to be an increased amount of oxygen radicals, leading to HSP70 induction. Furthermore, the results suggest that there is a flux density threshold where 50-Hz MF exerts its effects on K562 cells, at or below 0.025 mT, and also that it is the MF, and not the induced electric field, which is the active parameter.

Insights into the extracytoplasmic stress response of Xanthomonas campestris pv. campestris: role and regulation of {sigma}E-dependent activity

Xanthomonas campestris pv. campestris is an epiphytic bacterium that can become a vascular pathogen responsible for black rot disease of crucifers. To adapt gene expression in response to ever-changing habitats, phytopathogenic bacteria have evolved signal transduction regulatory pathways, such as extracytoplasmic function (ECF) σ factors. The alternative sigma factor σ(E), encoded by rpoE, is crucial for envelope stress response and plays a role in the pathogenicity of many bacterial species. Here, we combine different approaches to investigate the role and mechanism of σ(E)-dependent activation in X. campestris pv. campestris. We show that the rpoE gene is organized as a single transcription unit with the anti-σ gene rseA and the protease gene mucD and that rpoE transcription is autoregulated. rseA and mucD transcription is also controlled by a highly conserved σ(E)-dependent promoter within the σ(E) gene sequence. The σ(E)-mediated stress response is required for stationary-phase survival, resistance to cadmium, and adaptation to membrane-perturbing stresses (elevated temperature and ethanol). Using microarray technology, we started to define the σ(E) regulon of X. campestris pv. campestris. These genes encode proteins belonging to different classes, including periplasmic or membrane proteins, biosynthetic enzymes, classical heat shock proteins, and the heat stress σ factor σ(H). The consensus sequence for the predicted σ(E)-regulated promoter elements is GGAACTN(15-17)GTCNNA. Determination of the rpoH transcription start site revealed that rpoH was directly regulated by σ(E) under both normal and heat stress conditions. Finally, σ(E) activity is regulated by the putative regulated intramembrane proteolysis (RIP) proteases RseP and DegS, as previously described in many other bacteria. However, our data suggest that RseP and DegS are not only dedicated to RseA cleavage and that the proteolytic cascade of RseA could involve other proteases.

Modulation of the cannabinoid receptors by andrographolide attenuates hepatic apoptosis following bile duct ligation in rats with fibrosis

Bile acid-induced apoptosis plays an important role in the pathogenesis of cholestatic liver disease, and its prevention is of therapeutic interest. The aim of this study was to test whether the andrographolide limits the evolution of apoptosis in a murine model of bile duct ligation (BDL)-induced hepatic fibrosis. Male Sprague-Dawley rats were divided into four groups and hepatic apoptosis was induced by BDL for 2 weeks. The BDL animals were also treated with andrographolide (50, 100, and 200 mg/kg, i.p.) during the same time period. BDL-induced liver injury was associated with apoptosis and fibrosis, and the latter was significantly reduced in animals receiving andrographolide. The increase in serum alanine aminotransferase, asparate aminotransferase, tumor necrosis factor-alpha and IL-1beta levels caused by BDL were also significantly reduced by treatment with andrographolide. Andrographolide decreased the intrahepatic protein levels of cannabinoid receptor 1 (CB1), Bax, and cytochrome c, along with of alpha-smooth muscle actin (alpha-SMA) and transforming growth factor-beta (TGF-beta), two markers of fibrogenesis. This effect was mediated by the inactivation of the c-Jun N-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK1/2) phosphorylation cascade, but it did not affect the p38 mitogen-activated protein kinase pathway. Additionally, andrographolide reduced the generation of hepatic lipid peroxidation and enhance senescence marker protein-30 levels to resist the hepatic oxidative stress in the presence of BDL. In conclusion, this study has identified AP as a potent protector against cholestasis-induced apoptosis in vivo. Its anti-apoptotic action largely relies on the inhibition of the oxidative stress pathway.

O-linked beta-N-acetylglucosamine (O-GlcNAc) regulates stress-induced heat shock protein expression in a GSK-3beta-dependent manner

To investigate the mechanisms by which O-linked β-N-acetylglucosamine modification of nucleocytoplasmic proteins (O-GlcNAc) confers stress tolerance to multiple forms of cellular injury, we explored the role(s) of O-GlcNAc in the regulation of heat shock protein (HSP) expression. Using a cell line in which deletion of the O-GlcNAc transferase (OGT; the enzyme that adds O-GlcNAc) can be induced by 4-hydroxytamoxifen, we screened the expression of 84 HSPs using quantitative reverse transcriptase PCR. In OGT null cells the stress-induced expression of 18 molecular chaperones, including HSP72, were reduced. GSK-3β promotes apoptosis through numerous pathways, including phosphorylation of heat shock factor 1 (HSF1) at Ser(303) (Ser(P)(303) HSF1), which inactivates HSF1 and inhibits HSP expression. In OGT null cells we observed increased Ser(P)(303) HSF1; conversely, in cells in which O-GlcNAc levels had been elevated, reduced Ser(P)(303) HSF1 was detected. These data, combined with those showing that inhibition of GSK-3β in OGT null cells recovers HSP72 expression, suggests that O-GlcNAc regulates the activity of GSK-3β. In OGT null cells, stress-induced inactivation of GSK-3β by phosphorylation at Ser(9) was ablated providing a molecular basis for these findings. Together, these data suggest that stress-induced GlcNAcylation increases HSP expression through inhibition of GSK-3β.

Identification of novel 14-3-3ζ interacting proteins by quantitative immunoprecipitation combined with knockdown (QUICK)

The family of 14-3-3 proteins has emerged as critical regulators of diverse cellular responses under both physiological and pathological conditions. To gain insight into the molecular action of 14-3-3ζ in multiple myeloma (MM), we performed a systematic proteomic analysis of 14-3-3ζ-associated proteins. This analysis, recently developed by Matthias Mann, termed quantitative immunoprecipitation combined with knockdown (QUICK), integrates RNAi, SILAC, immunoprecipitation, and quantitative MS technologies. Quantitative mass spectrometry analysis allowed us to distinguish 14-3-3ζ-interacting proteins from background proteins, resulting in the identification of 292 proteins in total with 95 novel interactions. Three 14-3-3ζ-interacting proteins-BAX, HSP70, and BAG3-were further confirmed by reciprocal coimmunoprecipitations and colocalization analysis. Our results therefore not only uncover a large number of novel 14-3-3ζ-associated proteins that possess a variety of cellular functions, but also provide new research directions for the study of the functions of 14-3-3ζ. This study also demonstrated that QUICK is a useful approach to detect specific protein-protein interactions with very high confidence and may have a wide range of applications in the investigation of protein complex interaction networks.

Non-thermal cellular effects of lowpower microwave radiation on the lens and lens epithelial cells

Because of the increased use of modern radiofrequency devices, public concern about the possible health effects of exposure to microwave radiation has arisen in many countries. It is well established that high-power microwave radiation can induce cataracts via its thermal effects. It remains unclear whether low-power microwave radiation, especially at levels below the current exposure limits, is cataractogenic. This review summarizes studies on the biological effects of low-power microwave radiation on lens and lens epithelial cells (LECs). It has been reported that exposure affects lens transparency, alters cell proliferation and apoptosis, inhibits gap junctional intercellular communication, and induces genetic instability and stress responses in LECs. These results raise the question of whether the ambient microwave environment can induce non-thermal effects in the lens and whether such effects have potential health consequences. Further in vivo studies on the effects on the lens of exposure to low-power microwave radiation are needed.

The 2009 stock conference report: inflammation, obesity and metabolic disease

Obesity is linked with many deleterious health consequences and is associated with increased risk of chronic disease including type 2 diabetes, atherosclerosis and certain forms of cancer. Recent work has highlighted the impact of obesity to activate inflammatory gene networks and suggests a causal function of inflammation in the pathogenesis of the metabolic syndrome. Since 2005, when Dr Gokhan Hotamisligil chaired the fourth Stock Conference in Istanbul, Turkey, entitled 'Obesity and Inflammation', there has been an explosion of studies investigating the relationship between obesity, inflammation and substrate metabolism. The exuberance surrounding this field of research is exemplified by the body of work that has been published in these past 4 years, including over 1400 publications. During this time, several novel mechanisms relating to cellular inflammation have been uncovered including the role of the hematopoietic system, toll-like receptor activation, endoplasmic reticulum stress and very recently T-cell activation in obesity-induced insulin resistance. These discoveries have led us to rethink cellular nutrient sensing and its role in inflammation and metabolic disease. Despite burgeoning investigation in this field, there still remain a number of unanswered questions. This review that evolved from the 2009 Stock Conference summarizes current research and identifies the deficiencies in our understanding of this topic. The overall goal of this Stock Conference was to bring together leading investigators in the field of inflammation and obesity research in the hope of fostering new ideas, thus advancing the pursuit of novel therapeutic strategies to reduce disease risk and or better treat chronic disease including type 2 diabetes, cardiovascular disease and cancer.

Ascitic fluid and serum from rats with acute pancreatitis injure rat pancreatic tissues and alter the expression of heat shock protein 60

Acute pancreatitis (AP) is an inflammatory process in which cytokines and chemokines are involved. After onset, extrapancreatic stimuli can induce the expression of cytokines in pancreatic acinar cells, thereby amplifying this inflammatory loop. To further determine the role and mechanism of irritating agents in the pathogenesis of AP, rat pancreatic tissues were stimulated with ascitic fluid (APa) and serum (APs) from rats with AP or with lipopolysaccharide (LPS). In addition, the alteration of heat shock protein 60 (HSP60) expression was evaluated. Rat pancreas was removed and meticulously snipped to fragments. The snips were cultured for up to 48 h. During this period, the tissue viability as well as amylase and TNF-alpha levels in the supernatant and the HSP60 expression in the pancreatic tissue before and after stimulation by APa, APs, and LPS were assayed time-dependently. At different time-points during the culture, the viability and the amylase activity in the pancreatic tissue remained largely stable. After stimulation with APa, APs, or LPS for 1 h, the pancreatic tissues showed some damage, and this was followed by a sharp decrease in the viability accompanied by increased levels of amylase and TNF-alpha in the culture medium 2 or 4 h after stimulation (p < 0.05). In contrast, both the HSP60 mRNA and protein levels had a relatively high expression in the freshly prepared tissue fragments (0 h). As the culturing period was extended, the expression of HSP60 mRNA decreased only slightly; at the same time, the HSP60 protein levels decreased over a prolonged culture time, significantly so from 12 through 48 h (p < 0.05). After stimulation with APs, APa, or LPS, both the expression of HSP60 mRNA and protein in the tissue fragments increased slightly at 1 h and decreased significantly thereafter at 2 and 4 h (p < 0.05). APa, APs, or LPS induce injuries on isolated pancreatic tissues, accompanied by an altered HSP60 expression pattern in a time-dependent manner.

The expression of p53-regulated genes in human cultured lymphoblastoid TSCE5 and WTK1 cell lines during spaceflight

PURPOSE

The space environment contains two major biologically significant influences; space radiations and microgravity. The 53 kDa tumour suppressor protein (p53) plays a role as a guardian of the genome through the activity of p53-centered signal transduction pathways. The aim of this study was to clarify the biological effects of space radiations, microgravity, and the space environment on the gene expression of p53-regulated genes.

MATERIALS AND METHODS

Space experiments were performed with two human cultured lymphoblastoid cell lines; one line (TSCE5) bears a wild-type p53 gene status, and another line (WTK1) bears a mutated p53 gene status. Under one gravity or microgravity conditions, the cells were grown in the cell biology experimental facility (CBEF) of the International Space Station for 8 days without experiencing stress during launching and landing because the cells were frozen during these periods. Ground control samples also were cultured for 8 days in the CBEF on the ground during the spaceflight. Gene expression was analysed using an Agilent Technologies 44 k whole human genome microarray DNA chip.

RESULTS

p53-dependent up-regulated gene expression was observed for 111, 95, and 328 genes and p53-dependent down-regulated gene expression was found for 177, 16, and 282 genes after exposure to space radiations, to microgravity, and to both, respectively.

CONCLUSIONS

The data provide the p53-dependent regulated genes by exposure to radiations and/or microgravity during spaceflight. Our expression data revealed genes that might help to advance the basic space radiation biology.

αA-Crystallin associates with α6 integrin receptor complexes and regulates cellular signaling

α-Crystallins are small heat-shock proteins important to lens transparency that provide the lens with its refractive properties. In their role as molecular chaperones, these crystallins also prevent protein aggregation, affect cytoskeletal remodeling, enhance resistance to cell stress, and provide lens cells with protection against apoptosis. While many of the functions assigned to αA-crystallin are attributable to its presence in the cytoplasm of lens cells, αA-crystallin also has been detected at the lens plasma membrane. However, how αA-crystallin becomes linked to the plasma membrane or what its functions are at this site has remained unknown. In this study, we examined the mechanisms by which αA-crystallin becomes associated with the lens membrane, focusing specifically on its interaction with membrane receptors, and the differentiation-specificity of these interactions. We also determined how the long-term absence of αA-crystallin alters receptor-linked signaling pathways. αA-crystallin association with membrane receptors was determined by co-immunoprecipitation analysis; its membrane localization was examined by confocal imaging; and the effect of αA-crystallin loss-of-function on the activation state of signaling molecules in pathways linked to membrane receptors was determined by immunoblot analysis. The results show that, in lens epithelial cells, plasma membrane αA-crystallin was primarily localized to apicolateral borders, reflecting the association of αA-crystallin with E-cadherin complexes. These studies also provide the first evidence that αA-crystallin maintained its association with the plasma membrane in lens cortical fiber cells, where it was localized to lateral interfaces, and further show that this association was mediated, in part, by αA-crystallin interaction with α6 integrin receptor complexes. We report that the absence of αA-crystallin led to constitutive activation of the stress kinases p38 and JNK, classical inducers of apoptotic cell death, and the loss of the phospho-Bad pro-survival signal, effects that were greatest in differentiating lens fiber cells. Concurrent with this, activation of FAK and ERK kinases was increased, demonstrating that these receptor-linked pathways also were dysregulated in the absence of αA-crystallin. These data link αA-crystallin plasma membrane association to its differentiation-state-specific interaction with E-cadherin and α6 integrin receptor complexes. The changes in cell signaling in αA-crystallin-null lenses suggest that dysregulation of receptor-linked cell-signaling pathways that accompany the failure of αA-crystallin to associate with membrane receptors may be responsible for the induction of apoptosis. The observed changes in lens cell signaling likely reflect long-term functional adaptations to the absence of the αA-crystallin chaperone/small heat-shock protein.

Transcriptome responses to heat stress in the nucleated red blood cells of the rainbow trout (Oncorhynchus mykiss)

The retention of a nucleus in the mature state of fish red blood cells (RBCs) and the ability to easily collect and manipulate blood in nonterminal experiments make blood an ideal tissue on which to study the cellular stress response in fish. Through the use of the cGRASP 16K salmonid microarray, we investigated differences in RBC global gene transcription in fish held under control conditions (11°C) and exposed to heat stress (1 h at 25°C followed by recovery at 11°C). Repeated blood sampling (via a dorsal aorta cannula) enables us to examine the individual stress response over time. Samples were taken preheat stress (representing individual control) and at 4 and 24 h postheat stress (representing early and late transcriptional regulation). Approximately 3,000 microarray features had signal above threshold when hybridized with RBC RNA-derived targets, and cannulation did not have a detectable effect on RBC mRNA expression at the investigated time points. Genes involved in the stress response, immune response, and apoptosis were among those showing the highest dysregulation during both early and late transcriptional regulation. Additionally, genes related to the differentiation and development of blood cells were transcriptionally upregulated at the 24 h time point. This study provides a broader understanding of the mechanisms underpinning the stress response in fish and the discovery of novel genes that are regulated in a stress specific manner. Moreover, salmonid transcripts that are consistently dysregulated in blood in response to heat stress are potential candidates of nonlethal biomarkers of exposure to this particular stressor.

Binding of a small molecule at a protein-protein interface regulates the chaperone activity of hsp70-hsp40

Heat shock protein 70 (Hsp70) is a highly conserved molecular chaperone that plays multiple roles in protein homeostasis. In these various tasks, the activity of Hsp70 is shaped by interactions with co-chaperones, such as Hsp40. The Hsp40 family of co-chaperones binds to Hsp70 through a conserved J-domain, and these factors stimulate ATPase and protein-folding activity. Using chemical screens, we identified a compound, 115-7c, which acts as an artificial co-chaperone for Hsp70. Specifically, the activities of 115-7c mirrored those of a Hsp40; the compound stimulated the ATPase and protein-folding activities of a prokaryotic Hsp70 (DnaK) and partially compensated for a Hsp40 loss-of-function mutation in yeast. Consistent with these observations, NMR and mutagenesis studies indicate that the binding site for 115-7c is adjacent to a region on DnaK that is required for J-domain-mediated stimulation. Interestingly, we found that 115-7c and the Hsp40 do not compete for binding but act in concert. Using this information, we introduced additional steric bulk to 115-7c and converted it into an inhibitor. Thus, these chemical probes either promote or inhibit chaperone functions by regulating Hsp70-Hsp40 complex assembly at a native protein-protein interface. This unexpected mechanism may provide new avenues for exploring how chaperones and co-chaperones cooperate to shape protein homeostasis.

Role of lipid peroxidation in cellular responses to D,L-sulforaphane, a promising cancer chemopreventive agent

D,L-sulforaphane (SFN), a synthetic analogue of the broccoli-derived l-isomer, is a highly promising cancer chemopreventive agent substantiated by inhibition of chemically induced cancer in rodents and prevention of cancer development and distant site metastasis in transgenic mouse models of cancer. SFN is also known to inhibit growth of human cancer cells in association with cell cycle arrest and reactive oxygen species-dependent apoptosis, but the mechanism of these cellular responses to SFN exposure is not fully understood. Because 4-hydroxynonenal (4-HNE), a product of lipid peroxidation (LPO), the formation of which is regulated by hGSTA1-1, assumes a pivotal role in oxidative stress-induced signal transduction, we investigated its contribution in growth arrest and apoptosis induction by SFN using HL60 and K562 human leukemic cell lines as a model. The SFN-induced formation of 4-HNE was suppressed in hGSTA1-1-overexpressing cells, which also acquired resistance to SFN-induced cytotoxicity, cell cycle arrest, and apoptosis. While resistance to SFN-induced cell cycle arrest by ectopic expression of hGSTA1-1 was associated with changes in levels of G2/M regulatory proteins, resistance to apoptosis correlated with an increased Bcl-xL/Bax ratio, inhibition of nuclear translocation of AIF, and attenuated cytochrome c release in cytosol. The hGSTA1-1-overexpressing cells exhibited enhanced cytoplasmic export of Daxx, nuclear accumulation of transcription factors Nrf2 and HSF1, and upregulation of their respective client proteins, gamma-GCS and HSP70. These findings not only reveal a central role of 4-HNE in cellular responses to SFN but also reaffirm that 4-HNE contributes to oxidative stress-mediated signaling.

Biochemical and biophysical characterization of the Mg2+-induced 90-kDa heat shock protein oligomers

The 90-kDa heat shock protein (Hsp90) is involved in the regulation and activation of numerous client proteins essential for diverse functions such as cell growth and differentiation. Although the function of cytosolic Hsp90 is dependent on a battery of cochaperone proteins regulating both its ATPase activity and its interaction with client proteins, little is known about the real Hsp90 molecular mechanism. Besides its highly flexible dimeric state, Hsp90 is able to self-oligomerize in the presence of divalent cations or under heat shock. In addition to dimers, oligomers exhibit a chaperone activity. In this work, we focused on Mg(2+)-induced oligomers that we named Type I, Type II, and Type III in increasing molecular mass order. After stabilization of these quaternary structures, we optimized a purification protocol. Combining analytical ultracentrifugation, size exclusion chromatography coupled to multiangle laser light scattering, and high mass matrix-assisted laser desorption/ionization time of flight mass spectrometry, we determined biochemical and biophysical characteristics of each Hsp90 oligomer. We demonstrate that Type I oligomer is a tetramer, and Type II is an hexamer, whereas Type III is a dodecamer. These even-numbered structures demonstrate that the building brick for oligomerization is the dimer up to the Type II, whereas Type III probably results from the association of two Type II. Moreover, the Type II oligomer structure, studied by negative stain transmission electron microscopy tomography, exhibits a "nest-like" shape that forms a "cozy chaperoning chamber" where the client protein folding/protection could occur.

Effect of acute exposure to cadmium on the expression of heat-shock and hormone-nuclear receptor genes in the aquatic midge Chironomus riparius

Cadmium is a widespread and highly toxic pollutant of particular ecotoxicological relevance for aquatic ecosystems where it accumulates. To identify biomarkers for ecotoxicity monitoring, the effect of cadmium on the expression of different genes related to the stress response as well as to the ecdysone hormone-signalling pathway was studied in the aquatic larvae of Chironomus riparius (Diptera, Chironomidae), a standard test organism in aquatic toxicology testing. Reverse Transcription Polymerase Chain Reaction (RT-PCR) was used to evaluate the effects of acute and short-term cadmium exposures (10mM CdCl(2), 12h and 24h) on the expression of hsp70, hsc70, hsp90 and hsp40 genes, as well as on that of the ecdysone hormonal-receptor genes (EcR and usp). A significant 3-fold increase in the level of hsp70 gene transcripts was induced by the treatment, whereas neither the other stress genes tested (hsp90 and hsp40) nor the constitutive form of hsp70, hsc70, was affected in the larvae exposed to cadmium. These results show that hsp70 is differentially activated to other environmentally regulated heat-shock genes, and constitutes a biomarker of exposure to this toxic metal. In addition, we also found that cadmium is able to alter the expression of the ecdysone receptor gene (EcR), whose mRNA level is significantly increased whereas usp levels remained unaltered. This finding, evidenced for the first time in invertebrates, supports the view that cadmium has the ability to mimic the effect of the hormone by the activation of the ecdysone nuclear receptor, which may partly explain the endocrine disruption capability that has been previously suggested for this toxic metal. Our research adds to the growing evidence implicating heavy metals, and cadmium in particular, as potential endocrine disruptive agents and may have significant implications for ecological risk assessment of endocrine-disrupting compounds in invertebrates.

Mortalin inhibitors sensitize K562 leukemia cells to complement-dependent cytotoxicity

Mortalin, the mitochondrial hsp70, is a vital constitutively expressed heat shock protein. Its elevated expression has been correlated with malignant transformation and poor cancer prognosis. Cancer cells exhibit increased resistance to complement-dependent cytotoxicity, partly due to their capacity to eliminate the complement membrane attack complex (MAC) from their cell surface. As we have previously reported, mortalin and the complement membrane attack complexes are released in membrane vesicles from complement attacked cells. As shown here, knock down of mortalin with specific siRNA reduces MAC elimination and enhances cell sensitivity to MAC-induced cell death. Similar results were obtained with MKT-077, a cationic rhodacyanine dye that inhibits mortalin. Treatment of human erythroleukemia K562 and colorectal carcinoma HCT116 cells with MKT-077 sensitizes them to cell death mediated by MAC but not by streptolysin O. Pre-treatment of cells with MKT-077 also reduces the extent of MAC-mortalin vesiculation following a sublytic complement attack. In the presence of MKT-077, the direct binding of mortalin to complement C9, the major MAC component, is inhibited. The tumor suppressor protein p53 is a known mortalin client protein. The effect of MKT-077 on complement-mediated lysis of HCT116 p53(+/+) and p53(-/-) cells was found to be independent on the presence of p53. Our results also demonstrate that recombinant human mortain inhibits complement-mediated hemolysis of rabbit erythrocytes as well as zinc-induced C9 polymerization. We conclude that mortalin supports cancer cell resistance to complement-dependent cytotoxicity and propose consideration of mortalin as a novel target for cancer adjuvant immunotherapy.

The 90-kDa heat shock protein Hsp90 protects tubulin against thermal denaturation

Hsp90 and tubulin are among the most abundant proteins in the cytosol of eukaryotic cells. Although Hsp90 plays key roles in maintaining its client proteins in their active state, tubulin is essential for fundamental processes such as cell morphogenesis and division. Several studies have suggested a possible connection between Hsp90 and the microtubule cytoskeleton. Because tubulin is a labile protein in its soluble form, we investigated whether Hsp90 protects it against thermal denaturation. Both proteins were purified from porcine brain, and their interaction was characterized in vitro by using spectrophotometry, sedimentation assays, video-enhanced differential interference contrast light microscopy, and native polyacrylamide gel electrophoresis. Our results show that Hsp90 protects tubulin against thermal denaturation and keeps it in a state compatible with microtubule polymerization. We demonstrate that Hsp90 cannot resolve tubulin aggregates but that it likely binds early unfolding intermediates, preventing their aggregation. Protection was maximal at a stoichiometry of two molecules of Hsp90 for one of tubulin. This protection does not require ATP binding and hydrolysis by Hsp90, but it is counteracted by geldanamycin, a specific inhibitor of Hsp90.

Physiological adaptations of stressed fish to polluted environments: role of heat shock proteins

Fish are subjected to a wide variety of environmental stressors. Stressors affect fish at all life stages and the stress-specific responses that occur at the biochemical and physiological levels affect the overall health and longevity of such animals. In this review, the organ-specific alterations in fish that inhabit polluted environments are addressed in detail. Fish,like other vertebrates, have evolved strategies to counteract stress-mediated effects. Among the key strategies that fish have developed is the induction of HSPs. The primary functions of HSPs are to promote the proper folding or refolding of proteins, to prevent potentially damaging interactions with proteins, and aiding in the disassembly of formations of protein aggregates. Stress, a state of unbalanced tissue oxidation, causes a general disturbance in the cellular antioxidant and redox balance and evokes HSP70 overexpression. Distinct families of HSPs have diverse physiological functions, and their induction, which is regulated at the transcriptional level, is mediated by the activation of heat shock factors. Interestingly, HSPs also interact with a wide variety of signaling molecules that modulate stress-mediated apoptotic effects. Hence, HSP induction is of major importance for maintenance of cell homeostasis. HSP-mediated adaptation processes are regarded as a fundamental protective mechanism that decreases cellular sensitivity to damaging events. Thus, the adaptive expression of HSPs is a protective response that helps combat stress-induced conformational damage to proteins. Additional research is needed to gain further information on the functional significance and role of individual HSPs and to enhance the understanding of the molecular mechanisms by which they act. In addition, field studies are needed to allow comprehensive evaluation of the potential use of HSPs as biomarkers for environmental monitoring. Furthermore, the expression of HSPs in fish fluctuates in response to seasonal variation. Because HSPs serves as a tool for assessing the stressed state of individuals and/or populations, the impact of seasonal influences on constitutive and inducible factors of these proteins should also be elucidated. Such research will lead to a fundamental improvement in the understanding of the functional role of HSPs in response to natural environmental changes and may allow correlation of the action of HSPs at the molecular level with the whole organismal stress response, which, so far, remains unexplained.

A novel, small molecule inhibitor of Hsc70/Hsp70 potentiates Hsp90 inhibitor induced apoptosis in HCT116 colon carcinoma cells

PURPOSE

The anti-apoptotic function of the 70 kDa family of heat shock proteins and their role in cancer is well documented. Dual targeting of Hsc70 and Hsp70 with siRNA induces proteasome-dependent degradation of Hsp90 client proteins and extensive tumor specific apoptosis as well as the potentiation of tumor cell apoptosis following pharmacological Hsp90 inhibition.

METHODS

We have previously described the discovery and synthesis of novel adenosine-derived inhibitors of the 70 kDa family of heat shock proteins; the first inhibitors described to target the ATPase binding domain. The in vitro activity of VER-155008 was evaluated in HCT116, HT29, BT474 and MDA-MB-468 carcinoma cell lines. Cell proliferation, cell apoptosis and caspase 3/7 activity was determined for VER-155008 in the absence or presence of small molecule Hsp90 inhibitors.

RESULTS

VER-155008 inhibited the proliferation of human breast and colon cancer cell lines with GI(50)s in the range 5.3-14.4 microM, and induced Hsp90 client protein degradation in both HCT116 and BT474 cells. As a single agent, VER-155008 induced caspase-3/7 dependent apoptosis in BT474 cells and non-caspase dependent cell death in HCT116 cells. VER-155008 potentiated the apoptotic potential of a small molecule Hsp90 inhibitor in HCT116 but not HT29 or MDA-MB-468 cells. In vivo, VER-155008 demonstrated rapid metabolism and clearance, along with tumor levels below the predicted pharmacologically active level.

CONCLUSION

These data suggest that small molecule inhibitors of Hsc70/Hsp70 phenotypically mimic the cellular mode of action of a small molecule Hsp90 inhibitor and can potentiate the apoptotic potential of a small molecule Hsp90 inhibitor in certain cell lines. The factors determining whether or not cells apoptose in response to Hsp90 inhibition or the combination of Hsp90 plus Hsc70/Hsp70 inhibition remain to be determined.

The atheroprotective properties of Hsp70: a role for Hsp70-endothelial interactions?

Although heat shock (stress) proteins are typically regarded as being exclusively intracellular molecules, it is now apparent that they can be released from cells in the absence of cellular necrosis. We and others have reported the presence of Hsp60 (HSPD1) and Hsp70 (HSPA1A) in the circulation of normal individuals and our finding that increases in carotid intima-media thicknesses (a measure of atherosclerosis) in subjects with hypertension at a 4-year follow-up are less prevalent in those having high serum Hsp70 (HSPA1A) levels at baseline suggests that circulating Hsp70 (HSPA1A) has atheroprotective effects. Given that circulating Hsp70 (HSPA1A) levels can be in the range which has been shown to elicit a number of biological effects in vitro, and our preliminary findings that Hsp70 (HSPA1A) binds to and is internalised by human endothelial cell populations, we speculate on the mechanisms that might be involved in the apparent atheroprotective properties of this protein.

Functional characterization of orchardgrass endoplasmic reticulum-resident Hsp90 (DgHsp90) as a chaperone and an ATPase

Hsp90 proteins are essential molecular chaperones regulating multiple cellular processes in distinct subcellular organelles. In this study, we report the functional characterization of a cDNA encoding endoplasmic reticulum (ER)-resident Hsp90 from orchardgrass (DgHsp90). DgHsp90 is a 2742bp cDNA with an open reading frame predicted to encode an 808 amino acid protein. DgHsp90 has a well conserved N-terminal ATPase domain and a C-terminal Hsp90 domain and ER-retention motif. Expression of DgHsp90 increased during heat stress at 35 degrees C or H(2)O(2) treatment. DgHsp90 also functions as a chaperone protein by preventing thermal aggregation of malate dehydrogenase (EC 1.1.1.37) and citrate synthase (EC 2.3.3.1). The intrinsic ATPase activity of DgHsp90 was inhibited by geldanamycin, an Hsp90 inhibitor, and the inhibition reduced the chaperone activity of DgHsp90. Yeast cells overexpressing DgHsp90 exhibited enhanced thermotolerance.

Quality control against misfolded proteins in the cytosol: a network for cell survival

Misfolded proteins are toxic to cells and the accumulation of toxic species can lead to protein misfolding diseases, such as neurodegenerative disorders. The toxicity of misfolded proteins is thought to result from the presence of exposed hydrophobic surfaces, which mediate unnecessary binding to normal proteins, interrupting essential interactions between cellular proteins. To prevent toxicity, quality control systems monitor protein folding and remove misfolded species in the cytosol. Molecular chaperones recognize and mask hydrophobic surfaces of misfolded monomers, and transfer them to the ubiquitin-proteasome system and chaperone-mediated autophagy. To eliminate soluble aggregates of misfolded proteins, the macroautophagy-lysosome system is thought to degrade proteasome-resistant toxic species. In addition, the microtubule-dependent transport system sequesters soluble oligomers/aggregates into inclusion bodies. These systems are regulated by stress-inducible transcription factors, cochaperones and other cofactors for the effective removal of toxic monomers and oligomers. This review explores the roles of protein quality control pathways and networks that control quality control activities in the cytosol, particularly focusing on recent progress in this field.

Crosstalk between Hsp70 molecular chaperone, lysosomes and proteasomes in autophagy-mediated proteolysis in human retinal pigment epithelial cells

The pathogenesis of age-related macular degeneration involves chronic oxidative stress, impaired degradation of membranous discs shed from photoreceptor outer segments and accumulation of lysosomal lipofuscin in retinal pigment epithelial (RPE) cells. It has been estimated that a major part of cellular proteolysis occurs in proteasomes, but the importance of proteasomes and the other proteolytic pathways including autophagy in RPE cells is poorly understood. Prior to proteolysis, heat shock proteins (Hsps), agents that function as molecular chaperones, attempt to refold misfolded proteins and thus prevent the accumulation of cytoplasmic protein aggregates. In the present study, the roles of the Hsp70 molecular chaperone and proteasomal and lysosomal proteolytic pathways were evaluated in human RPE cells (ARPE-19). The Hsp70 and ubiquitin protein levels and localization were analysed by Western blotting and immunofluorescense. Confocal and transmission electron microscopy were used to detect cellular organelles and to evaluate the morphological changes. Hsp70 levels were modulated using RNA interference and overexpression techniques. Cell viability was measured by colorimetric assay. The proteasome inhibitor MG-132 evoked the accumulation of perinuclear aggregates positive for Hsp70, ubiquitin-protein conjugates and the lysosomal membrane protein LAMP-2. Interestingly, the hsp70 mRNA depletion significantly increased cell death in conjunction with proteasome inhibition. We found that the accumulation of lysosomes was reversible: a cessation of proteasome inhibition led to clearance of the deposits via a mechanism believed to include autophagy. The molecular chaperone Hsp70, proteasomes and autophagy have an important regulatory role in the protein turnover of human RPE cells and may thus open new avenues for understanding degenerative processes in retinal cells.

c-myb has a character of oxidative stress resistance in aged human diploid fibroblasts: regulates SAPK/JNK and Hsp60 pathway consequently

This study examined whether c-myb acts as a survival molecule in aged cells. A previous in vitro ageing model suggested that aged cells have a higher cell capacity for survival after exposure to oxidative stress, which involves blockage of the translocation of Hsp60 from the mitochondria to the cytoplasm followed by SAPK/JNK inactivation, than young cells. In human diploid fibroblasts (HDFs), c-myb expression increased gradually with ageing, and this increase had a significant influence on the cell survival capacity after exposure to oxidative stress. To clarify the role of c-myb in oxidative stress, young cells under 21 passages, which lacked c-myb expression, were transfected with adenovirus-mediated c-myb for express c-myb. These c-myb-over-expressed young cells showed increased cell viability upon exposure to oxidative stress to a similar extent to that of the aged cells. In addition, these c-myb-over-expressed young cells did not exhibit SAPK/JNK activation, Hsp60 displacement and cytochrome C release, as was observed in aged cells. The aged cells that had c-myb suppressed using siRNA c-myb showed reduced cell viability and increased apoptosis in a manner to that observed in young cells. From this study, c-myb blocked SAPK/JNK and Hsp60 translocation upon exposure to oxidative stress. This result suggests that c-myb might act as a modulator of cell survival in the ageing process by suppressing apoptosis in aged cells.

Characterization of a recombinant adenovirus vector encoding heat-inducible feline interleukin-12 for use in hyperthermia-induced gene-therapy

Interleukin-12 (IL-12) is a pro-inflammatory cytokine that has shown great promise as a therapeutic agent in experimental models of infectious disease and cancer. However, it is also a highly toxic molecule and for that reason has not been accepted readily into the clinic. A replication-deficient adenoviral vector was designed to deliver the feline interleukin-12 gene into tumour cells. The interleukin-12 gene has been placed under control of a heat inducible promoter, human heat shock promoter 70b, with the intent of spatially and temporally controlling the expression of IL-12, thus limiting its toxicity. In vitro, the transfection efficiency of the adenoviral vector, the effect of multiplicity of infection and the production of biologically active feline IL-12 were studied in the infected cells in response to a range of temperatures. This adenoviral vector will be a useful tool to examine the effects of intra-tumoural IL-12 delivery in a spontaneously occurring feline soft tissue sarcoma model.

Regulation of HSP70 on activating macrophages using PDT-induced apoptotic cells

Although anti-tumor immunological responses have been mainly associated with necrosis, apoptosis-associated immune responses have been recently suggested as well. In this study, we investigated anti-tumor immune responses and regulatory mechanisms of HSP70 using apoptotic cells induced by photodynamic therapy (PDT). The relationships between HSP70 release, HSP70 translocation and macrophage responses were studied using confocal fluorescence microscopy, FACS and ELISA. Macrophages incubated with apoptotic cells as well as necrotic tumor cells showed a high level of TNFalpha secretion. Apoptotic cells but not the apoptotic cell supernatants induced TNFalpha secretion. During both necrosis and apoptosis processes, the TNFalpha production was diminished drastically when HSP70 or TLR-2 was inhibited. After the PDT treatment, cytoplasmic HSP70 was released from the necrotic cells, while HSP70 rapidly translocated to the surface of the apoptotic cells. Furthermore, the TNFalpha secretion and the tumor cytotoxicity of splenocytes from mice immunized with apoptotic cells appeared similar to that of splenocytes immunized with necrotic cells. Our in vitro and in vivo results show that apoptosis can potentially have higher impact in inducing immunological responses, hence clarifying the immunological regulatory mechanisms of HSP70 under cell apoptosis and necrosis induced by PDT treatment. These findings could lead to an optimal PDT treatment based on immunological responses.

The molecular chaperone heat shock protein-90 positively regulates rotavirus infectionx

Rotaviruses are the major cause of severe dehydrating gastroenteritis in children worldwide. In this study, we report a positive role of cellular chaperone Hsp90 during rotavirus infection. A highly specific Hsp90 inhibitor, 17-allylamono-demethoxygeldanamycin (17-AAG) was used to delineate the functional role of Hsp90. In MA104 cells treated with 17-AAG after viral adsorption, replication of simian (SA11) or human (KU) strains was attenuated as assessed by quantitating both plaque forming units and expression of viral genes. Phosphorylation of Akt and NFkappaB observed 2-4 hpi with SA11, was strongly inhibited in the presence of 17-AAG. Direct Hsp90-Akt interaction in virus infected cells was also reduced in the presence of 17-AAG. Anti-rotaviral effects of 17-AAG were due to inhibition of activation of Akt that was confirmed since, PI3K/Akt inhibitors attenuated rotavirus growth significantly. Thus, Hsp90 regulates rotavirus by modulating cellular signaling proteins. The results highlight the importance of cellular proteins during rotavirus infection and the possibility of targeting cellular chaperones for developing new anti-rotaviral strategies.

Amyloid precursor protein, heat-shock proteins, and Bcl-2 form a complex in mitochondria and modulate mitochondria function and apoptosis in N2a cells

Neurons that degenerate in the brains of persons with Alzheimer's disease accumulate mitochondrial amyloid precursor protein (APP), which is thought to negatively affect mitochondrial function and cellular homeostasis. Because proteins that enter mitochondria require assistance from chaperone proteins, we hypothesized that heat-shock proteins (HSPs) help accumulate APP in mitochondria. We found that APP overexpression in N2a cells (APP cells) did not elicit mitochondrial dysfunction. Because cerebral hypoperfusion-associated energy deficiency is an important etiology for Alzheimer's disease, we also challenged the cells with serum starvation. APP/HSP/Bcl-2 complexes formed within the mitochondria of serum-starved APP cells, but not control cells. Mitochondria containing APP/HSP/Bcl-2 complexes induced apoptosis. We hypothesize that APP/HSP/Bcl-2 complexes diminish the functional capacities of HSPs and Bcl-2, which leads to mitochondrial injury and apoptosis.

Regulation of heat shock gene transcription in neuronal cells

The heat shock protein (HSP) molecular chaperones are the primary cellular defense against damage to the proteome, initiating refolding of denatured proteins and regulating degradation after severe protein damage. Many neurodegenerative disorders involve aberrant protein folding and protein damage, which accumulates in an age-dependent manner. Ageing is associated with the decrease in activity of the heat shock transcription factors (HSF) that regulate HSP gene transcription. Neuronal cells seem particularly vulnerable in this sense as HSF activity and HSP expression are relatively weak in such cells and motor neurons appear to require input of HSP secreted from adjacent glial cells to maintain adequate molecular chaperone levels. It may be significant that motor neurons have been shown to be the sensitive cells in the ageing of Drosophila and C. elegans and that these organisms may acquire extended lifespans with over-expression of small heat shock proteins and HSF1. HSF1 transcriptional activity has been discussed in neuronal cells, concentrating on the regulation and activity of HSF1 and HSF2 and their role in HSP expression, during neurodegenerative diseases and as mediators of cell survival.

Extremely Low-Frequency Magnetic Field Exposure and Protection Against UV-Induced Death in Chicken Embryos

We report on a study where 4-day old chicken embryos from different flocks were pre-treated with 50 Hz magnetic fields (MF) prior to a 60-min UV-C exposure (1.7 mW/cm(2)) to investigate the possible protective effect of MF exposure on UV-induced embryo death. Different flux densities (0.010, 0.025, 0.050, 0.10, and 0.20 mT), field directions (vertical and horizontal), as well as MF exposure times (10, 20, and 60 min) were employed. We did not find any significant effects by MF exposure, irrespective of exposure time, flux density, or field direction on the survival of embryos. Neither could we find any flock dependency on sensitivity to MF exposure.

Effect of GSM-900 and -1800 signals on the skin of hairless rats. III: Expression of heat shock proteins

PURPOSE

We previously reported the inability of Global System for Mobile communication (GSM) signals at 900 (GSM-900) and 1800 (GSM-1800) MegaHertz (MHz) to induce morphological and physiological changes in epidermis of Hairless rats. The present work aimed at investigating heat shock proteins (HSP) expression--as a cellular stress marker--in the skin of Hairless rats exposed to GSM-900 and -1800 signals.

MATERIALS AND METHODS

We studied the expression of the Heat-shock cognate (Hsc) 70, and the inducible forms of the Heat-shock proteins (Hsp) 25 and 70. Rat skin was locally exposed using loop antenna and restrain rockets to test several Specific Absorption Rates (SAR) and exposure durations: (i) single exposure: 2 hours at 0 and 5 W/kg; (ii) repeated exposure: 2 hours per day, 5 days per week, for 12 weeks, at 0, 2.5, and 5 W/kg. HSP expression was detected on skin slices using immunolabeling in the epidermal area.

RESULTS

Our data indicated that neither single nor repeated exposures altered HSP expression in rat skin, irrespective of the GSM signal or SAR considered.

CONCLUSIONS

Under our experimental conditions (local SAR < 5 W/kg), there was no evidence that GSM signals alter HSP expression in rat skin.

Cadmium-induced alterations of gene expression in human cells

We have reported the changes in gene expression in human HeLa cells exposed to a low concentration (5μM) of Cd. In the present study, cells exposed to a higher concentration of Cd were analyzed using a DNA microarray with 9182 human cDNA probes, in an attempt to obtain a comprehensive view on the biological effects of Cd. After a 6h exposure to 50μM Cd, 48 genes were up-regulated 2.5-fold or greater and 14 genes were down-regulated to 40% or less. Marked up-regulation of genes coding for metallothioneins, anti-oxidant proteins, and heat shock proteins was observed. Cd appeared to repress cell proliferation by modulating genes involved in multiple pathways. Cd also affected a number of genes related to apoptosis. Interestingly, it appeared that a series of genes were regulated to accelerate the intrinsic pathway of apoptosis, while others were directed to suppress the extrinsic pathway. Of these, rapid and transient induction of the TR3 gene was noted as a possible key process in Cd-induced apoptosis. Effects on several genes that may reflect mechanistic backgrounds of Cd toxicity were also observed. The present study disclosed a complex pleiotypic response of human cells to Cd, which was composed of a variety of changes in gene expression directed to defense, growth arrest, recovery from damage, apoptosis and so on.

Low concentration of GA activates a preconditioning response in HepG2 cells during oxidative stress-roles of Hsp90 and vimentin

Oxidative stress can be a significant cause of cell death and apoptosis. We performed studies in HepG2 cells to explore whether prior exposure to oxidative stress ("oxidative preconditioning") and geldanamycin (GA) treatment can protect the cell from damage caused by subsequent oxidative insults. The cells were treated with 10 nM GA for 24 h before oxidative stress. Oxidative preconditioning was achieved by 2 h exposures to H(2)O(2) (50 microM) separated by a 10-h recovery period in normal culture medium. Oxidative stress was induced by exposure to 500 microM H(2)O(2) for 24 h. The effects of GA and oxidative preconditioning were investigated on the formation of Hsp90, vimentin, insoluble vimentin aggregates, and cleavage of vimentin in a cell culture model of oxidative stress. GA treatment leads to enhanced expression of Hsp90 and vimentin and to inhibition of vimentin protein aggregation. Similar results were obtained by oxidative preconditioning. It is confirmed that low concentrations of GA protected HepG2 cells from subsequent oxidative stress by increasing the levels of Hsp90 and by alleviating the extent of cell apoptosis induced by oxidative stress, which is similar to oxidative preconditioning. However, in contrast to preconditioning, GA treatment obviously changed binding activity of Hsp90 to vimentin cleavages. All the above indicated that low concentrations of GA treatment triggered cell protection from oxidative stress. Both the level of Hsp90 and its ability to bind with vimentin were changed by low concentrations of GA and might contribute to oxidative stress protection.

Rescue of atypical protein kinase C in epithelia by the cytoskeleton and Hsp70 family chaperones

Atypical PKC (PKC iota) is a key organizer of cellular asymmetry. Sequential extractions of intestinal cells showed a pool of enzymatically active PKC iota and the chaperone Hsp70.1 attached to the apical cytoskeleton. Pull-down experiments using purified and recombinant proteins showed a complex of Hsp70 and atypical PKC on filamentous keratins. Transgenic animals overexpressing keratin 8 displayed delocalization of Hsp70 and atypical PKC. Two different keratin-null mouse models, as well as keratin-8 knockdown cells in tissue culture, also showed redistribution of Hsp70 and a sharp decrease in the active form of atypical PKC, which was also reduced by Hsp70 knockdown. An in-vitro turn motif rephosphorylation assay indicated that PKC iota is dephosphorylated by prolonged activity. The Triton-soluble fraction could rephosphorylate PKC iota only when supplemented with the cytoskeletal pellet or filamentous highly purified keratins, a function abolished by immunodepletion of Hsp70 but rescued by recombinant Hsp70. We conclude that both filamentous keratins and Hsp70 are required for the rescue rephosphorylation of mature atypical PKC, regulating the subcellular distribution and steady-state levels of active PKC iota.

Disc cell clusters in pathological human intervertebral discs are associated with increased stress protein immunostaining

Intervertebral disc (IVD) cells within the annulus fibrosus (AF) and nucleus pulposus (NP) maintain distinct functional extracellular matrices and operate within a potentially noxious and stressful environment. How disc cells respond to stress and whether stress is responsible for triggering degeneration is unknown. Disc cell proliferation and cluster formation are most marked in degenerate IVDs, possibly indicating attempts at matrix repair. In other tissues, stress proteins increase rapidly after stress protecting cell function and, although implicated in degeneration of articular cartilage, have received little attention in degenerative IVD pathologies. We have compared the distribution of stress protein immunolocalization in pathological and control IVDs. Disc tissues were obtained at surgery from 43 patients with degenerative disc disease (DDD) and herniation, and 12 controls at postmortem. Tissues were immunostained with a polyclonal antibody for heat shock factor 1 (HSF-1) and monoclonal antibodies for the heat shock proteins, Hsp27 and Hsp72, using an indirect immunoperoxidase method. Positively stained cells were expressed as a percentage of the total. Cell cluster formation was also assessed. The proportion of cells in clusters was similar in the AF (both 2%) and NP (8 and 9%) of control and DDD samples, whereas in herniated tissues this was increased (AF 12%, NP 14%). Stress antigen staining tended to be more frequent in clustered rather than in single/doublet cells, and this was significant (P < 0.005) in both the AF and NP of herniated discs. Clustered cells, which are most common in herniated discs, may be mounting a protective response to abnormal environmental factors associated with disc degeneration. A better understanding of the stress response in IVD cells may allow its utilization in disc cell therapies.