A novel 40-kDa protein induced by heat shock and other stresses in mammalian and avian cells

Ectopic expression of DnaJ type-I protein homolog of Vigna aconitifolia (VaDJI) confers ABA insensitivity and multiple stress tolerance in transgenic tobacco plants

Reduced crop productivity results from altered plant physiological processes caused by dysfunctional proteins due to environmental stressors. In this study, a novel DnaJ Type-I encoding gene, VaDJI having a zinc finger motif in its C-terminal domain was found to be induced early upon treatment with heat stress (within 5 min) in a heat tolerant genotype of Vigna aconitifolia RMO-40. VaDJI is induced by multiple stresses. In tobacco, ectopic expression of VaDJI reduced ABA sensitivity during seed germination and the early stages of seedling growth of transgenic tobacco plants. Concomitantly, it also improved the ability of transgenic tobacco plants to withstand drought stress by modulating the photosynthetic efficiency, with the transgenic plants having higher Fv/Fm ratios and reduced growth inhibition. Additionally, transgenic plants showed a reduced build-up of H2O2 and lower MDA levels and higher chlorophyll content during drought stress, which attenuated cell damage and reduced oxidative damage. An analysis using the qRT-PCR study demonstrated that VaDJI overexpression is associated with the expression of some ROS-detoxification-related genes and stress-marker genes that are often induced during drought stress responses. These findings suggest a hypothesis whereby VaDJI positively influences drought stress tolerance and ABA signalling in transgenic tobacco, and suggests that it is a potential gene for genetic improvement of drought and heat stress tolerance in crop plants.

Hyper-transcription of heat shock factors and heat shock proteins safeguard caprine cardiac cells against heat stress

The present study was undertaken to document the transcriptional abundance of heat shock factors and heat shock proteins and their role in survivability of caprine cardiac cells during heat stress. Cardiac tissues were collected from different goats (n = 6) and primary cardiac cell culture was done in an atmosphere of 5% CO₂ and 95% air at 38.5 °C. Cardiac cells accomplished 70-75% confluence after 72 h of incubation. Confluent cardiac cells were exposed to heat stress at 42 °C for 0 (control), 20, 60, 100 and 200 min. Quantitative RT-PCR for β2m (internal control), heat shock factors (HSF1, HSF2, HSF4, HSF5), heat shock proteins (HSP10, HSP40), and Caspase-3 was done and their transcriptional abundance was assessed by Pfaffl method. Transcriptional abundance of HSF1, HSF2, and HSF4 did not change at 20 min, increased (P < 0.05) from 60 to 200 min and reached zenith at 200 min of heat exposure. However, transcriptional abundance of HSF5 was gradually escalated (P < 0.05) from 20 to 200 min and registered highest at 200 min of heat exposure. Transcriptional abundance of HSP10 and HSP40 followed an similar pattern like that of HSF5. Transcriptional abundance of Caspase-3 was significantly down-regulated at 200 min of heat exposure. It could be speculated that over-expression of HSFs and HSPs might have reduced Caspase-3 expression at 200 min of heat exposure suggesting their involvement in cardiac cells survival under heat stress. Moreover, hyper-expression of HSFs and HSPs could maintain the integrity and endurance of cardiac tissues of goats under heat stress.

Analysis of lung transcriptome in calves infected with Bovine Respiratory Syncytial Virus and treated with antiviral and/or cyclooxygenase inhibitor

Bovine Respiratory Syncytial virus (BRSV) is one of the major infectious agents in the etiology of the bovine respiratory disease complex. BRSV causes a respiratory syndrome in calves, which is associated with severe bronchiolitis. In this study we describe the effect of treatment with antiviral fusion protein inhibitor (FPI) and ibuprofen, on gene expression in lung tissue of calves infected with BRSV. Calves infected with BRSV are an excellent model of human RSV in infants: we hypothesized that FPI in combination with ibuprofen would provide the best therapeutic intervention for both species. The following experimental treatment groups of BRSV infected calves were used: 1) ibuprofen day 3-10, 2) ibuprofen day 5-10, 3) placebo, 4) FPI day 5-10, 5) FPI and ibuprofen day 5-10, 6) FPI and ibuprofen day 3-10. All calves were infected with BRSV on day 0. Daily clinical evaluation with monitoring of virus shedding by qRT-PCR was conducted. On day10 lung tissue with lesions (LL) and non-lesional (LN) was collected at necropsy, total RNA extracted, and RNA sequencing performed. Differential gene expression analysis was conducted with Gene ontology (GO) and KEGG pathway enrichment analysis. The most significant differential gene expression in BRSV infected lung tissues was observed in the comparison of LL with LN; oxidative stress and cell damage was especially noticeable. Innate and adaptive immune functions were reduced in LL. As expected, combined treatment with FPI and Ibuprofen, when started early, made the most difference in gene expression patterns in comparison with placebo, especially in pathways related to the innate and adaptive immune response in both LL and LN. Ibuprofen, when used alone, negatively affected the antiviral response and caused higher virus loads as shown by increased viral shedding. In contrast, when used with FPI Ibuprofen enhanced the specific antiviral effect of FPI, due to its ability to reduce the damaging effect of prostanoids and oxidative stress.

Co-expression of heat shock protein (HSP) 40 and HSP70 in Pinctada martensii response to thermal, low salinity and bacterial challenges

Heat shock protein (HSP) 40 proteins are a family of molecular chaperones that bind to HSP70 through their J-domain and regulate the function of HSP70 by stimulating its adenosine triphosphatase activity. In the present study, a HSP40 homolog named PmHSP40 was cloned from the hemocytes of pearl oyster Pinctada martensii using EST and rapid amplification of cDNA ends (RACE) techniques. The full-length cDNA of PmHSP40 was 1251 bp in length, which included a 5' untranslated region (UTR) of 75 bp, an open reading frame (ORF) of a 663 bp, and a 3' UTR of 513 bp. The deduced amino acid sequence of PmHSP40 contains a J domain in the N-terminus. In response to thermal and low salinity stress challenges, the expression of PmHSP40 in hemocytes and the gill were inducible in a time-dependent manner. After bacterial challenge, PmHSP40 transcripts in hemocytes increased and peaked at 6 h post injection. In the gill, PmHSP40 expression increased, similar to expression in hemocytes; however, transcript expression of PmHSP40 was significantly up-regulated at 12 h post injection. Furthermore, the transcripts of PmHSP70 showed similar kinetics as that of PmHSP40, with highest induction during thermal, low salinity stress and bacterial challenges. Altogether these results demonstrate that PmHSP40 is an inducible protein under thermal, low salinity and bacterial challenges, suggesting its involvement in both environmental and biological stresses, and in the innate immunity of the pearl oyster.

J protein mutations and resulting proteostasis collapse

Despite a century of intensive investigation the effective treatment of protein aggregation diseases remains elusive. Ordinarily, molecular chaperones ensure that proteins maintain their functional conformation. The appearance of misfolded proteins that aggregate implies the collapse of the cellular chaperone quality control network. That said, the cellular chaperone network is extensive and functional information regarding the detailed action of specific chaperones is not yet available. J proteins (DnaJ/Hsp40) are a family of chaperone cofactors that harness Hsc70 (heat shock cognate protein of 70 kDa) for diverse conformational cellular tasks and, as such, represent novel clinically relevant targets for diseases resulting from the disruption of proteostasis. Here we review incisive reports identifying mutations in individual J protein chaperones and the proteostasis collapse that ensues.

Association of simian virus 40 vp1 with 70-kilodalton heat shock proteins and viral tumor antigens

Proper folding of newly synthesized viral proteins in the cytoplasm is a prerequisite for the formation of infectious virions. The major capsid protein Vp1 of simian virus 40 forms a series of disulfide-linked intermediates during folding and capsid formation. In addition, we report here that Vp1 is associated with cellular chaperones (HSP70) and a cochaperone (Hsp40) which can be coimmunoprecipitated with Vp1. Studies in vitro demonstrated the ATP-dependent interaction of Vp1 and cellular chaperones. Interestingly, viral cochaperones LT and ST were essential for stable interaction of HSP70 with the core Vp1 pentamer Vp1 (22-303). LT and ST also coimmunoprecipitated with Vp1 in vivo. In addition to these identified (co)chaperones, stable, covalently modified forms of Vp1 were identified for a folding-defective double mutant, C49A-C87A, and may represent a "trapped" assembly intermediate. By a truncation of the carboxyl arm of Vp1 to prevent the Vp1 folding from proceeding beyond pentamers, we detected several apparently modified Vp1 species, some of which were absent in cells transfected with the folding-defective mutant DNA. These results suggest that transient covalent interactions with known or unknown cellular and viral proteins are important in the assembly process.

Sodium arsenite retards proliferation of PHA-activated T cells by delaying the production and secretion of IL-2

Arsenic is a metalloid that commonly contaminates drinking water, and is a known human carcinogen. It has been shown that peripheral blood mononuclear cells (PBMCs) from healthy donors treated in vitro with NaAsO(2) and stimulated with phytohemagglutinin (PHA) show a lower proliferation than nontreated cells. We reported previously a reduction in the secretion of IL-2 in NaAsO(2)-treated PBMCs stimulated with PHA, an observation that might explain, in part, the reduction in proliferation. Since arsenic induces cytoskeleton alterations, which in turn may affect protein transport of the cell, we assumed that NaAsO(2) induced an accumulation of IL-2 inside the cells, and thus a reduction in the secretion of IL-2. In order to demonstrate this hypothesis, we assessed the intracellular IL-2 at the single cell level by flow cytometry, and unexpectedly found a reduction in the percentage of IL-2 producing T cells in the presence of NaAsO(2). We tracked the proliferation of T cells by using the 5,6-carboxyfluorescein diacetate succinimidyl ester (CFSE) dye and found that NaAsO(2) slows down the entrance to cell division and delays the proliferation of cells that have already entered the cell cycle. Nevertheless, the expression of the activation molecules, CD25 and CD69, was unaltered. Assessment of the intracellular and secreted IL-2 in kinetic experiments showed that in fact, NaAsO(2) delays the production of IL-2, given that a recovery of both intracellular and secreted IL-2 was detected at 72 h. Evaluation of the cell cycle showed a higher proportion of cells in G(0)/G(1) and a lower proportion in G(2)/M in the presence of NaAsO(2). We thus conclude that NaAsO(2) reduces proliferation of T cells by delaying the production and secretion of IL-2, thus blocking T cells in G(1); as a consequence, the entry to cell cycle and the rounds of cell division are retarded, and a lower proliferation of T cells is hence observed.

Induction of heat shock protein 40 and GrpE mRNAs following transient focal cerebral ischemia in the rat

Cerebral ischemia is associated with the induction of several heat shock proteins (HSPs), but the effects on HSP40 and GrpE are less clear. The present study investigated the induction of Hsp40 and GrpE mRNAs following 30 min of middle cerebral artery occlusion in the rat model. Reverse transcription-polymerase chain reaction (PCR) and in situ hybridization analyses showed significant induction of both mRNAs in the ischemic cortex. These results demonstrate the synergic induction of HSP70 molecular chaperone machinery in cerebral ischemia.

Genomic cloning and promoter analysis of the GAHSP40 gene

The new heat shock protein (GAHSP40), which binds to Gadd34, is a member of the Hsp40 family gene and has a J domain, which is similar to bacterial DNAJ. We have isolated and sequenced the mouse GAHSP40 gene including 1.6 kb of the 5'-flanking region. Primer extension analysis revealed that the transcription initiation site was located 36-bp upstream of the ATG translation initiation codon. In order to identify the heat-responsive regions in the GAHSP40, NIH3T3 cells were transiently transfected with a series of 5' terminus-truncated mutants of the GAHSP40 promoter linked to the luciferase reporter gene. We found that the region of -284 to -184 bp from initiation start site responded to heat shock treatment. By the gel shift analysis, we found the heat shock elements (HSEs) located in this region from -257 to -225. This HSEs has five 5 bp motifs. The transfection studies using HSEs mutant vectors revealed that those 3' two 5 bp motifs are essential for heat responsive transcription.

A DnaJ protein, apobec-1-binding protein-2, modulates apolipoprotein B mRNA editing

Mammalian homologues of DnaJ proteins, also known as Hsp40 proteins, are co-chaperonins that complement Hsp70 chaperone function. Using the yeast two-hybrid system, we cloned an apolipoprotein (apo) B mRNA editing complementation protein, called apobec-1-binding protein-2 (ABBP-2), and found that it is a Class II DnaJ homologue. ABBP-2 binds to apobec-1, the mammalian apoB mRNA editase, via its J domain and neighboring G/F domain. It is a ubiquitously expressed protein, and, by transfection analysis of GFP-ABBP-2, we found that the protein is located in both the nucleus and cytosol of transfected cells, with predominance in the nucleus. Down-regulation of ABBP-2 expression in cultured cells inhibits endogenous apobec-1-mediated apoB mRNA editing. Like other Hsp40 proteins, ABBP-2 binds to Hsp70 and has ATPase-stimulating activity. Apobec-1-mediated apoB mRNA editing activity of in vitro tissue extracts requires the presence of Hsp70/ABBP-2. Although exogenously added ATP is not required for editing activity, removal of the endogenous ATP present in these extracts, which disrupts ABBP-2-Hsp70 interaction, completely inhibits editing. ABBP-2 differs from previously described auxiliary proteins (ABBP-1, ACF, and GRY-RBP) in that it does not contain any RNA recognition motifs. Not only is ABBP-2 required for efficient apoB mRNA editing, this newly discovered apobec-1-binding protein may help determine the subcellular distribution and trafficking of apobec-1 via its interaction with the chaperonin Hsp70.

Characterization of a processed pseudogene of human psiHSP40 on chromosome 2q32

A pseudogene for the human Hsp40 gene has been characterized (psiHSP40). The pseudogene sequence shows 90% similarity to the human Hsp40 mRNA at the nucleotide level. No introns were found in the region corresponding to the human Hsp40 cDNA, and two direct repeats flank this same region. Because of these features, the pseudogene can be classified as a processed pseudogene. PsiHSP40 was assigned to chromosome 2q32 by in situ hybridization. This is the first report of a pseudogene for a member of the DnaJ (Hsp40) family protein gene.

Autoantibody to heat shock protein Hsp40 in sera of lung cancer patients

Heat shock protein Hsp40 is a stress protein with chaperone activity and has a cooperative function with Hsp70 in mammalian cells. We examined the possible expression of Hsp40 in lung tumor tissues using immunoblotting and immunohistochemistry, and established an enzyme-linked immunosorbent assay (ELISA) method to detect IgG antibody to Hsp40 in the serum using purified human Hsp40. Sera were obtained from 130 normal subjects and 50 patients with lung cancer. Lung tumor tissues and cells specifically overexpressed Hsp40, and no such expression was detected in normal lung tissues. Compared with normal sera, significantly higher levels of autoantibody to Hsp40 were present in patients with lung cancer. The present study is the first to demonstrate overexpression of Hsp40 in human tumor tissue and the associated presence of autoantibody to Hsp40 in the serum. These results suggest that overexpression of Hsp40 in tumor cells may be recognized as a self-antigen.

Human cyclophilin 40 is a heat shock protein that exhibits altered intracellular localization following heat shock

The unactivated steroid receptors are chaperoned into a conformation that is optimal for binding hormone by a number of heat shock proteins, including Hsp90, Hsp70, Hsp40, and the immunophilin, FKBP52 (Hsp56). Together with its partner cochaperones, cyclophilin 40 (CyP40) and FKBP51, FKBP52 belongs to a distinct group of structurally related immunophilins that modulate steroid receptor function through their association with Hsp90. Due to the structural similarity between the component immunophilins, FKBP52 and cyclophilin 40, we decided to investigate whether CyP40 is also a heat shock protein. Exposure of MCF-7 breast cancer cells to elevated temperatures (42 degrees C for 3 hours) resulted in a 75-fold increase in CyP40 mRNA levels, but no corresponding increase in CyP40 protein expression, even after 7 hours of heat stress. The use of cycloheximide to inhibit protein synthesis revealed that in comparison to MCF-7 cells cultured at 37 degrees C, those exposed to heat stress (42 degrees C for 3 hours) displayed an elevated rate of degradation of both CyP40 and FKBP52 proteins. Concomitantly, the half-life of the CyP40 protein was reduced from more than 24 hours to just over 8 hours following heat shock. As no alteration in CyP40 protein levels occurred in cells exposed to heat shock, an elevated rate of degradation would imply that CyP40 protein was synthesized at an increased rate, hence the designation of human CyP40 as a heat shock protein. Application of heat stress elicited a marked redistribution of CyP40 protein in MCF-7 cells from a predominantly nucleolar localization, with some nuclear and cytoplasmic staining, to a pattern characterized by a pronounced nuclear accumulation of CyP40, with no distinguishable nucleolar staining. This increase in nuclear CyP40 possibly resulted from a redistribution of cytoplasmic and nucleolar CyP40, as no net increase in CyP40 expression levels occurred in response to stress. Exposure of MCF-7 cells to actinomycin D for 4 hours resulted in the translocation of the nucleolar marker protein, B23, from the nucleolus, with only a small reduction in nucleolar CyP40 levels. Under normal growth conditions, MCF-7 cells exhibited an apparent colocalization of CyP40 and FKBP52 within the nucleolus.

Molecular chaperone function of mammalian Hsp70 and Hsp40--a review

Virtually all organisms respond to up-shifts in temperature (heat shock) by synthesizing a set of proteins called heat shock proteins (HSPs). The HSPs are induced not only by heat shock but also by various other environmental stresses. Induction of HSPs is regulated by the trans-acting heat shock factors (HSFs) and cis-acting heat shock element (HSE) present at the promoter region of each heat shock gene. Usually, HSPs are also expressed constitutively at normal growth temperatures and have basic and indispensable functions in the life cycle of proteins as molecular chaperones, as well as playing a role in protecting cells from the deleterious stresses. Molecular chaperones are able to inhibit the aggregation of partially denatured proteins and refold them using the energy of ATP. Recently, there are expectations for the use of molecular chaperones for the protection against and therapeutic treatment of inherited diseases caused by protein misfolding. In this review, the focus will be on the mammalian Hsp40, a homologue of bacterial DnaJ heat shock protein, and the beneficial functions of molecular chaperones.

Mammalian HSP40/DNAJ homologs: cloning of novel cDNAs and a proposal for their classification and nomenclature

We have cloned 10 novel full-length cDNAs of mouse and human HSP40/DNAJ homologs using expressed sequence tag (EST) clones found in the DDBJ/GenBank/EMBL DNA database. In this report, we tentatively designated them mHsp40, mDj3, mDj4, mDj5, mDj6, mDj7, mDj8, hDj9, mDj10, and mDj11. Based on the identity of the deduced amino acid sequences, mHsp40, mDj3, and mDj11 are orthologs of human Hsp40, rat Rdj2, and human Tpr2, respectively. We determined that mDj4 is identical with the recently isolated mouse Mrj (mammalian relative of DnaJ). PSORT analysis (a program that predicts the subcellular localization site of a given protein from its amino acid sequences) revealed that hDj9 has an N-terminal signal peptide; hence, its localization might be extracellular, suggesting that there may be a partner Hsp70 protein that acts together with the hDj9 outside of the cell. The same analysis indicated that mDj7 and mDj10 may have transmembrane domains. In order to simplify the complicated and confusing nomenclature of recently identified mammalian HSP40/DNAJ homologs, we propose here some new rules for their nomenclature. This proposed nomenclature includes the name of species with 2 lowercase letters such as hs (Homo sapiens), mm (Mus musculus) and rn (Rattus norvegicus); Dj standing for DnaJ; the name of types with A, B, and C, which were previously classified as type I, II, and III according to the domain structure of the homologs; and finally Arabic numerals according to the chronological order of registration of the sequence data into the database.

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

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

Characterization of HSE sequences in human Hsp40 gene: structural and promoter analysis

We have recently cloned a gene of Hsp40, a human homologue of bacterial DnaJ. Here we describe the structural and promoter analysis of human Hsp40 gene. Analysis of Hsp40 transcripts by 5' and 3' RACE suggested that they have different 3' ends, and primer extension studies revealed that the major transcription initiation site was localized 47 bp upstream of the ATG translation initiation codon. Promoter analysis using deletion derivatives defined a minimal region which was active in response to heat shock. The region contained the consensus heat shock element (HSE) sequences. The factor bound to these sequences was suggested to be a heat shock factor 1 (HSF1) by gel mobility supershift assay. In vivo footprinting and promoter analysis revealed that the HSEs in 5' upstream region of human Hsp40 gene were composed of eight contiguous (A/G)GAAN motifs and were essential for heat shock response. These results indicate that Hsp40 is a real heat shock protein. It is also shown that the HSE found in the first intron might not be the essential element for heat shock response.

Isolation of a new member of DnaJ-like heat shock protein 40 (Hsp40) from human liver

A new member of Hsp40, HLJ1, consisting of 337 amino acids, was cloned from a human liver cDNA library. The deduced amino acid sequence of HLJ1 has an 84% homology (69% identity) with that of HDJ-1 isolated from human placenta. Northern analysis showed that expression of the HLJ1 gene is heat-inducible and its transcription shows some degree of preference in heart, skeletal muscle, and pancreas.

Hsp70 and Hsp40 chaperone activities in the cytoplasm and the nucleus of mammalian cells

The existence and function of a Hsp40-Hsp70 chaperone machinery in mammalian cells in vivo was investigated. The rate of heat inactivation of firefly luciferase transiently expressed in hamster O23 fibroblasts was analyzed in cells co-transfected with the gene encoding the human Hsp40 (Ohtsuka, K. (1993) Biochem. Biophys. Res. Commun. 197, 235-240), the human inducible Hsp70 (Hunt, C., and Morimoto, R. I. (1985) Proc. Natl. Acad. Sci. U. S. A. 82, 6455-6459), or a combination of both. Whereas the expression of human Hsp70 alone in hamster cells was sufficient for the protection of firefly luciferase during heat shock, expression of the human Hsp40 alone was not. Rather, this led to a small but significant increase in the heat sensitivity of luciferase. The expression of the human Hsp40 only led to heat protection when the human Hsp70 was expressed as well. Under such conditions the rate of luciferase reactivation from the heat-inactivated state was increased, but the rate of inactivation during heat shock was not affected. Using constructs that direct firefly luciferase either to the cytoplasm or to the nucleus (Michels, A. A., Nguyen, V.-T., Konings, A. W. T., Kampinga, H. H., and Bensaude, O. (1995) Eur. J. Biochem. 234, 382-389), it was demonstrated that these chaperone functions are found in both compartments. Our data provide the first evidence on how the Hsp40/Hsp70 chaperone complex acts as heat protector in mammalian cells in vivo.

Hsp40, a possible indicator for thermotolerance of murine tumour in vivo

The relationship between Hsp40/Hsp70 synthesis and the development of thermotolerance was investigated using mouse squamous cell carcinoma in vivo. To examine the thermotolerance, tumours were heated at 44 degrees C for 30 min as conditioning heating. After various intervals they were heated again at 44 degrees C for 90 min as challenge heating. The tumour response to heat was evaluated by the growth delay. Thermotolerance rapidly developed with increasing interval and reached a maximum at 12 h interval. Subsequently, thermotolerance gradually decayed and almost disappeared at 120 h interval. Under this condition, synthesis of Hsp40/Hsp70 increased after conditioning heating, reached a maximum at 12 h interval, then gradually decreased thereafter within 120 h. The kinetics of accumulation and decay of both Hsp40 and Hsp70 were very similar. The extent of thermotolerance was well correlated with the relative amount of Hsp40/Hsp70. These results obtained in vivo were very similar to those in vitro (Kaneko et al. 1995). Our findings suggest that Hsp40 could be a useful indicator of the degree of thermotolerance in addition to Hsp70 in vivo as in vitro.

Regulation of thermotolerance and ischemic tolerance

Thermotolerance and ischemic tolerance are two major biological aspects where heat shock (stress) proteins exert essential roles for survival in cells as well as in various tissues. Bioflavonoids prevent the cells from acquiring thermotolerance after stresses through specific inhibition in the induction of heat shock proteins. The mechanism of this inhibition is revealed to be due to the prevention of the activation of heat shock factor 1 after heat shock. The induction of stress proteins during the ischemic stress is then described in global as well as focal cerebral ischemic model in rats. The activation of heat shock factor 1 after ischemia is first shown to induce various stress proteins in the central nervous system.

Expression of stress proteins and lymphocyte reactivity in heterotopic cardiac allografts undergoing cellular rejection

This report addresses the concept that, during rejection, the allograft undergoes a stress response which leads to an increased expression of stress proteins, also called heat shock proteins (hsp), and the recruitment and activation of hsp-reactive lymphocytes. Recent studies in our laboratory have provided evidence that hsp-reactive T-cells are present in cardiac allografts undergoing rejection. In this study, an MHC incompatible heterotopic heart allograft model (ACI into LEW) was chosen to analyse the kinetics of hsp expression during the development of rejection. Allografts and syngrafts (LEW into LEW) were harvested every day during the first 5 days post-transplant. Immunoblot analysis of proteins extracted from graft stromal tissues was done with murine monoclonal antibodies (mAb) against various mammalian hsp. Proliferation studies were done to determine hsp reactivity of graft-infiltrating lymphocytes on different days post-transplant. Three types of stressful stimuli appeared to increase hsp expression in the allograft. The first was a physiological stress secondary to the trauma of the transplant procedure and ischaemia/reperfusion injury and this would occur in allogeneic and syngeneic grafts. During the first day after transplantation, both types of grafts showed higher expression of hsp72 and grp78 and to a lesser extent, hsp60 and grp75. On the second and third day, the expression of grp78 and grp96 was higher in allografts than in syngrafts and this may reflect an immunologically mediated stress response in the allograft when infiltrating hsp-reactive lymphocytes became first detectable in the allograft. The third type of stress appeared related to the inflammatory process associated with rejection. On the fourth and fifth day post-transplant, the allografts showed strong expression of at least five proteins of lower molecular mass reacting with hsp-specific mAbs; namely, approximately 40 kDa (detected by anti-hsp60), approximately 30 kDa (by anti-hsp72), approximately 45 kDa and approximately 32 kDa (by anti-hsp72 + hsc73), and approximately 50 kDa (by anti-grp78). At that time, the allograft began to show progressive inflammatory changes and tissue damage. The appearance of lower molecular mass hsp-crossreactive proteins might reflect a degradation of hsps which had increased expression earlier during the post-transplant period. This process may generate large quantities of hsp-derived peptides which may be presented by MHC molecules to graft-infiltrating T-cells. Another interpretation of the strong expression of lower molecular bands in later allografts is that they represent other stress proteins that crossreact with antibodies against hsp60 and hsp70 family members.(ABSTRACT TRUNCATED AT 400 WORDS)

Evidence for aestivation specific proteins in Otala lactea

Changes in [35S]methionine protein labeling patterns were examined by following incorporation into the acid precipitate protein fraction of land snails, Otala lactea (Müller) (Pulmonata, Helicidae). Labeled proteins were analyzed by SDS polyacrylamide gel electrophoresis and isoelectric focusing columns. Snails in four different physiological states were compared: active controls, short term aestivating snails (injected and allowed to enter aestivation), long term aestivating snails (aestivated for 14 days, injected, and maintained in the aestivating state), and snails aroused after aestivation (aestivated, injected, and aroused). Protein associated radioactivity was measured over a 7 day time course post injection. Autoradiographic analysis of SDS-polyacrylamide gels showed increases in the radioactivity of four proteins: 91 kDa (hepatopancreas, day 1 in long term aestivating animals), 50 kDa (hepatopancreas, day 2 in short term aestivating snails), 70 kDa and 30 kDa (foot, day 2 in short term aestivating animals). Hepatopancreas and foot from day 1 long term aestivating and day 2 short term aestivating animals were also analyzed by isoelectric focusing columns. Several pH-specific differences were apparent when controls and aestivating animals were analyzed. In particular a peak of radioactivity was observed at pH 5.05 in 1 d long term aestivating hepatopancreas and at pH 4.30 in 2d short term aestivating animals. Several differences were noted in foot with no specific pattern emerging. SDS-polyacrylamide gel electrophoresis analysis of the hepatopancreas peaks showed the appearance of several bands with increased radioactivity, including the 91 kDa and 50 kDa proteins described above. These results suggest that O. lactea aestivation specific proteins may be involved in the transition to a depressed metabolic state.

Interaction between hsp70 and hsp40, eukaryotic homologues of DnaK and DnaJ, in human cells expressing mutant-type p53

We have recently identified a novel 40-kDa heatshock protein hsp40 as a mammalian homologue of bacterial DnaJ protein. Here we demonstrate the physical interaction between hsp70 (DnaK homologue) and hsp40 in human cells as determined by immunoprecipitation methods. Co-immunoprecipitation of hsp70 with hsp40 was dependent on the presence of ATP or unfolded protein (reduced carboxymethylated alpha-lactalbumin). A mutant type of tumor suppressor gene product, mtp53, was co-immunoprecipitated not only with hsp70 but also with hsp40. These results suggest the existence of a hsp70(DnaK)/hsp40(DnaJ) chaperone system in mammalian cells.

cAMP modulates stress protein synthesis in human monocytes-macrophages

The synthesis of heat-shock proteins (HSPs) and other stress proteins, including heme oxygenase (HO) and ferritin, is differentially induced by heat and oxidizing agents. In order to determine what role cAMP plays in those inductions in human monocytes-macrophages (m phi), we used cAMP activators or analogues alone or in combination with various stressful conditions. A stimulation in cAMP production did not per se affect stress proteins synthesis in m phi but modulated their induction in a differential way according to the stimulus. cAMP increased the synthesis of HSPs after heat shock. During erythrophagocytosis, whereas cAMP depressed the phagocytic process and the associated generation of superoxide anions, it enhanced the synthesis of HSPs, while inhibiting that of HO and ferritin. These results indicate that cAMP has a direct enhancing effect on the expression of stress proteins controlled by a classic heat-shock promoter, while decreasing their expression when induced by oxidative stress.

A stress-inducible 40 kDa protein (hsp40): purification by modified two-dimensional gel electrophoresis and co-localization with hsc70(p73) in heat-shocked HeLa cells

We have previously reported that a novel 40 kDa protein is induced by heat shock and several environmental stresses in mammalian and avian cells and that the N-terminal amino acid sequence of this 40 kDa protein has homology with the bacterial DnaJ heat-shock protein. We have purified this protein (40 kDa heat-shock protein, hsp40) from HeLa cells by modified two-dimensional gel electrophoresis and generated a polyclonal antibody against hsp40. This antibody was highly specific for human hsp40 and cross-reacted weakly with rat and Chinese hamster hsp40. Indirect immunofluorescence revealed that the hsp40 in HeLa cells accumulates in the nucleus, especially in the nucleolus, during heat shock and returns to the cytoplasm during the recovery period. The kinetics of the accumulation in the nucleoli and subsequent return to the cytoplasm of hsp40 was similar to that of hsp70. In addition, hsp40 was co-localized with hsc70(p73) in heat-shocked HeLa cells as demonstrated by double immunofluorescence staining. These results suggest that hsp40 (a DnaJ homologue) and hsp70 (a DnaK homologue) may act in concert to repair (refold) denatured proteins and protein aggregates in the nuclei and nucleoli of heat-shocked HeLa cells.

Stress proteins in aquatic organisms: an environmental perspective

The cellular stress response protects organisms from damage resulting from exposure to a wide variety of stressors, including elevated temperatures, ultraviolet (UV) light, trace metals, and xenobiotics. The stress response entails the rapid synthesis of a suite of proteins referred to as stress proteins, or heat-shock proteins, upon exposure to adverse environmental conditions. These proteins are highly conserved and have been found in organisms as diverse as bacteria, molluscs, and humans. In this review, we discuss the stress response in aquatic organisms from an environmental perspective. Our current understanding of the cellular functions of stress proteins is examined within the context of their role in repair and protection from environmentally induced damage, acquired tolerance, and environmental adaptation. The tissue specificity of the response and its significance relative to target organ toxicity also are addressed. In addition, the usefulness of using the stress response as a diagnostic in environmental toxicology is evaluated. From the studies discussed in this review, it is apparent that stress proteins are involved in organismal adaptation to both natural and anthropogenic environmental stress, and that further research using this focus will make important contributions to both environmental physiology and ecotoxicology.

Quercetin, an inhibitor of heat shock protein synthesis, inhibits the acquisition of thermotolerance in a human colon carcinoma cell line

Here, we describe the effects of quercetin on the induction of thermotolerance as examined by colony forming assay in a cell line derived from human colon carcinoma (COLO320 DM). Cells became resistant to heat treatment at 45 degrees C when they were preheated at 42 degrees C for 1.5 h or at 45 degrees C for 10 min. This induction of thermotolerance was almost completely inhibited by continuous treatment with 100 microM quercetin during the first and second heating sessions, and the interval between. This effect of quercetin was demonstrated to be dose-dependent over a concentration range of 50-200 microM. Quercetin did not increase the thermosensitivity of non-tolerant cells. The presence of quercetin during the first conditioning heating was more effective in inhibiting thermotolerance than its presence during the second heating. Quercetin was also found to inhibit the acquisition of thermotolerance induced by sodium arsenite. Cycloheximide, a nonspecific inhibitor of protein synthesis, did not affect the acquisition of thermotolerance by the same cell line. Quercetin specifically inhibits the synthesis of all heat shock proteins so far reported previously, and this leads to inhibition of the induction of thermotolerance. Such inhibition of thermotolerance by quercetin may improve the efficacy of clinical fractionated hyperthermia.

Metal carcinogenesis: mechanistic implications

Cancer epidemiology has identified several metal compounds as human carcinogens. Recent evidence suggests that carcinogenic metals induce genotoxicity in a multiplicity of ways, either alone or by enhancing the effects of other agents. This review summarizes current information on the genotoxicity of arsenic, chromium, nickel, beryllium and cadmium compounds and their possible roles in carcinogenesis. Each of these metals is distinct in its primary modes of action; yet there are several mechanisms induced by more than one metal, including: the induction of cellular immunity and oxidative stress, the inhibition of DNA metabolism and repair and the formation of DNA- and/or protein-crosslinks.