Identification of GRP 78 (BiP) as a liver cell expressed receptor element for dengue virus serotype 2

Summary. This study sought to identify receptor elements for dengue virus serotype 2 on human liver cells (HepG2) using the viral overlay protein binding assay (VOPBA) technique and Mass Spectrometry fingerprinting. A single major and several minor virus binding bands were observed, and mass spectrometry identified a candidate binding protein for the major binding band as GRP 78 (BiP). GRP78 expression on the cell surface was confirmed, and antibodies directed against both the N and C-terminus of GRP 78 (BiP) altered both the binding of the virus to the cell surface as well as the infectivity profile of HepG2 cells in response to dengue serotype 2 infection. GRP 78 (BiP), which has previously been identified as a co-receptor protein for coxsackievirus A9, is the first non-Fc receptor protein identified for the dengue virus, although GRP78 probably functions as part of a receptor complex.     

Characterization of putative Japanese encephalitis virus receptor molecules on microglial cells

Japanese encephalitis virus (JEV) a mosquito-borne flavivirus is a major cause of viral encephalitis in Asia. While the principle target cells for JEV in the central nervous system are believed to be neurons, microglia are activated in response to JEV and have been proposed to act as a long lasting virus reservoir. Viral attachment to a host cell is the first step of the viral entry process and is a critical mediator of tissue tropism. This study sought to identify molecules associated with JEV entry to microglial cells. Virus overlay protein-binding assay (VOPBA) and liquid chromatography-mass spectrometry (LC/MS/MS) identified the 37/67 kDa high-affinity laminin receptor protein and nucleolin as a potential JEV-binding proteins. These proteins were subsequently investigated for a contribution to JEV entry to mouse microglial BV-2 cells together with other possible candidate receptor molecules including Hsp70, Hsp90, GRP78, CD14, and CD4. In antibody mediated inhibition of infection experiments, both anti-laminin receptor and anti-CD4 antibodies significantly reduced virus entry while anti-Hsp70 and 90 antibodies produced a slight reduction. Significant inhibition of virus entry (up to 80%) was observed in the presence of lipopolysaccharide (LPS) which resulted in a complete down-regulation of CD4 and moderate down-regulation of CD14. These results suggest that multiple receptor proteins may mediate the entry of JEV to microglial cells, with CD4 playing a major role.     

Antibodies against the human heat shock protein hsp70 in patients with severe coronary artery disease

Heat shock proteins (hsps) play complex role in the function of the immune system, they can activate both humoral and cellular immune response, as well the complement system. Although autoimmunity to hsp70 was implicated in certain autoimmune diseases and other conditions, the exact role of anti-hsp70 antibodies is not known. It was demonstrated by our previous work and other's findings that antibodies against the 60 kDa hsps are strongly associated with coronary atherosclerosis and carotis disease. It is also known that there is increased hsp70 expression at different sites of atherosclerosis. Therefore our aim was to study whether level of anti-hsp70 antibodies correlate with the presence of severe coronary artery disease (CAD). We measured and compared anti-hsp70 IgG antibody levels in CAD patients (n = 99) and healthy subjects (n = 99) with ELISA. The frequency of these antibodies was high in both groups and there was no significant difference in the median level of anti-hsp70 antibodies between patients with severe CAD and controls (653 (400-1141) vs. 630 (326-1152) AU/mL, P = 0.337). Adjustment for age, sex, BMI and lipid parameters did not change this result. Furthermore we did not find a correlation between anti-hsp70 antibody levels and certain risk factors of CAD (age, lipid parameters, body mass index, C-reactive protein, gender, smoking, diabetes and anti-hsp60 antibodies). By contrast, in accordance with our previous findings, anti-hsp60 and anti-hsp65 antibody levels were significantly higher in CAD patients, compared to this control group (p < 0.0001 for both variables). We did not find any correlation between the levels of anti-hsp70 and anti-hsp60 or anti-hsp65 antibodies either in the patients or the controls. The exact role of hsp70 in atherosclerosis is controversial, but we suggest that humoral immunity against human hsp70 does not contribute to coronary atherosclerosis in contrast to antibodies against 60kDa hsps.     

ANTIBODIES AGAINST THE HUMAN HEAT SHOCK PROTEIN hsp70 IN PATIENTS WITH SEVERE CORONARY ARTERY DISEASE

Heat shock proteins (hsps) play complex role in the function of the immune system, they can activate both humoral and cellular immune response, as well the complement system. Although autoimmunity to hsp70 was implicated in certain autoimmune diseases and other conditions, the exact role of anti-hsp70 antibodies is not known. It was demonstrated by our previous work and other's findings that antibodies against the 60 kDa hsps are strongly associated with coronary atherosclerosis and carotis disease. It is also known that there is increased hsp70 expression at different sites of atherosclerosis. Therefore our aim was to study whether level of anti-hsp70 antibodies correlate with the presence of severe coronary artery disease (CAD). We measured and compared anti-hsp70 IgG antibody levels in CAD patients (n=99) and healthy subjects (n=99) with ELISA. The frequency of these antibodies was high in both groups and there was no significant difference in the median level of anti-hsp70 antibodies between patients with severe CAD and controls (653 (400–1141) vs. 630 (326–1152) AU/mL, P=0.337). Adjustment for age, sex, BMI and lipid parameters did not change this result. Furthermore we did not find a correlation between anti-hsp70 antibody levels and certain risk factors of CAD (age, lipid parameters, body mass index, C-reactive protein, gender, smoking, diabetes and anti-hsp60 antibodies). By contrast, in accordance with our previous findings, anti-hsp60 and anti-hsp65 antibody levels were significantly higher in CAD patients, compared to this control group (p<0.0001 for both variables). We did not find any correlation between the levels of anti-hsp70 and anti-hsp60 or anti-hsp65 antibodies either in the patients or the controls. The exact role of hsp70 in atherosclerosis is controversial, but we suggest that humoral immunity against human hsp70 does not contribute to coronary atherosclerosis in contrast to antibodies against 60 kDa hsps.     

Identification of dengue virus binding proteins using affinity chromatography

Several studies have identified putative dengue virus receptors using virus overlay protein binding assays (VOPBA) with some apparent success. Given that this technique relies upon the use of electrophoresis of proteins through polyacrylamide gels with varying amounts of protein denaturation, the physiological relevance of the proteins isolated is open to question. To address this issue a Sepharose 4B-dengue virus serotype 2-affinity column was constructed to selectively bind dengue virus binding proteins from HepG2 (liver) cell membrane preparations. Results show that GRP78, but not the 37/67 kDa high affinity laminin receptor, was specifically bound by the column. This result is consistent with earlier work and shows that while affinity chromatography may provide a useful adjunct to VOPBA based studies particularly in cases where proteins maybe sensitive to denaturation, proteins isolated by VOPBA can be physiologically relevant.     

GRP78 up-regulation is associated with androgen receptor status, Hsp70-Hsp90 client proteins and castrate-resistant prostate cancer

GRP78/BiP is a key member of the molecular chaperone heat shock protein (Hsp) 70 family. It has a critical role in prostate cancer (PC) including Pten loss‐driven carcinogenesis, but the molecular basis of this remains unclear. We investigated the effect of GRP78 and its putative client proteins, including androgen receptor (AR) in clinical PC. Expression of GRP78 and key Hsp70–hsp90 client proteins (HER2, HER3, AR and AKT) were studied in an incidence tissue microarray (TMA) of prostate cancer. The relationship of GRP78 and AR was further tested in in vitro cell models (LNCaP and its derived LNCaP‐CR subclone) and a matched TMA of hormone‐naïve (HNPC) and castrate‐resistant prostate cancer (CRPC). In vitro and in vivo expression of GRP78 and client proteins were assessed by western blotting and immunohistochemistry, respectively, using the weighted histoscore method. Significant co‐expression of GRP78, pAKT, HER2, HER3 and AR was observed in PC. Abnormal AR, GRP78 and pAKT expression have significant impact on patient survival. GRP78 expression in AR⁺ tumours was significantly higher than in AR^? tumours. In keeping with our clinical data, activation of AR by dihydrotestosterone (DHT) potently activated GRP78 expression in both LNCaP and LNCaP‐CR cells. For the first time, using a matched HNPC and CRPC TMA, enhanced cytoplasmic and membranous GRP78 expression was observed in CRPC. Future prospective studies are therefore warranted to validate GRP78 as prognostic marker and therapeutic target, in the context of the AR and pAKT status. In summary, GRP78 is co‐expressed with Hsp70–hsp90 client proteins. Up‐regulated expression of AR and GRP78 expression in untreated prostate cancer predicts a less favourable outcome. This points to the importance of understanding in the molecular interaction among AR, GRP78 and AKT. Copyright © 2010 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.     

Comparison of the stress response to cryopreservation in monolayer and three-dimensional human fibroblast cultures: stress proteins, MAP kinases, and growth factor gene expression

Stress responses induced in fibroblasts by cryopreservation were compared in suspension or three-dimensional cultures at various times up to 5 days of recovery. Cryopreservation caused an 86% inhibition in [(35)S]methionine incorporation, with recovery over 2 days to 45% ±: 14% of its original value. Stress proteins, including heat shock protein (hsp) and glucose-regulated proteins (GRP), detected by immunoblotting, responded with transient increases in cellular content (hsp27 and hsp90 in suspension and three-dimensional culture, and hsp70 only in three-dimensional culture), decreases at 24 h (hsp56, hsp70, hsp90, and GRP78 in three-dimensional culture and hsp90 in suspension), or little change (hsp70 in suspension). Polyacrylamide gel electrophoresis of [(35)S]methionine-labeled proteins showed transient induction of hsp47 within 4 h, and increased synthesis of hsp90 and GRP78 and other unidentified proteins at 24 h, but no change in hsp70. The mitogen-activated protein (MAP) kinase, p38, showed a transient increase after thawing, followed by a peak in extracellular signal-regulated kinase at 24 h. The stress-activated protein kinase (JNK) was not activated. In both stress protein and MAP kinase responses, the three-dimensional cultures showed a more intense response than fibroblasts in suspension. Although some responses were related to osmotic and cold stress during freezing, others were unique. Cryopreservation induced mRNA for selected growth factors, including vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF) A chain, which increased 5- to 20- fold at 48 h returning to basal levels by 120 h. Our results indicate the novel finding that cryopreservation of fibroblasts grown in three-dimensional culture induced a specific cellular stress response including growth factors.     

Expression of heat-shock proteins hsp27, hsp70 and hsp90 in malignant epithelial tumour of the ovaries

Recently, considerable attention has been focused on the role of the small heat-shock protein group hsp27, hsp70 and hsp90 in the clinical outcome of several malignancies. However, conflicting data exist regarding the prognostic role of hsp27 expression in ovarian carcinoma, and the prognostic significance of hsp70 and hsp90 expression still remains unknown in these tumours. The purpose of this study was to investigate immunohistochemically whether hsp27, hsp70 and hsp90 expression was associated with clinicopathological parameters and survival in 52 epithelial ovarian carcinomas. Chi-square test, Kaplan-Meier and Cox regression analysis were used for statistical analysis. Among clinicopathological parameters, hsp27, hsp70 and hsp90 expression was only correlated with FIGO stage; hsp70 and hsp90 positivity failed to detect survival. However, the overall survival rate of patients with hsp27 expression was 13%, which was significantly worse than that of patients without hsp27 expression (47%) (p<0.01). The prognosis was also adversely affected by FIGO stage (p<0.01) and presence of ascites (p<0.01). In multivariate analysis, hsp27 expression and FIGO stage were independent prognostic variables. Our results indicate that hsp70 and hsp90 expression had no prognostic relevance in epithelial ovarian carcinomas. However, hsp27 expression and FIGO stage in these tumours could be reliable indicators of prognosis.     

Production of anti-dengue NS1 monoclonal antibodies by DNA immunization

Monoclonal antibodies against dengue NS1 protein were generated following immunization of mice with plasmid DNA encoding the transmembrane form of NS1 from dengue serotype 2 virus. A mammalian expression vector, pDisplay, was engineered to direct cell surface expression of dengue NS1 and tested for transient expression in COS cells. Two mice were immunized intramuscularly with six doses of 100 microg of plasmid at 2-week intervals; one mouse received a booster of live virus prior to the last plasmid injection. Both mice showed antibody responses against dengue antigens in dot enzyme immunoassay. Following fusion, hybridomas were screened with dot enzyme immunoassay against all four dengue serotypes. Specificity to the NS1 protein was confirmed by western blot analysis. Among five anti-dengue NS1 monoclonal antibodies generated, two clones were serotype 2 specific, two clones reacted with all four serotypes and the last also reacted with Japanese encephalitis virus. Reactivity against native or denatured forms of NS1 revealed three clones with reactivity to linear epitopes and two clones recognizing conformational epitopes. Such diverse specificity of anti-dengue NS1 monoclonal antibodies indicates that DNA immunization, especially with the combination of virus boosting, is an efficient way of producing monoclonal antibodies against viral protein. This has opened up a possibility of producing monoclonal antibodies to rare viral proteins that are difficult to isolate or purify.     

Pharmacologic and genetic inhibition of hsp90-dependent trafficking reduces aggregation and promotes degradation of the expanded glutamine androgen receptor without stress protein induction

The molecular chaperone hsp90 has emerged as an important therapeutic target in cancer and neurodegenerative diseases, including the polyglutamine expansion disorders, because of its ability to regulate the activity, turnover and trafficking of many proteins. For neurodegenerative disorders associated with protein aggregation, the rationale has been that inhibition of hsp90 by geldanamycin and related compounds activates heat shock factor 1 (HSF1) to induce the production of the chaperones hsp70 and hsp40 that promote disaggregation and protein degradation. However, we show here that geldanamycin blocks the development of aggregates of the expanded glutamine androgen receptor (AR112Q) of Kennedy disease in Hsf1(-/-) mouse embryonic fibroblasts where these chaperones are not induced. Geldanamycin is additionally known to inhibit hsp90-dependent protein trafficking and to promote proteasomal degradation of client proteins. Overexpression of the hsp90 cochaperone p23 also promotes AR112Q degradation, and inhibits both AR trafficking and AR112Q aggregation without altering levels of hsp70 or hsp40. The hsp90-dependent trafficking mechanism has been defined, and it is shown that key immunophilin (IMM) components of the trafficking machinery are present in polyglutamine aggregates in cell and mouse models of Kennedy disease. Our results indicate that inhibition of the hsp90-dependent trafficking mechanism prevents aggregation of the expanded glutamine androgen receptor, thereby opening a variety of novel therapeutic approaches to these neurodegenerative disorders.     

Liver injury caused by antibodies against dengue virus nonstructural protein 1 in a murine model

Clinical manifestations of severe dengue diseases include thrombocytopenia, vascular leakage, and liver damage. Evidence shows that hepatic injury is involved in the pathogenesis of dengue infection; however, the mechanisms are not fully resolved. Our previous in vitro studies suggested a mechanism of molecular mimicry in which antibodies directed against dengue virus (DV) nonstructural protein 1 (NS1) cross-reacted with endothelial cells and caused inflammatory activation and apoptosis. In this study, the pathogenic effects of anti-DV NS1 antibodies were further examined in a murine model. We found, in liver sections, that anti-DV NS1 antibodies bound to naive mouse vessel endothelium and the binding activity was inhibited by preabsorption of antibodies with DV NS1. Active immunization with DV NS1 resulted in antibody deposition to liver vessel endothelium, and also apoptotic cell death of liver endothelium. Liver tissue damage was observed in DV NS1-immunized mice by histological examination. The serum levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) were increased in mice either actively immunized with DV NS1 protein or passively immunized with antibodies obtained from DV NS1-immunized mice. Furthermore, histological examination revealed mononuclear phagocyte infiltration and cell apoptosis in mice passively immunized with antibodies obtained from mice immunized with DV NS1. Increased AST and ALT levels were observed in mice passively immunized with purified immunoglobulin G (IgG) from dengue patients compared with normal control human IgG-immunized mice. The increased AST and ALT levels were inhibited when dengue patient serum IgG was preabsorbed with DV NS1. In conclusion, active immunization with DV NS1 protein causes immune-mediated liver injury in mice. Passive immunization provides additional evidence that anti-DV NS1 antibodies may play a role in liver damage, which is a pathologic manifestation in dengue virus disease.     

Dengue virus neutralization by human immune sera: Role of envelope protein domain III-reactive antibody

Dengue viruses (DENV) are the etiological agents of dengue fever (DF) and dengue hemorrhagic fever (DHF). The DENV complex consists of four closely related viruses designated DENV serotypes 1 through 4. Although infection with one serotype induces cross reactive antibody to all 4 serotypes, the long-term protective antibody response is restricted to the serotype responsible for infection. Cross reactive antibodies appear to enhance infection during a second infection with a different serotype. The goal of the present study was to characterize the binding specificity and functional properties of human DENV immune sera. The study focused on domain III of the viral envelope protein (EDIII), as this region has a well characterized epitope that is recognized by strongly neutralizing serotype-specific mouse monoclonal antibodies (Mabs). Our results demonstrate that EDIII-reactive antibodies are present in primary and secondary DENV immune human sera. Human antibodies bound to a serotype specific epitope on EDIII after primary infection and a serotype cross reactive epitope on EDIII after secondary infection. However, EDIII binding antibodies constituted only a small fraction of the total antibody in immune sera binding to DENV. Studies with complete and EDIII antibody depleted human immune sera demonstrated that EDIII binding antibodies play a minor role in DENV neutralization. We propose that human antibodies directed to other epitopes on the virus are primarily responsible for DENV neutralization. Our results have implications for understanding protective immunity following natural DENV infection and for evaluating DENV vaccines.     

Contribution of heat shock proteins to cell protection from complement-mediated lysis

The possible participation of hsc70 and hsp70 in cellular protection from complement damage was studied. Human erythroleukemia K562 cells were pretreated with reagents affecting hsc70 or hsp70, and cell sensitivity to lysis by antibody and human complement was examined. Treatment with deoxyspergualin, an hsc70 inhibitor, sensitized K562 cells to complement lysis, whereas treatment with ethanol, butanol or hemin, inducers of hsc70 synthesis, protected the cells from complement-mediated lysis. Incubation of K562 at either 42 degrees C or with the amino acid analogue L-azetidine-2-carboxylic acid induced synthesis of hsp70, but not of hsc70. The latter treatment also conferred elevated resistance to complement lysis on K562 cells. Pretreatment of K562 cells with sub-lethal doses of complement desensitizes them to lethal complement doses. No effect of sublytic complement on synthesis of hsc70 and hsp70 was found. However, the results demonstrated that complement stress causes translocation of hsc70 from the cytoplasm to the K562 cell surface. Two monoclonal and two polyclonal antibodies identified hsc70 on the surface of intact, viable complement-stressed cells, while antibodies directed to hsp70 did not bind to these cells. Altogether, the results suggest that the heat shock proteins hsc70 and hsp70 play a role in cell defense against complement.     

Analysis of hsp70 gene polymorphism in allergic asthma

BACKGROUND: Allergic asthma is a multifactorial and probably multigenic inflammatory disease of the upper airways, and has been associated with the HLA class II alleles DR4 and DR7. Here we investigated possible associations with other polymorphic susceptibility/resistance genes located within the major histocompatibility complex, i.e., the genes coding the major 70-kDa heat-shock proteins (HSP; Hsp70) hsp70-1, hsp70-2, and hsp70-HOM, whose products are overexpressed in the bronchi of asthmatic patients. METHODS: Genomic DNA was extracted from peripheral blood lymphocytes or buccal epithelial cells of 48 patients with allergic asthma and 31 selected nonatopic control subjects, in whom we previously reported a strong association of atopy with DR4/DR7 alleles. RESULTS: No evidence was found for an independent role of hsp70 gene polymorphism in susceptibility to allergic asthma. However, hsp70 alleles might be involved in extended haplotypes of HLA markers. CONCLUSIONS: Our data suggest that Hsp70 overexpression in asthma results from complex interactions between environmental exposures and genetic background rather than from specific genetic variations in hsp70 genes.     

Influence of the human high-affinity IgG receptor FcgammaRI (CD64) on residual infectivity of neutralized dengue virus.

We examined dengue virus immune complex-phagocyte interaction with respect to a single Fc receptor class using a transient expression system involving the high-affinity human macrophage receptor, FcgammaRI. We found that New Guinea C strain dengue 2 virus formed well-defined plaques in normal and transfected COS cells and we analyzed the structural determinants of FcgammaRI-mediated binding and internalization of dengue 2 virus immune complexes by expressing native or truncated forms of the receptor in COS cells, alone or with its accessory gamma chain signaling unit, which bears an immunoreceptor tyrosine-based activation motif (ITAM). The residual infectivity of dengue 2 virus treated with neutralizing human antiserum was strikingly higher in FcgammaRI-bearing COS cells than in controls. Compatible with the IgG subclass specificity of FcgammaRI, this difference was abrogated quantitatively by treatment of FcgammaRI-transfected cells with human IgG1 but not IgG2 myeloma protein. The magnitude of receptor-mediated plaque formation after cotransfection with gamma chain was also significantly higher than in controls but was less than that observed with FcgammaRI transfection only, a difference probably explained by reduced levels of FcgammaRI expression in gamma chain cotransfectants. Deletion of the FcgammaRI cytoplasmic domain had no effect on receptor-mediated immune complex infectivity. We conclude that the FcgammaRI extracellular domain is sufficient for internalization of infectious dengue virus immune complexes through a mechanism that does not involve classical ITAM-dependent signaling.     

Heat shock effect upon dengue virus replication into U937 cells

The molecules involved in dengue virus entry into human cells are currently unknown. We have previously shown that two surface heat shock proteins (Hsps), Hsp90 and Hsp70 are part of a receptor complex in monocytic cells. In the present report, the effect of heat shock (HS) on dengue virus infection is analyzed. We have documented a more than twofold increase in dengue virus infectivity after HS treatment in monocytic cells U937; this effect correlates mainly with an increase in viral entry due to a major presence of both Hsps on the surface of monocytic cells, particularly in membrane microdomains. Interestingly, since heat shock treatment at 6h post-infection also increased viral yields, it is likely that HS also modulates positively dengue virus replication.     

Induction of human hsp60 expression in monocytic cell lines.

Both bacterial and mammalian heat shock proteins (HSP) are recognized by some T cells, and hsp60 recognition has been implicated in rheumatoid arthritis. We have developed a model to study the induction of hsp60 in human monocytic cell lines. An anti-mycobacterial hsp65 mAb (ML30), cross-reacting with human hsp60 was used to screen 21 human tumor cell lines in Western blot analysis. All T cell and B cell lymphomas constitutively expressed hsp60 protein at moderate to high levels, while little or no hsp60 protein was detected in two monocytic leukemia lines. Moderate to high levels of hsp60 mRNA and protein could be induced in the THP-I monocytic leukemia cell line by heat shock, retinoic acid, interferon (IFN)-gamma or tumor necrosis factor (TNF)-alpha treatment, the highest levels obtained with a combination of IFN-gamma/TNF-alpha. This was also seen using two rabbit anti-hsp60 antisera directed against the N-terminal or C-terminal part of the human hsp60 protein. The determinants detected by the ML30 mAb or the two rabbit anti-hsp60 antisera were not cell surface expressed, as measured with immunofluorescence (FACS) analysis on control cultured or cytokine treated cell lines. This could be a useful model for studies related to the induction of hsp60 in human cells.     

Design of novel Geldanamycin analogue hsp90 alpha-inhibitor in silico for breast cancer therapy

Background

Geldanamycin, which is one of the most potent and effective hsp90 alpha inhibitor until date, is normally used to target breast cancer. Inhibition of hsp90 alpha leads to the degradation of client proteins involved in the initiation and progress of breast cancer pathogenesis. Hence, Geldanamycin has been widely pursued as a treatment option for breast cancer. However, it failed to move into the clinics due to the toxicity associated with its solubility. Geldanamycin was modified chemically to develop 17-N-allylamino-17-demethoxygeldanamycin (17-AAG) and later 17-Dimethylaminoethylamino-17-demethoxygeldanamycin (17-DMAG), which have higher solubility and lesser toxicity. Nonetheless, in order to achieve highest efficacy against breast cancer, a more potent, soluble and least toxic hsp90 alpha inhibitors need to be developed.

Hypothesis

We hypothesize that designing a novel Geldanamycin analogue with increased affinity and efficacy would provide a probability of having less toxic effect in the therapy of breast cancer. We also hypothesize that hsp90 alpha forms a multi-chaperone complex with hsp70 and hsp40 and thus assist the folding and maturation of number of client proteins including cellular p53. We further hypothesize that the higher binding affinity of the novel Geldanamycin analogue for hsp90 alpha triggers the degradation of nonfunctional mutant p53 by cellular proteasomes.

Experimental design

Ten different Geldanamycin analogues were designed using Marvinsketch software. Binding affinity of hsp90 alpha and its complex (hsp70, hsp40) with wild type p53 and mutant p53 were determined using Hex 6.3. Binding affinities of ten different analogues for hsp90 alpha were determined by estimating binding energies of molecules using Hex 6.3 and Autodock 4.0 softwares.

Results

The estimation of molecular docking energies using Hex 6.3 and Autodock 4.0 software proved that Analogue 9 was the best hsp90 alpha inhibitor among all ten analogues designed and the existing inhibitors. Following hsp90 alpha inhibition using Analogue 9 and subsequent docking results using Hex 6.3 software showed less binding affinity of Analogue 9 for mutant p53 than the wild version, suggesting the increased chance of the degradation of mutant p53 by cellular machines.

Conclusions

Based on our findings, we propose Analogue 9 to be the more efficient hsp90 alpha inhibitor than existing inhibitors. Furthermore, the chemical synthesis of Analogue 9 at the laboratory scale and successful in vitro and in vivo studies in breast cancer model would lead the compound into the clinical stage.     

Retrospective study of Western blot profiles in immune sera of natural dengue virus infections

The Western blot (WB) assay was used to determine dengue virus antibodies present in human immune sera arising from recent primary and secondary dengue virus infections in Singapore. Cell lysates of dengue-2 virus-infected C6/36 and Vero cells were used. Antibodies directed against structural proteins of dengue-2 virus including envelope (E, gp60/50), capsid-premembrane (C-PrM, gp35), and premembrane (PrM, gp20) were detected, with antibody against envelope protein being most dominant. Similar WB profiles were detected in both primary and secondary dengue virus infections. The reactivity rate of antibodies to dengue-2 virus proteins was higher in infected Vero cell lysate than in infected C6/36 cell lysate, with the exception of antibodies to nonstructural proteins of NS1 and NS3, which were detected predominantly in infected C6/36 cell lysate. More than 75% of "normal" individuals (with no complaint of recent dengue virus infection) examined had low levels of dengue virus antibodies, but all presented with similar WB profiles as patients with recent dengue virus infections. This finding reflects a high seroprevalence of dengue virus infections and the long lasting nature of E, C-PrM, and PrM antibodies. Results from this study indicate that in natural dengue virus infections, native E, C-PrM, and PrM antigens of dengue virus are immunogenic and elicit long-lasting antibodies.     

CD91 is a common receptor for heat shock proteins gp96, hsp90, hsp70, and calreticulin

Complexes of the heat shock protein gp96 and antigenic peptides are taken up by antigen-presenting cells and presented by MHC class I molecules. In order to explain the unusual efficiency of this process, the uptake of gp96 had been postulated to occur through a receptor, identified recently as CD91. We show here that complexes of peptides with heat shock proteins hsp90, calreticulin, and hsp70 are also taken up by macrophages and dendritic cells and re-presented by MHC class I molecules. All heat shock proteins utilize the CD91 receptor, even though some of the proteins have no homology with each other. Postuptake processing of gp96-chaperoned peptides requires proteasomes and the transporters associated with antigen processing, utilizing the classical endogenous antigen presentation pathway.