Cloning, nucleotide sequence and expression of rat heat inducible hsp70 gene

The multifaceted role of intracellular glycosylation in cytoprotection and heart disease

The modification of nuclear, cytoplasmic, and mitochondrial proteins by O-linked β-N-actylglucosamine (O-GlcNAc) is an essential posttranslational modification that is common in metozoans. O-GlcNAc is cycled on and off proteins in response to environmental and physiological stimuli impacting protein function, which, in turn, tunes pathways that include transcription, translation, proteostasis, signal transduction, and metabolism. One class of stimulus that induces rapid and dynamic changes to O-GlcNAc is cellular injury, resulting from environmental stress (for instance, heat shock), hypoxia/reoxygenation injury, ischemia reperfusion injury (heart attack, stroke, trauma hemorrhage), and sepsis. Acute elevation of O-GlcNAc before or after injury reduces apoptosis and necrosis, suggesting that injury-induced changes in O-GlcNAcylation regulate cell fate decisions. However, prolonged elevation or reduction in O-GlcNAc leads to a maladaptive response and is associated with pathologies such as hypertrophy and heart failure. In this review, we discuss the impact of O-GlcNAc in both acute and prolonged models of injury with a focus on the heart and biological mechanisms that underpin cell survival.

Liposome-based DNA carriers may induce cellular stress response and change gene expression pattern in transfected cells

Background

During functional studies on the rat stress-inducible Hspa1b (hsp70.1) gene we noticed that some liposome-based DNA carriers, which are used for transfection, induce its promoter activity. This observation concerned commercial liposome formulations (LA), Lipofectin and Lipofectamine 2000. This work was aimed to understand better the mechanism of this phenomenon and its potential biological and practical consequences.

Results

We found that a reporter gene driven by Hspa1b promoter is activated both in the case of transient transfections and in the stably transfected cells treated with LA. Using several deletion clones containing different fragments of Hspa1b promoter, we found that the regulatory elements responsible for most efficient LA-driven inducibility were located between nucleotides -269 and +85, relative to the transcription start site. Further studies showed that the induction mechanism was independent of the classical HSE-HSF interaction that is responsible for gene activation during heat stress. Using DNA microarrays we also detected significant activation of the endogenous Hspa1b gene in cells treated with Lipofectamine 2000. Several other stress genes were also induced, along with numerous genes involved in cellular metabolism, cell cycle control and pro-apoptotic pathways.

Conclusions

Our observations suggest that i) some cationic liposomes may not be suitable for functional studies on hsp promoters, ii) lipofection may cause unintended changes in global gene expression in the transfected cells.

Photochemical Internalization of Transgenes Controlled by the Heat-shock Protein 70 Promoter

Photochemical internalization (PCI) is a targeting technique that facilitates endosomal escape of macromolecules, such as transgenes, in response to photochemical treatment with endosome/lysosome-localized photosensitizers, such as disulfonated meso-tetraphenylporphine (TPPS(2a)). In gene therapy this leads to enhanced transgene expression. Moreover, photochemical treatment generally activates transcription of stress-response genes, such as heat-shock proteins (HSPs), via stimulation of corresponding promoters. Therefore, we used HSP70 (HSPp; a promoter from the HSP family gene) and investigated whether the PCI stimulus could also activate HSPp and thereby stimulate transcription (expression) of the HSPp-controlled transgene internalized via PCI. Using human colorectal carcinoma and hepatoma cell lines in vitro, we showed that TPPS(2a)-based photochemical treatment enhances expression of cellular HSP70, which correlated with a photochemically enhanced expression (approximately 2-fold, at PCI-optimal doses) of the HSPp-controlled transgene integrated in the genome. Furthermore, PCI enhanced expression of the HSPp-controlled episomal transgene delivered as a plasmid. However, in plasmid-based transfection, PCI-mediated enhancement with HSPp did not exceed the enhancement achieved with the constitutive active CMV promoter. In conclusion, we demonstrated that the PCI-relevant treatment initiates HSP70 response and that the HSP70 promoter can be used in combination with PCI, leading to PCI-enhanced expression of the HSPp-controlled transgene.

Novel Method to Examine Hepatocyte-Specific Gene Expression in a Functional Coculture System

To mimic native tissue function, coculture systems are an extremely useful model. In many cases, differentiated functions can be maintained only through the interactions of various cell types. Therefore, methods for examining the interactions between cocultured cells are necessary. The assessment of cell-to-cell cross-talk at the level of gene expression is one such method to examine interactions between different cell types. However, it is generally difficult to determine the gene expression of specific cell types in coculture without first separating cell populations. To overcome these obstacles, we have established a novel method to determine gene expression levels of a targeted cell population in coculture, using species-specific primers. With this approach, we were able to determine hepatocyte-specific gene expression of Fao cells (a rat hepatocyte cell line) in culture with human umbilical vein endothelial cells (HUVECs). Expression of both albumin and apolipoprotein A-I (apoA-I) increased time dependently for 10 days and maintained significantly higher expression in the coculture system as compared with isolated Fao cells. This indicates that hepatocyte function increased gradually in our coculture system and could be maintained long-term, suggesting that the construction of mature cell-to-cell communication between the two cell lines required a considerable amount of time. The expression of HNF-4 and HNF-1alpha, which are liver-enriched transcription factors, did not differ between the monolayer and cocultured Fao cells, suggesting that expression of HNF-4 and HNF-1alpha was not responsible for the increased expression albumin and apoA-I. Our findings suggest that this novel method for the detection of gene expression of targeted cell populations can be a useful tool in determining the molecular mechanisms that regulate communication between different cell types.

Oligo-3-hydroxybutyrates as potential carriers for drug delivery

In the present paper we describe the synthesis and toxicity studies of well-defined tailor made oligo-[R,S]-3-hydroxybutyrates (OHBs). The results indicate potential applicability of these nano-polymers as drug delivery carriers. Several OHBs of number average molecular weight (M(n)) ranging from 800 to 2400 have been synthesized and tested on transformed hamster V79 fibroblasts and murine melanoma B16(F10) cells using the 3-[4,5-dimethylthiazol-2-yl]2,5-diphenyltetrazolium bromide (MTT) based drug resistance and clonogenic survival assays. We show that 96-h incubation of cells with 1-9 microg/ml of OHBs did not affect cell viability. Incubation of OHBs with rat hepatoma FTO-2B cells stably transfected with chloramphenicol acetyltransferase (CAT) gene ligated to heat-inducible hsp70i gene promoter demonstrated that OHBs did not induce cellular stress response. Finally, we demonstrate that doxorubicin conjugated with OHB is effectively taken up by murine melanoma B16(F10) cells in vitro and localizes in the cytoplasm. These data show for the first time that tailor-made biodegradable and biocompatible oligomers of 3-hydroxybutyric acid can be taken into consideration as effective, non-toxic vectors for delivery of drugs in a conjugated form.

Structure of gene flanking regions and functional analysis of sequences upstream of the rat hsp70.1 stress gene

We present structural and comparative analysis of the flanking regions of the rat hsp70.1 stress gene. Several repetitive sequences, microsatellites and short interspersed repetitive elements (SINEs) were found, as well as a significant gap in the 3' UTR, as compared to the orthologous mouse gene. We also show that the complex microsatellite region composed of partially overlapping inverted repeat and long homopurine-homopyrimidine sequence, which is localized 1.8 kbp upstream of the transcription start site, is capable to adopt non-B DNA structures (an H-DNA and a cruciform structure) in vitro. Functional analysis performed with the use of various fragments of the 5'end flanking regions ligated to the chloramphenicol acetyltransferase (CAT) reporter gene revealed a crucial role of cooperation between heat shock element (HSE) regulatory sequences, while none of the three HSEs alone is able to drive efficient heat induced transcription of the reporter gene. We also found that the microsatellite region does not influence transcription by itself, however, it abolishes the effect of the adjacent putative silencing element. To our knowledge, this is a first extensive structural and functional analysis of the promoter region of the mammalian heat inducible hsp70i gene localized distally to the hsp70-related spermatid-specific gene in the major histocompatibility complex III.

HSP70 overexpression increases resistance of V79 cells to cytotoxicity of airborne pollutants, but does not protect the mitotic spindle against damage caused by airborne toxins

Exposure of Chinese hamster V79 cells to extracts of airborne pollutants induced formation of multipolar or incomplete mitotic spindles. To find out whether overexpression of the HSP70 chaperone protein could protect spindles against airborne toxins we constructed V79 cells stably transfected with an expression vector containing rat heat-inducible hsp70.1 gene under the control of a constitutive CMV promoter. When cells were incubated with extracts of airborne pollutants (5-20 microg/ml) no protective effect of the HSP70 protein against mitotic spindle damage was observed. Moreover, at 20 microg/ml of extracts of airborne toxins the frequency of mitotic malformations was even higher in HSP70-overexpressing cells than in control ones. Extracts of airborne pollutants of 50 microg/ml blocked the formation of mitotic figures both in control and HSP70-overexpressing cells and led to destruction of cell nuclei. However, the HSP70-overproducing cells exhibited higher survival rates when exposed to heat shock and airborne toxins than the control ones, as determined by MTT assay. This suggests that HSP70 overexpression-a frequent feature of cancer cells-should be considered as a factor facilitating survival of cells with damaged mitotic spindles and aberrantly segregated chromosomes.

Induction of systemic antitumor immunity by gene transfer of mammalian heat shock protein 70.1 into tumors in situ

Heat shock proteins (hsps) chaperone cytosolic peptides, forming complexes that stimulate antitumor immunity. Hsps facilitate signal 1 in the two-signal model of T-cell costimulation, whereas cell adhesion molecules such as B7.1 provide secondary (signal 2) costimulatory signals. B7.1 gene transfer into tumors in situ has been shown to eradicate small (<0.3 cm in diameter) tumors in mice, and induce systemic antitumor immunity, but is ineffective against larger tumors. We examine whether mammalian hsps, as facilitators of T-cell costimulation, also exhibit this ability, and whether simultaneously stimulating both signal 1 (hsp-facilitated antigen presentation) and signal 2 (B7.1-mediated costimulation) enhances antitumor immunity compared to that achieved with either monotherapy. Prophylactic vaccination of mice with an hsp preparation from an EL-4 lymphoma weakly retarded tumor growth, to the same extent as that achieved with a single EL-4-derived peptide (AQHPNAELL), previously shown to induce antitumor immunity establishing that a preparation of EL-4 hsp-peptide complexes has antitumor activity. Here we show that injection of rat hsp70.1 into mouse tumors in situ causes the complete eradication of tumors, and generates potent systemic antitumor immunity mediated by CD4+ and CD8+ T cells. Unexpectedly, simultaneous gene transfer of hsp70.1 and B7.1 compromised the efficacy of hsp-mediated tumor rejection--a problem which could be partially overcome by the timed delivery of hsp70.1 and B7.1. Thus, gene transfer of hsp70 into tumors can be employed to generate potent systemic antitumor immunity, but further consideration is required if this approach is to be successfully combined with immunotherapies employing other T-cell costimulators.

Heat shock proteins and cardiovascular pathophysiology

In the eukaryotic cell an intrinsic mechanism is present providing the ability to defend itself against external stressors from various sources. This defense mechanism probably evolved from the presence of a group of chaperones, playing a crucial role in governing proper protein assembly, folding, and transport. Upregulation of the synthesis of a number of these proteins upon environmental stress establishes a unique defense system to maintain cellular protein homeostasis and to ensure survival of the cell. In the cardiovascular system this enhanced protein synthesis leads to a transient but powerful increase in tolerance to such endangering situations as ischemia, hypoxia, oxidative injury, and endotoxemia. These so-called heat shock proteins interfere with several physiological processes within several cell organelles and, for proper functioning, are translocated to different compartments following stress-induced synthesis. In this review we describe the physiological role of heat shock proteins and discuss their protective potential against various stress agents in the cardiovascular system.

HSP-CBF is an NF-Y-dependent coactivator of the heat shock promoters CCAAT boxes

The cellular response to toxic stimuli is elicited through the expression of heat shock proteins, a transcriptional process that relies upon conserved DNA elements in the promoters: the Heat Shock Elements, activated by the heat shock factors, and the CCAAT boxes. The identity of the CCAAT activator(s) is unclear because two distinct entities, NF-Y and HSP-CBF, have been implicated in the HSP70 system. The former is a conserved ubiquitous trimer containing histone-like subunits, the latter a 110-kDa protein with an acidic N-terminal. We analyzed two CCAAT-containing promoters, HSP70 and HSP40, with recombinant NF-Y and HSP-CBF using electrophoretic mobility shift assay, protein-protein interactions, transfections and chromatin immunoprecipitation assays (ChIP) assays. Both recognize a common DNA-binding protein in nuclear extracts, identified in vitro and in vivo as NF-Y. Both CCAAT boxes show high affinity for recombinant NF-Y but not for HSP-CBF. However, HSP-CBF does activate HSP70 and HSP40 transcription under basal and heat shocked conditions; for doing so, it requires an intact NF-Y trimer as judged by cotransfections with a diagnostic NF-YA dominant negative vector. HSP-CBF interacts in solution and on DNA with the NF-Y trimer through an evolutionary conserved region. In yeast two-hybrid assays HSP-CBF interacts with NF-YB. These data implicate HSP-CBF as a non-DNA binding coactivator of heat shock genes that act on a DNA-bound NF-Y.

Heat shock proteins Hsp70-1 and Hsp70-3 Are necessary and sufficient to prevent arsenite-induced dysmorphology in mouse embryos

Heat Shock Proteins (HSPs) represent a variety of protein families that are induced by stressors such as heat and toxicants, and the induction of HSPs in the organogenesis stage rodent embryo is well established. It has been proposed that thermotolerance and chemotolerance result from expression of the HSPs. However, whether these proteins function to prevent dysmorphogenesis and which family members serve this function are unknown. Therefore, we evaluated the specific ability of stress-inducible Hsp70-1 and Hsp70-3 to prevent arsenite-induced dysmorphology in the cultured mouse embryo using gain- and loss-of-function models. Loss of HSP function was accomplished by injecting antisense oligonucleotides directed against hsp70-1 and hsp 70-3 mRNAs into the amniotic cavity of cultured Day 9 mouse embryos. Suppression of hsp70-1 and hsp70-3 expression resulted in an up to six-fold increase in the incidence of arsenite-induced neural tube defects. Gain of HSP function was accomplished by microinjecting a transgene with a constitutive promotor driving expression of the hsp70-1 coding region, and resulted in a decreased incidence of arsenite-induced neural tube defects. These results indicate that Hsp70-1 and Hsp70-3 are both necessary and sufficient for preventing arsenite-induced dysmorphology in early-somite staged mouse embryos. Mol. Reprod. Dev. 59:285-293, 2001.

Green fluorescent protein as a marker for monitoring activity of stress-inducible hsp70 rat gene promoter

Murine melanoma cells B16(F10) were stably transfected with a plasmid containing GFP gene linked to rat stress-inducible hsp70.1 gene promoter. Transfected cells show in vitro variable basal levels of fluorescence depending on stress response induced at physiological temperature by growth conditions. Lack of manipulations except medium change resulted in reduction of cellular fluorescence. GFP expression in experimental murine tumors dropped to levels undetectable at physiological temperature. Heat shock induced significant fluorescence of tumor cells both in vitro and in vivo. GFP protein could be a useful marker for studies of mammalian hsp70i gene promoters.

Regulation of glucocorticoid receptor mRNA and heat shock protein 70 mRNA in the developing sheep brain

Fetal hypothalamo-pituitary-adrenal (HPA) activity increases dramatically at term in sheep, however, little is known about the regulation of glucocorticoid feedback in the developing brain. Heat shock protein 70 (hsp70) is closely associated with glucocorticoid actions within the cell. We hypothesized that there is a decrease in glucocorticoid negative feedback in the brain, near term, resulting from changes in the expression of glucocorticoid receptors (GR) and hsp70. Brains were removed at various stages of development. GR mRNA levels in the paraventricular nucleus (PVN) and cortex, and hsp70 mRNA in the PVN were determined by in situ hybridization. In the hippocampus, GR mRNA levels were measured by Northern analysis. In the PVN, GR mRNA was present by d60. GR mRNA levels reached a peak at d100-110, but then decreased significantly with progression of gestation, and were lowest at term. Hippocampal GR mRNA levels were highest on day 130 of gestation, decreasing to low levels at term. In the cerebral cortex, GR mRNA levels were expressed at high levels in all layers of the cortex by day 110 of gestation with levels decreasing to term. Hsp70 mRNA was present in both parvocellular and magnocellular regions of the PVN, and there was no significant change in late gestation. In conclusion, (1) The high levels of GR mRNA present in the PVN, hippocampus and cerebral cortex during fetal life are likely important in development of these structures at a time when circulating glucocorticoids are low. (2) Changes in GR mRNA levels in the PVN are not associated with alterations in the expression of hsp70. (3) The decrease in GR mRNA in the hippocampus and PVN in late gestation, at a time when fetal plasma cortisol is increasing, likely facilitates maintained hypothalamic drive to the pituitary corticotroph.

Molecular characterization of a heat shock cognate cDNA of zebrafish, hsc70, and developmental expression of the corresponding transcripts

To elucidate the potential role of the hsp70 gene family in developmental processes in vertebrates, we chose to study the expression of one of these genes in zebrafish. A zebrafish gastrula cDNA library was screened with a Pleurodeles waltl hsp70 cDNA probe. A 2.3-kb cDNA was thus isolated and sequenced. The predicted amino acid sequence contained an open reading frame encoding for a 649-amino acid polypeptide. Sequence analysis showed strong homology with hsp70-related gene sequences in other species; in particular, the strongest homology was found with the cognate members of this family. Tests of heat inducibility revealed that transcripts were expressed at normal temperature, but the level of transcript expression increased after heat shock. Moreover, experiments of the neosynthesis of total proteins in heat shock conditions and corresponding immunoblotting assays showed that 24-h-stage embryos are able to respond to heat shock. The quantity of 70 kDa proteins, recognized by a specific antibody of the HSP/C70 protein family, is expressed in control condition and increased significantly after heat shock. Furthermore, Northern blot analysis of transcript expression showed that the corresponding mRNAs were detected throughout embryonic development in the absence of any heat shock. Our clone, named hsc70, thus corresponded to a cognate member of the hsp70 gene family, expressed under normal conditions during development, but also heat inducible. The spatio-temporal pattern of transcripts during development was determined by in situ hybridization on wholemount embryos at different stages. As a maternal RNA, hsc70 mRNA was uniformly present in the embryo, up to the end of gastrulation. Later, a tissue-specific enrichment of hsc70 transcripts was detected in the central nervous system (CNS) and in a fraction of the somites. These results suggest that the hsc70 gene may be involved in developmental differentiation events.

Analysis of the 5'-flanking regions of the MHC-linked Hsp70-2 and Hsp70-3 genes of the rat

We have analyzed the genomic interval between the MHC-linked heat shock protein 70 (Hsp70) genes Hsp70-2 and Hsp70-3 in the rat. The distance between the transcription start sites of both genes which are organized in a head-to-head orientation is 604 bp. Unlike Hsp70-2 the 5'untranslated region of Hsp70-3 is interrupted by an intron of about 3.9 kb. The Hsp70-3 promoter lacks a TATA box and heat shock elements, but contains two CRE elements, one Sp1-GC and two PuF binding sites. Analysis of the Hsp70-2 promoter by CAT assays reveals positive and negative regulatory elements extending into the Hsp70-3 gene.

Inducible heat shock protein 70 in rat cardiac allograft and its immunohistochemical localization in cardiac myocytes

BACKGROUND

Heat shock proteins (HSP) are induced by a variety of stress and are presumed to play an important role in protecting cells from the effects of stress. Some evidence exists that HSP is involved in allograft rejection. Recently, an increase of inducible HSP 70 in heterotopic rat heart allografts was shown by quantitative Western blotting. To determine a possible mRNA induction and the localization of inducible HSP 70, we examined 19 heart transplants in rats.

METHODS

Fisher F344 rat hearts were heterotopically transplanted into Lewis recipients (n=10), and nine cardiac isografts (Fisher to Fisher) were performed. The 19 native hearts of the recipients served as controls. Animals were killed on posttransplantation days 1, 3, and 5. The hearts were examined immunohistologically for inducible HSP and analyzed by a semiquantitative polymerase chain reaction for inducible mRNA.

RESULTS

The level of HSP 70 mRNA in the allograft increased from day 1 to 3 and day 3 to 5 after transplantation and was significantly higher than that of time-matched isografts (0.92+/-0.49 vs. 0.49+/-0.05 and 1.14+/-0.53 vs. 0.53+/-0.15; P<0.05). The native hearts showed no elevated HSP 70 expression compared with isografts. Immunohistochemically, the majority of inducible HSP was located in cardiomyocytes adjacent to infiltrating lymphocytes, which where consistently negative.

CONCLUSIONS

These results demonstrate that HSP mRNA expression in cardiac allografts is time-dependent, and its protein is expressed in cardiomyocytes.

Characterization of a new high-temperature-induced 66-kDa heat-shock protein, antigenically related to heat-shock protein 72

M-14 human melanoma cells, following severe hyperthermic exposures, synthesized a heat-shock protein of 66 kDa (hsp 66), in addition to the major "classic" heat-shock proteins. This hsp 66 was not expressed following mild hyperthermic exposures sufficient to trigger the synthesis of the other heat-shock proteins. The induction of hsp 66 was observed also in Li human glioma cells treated at 45 degrees C for 20 min. By contrast, hsp 66 was not induced in seven other human cell lines (both melanoma and nonmelanoma) when they were subjected to the same hyperthermic treatment. Immunological recognition experiments showed that hsp 66 cross-reacted with the inducible hsp 72, but not with the constitutive hsp 73. The possibility that hsp 66 is a breakdown product of hsp 72 was ruled out by the fact that Poly(A)+ RNA extracted from cells treated at 45 degrees C for 20 min was able to direct the synthesis of hsp 66 (together with hsp 72) in a message-dependent rabbit reticulocyte lysate, as well as in microinjected Xenopus oocytes. By contrast, only the hsp 72 was expressed using Poly(A)+ RNA extracted from cells heated at 42 degrees C for 1 h. Affinity chromatography experiments on ATP-agarose showed that hsp 66 did not bind ATP in vitro. hsp 66 was localized both in the cytoplasm (cytosol, mitochondria, and microsome fraction) and in the nuclei of cells recovered from a severe heat shock: this intracellular distribution closely corresponded to that of hsp 72. The nuclear-associated hsp 66 was found to be tightly bound to nuclear structures and could not be extracted by incubation in ATP-containing buffer.

A 252 bp upstream region of the rat spermatocyte-specific hst70 gene is sufficient to promote expression of the hst70-CAT hybrid gene in testis and brain of transgenic mice

The rat hst70 gene belongs to a heat shock hsp70 multigene family and its expression has been detected so far solely in spermatocytes. To investigate the cis-elements responsible for testis-specific expression of the hst70 gene we produced several lines of transgenic mice carrying fragments of the 5'-flanking regions of the hst70 gene fused to the chloramphenicol acetyltransferase (CAT) reporter gene. Hybrid genes of series B were constructed such that, besides the 780 bp, 343 bp and 163 bp 5'-flanking region these plasmids contained no other sequences of the hst70 gene. In hybrid genes of series D the CAT gene was ligated to 343 bp and 252 bp 5'-flanking regions together with the 57 bp of the 5'-end nontranslated (leader) sequences of the hst70 gene. We found that in 780/B, 343/B, 343/D and 252/D adult mice the transgene was specifically and highly expressed in testes. In developing testes the high CAT activity appeared in transgenic mice aged 3 weeks and older. None of the three 163/B transgenic lines exhibited CAT activity in any tissue analyzed. In all CAT expressing lines a weak but significant CAT activity (up to 5% of that in testis) was detected also in the brain. RNase protection assay confirmed that the endogenous hst70 gene transcripts are present in testis as well as in brain of nontransgenic rats and mice. Our data show that the cis-regulatory sequences responsible for testis-specific and developmentally regulated expression of the hst70 gene are localized within the 252 bp region 5' to the gene and neither the 5'-end nor 3'-end nontranslated sequences of the gene are important for this specificity.

Genetic aspects of the hsp70 multigene family in vertebrates

The family of genes encoding heat shock proteins of about 70 kDa (hsp70) in vertebrates is reviewed under genetic aspects. After a detailed description of the various hsp70 genes more general characteristics of the organization and evolution of the multigene family are discussed.