Optimization of expression and purification of human mortalin (Hsp70): Folding/unfolding analysis

Human mortalin is a Hsp70 mitochondrial protein that plays an essential role in the biogenesis of mitochondria. The deregulation of mortalin expression and its functions could lead to several age-associated disorders and some types of cancers. In the present study, we optimized the expression and purification of recombinant human mortalin by the use of two-step chromatography. Low temperature (18°C) and 0.5mM (IPTG) was required for optimum mortalin expression. Chaperone activity of mortalin was assessed by the citrate synthase and insulin protection assay, which suggested their protective role in mitochondria. Folding and unfolding assessments of mortalin were carried out in the presence of guanidine hydrochloride (GdnHCl) by intrinsic fluorescence measurement, ANS (8-analino 1-nephthlene sulfonic acid) binding and CD (circular dichroism) analysis. Under denaturing conditions, mortalin showed decrease in tryptophan fluorescence intensity along with a red shift of 11nm. Moreover, ANS binding studies illustrated decrease in hydrophobicity. CD measurement of mortalin showed a predominant helical structure. However, the secondary structure was lost at low concentration of GdnHCl (1M). We present a simple and robust method to produce soluble mortalin and warranted that chaperones are also susceptible to unfolding and futile to maintain protein homeostasis.

Eukaryotic Hsp70 chaperones in the intermembrane space of chloroplasts

MAIN CONCLUSION

Multiple eukaryotic Hsp70 typically localized in the cytoplasm are also distributed to the intermembrane space of chloroplasts and might thereby represent the missing link in energizing protein translocation. Protein translocation into organelles is a central cellular process that is tightly regulated. It depends on signals within the preprotein and on molecular machines catalyzing the process. Molecular chaperones participate in transport and translocation of preproteins into organelles to control folding and to provide energy for the individual steps. While most of the processes are explored and the components are identified, the transfer of preproteins into and across the intermembrane space of chloroplasts is not yet understood. The existence of an energy source in this compartment is discussed, because the required transit peptide length for successful translocation into chloroplasts is shorter than that found for mitochondria where energy is provided exclusively by matrix chaperones. Furthermore, a cytosolic-type Hsp70 homologue was proposed as component of the chloroplast translocon in the intermembrane space energizing the initial translocation. The molecular identity of such intermembrane space localized Hsp70 remained unknown, which led to a controversy concerning its existence. We identified multiple cytosolic Hsp70s by mass spectrometry on isolated, thermolysin-treated Medicago sativa chloroplasts. The localization of these Hsp70s of M. sativa or Arabidopsis thaliana in the intermembrane space was confirmed by a self-assembly GFP-based in vivo system. The localization of cytosolic Hsp70s in the stroma of chloroplasts or different mitochondrial compartments could not be observed. Similarly, we could not identify any cytosolic Hsp90 in the intermembrane space of chloroplast. With respect to our results we discuss the possible targeting and function of the Hsp70 found in the intermembrane space.

The Malarial Exported PFA0660w Is an Hsp40 Co-Chaperone of PfHsp70-x

Plasmodium falciparum, the human pathogen responsible for the most dangerous malaria infection, survives and develops in mature erythrocytes through the export of proteins needed for remodelling of the host cell. Molecular chaperones of the heat shock protein (Hsp) family are prominent members of the exportome, including a number of Hsp40s and a Hsp70. PFA0660w, a type II Hsp40, has been shown to be exported and possibly form a complex with PfHsp70-x in the infected erythrocyte cytosol. However, the chaperone properties of PFA0660w and its interaction with human and parasite Hsp70s are yet to be investigated. Recombinant PFA0660w was found to exist as a monomer in solution, and was able to significantly stimulate the ATPase activity of PfHsp70-x but not that of a second plasmodial Hsp70 (PfHsp70-1) or a human Hsp70 (HSPA1A), indicating a potential specific functional partnership with PfHsp70-x. Protein binding studies in the presence and absence of ATP suggested that the interaction of PFA0660w with PfHsp70-x most likely represented a co-chaperone/chaperone interaction. Also, PFA0660w alone produced a concentration-dependent suppression of rhodanese aggregation, demonstrating its chaperone properties. Overall, we have provided the first biochemical evidence for the possible role of PFA0660w as a chaperone and as co-chaperone of PfHsp70-x. We propose that these chaperones boost the chaperone power of the infected erythrocyte, enabling successful protein trafficking and folding, and thereby making a fundamental contribution to the pathology of malaria.

A Proteomic-Based Workflow Using Purified Respiratory Syncytial Virus Particles to Identify Cellular Factors as Drug Targets

The identification of cellular factors that play a role in respiratory syncytial virus (RSV) replication is an alternative strategy in the identification of druggable cellular protein that are essential for RSV replication. In this regard experimental strategies that are able to screen relevant proteins from the vast array of proteins in the cellular milieu will facilitate the identification of potential drug targets. In this chapter we describe a procedure where RSV particles are purified from cells that are permissive for RSV infection, and the protein composition of the purified virus particles characterized using a proteomics-based strategy. This procedure revealed that actin, several actin-binding proteins, and the chaperones HSP70 and HSP90 also co-purified with the virus particles. The relevance of the HSP90 protein to virus replication was then further validated using imaging, gene silencing and by using an established small molecule HSP90 inhibitor.

Production and preliminary evaluation of Trypanosoma evansi HSP70 for antibody detection in Equids

The present immuno-diagnostic method using soluble antigens from whole cell lysate antigen for trypanosomosis have certain inherent problems like lack of standardized and reproducible antigens, as well as ethical issues due to in vivo production, that could be alleviated by in vitro production. In the present study we have identified heat shock protein 70 (HSP70) from T. evansi proteome. The nucleotide sequence of T. evansi HSP70 was 2116 bp, which encodes 690 amino acid residues. The phylogenetic analysis of T. evansi HSP70 showed that T. evansi occurred within Trypanosoma clade and is most closely related to T. brucei brucei and T. brucei gambiense, whereas T. congolense HSP70 laid in separate clade. The two partial HSP70 sequences (HSP-1 from N-terminal region and HSP-2 from C-terminal region) were expressed and evaluated as diagnostic antigens using experimentally infected equine serum samples. Both recombinant proteins detected antibody in immunoblot using serum samples from experimental infected donkeys with T. evansi. Recombinant HSP-2 showed comparable antibody response to Whole cell lysate (WCL) antigen in immunoblot and ELISA. The initial results indicated that HSP70 has potential to detect the T. evansi infection and needs further validation on large set of equine serum samples.

Identification of Arsenic Direct-Binding Proteins in Acute Promyelocytic Leukaemia Cells

The identification of arsenic direct-binding proteins is essential for determining the mechanism by which arsenic trioxide achieves its chemotherapeutic effects. At least two cysteines close together in the amino acid sequence are crucial to the binding of arsenic and essential to the identification of arsenic-binding proteins. In the present study, arsenic binding proteins were pulled down with streptavidin and identified using a liquid chromatograph-mass spectrometer (LC-MS/MS). More than 40 arsenic-binding proteins were separated, and redox-related proteins, glutathione S-transferase P1 (GSTP1), heat shock 70 kDa protein 9 (HSPA9) and pyruvate kinase M2 (PKM2), were further studied using binding assays in vitro. Notably, PKM2 has a high affinity for arsenic. In contrast to PKM2, GSTP1and HSPA9 did not combine with arsenic directly in vitro. These observations suggest that arsenic-mediated acute promyelocytic leukaemia (APL) suppressive effects involve PKM2. In summary, we identified several arsenic binding proteins in APL cells and investigated the therapeutic mechanisms of arsenic trioxide for APL. Further investigation into specific signal pathways by which PKM2 mediates APL developments may lead to a better understanding of arsenic effects on APL.

Overexpression, Purification and Characterisation of the Plasmodium falciparum Hsp70-z (PfHsp70-z) Protein

Six Hsp70-like genes are represented on the genome of Plasmodium falciparum. Of these two occur in the cytosol: P. falciparum Hsp70-z (PfHsp70-z) and PfHsp70-1. PfHsp70-1 is a well characterised canonical Hsp70 that facilitates protein quality control and is crucial for the development of malaria parasites. There is very little known about PfHsp70-z. However, PfHsp70-z is known to be essential and is implicated in suppressing aggregation of asparagine-rich proteins of P. falciparum. In addition, its expression at the clinical stage of malaria correlates with disease prognosis. Based on structural evidence PfHsp70-z belongs to the Hsp110 family of proteins. Since Hsp110 proteins have been described as nucleotide exchange factors (NEFs) of their canonical Hsp70 counterparts, it has been speculated that PfHsp70-z may serve as a NEF of PfHsp70-1. In the current study, P. falciparum cells cultured in vitro were subjected to heat stress, triggering the enhanced expression of PfHsp70-z. Biochemical assays conducted using recombinant PfHsp70-z protein demonstrated that the protein is heat stable and possesses ATPase activity. Furthermore, we observed that PfHsp70-z is capable of self-association. The structural-functional features of PfHsp70-z provide further evidence for its role as a chaperone and possible nucleotide exchange factor of PfHsp70-1.

Affinity purification probes of potential use to investigate the endogenous Hsp70 interactome in cancer

Heat shock protein 70 (Hsp70) is a family of proteins with key roles in regulating malignancy. Cancer cells rely on Hsp70 to inhibit apoptosis, regulate senescence and autophagy, and maintain the stability of numerous onco-proteins. Despite these important biological functions in cancer, robust chemical tools that enable the analysis of the Hsp70-regulated proteome in a tumor-by-tumor manner are yet unavailable. Here we take advantage of a recently reported Hsp70 ligand to design and develop an affinity purification chemical toolset for potential use in the investigation of the endogenous Hsp70-interacting proteome in cancer. We demonstrate that these tools lock Hsp70 in complex with onco-client proteins and effectively isolate Hsp70 complexes for identification through biochemical techniques. Using these tools we provide proof-of-concept analyses that glimpse into the complex roles played by Hsp70 in maintaining a multitude of cell-specific malignancy-driving proteins.

Isolation and amplification of mRNA within a simple microfluidic lab on a chip

The major modules for realizing molecular biological assays in a micro-total analysis system (μTAS) were developed for the detection of pathogenic organisms. The specific focus was the isolation and amplification of eukaryotic mRNA within a simple, single-channel device for very low RNA concentrations that could then be integrated with detection modules. The hsp70 mRNA from Cryptosporidium parvum was used as a model analyte. Important points of study were surface chemistries within poly(methyl methacrylate) (PMMA) microfluidic channels that enabled specific and sensitive mRNA isolation and amplification reactions for very low mRNA concentrations. Optimal conditions were achieved when the channel surface was carboxylated via UV/ozone treatment followed by the immobilization of polyamidoamine (PAMAM) dendrimers on the surface, thus increasing the immobilization efficiency of the thymidine oligonucleotide, oligo(dT)25, and providing a reliable surface for the amplification reaction, importantly, without the need for blocking agents. Additional chemical modifications of the remaining active surface groups were studied to avoid nonspecific capturing of nucleic acids and hindering of the mRNA amplification at low RNA concentrations. Amplification of the mRNA was accomplished using nucleic acid sequence-based amplification (NASBA), an isothermal, primer-dependent technique. Positive controls consisting of previously generated NASBA amplicons could be diluted 10(15) fold and still result in successful on-chip reamplification. Finally, the successful isolation and amplification of mRNA from as few as 30 C. parvum oocysts was demonstrated directly on-chip and compared to benchtop devices. This is the first proof of successful mRNA isolation and NASBA-based amplification of mRNA within a simple microfluidic device in relevant analytical volumes.

[Stress proteins in the cells of Porphyra purpurea (Rhodophyta) thallus]

Heat shock proteins have been revealed for the first time by the methods of Western blotting using alkaline phosphatase and ECL in the cells of Porphyra purpurea from Kattegat area of the Baltic Sea in normal and experimental stress conditions. It was demonstrated with application of monoclonal anti-Hsp70 antibodies that a slight band about 70 kDa is present constitutively at the film; additionally the polypeptide of about 40 kDa ("Hsp40") has been detected. After heat shock at 28 degrees C during 1 hr significant "expenditure" of Hsp70 was observed, as well as the pronounced induction of "Hsp40"; the induction was expressed especially strongly in 24 hr after the stress application.

Identification of an exported heat shock protein 70 in Plasmodium falciparum

Host cell remodelling is a hallmark of malaria pathogenesis. It involves protein folding, unfolding and trafficking events and thus participation of chaperones such as Hsp70s and Hsp40s is well speculated. Until recently, only Hsp40s were thought to be the sole representative of the parasite chaperones in the exportome. However, based on the re-annotated Plasmodium falciparum genome sequence, a putative candidate for exported Hsp70 has been reported, which otherwise was known to be a pseudogene. We raised a specific antiserum against a C-terminal peptide uniquely present in PfHsp70-x. Immunoblotting and immunofluorescence-based approaches in combination with sub-cellular fractionation by saponin and streptolysin-O have been taken to determine the expression and localization of PfHsp70-x in infected erythrocyte. The re-annotated sequence of PfHsp70-x reveals it to be a functional protein with an endoplasmic reticulum signal peptide. It gets maximally expressed at the schizont stage of intra-erythrocytic life cycle. Majority of the protein localizes to the parasitophorous vacuole and some of it gets exported to the erythrocyte compartment where it associates with Maurer's clefts. The identification of an exported parasite Hsp70 chaperone presents us with the fact that the parasite has evolved customized chaperones which might be playing crucial roles in aspects of trafficking and host cell remodelling.

[Changes of heat shock proteins content in the gill epithelium cells of mussel Mytilus edulis L. depending upon the salinity of medium]

The composition and the level of heat shock (stress) proteins content were studied by the method of immunobloting in the gill epithelium cells of mussels Mytilus edulis L. from the White sea, treated by water of different salinities. Stress proteins of about 70 and 40 kDa were revealed at Western blots. After long-term (11-14 days) acclimation to 14 and 35 per thousand the level of Hsp70 in gill epithelium cells increased to compare with that in control mussels. Hsp70 induction was observed in the cells of isolated gills after salinity shock at 14 per thousand during 3 and 24 hours.

Reactivation of protein aggregates by mortalin and Tid1--the human mitochondrial Hsp70 chaperone system

The mitochondrial 70-kDa heat shock protein (mtHsp70), also known in humans as mortalin, is a central component of the mitochondrial protein import motor and plays a key role in the folding of matrix-localized mitochondrial proteins. MtHsp70 is assisted by a member of the 40-kDa heat shock protein co-chaperone family named Tid1 and a nucleotide exchange factor. Whereas, yeast mtHsp70 has been extensively studied in the context of protein import in the mitochondria, and the bacterial 70-kDa heat shock protein was recently shown to act as an ATP-fuelled unfolding enzyme capable of detoxifying stably misfolded polypeptides into harmless natively refolded proteins, little is known about the molecular functions of the human mortalin in protein homeostasis. Here, we developed novel and efficient purification protocols for mortalin and the two spliced versions of Tid1, Tid1-S, and Tid1-L and showed that mortalin can mediate the in vitro ATP-dependent reactivation of stable-preformed heat-denatured model aggregates, with the assistance of Mge1 and either Tid1-L or Tid1-S co-chaperones or yeast Mdj1. Thus, in addition of being a central component of the protein import machinery, human mortalin together with Tid1, may serve as a protein disaggregating machine which, for lack of Hsp100/ClpB disaggregating co-chaperones, may carry alone the scavenging of toxic protein aggregates in stressed, diseased, or aging human mitochondria.

[Characterization of recombinant human HSP70's domains functions and interdomain interactions]

We investigated ATP-ase and peptide-binding activity of recombinant human heat shock protein HSP70(A1B), HSC70, and two hybrid proteins derived from those. The UV-spectral recorded data was used to characterize conformational rearrangements, which were induced by domain replacement or HSP70-peptide interaction. We have shown that N-terminal domain dramatically affect substrate specificity of C-terminal peptide-binding domain. This proposes new hypothesis for HSP70 chaperone machinery. The linear dependence between ATP-ase activity and peptide complex ratio was found. This relationship could be used for unlabeled peptide-HSP70 complex quantification.

Reconstitution of the mitochondrial Hsp70 (mortalin)-p53 interaction using purified proteins--identification of additional interacting regions

Previous studies have shown that the mammalian mitochondrial 70 kDa heat-shock protein (mortalin) can also be detected in the cytosol. Cytosolic mortalin binds p53 and by doing so, prevents translocation of the tumor suppressor into the nucleus. In this study, we developed a novel binding assay, using purified proteins, for tracking the interaction between p53 and mortalin. Our results reveal that: (i) P53 binds to the peptide-binding site of mortalin which enhances the ability of the former to bind DNA. (ii) An additional previously unknown binding site for mortalin exists within the C-terminal domain of p53.

Novel modification of growth medium enables efficient E. coli expression and simple purification of an endotoxin-free recombinant murine hsp70 protein

Heat shock protein 70 kDa (hsp70), a molecular chaperone involved in folding of nascent proteins, has been studied for its ability to activate innate and specific immunity. High purity hsp70 preparation is generally required for immunization experiments, because endotoxins and other immunologically active contaminants may affect immune responses independently of hsp70. We have developed a novel modification of E. coli-expression medium that enabled a simple two-step production and purification method for endotoxin-free recombinant hsp70. During Ni-NTA-based affinity purification of hsp70, a contaminating protein from host E. coli cells, L-glutamine-D-fructose-6-phosphate aminotransferase (GFAT), was identified. By testing various compounds, supplementation of growth medium with a GFAT metabolite, N-acetylglucosamine, was found to reduce GFAT expression and increase the total hsp70 yield five times. The new protocol is based on column purification of His-tagged hsp70 protein produced by E. coli with the modified medium, followed by endotoxin removal by Triton X-114 extraction. This approach yielded hsp70 with high purity and minimal endotoxin contamination, making the final product acceptable for immunization experiments. In summary, a simple modification of growth medium allowed production of recombinant mouse hsp70 in high yield and purity, thus compatible with immunological studies. This protocol may be useful for production of other His.

Identification of candidate prostate cancer biomarkers in prostate needle biopsy specimens using proteomic analysis

Although serum prostate specific antigen (PSA) is a well-established diagnostic tool for prostate cancer (PCa) detection, the definitive diagnosis of PCa is based on the information contained in prostate needle biopsy (PNBX) specimens. To define the proteomic features of PNBX specimens to identify candidate biomarkers for PCa, PNBX specimens from patients with PCa or benign prostatic hyperplasia (BPH) were subjected to comparative proteomic analysis. 2-DE revealed that 52 protein spots exhibited statistically significantly changes among PCa and BPH groups. Interesting spots were identified by MALDI-TOF-MS/MS. The 2 most notable groups of proteins identified included latent androgen receptor coregulators [FLNA(7-15) and FKBP4] and enzymes involved in mitochondrial fatty acid beta-oxidation (DCI and ECHS1). An imbalance in the expression of peroxiredoxin subtypes was noted in PCa specimens. Furthermore, different post-translationally modified isoforms of HSP27 and HSP70.1 were identified. Importantly, changes in FLNA(7-15), FKBP4, and PRDX4 expression were confirmed by immunoblot analyses. Our results suggest that a proteomics-based approach is useful for developing a more complete picture of the protein profile of PNBX specimen. The proteins identified by this approach may be useful molecular targets for PCa diagnostics and therapeutics.

The interplay between components of the mitochondrial protein translocation motor studied using purified components

The final step of protein translocation across the mitochondrial inner membrane is mediated by a translocation motor composed of 1) the matrix-localized, ATP-hydrolyzing, 70-kDa heat shock protein mHsp70; 2) its anchor to the import channel, Tim44; 3) the nucleotide exchange factor Mge1; and 4) a J-domain-containing complex of co-chaperones, Tim14/Pam18-Tim16/Pam16. Despite its essential role in the biogenesis of mitochondria, the mechanism by which the translocation motor functions is still largely unknown. The goal of this work was to carry out a structure-function analysis of the mitochondrial translocation motor utilizing purified components, with an emphasis on the formation of the Tim44-mHsp70 complex. To this end, we purified Tim44 and monitored its interaction with other components of the motor using cross-linking with bifunctional reagents. The effects of nucleotides, the J-domain-containing components, and the P5 peptide (CALLSAPRR, representing part of the mitochondrial targeting signal of aspartate aminotransferase) on the formation of the translocation motor were examined. Our results show that only the peptide and nucleotides, but not J-domain-containing proteins, affect the Tim44-mHsp70 interaction. Additionally, binding of Tim44 to mHsp70 prevents the formation of a complex between the latter and Tim14/Pam18-Tim16/Pam16. Thus, mutually exclusive interactions between various components of the motor with mHsp70 regulate its functional cycle. The results are discussed in light of known models for the function of the mitochondrial translocation motor.

Leishmania major heat shock protein 70 (HSP70) is not protective in murine models of cutaneous leishmaniasis and stimulates strong humoral responses in cutaneous and visceral leishmaniasis patients

Heat shock proteins (HSP) are highly conserved molecules that play important roles in protein folding, assembly of protein complexes and translocation of proteins across cellular compartments, as well as in several immunological processes. In this study, we first immunized susceptible BALB/c and resistant C57BL/6 mice with the complete open-reading frame of Leishmania HSP-70 (pcDNA-HSP70) and boosted mice with rHSP-70 (amino acid 221-604 cloned in pQE-HSP70 and referred to as rHSP70) mixed with Montanide 720. When we evaluated the effects of HSP70 in both mouse strains, we found that the entire fragment (amino acids 221-604) and rCT-HSP70 (amino acids 491-604 cloned in pQE-CT), but not rNT-HSP70 (amino acids 221-291 cloned pQE-NT), contained the highest immunogenicity. However, after infectious challenge with Leishmania major, no efficient protective responses were observed in either mouse strain. The humoral immune responses against the different truncated forms of HSP70 suggested a mixed TH1/TH2 response in vivo. We then assessed infected susceptible and resistant mice for lymphoproliferative and cytokine responses against the truncated forms of HSP70. At 9-week post-infection, we observed no differences in those responses between vaccinated and control mice. Next, we initiated comparative studies in human patient samples, finding no significant proliferation against all three truncated forms of HSP70 in the cellular immune responses of 16 cured cutaneous leishmaniasis patients and 5 normal individuals. Sera from active cutaneous and visceral leishmaniasis patients, however, were reactive to all three forms of HSP70. This study demonstrates the potential of HSP70 in stimulating humoral responses in humans and mice and indicates there is a need to further explore and examine the value of this important molecule in the control of leishmaniasis.

ATP-independent thermoprotective activity of Nicotiana tabacum heat shock protein 70 in Escherichia coli

To study the functioning of HSP70 in Escherichia coli, we selected NtHSP70-2 (AY372070) from among three genomic clones isolated in Nicotiana tabacum. Recombinant NtHSP70-2, containing a hexahistidine tag at the amino-terminus, was constructed, expressed in E. coli, and purified by Ni(2+) affinity chromatography and Q Sepharose Fast Flow anion exchange chromatography. The expressed fusion protein, H(6)NtHSP70-2 (hexahistidine-tagged Nicotiana tabacum heat shock protein 70-2), maintained the stability of E. coli proteins up to 90 degrees C. Measuring the light scattering of luciferase (luc) revealed that NtHSP70-2 prevents the aggregation of luc without ATP during high-temperature stress. In a functional bioassay (1 h at 50 degrees C) for recombinant H(6)NtHSP70-2, E. coli cells overexpressing H(6)NtHSP70-2 survived about seven times longer than those lacking H(6)NtHSP70-2. After 2 h at 50 degrees C, only the E. coli overexpressing H(6)NtHSP70-2 survived under such conditions. Our NtHSP70-2 bioassays, as well as in vitro studies, strongly suggest that HSP70 confers thermo-tolerance to E. coli.

[Expression of stress proteins of family HSP70 in response to cold in Myrmica ants from different geographic populations]

Expression of HSP70 is induced by stress factors, including sub-lethal chilling, but the role of HSP70 for overcoming consequenses of cold stress is not clear. If the role is positive, the level of HSP70 expression might be higher in populations from colder climates. By use of immunoblotting we investigated dynamics of HSP70 expression in response to cold stress in two Myrmica species from three localities of different latitude (50, 60 and 67 degrees N). The results showed that in the more thermophilic species Myrmica rubra expression of HSP70 after cold stress was more intense. Expression traits within both species did not show direct relationship with latitude. In M. rubra the southernmost population and in M. ruginodis the northernmost one displayed the fastest and most intense response. However, in M. rubra the two other studied populations were similar in timing and intensity of the response, while in M. ruginodis the intermediate population showed the slowest and weakest response. The data suggest that the expression of HSP70 might play the most considerable role in the adaptation to cold in the southernmost population of M. ruginodis.

Enhanced immunogenicity of heat shock protein 70 peptide complexes from dendritic cell-tumor fusion cells

We have developed a molecular chaperone-based tumor vaccine that reverses the immune tolerance of cancer cells. Heat shock protein (HSP) 70 extracted from fusions of dendritic (DC) and tumor cells (HSP70.PC-F) possess superior properties such as stimulation of DC maturation and T cell proliferation over its counterpart from tumor cells. More importantly, immunization of mice with HSP70.PC-F resulted in a T cell-mediated immune response including significant increase of CD8 T cells and induction of the effector and memory T cells that was able to break T cell unresponsiveness to a nonmutated tumor Ag and provide protection of mice against challenge with tumor cells. By contrast, the immune response to vaccination with HSP70-PC derived from tumor cells is muted against such nonmutated tumor Ag. HSP70.PC-F complexes differed from those derived from tumor cells in a number of key manners, most notably, enhanced association with immunologic peptides. In addition, the molecular chaperone HSP90 was found to be associated with HSP70.PC-F as indicated by coimmunoprecipitation, suggesting ability to carry an increased repertoire of antigenic peptides by the two chaperones. Significantly, activation of DC by HSP70.PC-F was dependent on the presence of an intact MyD88 gene, suggesting a role for TLR signaling in DC activation and T cell stimulation. These experiments indicate that HSP70-peptide complexes (PC) derived from DC-tumor fusion cells have increased their immunogenicity and therefore constitute an improved formulation of chaperone protein-based tumor vaccine.

[Construction and expression of HSV-2gD-Hsp70 fusion protein gene]

To construct and express Hsp70-HSV2gD fusion protein. Genes of Hsp70 and HSV-2gD were subcloned into vectors pGEX-4T-1 respectively. After confirmed by DNA sequence analysis, the recombinant plasmids pGEX-4T-HSP-gD was transformed into E. coli DH5alpha and induced to express with IPTG. The expressed protein was characterized by SDS-PAGE and Western blot after purified. BALB/c mice were immunized with fusion proteins respectively via intra-m uscular injection. The proliferation of spleen lymphocytes, the level of y-IFN in culture and anti-HSV-2gD IgG antibody in serum was detected was detected. The expressed protein was analyzed by SDS-PAGE after induced with IPTG, which showed a new band with an apparent molecular mass corresponding to the predicted size (118 kD). Western Blotting analysis demonstrates that the purified Hsp70-HSV2gD fusion protein had specific binding activity. The stimulation indexes of spleen lymphocytes, the level of gamma-IFN in culture and anti-HSV-2gD IgG antibody in serum of GST-Hsp70-gD group was obviously higher than that of other groups (P < 0.05 respectively). The successful expression of the Hsp70-HSV2gD fusion protein, which can induce immune responses, laid a solid foundation for its further research.

First hsp70 from two hydrothermal vent shrimps, Mirocaris fortunata and Rimicaris exoculata: characterization and sequence analysis

The vent shrimps, Mirocaris fortunata and Rimicaris exoculata, live in a highly fluctuating thermal environment and undergo frequent temperature bursts. As a first step in the investigation of the response to heat stress, this work aimed to characterize stress proteins in these two species. Complementary deoxyribonucleic acid (cDNA) clones encoding a 70-kDa heat shock protein (HSP) were isolated and characterized from M. fortunata and R. exoculata. The cDNA clones were of 2055 and 1941 base pairs in length, and contained a 2018-bp complete open reading frame (ORF) and a 1785-bp partial coding sequence, respectively. The amino acid sequences corresponding to these ORF are 645 residues in length for M. fortunata and 595 for R. exoculata, and were clearly characterized as members of the HSP70 family. The C-terminal extremity would identify R. exoculata sequence as a cytoplasm HSP70. The relationships between the crustacean HSP70 sequences were examined by two phylogenetic methods, i.e. Maximum Likelihood and Bayesian methods. The resulting trees suggested that M. fortunata sequence may correspond to constitutively expressed HSP70, named HSC70, whereas R. exoculata sequence may correspond to an inducible form of HSP70. The HSP70 sequences from the hydrothermal shrimps proved to be very similar to the other homologous shrimp sequences, except for the presence of an insertion of unknown function in the ATPase domain of R. exoculata sequence.

Extracellular targeting of endoplasmic reticulum chaperone glucose-regulated protein 170 enhances tumor immunity to a poorly immunogenic melanoma

We have demonstrated previously that immunization with tumor-derived endoplasmic reticulum (ER) chaperone glucose-regulated protein 170 (grp170) elicits potent antitumor immunity. In the present study, we determine the impact of extracellular targeting grp170 by molecular engineering on tumor immunogenicity and potential use of grp170-secreting tumor cells as a cancer vaccine. grp170 depleted of ER retention sequence "KNDEL," when secreted by B16 tumor cells, maintained its highly efficient chaperoning activities and was significantly superior to both hsp70 and gp96. The continued secretion of grp170 dramatically reduced the tumorigenicity of B16 tumor cells in vivo, although the modification did not alter its transformation phenotype and cell growth rate. C57BL/6 mice that rejected grp170-secreting B16 tumor cells (B16-sgrp170) developed a strong CTL response recognizing melanocyte differentiation Ag TRP2 and were resistant to subsequent tumor challenge. B16-sgrp170 cells also stimulated the production of proinflammatory cytokines by cocultured dendritic cells. Depletion studies in vivo indicate that NK cells play a primary role in elimination of viable B16-sgrp170 tumor cells inoculated into the animals, whereas both NK cells and CD8(+) T cells are required for a long-term protection against wild-type B16 tumor challenge. Both the secreted and endogenous grp170, when purified from the B16 tumor, exhibited potent tumor-protective activities. However, the B16-sgrp170 cell appears to be more effective than tumor-derived grp170. Thus, molecular engineering of tumor cell to release the largest ER chaperone grp170 is capable of eliciting innate as well as adaptive immune responses, which may provide an effective cell-based vaccination approach for cancer immunotherapy.

Crystallization and X-ray data analysis of the 10 kDa C-terminal lid subdomain from Caenorhabditis elegans Hsp70

Hsp70 is an important molecular chaperone involved in the regulation of protein folding. Crystals of the C-terminal 10 kDa helical lid domain (residues 542-640) from a Caenorhabditis elegans Hsp70 homologue have been produced that diffract X-rays to approximately 3.4 A. Crystals belong to space group I2(1)2(1)2(1), with unit-cell parameters a = b = 197, c = 200 A. The Matthews coefficient, self-rotation function and Patterson map indicate 24 monomers in the asymmetric unit, showing non-crystallographic 432 symmetry. Molecular-replacement studies using the corresponding domain from rat, the only eukaryotic homologue with a known structure, failed and a mercury derivative was obtained. Preliminary MAD phasing using SHELXD and SHARP for location and refinement of the heavy-atom substructure and SOLOMON for density modification produced interpretable maps with a clear protein-solvent boundary. Further density-modification, model-building and refinement are currently under way.

One-step purification of bacterially expressed recombinant transducin alpha-subunit and isotopically labeled PDE6 gamma-subunit for NMR analysis

Interactions between the transducin alpha-subunit (Galpha(t)) and the cGMP phosphodiesterase gamma-subunit (PDEgamma) are critical not only for turn-on but also turn-off of vertebrate visual signal transduction. Elucidation of the signaling mechanisms dominated by these interactions has been restrained by the lack of atomic structures for full-length Galpha(t)/PDEgamma complexes, in particular, the signaling-state complex represented by Galpha(t).GTPgammaS/PDEgamma. As a preliminary step in our effort for NMR structural analysis of Galpha(t)/PDEgamma interactions, we have developed efficient protocols for the large-scale production of recombinant Galpha(t) (rGalpha(t)) and homogeneous and functional isotopically labeled PDEgamma from Escherichia coli cells. One-step purification of rGalpha(t) was achieved through cobalt affinity chromatography in the presence of glycerol, which effectively removed the molecular chaperone DnaK that otherwise persistently co-purified with rGalpha(t). The purified rGalpha(t) was found to be functional in GTPgammaS/GDP exchange upon activation of rhodopsin and was used to form a signaling-state complex with labeled PDEgamma, rGalpha(t). GTPgammaS/[U-13C,15N]PDEgamma. The labeled PDEgamma sample yielded a well-resolved 1H-15N HSQC spectrum. The methods described here for large-scale production of homogeneous and functional rGalpha(t) and isotope-labeled PDEgamma should support further NMR structural analysis of the rGalpha(t)/PDEgamma complexes. In addition, our protocol for removing the co-purifying DnaK contaminant may be of general utility in purifying E. coli-expressed recombinant proteins.

Association of MBP peptides with Hsp70 in normal appearing human white matter

Multiple Sclerosis is an autoimmune disease directed against myelin proteins. The etiology of MS is poorly defined though, with no definitive causative agent yet identified. It has been hypothesized that MS may be a multifactorial disease resulting in the same end product: the destruction of myelin by the immune system. In this report we describe a potential role for heat shock proteins in the pathogenesis of MS. We isolated Hsp70 from the normal appearing white matter of both MS and normal human brain and found this was actively associated with, among other things, immunodominant MBP peptides. Hsp70-MBP peptide complexes prepared in vitro were shown to be highly immunogenic, with adjuvant-like effects stimulating MBP peptide-specific T cell lines to respond to normally sub-optimal concentrations of peptide. This demonstration of a specific interaction between Hsp70 and different MBP peptides, coupled with the adjuvanticity of this association is suggestive of a possible role for Hsp70 in the immunopathology associated with MS.

Structure and function of Hsp78, the mitochondrial ClpB homolog

The cellular role of Hsp100/Clp chaperones in maintaining protein stability is based on two functional aspects. Under normal growth conditions they represent components of cellular protein quality control machineries that selectively remove damaged or misfolded polypeptides in cooperation with specific proteases. After thermal stress, proteins of the ClpB subfamily have the unique ability to directly resolubilize aggregated polypeptides in concert with Hsp70-type chaperones, leading to the recovery of enzymatic activity. Hsp78, the homolog of the bacterial chaperone ClpB in mitochondria of eukaryotic organisms, participates in both protective activities. Hsp78 is involved in conferring thermotolerance to the mitochondrial compartment but also participates in protein degradation by the matrix protease Pim1. Despite the high sequence conservation between Hsp78 and ClpB, an analysis of the structural properties revealed significant differences. The identified mitochondrial Hsp78s do not contain N-terminal substrate-binding domains. In addition, formation of the oligomeric chaperone complex was more variable as anticipated from the studies with bacterial ClpB. Hsp78 predominantly formed a trimeric complex under in vivo conditions. Hence, mitochondrial Hsp78s form a distinct subgroup of the ClpB chaperone family, exhibiting specific structural and functional properties.

Characterisation and expression of an Hsp70 gene from Parastrongyloides trichosuri

Parastrongyloides trichosuri is a nematode parasite of Australian brushtail possums that has an alternative free-living life cycle which can be readily maintained indefinitely in a laboratory setting. The ability to maintain this parasite in a free-living cycle and induce it to parasitism at the free-living L1 stage makes this an excellent model for the study of genes associated with parasitism. A 70kD protein from infective larvae of P. trichosuri that appears to be immunogenic in infected possums has been identified as a heat shock protein (Hsp)70 homologue. The complete gene for Pt-Hsp70 was cloned and sequenced. The protein encoded by the Pt-Hsp70 gene is the likely orthologue of the Caenorhabditis elegans protein, Hsp70A, also known as hsp-1. Reverse transcriptase-PCR data indicate that Pt-Hsp70 (designated Pt-hsp-1) is expressed at readily detectable levels in all developmental stages of both the parasitic and free-living P. trichosuri life cycles and the promoter is mildly inducible by heat shock. Bioinformatic analysis of expressed sequence tag databases indicates that C. eleganshsp-1 homologues, together with C. eleganshsp-3 homologues, are the predominant members of the Hsp70 superfamily that are normally expressed in parasitic stages of the Strongyloididae family. Promoter fusions to a beta-galactosidase coding sequence were prepared and introduced into wild type C. elegans to produce transgenic nematodes. Reporter gene expression was clearly present within embryonic cells and within intestinal cells of larval and adult stages. Thus, the expression of the Pt-hsp-1 promoter within P. trichosuri and transgenic C. elegans appears similar to the known expression of C. elegans hsp-1. This promoter should be of value in efforts to develop genetic manipulation tools for P. trichosuri.

Proteomic identification of a stress protein, mortalin/mthsp70/GRP75: relevance to Parkinson disease

Functional impairment of mitochondria and proteasomes and increased oxidative damage comprise the main pathological phenotypes of Parkinson disease (PD). Using an unbiased quantitative proteomic approach, we compared nigral mitochondrial proteins of PD patients with those from age-matched controls. 119 of 842 identified proteins displayed significant differences in their relative abundance (increase/decrease) between the two groups. We confirmed that one of these, mortalin (mthsp70/GRP75, a mitochondrial stress protein), is substantially decreased in PD brains as well as in a cellular model of PD. In addition, nine candidate mortalin-binding partners were identified as potential mediators of PD pathology. Manipulations of mortalin level in dopaminergic neurons resulted in significant changes in sensitivity to PD phenotypes via pathways involving mitochondrial and proteasomal function as well as oxidative stress.

Brain-derived heat shock protein 70-peptide complexes induce NK cell-dependent tolerance to experimental autoimmune encephalomyelitis

Heat shock proteins (Hsp) are markedly up-regulated at sites of inflammation during autoimmune diseases like experimental autoimmune encephalomyelitis (EAE). In this study, we show that Hsp70-peptide complexes (pc) isolated from brains of mice with EAE prevented the development of EAE clinically and pathologically when administered before proteolipid protein 139-151 (PLP139-151) immunization. In contrast, pure Hsp70 or Hsp70-pc derived from brains of healthy mice or other inflamed tissue did not modulate the expression of EAE. In animals in which EAE had been suppressed by Hsp70-pc, lymphocytes showed increased cell death in response to PLP139-151 that correlated with elevated IFN-gamma and NO production. Coculture of spleen cells from Hsp70-pc immunized mice with spleen cells from untreated EAE mice, in addition to depletion experiments, showed that NK cells reduced reactivity to PLP139-151. Transfer of NK cells from Hsp70-pc-immunized mice to recipients sensitized for EAE abolished disease development. Thus, we propose that Hsp70 demonstrate the ability to bind to peptides generated during brain inflammation and to induce a regulatory NK cell population that is capable of preventing subsequent autoimmunization for EAE.

Proteomics analysis of the tombusvirus replicase: Hsp70 molecular chaperone is associated with the replicase and enhances viral RNA replication

Plus-strand RNA virus replication occurs via the assembly of viral replicase complexes involving multiple viral and host proteins. To identify host proteins present in the cucumber necrosis tombusvirus (CNV) replicase, we affinity purified functional viral replicase complexes from yeast. Mass spectrometry analysis of proteins resolved by two-dimensional gel electrophoresis revealed the presence of CNV p33 and p92 replicase proteins as well as four major host proteins in the CNV replicase. The host proteins included the Ssa1/2p molecular chaperones (yeast homologues of Hsp70 proteins), Tdh2/3p (glyceraldehyde-3-phosphate dehydrogenase, an RNA-binding protein), Pdc1p (pyruvate decarboxylase), and an unknown approximately 35-kDa acidic protein. Copurification experiments demonstrated that Ssa1p bound to p33 replication protein in vivo, and surface plasmon resonance measurements with purified recombinant proteins confirmed this interaction in vitro. The double mutant strain (ssa1 ssa2) showed 75% reduction in viral RNA accumulation, whereas overexpression of either Ssa1p or Ssa2p stimulated viral RNA replication by approximately threefold. The activity of the purified CNV replicase correlated with viral RNA replication in the above-mentioned ssa1 ssa2 mutant and in the Ssa overexpression strains, suggesting that Ssa1/2p likely plays an important role in the assembly of the CNV replicase.

Novel vaccines for the treatment of chronic HBV infection based on mycobacterial heat shock protein 70

Immunogenic peptide-based vaccines can raise significant cellular immune responses. Although cytotoxic T lymphocytes (CTL) peptide epitopes are generally poor immunogens, heat shock protein 70 from Mycobacterium tuberculosis (TBhsp70) can overcome this problem since it is a potent adjuvant that links innate and adaptive immune responses. Our goal is to use TBhsp70 as an adjuvant for development of therapeutic vaccines for chronic Hepatitis B virus infection (HBV). To this end, we genetically fused the HBV core 18-27 peptide (HBcAg((18-27))) as a CTL epitope to the C-terminus of TBhsp70 and expressed the resulting protein in methylotropic yeast Pichia pastoris GS115. At the same time, the TBhsp70-HBcAg((18-27)) peptide complex was reconstituted in vitro. We investigated whether TBhsp70-peptide complex and TBhsp70-peptide fusion protein could generate antigen specific CTL responses in vitro. Dendritic cells (DC) from HLA-A2(+) chronic HBV infection and healthy control pulsed with two vaccines were studied phenotypically by FACS analyses and functionally by cytokine release, and HBV-specific CTL response. Our results demonstrate that two vaccines can activate DC of chronic HBV infection and healthy control by upregulation CD40 and CD86, high production of IL-12p70 and TNF-alpha. Furthermore, autologous T cells with DC stimulated by two vaccines can produce IFN-gamma and generate HBV-specific CTL response. However, capacity for CTL response and cytokines production from HBV infections remained inferior to that of healthy controls. Thus, the strategy of utilizing TBhsp70 may provide a novel design for the development of prophylactic and therapeutic vaccines.

[Heat shock protein of HSP70 family revealed in some contemporary freshwater Amoebae and in Acanthamoeba sp. from cysts isolated from permafrost samples]

A heat shock protein of HSP70 family was revealed for the first time in trophozoites of Acanthamoeba sp. (strain Am8) excysted from cysts previously isolated from samples of permafrost aging 30,000-35,000 years. The constitutive level of this HSP, shown by immunnoblotting in unstressed trophozoites of the ancient acanthamoebae, much surpassed that in unstressed cells of the three examined species of contemporary freshwater amebae of the genus Amoeba.

Protein extraction from activated sludge

Two methods for the separation of protein originating from activated sludge were compared. In one method, the total protein was isolated out of the activated sludge (crude extract). These samples included all dissolved proteins originating from the bacterial cells and biofilm made up of extracellular polymeric substances (EPS). Every time polyacrylamide gel electrophoresis (PAGE) was done, the protein bands from samples of crude extract were covered by polymeric substances including carbohydrates, uronic acids or humic compounds. Using the immunoblot technique it was possible to demonstrate the presence of the heat shock protein HSP70 in crude extracts of activated sludge. The comparison of protein fingerprints required that clear and distinct bands appear on the PAGE analysis. To this end, a procedure to separates bacterial cells from the EPS was developed. Bacterial cells were separated by incubation with EDTA and subsequent filtration. The isolated cells were directly incubated in a sample buffer.

Protective role of melatonin in cyclosporine A-induced oxidative stress in rat liver

Cyclosporine A (CsA) is the most widely used immunosuppressive drug for preventing graft rejection and autoimmune disease. However, the therapeutic treatment induces several side effects such as nephrotoxicity, cardiotoxicity, hypertension and hepatotoxicity. Among possible mechanisms of CsA-induced hepatic damage, oxidative stress has been suggested. Melatonin (Mel) has been successfully used as a potent antioxidant against many pathophysiological states. This experimental study was performed to test, during CsA treatment, the alterations of some heat shock proteins (HSP) and the Mel antioxidant properties against CsA-induced injury. Rats were divided into four groups, which were treated respectively with olive oil, Mel alone, CsA and CsA plus Mel for 30 days. At the end of the treatments, the animals were killed and hepatic tissue was treated for morphological (haematoxylin-eosin), biochemical (reduced glutathione, GSH and malondialdehyde, MDA) and immunohistochemical (HSP60, HSP72, GRP75 and MT) analyses. The results indicate that CsA-induced hepatotoxicity was characterised by morphological alterations in tissue architecture, changes in GSH and MDA levels and increase in stress protein expression. In conclusion, our data suggest that the imbalance between production of free oxygen radicals and antioxidant defence systems, due to CsA administration, is a mechanism responsible for oxidative stress. Moreover, we show that Mel plays a protective action against CsA-induced oxidative stress, as supported by biochemical and immunohistochemical results.

Dendritic cells pulsed with hsp70-peptide complexes derived from human hepatocellular carcinoma induce specific anti-tumor immune responses

AIM: To investigate the anti-tumor effect of dendritic cells (DCs) pulsed with hsp70-peptide complexes derived from human hepatocellular carcinoma (HCC) cells on human T cells.

METHODS: Hsp70-peptide complexes were purified from human HCC cells with column chromatography using ADP-agarose and DEAE-Sepharose. DCs were derived from peripheral blood mononuclear cells of healthy donors in the presence of human GM-CSF and IL-4. The anti-tumor effect of DCs pulsed with hsp70-peptide complexes on human T-cell was assayed by CTL and enzyme-linked immunospot (ELISPOT) tests.

RESULTS: Hsp70-peptide complexes derived from human HCC cells activated phenotypic and functional maturation of DCs. The matured DCs stimulated a high level of autologous T-cell proliferation and type I cytokine secretion, and induced HCC-specific cytotoxic T lymphocytes (CTLs), which specifically killed HCC cells by a MHC class I restricted mechanism.

CONCLUSION: Hsp70-peptide complexes derived from human HCC cells can serve as a potent tumor antigen source for pulsing DCs, the pulsed DCs are very effective in activating specific T-cell responses against HCC cells.

Heat shock protein 70 chaperoned alpha-fetoprotein in human hepatocellular carcinoma cell line BEL-7402

AIM: To investigate the interaction between heat shock protein 70 (HSP70) and α-fetoprotein (AFP) in human hepatocellular carcinoma (HCC) cell line BEL-7402.

METHODS: The expression and localization of HSP70 and AFP in human HCC cell line BEL-7402 were determined by immunocytochemistry and indirect immunofluorescence cytochemical staining. The interaction between HSP70 and AFP in HCC cells was analyzed by immunoprecipitation and Western blot.

RESULTS: Immunocytochemical staining detection showed that HCC cell BEL-7402 expressed a high level of HSP70 and AFP synchronously. Both were stained in cell plasma. AFP existed in the immunoprecipitate of anti-HSP70 mAb, while there was HSP70 in the immunoprecipitate of anti-AFP mAb.

CONCLUSION: HSP70 chaperones AFP in human HCC cell BEL-7402. The interaction between HSP70 and AFP in human HCC cell can be a new route to study the pathogenesis and immunotherapy of HCC.

Initiation of stress protein synthesis in the myocardium of coronary patients

We studied myocardial biopsy specimens from the right atrium of cardiological patients with different degree of cardiac ischemia obtained during surgery. No inducible HSP70 stress proteins were detected in atrial cardiomyocytes of patients with the WPW syndrome without signs of ischemic injuries of the heart. These proteins were detected in the myocardium of coronary patients. Their expression was more intense in patients with coronary disease paralleled by the development of myocardial dyskinesia. Two-dimensional electrophoresis showed only acid HSP70 but no alkaline isoforms in coronary patients even with pronounced dyskinesia. Presumably, alkaline HSP70 isoforms are present in the myocardium directly involved in the dyskinesia zone.

[Screening tumor antigens of ovarian carcinoma by Western blot, immunoprecipitation, and mass spectrometry]

BACKGROUND & OBJECTIVE

Screening tumor antigens plays a key role in early diagnosis of ovarian carcinoma. Several technologies, such as phage antibody library, ribosome display, and serological analysis of recombinant cDNA expression libraries (SEREX), have been applied widely. This study was to screen and identify tumor antigens of ovarian carcinoma by Western blot, immunoprecipitation, and mass spectrometry, and to establish a new methodological entity.

METHODS

Western blot was used to find out the obviously different serum in ovarian carcinoma patients; SKOV3 cells lysate was added in the serum; immunoprecipitation was used to enrich antigens; then, the different protein band was gained when compared with normal serum immunoprecipitates, identified by mass spectrometry, and analyzed with bioinformatics.

RESULTS

The serum of patient No. 7 was the obviously different one screened with Western blot. Immunoprecipitation and SDS-PAGE showed a different protein band in the serum appeared in the position of about 66.2 ku when compared with normal serum immunoprecipitates. Through mass spectrometry and bioinformatics analysis, heat shock protein 70 (HSP70) and cytokeratin 9 were identified in the different protein band.

CONCLUSION

Western blot, immunoprecipitation, and mass spectrometry is an effectively methodological entity for screening and identifying tumor antigens.

NADP-malic enzyme and Hsp70: co-purification of both proteins and modification of NADP-malic enzyme properties by association with Hsp70

Different preparations of antibodies against 62 kDa NADP-malic enzyme (NADP-ME) from purified maize leaves cross-react with a 72 kDa protein from diverse tissues in many species. A 72 kDa protein, suggested to be a non-photosynthetic NADP-ME, has been purified from several plant species. However, to date, a cDNA coding for this putative 72 kDa NADP-ME has not been isolated. The screening of maize and tobacco leaf expression libraries using antibodies against purified 62 kDa NADP-ME allowed the identification of a heat shock protein (Hsp70). In addition, tandem mass spectrometry (MS/MS) studies indicate that along with NADP-ME, a 72 kDa protein, identified as an Hsp70 and reacting with the antibodies, is also purified from maize roots. On the other hand, the screening of a maize root cDNA library revealed the existence of a cDNA that encodes a mature 66 kDa NADP-ME. These results suggest that the 72 kDa protein is not actually an NADP-ME but in fact an Hsp70, at least in maize and tobacco. Probably, NADP-ME-Hsp70 association, taking place at least when preparing crude extracts, can lead to a co-purification of the proteins and can thus explain the cross-reaction of the antibodies. In the present work, we analyse and discuss a probable interaction of NADP-ME with Hsp70.

Iron-sulfur cluster biosynthesis. Molecular chaperone DnaK promotes IscU-bound [2Fe-2S] cluster stability and inhibits cluster transfer activity

IscU functions as a scaffold for Fe-S cluster assembly and transfer, and is known to be a substrate protein for molecular chaperones. Kinetic studies of Fe-S cluster transfer from holo IscU to apo Fd in the presence of chaperone DnaK demonstrate an inhibitory effect on the rate of Fe-S cluster transfer from IscU. Binding of DnaK reduces the rate of formation of the IscU-Fd complex (greater than 8-fold), but has little influence on the intrinsic rate of iron-sulfur cluster transfer to apo Fd. Apparently the molecular chaperone DnaK does not facilitate the process of Fe-S cluster transfer from IscU. Rather, DnaK has a modest influence on the stability of the IscU-bound Fe-S cluster that may reflect a more important role in promoting cluster assembly. In accord with prior observations the cochaperone DnaJ stimulates the ATPase activity of DnaK, but has a minimal influence on IscU cluster transfer activity, either alone or in concert with DnaK.

Mercury stimulates rat liver glucocorticoid receptor association with Hsp90 and Hsp70

The subject of the present study is the influence of mercury on association of rat liver glucocorticoid receptor (GR) with heat shock proteins Hsp90 and Hsp70. The glucocorticoid receptor heterocomplexes with Hsp90 and Hsp70 were immunopurified from the liver cytosol of rats administered with different doses of mercury. The amounts of co-immunopurified apo-receptor, Hsp90 and Hsp70 were then determined by quantitative Western blotting. The ratio between the amount of heat shock protein Hsp90 or Hsp70 and the amount of apo-receptor within immunopurified heterocomplexes was found to increase in response to mercury administration. On the other hand, the levels of Hsp90 and Hsp70 in hepatic cytosol remained unaltered. The finding that mercury stimulates association of the two heat shock proteins with the glucocorticoid receptor, rendering the cytosolic heat shock protein levels unchanged, suggests that mercury affects the mechanisms controlling the assembly of the receptor heterocomplexes.

Molecular cloning and expression of two HSP70 genes in the prawn, Macrobrachium rosenbergii

Two complementary deoxyribonucleic acid (cDNA) clones encoding 2 different 70-kDa heat shock proteins (HSPs) were isolated from the prawn Macrobrachium rosenbergii. The cDNA clones were 2448 and 2173 bp in length and contained 1950- and 1734-bp open reading frames (ORFs), respectively. The ORFs encoded 649- and 577-amino acid polypeptides, which were named Mar-HSC70 and Mar-HSP70, respectively, according to the sequence identities with other known HSC70s and HSP70s and based on their inducibility in response to heat shock stress (at 35 degrees C). Genomic DNA sequence analysis revealed no introns in either gene. The major structural differences between the 2 proteins were a 60-amino acid segment and a 14-amino acid segment present in the N-terminal and C-terminal, respectively, of Mar-HSC70 that were not found in Mar-HSP70. Northern blotting and semiquantitative reverse transcription-polymerase chain reaction analyses indicated that the Mar-HSP70 gene was expressed under heat shock (35 degrees C) stress in a non-tissue-specific manner. In contrast, Mar-HSC70 messenger ribonucleic acid was constitutively expressed in every tissue except muscle, and its expression in response to heat shock (at 35 degrees C) changed only in muscle.

The in vivo and in vitro characterization of DnaK from Agrobacterium tumefaciens RUOR

Molecular chaperones of the heat shock protein 70 family (Hsp70; also called DnaK in prokaryotes) play an important role in the folding and functioning of cellular protein machinery. The dnaK gene from the plant pathogen Agrobacterium tumefaciens RUOR was amplified using the polymerase chain reaction and the DnaK protein (Agt DnaK) was over-produced as a His-tagged protein in Escherichia coli. The Agt DnaK amino acid sequence was 96% identical to the A. tumefaciens C58 DnaK sequence and 65% identical to the E. coli DnaK sequence. Agt DnaK was shown to be able to functionally replace E. coli DnaK in vivo using complementation assays with an E. coli dnaK756 mutant strain and a dnaK52 deletion strain. Over-production and purification of Agt DnaK was successful, and allowed for further characterization of the protein. Kinetic analysis of the basal ATPase activity of purified Agt DnaK revealed a Vmax of 1.3 nmol phosphate released per minute per milligram DnaK, and a Km of 62 microM ATP. Thus, this is the first study to provide both in vivo and in vitro evidence that Agt DnaK has the properties of a molecular chaperone of the Hsp70 family.

Molecular cloning of bovine cardiac muscle heat-shock protein 70 kDa and its phosphorylation by cAMP-dependent protein kinase in vitro

The 70-kDa heat-shock protein (Hsp70) has been cloned and sequenced from bovine cardiac muscle. On the basis of sequence features, the gene corresponds to the cytoplasmic form of Hsp70. This cardiac Hsp70 cDNA clone has an open reading frame of 1926 bp coding for 641 amino acids and a predicted molecular mass of 70.25 kDa. Comparison of the amino acid sequence revealed an extensive sequence identity with other species of Hsp70. Escherichia coli expressed cardiac Hsp70 stimulated a 2-fold increase in calcineurin (CaN) activity. Notably, we observed that Hsp70 directly interacts with CaN using a pull-down assay. Furthermore, expressed cardiac-specific Hsp70 was phosphorylated in vitro by cAMP-dependent protein kinase. Phosphorylation resulted in the incorporation of 0.1 mol of phosphate per mol of Hsp70. The phosphorylated Hsp70 was unable to activate the phosphatase activity of CaN. This is the first demonstration that Hsp70 is phosphorylated by cAMP-dependent protein kinase and provides an on/off switch for the regulation of CaN signaling by Hsp70.

Overproduction, purification, and characterization of the Plasmodium falciparum heat shock protein 70

Plasmodium falciparum heat shock protein (PfHsp70) has been proposed to be involved in the cytoprotection of the malaria parasite through its action as a molecular chaperone. However, the biochemical and chaperone properties of PfHsp70 have not been elucidated. The heterologous overproduction of P. falciparum proteins in Escherichia coli is problematic because of its AT-rich genome and the usage of codons that are rarely used in E. coli. In this paper, we describe the successful overproduction of (His)(6)-PfHsp70 in E. coli using the pQE30 expression vector system. Initial experiments with E. coli [pQE30/PfHsp70] resulted in the overproduction of the full-length protein and truncated derivatives. The RIG plasmid, which encodes tRNAs for rare codons, was engineered into the E. coli [pQE30/PfHsp70] strain, resulting in significant reduction of the truncated (His)(6)-PfHsp70 derivatives and improved yields of the full-length protein. (His)(6)-PfHsp70 was successfully purified using nickel-chelating Sepharose affinity chromatography and its biochemical properties were determined. The V(max), K(m), and k(cat) for the basal ATPase activity of (His)(6)-PfHsp70 were found to be 14.6 nmol/min/mg, 616.5 microM, and 1.03 min(-1), respectively. Gel filtration studies indicated that (His)(6)-PfHsp70 existed largely as a monomer in solution. This is the first study to biochemically describe PfHsp70 and establishes a foundation for future studies on its chaperone properties.