Induction of Apg-1, a member of the heat shock protein 110 family, following transient forebrain ischemia in the rat brain

Expression of Heat Shock Protein 105 in Cutaneous Squamous Cell Carcinoma: Correlation with Clinicopathological Characteristics

Background

Heat shock proteins (HSPs), a group of heat stress proteins, are characterized by highly conserved properties. Malignant transformation is a cellular stress, and the expression of HSPs may be affected during this process. Heat shock protein 105 (HSP105) is a protective protein that has long been observed in many cancer types, but little attention has been given to cutaneous squamous cell carcinoma (CSCC). As such, the objectives of this study were to observe the expression of HSP105 on CSCC and evaluate its correlation with clinicopathological characteristics.

Methods

This retrospective study enrolled 60 patients with CSCC. The patients’ clinical data, including sex, age, tumor location, tumor type, and degree of pathological differentiation, were collected. The expression of HSP105 was measured by Western blot and immunohistochemical staining.

Results

HSP105 expression was decreased in CSCC (HSCORE=0.65 (0.30, 1.98)) compared with normal skin (HSCORE=2.20 (1.50, 2.80)) (P<0.001). These results were consistent with the Western blot analysis. HSP105 immunostaining of Bowen disease (HSCORE=1.28 (1.08, 2.40)) revealed higher expression than in verrucous carcinoma (HSCORE=0.30 (0.23, 0.85)), keratoacanthoma (HSCORE=0.53 (0.29, 0.93)) and acantholytic squamous cell carcinoma (HSCORE=0.53 (0.41, 0.68) (P<0.01)). Poorly differentiated CSCC showed significantly higher expression of HSP105.

Conclusion

Our study reveals for the first time that the expression of HSP105 is decreased in CSCC. We suggest that the molecular mechanisms underlying the differential expression of HSP deserve a more rigorous future study, the results of which might explain its role in carcinogenesis and its potential as a target for selective tumor therapy.

Nogo-A couples with Apg-1 through interaction and co-ordinate expression under hypoxic and oxidative stress

Nogo-A is the largest isoform of the Nogo/RTN4 (reticulon 4) proteins and has been characterized as a major myelin-associated inhibitor of regenerative nerve growth in the adult CNS (central nervous system). Apart from the myelin sheath, Nogo-A is expressed at high levels in principal neurons of the CNS. The specificity of Nogo-A resides in its central domain, NiG. We identified Apg-1, a member of the stress-induced Hsp110 (heat-shock protein of 110 kDa) family, as a novel interactor of NiG/Nogo-A. The interaction is selective because Apg-1 interacts with Nogo-A/RTN4-A, but not with RTN1-A, the closest paralogue of Nogo-A. Conversely, Nogo-A binds to Apg-1, but not to Apg-2 or Hsp105, two other members of the Hsp110 family. We characterized the Nogo-A–Apg-1 interaction by affinity precipitation, co-immunoprecipitation and proximity ligation assay, using primary hippocampal neurons derived from Nogo-deficient mice. Under conditions of hypoxic and oxidative stress we found that Nogo-A and Apg-1 were tightly co-regulated in hippocampal neurons. Although both proteins were up-regulated under hypoxic conditions, their expression levels were reduced upon the addition of hydrogen peroxide. Taken together, we suggest that Nogo-A is closely involved in the neuronal response to hypoxic and oxidative stress, an observation that may be of relevance not only in stroke-induced ischaemia, but also in neuroblastoma formation.

The nerve growth inhibitor Nogo-A selectively binds to the heat-shock protein Apg-1 and the expression levels of these two interactors are co-regulated under different forms of stress in neurons.

Proteomic analysis for testis of mice exposed to carbon ion radiation

This paper investigates the mechanism of action of heavy ion radiation (HIR) on mouse testes. The testes of male mice subjected to whole body irradiation with carbon ion beam (0.5 and 4Gy) were analyzed at 7days after irradiation. A two-dimensional gel electrophoresis approach was employed to investigate the alteration of protein expression in the testes. Spot detection and matching were performed using the PDQuest 8.0 software. A difference of more than threefold in protein quantity (normalized spot volume) is the standard for detecting differentially expressed protein spots. A total of 11 differentially expressed proteins were found. Protein identification was performed using matrix-assisted laser desorption/ionization tandem time-of-flight mass spectrometry (MALDI-TOF-TOF). Nine specific proteins were identified by searching the protein sequence database of the National Center for Biotechnology Information. These proteins were found involved in molecular chaperones, metabolic enzymes, oxidative stress, sperm function, and spermatogenic cell proliferation. HIR decreased glutathione activity and increased malondialdehyde content in the testes. Given that Pin1 is related to the cell cycle and that proliferation is affected by spermatogenesis, we analyzed testicular histological changes and Pin1 protein expression through immunoblotting and immunofluorescence. Alterations of multiple pathways may be associated with HIR toxicity to the testes. Our findings are essential for studies on the development, biology, and pathology of mouse testes after HIR in space or radiotherapy.

Gene expression of Hsp70, Hsp90 and Hsp110 families in normal palate and cleft palate during mouse embryogenesis

Most previous studies focused on a small number of heat shock proteins (Hsps) and their relationships with embryogenesis, and the actual roles of these Hsps in normal and abnormal embryonic development remain unclear. It was found in the present systemic study that except for Grp170, whose expression was not detectable at GD18, all 19 Hsps of Hsp70, Hsp90 and Hsp110 families were expressed in the normal development of embryonic palate tissue in mice, but their expression patterns varied with different Hsps, presenting as a correlation with the developmental phases. In the treatment group by all-trans retinoic acid (atRA), the messenger RNA (mRNA) abundance of HspA1A, HspA1L, HspA8, HspA9, HspA12A, HspA12B, HspA13, HspA14, Hsp90AA1, Hsp90AB1, Grp94, Trap1, Hsp105, Hsp110 and Grp170 was higher in the palates at GD11 (the beginning of palate development), the mRNA abundance of HspA1A, HspA12A and HspA12B was higher at GD18 (before birth) and an mRNA expression peak of HspA1L, HspA8, HspA9, Hsp90AA1, Grp94, Hsp110 and Grp170 was observed at GD17. The mRNA abundance of most genes in atRA-induced cleft palates of the treatment group was different from that of the control group. Grp78, HspA14 and Hsp105 were closely associated with the normal palate development and cleft palate in mouse embryo, possibly as palate development-related genes. Except Grp170, the other genes may be closely associated with the development of mouse palates through participating in the stress response process and/or the antiapoptosis process.

The influence of loud sound stress on expression of osmotic stress protein 94 in the murine inner ear

Osmotic stress protein 94 (OSP94), a member of the heat shock protein 110/SSE subfamily, is expressed in certain organs such as the kidney, testis, and brain where it can act as a molecular chaperon. In general, its alteration in expression is in response to hyper-ionic and osmotic stress as well as heat shock stress. Since many cells in the inner ear are involved in active ion transportation and are constantly exposed to two ionic different environments, we hypothesize that OSP94 may be expressed in the inner ear and its expression may be influenced by loud sound stress (LSS). With immunohistochemistry combined with confocal microscopy, immunoblotting, and reverse transcription polymerase chain reaction techniques, we found that OSP94 was widely expressed in various cells in the murine cochlea including the stria vascularis, the organ of Corti, the interdental cells, spiral ganglion cells, the spiral ligament, and Reissner's membrane. Under the unstressed condition, the transcription and protein level of OSP94 expression in the inner ear was quantitatively similar to that of the kidney. Furthermore, its expression in the inner ear by LSS from broadband noise at 117 dB/SPL was upregulated, but remained unchanged in the kidney. In particular, the upregulation of OSP94 in the cochlear lateral wall tissue was slowly elicited in a LSS time-dependent manner compared with the response of two other HSPs; HSP25 and HSP70 are considered to play a cytoprotective role under stressful conditions. Our results show that OSP94 is expressed in the inner ear and indicate this may be necessary for cells in a special ionic and osmotic environment such as endo-perilymphatic ion compartments. The organ-specific upregulation of OSP94 by acoustic overstimulation reveals that OSP94 in the murine inner ear is potentially important for cellular functional adaptation to LSS.

Glial elements contribute to stress-induced torsinA expression in the CNS and peripheral nervous system

DYT1 dystonia is caused by a single GAG deletion in exon 5 of TOR1A, the gene encoding torsinA, a putative chaperone protein. In this study, central and peripheral nervous system perturbations (transient forebrain ischemia and sciatic nerve transection, respectively) were used to examine the systems biology of torsinA in rats. After forebrain ischemia, quantitative real-time reverse transcriptase-polymerase chain reaction identified increased torsinA transcript levels in hippocampus, cerebral cortex, thalamus, striatum, and cerebellum at 24 h and 7 days. Expression declined toward sham values by 14 days in striatum, thalamus and cortex, and by 21 days in cerebellum and hippocampus. TorsinA transcripts were localized to dentate granule cells and pyramidal neurons in control hippocampus and were moderately elevated in these cell populations at 24 h after ischemia, after which CA1 expression was reduced, consistent with the loss of this vulnerable neuronal population. Increased in situ hybridization signal in CA1 stratum radiatum, stratum lacunosum-moleculare, and stratum oriens at 7 days after ischemia was correlated with the detection of torsinA immunoreactivity in interneurons and reactive astrocytes at 7 and 14 days. Sciatic nerve transection increased torsinA transcript levels between 24 h and 7 days in both ipsilateral and contralateral dorsal root ganglia (DRG). However, increased torsinA immunoreactivity was localized to both ganglion cells and satellite cells in ipsilateral DRG but was restricted to satellite cells contralaterally. These results suggest that torsinA participates in the response of neural tissue to central and peripheral insults and its sustained up-regulation indicates that torsinA may contribute to remodeling of neuronal circuitry. The striking induction of torsinA in astrocytes and satellite cells points to the potential involvement of glial elements in the pathobiology of DYT1 dystonia.

Identification of an overexpressed gene, HSPA4L, the product of which can provoke prevalent humoral immune responses in leukemia patients

OBJECTIVE

To identify leukemia-associated antigens, we applied the serological identification of antigens by the recombinant expression cloning (SEREX) method to a chronic myelogenous leukemia (CML) patient who achieved a cytogenetic response to interferon-alpha.

MATERIALS AND METHODS

Immunoscreening of the cDNA library was performed with sera from a CML patient. Two isolated antigens were used to evaluate the expression pattern using Northern blot analysis and quantitative reverse transcriptase polymerase chain reaction. Western blotting and enzyme-linked immunosorbent assay were also performed for serological analysis.

RESULTS

We identified 14 positive clones, representing five different antigens. Of these, two genes were further validated. One (clone 70) was the human polyribonucleotide nucleotidyltransferase 1 (PNPT1), which is the type I interferon (alpha/beta-responsive gene). The mRNA of clone 70 was ubiquitously expressed in normal human tissues. The other gene (clone 57) was the heat shock 70-kDa protein 4-like (HSPA4L), which is a member of the heat shock protein 110 family, whose mRNA is strongly expressed in normal human testis and overexpressed in leukemia cells. Seroactivity against HSPA4L was detected in 6 of 9 acute myeloid leukemia patients, 4 of 10 acute lymphoblastic leukemia patients, 9 of 11 CML patients, and none of 10 healthy volunteers. Leukemia patients had higher titer of the antibodies against the protein than healthy volunteers.

CONCLUSIONS

These results suggest that HSPA4L, a member of heat shock protein, is highly expressed by leukemia cells, and elicit humoral immune responses in leukemia patients, and it might be a potential target for antileukemia therapy and an antigen-specific immunotherapy for leukemia.

Hsp105 family proteins suppress staurosporine-induced apoptosis by inhibiting the translocation of Bax to mitochondria in HeLa cells

Hsp105 (Hsp105alpha and Hsp105beta), major heat shock proteins in mammalian cells, belong to a subgroup of the HSP70 family, HSP105/110. Previously, we have shown that Hsp105alpha has completely different effects on stress-induced apoptosis depending on cell type. However, the molecular mechanisms by which Hsp105alpha regulates stress-induced apoptosis are not fully understood. Here, we established HeLa cells that overexpress either Hsp105alpha or Hsp105beta by removing doxycycline and examined how Hsp105 modifies staurosporine (STS)-induced apoptosis in HeLa cells. Apoptotic features such as the externalization of phosphatidylserine on the plasma membrane and nuclear morphological changes were induced by the treatment with STS, and the STS-induced apoptosis was suppressed by overexpression of Hsp105alpha or Hsp105beta. In addition, we found that overexpression of Hsp105alpha or Hsp105beta suppressed the activation of caspase-3 and caspase-9 by preventing the release of cytochrome c from mitochondria. Furthermore, the translocation of Bax to mitochondria, which results in the release of cytochrome c from the mitochondria, was also suppressed by the overexpression of Hsp105alpha or Hsp105beta. Thus, it is suggested that Hsp105 suppresses the stress-induced apoptosis at its initial step, the translocation of Bax to mitochondria in HeLa cells.

Heat shock protein 105 is overexpressed in squamous cell carcinoma and extramammary Paget disease but not in basal cell carcinoma

BACKGROUND

Heat shock protein (HSP) 105 is a 105-kDa protein, recently discovered by serological analysis of recombinant cDNA expression libraries prepared from tumour cells (SEREX), and is still undergoing intensive research. SEREX can define strongly immunogenic tumour antigens that elicit both cellular and humoral immunity. Previous studies have shown that HSP105 is a cancer testis antigen and is overexpressed in various internal malignancies. The expression of HSP105 has not been studied in skin cancers.

OBJECTIVES

To assess the expression of HSP105 in skin cancers including extramammary Paget disease (EMPD), cutaneous squamous cell carcinoma (SCC) and basal cell carcinoma (BCC).

METHODS

Samples of EMPD (n = 25), SCC (n = 23, of which three were metastatic lesions) and BCC (n = 23) were collected from patients treated in our department between January 2002 and December 2004. Western blot and immunohistochemical staining methods were used to investigate the expression of HSP105.

RESULTS

Results of Western blot analysis showed overexpression of HSP105 in EMPD and SCC, and minimal expression in BCC. Immunohistochemistry results showed that 56% of EMPD, 60% of primary and 100% of metastatic SCC highly expressed HSP105 while only 13% of BCC lesions showed increased staining.

CONCLUSIONS

EMPD and SCC overexpress HSP105 while BCC does not. Tumours overexpressing HSP105 present ideal candidates for vaccination by HSP105-derived peptides or DNA.

Apg-2 has a chaperone-like activity similar to Hsp110 and is overexpressed in hepatocellular carcinomas

Hepatocellular carcinoma (HCC) is the fifth most common cancer in the world. We constructed subtracted cDNA libraries enriched with genes overexpressed in HCCs. Among the 17 genes identified were molecular chaperones, Hsp110, Hsp90B, and Hsp70-1. Expression of the Hsp110 family members was further analyzed, and increased transcript levels of Hsp110 and Apg-2, but not Apg-1, were found in 12 and 14, respectively, of 18 HCCs. Immunohistochemical analysis demonstrated the overexpression of the proteins in tumor cells. Apg-2 had chaperone ability similar to Hsp110 in a thermal denaturation assay using luciferase, and showed anti-apoptotic activity. These results suggest that the Hsp110 family members play important roles in hepatocarcinogenesis through their chaperoning activities.

DNA microarray analysis of hippocampal gene expression measured twelve hours after hypoxia-ischemia in the mouse

Cell death from cerebral ischemia is a dynamic process. In the minutes to days after an ischemic insult, progressive changes in cellular morphology occur. Associated with these events is the regulation of competing programs of gene expression; some are protective against ischemic insult, and others contribute to delayed cell death. Many genes involved in these processes have been identified, but individually, these findings have provided only limited insight into the systems biology of cerebral ischemia. Attempts to characterize the coordinated expression of large numbers of genes in cerebral ischemia has only recently become possible. Today, DNA microarray technology provides a powerful tool for investigating parallel expression changes for thousands of genes at one time. In this study, adult mice were subjected to 30 minutes of hypoxia-ischemia (HI), and the hippocampus was examined 12 hours later for differential gene expression using a 15K high-density mouse EST array. The genomic response to HI is complex, affecting approximately 7% of the total number of ESTs examined. Assigning differentially expressed ESTs to molecular functional groups revealed that HI affects many pathways including the molecular chaperones, transcription factors, kinases, and calcium ion binding genes. A comprehensive list of regulated genes should prove valuable in advancing our understanding of the pathogenesis of cerebral ischemia.

Identification of alpha-tubulin as an hsp105alpha-binding protein by the yeast two-hybrid system

Hsp105alpha is a mammalian stress protein that belongs to the HSP105/110 family. Hsp105alpha prevents stress-induced apoptosis in neuronal cells and binds to Hsp70/Hsc70 and suppresses the Hsp70 chaperone activity in vitro. In this study, to further elucidate the function of Hsp105alpha, we searched for Hsp105alpha-binding proteins by screening a mouse FM3A cell cDNA library with full-length Hsp105alpha using the yeast two-hybrid system and obtained alpha-tubulin as an Hsp105alpha-binding protein. Hsp105alpha bound directly to alpha-tubulin both in vitro and in vivo. Indirect immunofluorescence analysis with anti-Hsp105 and anti-alpha-tubulin antibodies indicated that Hsp105alpha was colocalized with microtubules. Furthermore, the disorganization of microtubules induced by heat shock was prevented in Hsp105alpha-overexpressing COS-7 cells. These findings suggested that Hsp105alpha associates with alpha-tubulin and microtubules in cells and plays a role in protection of microtubules under conditions of stress.

Enhancement of oxidative stress-induced apoptosis by Hsp105alpha in mouse embryonal F9 cells

Hsp105alpha is one of the major mammalian heat shock proteins that belongs to the HSP105/110 family, and is expressed at especially high levels in the brain as compared with other tissues in mammals. Previously, we showed that Hsp105alpha prevents stress-induced apoptosis in neuronal PC12 cells, and is a novel anti-apoptotic neuroprotective factor in the mammalian brain. On the other hand, we have also demonstrated that Hsp105alpha is expressed transiently at high levels during mouse embryogenesis and is found not only in various tissues but also in apoptotic cells. In the present study, to elucidate the role of Hsp105alpha during mouse embryogenesis, we established mouse embryonal F9 cell lines that constitutively over-express Hsp105alpha. Over-expression of Hsp105alpha enhanced hydrogen peroxide-induced apoptosis by enhancing the activation of caspase-3, poly(ADP-ribose)polymerase cleavage, cytochrome c release and activation of p38 mitogen-activated protein kinase (p38). Furthermore, oxidative stress-induced apoptosis was suppressed by SB202190, a potent inhibitor of p38, in F9 cells. These findings indicated that the activation of p38 is an essential step for apoptosis in F9 cells and that Hsp105alpha enhances activation of p38, release of cytochrome c and caspase activation. Hsp105alpha may play important roles in organogenesis, during which marked apoptosis occurs, by enhancing apoptosis during mouse embryogenesis.

An immunohistochemical study of APG-2 protein in the rat hippocampus after transient forebrain ischemia

The cellular localization and spatiotemporal expression pattern of APG-2 protein, a member of the heat shock protein 110 family, were investigated in the rat hippocampus after transient forebrain ischemia. The spatiotemporal patterns of immunoreactivity of both APG-2 and glial fibrillary acidic protein were very similar, indicating that reactive astrocytes express APG-2, which was confirmed by double immunofluorescence histochemistry. Colocalization of APG-2 and a neuronal marker NeuN in the neurons of the CA2 and CA3 subfields was also confirmed.

Role of hsp105 in protection against stress-induced apoptosis in neuronal PC12 cells

hsp105alpha is a stress protein characteristically highly expressed in the brain compared with other tissues in mammals. Here, to examine whether hsp105alpha plays a pivotal role in the nervous system, we tested the capability of hsp105alpha to protect against apoptosis in rat neuronal PC12 cells. Various stress treatments such as serum deprivation, heat shock, hydrogen peroxide, etoposide, and actinomycin D induced apoptosis in PC12 cells with characteristic shrinking of nuclei and chromatin. However, PC12 cells that constitutively overexpressed mouse hsp105alpha exhibited a strong protective effect against apoptosis induced by these stress treatments. Cleavage of poly(ADP-ribose) polymerase induced in PC12 cells by these treatments was inhibited in the constitutively overexpressed hsp105alpha cells. Furthermore, c-Jun N-terminal kinase (JNK) was activated in the cells treated with heat shock but not other treatments, and the heat-induced JNK activation was inhibited by the constitutive expression of hsp105alpha.Thus, hsp105alpha prevents not only heat-induced apoptosis by inhibiting JNK activation, but also prevents the apoptosis induced by other stressors through different pathways, and may play important roles in neuronal protection.

Suppression subtraction hybridization and northern analysis reveal upregulation of heat shock, trkB, and sodium calcium exchanger genes following global cerebral ischemia in the rat

Driver (sham-operated) and tester (ischemic) hippocampal cDNAs were subtracted, and the resulting ischemia-induced upregulated gene expression was verified by northern analysis. cDNAs isolated corresponded to (1) genes known to be upregulated following ischemia, (hsc70, hsp90, hsp105 and trkB) and (2) a gene not previously implicated with cerebral ischemia, sodium calcium exchanger (ncx). Furthermore, upregulation of these genes was demonstrated following preconditioning transient global ischemia.

Decrease in level of APG-2, a member of the heat shock protein 110 family, in murine brain following systemic administration of kainic acid

APG-2 belongs to the heat shock protein 110 family. Although kainic acid (KA)-induced seizures are known to elicit expression of inducible heat shock protein 70 (HSP70) in the brain, no investigation has been carried out on the APG-2 level after excitatory amino acid-induced seizures. By means of an immunoblot assay, we determined the levels of HSP70 and APG-2 in discrete brain structures of mice after a single intraperitoneal injection of KA or N-methyl-D-aspartic acid (NMDA). APG-2 level was significantly decreased in frontal cortex, hippocampus, and striatum three days after the administration of KA, while HSP70 level was increased in these regions following the administration. In any of these regions, APG-2 levels were returned to the control levels 10 days after the administration. However, no significant changes were observed in levels of both HSP70 and APG-2 in hypothalamus, midbrain, medulla-pons, and cerebellum of the mice. By contrast, NMDA administration did not significantly affect both levels in any of the regions examined. These findings indicate that the transient decrease in APG-2 expression is one of the intracellular events elicited by signals peculiar to KA, but not by those peculiar to NMDA, in telencephalon of murine brain.

Induction of the HSP110/105 family in the rat hippocampus in cerebral ischemia and ischemic tolerance

Recently, the authors isolated a novel gene of the HSP110 family, ischemia responsive protein 94 kDa (irp94), and demonstrated the expression of this gene after transient forebrain ischemia. In the current study, the authors investigated the expression profiles of all HSP110 family members including hsp110/105 and osp94/apg-1, after transient forebrain ischemia using rat four-vessel occlusion model. Among three members of the HSP110 family, induction of hsp110/105 was the most prominent after ischemia. hsp110/105 mRNA expression was clearly enhanced from 4 to 24 hours after a 6-minute or longer ischemic period. First, hsp110/105 mRNA expression was induced in the dentate gyrus, and later in the pyramidal layer. HSP110/105 protein expression also was enhanced by a 6-minute or longer period of ischemia. Profiles of HSP110/105 expression after ischemia were similar to those of inducible HSP70. After transient forebrain ischemia for 10 minutes, HSP110/105 protein was induced in the dentate gyrus and the CA3 pyramidal layer, but not in the CA1 pyramidal neurons. However, 6 minutes of ischemia induced the HSP110/105 protein, as well as the HSP70 protein, in the CA1 region. CA1 pyramidal neurons expressing HSP110/105 acquired tolerance against subsequent severe ischemia. In conclusion, HSP110/105 showed the most prominent induction after ischemia among the three HSP110 gene family members. Colocalization of HSP110/105 and HSP70 in the CA1 neurons that acquired tolerance suggested that induced HSP110/105 might contribute to ischemic tolerance together with HSP70.

Identification of differentially expressed genes in rat hippocampus after transient global cerebral ischemia using subtractive cDNA cloning based on polymerase chain reaction

BACKGROUND AND PURPOSE

The purpose of this study is to identify new molecules that play important roles in the phenomena that occur in the hippocampus after transient global cerebral ischemia, as clues to better understanding of the mechanisms.

METHODS

A subtractive cDNA library was established by suppression subtractive hybridization of rat hippocampal tissues after transient global cerebral ischemia. With differential screening of the library, upregulated fragments were identified. The mRNA expression levels of selected genes were measured with semiquantitative reverse transcriptase polymerase chain reaction (PCR).

RESULTS

Among more than 100 isolated fragments, approximately half were determined to be identical to known sequences. The rest showed high homology to known sequences, and only 2 did not exhibit homology to any known sequences. The expression of 5 genes identified in this study increased in 24 hours after ischemia to a level twice as high as that in sham-operated controls. These included furin, prosaposin, synaptotagmin IV, heat shock protein 105, and the neutral and basic amino acid transporter (NBAT). The increases in the mRNA expression levels of the genes except NBAT, as revealed by semiquantitative reverse transcription PCR, were statistically significant at both 6 and 24 hours after ischemia.

CONCLUSIONS

Genes isolated are thought to be associated with production of proteins necessary for degeneration, neuroprotection, and reconstruction of neurons. How the expression of these genes relates to functional changes after ischemia remains to be determined. PCR-based subtractive cDNA cloning is demonstrated to be a useful tool for analyzing in vivo gene expression in animal ischemia models.

The hsp110 and Grp1 70 stress proteins: newly recognized relatives of the Hsp70s

Both the Grp170 and Hsp110 families represent relatively conserved and distinct sets of stress proteins, within a more diverse category that also includes the Hsp70s. All of these families are found in a wide variety of organisms from yeasts to humans. Although Hsp110s or Grp170s are not Hsp70s any more than Hsp70s are Hsp110s or Grp170s, it is still reasonable to refer to this combination of related families as the Hsp70 superfamily based on arguments discussed above and since no obvious prokaryotic Hsp110 or Grp170 has yet been identified. These proteins are related to their counterparts in the Hsp70/Grp78 family of eukaryotic stress proteins but are characterized by significantly larger molecular weights. The members of the Grp170 family are characterized by C-terminal ER retention sequences and are ER localized in yeasts and mammals. As a Grp, Grp170 is recognized to be coregulated with other major Grps by a well-known set of stress conditions, sometimes referred to as the unfolded protein response (Kozutsumi et al 1988; Nakaki et al 1989). The Hsp110 family members are localized in the nucleus and cytoplasm and, with other major Hsps, are also coregulated by a specific set of stress conditions, most notably including hyperthermic exposures. Hsp110 is sometimes called Hsp105, although it would be preferable to have a uniform term. The large Hsp70-like proteins are structurally similar to the Hsp70s but differ from them in important ways. In both the Grp170 and Hspl10 families, there is a long loop structure that is interposed between the peptide-binding ,-domain and the alpha-helical lid. In the Hsp110 family and Grp170, there are differing degrees of expansion in the alpha-helical domain and the addition of a C-terminal loop. This gives the appearance of much larger lid domains for Hsp110 and Grp170 compared with Hsp70. Both Hsp110 and Grp170 families have relatively conserved short sequences in the alpha-helical domain in the lid, which are conserved motifs in numerous proteins (we termed these motifs Magic and TedWylee as discussed earlier). The structural differences detailed in this review result in functional differences between the large (Grp170 and Hspl10) members of the Hsp70 superfamily, the most distinctive being an increased ability of these proteins to bind (hold) denatured polypeptides compared with Hsc70, perhaps related to the enlarged C-terminal helical domain. However, there is also a major difference between these large stress proteins; Hsp110 does not bind ATP in vitro, whereas Grp170 binds ATP avidly. The role of the Grp170 and Hsp110 stress proteins in cellular physiology is not well understood. Overexpression of Hsp110 in cultured mammalian cells increases thermal tolerance. Grp170 binds to secreted proteins in the ER and may be cooperatively involved in folding these proteins appropriately. These roles are similar to those of the Hsp70 family members, and, therefore, the question arises as to the differential roles played by the larger members of the superfamily. We have discussed evidence that the large members of the superfamily cooperate with members of the Hsp70 family, and these chaperones probably interact with a large number of chaperones and cochaperones in their functional activities. The fundamental point is that Hsp110 is found in conjunction with Hsp70 in the cytoplasm (and nucleus) and Grp170 is found in conjunction with78 in tha ER in every eucaryotic cell examined from yeast to humans. This would strongly argue that Hsp110 Grp170 exhibit functions in eucaryotes not effectively performed by Hsp70s or Grp78, respectively. Of interest in this respect is the observation that all Hsp110s loss of function or deletion mutants listed in the Drosophila deletion project database are lethal. The important task for the future is to determine the roles these conserved molecular chaperones play in normal and physiologically stressed cells.

The distribution and localization of hsp110 in brain

Hsp110 is one of the few, major heat shock proteins of mammalian cells and was one of the earliest heat shock proteins described. However, it has only recently been cloned and studied at the molecular level. It has been noted that of all tissues examined, brain expresses the highest level of hsp110, with expression levels in unstressed brain being similar to the levels seen in heat shocked cells. The present report describes a combined Northern and Western blot analysis of hsp110 expression in various regions of mouse and human brain. These observations are further expanded by an immunohistochemical characterization of hsp110 cellular localization in mouse brain. It is seen that although hsp110 is an abundant protein in most regions of the brain, its expression is heterogeneous, with little being detectable in the cerebellum. Within the cerebral hemispheres, hsp110 is present in neurons in all regions including the cerebral cortex, the hippocampus, the thalamus and the hypothalamus. In contrast, in the cerebellum, the Purkinje cells are the major hsp110 containing cells while the more abundant granule cells show little if any hsp110 labeling. Since hsp110 has been shown to protect cells and proteins from thermal damage, this differential pattern of expression may have ramifications in the pathophysiology of brain, specifically involving cerebellar sequelae.

Expression of APG-2 protein, a member of the heat shock protein 110 family, in developing rat brain

APG-2 protein is a member of the heat shock protein 110 family, and it is thought to play an important role in the maintenance of neuronal functions under physiological and stress conditions. However, neither the tissue-distribution of APG-2 protein nor developmental change of its expression has been studied at the protein level. Therefore, we generated an antiserum against APG-2 protein and studied expression of this protein in rat brain and other tissues by use of the Western blot method. The results showed a high expression of APG-2 protein in various regions of the central nervous system (cerebral cortex, hippocampus, striatum, midbrain, hypothalamus, cerebellum, medulla pons, and spinal cord) throughout the entire postnatal stage. Similarly, a high level of APG-2 protein was detected in the whole brain of rat embryos and in adult rat tissues such as liver, lung, spleen, and kidney. In contrast, its expression in heart was high at postnatal days 1 and 3, but thereafter drastically decreased to a low level. Furthermore, APG-2 protein was detected in neuronal primary cultures prepared from rat cerebral cortex, and its level did not change notably during neuronal differentiation. These results show that APG-2 protein is constitutively expressed in various tissues and also in neuronal cells throughout the entire embryonic and postnatal period. suggesting that it might play an important role in these tissues under non-stress conditions.

Cloning of human cDNAs for Apg-1 and Apg-2, members of the Hsp110 family, and chromosomal assignment of their genes

In mice, the Hsp110/SSE family is composed of the heat shock protein (Hsp)110/105, Apg-1 and Apg-2. In humans, however, only the Hsp110/105 homolog has been identified as a member, and two cDNAs, Hsp70RY and HS24/p52, potentially encoding proteins structurally similar to, but smaller than, mouse Apg-2 have been reported. To clarify the membership of Hsp110 family in humans, we isolated Apg-1 and Apg-2 cDNAs from a human testis cDNA library. The human Apg-1 was 100% and 91.8% identical in length and amino acid (aa) sequence, respectively, to mouse Apg-1. Human Apg-2 was one aa shorter than and 95.5% identical in sequence to mouse Apg-2. In ECV304, human endothelial cells Apg-1 but not Apg-2 transcripts were induced in 2 h by a temperature shift from 32 degrees C to 39 degrees C. As found in mice, the response was stronger than that to a 37-42 degrees C shift. The human Apg-1 and Apg-2 genes were mapped to the chromosomal loci 4q28 and 5q23.3-q31.1, respectively, by fluorescence in-situ hybridization. We isolated cDNA and genomic clones encompassing the region critical for the difference between Apg-2 and HS24/p52. Although the primer sets used were derived from the sequences common to both cDNAs, all cDNA and genomic clones corresponded to Apg-2. Using a similar approach, the relationship between Apg-2 and Hsp70RY was assessed, and no clone corresponding to Hsp70RY was obtained. These results demonstrated that the Hsp110 family consists of at least three members, Apg-1, Apg-2 and Hsp110 in humans as well as in mice. The significance of HS24/p52 and Hsp70RY cDNAs previously reported remains to be determined.