Stage and lineage-regulated expression of two hsp90 transcripts during mouse germ cell differentiation and embryogenesis

Gene expression analysis of ovine prepubertal testicular tissue vitrified with a novel cryodevice (E.Vit)

PURPOSE

Testicular tissue cryopreservation prior to gonadotoxic therapies is a method to preserve fertility in children. However, the technique still requires development, especially when the tissue is immature and rather susceptible to stress derived from in vitro manipulation. This study aimed to investigate the effects of vitrification with a new cryodevice (E.Vit) on cell membrane integrity and gene expression of prepubertal testicular tissue in the ovine model.

METHODS

Pieces of immature testicular tissue (1 mm³) were inserted into "E.Vit" devices and vitrified with a two-step protocol. After warming, tissues were cultured in vitro and cell membrane integrity was assessed after 0, 2, and 24 h by trypan blue exclusion test. Controls consisted of non-vitrified tissue analyzed after 0, 2, and 24 h in vitro culture (IVC). Expression of genes involved in transcriptional stress response (BAX, SOD1, CIRBP, HSP90AB1), cell proliferation (KIF11), and germ- (ZBDB16, TERT, POU5F1, KIT) and somatic- (AR, FSHR, STAR) cell specific markers was evaluated 2 and 24 h after warming.

RESULTS

Post-warming trypan blue staining showed the survival of most cells, although membrane integrity immediately after warming (66.00% ± 4.73) or after 2 h IVC (59.67% ± 4.18) was significantly lower than controls (C0h 89.67% ± 1.45). Extended post-warming IVC (24 h) caused an additional decrease to 31% ± 3.46 (P < 0.05). Germ- and somatic-cell specific markers showed the survival of both cell types after cryopreservation and IVC. All genes were affected by cryopreservation and/or IVC, and moderate stress conditions were indicated by transcriptional stress response.

CONCLUSIONS

Vitrification with the cryodevice E.Vit is a promising strategy to cryopreserve prepubertal testicular tissue.

Heat Shock Protein 90 as a Prognostic Marker and Therapeutic Target for Adrenocortical Carcinoma

Background: Adrenocortical carcinoma (ACC) is a rare tumor entity with restricted therapeutic opportunities. HSP90 (Heat Shock Protein 90) chaperone activity is fundamental for cell survival and contributes to different oncogenic signaling pathways. Indeed, agents targeting HSP90 function have shown therapeutic efficacy in several cancer types. We have examined the expression of HSP90 in different adrenal tumors and evaluated the use of HSP90 inhibitors in vitro as possible therapy for ACC. Methods: Immunohistochemical expression of HSP90 isoforms was investigated in different adrenocortical tumors and associated with clinical features. Additionally, a panel of N-terminal (17-allylamino-17-demethoxygeldanamycin (17-AAG), luminespib, and ganetespib) and C-terminal (novobiocin and silibinin) HSP90 inhibitors were tested on various ACC cell lines. Results: Within adrenocortical tumors, ACC samples exhibited the highest expression of HSP90β. Within a cohort of ACC patients, HSP90β expression levels were inversely correlated with recurrence-free and overall survival. In functional assays, among five different compounds tested luminespib and ganetespib induced a significant decrease in cell viability in single as well as in combined treatments with compounds of the clinically used EDP-M scheme (etoposide, doxorubicin, cisplatin, mitotane). Inhibition of cell viability correlated furthermore with a decrease in proliferation, in cell migration and an increase in apoptosis. Moreover, analysis of cancer pathways indicated a modulation of the ERK1/2-and AKT-pathways by luminespib and ganetespib treatment. Conclusions: Our findings emphasize HSP90 as a marker with prognostic impact and promising target with N-terminal HSP90 inhibitors as drugs with potential therapeutic efficacy toward ACC.

PML/RARA inhibits expression of HSP90 and its target AKT

Essential for cell survival, the 90 kD Heat Shock Proteins (HSP90) are molecular chaperons required for conformational stabilization and trafficking of numerous client proteins. Functional HSP90 is required for the stability of AKT, a serine-threonine kinase phosphorylated in response to growth factor stimulation. AKT plays a crucial regulatory role in differentiation, cell cycle, transcription, translation, metabolism and apoptosis. Acute promyelocytic leukaemia (APL) is characterized by the presence of the promyelocytic leukaemia/retinoic acid receptor alpha (PML/RARA) fusion protein, which deregulates expression of several genes involved in differentiation and apoptosis. Here, we report inhibition of HSP90AA1 and HSP90AB1 isomer transcription in blasts isolated from patients with APL, associated with reduction of HSP90 protein expression and loss of control on AKT protein phosphorylation. We show that in vitro treatment of PML/RARA expressing cells with all-trans retinoic acid (ATRA) up-regulates HSP90 expression and stabilizes AKT. Addition of the HSP90-inhibitor 17-(allylamino)-17-demethoxygeldanamycin in combination with ATRA, blocks upregulation of AKT protein, indicating that HSP90 is necessary for ATRA action on AKT. This is the first report proving that expression of HSP90 isomers are directly and differentially repressed by PML/RARA, with critical results on cellular homeostasis of target proteins, such as AKT, in APL blasts.

The Unmysterious Roles of HSP90: Ovarian Pathology and Autoantibodies

The heat shock proteins (HSPs) are a group of evolutionarily conserved proteins with important physiological functions, whose synthesis is enhanced by elevated temperature or other stresses. HSPs show high sequence homology between different species, from bacteria to humans. Despite the significant degree of evolutionary conservation, HSPs are highly immunogenic. Of the several HSPs, HSP90 is an abundant, constitutively expressed chaperone constituting around 1-2% of total cellular protein under non-stress conditions. This protein from even the most distantly related eukaryotes has 50% amino acid identity, and all have more than 40% identity with the Escherichia coli protein. They are immunodominant antigens for many common microbes, and thus their epitopes are recognized by the immune system. As HSPs are overexpressed at sites of acute and chronic inflammation, individuals are likely to be sensitized during the course of a microbial infection encountered during life. This chapter considers the evidence of a role for HSP90 in autoimmune ovarian failure, where autoantibodies to it have been observed in patients, and has been correlated to infertility.

Transcriptome profiling of the testis reveals genes involved in spermatogenesis and marker discovery in the oriental fruit fly, Bactrocera dorsalis

The testis is a highly specialized tissue that plays a vital role in ensuring fertility by producing spermatozoa, which are transferred to the female during mating. Spermatogenesis is a complex process, resulting in the production of mature sperm, and involves significant structural and biochemical changes in the seminiferous epithelium of the adult testis. The identification of genes involved in spermatogenesis of Bactrocera dorsalis (Hendel) is critical for a better understanding of its reproductive development. In this study, we constructed a cDNA library of testes from male B. dorsalis adults at different ages, and performed de novo transcriptome sequencing to produce a comprehensive transcript data set, using Illumina sequencing technology. The analysis yielded 52 016 732 clean reads, including a total of 4.65 Gb of nucleotides. These reads were assembled into 47 677 contigs (average 443 bp) and then clustered into 30 516 unigenes (average 756 bp). Based on BLAST hits with known proteins in different databases, 20 921 unigenes were annotated with a cut-off E-value of 10(-5). The transcriptome sequences were further annotated using the Clusters of Orthologous Groups, Gene Orthology and the Kyoto Encyclopedia of Genes and Genomes databases. Functional genes involved in spermatogenesis were analysed, including cell cycle proteins, metalloproteins, actin, and ubiquitin and antihyperthermia proteins. Several testis-specific genes were also identified. The transcripts database will help us to understand the molecular mechanisms underlying spermatogenesis in B. dorsalis. Furthermore, 2913 simple sequence repeats and 151 431 single nucleotide polymorphisms were identified, which will be useful for investigating the genetic diversity of B. dorsalis in the future.

Radicicol, a heat shock protein 90 inhibitor, inhibits differentiation and adipogenesis in 3T3-L1 preadipocytes

Heat shock protein 90 (Hsp90) is involved in various cellular processes, such as cell proliferation, differentiation and apoptosis. As adipocyte differentiation plays a critical role in obesity development, the present study investigated the effect of an Hsp90 inhibitor radicicol on the differentiation of 3T3-L1 preadipocytes and potential mechanisms. The cells were treated with different concentrations of radicicol during the first 8days of cell differentiation. Adipogenesis, the expression of adipogenic transcriptional factors, differentiation makers and cell cycle were determined. It was found that radicicol dose-dependently decreased intracellular fat accumulation through down-regulating the expression of peroxisome proliferator-activated receptor γ (PPARγ) and CCAAT element binding protein α (C/EBPα), fatty acid synthase (FAS) and fatty acid-binding protein 4 (FABP4). Flow cytometry analysis revealed that radicicol blocked cell cycle at G1-S phase. Radicicol redcued the phosphorylation of Akt while showing no effect on β-catenin expression. Radicicol decreased the phosphorylation of phosphoinositide-dependent kinase 1 (PDK1). The results suggest that radicicol inhibited 3T3-L1 preadipocyte differentiation through affecting the PDK1/Akt pathway and subsequent inhibition of mitotic clonal expansion and the expression/activity of adipogenic transcriptional factors and their downstream adipogenic proteins.

TLRR (lrrc67) interacts with PP1 and is associated with a cytoskeletal complex in the testis

BACKGROUND INFORMATION

Spermatozoa are formed via a complex series of cellular transformations, including acrosome and flagellum formation, nuclear condensation and elongation and removal of residual cytoplasm. Nuclear elongation is accompanied by the formation of a unique cytoskeletal structure, the manchette. We have previously identified a leucine-rich repeat protein that we have named TLRR (testis leucine-rich repeat), associated with the manchette that contains a PP1 (protein phosphatase-1)-binding site. Leucine-rich repeat proteins often mediate protein-protein interactions; therefore, we hypothesize that TLRR acts as a scaffold to link signalling molecules, including PP1, to the manchette near potential substrate proteins important for spermatogenesis.

RESULTS

TLRR and PP1 interact with one another as demonstrated by co-immunoprecipitation and the yeast two-hybrid assay. TLRR binds more strongly to PP1 gamma 2 than it does to PP1 alpha. Anti-phosphoserine antibodies immunoprecipitate TLRR from testis lysate, indicating that TLRR is a phosphoprotein. TLRR is part of a complex in testis that includes cytoskeletal proteins and constituents of the ubiquitin-proteasome pathway. The TLRR complex purified from 3T3 cells contains similar proteins, co-localizes with microtubules and is enriched at the microtubule-organizing centre. TLRR is also detected near the centrosome of elongated, but not mid-stage, spermatids.

CONCLUSION

We demonstrate here that TLRR interacts with PP1, particularly the testis-specific isoform, PP1 gamma 2. Immunoaffinity purification confirms that TLRR is associated with the spermatid cytoskeleton. In addition, proteins involved in protein stability are part of the TLRR complex. These results support our hypothesis that TLRR links signalling molecules to the spermatid cytoskeleton in order to regulate important substrates involved in spermatid transformation. The translocation of TLRR from the manchette to the centrosome region suggests a possible role for this protein in tail formation. Our finding that TLRR is associated with microtubules in cultured cells suggests that TLRR may play a common role in modulating the cytoskeleton in other cell types besides male germ cells.

Transcripts of enriched germ cells responding to heat shock as potential markers for porcine semen quality

A cDNA microarray-assisted experiment was conducted to survey genes that respond early to heat shock in enriched immature porcine germ cells; the 5'-UTR flanking the highest upregulated gene, heat shock 105/110 kDa protein 1 (Hsph1 or Hsp105), in response to heat shock was also investigated. We established a porcine testis cDNA microarray with 9944 transcripts from two libraries constructed from the testes of mature boars, with or without heat shock. After a mild heat shock treatment (39 degrees C for 1h and recovered at 34 degrees C for 2h), 380 transcripts demonstrated significant gene expression in enriched immature germ cells; 326 were upregulated and 54 were downregulated. Ten transcripts of interest exhibiting significance analysis of microarrays (SAM) scores higher than the median were subjected to quantitative real-time PCR; three (Hsp105, Hspa4l and Thap4) were upregulated >1.5-fold. The sequence of the 5'-UTR of Hsp105, the highest upregulated transcript, was cloned and analyzed. A single nucleotide polymorphism (SNP) was found at position -762 (C or T) upstream of the translational start site (ATG codon). Only two genotypes (CC or TC) were found in the mature boars that were studied (n=31). A heterozygous genotype (TC) at this SNP site revealed an elevated percentage of morphologically normal sperm during hot and cold seasons; this SNP may be a useful marker for semen quality in boars. Furthermore, the cell-model established from enriched primitive germ cells has potential for the study of reproduction in mature animals.

MPSS profiling of embryonic gonad and primordial germ cells in chicken

The massively parallel signature sequencing (MPSS) provides a greater depth of coverage than expressed sequence tag scan or microarray and provides a comprehensive expression profile. We used the MPSS technology to uncover gene expression profiling in the early embryonic gonads and primordial germ cells (PGCs) in the chicken. Total numbers of sequenced signatures were 1,012,533 and 995,676 for the PGCs and gonad, respectively. Using a noise distribution model, we found that 1.67% of all signatures are expressed at a higher level in PCGs and 2.81% of all signatures are expressed at a higher level in the gonad. The MPSS data are presented via an interactive web interface available at http://snugenome.snu.ac.kr/MPSS . The MPSS data have been submitted to the Gene Expression Omnibus of the National Center for Biotechnology Information (accession number GSM137300 and GSM137301 for PGCs and gonad, respectively).

Developmental changes of heat-shock proteins in porcine testis by a proteomic analysis

Heat-shock proteins (HSPs) are important in spermatogenesis. This study investigated developmental changes in the expression of major HSPs in porcine testis. The testis from five immature (mean age 2.9+/-0.1 months) and five mature boars (35.7+/-14.0 months) were examined. Two-dimensional polyacrylamide gel electrophoresis was conducted and proteins were identified by Western blotting and/or matrix-assisted laser desorption/ionization mass spectrometry. Moreover, the 90, 70, and 60 kDa HSPs, 70 kDa heat-shock cognate protein (HSC 70), tubulin, and actin were quantified on two-dimensional gels. Protein spots were quantified by densitometry, combined with a computer-assisted image analysis system. Immunohistochemistry was performed to analyze the expression pattern of major HSPs and beta-tubulin in testis. One isoform of HSP 90 (HSP 90 alpha), two isoforms of HSC 70 (HSC 70a and HSC 70c), one isoform of HSP70 (HSP 70e), and tubulin increased after sexual maturation (P<0.05). A testis-specific HSP70 (P70t) was markedly increased in the testes of sexually mature boars. Meanwhile, levels of actin and some isoforms of HSPs including 60 kDa HSP remained similar in both groups. These observations were further confirmed by immunohistochemistry; therefore, the upregulation of protein expression in the adult testis could be attributed to a higher level of protein expression and the number of cells that were HSPs-positive already resided in the immature testis. The differential expression of major HSPs suggested that they may be important in porcine spermatogenesis.

Single nucleotide polymorphisms of the heat shock protein 90 gene in varicocele-associated infertility

PURPOSE

Varicoceles are associated with impaired testicular function and male infertility, but the molecular mechanisms by which fertility is affected have not been satisfactorily explained. Spermatogenesis might be affected by increased scrotal temperature, such as that caused by varicocele. HSP90 is a molecular chaperone expressed in germ cells and is related to spermatogenesis, motility, and both heat and oxidative stress. Possible correlations between coding single region nucleotide polymorphisms (cSNPs) in the HSP90 gene in patients with varicocele associated with infertility were analyzed, and polymorphisms in these exons were characterized through DNA sequencing.

MATERIALS AND METHODS

PCR-SSCP and DNA sequencing were used to search for mutations in 18 infertile patients with varicocele, 11 patients with idiopathic infertility and 12 fertile men. DNA was extracted from leucocytes for PCR amplification and SSCP analysis. DNA from samples with an altered band pattern in the SSCP was then sequenced to search for polymorphisms.

RESULTS

Three silent polymorphisms that do not lead to amino acid substitutions were identified.

CONCLUSION

Mutations in the HSP90 gene do not appear to be a common cause of male factor infertility. The low incidence of gene variation, or SNPs, in infertile men demonstrates that this gene is highly conserved and thus confirms its key role in spermatogenesis and response to heat stress.

Differential expression of a Bombyx mori AHA1 homologue during spermatogenesis

The AHA1 (activator of Hsp90 ATPase) family of proteins were exclusively conserved from yeast to humans, but little is known about their tissue distribution or biological function. In this study, a cDNA for a Bombyx mori AHA1 homologue, BmAHA1, was isolated from the testes of larvae on day 3 of the fifth instar using an mRNA differential display method. This cDNA encodes a protein with 341 amino acid residues. Gene expression studies revealed that BmAHA1 mRNA occurred prominently in the testes. In situ hybridization and immunostaining showed that the BmAHA1 mRNA signals were strongly detected in spermatogonial cells and primary spermatocytes at the fifth larval instar stage, whereas the BmAha1 protein was abundant in round and elongated spermatids at the pupal stage. The localization pattern of the accumulated protein in the elongated spermatids was reminiscent of that reported previously for microtubules, but the BmAha1 protein showed a decrease in apparent concentration during maturation process. The stage- and cell-specific expression indicated that BmAha1 might play a role in silkworm spermatogenesis, especially in postmeiotic differentiation.

Prenatal estrogen exposure differentially affects estrogen receptor-associated proteins in rat testis gonocytes

We previously reported that gonocytes from 3-day-old rat testes proliferate in response to estradiol. In the present study, we found that purified gonocytes contained the mRNAs of estrogen receptor beta (ERbeta) and the chaperones Hsp90, p23, and Cyp40, but no inducible Hsp70. Immunoblot analysis showed high levels of ERbeta, Hsp90, p23, Cyp40, and the constitutive Hsc70 in gonocytes. Prenatal exposure to the estrogenic compounds diethylstilbestrol, bisphenol A, genistein, and coumestrol led to significantly increased Hsp90 mRNA levels in testis, but not p23 and Cyp40. In situ hybridization analysis indicated that Hsp90 mRNA was prominent in gonocytes, where it was increased following phytoestrogen exposure, whereas bisphenol A induced a more generalized increase throughout the testis. Immunoblot analysis of testicular extracts demonstrated that Hsp90 protein levels were significantly increased following estrogen exposure, and immunohistochemical analysis indicated that this increase occurred predominantly in gonocytes. By contrast, no change was observed in the expression of Cyp40, p23, and ERbeta, whereas Hsc70 was increased by bisphenol A only. Using an antibody and reverse transcriptase-polymerase chain reaction probes specific for Hsp90alpha, we subsequently confirmed that Hsp90alpha was primarily expressed in gonocytes, and that it was increased following estrogen exposure. Hsp90 immunolocalization in fetal and prepubertal testes showed an increased expression in fetal gonocytes upon estrogen exposure, but no difference in the subsets of Hsp90-positive germ cells in prepubertal testes. These results demonstrate that prenatal estrogen exposure specifically affects Hsp90 expression in gonocytes. Considering the interaction of Hsp90 with several signaling molecules, changes in its expression levels may lead to subsequent changes in gonocyte development.

Hsp90 isoforms: functions, expression and clinical importance

The 90 kDa heat shock protein, Hsp90, is a main functional component of an important cytoplasmic chaperone complex, and it is involved in various cellular processes, such as cell proliferation, differentiation and apoptosis. Identification of Hsp90 as a molecular target of various anticancer drugs highlighted its importance from the clinical point of view. Here we summarize the current knowledge of various Hsp90 isoforms regarding their genomic location, molecular evolution, functional differences, differential induction after various environmental stresses and in pathological conditions as well as the growing importance of discriminating between Hsp90 isoforms in clinical practice.

Tyrosine phosphorylation of HSP-90 during mammalian sperm capacitation

The process of sperm capacitation is correlated with activation of a signal transduction pathway leading to protein tyrosine phosphorylation. Whereas phosphotyrosine expression is an essential prerequisite for fertilization, the proteins that are phosphorylated during capacitation have not yet been identified. In the present study, we observed that a major target of this signaling pathway is the molecular chaperone protein, heat shock protein (HSP)-86, a member of the HSP-90 family of HSPs. We used cross-immunoprecipitation experiments to confirm the tyrosine phosphorylation of HSP-86, a process that is not inhibited by the ansamycin antibiotic, geldanamycin. The general significance of these findings was confirmed by studies in which HSP-90 was also found to be tyrosine phosphorylated in human and rat spermatozoa when incubated under conditions that support capacitation. To our knowledge, these results represent the first report of a protein that undergoes tyrosine phosphorylation during mouse sperm capacitation and the first study implicating molecular chaperones in the processes by which mammalian spermatozoa gain the ability to fertilize the oocyte.

Purification and characterization of porcine testis 90-kDa heat shock protein (HSP90) as a substrate for various protein kinases

We purified a large quantity of HSP90 from porcine testis by hydroxylapatite (HA-HSP90) and SDS-PAGE/electroelution (eluted-HSP90) to explore the molecular mechanism of HSP90 phosphorylation affecting its metabolism. The purified HSP90 was used as an antigen to raise polyclonal antibodies in rabbits. Immunoblot analysis revealed that most purified HSP90 was HSP90alpha. Compared with the commercial anti-HSP90 antibody, the polyclonal antibody raised in this study could specifically detect the testis HSP90 and immunoprecipitate HSP90 from tissue homogenates or cell extracts. Incubation of the purified HSP90 or HSP90 immunoprecipitated from extracts of human A431 cells, Balb/c 3T3 fibroblasts, and porcine testis with [gamma-32P]ATP/Mg2+ resulted in phosphorylation of HSP90. However, the eluted-HSP90 lost its phosphorylation ability when incubated with [gamma-32P]ATP x Mg2+ alone but could be phosphorylated by various protein kinases, including PKA, CKII, kinase FA/GSK-3 alpha, and AK. The order of phosphorylation of HSP90 by these kinases is PKA = CKII > AK >> kinase FA/GSK-3 alpha.

Function of 90-kDa heat shock protein in cellular differentiation of human embryonal carcinoma cells

Heat shock proteins (HSPs) have been recognized as molecules that maintain cellular homeostasis during changes in the environment. Here we report that HSP90 functions not only in stress responses but also in certain aspects of cellular differentiation. We found that HSP90 showed remarkably high expression in undifferentiated human embryonal carcinoma (EC) cells, which were subsequently dramatically down-regulated during in vitro cellular differentiation, following retinoic acid (RA) treatment, at the protein level. Surprisingly, heat shock treatment also triggered the down-regulation of HSP90 within 48 h at the protein level. Furthermore, the heat treatment induced cellular differentiation into neural cells. This down-regulation of HSP90 by heat treatment was shifted to an up-regulation pattern after cellular differentiation in response to RA treatment. In order to clarify the functions of HSP90 in cellular differentiation, we conducted various experiments, including overexpression of HSP90 via gene transfer. We showed that the RA-induced differentiation of EC cells into a neural cell lineage was inhibited by overexpression of the HSP90alpha or -beta isoform via the gene transfer method. On the other hand, the overexpression of HSP90beta alone impaired cellular differentiation into trophoectoderm. These results show that down-regulation of HSP90 is a physiologically critical event in the differentiation of human EC cells and that specific HSP90 isoforms may be involved in differentiation into specific cell lineages.

Expression of heat shock proteins in developing and degenerating rat testes

In the testis, several types of heat shock proteins (HSPs) have been identified and characterized, although the cellular basis of the HSPs remains elusive. In the present study, alterations in the cellular localization of HSPs, including HSP 25, 60, 70, and 90, were studied during the developing and degenerating periods in the rat testis using immunohistochemistry and Western blotting. HSP25 was expressed in neither germ cells nor somatic cells on all days examined. In contrast, HSP 60 was expressed in Leydig cells during neonatal and prepuberty periods, and only in spermatogonia and primary spermatocytes after puberty. HSPs 70 and 90 were expressed in germ cells, Sertoli cells, and Leydig cells during neonatal and early developing testes, and in spermatocytes and round spermatids after puberty. Besides, there was faint expression of HSP 90 protein in spermatogonia in this period. In the degenerative condition, all HSP proteins were markedly expressed in germ cells after surgery. It would appear that HSPs play roles in unique homeostasis in testes.

Sequence features and phylogenetic analysis of the stress protein hsp90alpha in chinook salmon (Oncorhynchus tshawytscha), a poikilothermic vertebrate

We cloned and sequenced a chinook salmon Hsp90 cDNA; sequence analysis shows it to be Hsp90alpha. Phylogenetic analysis supports the hypothesis that alpha and beta paralogs of Hsp90 arose as a result of a gene duplication event and that they diverged early in the evolution of vertebrates, before tetrapods separated from the teleost lineage. Among several differences distinguishing poikilothermic Hsp90alpha sequences from their bird and mammal orthologs, the teleost versions specifically lack a characteristic QTQDQP phosphorylation site near the N-terminus. We used the cDNA to develop an RNA (Northern) blot to quantify cellular Hsp90 mRNA levels. Chinook salmon embryonic (CHSE-214) cells responded to heat shock with a rapid rise in Hsp90 mRNA through 4 h, followed by a gradual decline over the next 20 h. Hsp90 mRNA level may be useful as a stress indicator, especially in a laboratory setting or in response to acute heat stress.

Molecular cloning and characterization of porcine cDNA encoding a 90-kDa heat shock protein and its expression following hyperthermia

We have isolated and sequenced cDNA clones encoding a 90-kDa heat shock protein (HSP90) from a porcine brain cDNA library. The sequence of the 2202-nucleotide coding region showed 88.6% homology with that of the human homologue. Moreover, the deduced amino acid sequence of the porcine hsp90 cDNA was 99.7% identical to that of the human counterpart, with a difference of only three amino acids in a total of 733 residues. Expression of the gene was greatly increased in cultured cells during recovery from heat shock treatment at 45 degrees C for 60 min. Three major transcripts 2.2, 3.0, and 4.1kb in size were detected by Northern blot hybridization. These transcripts were further identified in a whole-pig hyperthermia experiment. These three hsp90 transcripts were constitutively expressed in porcine tissues including kidney, liver, brain, and heart, and their levels were markedly enhanced during recovery from 30-min hyperthermia treatment at 43 degrees C. Furthermore, we found that HSP90 was preferentially expressed in pituitary gland, brain, adrenal gland, and testis, in comparison to the other tissues.

Stage-specific expression and cellular localization of the heat shock factor 2 isoforms in the rat seminiferous epithelium

Heat shock transcription factors (HSFs) are generally known as regulators of cellular stress response. The mammalian HSF1 functions as a classical stress factor, whereas HSF2 is active during certain developmental processes, including embryogenesis and spermatogenesis. In the present study, we examined HSF2 expression at specific stages of the rat seminiferous epithelial cycle. We found that expression of the alternatively spliced HSF2-alpha and HSF2-beta isoforms is developmentally regulated in a stage-specific manner. Studies on cellular localization demonstrated that HSF2 is present in the nuclei of early pachytene spermatocytes at stages I-IV and in the nuclei of round spermatids at stages V-VIIab. In contrast a strong HSF2 immunoreactivity was detected in small distinct cytoplasmic regions from zygotene spermatocytes to maturation phase spermatids. Immunoelectron microscopic analysis revealed that these structures are mainly cytoplasmic bridges between germ cells. Our results on cellular localization of HSF2 and stage-specific expression of the HSF2 isoforms indicate that HSF2, in addition to its function as a nuclear transcription factor, may be involved in other cellular processes during spermatogenesis, possibly in the sharing process of gene products between the germ cells.

Heat shock genes and the heat shock response in zebrafish embryos

Heat shock genes exhibit complex patterns of spatial and temporal regulation during embryonic development in a wide range of organisms. Our laboratory has initiated an analysis of heat shock protein gene expression in the zebrafish, a model system that is now utilized extensively for the examination of early embryonic development of vertebrates. We have cloned members of the zebrafish hsp47, hsp70,\i and hsp90 gene families and shown them to be closely related to their counterparts in higher vertebrates. Whole mount in situ hybridization and Northern blot analyses have revealed that these genes are regulated in distinct spatial, temporal, and stress-specific manners. Furthermore, the tissue-specific expression patterns of the hsp47 and hsp90 alpha genes correlate closely with the expression of genes encoding known chaperone targets of Hsp47 and Hsp90 in other systems. The data raise a number of interesting questions regarding the function and regulation of these heat shock genes in zebrafish embryos during normal development and following exposure to environmental stress.

HSP90alpha gene expression may be a conserved feature of vertebrate somitogenesis

We have previously demonstrated that the hsp90alpha and hsp90beta genes in zebrafish are expressed in dramatically different spatial and temporal patterns in early embryos. In the case of hsp90alpha, expression is spatially restricted within the somites to putative myogenic cells which also express mRNA encoding the myogenic bHLH transcription factor myoD and is downregulated along with myoD following myogenesis. In the present study, we have examined hsp90alpha gene expression in developing chicken embryos using a gene-specific probe. We show that hsp90alpha gene expression is also localized to a subset of cells within the somites of chicken embryos and that the expression pattern correlates closely to that observed for myoD. Furthermore, expression of the hsp90alpha gene is strongly upregulated throughout the embryo following heat shock in a manner similar to that observed in heat-shocked zebrafish embryos. The data suggest that the hsp90alpha gene may play an evolutionarily conserved role during somitogenesis in vertebrates in addition to providing protection to all cells of the embryo following stress.

Cloning and characterization of the promoter for murine 84-kDa heat-shock protein

The 90-kDa heat-shock (HS) proteins (HSP90) are members of the HSP family. Their synthesis is inducible by HS and a variety of stress signals. HSP90 is also abundant under normal physiological conditions and its synthesis can be regulated during growth and differentiation. Therefore, HSP90 is speculated to have important biological functions, in addition to its role in mediating stress responses. However, the mechanism(s) regulating hsp90 gene expression in nonstressed cells is poorly understood. As a prerequisite towards understanding the basis for hsp90 regulation, we have cloned and characterized the 5' flanking region of murine hsp84, one of two genes which code for HSP90 proteins. Full basal promoter activity of hsp84 was found to be associated with a 627-bp region immediately upstream from the transcription start point (tsp). Sequence analysis revealed several putative regulatory elements, including a HS element (HSE), an AP1-binding site (AP1), a cyclic AMP response element (CRE), and four stimulatory protein-1-binding sites (SP1). HS inducibility required the HSE which was bound by HS transcription factor-1(HSF-1) present in extracts prepared from cells exposed to HS. The HSE was not required for basal (non-HS) expression, but, interestingly, two protein-HSE complexes, devoid of HSF-1 and HSF-2, were formed under these conditions. The potential significance of these findings to the expression of hsp84 under normal physiological conditions is discussed.

Developmental expression of heat shock protein 60 (HSP60) in the rat testis and ovary

Heat shock protein 60 (HSP60), a member of the chaperonin family, has an essential role in mediating correct folding of nuclear encoded proteins imported to mitochondria. We have investigated immunocytochemical expression of HSP60 in developing fetal, newborn, postnatal, and pubertal testis and ovary, and in the adult ovary of the rat. In the fetal gonads, HSP60 was expressed in the germ cells organized into sex cords and in the developing Leydig cells of the testis. In the pubertal testis, Leydig cells were strongly, spermatogonia and premeiotic spermatocytes moderately labeled, spermatids unlabeled. In the postnatal ovary, oocytes at all stages of folliculogenesis were positive for HSP60. In the pubertal ovary, glandular theca cells, and in the mature ovary, also the cells of the corpora lutea exhibited intense cytoplasmic labeling. At the electron microscopic level, immunogold particles were localized in the mitochondrial matrix, and in the Western blot analysis the antibody detected one single band of 60 kDa. Anti-HSP60 labeling in male and female sex steroid producing cells and their progenitors seems to be coordinated with the functional differentiation of these endocrine cells of the gonad. In the oocytes, a key element required for proper folding of imported mitochondrial proteins seems to be constitutively expressed throughout folliculogenesis. However, the data suggest that in the male germ cells mitochondrial chaperonin HSP60 is either not needed during the haploid phase of spermatogenesis or its level becomes extensively reduced and therefore undetectable by the methods used in the study.

Expression of heme oxygenase-1 (HSP32) in human prostate: normal, hyperplastic, and tumor tissue distribution

OBJECTIVES

Heme oxygenase isozymes, HO-1 and HO-2, are members of the stress/heat shock (HSP) family of proteins, with the known function of cleaving the heme molecule to biliverdin, iron, and carbon monoxide. The aim of this study was to examine the pattern of tissue expression of HO-1 in the human prostate under different states of proliferation and differentiation and to investigate whether the pattern differs between these states.

METHODS

Presently, we have determined the pattern of tissue expression of the stress-inducible isozyme, HO-1 (HSP32), in human prostate under normal and pathologic conditions, by immunohistochemistry, using polyclonal antibodies, and have measured HO-1 and HO-2 mRNA levels in normal prostate and benign prostatic hyperplasia (BPH) by Northern blotting. The activity of prostate to catalyze heme degradation was also assessed.

RESULTS

In normal and BPH tissue, columnar epithelial cells of acini and ducts and cells in stroma displayed HO-1 immunoreactivity; in all cells, perinuclear staining was prominent. In BPH tissue, however, a more intense staining of the epithelial cells occurred, with notable staining of the basal cells. In undifferentiated malignant tumors, intense HO-1 staining was manifest in nearly all tumor cells, and also in the epithelial lining of blood vessels. HO-1 in the prostate tissue was found catalytically active and oxidatively cleaved the heme molecule (Fe-protoporphyrin IX) to biliverdin. Northern blot analysis shows that two forms of HO are present in the human prostate. Compared with normal tissue, predominantly hyperplastic tissue demonstrates a pronounced increase in the approximately 1.8 kb mRNA that hybridizes to the rat HO-1 probe. The levels of two transcripts, approximately 1.3 and approximately 1.7 kb, that hybridize to the rat HO-2 probe are not increased in BPH tissue.

CONCLUSIONS

The finding that HO-1 expression is increased in BPH and malignant prostate tissue is consistent with a role for this stress protein in the pathogenesis of BPH and prostate cancer; in the context of iron metabolism, an argument is made in support of this possibility.

Sense and antisense transcripts of the developmentally regulated murine hsp70.2 gene are expressed in distinct and only partially overlapping areas in the adult brain

We have examined the spatial pattern of expression of a member of the hsp70 gene family, hsp70.2, in the mouse central nervous system. Surprisingly, RNA blot analysis and in situ hybridization revealed abundant expression of an 'antisense' hsp70.2 transcript in several areas of adult mouse brain. Two different transcripts recognized by sense and antisense riboprobes for the hsp70.2 gene were expressed in distinct and only partially overlapping neuronal populations. RNA blot analysis revealed low levels of the 2.7 kb transcript of hsp70.2 in several areas of the brain, with highest signal in the hippocampus. Abundant expression of a slightly larger (approximately 2.8 kb) 'antisense' transcript was detected in several brain regions, notably in the brainstem, cerebellum, mesencephalic tectum, thalamus, cortex, and hippocampus. In situ hybridization revealed that the sense and antisense transcripts were both predominantly neuronal and localized to the same cell types in the granular layer of the cerebellum, trapezoid nucleus of the superior olivary complex, locus coeruleus and hippocampus. The hsp70.2 antisense transcripts were particularly abundant in the frontal cortex, dentate gyrus, subthalamic nucleus, zona incerta, superior and inferior colliculi, central gray, brainstem, and cerebellar Purkinje cells. Our findings have revealed a distinct cellular and spatial localization of both sense and antisense transcripts, demonstrating a new level of complexity in the function of the heat shock genes.

Distinct transcripts are recognized by sense and antisense riboprobes for a member of the murine HSP70 gene family, HSP70.2, in various reproductive tissues

The expression of hsp70.2, an hsp70 gene family member, originally characterized by its high levels of expression in germ cells in the adult mouse testis, was detected in several other reproductive tissues, including epididymis, prostate, and seminal vesicles, as well as in extraembryonic tissues of mid-gestation fetuses. In addition, hybridization with RNA probes transcribed in the sense orientation surprisingly indicated the presence of slightly larger "antisense" transcripts in several tissues. The levels of antisense transcripts varied among the tissues, with the highest signal detected in the prostate and no signal being detectable in the testis. Consistent with these results, in situ hybridization analysis clearly localized the sense-orientation transcripts to pachytene spermatocytes, while no antisense-orientation transcripts were observed in adjacent sections of the same tubules. Our findings have thus shown that although hsp70.2 was expressed abundantly and in a highly stage-specific manner in the male germ line, it was also expressed in other murine tissues. Furthermore, we have made the surprising observation of antisense transcription of the hsp70.2 gene in several mouse tissues, revealing another level of complexity in the regulation and function of heat shock proteins.

Messenger RNA expression of heat shock proteins (HSPs) during ocular development

The heat shock proteins (HSPs) are believed to act as molecular chaperones which appear to play some roles in regulation of normal protein folding and also in preventing damage to protein structures under various conditions of environmental stress. We examined the expression of the major HSP families, HSP60, 70 and 90 families and small HSP32, at the mRNA level in ocular development. Expression of HSP32, HSP60, HSP70, HSP84, HSP86 and heat shock cognate protein (HSC)70 mRNAs was examined by in situ hybridization. HSC70, HSP84, HSP86 and HSP60 mRNAs were expressed strongly in all ocular tissues during early stages 3 to 5, corresponding to embryonic day (E)11.5 to E14.5. At stages 6 to 7 (E15.5 to E18.5), the expression of these four mRNA species was decreased markedly in most ocular tissue, while in the retina strong HSC70 and HSP86 mRNA expression was still detected. HSP32 and HSP70 mRNAs were not detected at any stage. These results suggest that the expression of HSPs is developmentally regulated through ocular organogenesis, and the proteins may play some important roles in ocular development.

Characterization of the heat shock protein P70 in rat spermatogenic cells

A number of hsp70-like proteins are associated with developing male germ cells. One of these molecules, P70, is not sensitive to heat stress and is germ cell-specific, and its expression is developmentally regulated. We have characterized the association of the rat P70(rP70) with differentiating germ cells in the testis and with posttesticular sperm. An antibody originally raised against human sperm proacrosin (designated C3; Sigel et al., 1987: J Reprod Immunol 11:307-319) was found to immunostain rP70 by immunoblot analysis and was used in subsequent studies of the rP70 molecule. The C3 antibody reacted with P70 isoforms in rat, human, mouse, guinea pig, boar, and rooster testicular homogenates. In the developing rat testis, abundant rP70 protein levels were first detected on postnatal day 22, with upregulation to adult levels occurring after postnatal day 28. Purified populations of adult rat pachytene spermatocytes, round spermatids, and elongating spermatids, isolated by unit gravity velocity sedimentation, all expressed rP70. Posttesticular sperm exhibited a loss of the rP70 molecule; caput epididymal sperm were weakly immunoreactive for rP70, but no immunoreactivity was observed in either cauda epididymal sperm or epididymal fluid. In contrast to human ejaculated sperm, rat ejaculated sperm did not express rP70. The loss of P70 from rat posttesticular sperm may reflect species-specific differences in P70 functions, which are thought to include a role in the structural modifications that occur during germ cell differentiation.

Dynamic Hsp83 RNA localization during Drosophila oogenesis and embryogenesis

Hsp83 is the Drosophila homolog of the mammalian Hsp90 family of regulatory molecular chaperones. We show that maternally synthesized Hsp83 transcripts are localized to the posterior pole of the early Drosophila embryo by a novel mechanism involving a combination of generalized RNA degradation and local protection at the posterior. This protection of Hsp83 RNA occurs in wild-type embryos and embryos produced by females carrying the maternal effect mutations nanos and pumilio, which eliminate components of the posterior polar plasm without disrupting polar granule integrity. In contrast, Hsp83 RNA is not protected at the posterior pole of embryos produced by females carrying maternal mutations that disrupt the posterior polar plasm and the polar granules--cappuccino, oskar, spire, staufen, tudor, valois, and vasa. Mislocalization of oskar RNA to the anterior pole, which has been shown to result in induction of germ cells at the anterior, leads to anterior protection of maternal Hsp83 RNA. These results suggest that Hsp83 RNA is a component of the posterior polar plasm that might be associated with polar granules. In addition, we show that zygotic expression of Hsp83 commences in the anterior third of the embryo at the syncytial blastoderm stage and is regulated by the anterior morphogen, bicoid. We consider the possible developmental significance of this complex control of Hsp83 transcript distribution.

Dynamic Hsp83 RNA localization during Drosophila oogenesis and embryogenesis

Hsp83 is the Drosophila homolog of the mammalian Hsp90 family of regulatory molecular chaperones. We show that maternally synthesized Hsp83 transcripts are localized to the posterior pole of the early Drosophila embryo by a novel mechanism involving a combination of generalized RNA degradation and local protection at the posterior. This protection of Hsp83 RNA occurs in wild-type embryos and embryos produced by females carrying the maternal effect mutations nanos and pumilio, which eliminate components of the posterior polar plasm without disrupting polar granule integrity. In contrast, Hsp83 RNA is not protected at the posterior pole of embryos produced by females carrying maternal mutations that disrupt the posterior polar plasm and the polar granules--cappuccino, oskar, spire, staufen, tudor, valois, and vasa. Mislocalization of oskar RNA to the anterior pole, which has been shown to result in induction of germ cells at the anterior, leads to anterior protection of maternal Hsp83 RNA. These results suggest that Hsp83 RNA is a component of the posterior polar plasm that might be associated with polar granules. In addition, we show that zygotic expression of Hsp83 commences in the anterior third of the embryo at the syncytial blastoderm stage and is regulated by the anterior morphogen, bicoid. We consider the possible developmental significance of this complex control of Hsp83 transcript distribution.

Widespread constitutive expression of HSP90 messenger RNA in rat brain

The distribution of constitutively expressed mRNA encoding 2 isoforms of heat shock protein 90 (HSP90) was investigated in adult rat brain by in situ hybridization with 35S-labeled cRNA probes. HSP90 mRNA density was estimated by semiquantitative autoradiography and by microscopic analysis. The distribution of HSP90 transcripts was similar for the 2 probes. HSP90 mRNA was widespread but not ubiquitous, and labeling intensity varied among different regions. In particular, HSP90 mRNA was abundant in limbic system-related structures, such as the hippocampus, amygdala, mamillary body, piriform cortex, enthorhinal cortex, bed nucleus of the stria terminalis, medial habenular nucleus, and preoptic hypothalamic nuclei. The highest abundance of mRNA was detected in the Purkinje cell layer of the cerebellum. High abundance was also present in pineal body, choroid plexus, cerebellar granule cell layer, and cranial nerve nuclei. HSP90 mRNA was present in moderate abundance throughout the cortical gray mantle, in the caudate-putamen, most other thalamic and hypothalamic nuclei, the pontine and spinal gray matter, and the anterior lobe of the hypophysis. Weak hybridization was observed in white matter fiber tracts, glial cells, and leptomeninges, and none was observed in endothelial cells and the smooth muscle of the cerebral microvasculature. Our findings suggest that HSP90 gene products may serve constitutive neuron-specific functions in the unstressed brain.

Tissue-specific expression of heat shock proteins of the mouse in the absence of stress

The steady-state levels of four members of the heat shock proteins families (HSP84, HSC73, HSP71, and HSP25) were examined by immunoblot analysis of several different tissues of young and adult mice in the absence of stress. These hsps were detected in all tissues but their level was variable. The levels of HSC73 and HSP84 varied only slightly between different tissues in either young or adult mice, with the exception of skin where these hsps were found in reduced amounts. In contrasts, the stress-inducible member of the HSP70 family, HSP71, was found to be expressed in all tissues but in amounts which differed by as much as two orders of magnitude between tissues. In general, the levels of both HSP71 and HSP25 were found to be tissue dependent, with higher levels found in tissues such as stomach, intestine, colon and bladder, tissues which are exposed to toxic environmental or metabolic products, and which may concentrate these substances by water resorption and/or be exposed to them for longer periods. The levels of HSP71 and HSP25 were generally positively correlated both in young and adult mice although this correlation was not found in certain tissues such as kidney, testes, and bone. Tissues of young mice contained lower amounts of HSP25 and HSP71 than were found in the same tissues from adults. We conclude that hsps are expressed in all tissues of the mouse in the absence of stress and that some organs, particularly those exposed to potentially toxic metabolites, show a higher level of expression of HSP71 and HSP25.

HSP86 and HSP84 exhibit cellular specificity of expression and co-precipitate with an HSP70 family member in the murine testis

This study extends to the protein level our previous observations, which had established the stage and cellular specificity of expression of hsp86 and hsp84 in the murine testis in the absence of exogenous stress. Immunoblot analysis was used to demonstrate that HSP86 protein was present throughout testicular development and that its levels increased with the appearance of differentiating germ cells. HSP86 was most abundant in the germ cell population and was present at significantly lower levels in the somatic cells. By contrast, the HSP84 protein was detected in the somatic cells of the testis rather than in germ cells. The steady-state levels of HSP86 and HSP84 paralleled the pattern of the expression of their respective mRNAs, suggesting that regulation at the level of translation was not a major mechanism controlling hsp90 gene expression in testicular cells. Immunoprecipitation analysis revealed that a 70-kDa protein coprecipitated with the HSP86/HSP84 proteins in testicular homogenates. This protein was identified as an HSP70 family member by immunoblot analysis, suggesting that HSP70 and HSP90 family members interact in testicular cells.

The small heat shock protein hsp25 is accumulated in P19 embryonal carcinoma cells and embryonic stem cells of line BLC6 during differentiation

Murine embryonal carcinoma and embryonic stem cell lines were investigated with regard to the occurrence of the small heat shock protein hsp25 during cell growth and differentiation. In the embryonal carcinoma cell line F9 considerable constitutive levels of hsp25 were observed which could be slightly increased by treatment with retinoic acid. No hsp25 was found, however, in the embryonal carcinoma cell line PCC4. When analyzing the pluripotent embryonal carcinoma cell line P19 and the pluripotent embryonic stem cell line BLC6, both characterized by high differentiation capacity, no hsp25 was observed under cell culture conditions maintaining the undifferentiated state. Induction of differentiation caused by prolonged cell culture, retinoic acid treatment, or embryoid body formation, however, resulted in an increase of the level of hsp25. The finding that hsp25 is accumulated in a differentiation-dependent manner suggests that this protein is associated with processes involved in differentiation. Therefore, hsp25 can be regarded as a marker of differentiation in the investigated embryonal carcinoma cell line P19 and the embryonic stem cell line BLC6.

Mammalian heat shock protein families. Expression and functions

When prokaryotic or eukaryotic cells are submitted to a transient rise in temperature or to other proteotoxic treatments, the synthesis of a set of proteins called the heat shock proteins (hsp) is induced. The structure of these proteins has been highly conserved during evolution. The signal leading to the transcriptional activation of the corresponding genes is the accumulation of denatured and/or aggregated proteins inside the cells after stressful treatment. The expression of a subset of hsp is also induced during early embryogenesis and many differentiation processes. Two different functions have been ascribed to hsp: a molecular chaperone function: chaperones mediate the folding, assembly or translocation across the intracellular membranes of other polypeptides, and a role in protein degradation: some of the essential components of the cytoplasmic ubiquitin-dependent degradative pathway are hsp. These functions of hsp are essential in every living cell. They are required for repairing the damage resulting from stress.