The Drosophila Dpit47 protein is a nuclear Hsp90 co-chaperone that interacts with DNA polymerase α

Anti-herpes simplex virus activities and mechanisms of marine derived compounds

Herpes simplex virus (HSV) is the most widely prevalent herpes virus worldwide, and the herpetic encephalitis and genital herpes caused by HSV infection have caused serious harm to human health all over the world. Although many anti-HSV drugs such as nucleoside analogues have been ap-proved for clinical use during the past few decades, important issues, such as drug resistance, toxicity, and high cost of drugs, remain unresolved. Recently, the studies on the anti-HSV activities of marine natural products, such as marine polysaccharides, marine peptides and microbial secondary metabolites are attracting more and more attention all over the world. This review discusses the recent progress in research on the anti-HSV activities of these natural compounds obtained from marine organisms, relating to their structural features and the structure-activity relationships. In addition, the recent findings on the different anti-HSV mechanisms and molecular targets of marine compounds and their potential for therapeutic application will also be summarized in detail.

Association of Mutations in Replicative DNA Polymerase Genes with Human Disease: Possible Application of Drosophila Models for Studies

Replicative DNA polymerases, such as DNA polymerase α-primase, δ and ε, are multi-subunit complexes that are responsible for the bulk of nuclear DNA replication during the S phase. Over the last decade, extensive genome-wide association studies and expression profiling studies of the replicative DNA polymerase genes in human patients have revealed a link between the replicative DNA polymerase genes and various human diseases and disorders including cancer, intellectual disability, microcephalic primordial dwarfism and immunodeficiency. These studies suggest the importance of dissecting the mechanisms involved in the functioning of replicative DNA polymerases in understanding and treating a range of human diseases. Previous studies in Drosophila have established this organism as a useful model to understand a variety of human diseases. Here, we review the studies on Drosophila that explored the link between DNA polymerases and human disease. First, we summarize the recent studies linking replicative DNA polymerases to various human diseases and disorders. We then review studies on replicative DNA polymerases in Drosophila. Finally, we suggest the possible use of Drosophila models to study human diseases and disorders associated with replicative DNA polymerases.

Screening of heat stress-regulating active fractions in mung beans

Introduction

Heat stress caused by high temperatures has important adverse effects on the safety and health status of humans and animals, and dietary interventions to alleviate heat stress in daily life are highly feasible.

Methods

In this study, the components of mung bean that have heat stress-regulating effects were characterized by in vitro antioxidant indicators and heat stress cell models.

Results

As a result, 15 target monomeric polyphenol fractions were identified based on untargeted analysis on an ultra performance liquid chromatography coupled with high field quadrupole orbit high resolution mass spectrometry (UHPLC-QE-HF-HRMS) platform and available reports. The results of DPPH and ABTS radical scavenging showed that mung bean polyphenols (crude extract) and 15 monomeric polyphenols had better antioxidant activity, followed by oil and mung bean peptides, while protein and polysaccharides had relatively poor antioxidant activity. Qualitative and quantitative assays for 20 polyphenols (15 polyphenols and 5 isomers) were then established based on platform targets. Vitexin, orientin, and caffeic acid were identified as monomeric polyphenols for heat stress control in mung beans based on their content. Finally, mild (39°C), moderate (41°C), and severe (43°C) heat stress models were successfully constructed based on mouse intestinal epithelial Mode-k cells and human colorectal adenocarcinoma Caco-2 cell lines, all with an optimal heat stress modeling time of 6 h. Screening of mung bean fractions using HSP70 mRNA content, a key indicator of heat stress. As a result, HSP70 mRNA content was significantly up-regulated by different levels of heat stress in both cell models. The addition of mung bean polyphenols (crude extract), vitexin, orientin, and caffeic acid resulted in significant down-regulation of HSP70 mRNA content, and the higher the level of heat stress, the more significant the regulation effect, with orientin having the best effect. Mung bean proteins, peptides, polysaccharides, oils and mung bean soup resulted in increased or no change in HSP70 mRNA levels after most heat stresses.

Discussion

The polyphenols were shown to be the main heat stress regulating components in mung bean. The results of the validation experiments confirm that the above three monomeric polyphenols may be the main heat stress regulating substances in mung bean. The role of polyphenols in the regulation of heat stress is closely linked to their antioxidant properties.

Genomic organization and hypoxia inducible factor responsive regulation of teleost hsp90β gene during hypoxia stress

BACKGROUND

The physiological significance of a large family of heat-shock proteins (HSPs), comprised of the cytosolic HSP90A and the endoplasmic reticulum component of HSPB, is evident in prokaryotes and eukaryotes. The HSP90A is believed to play critical roles in diverse physiological functions of cell viability and chromosomal stability including stress management. Heightened abundance of hsp90β transcript was documented in Channa striatus, a freshwater fish, which is capable of surviving within an extremely hypoxic environment.

METHODS AND RESULTS

To better understand the mechanism of hsp90β gene expression, we investigated its genomic organization. Eleven exons were identified, including a long upstream intron with a remarkable similarity with human, but not with chicken counterpart. Dual-luciferase assays identified promoter activity in a 1366 bp 5'-flanking segment beyond the transcription initiation site. Examination detected a minimal promoter of 754 bp containing a TATA-box, CAAT-enhancer in addition to providing clues regarding other enhancer and repressor elements. The driving capability of this minimal promoter was further validated by its binding ability with TATA-box binding protein and the generation of GFP expressing transgenic zebrafish (F₂). Further, deletion of an inverted HIF (hypoxia inducible factor) motif RCGTG (upstream of the TATA-box) dramatically reduced luciferase expression in a hypoxic environment (CoCl₂ treated cultivable cells) and was identified as a cis-acting HIF responsive element, necessary for the hypoxia-induced expression.

CONCLUSIONS

The results obtained herein provide an insight regarding how hsp90β gene expression is controlled by HIF responsive element in teleost both during hypoxia stress management and normal physiological functions, and suggested that the hsp90β gene promoter could be used as a potential candidate for generating ornamental and food-fish transgenics.

Functional and Stress Response Analysis of Heat Shock Proteins 40 and 90 of Giant River Prawn (Macrobrachium rosenbergii) under Temperature and Pathogenic Bacterial Exposure Stimuli

The aims of this research were to perform molecular characterization and biofunctional analyses of giant river prawn Hsp40 and Hsp90 genes (Mr-hsp40 and Mr-hsp90) under various stress conditions. Comparisons of the nucleotide and amino acid sequences of Mr-hsp40 and Mr-hsp90 with those of other species showed the highest similarity scores with crustaceans. Under normal conditions, expression analysis using quantitative real-time RT-PCR (qRT-PCR) indicated that Mr-hsp40 was highly expressed in the gills and testis, and Mr-hsp90 expression was observed in all tissues, with the highest expression in the ovary. The expression patterns of Mr-hsp40 and Mr-hsp90 transcripts under Aeromonas hydrophila challenge and heat-cold shock conditions were examined in gills, the hepatopancreas and hemocytes, at 0, 3, 6, 12, 24, 48 and 96 h by qRT-PCR. Under bacterial challenge, Mr-hsp40 displayed variable expression patterns in all tissues examined during the tested periods. In contrast, upregulated expression of Mr-hsp90 was quickly observed from 3 to 12 h in the gills and hepatopancreas, whereas obviously significant upregulation of Mr-hsp90 was observed in hemocytes at 12-96 h. Under temperature shock conditions, upregulation of Mr-hsp40 expression was detected in all tested tissues, while Mr-hsp90 expression was quickly upregulated at 3-48 h in all tissues in response to 35 °C conditions, and conditions of 35 and 25 °C stimulated its expression in gills and the hepatopancreas at 12 and 48 h, respectively. Silencing analyses of these two genes were successfully conducted under normal, high-temperature (35 °C) and A. hydrophila infection conditions. Overall, knockdown of Mr-hsp40 and Mr-hsp90 effectively induced more rapid and higher mortality than in the PBS control and GFP induction groups in temperature and infectious treatments. Evidence from this study clearly demonstrated the significant functional roles of Mr-hsp40 and Mr-hsp90, which are crucially involved in cellular stress responses to both temperature and pathogenic bacterial stimuli.

Promoting TTC4 and HSP70 interaction and translocation of annexin A7 to lysosome inhibits apoptosis in vascular endothelial cells

We previously demonstrated that Tetraticopeptide 4 (TTC4) inhibited apoptosis in vascular endothelial cells (VEC) deprived of serum and fibroblast growth factor 2 (FGF-2). In this study, we aimed to resolve the mechanism of TTC4 inhibiting VEC apoptosis. TTC4, predicted as a HSP70 co-chaperone protein, may regulate the fate of cells by affecting the activity of HSP70, however, there is no experimental evidence showing the interaction of TTC4 and HSP70. Using Co-immunoprecipitation (Co-IP), we demonstrated that TTC4 interacted with HSP70. If HSP70 was knockdown, TTC4 no longer suppressed apoptosis. Furthermore, we found ABO, an inhibitor of annexin A7 (ANXA7) GTPase, could promote the interaction of TTC4 and HSP70 and the translocation of ANXA7 to lysosome. At the same time, ABO inhibited the interaction of HSP70 and ANXA7. Moreover, Akt, as a downstream effector of HSP70 was upregulated, and ANXA7 translocating to lysosome protected the stability of lysosomal membrane. Here, we discovered a special mechanism by which TTC4 inhibited apoptosis via HSP70 in VECs. On the one hand, increasing TTC4 and HSP70 interaction upregulated Akt that inhibited apoptosis. On the other hand, decreasing HSP70 and ANXA7 interaction promoted the translocation of ANXA7 to lysosome, which inhibited apoptosis through protecting the lysosomal membrane stability.

Potential role of the heat shock protein 90 (hsp90) in buffering mutations to favour cyclical parthenogenesis in the peach potato aphid Myzus persicae (Aphididae, Hemiptera)

Heat-shock proteins 90 (hsp90s) are a class of molecules able to stabilize a network of 'client' proteins that are involved in several processes. Furthermore, recent studies indicated that mutations in the hsp90-encoding gene induce a wide range of phenotypic abnormalities, which have been interpreted as an increased sensitivity of different developmental pathways to hidden/cryptic mutations. In order to verify the role of hsp90 in aphids, we amplified and sequenced the hsp90 gene in 17 lineages of the peach potato aphid Myzus persicae (Sulzer, 1776) looking for the presence of mutations. In particular, we compared lineages with different reproductive modes (obligate vs. cyclical parthenogenesis), propensity to develop winged females and karyotype stability. Differently from the cyclical parthenogenetic lineages that possessed functional hsp90 genes, the seven analysed asexual lineages showed severe mutations (including frameshift and non-sense mutations). In vivo functional assays with the hsp90-inhibitor geldanamycin showed that some lineages with cyclical parthenogenesis may lose their ability to induce sexuales in the absence of active hsp90 revealing the presence of cryptic mutations in their genomes. As a whole, our data suggest that hsp90 could play in aphids a role in buffering hidden/cryptic mutations that disrupt cyclical parthenogenesis.

Comparative RNA-sequencing analysis of ER-based HSP90 functions and signal pathways in Tribolium castaneum

Tribolium castaneum, the red flour beetle, is a major agriculture pest that damages stored grains and cereal products. Heat-shock protein 90 of T. castaneum (Tchsp90) has been reported to play pivotal roles in heat stress response, development, reproduction, and life span. However, the signaling pathway of Tchsp90 remains unclear. Thus, the global transcriptome profiles between RNA interference (RNAi)-treated insects (ds-Tchsp90) and control insects of T. castaneum were investigated and compared by RNA sequencing. In all, we obtained 14,145,451 sequence reads, which assembled into 13,243 genes. Among these genes, 461 differentially expressed genes (DEGs) were identified between the ds-Tchsp90 and control samples. These DEGs were classified into 44 gene ontology (GO) functional groups, including the cellular process, the response to stimulus, the immune system process, the development process, and reproduction. Interestingly, knocking down the expression of Tchsp90 suppressed both the DNA replication and cell division signaling pathways, which most likely modulated the effects of Tchsp90 on development, reproduction, and life span. Moreover, the DEGs encoding AnnexinB9, frizzled-4, sno, Fem1B, TSL, and CSW might be related to the regulation of the development and reproduction of ds-Tchsp90 insects. The DEGs including TLR6, PGRP2, defensin1, and defensin2 were involved in heat stress and immune response simultaneously, which suggested that cross talk might exist between immunity and stress response. Additionally, RNAi of Tchsp90 altered large-scale serine protease (sp) gene expression patterns and amplified the SP signaling pathway to regulate the development and reproduction as well as the stress response and innate immunity in T. castaneum. All these results shed new light onto the regulatory mechanism of Tchsp90 involved in insect physiology and could further facilitate research into appropriate and sustainable pest control management.

Proteomic Investigation of Metabolic Changes of Mushroom (Flammulina velutipes) Packaged with Nanocomposite Material during Cold Storage

Metabolic changes of mushroom (Flammulina velutipes) applied with polyethylene (PE) material (Normal-PM) or nanocomposite reinforced PE packaging material (Nano-PM) were monitored using tandem mass tags (TMT) labeling combined with two-dimensional liquid chromatography-tandem mass spectrometry (2D LC-MS/MS) technique. A total of 429 proteins were investigated as differentially expressed proteins (DEPs) among treatments after a cold storage period. A total of 232 DEPs were up-regulated and 65 DEPs were down-regulated in Nano-PM packed F. velutipes compared to that of Normal-PM. The up-regulated DEPs were mainly involved in amino acid synthesis and metabolism, signal transduction, and response to stress while the down-regulated DEPs were largely located in mitochondrion and participated in carbohydrate metabolic, amino acid synthesis and metabolism, and organic acid metabolic. It was also revealed that Nano-PM could inhibit the carbohydrate and energy metabolism bioprocess, promote amino acids biosynthesis, enhance antioxidant system, and improve its resistance to stress, resulting in a further extended shelf life of F. velutipes.

Heat shock protein 90β in the Vero cell membrane binds Japanese encephalitis virus

The pathogenesis of Japanese encephalitis virus (JEV) is complex and unclearly defined, and in particular, the effects of the JEV receptor (JEVR) on diverse susceptible cells are elusive. In contrast to previous studies investigating JEVR in rodent or mosquito cells, in this study, we used primate Vero cells instead. We noted that few novel proteins co‑immunoprecipitated with JEV, and discovered that one of these was heat shock protein 90β (HSP90β), which was probed by mass spectrometry with the highest score of 60.3 after questing the monkey and human protein databases. The specific HSP90β‑JEV binding was confirmed by western blot analysis under non‑reducing conditions, and this was significantly inhibited by an anti‑human HSP90β monoclonal antibody in a dose‑dependent manner, as shown by immunofluorescence assay and flow cytometry. In addition, the results of confocal laser scanning microscopic examination demonstrated that the HSP90β‑JEV binding occurred on the Vero cell surface. Finally, JEV progeny yields determined by plaque assay were also markedly decreased in siRNA‑treated Vero cells, particularly at 24 and 36 h post‑infection. Thus, our data indicate that HSP90β is a binding receptor for JEV in Vero cells.

Stromal COX-2 signaling are correlated with colorectal cancer: A review

Cyclooxygenase-2 (COX-2) and its product prostaglandin E₂ (PGE₂) play a critical role in development and progression of colorectal cancer. Yet the detailed mechanistic pathways of COX-2 mediated signaling are still controversial and the role of COX-2 interaction in epithelial-stromal compartments on colorectal carcinogenesis is not well-understood either. In this review, we provide experimental evidence to support that (1) COX-2 signaling plays a major role in development and progression of colorectal cancer; (2) Stromal fibroblasts are a major source of COX-2 and PGE₂; (3) Stromal-epithelial interaction mediated by COX-2 signaling promotes colorectal carcinogenesis and (4) Inhibition of stromal COX-2 signaling is necessary to control colorectal cancer. In conclusion, the evidences summarized in the review reflect recent advances and insight in mechanistic studies of colorectal cancer which can help the audiences to further understand the etiology and the control of this disease.

The Hsp90 cochaperones Cpr6, Cpr7, and Cns1 interact with the intact ribosome

The abundant molecular chaperone Hsp90 is essential for the folding and stabilization of hundreds of distinct client proteins. Hsp90 is assisted by multiple cochaperones that modulate Hsp90's ATPase activity and/or promote client interaction, but the in vivo functions of many of these cochaperones are largely unknown. We found that Cpr6, Cpr7, and Cns1 interact with the intact ribosome and that Saccharomyces cerevisiae lacking CPR7 or containing mutations in CNS1 exhibited sensitivity to the translation inhibitor hygromycin. Cpr6 contains a peptidyl-prolyl isomerase (PPIase) domain and a tetratricopeptide repeat (TPR) domain flanked by charged regions. Truncation or alteration of basic residues near the carboxy terminus of Cpr6 disrupted ribosome interaction. Cns1 contains an amino-terminal TPR domain and a poorly characterized carboxy-terminal domain. The isolated carboxy-terminal domain was able to interact with the ribosome. Although loss of CPR6 does not cause noticeable growth defects, overexpression of CPR6 results in enhanced growth defects in cells expressing the temperature-sensitive cns1-G90D mutation (the G-to-D change at position 90 encoded by cns1). Cpr6 mutants that exhibit reduced ribosome interaction failed to cause growth defects, indicating that ribosome interaction is required for in vivo functions of Cpr6. Together, these results represent a novel link between the Hsp90 molecular-chaperone machine and protein synthesis.

Heat shock proteins in relation to heat stress tolerance of creeping bentgrass at different N levels

Heat stress is a primary factor causing summer bentgrass decline. Changes in gene expression at the transcriptional and/or translational level are thought to be a fundamental mechanism in plant response to environmental stresses. Heat stress redirects protein synthesis in higher plants and results in stress protein synthesis, particularly heat shock proteins (HSPs). The goal of this work was to analyze the expression pattern of major HSPs in creeping bentgrass (Agrostis stolonifera L.) during different heat stress periods and to study the influence of nitrogen (N) on the HSP expression patterns. A growth chamber study on 'Penn-A4' creeping bentgrass subjected to 38/28°C day/night for 50 days, was conducted with four nitrate rates (no N-0, low N-2.5, medium N-7.5, and high N-12.5 kg N ha-1) applied biweekly. Visual turfgrass quality (TQ), normalized difference vegetation index (NDVI), photochemical efficiency of photosystem II (Fv/Fm), shoot electrolyte leakage (ShEL), and root viability (RV) were monitored, along with the expression pattern of HSPs. There was no difference in measured parameters between treatments until week seven, except TQ at week five. At week seven, grass at medium N had better TQ, NDVI, and Fv/Fm accompanied by lower ShEL and higher RV, suggesting a major role in improved heat tolerance. All the investigated HSPs (HSP101, HSP90, HSP70, and sHSPs) were up-regulated by heat stress. Their expression patterns indicated cooperation between different HSPs and their roles in bentgrass thermotolerance. In addition, their production seems to be resource dependent. This study could further improve our understanding about how different N levels affect bentgrass thermotolerance.

Heat-shock protein 90 promotes nuclear transport of herpes simplex virus 1 capsid protein by interacting with acetylated tubulin

Although it is known that inhibitors of heat shock protein 90 (Hsp90) can inhibit herpes simplex virus type 1 (HSV-1) infection, the role of Hsp90 in HSV-1 entry and the antiviral mechanisms of Hsp90 inhibitors remain unclear. In this study, we found that Hsp90 inhibitors have potent antiviral activity against standard or drug-resistant HSV-1 strains and viral gene and protein synthesis are inhibited in an early phase. More detailed studies demonstrated that Hsp90 is upregulated by virus entry and it interacts with virus. Hsp90 knockdown by siRNA or treatment with Hsp90 inhibitors significantly inhibited the nuclear transport of viral capsid protein (ICP5) at the early stage of HSV-1 infection. In contrast, overexpression of Hsp90 restored the nuclear transport that was prevented by the Hsp90 inhibitors, suggesting that Hsp90 is required for nuclear transport of viral capsid protein. Furthermore, HSV-1 infection enhanced acetylation of α-tubulin and Hsp90 interacted with the acetylated α-tubulin, which is suppressed by Hsp90 inhibition. These results demonstrate that Hsp90, by interacting with acetylated α-tubulin, plays a crucial role in viral capsid protein nuclear transport and may provide novel insight into the role of Hsp90 in HSV-1 infection and offer a promising strategy to overcome drug-resistance.

DNA polymerase α interacts with PrSet7 and mediates H4K20 monomethylation in Drosophila

In human cells, appropriate monomethylation of histone H4 lysine 20 by PrSet7 (also known as SET8 and SETD7) is important for the correct transcription of specific genes and timely progression through the cell cycle. Over-methylation appears to be prevented through the interaction of PrSet7 with proliferating cell nuclear antigen (PCNA), which targets PrSet7 for destruction through the pathway mediated by CRL4(C) (dt2) (the cullin ring finger ligase-4 complex containing Cdt2). However, the factors involved in positive regulation of PrSet7 histone methylation remain undefined. Here, we present biochemical and genetic evidence for a previously undocumented interaction between Drosophila PrSet7 (dPrSet7) and DNA polymerase α in Drosophila. Depletion of the polymerase reduces H4K20 monomethylation suggesting that it is required for dPrSet7 histone methylation activity. We also show that the interaction between PCNA and PrSet7 is conserved in Drosophila, but is only detectable in chromatin fractions. Consistent with this, S2 cells show a significant loss of chromatin-bound dPrSet7 protein as S phase progresses. Based on these data we suggest that interaction with the DNA polymerase represents an important route for stimulation of PrSet7 histone methylase activity that is mediated by allowing loading of dPrSet7 onto chromatin or its subsequent activation.

VER-155008, a small molecule inhibitor of HSP70 with potent anti-cancer activity on lung cancer cell lines

Lung cancer is the most common malignancy and exhibits significant morbidity and mortality worldwide. Among all lung cancer subtypes, non-small-cell lung cancer (NSCLC) accounts for the majority of all lung cancer cases. Although there have been intensive investigations on the underlying mechanism of NSCLC development and progression, the exact molecular basis is not well understood. Further insights on important molecular regulators of lung cancer are needed for development of novel therapeutics. The heat shock protein (HSP) family is a group of molecular chaperones that assist in protein folding, modification, and transportation. Different HSPs are essential for tumor cell survival by binding diverse client proteins and regulating homeostasis. In the current study, we sought to characterize HSP70 and HSP90 as potent regulators of NSCLC growth. Our results indicate that differential expression of HSP70 is associated with the malignant phenotype of NSCLC cell lines and plays an important regulatory role in NSCLC cell proliferation. Moreover, a specific inhibitor of HSP70, VER-155008 significantly inhibits NSCLC proliferation and cell cycle progression. We showed that this effect is largely abolished by HSP70 overexpression, indicating that the inhibitory effect of VER-155008 on cell growth is specifically through HSP70 inhibition. In addition, 17-AAD, an inhibitor of HSP90, exerts a potent synergistic effect on NSCLC proliferation with VER-155008. We also observed that inhibition of HSP70 by VER-155008 can sensitize A549 cells to ionizing radiation. These data provide proof-of-principle that VER-155008 can be a good candidate for NSCLC treatment and HSP machinery is a good target for developing NSCLC therapeutics.

A heat shock protein 90 inhibitor that modulates the immunophilins and regulates hormone receptors without inducing the heat shock response

When a cell encounters external stressors, such as lack of nutrients, elevated temperatures, changes in pH or other stressful environments, a key set of evolutionarily conserved proteins, the heat shock proteins (hsps), become overexpressed. Hsps are classified into six major families with the hsp90 family being the best understood; an increase in cell stress leads to increased levels of hsp90, which leads to cellular protection. A hallmark of hsp90 inhibitors is that they induce a cell rescue mechanism, the heat shock response. We define the unique molecular profile of a compound (SM145) that regulates hormone receptor protein levels through hsp90 inhibition without inducing the heat shock response. Modulation of the binding event between heat shock protein 90 and the immunophilins/homologs using SM145, leads to a decrease in hormone receptor protein levels. Unlike N-terminal hsp90 inhibitors, this hsp90 inhibitor does not induce a heat shock response. This work is proof of principle that controlling hormone receptor expression can occur by inhibiting hsp90 without inducing pro-survival protein heat shock protein 70 (hsp70) or other proteins associated with the heat shock response. Innovatively, we show that blocking the heat shock response, in addition to hsp90, is key to regulating hsp90-associated pathways.

Targeting heat-shock-protein 90 (Hsp90) by natural products: geldanamycin, a show case in cancer therapy

Covering 2005 to 2013. In this review recent progress in the development of heat shock proteins (Hsp90) in oncogenesis is illuminated. Particular emphasis is put on inhibitors such as geldanamycin and analogues that serve as a natural product show case. Hsp90 has emerged as an important target in cancer therapy and/or against pathogenic cells which elicit abnormal Hsp patterns. Competition for ATP by geldanamycin and related compounds abrogate the chaperone function of Hsp90. In this context, this account pursues three topics in detail: a) Hsp90 and its biochemistry, b) Hsp90 and its role in oncogenesis and c) strategies to create compound libraries of structurally complex inhibitors like geldanamycin on which SAR studies and the development of drugs that are currently in different stages of clinical testing rely.

Heat shock protein 90B1 plays an oncogenic role and is a target of microRNA-223 in human osteosarcoma

BACKGROUND/AIMS

Over the past decade, heat shock protein 90 (Hsp90) has emerged as a potential therapeutic target for cancer. However, the molecular mechanisms of down-regulation Hsp90 expression in osteosarcoma are incompletely understood. To develop potential therapy targeting Heat shock protein 90B1 (Hsp90B1), we studied the roles of miR- 223 in the proliferation and apoptosis of human osteosarcoma.

METHODS

pcDNA3.1(+)- miR-223 plasmid vectors were constructed and transfected into MG63 cells. Co-transfection of miR-223 expression vector with pMIR-Hsp90B1 (The recombined vector of pMIR-GLOTM luciferase vector containing Hsp90B1-3'UTR) led to the reduced activity of luciferase in a dual-luciferase reporter gene assay, suggesting that Hsp90B1 is a target gene of miR-223. Expression of HSP90B1 was detected by RT-PCR and western blotting analysis. Cell proliferation was determined using the MTT assay. Cell-cycle distribution and apoptosis were examined by flow cytometry. PI3K, p-Akt, Akt, mTOR, Bcl-2 and Bid were also detected by western blotting analysis. After a mouse xenograft model of human MG63 tumors was constructed, tumor growth, microvessel density and proliferation in each group was determined.

RESULTS

The pcDNA3.1(+)-miR-223 vector efficiently suppressed the expression of HSP90B1, while silencing miR-223 increased expression of Hsp90B1. Furthermore, overexpression of miR-223 results in significant inhibition of cell growth on culture plates. Moreover, cancer cells showed significant G0/G1 arrest and increased apoptosis due to gene silencing. Protein levels of PI3k, p-Akt, mTOR, and Bcl-2 were decreased, whereas Bid levels were increased. Microvessel density as assessed by CD34 levels and cell growth by PCNA levels decreased according to immunohistochemical analysis.

CONCLUSION

Hsp90B1 is a direct target of miR-223 and miR- 223 may have a tumor suppressor function in osteosarcoma through the PI3K/Akt/mTOR pathway and could be used in anticancer therapies in osteosarcoma.

Differential transcription of heat shock protein 90 (HSP90) in the dinoflagellate Prorocentrum minimum by copper and endocrine-disrupting chemicals

The dinoflagellate algae survive variations in water temperature as well as sudden exposures to toxic substances; heat shock proteins (HSPs) seem to function as part of their cell survival strategy. In the present study, we determined the complete open reading frame (ORF) of HSP90 gene in the dinoflagellate Prorocentrum minimum (PmHSP90), and examined the expression levels of the gene after exposure to thermal stressors, copper metal, and endocrine-disrupting chemicals, including bisphenol A (BPA) and polychlorinated biphenyl (PCB). The complete ORF of PmHSP90 was 2,130-bp long, encoding a 709-amino acid-long polypeptide (81.62 kDa), and bearing characteristics of the HSP90 family and conserved domains. Real-time (RT)-PCR analyses revealed different expression patterns after exposure to heat, metals, and chemicals. The expression of PmHSP90 was significantly upregulated by increased thermal stresses, with the highest changes of 2.4-fold and 1.9-fold occurring after 24 h at 25 °C and 30 °C, respectively. The gene expression dramatically increased (2.1 to 8.9-fold changes) with increasing concentrations of copper (one-way ANOVA, P < 0.01). Treatment with BPA or PCB, however, did not induce significant changes in PmHSP90 expression. These data suggest that the dinoflagellate HSP90 responds to thermal stressors, but may differentially respond to toxic substances such as metals and endocrine-disrupting chemicals.

Hsp90 regulates O-linked β-N-acetylglucosamine transferase: a novel mechanism of modulation of protein O-linked β-N-acetylglucosamine modification in endothelial cells

O-linked β-N-acetylglucosamine (O-GlcNAc) modification of proteins is involved in many important cellular processes. Increased O-GlcNAc has been implicated in major diseases, such as diabetes and its complications and cardiovascular and neurodegenerative diseases. Recently, we reported that O-GlcNAc modification occurs in the proteasome and serves to inhibit proteasome function by blocking the ATPase activity in the 19S regulatory cap, explaining, at least in part, the adverse effects of O-GlcNAc modification and suggesting that downregulating O-GlcNAc might be important in the treatment of human diseases. In this study, we report on a novel mechanism to modulate cellular O-GlcNAc modification, namely through heat shock protein 90 (Hsp90) inhibition. We observed that O-linked β-N-acetylglucosamine transferase (OGT) interacts with the tetratricopeptide repeat binding site of Hsp90. Inhibition of Hsp90 by its specific inhibitors, radicicol or 17-N-allylamino-17-demethoxygeldanamycin, destabilized OGT in primary endothelial cell cultures and enhanced its degradation by the proteasome. Furthermore, Hsp90 inhibition downregulated O-GlcNAc protein modifications and attenuated the high glucose-induced increase in O-GlcNAc protein modification, including high glucose-induced increase in endothelial or type 3 isoform of nitric oxide synthase (eNOS) O-GlcNAcylation. These results suggest that Hsp90 is involved in the regulation of OGT and O-GlcNAc modification and that Hsp90 inhibitors might be used to modulate O-GlcNAc modification and reverse its adverse effects in human diseases.

Broad action of Hsp90 as a host chaperone required for viral replication

Viruses are intracellular pathogens responsible for a vast number of human diseases. Due to their small genome size, viruses rely primarily on the biosynthetic apparatus of the host for their replication. Recent work has shown that the molecular chaperone Hsp90 is nearly universally required for viral protein homeostasis. As observed for many endogenous cellular proteins, numerous different viral proteins have been shown to require Hsp90 for their folding, assembly, and maturation. Importantly, the unique characteristics of viral replication cause viruses to be hypersensitive to Hsp90 inhibition, thus providing a novel therapeutic avenue for the development of broad-spectrum antiviral drugs. The major developments in this emerging field are hereby discussed. This article is part of a Special Issue entitled: Heat Shock Protein 90 (HSP90).

Combining emerging agents in advanced breast cancer

Newer treatments have improved survival for patients with metastatic breast cancer over the last two decades, and a battery of new cytotoxic and targeted therapies is continuing to enhance this trend. This review outlines recent data and ongoing research in this area, by highlighting new developments (regarding approved but relatively new classes of cytotoxic and targeted agents) and also new classes of targeted therapy that are undergoing clinical evaluation. Mechanisms for synergy between agents are discussed where data are available, as is information on the rationale behind the development of agents that inhibit angiogenesis, DNA repair, histone deacetylases, heat shock proteins, or various signaling pathways in tumor proliferation. The abundance of clinical research surrounding anticancer agents, together with ongoing cancer biology research, is expected to further increase the available pool of therapeutic options for metastatic breast cancer. Concomitantly, in the absence of an effective targeted monotherapy, a better understanding of the interplay between biologic and cytotoxic anticancer agents will improve our ability to rationally design combination regimens with better efficacy and tolerability.

Heat shock protein 70 expression following hepatic radiofrequency ablation is affected by adjacent vasculature

BACKGROUND

Heat shock proteins are a highly conserved family of stress response proteins. Members of the heat shock protein 70 (Hsp70) family prevent protein misfolding and aggregation. Following radiofrequency ablation of unresectable liver tumors an interface appears between the irreversibly damaged and normal liver. The fate of this transition zone is critical and is believed to be responsible for local recurrences. Hsp70 is expressed in response to thermal stress and may influence the fate of cells in this transitional zone. It is also recognized that the presence of large vessels or a perivascular location of tumors also influences the recurrence rate. The aim of this study is to examine the transition zone and observe the effect of local blood flow on ablation morphology and Hsp70 expression.

METHODS

Radiofrequency ablation was performed in 25 rats at various distances from the liver hilum. Tissue was retrieved and analysed at time points 0, 4, 24, 48 h, and 2 wk following treatment. Tissue was analyzed histologically with hematoxylin and eosin staining (H and E,) and immunohistochemically for Hsp70 expression.

RESULTS

All rats survived the procedure. H and E staining revealed previously unreported foci of apoptosis at the ablation edge and deep in the normal hepatic parenchyma. Hsp70 was expressed in the transition zone at 4 h and peaked at 24 h. The degree of Hsp70 expression was significantly influenced by the distance from surrounding vasculature.

CONCLUSIONS

This study reports several previously unreported findings. There is increased apoptosis distal to the ablated zone suggests leakage of radiofrequency (RF) current down blood vessels originating in the ablation zone. The degree of Hsp70 expression in the transition zone correlates with time after treatment and the size and location of any adjacent vasculature. These findings suggest that heat shock proteins may play a role in the ability of damaged cells to recover and survive at the periphery of an ablation zone.

Pharmacophore-based virtual screening and docking studies on Hsp90 inhibitors

Hsp90 (Heat shock protein 90) is an important therapeutic target for the treatment of cancer. To identify important chemical features for Hsp90 inhibitory activity, a 3D-QSAR pharmacophore model was developed using a set of 61 inhibitors (a training set of 31 and a test set of 30 compounds) belonging to a series of 2-amino-6-halopurine and 7'-substituted benzothiazolothio- and pyridinothiazolothio-purines. The best HypoGen model consisted of five pharmacophoric features: one hydrogen bond acceptor (HBA), one hydrogen bond donor (HBD) and three hydrophobic (HY) groups. It showed a high correlation coefficient (r = 0.943) and low root mean square deviation (RMSD = 0.751). This model was validated against 30 known Hsp90 inhibitors, where it showed a high predictive value for R(2)pred = 0.805], thus confirming that HY, HBA and HBD features are essential for Hsp90 inhibition. The validated pharmacophore model (Hypo-1) was used as a 3D query for virtual screening to retrieve potential inhibitors from the Maybridge and National Cancer Institute (NCI) databases. The hit compounds were subsequently subjected to molecular docking studies and, finally, five hits were prioritized as potential leads based on GoldScore function.

Symbiosis as a source of selectable epigenetic variation: taking the heat for the big guy

Evolutionary developmental biology is based on the principle that evolution arises from hereditable changes in development. Most of this new work has centred on changes in the regulatory components of the genome. However, recent studies (many of them documented in this volume) have shown that development also includes interactions between the organism and its environment. One area of interest concerns the importance of symbionts for the production of the normal range of phenotypes. Many, if not most, organisms have 'outsourced' some of their developmental signals to a set of symbionts that are expected to be acquired during development. Such intimate interactions between species are referred to as codevelopment, the production of a new individual through the coordinated interactions of several genotypically different species. Within the past 2 years, several research programmes have demonstrated that such codevelopmental schemes can be selected. We will focus on symbioses in coral reef cnidarians symbiosis, pea aphids and cactuses, wherein the symbiotic system provides thermotolerance for the composite organism.

Goat endometrial heat shock protein-90 (Hsp-90): development of an expedient method for its purification and observations on its intracellular movement

An expedient method has been developed by which goat uterine Hsp-90 could be isolated and purified to homogeneity in less than 1day. The yield is roughly 1mg from 60g tissue. This method takes into advantage three of our earlier observation that (a) Hsp-90 gets linked to the non-activated estrogen receptor (naER) in the presence of 10mM sodium molybdate; (b) naER, but not Hsp-90 binds to phosphocellulose and (c) exposure to estradiol facilitates dissociation of Hsp-90 from naER through estradiol binding to naER and the possible change in naER conformation. Intracellular movement of Hsp-90 and naER was monitored in goat endometrial cells in culture following exposure of the cells to estradiol. Confocal microscopic analysis revealed a clear presence of both proteins within the nucleus within 3h after exposure to estradiol. Whether Hsp-90 has its own nuclear-transport machinery is debatable. Being an actin-binding protein, there is a distinct possibility that the nuclear entry of Hsp-90 is actin dependent. The functional significance of the nuclear entry of Hsp-90, along with naER, remains to be determined; it may, however, be speculated that the Hsp-90 might be directly involved in the naER to nER II transformation by functioning as a molecular chaperone and helping the protein in re-orienting its structural organization.

Nuclear transport of protein TTC4 depends on the cell cycle

TTC4 (tetratricopeptide repeat domain protein 4) is a putative tumor suppressor involved in the transformation of melanocytes. At present, the relationships between TTC4 and DNA replication proteins are largely unknown, as are the tissue distribution and subcellular localization of TTC4. Using reverse transcription with the polymerase chain reaction, we have observed that the murine TTC4 gene is ubiquitously expressed. Analysis of the TTC4 subcellular localization has shown that, upon overexpression, TTC4 localizes to the cytoplasm. Interestingly, co-expression with a known protein interaction partner, hampin/MSL1, results in the nuclear translocation of the TTC4 protein. The subcellular localization of endogenous TTC4 depends, however, on the cell cycle: it is mostly nuclear in the G1 and S phases and is evenly distributed between the nucleus and cytoplasm in G2. The nuclear transport of TTC4 is apparently a complex process dependent on interactions with other proteins during the progression of the cell cycle. Thus, the dynamic character of the nuclear accumulation of TTC4 might be a potential link with regard to its function in tumor suppression.

Plasticity of the Hsp90 chaperone machine in divergent eukaryotic organisms

Hsp90 is critical for the regulation and activation of numerous client proteins critical for diverse functions such as cell growth, differentiation, and reproduction. Cytosolic Hsp90 function is dependent on a battery of co-chaperone proteins that regulate the ATPase activity of Hsp90 function or direct Hsp90 to interact with specific client proteins. Little is known about how Hsp90 complexes vary between different organisms and how this affects the scope of clients that are activated by Hsp90. This study determined whether ten distinct Hsp90 co-chaperones were encoded by genes in 19 disparate eukaryotic organisms. Surprisingly, none of the co-chaperones were present in all organisms. The co-chaperone Hop/Sti1 was most widely dispersed (18 out of 19 species), while orthologs of Cdc37, which is critical for the stability and activation of diverse protein kinases in yeast and mammals, were identified in only nine out of 19 species examined. The organism with the smallest proteome, Encephalitozoon cuniculi, contained only three of these co-chaperones, suggesting a correlation between client diversity and the complexity of the Hsp90 co-chaperone machine. Our results suggest co-chaperones are critical for cytosolic Hsp90 function in vivo, but that the composition of Hsp90 complexes varies depending on the specialized protein folding requirements of divergent species.

The human TPR protein TTC4 is a putative Hsp90 co-chaperone which interacts with CDC6 and shows alterations in transformed cells

Background

The human TTC4 protein is a TPR (tetratricopeptide repeat) motif-containing protein. The gene was originally identified as being localized in a genomic region linked to breast cancer and subsequent studies on melanoma cell lines revealed point mutations in the TTC4 protein that may be associated with the progression of malignant melanoma.

Methodology/Principle Findings

Here we show that TTC4 is a nucleoplasmic protein which interacts with HSP90 and HSP70, and also with the replication protein CDC6. It has significant structural and functional similarities with a previously characterised Drosophila protein Dpit47. We show that TTC4 protein levels are raised in malignant melanoma cell lines compared to melanocytes. We also see increased TTC4 expression in a variety of tumour lines derived from other tissues. In addition we show that TTC4 proteins bearing some of the mutations previously identified from patient samples lose their interaction with the CDC6 protein.

Conclusions/Significance

Based on these results and our previous work with the Drosophila Dpit47 protein we suggest that TTC4 is an HSP90 co-chaperone protein which forms a link between HSP90 chaperone activity and DNA replication. We further suggest that the loss of the interaction with CDC6 or with additional client proteins could provide one route through which TTC4 could influence malignant development of cells.

Characterization of hampin/MSL1 as a node in the nuclear interactome

Hampin, homolog of Drosophila MSL1, is a partner of histone acetyltransferase MYST1/MOF. Functions of these proteins remain poorly understood beyond their participation in chromatin remodeling complex MSL. In order to identify new proteins interacting with hampin, we screened a mouse cDNA library in yeast two-hybrid system with mouse hampin as bait and found five high-confidence interactors: MYST1, TPR proteins TTC4 and KIAA0103, NOP17 (homolog of a yeast nucleolar protein), and transcription factor GC BP. Subsequently, all these proteins were used as baits in library screenings and more new interactions were found: tumor suppressor RASSF1C and spliceosome component PRP3 for KIAA0103, ring finger RNF10 for RASSF1C, and RNA polymerase II regulator NELF-C for MYST1. The majority of the observed interactions was confirmed in vitro by pull-down of bacterially expressed proteins. Reconstruction of a fragment of mammalian interactome suggests that hampin may be linked to diverse regulatory processes in the nucleus.

The Drosophila Cdc6/18 protein has functions in both early and late S phase in S2 cells

The Cdc6/18 protein has been mainly characterised for its role in the initiation of DNA replication. Several studies exist, however, which suggest that it may also have a role in controlling the G2/M transition. Here we present studies on the Drosophila Cdc6 (DmCdc6) protein that support this dual function for the protein. First we show that its location is consistent with a cellular role post replication initiation as it remains nuclear throughout G1, S and G2 phases. In addition, we have been able to reduce the level of DmCdc6 protein to nondetectable levels in S2 cells using RNAi. This causes DNA fragmentation and cell cycle abnormalities which have some similarities with phenotypes previously observed in yeasts and are consistent with the cells entering mitosis with incompletely replicated DNA. Finally, we have stably overexpressed the DmCdc6 protein to a high level in S2 cells. Despite a large excess of protein the effects on the S2 cells were minimal. We did, however, detect a slight stalling of the cells in the late S phase of the cell cycle, which further supports the proposal that DmCdc6 has a role in controlling the transition from the S to M phases of the cycle.

Molecular cloning and characterization of two different cDNAs encoding the molecular chaperone Hsp90 in the Oomycete Achlya ambisexualis

The chaperone Hsp90 plays a key role in the maturation and activation of many 'client' proteins in eukaryotic cells. In the oomycete Achlya ambisexualis two populations of hsp90 transcripts that differ slightly in size (2.8 and 2.9 kb) are present in heat-shocked mycelia. Only the 2.8 kb transcripts are seen in vegetative mycelia and in mycelia undergoing antheridiol-induced differentiation. Two different hsp90 cDNAs were isolated and characterized. Although nearly identical, an additional eight nucleotide sequence was present at the end of the 3'UTR of one of the two cDNAs. RT-PCR analyses indicated that hsp90 transcripts containing the eight nucleotide extension, were present only in heat-shocked mycelia. Hsp90 transcripts lacking this sequence were present in vegetative mycelia and the levels of these transcripts increased in both heat-shocked and hormone-treated mycelia. Each hsp90 cDNA encoded a nearly identical Hsp90 protein. However, two Hsp90 proteins (86 and 84 kDa) were observed on immunoblots of mycelial proteins. Only one of these, i.e., the 86 kDa protein was detected by an anti-phosphoserine antibody, suggesting that the difference in mass of the two Hsp90 isoforms, was due at least in part, to different levels of phosphoserine residues.

Hsp70 and Hsp90--a relay team for protein folding

Molecular chaperones are a functionally defined set of proteins which assist the structure formation of proteins in vivo. Without certain protective mechanisms, such as binding nascent polypeptide chains by molecular chaperones, cellular protein concentrations would lead to misfolding and aggregation. In the mammalian system, the molecular chaperones Hsp70 and Hsp90 are involved in the folding and maturation of key regulatory proteins, like steroid hormone receptors, transcription factors, and kinases, some of which are involved in cancer progression. Hsp70 and Hsp90 form a multichaperone complex, in which both are connected by a third protein called Hop. The connection of and the interplay between the two chaperone machineries is of crucial importance for cell viability. This review provides a detailed view of the Hsp70 and Hsp90 machineries, their cofactors and their mode of regulation. It summarizes the current knowledge in the field, including the ATP-dependent regulation of the Hsp70/Hsp90 multichaperone cycle and elucidates the complex interplay and their synergistic interaction.

The UCS family of myosin chaperones

The canonical UCS (UNC-45/Cro1/She4p) protein, Caenorhabditis elegans UNC-45, was one of the earliest molecules to be shown genetically to be necessary for sarcomere assembly. Genetic analyses of homologues in several fungal species indicate that the conserved UCS domain functionally interacts with conventional type II and unconventional type V myosins. In C. elegans and other invertebrate species, UNC-45 and its orthologues interact with both sarcomeric and non-sarcomeric myosins whereas, in vertebrates, there are two UNC-45 isoforms: a general cell (GC) and a striated muscle (SM) isoform. Although the mechanism of action of UCS proteins is unknown, recent biochemical studies suggest that they may act as molecular chaperones that facilitate the folding and/or maturation of myosin.