HSP90 protects apoptotic cleavage of vimentin in geldanamycin-induced apoptosis

Caspase-9-mediated cleavage of vimentin attenuates the aggressiveness of leukemic NB4 cells

Vimentin is a main type 3 intermediate filament protein. It seems that abnormal expression of vimentin is contributed to the appearance of the aggressive feature of cancer cells. So that it has been reported that malignancy and epithelial-mesenchymal transition in solid tumors, and poor clinical outcomes in patients with lymphocytic leukemia and acute myelocytic leukemia have been associated with the high expression of vimentin. Vimentin is a non-caspase substrate of caspase-9 although its cleavage by caspase-9 in biological processes has not been reported. In the present study, we sought to understand whether vimentin cleavage mediated by caspase-9 could reverse the malignancy in leukemic cells. Herein, to address the issue, we investigated vimentin changes in differentiation and took advantage of the inducible caspase-9 (iC9)/AP1903 system in human leukemic NB4 cells. Following the transfection and treatment of the cells using the iC9/AP1903 system, vimentin expression, cleavage, and subsequently, the cell invasion and the relevant markers such as CD44 and MMP-9 were evaluated. Our results revealed the downregulation and cleavage of vimentin which attenuates the malignant phenotype of the NB4 cells. Considering the favorable effect of this strategy in keeping down the malignant features of the leukemic cells, the effect of the iC9/AP1903 system in combination with all-trans-retinoic acid (ATRA) treatment was evaluated. The obtained data prove that iC9/AP1903 significantly makes the leukemic cells more sensitive to ATRA.

A review of protein-protein interaction and signaling pathway of Vimentin in cell regulation, morphology and cell differentiation in normal cells

The Vimentin intermediate filament (VIF) is an essential cytoskeleton component. It shows dynamically changing expression patterns throughout various phases of the differentiation process, suggesting that the protein is physiologically important. Vimentin's essential functions have recently been clear, so Vimentin-deficient of animals was described as a change of morphology and signaling pathway. Recent research has discovered many vital roles for Vimentin that were previously unknown. VIF emerges as an organizer of many essential proteins involved in movement and cell signaling. The highly dynamic and complicated phosphorylation of VIF seems to be a regulator mechanism for various activities. Changes in IF expression patterns are often linked with cancer progression, especially those leading to enhanced invasion and cellular migration. This review will discuss the function of Vimentin intermediate filaments in normal cell physiology, cell adhesion structures, cell shape, and signaling pathways. The genes interaction and gene network linked with Vimentin will be discussed in more studies. However, research aimed at understanding the function of Vimentin in different signaling cascades and gene interactions might offer novel methods for creating therapeutic medicines. Enrichr GEO datasets used gene ontology (GO) and pathway enrichment analyses. STRING online was used to predict the functional connections of proteins-proteins, followed by Cytoscape analysis to find the master genes. Cytoscape and STRING research revealed that eight genes, Fas, Casp8, Casp6, Fadd, Ripk1, Des, Tnnc2, and Tnnt3, were required for protein-protein interactions with Vimentin genes involved in cell differentiation.

The heat shock response and small molecule regulators

The heat shock response (HSR) is a highly conserved cellular pathway that is responsible for stress relief and the refolding of denatured proteins [1]. When a host cell is exposed to conditions such as heat shock, ischemia, or toxic substances, heat shock factor-1 (HSF-1), a transcription factor, activates the genes that encode for the heat shock proteins (Hsps), which are a family of proteins that work alongside other chaperones to relieve stress and refold proteins that have been denatured (Burdon, 1986) [2]. Along with the refolding of denatured proteins, Hsps facilitate the removal of misfolded proteins by escorting them to degradation pathways, thereby preventing the accumulation of misfolded proteins [3]. Research has indicated that many pathological conditions, such as diabetes, cancer, neuropathy, cardiovascular disease, and aging have a negative impact on HSR function and are commonly associated with misfolded protein aggregation [4,5]. Studies indicate an interplay between mitochondrial homeostasis and HSF-1 levels can impact stress resistance, proteostasis, and malignant cell growth, which further support the role of Hsps in pathological and metabolic functions [6]. On the other hand, Hsp activation by specific small molecules can induce the heat shock response, which can afford neuroprotection and other benefits [7]. This review will focus on the modulation of Hsps and the HSR as therapeutic options to treat these conditions.

Loss of ARID1A Promotes Epithelial-Mesenchymal Transition and Sensitizes Pancreatic Tumors to Proteotoxic Stress

Cellular dedifferentiation is a key mechanism driving cancer progression. Acquisition of mesenchymal features has been associated with drug resistance, poor prognosis, and disease relapse in many tumor types. Therefore, successful targeting of tumors harboring these characteristics is a priority in oncology practice. The SWItch/Sucrose non-fermentable (SWI/SNF) chromatin remodeling complex has also emerged as a critical player in tumor progression, leading to the identification of several SWI/SNF complex genes as potential disease biomarkers and targets of anticancer therapies. AT-rich interaction domain-containing protein 1A (ARID1A) is a component of SWI/SNF, and mutations in ARID1A represent one of the most frequent molecular alterations in human cancers. ARID1A mutations occur in approximately 10% of pancreatic ductal adenocarcinomas (PDAC), but whether these mutations confer a therapeutic opportunity remains unclear. Here, we demonstrate that loss of ARID1A promotes an epithelial-mesenchymal transition (EMT) phenotype and sensitizes PDAC cells to a clinical inhibitor of HSP90, NVP-AUY922, both in vitro and in vivo. Although loss of ARID1A alone did not significantly affect proliferative potential or rate of apoptosis, ARID1A-deficient cells were sensitized to HSP90 inhibition, potentially by promoting the degradation of intermediate filaments driving EMT, resulting in cell death. Our results describe a mechanistic link between ARID1A defects and a quasi-mesenchymal phenotype, suggesting that deleterious mutations in ARID1A associated with protein loss exhibit potential as a biomarker for patients with PDAC who may benefit by HSP90-targeting drugs treatment. SIGNIFICANCE: This study identifies ARID1A loss as a promising biomarker for the identification of PDAC tumors that are potentially responsive to treatment with proteotoxic agents.

Vimentin filaments interact with the actin cortex in mitosis allowing normal cell division

The vimentin network displays remarkable plasticity to support basic cellular functions and reorganizes during cell division. Here, we show that in several cell types vimentin filaments redistribute to the cell cortex during mitosis, forming a robust framework interwoven with cortical actin and affecting its organization. Importantly, the intrinsically disordered tail domain of vimentin is essential for this redistribution, which allows normal mitotic progression. A tailless vimentin mutant forms curly bundles, which remain entangled with dividing chromosomes leading to mitotic catastrophes or asymmetric partitions. Serial deletions of vimentin tail domain gradually impair cortical association and mitosis progression. Disruption of f-actin, but not of microtubules, causes vimentin bundling near the chromosomes. Pathophysiological stimuli, including HIV-protease and lipoxidation, induce similar alterations. Interestingly, full filament formation is dispensable for cortical association, which also occurs in vimentin particles. These results unveil implications of vimentin dynamics in cell division through its interplay with the actin cortex.

The intermediate filament vimentin reorganizes during mitosis, but its molecular regulation and impact on the cell during cell division is unclear. Here, the authors show that vimentin filaments redistribute to the cell cortex during mitosis intertwining with and affecting actin organization.

A Binding Potency Assay for Pritumumab and Ecto-Domain Vimentin

Pritumumab, a natural human IgG1kappa mAb, was isolated from the regional lymph node of a patient with cervical cancer. This antibody has been reported to bind the cytoskeletal protein vimentin, and to cell surface expressed vimentin referred to as ecto-domain vimentin (EDV). Here, we report details of the development of a potency of binding assay for pritumumab as a prerequisite before pursuing clinical trials. The enzyme linked immunosorbent assay (ELISA) to detect antibody-binding antigen can serve as a potency assay for release of manufactured samples to be used in clinical studies. Several layers of controls for this assay along with suitability testing for reagents and components of the assay must be developed before the assay can be incorporated for stability testing and release of manufatured samples.

Upregulation of the EMT marker vimentin is associated with poor clinical outcome in acute myeloid leukemia

Background

Vimentin (VIM) is a type III intermediate filament that maintains cell integrity, and is involved in cell migration, motility and adhesion. When overexpressed in solid cancers, vimentin drives epithelial to mesenchymal transition (EMT) and ultimately, metastasis. The effects of its overexpression in AML are unclear.

Methods

In this study, we analyzed the TCGA data of 173 AML patients for which complete clinical and expression data were available. In this analysis, we assessed the association between VIM mRNA expression and patient’s clinical and molecular characteristics including clinical outcome.

Results

VIM overexpression was associated with higher white blood count (< p = 0.0001). Patients with high VIM expression have worse overall survival (OS) and disease-free survival (DFS) compared with patients with low VIM expression (median OS; 7.95 months vs 19.2 months; p = 0.029). After age-stratification, high VIM expression was significantly associated with worse overall survival in older patients (age ≥ 60; median OS: 5.4 vs 9.9 months: p = 0.0257) but not in younger patients (age < 60). In stratification analysis according to cytogenetic status, high VIM expression was significantly associated with shorter OS (7.95 vs 24.6 months: p = 0.0102) in cytogenetically normal, but not in cytogenetic abnormal AML.

Conclusions

Collectively, the data indicate that overexpression of the EMT marker vimentin is associated with poor clinical outcome in older patients with cytogenetically normal AML; and therefore may play a role in this disease.

Electronic supplementary material

The online version of this article (10.1186/s12967-018-1539-y) contains supplementary material, which is available to authorized users.

The meaning of the anti-cancer antibody CLN-IgG (Pritumumab) generated by human × human hybridoma technology against the cyto-skeletal protein, vimentin, in the course of the treatment of malignancy

Cancer stem cells in a tumor mass form a very small subpopulation ranging from below 0.1% in a brain tumor but they have the crucial ability to become malignant. The goal of cancer therapy has been the total killing of tumor cells. However we should clarify that most of all tumor cells are differentiated cancer cells. Thus the elimination of 99.9% of tumor cells under histological criteria cannot ensure the cancer will be cured. Rather cancer cell biologists should turn their attention to reprogramming cancer stem cells to normal stem cells by which malignancy recuperates normal organogenesis from the aspect of the dichotomy of cancer stem cell. The cue points underlying the reverse cancer stem cell at blastogenesis in inflammation site is depending upon cell-to-cell recognition of the tumor-niche cells. Normalization of tumor-niche promises to lead cancer stem cell into normal stem cell owing to autonomous healing mechanisms that reside in the self-defense mechanisms in immunity and the cell competition mechanisms in the wound healing of the tissue cells. Among the cyto-skeletal proteins, vimentin becomes a target of self-restoration of cancer stem cell by means of immune surveillance. A human monoclonal antibody, CLN-IgG recognizes vimentin expressing on the cell surface of the malignant tumor. Since vimentin network resides in the cytoplasm connecting the plasma membrane with chromatin assembly in the nucleus, it is highly likely vimentin plays an important role in up-regulation and down-regulation through signal transduction between certain membrane receptors and gene expression with respect to the transformation of the cell. Aberrant arrangement of vimentin undergoes malignancy accompanied by epithelial-mesenchymal-transition relating to the aberrant apoptotic cellular behavior in the tumor-niche. Restraint of the aberrant expression of vimentin on the plasma membrane of the malignant cell evokes a pertinent signal transduction pathway for healing that is an indication there must be a reverse path that reprograms cancer stem cells to normal organogenesis.

The complexity of identifying cancer stem cell biomarkers

The efficacy of glioma therapy can be considerably improved if it eliminates cancer stem cells (CSCs); however, to achieve this, CSCs markers are required. This study investigated the influence of micro-environmental changes on CSCs in hypoxic, serum deprived U87-MG and the corresponding control cells. Proteomic analysis produced a wide dataset, depicting the changes that occur at the proteomic level in the differentiated and undifferentiated U87-MG cell line. With the IPA analysis, HPRD and literature reviews, 11 proteins were proposed as potential differentiated biomarkers for CSCs namely Hsp90β1, vimentin, PGK1, GAPDH, EIF4e, TPI1, HspA8, HNRNPK, NAMPT, CCSNK2A1, and ANXA2.

Risk assessment, disease prevention and personalised treatments in breast cancer: is clinically qualified integrative approach in the horizon?

Breast cancer is a multifactorial disease. A spectrum of internal and external factors contributes to the disease promotion such as a genetic predisposition, chronic inflammatory processes, exposure to toxic compounds, abundant stress factors, a shift-worker job, etc. The cumulative effects lead to high incidence of breast cancer in populations worldwide. Breast cancer in the USA is currently registered with the highest incidence rates amongst all cancer related patient cohorts. Currently applied diagnostic approaches are frequently unable to recognise early stages in tumour development that impairs individual outcomes. Early diagnosis has been demonstrated to be highly beneficial for significantly enhanced therapy efficacy and possibly full recovery. Actual paper shows that the elaboration of an integrative diagnostic approach combining several levels of examinations creates a robust platform for the reliable risk assessment, targeted preventive measures and more effective treatments tailored to the person in the overall task of breast cancer management. The levels of examinations are proposed, and innovative technological approaches are described in the paper. The absolute necessity to create individual patient profiles and extended medical records is justified for the utilising by routine medical services. Expert recommendations are provided to promote further developments in the field.

Human calmodulin methyltransferase: expression, activity on calmodulin, and Hsp90 dependence

Deletion of the first exon of calmodulin-lysine N-methyltransferase (CaM KMT, previously C2orf34) has been reported in two multigene deletion syndromes, but additional studies on the gene have not been reported. Here we show that in the cells from 2p21 deletion patients the loss of CaM KMT expression results in accumulation of hypomethylated calmodulin compared to normal controls, suggesting that CaM KMT is essential for calmodulin methylation and there are no compensatory mechanisms for CaM methylation in humans. We have further studied the expression of this gene at the transcript and protein levels. We have identified 2 additional transcripts in cells of the 2p21 deletion syndrome patients that start from alternative exons positioned outside the deletion region. One of them starts in the 2^nd known exon, the other in a novel exon. The transcript starting from the novel exon was also identified in a variety of tissues from normal individuals. These new transcripts are not expected to produce proteins. Immunofluorescent localization of tagged CaM KMT in HeLa cells indicates that it is present in both the cytoplasm and nucleus of cells whereas the short isoform is localized to the Golgi apparatus. Using Western blot analysis we show that the CaM KMT protein is broadly expressed in mouse tissues. Finally we demonstrate that the CaM KMT interacts with the middle portion of the Hsp90 molecular chaperon and is probably a client protein since it is degraded upon treatment of cells with the Hsp90 inhibitor geldanamycin. These findings suggest that the CaM KMT is the major, possibly the single, methyltransferase of calmodulin in human cells with a wide tissue distribution and is a novel Hsp90 client protein. Thus our data provides basic information for a gene potentially contributing to the patient phenotype of two contiguous gene deletion syndromes.

Molecular insight in the multifunctional activities of Withaferin A

Herbal medicine which involves the use of plants for their medicinal value, dates as far back as the origin of mankind and demonstrates an array of applications including cardiovascular protection and anti-cancer activities, via antioxidant, anti-inflammatory and metabolic activities. Even today the popularity of medicinal herbs is still growing like in traditional medicines such as the Indian medicine, Ayurveda. One of the Ayurvedic medicinal plants is Withania somnifera Dunal, of which the important constituents are the withanolides. Among them, Withaferin A is one of the most bioactive compounds, exerting anti-inflammatory, pro-apoptotic but also anti-invasive and anti-angiogenic effects. In the context of modern pharmacology, a better insight in the underlying mechanism of the broad range of bioactivities exerted by Withaferin A is compulsory. Therefore, a lot of effort was made to explore the intracellular effects of Withaferin A and to characterize its target proteins. This review provides a decisive insight on the molecular basis of the health-promoting potential of Withaferin A.

Heat shock proteins in hematopoietic malignancies

Inducible heat shock proteins are molecular chaperones whose expression is increased after many different types of stress. They have a protective function helping the cell to cope with lethal conditions. Their basal expression is low in nonstressed, normal and nontransformed cells. However, in cancer cells and particularly in hematological malignancies, they are surprisingly abundant. Malignant cells have to rewire their metabolic requirements and therefore have a higher need for chaperones. This cancer cell addiction for HSPs is the basis for the use of HSP inhibitors in cancer therapy. HSPs have been shown to interact with different key apoptotic proteins. As a result, HSPs can essentially block the apoptotic pathways at several steps, most of them involving the activation of cystein proteases called caspases. Apoptosis and differentiation are physiological processes that share many common features, for instance, a controlled caspase activation and chromatin condensation are frequently observed. It is, therefore, not surprising that HSPs may be implicated in the differentiation process. HSPs may determine the fate of the cells by orchestrating the decision of apoptosis versus differentiation. This review will focus on the role of HSPs in hematological malignancies and the emerging therapeutic options that are being either proposed or used to target these protective proteins.

Akt, 14-3-3ζ, and vimentin mediate a drug-resistant invasive phenotype in diffuse large B-cell lymphoma

Development of resistance to the CHOP chemotherapeutic regimen (cyclophosphamide, doxorubicin, vincristine, prednisone) remains a major cause of treatment failure and mortality in approximately 40% of patients with diffuse large B-cell lymphoma (DLBCL). We established CHOP-resistant DLBCL cells as a model system to investigate molecular mechanisms involved in multidrug resistance. Two-dimensional differential in-gel (DIGE) analysis identified 10 differentially expressed proteins between CHOP-sensitive and -resistant DLBCL cells that play roles in glycolysis (triosephosphate isomerase-1, enolase-1), cytoskeletal structure (ezrin, vimentin, tubulin-specific chaperone B), purine biosynthesis (serine hydroxymethyltransferase), calcium binding (sorcin), and apoptosis (p53, 14-3-3ζ, Akt). Akt, 14-3-3ζ, and vimentin were up-regulated in CHOP-resistant DLBCL cells. We showed previously that siRNA-mediated knockdown of 14-3-3ζ reversed CHOP resistance in DLBCL cells (Maxwell et al., J Biol Chem 2009;284:22379-22389). Here we show that chemical inhibition of Akt overcomes CHOP resistance in DLBCL cells. CHOP-resistant cells exhibited a five-fold greater ability to invade collagen matrices compared with CHOP-sensitive cells. Knockdown of vimentin by siRNA or withaferin A repressed the invasiveness of CHOP-resistant cells in collagen matrices. Increased expressions of Akt, 14-3-3ζ, and vimentin were observed by Western blotting in primary DLBCL tissues relative to normal lymphatic tissue. The data implicate activation of an Akt-14-3-3ζ signaling pathway in promoting a multidrug-resistant phenotype associated with a vimentin-dependent invasive behavior in DLBCL cells.

Endogenous HIV-1 Vpr-mediated apoptosis and proteome alteration of human T-cell leukemia virus-1 transformed C8166 cells

HIV-1 viral protein R (Vpr) can induce cell cycle arrest and cell death, and may be beneficial in cancer therapy to suppress malignantly proliferative cell types, such as adult T-cell leukemia (ATL) cells. In this study, we examined the feasibility of employing the HIV-vpr gene, via targeted gene transfer, as a potential new therapy to kill ATL cells. We infected C8166 cells with a recombinant adenovirus carrying both vpr and GFP genes (rAd-vpr), as well as the vector control virus (rAd-vector). G(2)/M phase cell cycle arrest was observed in the rAd-vpr infected cells. Typical characteristics of apoptosis were detected in rAd-vpr infected cells, including sub-diploid peak exhibition in DNA content assay, the Hoechst 33342 accumulation, apoptotic body formation, mitochondrial membrane potential and plasma membrane integrity loss. The proteomic assay revealed apoptosis related protein changes, exhibiting the regulation of caspase-3 activity indicator proteins (vimentin and Rho GDP-dissociation inhibitor 2), mitochondrial protein (prohibitin) and other regulatory proteins. In addition, the up-regulation of anti-inflammatory redox protein, thioredoxin, was identified in the rAd-vpr infected group. Further supporting these findings, the increase of caspase 3&7 activity in the rAd-vpr infected group was observed. In conclusion, endogenous Vpr is able to kill HTLV-1 transformed C8166 cells, and may avoid the risks of inducing severe inflammatory responses through apoptosis-inducing and anti-inflammatory activities.

Low concentration of GA activates a preconditioning response in HepG2 cells during oxidative stress-roles of Hsp90 and vimentin

Oxidative stress can be a significant cause of cell death and apoptosis. We performed studies in HepG2 cells to explore whether prior exposure to oxidative stress ("oxidative preconditioning") and geldanamycin (GA) treatment can protect the cell from damage caused by subsequent oxidative insults. The cells were treated with 10 nM GA for 24 h before oxidative stress. Oxidative preconditioning was achieved by 2 h exposures to H(2)O(2) (50 microM) separated by a 10-h recovery period in normal culture medium. Oxidative stress was induced by exposure to 500 microM H(2)O(2) for 24 h. The effects of GA and oxidative preconditioning were investigated on the formation of Hsp90, vimentin, insoluble vimentin aggregates, and cleavage of vimentin in a cell culture model of oxidative stress. GA treatment leads to enhanced expression of Hsp90 and vimentin and to inhibition of vimentin protein aggregation. Similar results were obtained by oxidative preconditioning. It is confirmed that low concentrations of GA protected HepG2 cells from subsequent oxidative stress by increasing the levels of Hsp90 and by alleviating the extent of cell apoptosis induced by oxidative stress, which is similar to oxidative preconditioning. However, in contrast to preconditioning, GA treatment obviously changed binding activity of Hsp90 to vimentin cleavages. All the above indicated that low concentrations of GA treatment triggered cell protection from oxidative stress. Both the level of Hsp90 and its ability to bind with vimentin were changed by low concentrations of GA and might contribute to oxidative stress protection.

(-)-Epigallocatechin-3-gallate is a novel Hsp90 inhibitor

(-)-Epigallocatechin-3-gallate (EGCG), a major component of green tea, protects against certain types of cancers, although the mechanism has not yet been determined. It was previously demonstrated that EGCG blocks aryl hydrocarbon receptor (AhR)-mediated transcription induced by the potent carcinogen 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Unlike other AhR antagonists that directly bind to the AhR, EGCG inhibits AhR-mediated transcription by binding to hsp90. We hypothesize that EGCG exerts anti-AhR and anticancer effects by acting as an hsp90 inhibitor. Using proteolytic footprinting, immunoprecipitation, and an ATP-agarose pull-down assay, EGCG was found to directly modulate the conformation of hsp90 and bind at or near to a C-terminal ATP binding site. Hsp90 chaperone function, as assessed by its ability to mediate refolding of denatured luciferase, was inhibited by EGCG treatment. Hsp90 dimerization, which occurs at the C-terminal end, was also inhibited by EGCG treatment. Coimmunoprecipitation studies showed that EGCG stabilizes an AhR complex that includes hsp90 and XAP2 (hepatitis B virus X-associated protein 2), and decreases the association of aryl hydrocarbon nuclear translocator (Arnt) with ligand-activated AhR. Thus, EGCG, through its ability to bind to hsp90, blocks AhR response element (AhRE) recognition. These studies indicate a novel mechanism whereby EGCG inhibits ligand-induced AhRE binding and AhR-mediated transcriptional activity. In EGCG-treated human ovarian carcinoma SKOV3 cells, decreased levels of several cancer-related hsp90 client proteins, such as ErbB2, Raf-1 and phospho-AKT, were observed. EGCG also modified the association of hsp90 with several cochaperones. Overall, these data indicate that EGCG is a novel hsp90 inhibitor. Further studies are needed to determine if this has a role in the antitumor actions of EGCG.

Population origin, development and temperature of development affect the amounts of HSP70, HSP90 and the putative hypoxia-inducible factor in the tadpoles of the common frog Rana temporaria

We raised Rana temporaria tadpoles from three different populations from southern, mid and northern Sweden (the total north-to-south distance between populations is approximately 1500 km) at two temperatures, and measured the differences in HSP70, HSP90 and putative HIF-1alpha levels (Rana temporaria HIF-1alpha was sequenced in the present study) with immunoblotting. The levels of the studied proteins increased with developmental stage. Also, the levels increased with latitude at the lower but not at the higher developmental temperature. This shows that there is a clear difference between the populations at the molecular level but that this difference can be modified by the environmental conditions experienced during development. The proteins analyzed may be involved in the regulation of developmental processes. If this is the case, the tadpoles from the northernmost population have the most advanced complement of regulatory proteins at developmental stages approaching metamorphosis.

Heat shock proteins: essential proteins for apoptosis regulation

Many different external and intrinsic apoptotic stimuli induce the accumulation in the cells of a set of proteins known as stress or heat shock proteins (HSPs). HSPs are conserved proteins present in both prokaryotes and eukaryotes. These proteins play an essential role as molecular chaperones by assisting the correct folding of nascent and stress-accumulated misfolded proteins, and by preventing their aggregation. HSPs have a protective function, that is they allow the cells to survive to otherwise lethal conditions. Various mechanisms have been proposed to account for the cytoprotective functions of HSPs. Several of these proteins have demonstrated to directly interact with components of the cell signalling pathways, for example those of the tightly regulated caspasedependent programmed cell death machinery, upstream, downstream and at the mitochondrial level. HSPs can also affect caspase-independent apoptosis-like process by interacting with apoptogenic factors such as apoptosis-inducing factor (AIF) or by acting at the lysosome level. This review will describe the different key apoptotic proteins interacting with HSPs and the consequences of these interactions in cell survival, proliferation and apoptotic processes. Our purpose will be illustrated by emerging strategies in targeting these protective proteins to treat haematological malignancies.

Citrinin induces apoptosis via a mitochondria-dependent pathway and inhibition of survival signals in embryonic stem cells, and causes developmental injury in blastocysts

The mycotoxin CTN (citrinin), a natural contaminant in foodstuffs and animal feeds, has cytotoxic and genotoxic effects on various mammalian cells. CTN is known to cause cell injury, including apoptosis, but the precise regulatory mechanisms of CTN action, particularly in stem cells and embryos, are currently unclear. In the present paper, I report that CTN has cytotoxic effects on mouse embryonic stem cells and blastocysts, and is associated with defects in their subsequent development, both in vitro and in vivo. Experiments in embryonic stem cells (ESC-B5) showed that CTN induces apoptosis via ROS (reactive oxygen species) generation, increased Bax/Bcl-2 ratio, loss of MMP (mitochondrial membrane potential), induction of cytochrome c release, and activation of caspase 3. In this model, CTN triggers cell death via inactivation of the HSP90 [a 90 kDa isoform of the HSP (heat-shock protein) family proteins]/multichaperone complex and subsequent degradation of Ras and Raf-1, further inhibiting anti-apoptotic processes, such as the Ras-->ERK (extracellular-signal-regulated kinase) signal transduction pathway. In addition, CTN causes early developmental injury in mouse ESCs and blastocysts in vitro. Lastly, using an in vivo mouse model, I show that consumption of drinking water containing 10 muM CTN results in blastocyst apoptosis and early embryonic developmental injury. Collectively, these findings show for the first time that CTN induces ROS and mitochondria-dependent apoptotic processes, inhibits Ras-->ERK survival signalling via inactivation of the HSP90/multichaperone complex, and causes developmental injury in vivo.

Novel functions of vimentin in cell adhesion, migration, and signaling

Vimentin is the major intermediate filament (IF) protein of mesenchymal cells. It shows dynamically altered expression patterns during different developmental stages and high sequence homology throughout all vertebrates, suggesting that the protein is physiologically important. Still, until recently, the real tasks of vimentin have been elusive, primarily because the vimentin-deficient mice were originally characterized as having a very mild phenotype. Recent studies have revealed several key functions for vimentin that were not obvious at first sight. Vimentin emerges as an organizer of a number of critical proteins involved in attachment, migration, and cell signaling. The highly dynamic and complex phosphorylation of vimentin seems to be a likely regulator mechanism for these functions. The implicated novel vimentin functions have broad ramifications into many different aspects of cell physiology, cellular interactions, and organ homeostasis.

Cadmium-induced apoptosis in rat hepatocytes does not necessarily involve caspase-dependent pathways

Cadmium (Cd) is a well-known hepatotoxic environmental pollutant. Depending on the exposure conditions, Cd may cause necrosis or apoptosis. Oxidative stress is believed to participate in Cd toxicity but the molecular signaling responsible for Cd-induced apoptosis in non-malignant liver cells still needs to be clarified. Therefore we have studied apoptosis in primary cultures of rat hepatocytes incubated with low levels of Cd for short exposure times. Studies of nuclear morphology, chromatin condensation, and oligonucleosomal DNA fragmentation demonstrate that 1-5 microM Cd induces apoptosis as early as 6-12 h with minor effects on MTT activity. A concomitant time- and concentration-dependent increase in caspase-9 and -3 activities was observed, whereas Cd did not affect caspase-8 activity as much, suggesting a minor role of the death-receptor pathway. Significant release of cytochrome c into the cytosol demonstrated the involvement of a mitochondrial-dependent apoptotic pathway. However, cell pre-treatment with caspase inhibitors (Z-VAD-fmk or Ac-DEVD-CHO) did not prevent apoptosis. Increases in the cytosolic levels of the mitochondrial apoptosis-inducing factor (AIF) were also observed: kinetics of cytochrome c and AIF release were similar. These results show that Cd-induced apoptosis in rat hepatocytes is time- and concentration-dependent. The early apoptotic events involved mitochondrial-dependent pathways but not necessarily caspase-dependent signaling.