Functional structure and physiological functions of mammalian wild-type HSP60

The Chaperonins comprise a family of molecular chaperones having a double-ring structure and similar sequence homology. These proteins play an essential role in biological reactions that mediate the folding of newly synthesized polypeptides and partially denatured proteins. In the prokaryotic group I chaperonins, structural and reaction cycle analyses of GroEL and its co-chaperone GroES have been performed in detail. While in eukaryotes, there have been limited reports analyzing the group I chaperonin HSP60 and its co-chaperone HSP10. In the present study, we purified the wild type HSP60 from porcine liver and investigated the interaction between HSP60 and HSP10, including conformation and physiological relationships. Based on the results of transmission electron microscopy, native PAGE, and gel filtration column chromatography, the wild type HSP60 displayed a heptameric single-ring structure in the absence of ATP. In contrast, HSP60 formed mainly a "football-type" complex with HSP10 in the presence of ATP and mediated the refolding of denatured substrate protein. The functional conformation cycle of the purified mammalian HSP60 is distinct from the cycle of the prokaryotic GroEL/GroES chaperonin.

TLR4 mutation and HSP60-induced cell death in adult mouse cardiac myocytes

Extracellular (ex) HSP60 is increasingly recognized as an agent of cell injury. Previously, we reported that low endotoxin exHSP60 causes cardiac myocyte apoptosis. Our findings supported a role for Toll-like receptor (TLR) 4 in HSP60 mediated apoptosis. To further investigate the involvement of TLR4 in cardiac injury, we studied adult cardiac myocytes from C3H/HeJ (HeJ) mice, which have a mutant, nonfunctional TLR4, and compared the results with parallel studies using wild-type (WT) mice. Nuclear factor κB (NFκB) activation is an early step downstream of TLR4. NFκB was activated 1 h after treatment with HSP60 in WT, but not HeJ mouse myocytes. ExHSP60 caused apoptosis in cardiac myocytes from WT mice, but not in myocytes from the HeJ mutants. To further elucidate the importance of exHSP60 in cardiac myocyte injury, both WT and HeJ mutant isolated mouse adult cardiac myocytes were exposed to hypoxia/reoxygenation. Anti-HSP60 antibody treatment reduced apoptosis in the WT group, but had no effect on the HeJ mutant myocytes. Unexpectedly, necrosis was also decreased in the HeJ mutants. Necrosis after hypoxia/reoxygenation in WT cardiac myocytes was mediated in part by TLR2 and TLR4 through rapid activation of PKCα, followed by increased expression of Nox2, and this was ameliorated by blocking antibodies to TLR2/4. These studies provide further evidence that TLR4 mediates exHSP60-associated apoptosis and that exHSP60 has an important role in cardiac myocyte injury, both apoptotic and necrotic.

Identification of Heat Shock Protein 60 as a Regulator of Neutral Sphingomyelinase 2 and Its Role in Dopamine Uptake

Activation of sphingomyelinase (SMase) by extracellular stimuli is the major pathway for cellular production of ceramide, a bioactive lipid mediator acting through sphingomyelin (SM) hydrolysis. Previously, we reported the existence of six forms of neutral pH–optimum and Mg²⁺-dependent SMase (N-SMase) in the membrane fractions of bovine brain. Here, we focus on N-SMase ε from salt-extracted membranes. After extensive purification by 12,780-fold with a yield of 1.3%, this enzyme was eventually characterized as N-SMase2. The major single band of 60-kDa molecular mass in the active fractions of the final purification step was identified as heat shock protein 60 (Hsp60) by matrix-assisted laser desorption/ionization time-of-flight mass spectrometric analysis. Proximity ligation assay and immunoprecipitation study showed that Hsp60 interacted with N-SMase2, prompting us to examine the effect of Hsp60 on N-SMase2 and ceramide production. Interestingly, Hsp60 siRNA treatment significantly increased the protein level of N-SMase2 in N-SMase2-overexpressed HEK293 cells. Furthermore, transfection of Hsp60 siRNA into PC12 cells effectively increased both N-SMase activity and ceramide production and increased dopamine re-uptake with paralleled increase. Taken together, these results show that Hsp60 may serve as a negative regulator in N-SMase2-induced dopamine re-uptake by decreasing the protein level of N-SMase2.

Heat shock protein 60 as a mediator of adipose tissue inflammation and insulin resistance

The stress protein heat shock protein 60 (Hsp60) induces secretion of proinflammatory mediators from murine adipocytes. This study aimed to study Hsp60 as a mediator of adipose tissue inflammation and skeletal muscle cell (SkMC) insulin sensitivity and to quantify plasma Hsp60 concentrations in lean and obese individuals. Regulation of Hsp60 release and Hsp60-induced cytokine secretion and signaling was measured in human adipocytes and SkMCs. Adipocytes exhibited higher Hsp60 release than preadipocytes and SkMCs, which was further stimulated by cytokines and Toll-like receptor (TLR)-4 activation. Hsp60 activated extracellular signal-related kinase (ERK)-1/2, Jun NH(2)-terminal kinase (JNK), p38, nuclear factor (NF)-κB, and impaired insulin-stimulated Akt phosphorylation in adipocytes. Furthermore, Hsp60 stimulated adipocytes to secrete tumor necrosis factor-α, interleukin (IL)-6, and IL-8. In SkMCs, Hsp60 activated ERK1/2, JNK, and NF-κB and inhibits insulin signaling and insulin-stimulated glucose uptake. SkMCs released IL-6, IL-8, and monocyte chemoattractant protein-1 on Hsp60 stimulation. Plasma Hsp60 was higher in obese males than in lean males and correlated positively with BMI, blood pressure, leptin, and homeostasis model assessment-insulin resistance. In summary, Hsp60 is released by human adipocytes, increased in plasma of obese humans, and induces insulin resistance. This is accompanied by activation of proinflammatory signaling in human adipocytes and SkMCs. Thus, Hsp60 might be a factor underlying adipose tissue inflammation and obesity-associated metabolic disorders.

Heat shock protein 60 protects skeletal tissue against glucocorticoid-induced bone mass loss by regulating osteoblast survival

Excessive glucocorticoid administration accelerates osteoblast apoptosis and skeletal deterioration. Heat shock proteins (HSPs) regulate metabolic activities in osteoblastic cells. This study characterized the biological significance of HSP60 in glucocorticoid-induced bone loss. Rats were treated with glucocorticoid, HSP60 antisense oligonucleotides, or adenovirus-mediated HSP60 gene transfer. Bone mineral density, metaphyseal trabecular micro-architecture, and fragility were analyzed by dual X-ray absorptiometry, micro-computed tomography, and material testing, respectively. Differential proteomic profiles of bone tissue extracts were detected by bi-dimensional electrophoresis and mass spectrometry. Survival and proapoptotic signal transduction were quantified by immunoblotting. Glucocorticoid-treated rats had low bone mineral density and metaphyseal trabecular microstructure in association with downregulation of collagen 1α1 and HSP60 expressions in bone tissue. Gain of HSP60 function by adenovirus-mediated HSP60 gene transfer abrogated the deleterious effects of glucocorticoid treatment on bone mass, trabecular microstructure, and mechanical strength. Enhancement of HSP60 signaling attenuated the glucocorticoid-induced loss of trabecular bone volume, mineral acquisition reactions and osteoblast surface. HSP60 gene transfer activated ERK and Akt and reduced Bax and cytochrome c release, as well as caspase-3 cleavage, which attenuated the inhibitory effects of glucocorticoid treatment on osteoblast survival. Loss of HSP60 function by HSP60 antisense oligonucleotides accelerated mitochondrial apoptotic programs and osteoblast apoptosis. Knockdown of HSP60 induced loss of bone mass, micro-architecture integrity, and mechanical property. Taken together, loss of HSP60 signaling contributes to the glucocorticoid-induced enhancement of pro-apoptotic reactions, thereby accelerating osteoblast apoptosis and bone mass loss. Enhancement of HSP60 function is beneficial for protecting bone tissue against the glucocorticoid-induced inhibition of bone cell viability and bone formation.

Comparison of the moonlighting actions of the two highly homologous chaperonin 60 proteins of Mycobacterium tuberculosis

Evidence is emerging that the two chaperonin (Cpn) 60 proteins of Mycobacterium tuberculosis, Cpn60.1 and Cpn60.2, have moonlighting actions that may contribute to the pathology of tuberculosis. We studied the release of Cpn60.1 from M. tuberculosis and infected macrophage like cells and compared recombinant Cpn60.1 and Cpn60.2 in a range of cell-based assays to determine how similar the actions of these highly homologous proteins are. We now establish that Cpns are similar as follows: (i) Cpn60.1, as it has been shown for Cpn60.2, is released by M. tuberculosis in culture, and Cpn60.1 is furthermore released when the bacterium is in quiescent, but not activated, macrophage like cells, and (ii) both proteins only showed a partial requirement for MyD88 for the induction of proinflammatory cytokine production compared to lipopolysaccharide. However, we also found major differences in the cellular action of Cpns. (i) Cpn60.2 proved to be a more potent stimulator of whole blood leukocytes than Cpn60.1 and was the only one to induce tumor necrosis factor alpha synthesis. (ii) Cpn60.1 bound to ca. 90% of circulating monocytes compared to Cpn60.2, which bound <50% of these cells. Both chaperonins bound to different cell surface receptors, while monocyte activation by both proteins was completely abrogated in TLR4-/- mice, although Cpn60.2 also showed significant requirement for TLR2. Finally, an isogenic mutant lacking cpn60.1, but containing intact cpn60.2, was severely inhibited in generating multinucleate giant cells in an in vitro human granuloma assay. These results clearly show that, despite significant sequence homology, M. tuberculosis Cpn60 proteins interact in distinct ways with human or murine macrophages.

Administration of Mycobacterium leprae rHsp65 aggravates experimental autoimmune uveitis in mice

The 60 kDa heat shock protein family, Hsp60, constitutes an abundant and highly conserved class of molecules that are highly expressed in chronic-inflammatory and autoimmune processes. Experimental autoimmune uveitis [EAU] is a T cell mediated intraocular inflammatory disease that resembles human uveitis. Mycobacterial and homologous Hsp60 peptides induces uveitis in rats, however their participation in aggravating the disease is poorly known. We here evaluate the effects of the Mycobacterium leprae Hsp65 in the development/progression of EAU and the autoimmune response against the eye through the induction of the endogenous disequilibrium by enhancing the entropy of the immunobiological system with the addition of homologous Hsp. B10.RIII mice were immunized subcutaneously with interphotoreceptor retinoid-binding protein [IRBP], followed by intraperitoneally inoculation of M. leprae recombinant Hsp65 [rHsp65]. We evaluated the proliferative response, cytokine production and the percentage of CD4(+)IL-17(+), CD4(+)IFN-gamma(+) and CD4(+)Foxp3(+) cells ex vivo, by flow cytometry. Disease severity was determined by eye histological examination and serum levels of anti-IRBP and anti-Hsp60/65 measured by ELISA. EAU scores increased in the Hsp65 group and were associated with an expansion of CD4(+)IFN-gamma(+) and CD4(+)IL-17(+) T cells, corroborating with higher levels of IFN-gamma. Our data indicate that rHsp65 is one of the managers with a significant impact over the immune response during autoimmunity, skewing it to a pathogenic state, promoting both Th1 and Th17 commitment. It seems comprehensible that the specificity and primary function of Hsp60 molecules can be considered as a potential pathogenic factor acting as a whistleblower announcing chronic-inflammatory diseases progression.

Chlamydia trachomatis infection and anti-Hsp60 immunity: the two sides of the coin

Chlamydia trachomatis (CT) infection is one of the most common causes of reproductive tract diseases and infertility. CT-Hsp60 is synthesized during infection and is released in the bloodstream. As a consequence, immune cells will produce anti-CT-Hsp60 antibodies. Hsp60, a ubiquitous and evolutionarily conserved chaperonin, is normally sequestered inside the cell, particularly into mitochondria. However, upon cell stress, as well as during carcinogenesis, the chaperonin becomes exposed on the cell surface (sf-Hsp60) and/or is secreted from cells into the extracellular space and circulation. Reports in the literature on circulating Hsp and anti-Hsp antibodies are in many cases short on details about Hsp60 concentrations, and about the specificity spectra of the antibodies, their titers, and their true, direct, pathogenetic effects. Thus, more studies are still needed to obtain a definitive picture on these matters. Nevertheless, the information already available indicates that the concurrence of persistent CT infection and appearance of sf-Hsp60 can promote an autoimmune aggression towards stressed cells and the development of diseases such as autoimmune arthritis, multiple sclerosis, atherosclerosis, vasculitis, diabetes, and thyroiditis, among others. At the same time, immunocomplexes composed of anti-CT-Hsp60 antibodies and circulating Hsp60 (both CT and human) may form deposits in several anatomical locations, e.g., at the glomerular basal membrane. The opposite side of the coin is that pre-tumor and tumor cells with sf-Hsp60 can be destroyed with participation of the anti-Hsp60 antibody, thus stopping cancer progression before it is even noticed by the patient or physician.

Sequence variants in SPAST, SPG3A and HSPD1 in hereditary spastic paraplegia

Hereditary spastic paraplegia (HSP) is a group of clinically and genetically heterogeneous neurodegenerative disorders characterized by progressive spasticity and weakness in the lower limbs. The most common forms of autosomal dominant HSP, SPG4 and SPG3, are caused by sequence variants in the SPAST and SPG3A genes, respectively. The pathogenic variants are scattered all over these genes and many variants are unique to a specific family. The phenotype in SPG4 patients can be modified by a variant in SPAST (p.Ser44Leu) and recently, a variant in HSPD1, the gene underlying SPG13, was reported as a second genetic modifier in SPG4 patients. In this study HSP patients were screened for variants in SPG3A, SPAST and HSPD1 in order to identify disease causing variations. SPAST was sequenced in all patients whereas subsets were sequenced in HSPD1 and in selected exons of SPG3A. SPG4 patients and their HSP relatives were genotyped for the modifying variant in HSPD1. We report six new sequence variants in SPAST including a fourth non synonymous sequence variant in exon 1 and two synonymous changes of which one has been found in a HSP patient previously, but never in controls. Of the novel variants in SPAST four were interpreted as disease causing. In addition one new disease causing sequence variant and one non pathogenic non synonymous variant were found in SPG3A. In HSPD1 we identified a sporadic patient homozygote for the potential modifying variation. The effect of the modifying HSPD1 variation was not supported by identification in one SPG4 family.

Conserved inserts in the Hsp60 (GroEL) and Hsp70 (DnaK) proteins are essential for cellular growth

The Hsp60 and Hsp70 chaperones contain a number of conserved inserts that are restricted to particular phyla of bacteria. A one aa insert in the E. coli GroEL and a 21-23 insert in the DnaK proteins are specific for most Gram-negative bacteria. Two other inserts in DnaK are limited to certain groups of proteobacteria. The requirement of these inserts for cellular growth was examined by carrying out complementation studies with temperature-sensitive (T(s)) mutants of E. coli groEL or dnaK. Our results demonstrate that deletion or most changes in these inserts completely abolished the complementation ability of the mutant proteins. Studies with GroEL and DnaK from some other species that either lacked or contained these inserts also indicated that these inserts are essential for growth of E. coli. The DnaK from some bacteria contains a two aa insert that is not found in E. coli. Introduction of this insert into the E. coli DnaK also led to its inactivation, indicating that these inserts are specific for different groups. We postulate that these conserved inserts that are localized in loop regions on protein surfaces, are involved in some ancillary functions that are essential for the groups of bacteria where they are found.

HSP60 as a target of anti-ergotypic regulatory T cells

The 60 kDa heat shock protein (HSP60) has been reported to influence T-cell responses in two ways: as a ligand of toll-like receptor 2 signalling and as an antigen. Here we describe a new mechanism of T-cell immuno-regulation focused on HSP60: HSP60 is up-regulated and presented by activated T cells (HSP60 is an ergotope) to regulatory (anti-ergotypic) T cells. Presentation of HSP60 by activated T cells was found to be MHC-restricted and dependent on accessory molecules - CD28, CD80 and CD86. Anti-ergotypic T cells responded to T-cell HSP60 by proliferation and secreted IFNγ and TGFβ1. In vitro, the anti-ergotypic T cells inhibited IFNγ production by their activated T-cell targets. In vivo, adoptive transfer of an anti-ergotypic HSP60-specific T-cell line led to decreased secretion of IFNγ by arthritogenic T cells and ameliorated adjuvant arthritis (AA). Thus, the presentation of HSP60 by activated T cells turns them into targets for anti-ergotypic regulatory T cells specific for HSP60. However, the direct interaction between the anti-ergotypic T regulators (anti-HSP60) and the activated T cells also down-regulated the regulators. Thus, by functioning as an ergotope, HSP60 can control both the effector T cells and the regulatory HSP60-specific T cells that control them.

In infertile women, cells from Chlamydia trachomatis infected sites release higher levels of interferon-gamma, interleukin-10 and tumor necrosis factor-alpha upon heat-shock-protein stimulation than fertile women

BACKGROUND

The magnitude of reproductive morbidity associated with sexually transmitted Chlamydia trachomatis infection is enormous. Association of antibodies to chlamydial heat shock proteins (cHSP) 60 and 10 with various disease sequelae such as infertility or ectopic pregnancy has been reported. Cell-mediated immunity is essential in resolution and in protection to Chlamydia as well as is involved in the immunopathogenesis of chlamydial diseases. To date only peripheral cell mediated immune responses have been evaluated for cHSP60. These studies suggest cHSPs as important factors involved in immunopathological condition associated with infection. Hence study of specific cytokine responses of mononuclear cells from the infectious site to cHSP60 and cHSP10 may elucidate their actual role in the cause of immunopathogenesis and the disease outcome.

METHODS

Female patients (n = 368) attending the gynecology out patient department of Safdarjung hospital, New Delhi were enrolled for the study and were clinically characterized into two groups; chlamydia positive fertile women (n = 63) and chlamydia positive infertile women (n = 70). Uninfected healthy women with no infertility problem were enrolled as controls (n = 39). cHSP60 and cHSP10 specific cytokine responses (Interferon (IFN)-gamma, Interleukin (IL)-10, Tumor Necrosis Factor (TNF)-alpha, IL-13 and IL-4) were assessed by ELISA in stimulated cervical mononuclear cell supernatants.

RESULTS

cHSP60 and cHSP10 stimulation results in significant increase in IFN-gamma (P = 0.006 and P = 0.04 respectively) and IL-10 levels (P = 0.04) in infertile group as compared to fertile group. A significant cHSP60 specific increase in TNF-alpha levels (P = 0.0008) was observed in infertile group as compared to fertile group. cHSP60 and cHSP10 specific IFN-gamma and IL-10 levels were significantly correlated (P < 0.0001, r = 0.54 and P = 0.004, r = 0.33 respectively) in infertile group.

CONCLUSION

Our results suggest that exposure to chlamydial heat shock proteins (cHSP60 and cHSP10) could significantly affect mucosal immune function by increasing the release of IFN-gamma, IL-10 and TNF-alpha by cervical mononuclear cells.

Effects of parental effort on blood stress protein HSP60 and immunoglobulins in female blue tits: a brood size manipulation experiment

1. Physiological stress in animals may impose a limit for investment in current reproduction in the wild. A brood manipulation experiment was conducted in a population of blue tits Cyanistes caeruleus to study the effect of parental effort on changes in two types of proteins related with stress: the blood stress protein HSP60 and the plasma immunoglobulins. 2. Levels of HSP60 were reduced across the experiment for females attending reduced broods, and females attending enlarged broods experienced a reduction of immunoglobulin levels. Moreover, the overall changes in the levels of both proteins were positively related. 3. By controlling for the change in immunoglobulin levels we found an increase in HSP60 for females in the enlarged treatment, presumably to offset deleterious effects derived from increased effort. 4. Maternal effort was able to partially compensate for the effect of treatment as nestlings did not differ in mass and levels of immunoglobulins and HSP60 among treatments. 5. Physiological stress as reflected in stress and immunoglobulin proteins may limit maternal effort in breeding blue tits.

Allosteric transitions in the chaperonin GroEL are captured by a dominant normal mode that is most robust to sequence variations

The Escherichia coli chaperonin GroEL, which helps proteins to fold, consists of two heptameric rings stacked back-to-back. During the reaction cycle GroEL undergoes a series of allosteric transitions triggered by ligand (substrate protein, ATP, and the cochaperonin GroES) binding. Based on an elastic network model of the bullet-shaped double-ring chaperonin GroEL-(ADP)(7)-GroES structure (R''T state), we perform a normal mode analysis to explore the energetically favorable collective motions encoded in the R''T structure. By comparing each normal mode with the observed conformational changes in the R''T --> TR'' transition, a single dominant normal mode provides a simple description of this highly intricate allosteric transition. A detailed analysis of this relatively high-frequency mode describes the structural and dynamic changes that underlie the positive intra-ring and negative inter-ring cooperativity. The dynamics embedded in the dominant mode entails highly concerted structural motions with approximate preservation of sevenfold symmetry within each ring and negatively correlated ones between the two rings. The dominant normal mode (in comparison with the other modes) is robust to parametric perturbations caused by sequence variations, which validates its functional importance. Response of the dominant mode to local changes that mimic mutations using the structural perturbation method technique leads to a wiring diagram that identifies a network of key residues that regulate the allosteric transitions. Many of these residues are located in intersubunit interfaces, and may therefore play a critical role in transmitting allosteric signals between subunits.

Cell adherence-promoted activity of Plesiomonas shigelloides groEL

Previously, it has been demonstrated that the invasion of Caco-2 cells by Plesiomonas shigelloides induces apoptotic cell death. Therefore, the attachment to and colonization of eukaryotic intestinal host cells by P. shigelloides are important steps in causing pathogenicity. In this study, the participation of P. shigelloides GroEL in the attachment of P. shigelloides was examined. The groESL operon of P. shigelloides was isolated by PCR. The nucleotide sequence of the groESL operon of P. shigelloides revealed two ORFs of 294 nucleotides for groES and 1647 nucleotides for groEL. Cell fractionation and immunostaining experiments suggested that the GroEL of P. shigelloides was associated with the bacterial cell surface. The expression of the groEL gene was upregulated during the attachment and apoptosis-induction stages, and the expression of the protein was also induced during the attachment stage. Furthermore, GroEL efficiently promoted the attachment of P. shigelloides to Caco-2 cells, as measured by a FACSCalibur flow cytometer. These results demonstrated that GroEL has a positive influence on the attachment of P. shigelloides to Caco-2 cells.

DnaK Plays a Pivotal Role in Tat Targeting of CueO and Functions beside SlyD as a General Tat Signal Binding Chaperone

The Tat (twin-arginine translocation) system from Escherichia coli transports folded proteins with N-terminal twin-arginine signal peptides across the cytoplasmic membrane. The influence of general chaperones on Tat substrate targeting has not been clarified so far. Here we show that the chaperones SlyD and DnaK bind to a broad range of different Tat signal sequences in vitro and in vivo. Initially, SlyD and GroEL were purified from DnaK-deficient extracts by their affinity to various Tat signal sequences. Of these, only SlyD bound Tat signal sequences also in the presence of DnaK. SlyD and DnaK also co-purified with Tat substrate precursors, demonstrating the binding to Tat signal sequences in vivo. Deletion of dnaK completely abolished Tat-dependent translocation of CueO, but not of DmsA, YcdB, or HiPIP, indicating that DnaK has an essential role specifically for CueO. DnaK was not required for stability of the CueO precursor and thus served in some essential step after folding. A CueO signal sequence fusion to HiPIP was Tat-dependently transported without the need of DnaK, indicating that the mature domain of CueO is responsible for the DnaK dependence. The overall results suggest that SlyD and DnaK are in the set of chaperones that can serve as general Tat signal-binding proteins. DnaK has additional functions that are indispensable for the targeting of CueO.

Modulation of endothelial cell damages by anti-Hsp60 autoantibodies in systemic autoimmune diseases

Heat-shock protein (Hsp) family is made up of heterogeneous proteins of which Hsp60 members are the most studied. It is now generally admitted that Hsp60 is not only a mitochondrial component but can be localized on the membrane cell surface. Considered as a signal danger following infections, Hsp60 can induce the production of anti-Hsp60 antibodies as defense mechanisms against pathogens. However, endogenous Hsp60 is also a target of autoantibodies in autoimmune disorders, atherosclerosis and vascular diseases, in which anti-endothelial cell antibodies (AECA) are generated. Hsp60 is one of the endothelial cell autoantigens able to trigger cytotoxic and apoptotic responses when recognized by the related autoantibodies. Depending on the Hsp60 epitope specificity, it appears that AECA with Hsp60 reactivity may differ in their functional effects. These observations suggest that new therapeutic approach to avoid endothelial cell damages due to anti-Hsp60 autoantibodies would be successful provided that specific Hsp60 epitopes would have been precisely characterized.

Protective effect of human heat shock protein 60 suggested by its association with decreased seropositivity to pathogens

The presence of heat shock protein 60 (Hsp60) in human plasma has been linked with cardiovascular disease (CVD). In this study, the examination of the relationship between Hsp60 in plasma and seropositivity for three microbial agents, which are thought to be risk factors for CVD, surprisingly revealed a negative association between Hsp60 and seropositivity, suggesting a protective effect of this circulating stress protein.

H pylori infection and systemic antibodies to CagA and heat shock protein 60 in patients with coronary heart disease

AIM: To determine the overall prevalence of H pylori and CagA positive H pylori infection and the prevalence of other bacterial and viral causes of chronic infection in patients with coronary heart disease (CHD), and the potential role of anti-heat-shock protein 60 (Hsp60) antibody response to these proteins in increasing the risk of CHD development.

METHODS: Eighty patients with CHD and 160 controls were employed. We also compared the levels of anti-heat-shock protein 60 (Hsp60) antibodies in the two groups. The H pylori infection and the CagA status were determined serologically, using commercially available enzyme-linked immunosorbent assays (ELISA), and a Western blotting method developed in our laboratory. Systemic antibodies to Hsp60 were determined by a sandwich ELISA, using a polyclonal antibody to Hsp60 to sensitise polystyrene plates and a commercially available human Hsp60 as an antigen.

RESULTS: The overall prevalence of H pylori infection was 78.7% (n = 63) in patients and 76.2% (n = 122) in controls (P = 0.07). Patients infected by CagA-positive (CagA⁺) H pylori strains were 71.4% (n = 45) vs 52.4% of infected controls (P = 0.030, OR = 2.27). Systemic levels of IgG to Hsp60 were increased in H pylori-negative patients compared with uninfected controls (P < 0.001) and CagA-positive infected patients compared with CagA-positive infected controls (P = 0.007).

CONCLUSION: CagA positive H pylori infection may concur to the development of CHD; high levels of anti-Hsp60 antibodies may constitute a marker and/or a concomitant pathogenic factor of the disease.

Physiologic effects of forced down-regulation of dnaK and groEL expression in Streptococcus mutans

Strains of Streptococcus mutans lacking DnaK or GroEL appear not to be isolable. To better distinguish the roles played by these chaperones/chaperonins in the physiology of S. mutans, we created a knockdown strategy to lower the levels of DnaK by over 95% in strain SM12 and the level of GroEL about 80% in strain SM13. Interestingly, GroEL levels were approximately twofold higher in SM12 than in the parent strain, but the levels of DnaK were not altered in the GroEL knockdown strain. Both SM12 and SM13 grew slower than the parent strain, had a strong tendency to aggregate in broth culture, and showed major changes in their proteomes. Compared with the wild-type strain, SM12 and SM13 had impaired biofilm-forming capacities when grown in the presence of glucose. The SM12 strain was impaired in its capacity to grow at 44 degrees C or at pH 5.0 and was more susceptible to H(2)O(2), whereas SM13 behaved like the wild-type strain under these conditions. Phenotypical reversions were noted for both mutants when cells were grown in continuous culture at a low pH, suggesting the occurrence of compensatory mutations. These results demonstrate that DnaK and GroEL differentially affect the expression of key virulence traits, including biofilm formation and acid tolerance, and support that these chaperones have evolved to accommodate unique roles in the context of this organism and its niche.

Hfq modulates the sigmaE-mediated envelope stress response and the sigma32-mediated cytoplasmic stress response in Escherichia coli

Hfq, a chaperone for small noncoding RNAs, regulates many processes in Escherichia coli, including the sigma(S)-mediated general stress response. Here we used microarray analysis to identify the changes in gene expression resulting from lack of Hfq. We identify several potential new targets for Hfq regulation, including genes encoding outer membrane proteins, enzymes, factors, and transporters. Many of these genes are involved in amino acid uptake and biosynthesis, sugar uptake and metabolism, and cell energetics. In addition, we find altered regulation of the sigma(E)- and sigma(32)-mediated stress responses, which we analyze further. We show that cells lacking Hfq induce the sigma(E)-mediated envelope stress response and are defective in sigma(E)-mediated repression of outer membrane proteins. We also show that the sigma(32)-mediated cytoplasmic stress response is repressed in cells lacking Hfq due to increased expression of DnaK. Furthermore, we show that cells lacking Hfq are defective in the "long-term adaptation" of sigma(32) to chronic chaperone overexpression. Together, our results indicate that Hfq may play a general role in stress response regulation in E. coli.

Temperature adaptation of Bacillus subtilis by chromosomal groEL replacement

We investigated a temperature adaptation of Bacillus subtilis 168 in which chromosomal groEL was replaced with a psychrophilic groEL. This strain can grow at 50 degrees C but not at 51 degrees C, a temperature at which wild-type B. subtilis can grow. Using in vivo random mutagenesis by the B. subtilis mutator strain (mutS, mutM, mutY), two thermo-adaptants were isolated from the groEL substituted strain at 52 degrees C. They contained novel amino acid alterations in their ATP binding motif (T93I) and the inter-monomer contact (R285H) region of GroEL. These results suggest that GroEL participates in bacterial temperature adaptation.

GroEL-mediated protein folding: making the impossible, possible

Protein folding is a spontaneous process that is essential for life, yet the concentrated and complex interior of a cell is an inherently hostile environment for the efficient folding of many proteins. Some proteins-constrained by sequence, topology, size, and function-simply cannot fold by themselves and are instead prone to misfolding and aggregation. This problem is so deeply entrenched that a specialized family of proteins, known as molecular chaperones, evolved to assist in protein folding. Here we examine one essential class of molecular chaperones, the large, oligomeric, and energy utilizing chaperonins or Hsp60s. The bacterial chaperonin GroEL, along with its co-chaperonin GroES, is probably the best-studied example of this family of protein-folding machine. In this review, we examine some of the general properties of proteins that do not fold well in the absence of GroEL and then consider how folding of these proteins is enhanced by GroEL and GroES. Recent experimental and theoretical studies suggest that chaperonins like GroEL and GroES employ a combination of protein isolation, unfolding, and conformational restriction to drive protein folding under conditions where it is otherwise not possible.

In vitro reassembly of tobacco ribulose-1,5-bisphosphate carboxylase/oxygenase from fully denatured subunits

It has been generally proved impossible to reassemble ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) from fully denatured subunits in vitro in higher plant, because large subunit of fully denatured Rubisco is liable to precipitate when the denaturant is removed by common methods of direct dilution and one-step dialysis. In our experiment, the problem of precipitation was resolved by an improved gradual dialysis method, which gradually decreased the concentration of denaturant. However, fully denatured Rubisco subunits still could not be reassembled into holoenzyme using gradual dialysis unless chaperonin 60 was added. The restored activity of reassembled Rubisco was approximately 8% of natural enzyme. The quantity of reassembled Rubisco increased greatly when heat shock protein 70 was present in the reassembly process. ATP and Mg2+ were unnecessary for in vitro reassembly of Rubisco, and Mg2+ inhibited the reassembly process. The reassembly was weakened when ATP, Mg2+ and K+ existed together in the reassembly process.

The role of heat shock protein 60, vascular endothelial growth factor and antiphospholipid antibodies in Behçet disease

BACKGROUND

Behçet disease is a systemic inflammatory disease of unknown aetiology. T cells in this disease proliferate vigorously in response to a specific peptide of heat shock protein (HSP) 60 in an antigen-specific fashion. Vascular endothelial cell growth factor (VEGF) is a cytokine participating in the inflammatory process. One of the prominent features of Behçet disease is vasculitis as a result of endothelial dysfunction. Antiphospholipid antibodies (APA) may play a role in the development of thrombosis by inhibiting production of prostacyclin by endothelial cells.

OBJECTIVES

To investigate the role of HSP60, VEGF and APA in Behçet disease and their relation to clinical manifestations and disease activity.

METHODS

Thirty patients with Behçet disease were included; 17 were in the active stage and 13 were in the inactive. Fifteen age- and sex-matched healthy subjects served as controls. Complete clinical examination and Doppler examination were done. Serum levels of HSP60, VEGF and APA were performed.

RESULTS

Serum levels of HSP60, VEGF and APA were significantly higher in patients than in controls; however, their level did not correlate with disease activity. The serum level of VEGF correlated significantly with the presence of vascular manifestations and ocular involvement. The serum level of APA was greater in patients with thrombosis. HSP60 has an important role in aetiopathogenesis of Behçet disease, which sheds new light on its autoimmune nature.

CONCLUSIONS

An elevated serum level of VEGF may be a risk factor for the development of ocular disease contributing to poor visual outcome.

Induction of Porphyromonas gingivalis GroEL signaling via binding to Toll-like receptors 2 and 4

BACKGROUND/AIMS

Heat shock protein 60 (HSP60) has been recognized as an important molecule in infectious and autoimmune diseases. Although Porphyromonas gingivalis GroEL, a homologue of HSP60, is a potent stimulator of inflammatory cytokines, its receptor and signaling mechanisms are not yet understood in detail. In this study, we investigated whether the Toll-like receptor (TLR) family plays a functional role as a P. gingivalis GroEL receptor.

METHODS

Human macrophage-like THP-1 cells were used and the nuclear factor-kappaB (NF-kappaB) activity of cells stimulated with a recombinant P. gingivalis GroEL was measured with a luciferase assay. Flow cytometry analysis was used to determine the binding to THP-1 cells of fluorescein isothiocyanate (FITC)-labeled GroEL. In addition, anti-human TLR (anti-hTLR)2 and anti-hTLR4 monoclonal antibodies were used to assess the functional role of TLR2 and TLR4 as the receptors for GroEL.

RESULTS

We observed by luciferase assay that the purified recombinant GroEL was able to stimulate NF-kappaB transcriptional activity in THP-1 cells. Flow cytometry analysis showed that the FITC-labeled GroEL bound to THP-1 cells in a dose-dependent fashion. Our binding competition analysis with FITC-labeled and unlabeled GroEL showed that it bound to the cells as a specific mode of action. On the other hand, GroEL-stimulated NF-kappaB transcriptional activity was significantly inhibited by anti-hTLR2 and anti-hTLR4 antibodies and was inhibited more strongly by a combination of both antibodies.

CONCLUSION

Our present study demonstrates that P. gingivalis GroEL induces its intracellular signaling cascade in THP-1 cells via TLR2 or TLR4 and via a combination of both receptors.

Differential effects of mitochondrial heat shock protein 60 and related molecular chaperones to prevent intracellular beta-amyloid-induced inhibition of complex IV and limit apoptosis

Defects in mitochondrial oxidative metabolism, in particular decreased activity of cytochrome c oxidase, have been reported in Alzheimer disease tissue and in cultured cells that overexpress amyloid precursor protein. Mitochondrial dysfunction contributes to neurodegeneration in Alzheimer disease partly through formation of reactive oxygen species and the release of sequestered molecules that initiate programmed cell death pathways. The heat shock proteins (HSP) are cytoprotective against a number of stressors, including accumulations of misfolded proteins and reactive oxygen species. We reported on the property of Hsp70 to protect cultured neurons from cell death caused by intraneuronal beta-amyloid. Here we demonstrate that Hsp60, Hsp70, and Hsp90 both alone and in combination provide differential protection against intracellular beta-amyloid stress through the maintenance of mitochondrial oxidative phosphorylation and functionality of tricarboxylic acid cycle enzymes. Notably, beta-amyloid was found to selectively inhibit complex IV activity, an effect selectively neutralized by Hsp60. The combined effect of HSPs was to reduce the free radical burden, preserve ATP generation, decrease cytochrome c release, and prevent caspase-9 activation, all important mediators of beta-amyloid-induced neuronal dysfunction and death.

On the brotherhood of the mitochondrial chaperones mortalin and heat shock protein 60

The heat shock chaperones mortalin/mitochondrial heat shock protein 70 (mtHsp70) and Hsp60 are found in multiple subcellular sites and function in the folding and intracellular trafficking of many proteins. The chaperoning activity of these 2 proteins involves different structural and functional mechanisms. In spite of providing an excellent model for an evolutionarily conserved molecular "brotherhood", their individual functions, although overlapping, are nonredundant. As they travel to various locations, both chaperones acquire different binding partners and exert a more divergent involvement in tumorigenesis, cellular senescence, and immunology. An understanding of their functional biology may lead to novel designing and development of therapeutic strategies for cancer and aging.

Chloroplast heat shock protein Cpn60 fromChlamydomonas reinhardtiiexhibits a novel function as a group II intron-specific RNA-binding protein

Intron-binding proteins in eukaryotic organelles are mainly encoded by the nuclear genome and are thought to promote the maturation of precursor RNAs. Here, we present a biochemical approach that enable the isolation of a novel nuclear-encoded protein from Chlamydomonas reinhardtii showing specific binding properties to organelle group II intron RNA. Using FPLC chromatography of chloroplast protein extracts, a 61-kDa RNA-binding protein was isolated and then tentatively identified by mass spectrometry as the chloroplast heat shock protein Cpn60. Heterologous Cpn60 protein was used in RNA protein gel mobility shift assays and revealed that the ATPase domains of Cpn60 mediates the specific binding of two group II intron RNAs, derived from the homologous chloroplast psaA gene and the heterologous mitochondrial LSU rRNA gene. The function of Cpn60 as a general organelle splicing factor is discussed.

Bartonella bacilliformis GroEL: effect on growth of human vascular endothelial cells in infected cocultures

Bartonella are the only bacteria known to induce angioproliferative lesions of the human vasculature and liver during infection. Previous work from our lab suggests that GroEL participates in the mitogenic response observed in HUVEC cultures supplemented with the soluble fraction of Bartonella bacilliformis. Work in this study shows that exposure to high concentrations of the fraction is actually cytotoxic for HUVECs. To analyze this phenomenon, live B. bacilliformis-HUVEC cocultures were employed to study the effect of excess bacterial GroEL on the host cell during active infection. Four B. bacilliformis strains were generated to produce varying levels of GroEL. HUVEC cocultures with LSS100, a strain that synthesizes markedly greater quantities of GroEL relative to others, significantly accelerates apoptosis of the cocultured HUVECs relative to other strains. Acceleration of apoptosis can be inhibited by Z-VAD-FMK, a pan-caspase inhibitor. Time course data show that, at 18 h of infection, both LSS100 and control strains significantly inhibit spontaneous apoptosis of cocultured HUVECs, as previously reported for other Bartonella species. However, by 48 h, LSS100 significantly increases apoptosis of the host cell. We hypothesize that intracellular Bartonella GroEL functions as an Hsp60 analogue, a eukaryotic orthologue known to accelerate pro-caspase 3 activation by enhancing its vulnerability to upstream activator caspases. These data suggest another strategy whereby Bartonella may regulate host cell growth.

ChlamydiaHeat Shock Protein 60 Induces Trophoblast Apoptosis through TLR4

Intrauterine infection affects placental development and function, and subsequently may lead to complications such as preterm delivery, intrauterine growth retardation, and preeclampsia; however, the molecular mechanisms are not clearly known. TLRs mediate innate immune responses in placenta, and recently, TLR2-induced trophoblast apoptosis has been suggested to play a role in infection-induced preterm delivery. Chlamydia trachomatis is the etiological agent of the most prevalent sexually transmitted bacterial infection in the United States. In this study, we show that in vitro chlamydial heat shock protein 60 induces apoptosis in primary human trophoblasts, placental fibroblasts, and the JEG3 trophoblast cell line, and that TLR4 mediates this event. We observed a host cell type-dependent apoptotic response. In primary placental fibroblasts, chlamydial heat shock protein 60-induced apoptosis was caspase dependent, whereas in JEG3 trophoblast cell lines it was caspase independent. These data suggest that TLR4 stimulation induces apoptosis in placenta, and this could provide a novel mechanism of pathogenesis for poor fertility and pregnancy outcome in women with persistent chlamydia infection.

Co-expression of chaperonin GroEL/GroES enhances in vivo folding of yeast mitochondrial aconitase and alters the growth characteristics of Escherichia coli

Over last two decades many researchers have demonstrated the mechanisms of how the Escherichia coli chaperonin GroEL and GroES work in the binding and folding of different aggregation prone substrate proteins both in vivo and in vitro. However, preliminary aspects, such as influence of co-expressing GroEL and GroES on the over expression of other recombinant proteins in E. coli cells and subsequent growth aspects, as well as the conditions for optimum production of recombinant proteins in presence of recombinant chaperones have not been properly investigated. In the present study we have demonstrated the temperature dependent growth characteristics of E. coli cells, which are over expressing recombinant aconitase and how the co-expression of E. coli chaperonin GroEL and GroES influence the growth rate of the cells and in vivo folding of recombinant aconitase. Presence of co-expressed GroEL reduces the aconitase over-expression drastically; however, exogenous GroEL & GroES together compensate this reduction. For the aconitase over-expressing cells the growth rate decreases by 30% at 25 degrees C when compared with the M15 E. coli cells, however, there is an increase of 20% at 37 degrees C indicating the participation of endogenous chaperonin in the folding of a fraction of over expressed aconitase. However, in presence of co-expressed GroEL and GroES the growth rate of aconitase producing cells was enhanced by 30% at 37 degrees C confirming the assistance of exogenous chaperone system for the folding of recombinant aconitase. Optimum in vivo folding of aconitase requires co-production of complete E. coli chaperonin machinery GroEL and GroES together.

Heat-shock protein 60 as a tool for novel therapeutic strategies that target the induction of regulatory T cells in human arthritis

In health, immune responses to self are abundantly available, but under strict control of mechanisms of peripheral tolerance. Occasionally the immune system loses control and an autoimmune disease develops. At present, treatment of autoimmune disease is based on generalised suppression of all immune responses, and is often needed to be lifelong, leading to long-term toxicities and suppression of protective immune responses against pathogens. A more targeted approach would be to reset the immune system via restoration of failing regulatory mechanisms, and redirect the immune system to a state of tolerance. Over the past decade there have been enormous advances in the understanding of basic processes that control immune tolerance, pushing regulatory T cells forward as targets for novel therapeutic strategies. This review describes the development of antigen-specific immunotherapy that targets the antigen-specific induction of regulatory T cells as a means to treat autoimmune disease. The 'holy grail' for autoimmunity is not the disease-causing antigen, but the disease-curing antigen.

Heat shock protein 60 in rostral ventrolateral medulla reduces cardiovascular fatality during endotoxaemia in the rat

The rostral ventrolateral medulla (RVLM) is the origin of a 'life-and-death' signal that reflects central cardiovascular regulatory failure during brain stem death. Using an experimental endotoxaemia model, we evaluated the hypothesis that the 60 kDa heat shock protein 60 (HSP60) reduces cardiovascular fatality during brain stem death via an anti-apoptotic action in the RVLM. In Sprague-Dawley rats maintained under propofol anaesthesia, proteomic or Western blot analysis revealed a progressive augmentation of HSP60 expression in the RVLM after intravenous administration of Escherichia coli lipopolysaccharide (30 mg kg(-1)). Pretreatment with a microinjection of actinomycin D or cycloheximide into bilateral RVLM significantly blunted this HSP60 increase, whereas real-time PCR showed progressive augmentation of hsp60 mRNA. Intriguingly, superimposed on the augmented expression was a progressive decline in mitochondrial, or elevation in cytosolic, HSP60 in ventrolateral medulla. Loss-of-function manipulations in the RVLM using anti-HSP60 antiserum or antisense hsp60 oligonucleotide exacerbated mortality by potentiating the cardiovascular depression during experimental endotoxaemia, alongside intensified nucleosomal DNA fragmentation, elevated cytoplasmic histone-associated DNA fragments or augmented cytochromec-caspase-3 cascade of apoptotic signalling in the RVLM. Immunoprecipitation coupled with immunoblot analysis further revealed a progressive increase in the complex formed between HSP60 and mitochondrial or cytosolic Bax or mitochondrial Bcl-2 during endotoxaemia, alongside a dissociation of the cytosolic HSP60-Bcl-2 complex. We conclude that HSP60 redistributed from mitochondrion to cytosol in the RVLM confers neuroprotection against fatal cardiovascular depression during endotoxaemia via reduced activation of the cytochrome c-caspase-3 cascade of apoptotic signalling through enhanced interactions with mitochondrial or cytosolic Bax or Bcl-2.

Human heat shock protein 60 stimulates vascular smooth muscle cell proliferation through Toll-like receptors 2 and 4

Heat shock proteins (HSPs) of endogenous and exogenous origin are suspected contributors to the initiation and aggravation of vascular pathologies like atherosclerosis and restenosis. Toll-like receptors (TLRs) 2 and 4 are well-known receptors for exogenous pathogen-associated molecular patterns and have recently been thought to play a role in HSP60-induced cellular activation. We hypothesized that human HSP60 directly stimulates venous smooth muscle cell (VSMC) proliferation through a TLR-dependent mechanism. Localization of HSP60, TLR2 and TLR4 was studied in failed venous grafts and normal venous tissue by double immunostaining. In vitro VSMCs were incubated for 48 h with recombinant human HSP60. In other experiments, VSMCs were pre-incubated for 30 min with specific anti-TLR2 and anti-TLR4 antibodies. VSMC proliferation was determined by Ki67 immunoreactivity, and mean values were compared between experimental and control groups. In addition, human embryonic kidney (HEK) cells transfected with human TLR2 or TLR4/MD-2 were exposed to HSP60 for 48 h, and proliferation was determined by using a hemocytometer. Co-localization of HSP60 and TLRs was detected in all neointimal lesions but was virtually absent in normal veins. Human HSP60 stimulated VSMC proliferation in a concentration-dependent fashion. In addition, TLR2 and TLR4 antibodies attenuated VSMC proliferation. The role of TLR-mediated stimulation of cell proliferation by HSP60 was supported by the significant increase in proliferation of transfected HEK cells. These findings provide supporting evidence for the role of HSP60 and TLR2 and TLR4 in vascular disease. Moreover, our data surpass the infection- and autoimmunity-based hypotheses of cardiovascular disease and suggest an additional HSP60-related autocrine process.

Heat shock proteins: endogenous modulators of apoptotic cell death

The highly conserved heat shock proteins (Hsps) accumulate in cells exposed to heat and a variety of other stressful stimuli. Hsps, that function mainly as molecular chaperones, allow cells to adapt to gradual changes in their environment and to survive in otherwise lethal conditions. The events of cell stress and cell death are linked and Hsps induced in response to stress appear to function at key regulatory points in the control of apoptosis. Hsps include anti-apoptotic and pro-apoptotic proteins that interact with a variety of cellular proteins involved in apoptosis. Their expression level can determine the fate of the cell in response to a death stimulus, and apoptosis-inhibitory Hsps, in particular Hsp27 and Hsp70, may participate in carcinogenesis. This review summarizes the apoptosis-regulatory function of Hsps.

Epolactaene binds human Hsp60 Cys442 resulting in the inhibition of chaperone activity

Epolactaene is a microbial metabolite isolated from Penicillium sp., from which we synthesized its derivative ETB (epolactaene tertiary butyl ester). In the present paper, we report on the identification of the binding proteins of epolactaene/ETB, and the results of our investigation into its inhibitory mechanism. Using biotin-labelled derivatives of epolactaene/ETB, human Hsp (heat-shock protein) 60 was identified as a binding protein of epolactaene/ETB in vitro as well as in situ. In addition, we found that Hsp60 pre-incubated with epolactaene/ETB lost its chaperone activity. The in vitro binding study showed that biotin-conjugated epolactaene/ETB covalently binds to Hsp60. In order to investigate the binding site, binding experiments with alanine mutants of Hsp60 cysteine residues were conducted. As a result, it was suggested that Cys442 is responsible for the covalent binding with biotin-conjugated epolactaene/ETB. Furthermore, the replacement of Hsp60 Cys442 with an alanine residue renders the chaperone activity resistant to ETB inhibition, while the alanine replacement of other cysteine residues do not. These results indicate that this cysteine residue is alkylated by ETB, leading to Hsp60 inactivation.

Capture of monomeric refolding intermediate of human muscle creatine kinase

Human muscle creatine kinase (CK) is an enzyme that plays an important physiological role in the energy metabolism of humans. It also serves as a typical model for studying refolding of proteins. A study of the refolding and reactivation process of guanidine chloride-denatured human muscle CK is described in the present article. The results show that the refolding process can be divided into fast and slow folding phases and that an aggregation process competes with the proper refolding process at high enzyme concentration and high temperature. An intermediate in the early stage of refolding was captured by specific protein molecules: the molecular chaperonin GroEL and alpha(s)-casein. This intermediate was found to be a monomer, which resembles the "molten globule" state in the CK folding pathway. To our knowledge, this is the first monomeric intermediate captured during refolding of CK. We propose that aggregation is caused by interaction between such monomeric intermediates. Binding of GroEL with this intermediate prevents formation of aggregates by decreasing the concentration of free monomeric intermediates, whereas binding of alpha(s)-casein with this intermediate induces more aggregation.

Peripheral blood mononuclear cell responses to heat shock proteins in patients undergoing stem cell transplantation

GVHD is a major complication after allogeneic SCT. Etiology of GVHD is multifactorial. Known role of hSPS in antigen presentation could suggest their potential role in the alloreactive process that leads to aGVHD. HSPS represent major immunodominant antigens in a wide spectrum of microbial pathogens. Bacterial and fungal colonization, infection and sepsis are frequent in immunocompromised patients with various malignant and non-malignant diseases. We studied PBMC responses to recombinant human hsp60 (rh-hsp60), rh-hsp70 and Mycobacterium bovis hsp65 (M. bovis hsp65) in relation to aGVHD and infection in 34 pediatric patients with various lympho-hemopoietic malignancies as well as non-malignant disorders subjected to SCT. PBMC of patients before initiation of preparative regimen as well as after engraftment were stimulated with hSPS (1 microg/mL/well, 7-day cultivation). PHA was used as a control of the stimulation ability. Cell responses were measured after the incorporation of 3H-thymidin (pulsing with 1 microCi/well) and were expressed as stimulation indexes (SI). We demonstrated significantly high proliferative response to rh-hsp60 as well as M. bovis hsp65 in a cohort of pretransplant patients with anamnestic and/or actual infection when compared with a cohort of patients without infection and healthy individuals. Strong PBMC cell responses to hSPS were found in patients who were at present colonized with Escherichia coli and Klebsiella pneumoniae or had previously K. pneumoniae infection with subsequent sepsis. Our findings support various studies dealing with immunodominant hSPS in connection with several pathogens and infectious diseases. Although no statistical difference for proliferative response to PHA was observed, PBMC responses against all tested hSPS comparing a cohort of patients with aGVHD and that with no sign of GVHD resulted in significantly lower SI for all tested hSPS in patients with aGVHD. Lower stimulation with hSPS during aGVHD might be explained by the stress-induced upregulation of self-hSPS synthesis that might lead to the inhibition of self-hSPS reactive T-cell response. Vice versa, we hypothesize that increased hsp-specific stimulation may reflect the presence of protecting regulatory T cells preventing the development of Th1-mediated diseases involving aGVHD.

GroEL of Lactobacillus johnsonii La1 (NCC 533) is cell surface associated: potential role in interactions with the host and the gastric pathogen Helicobacter pylori

Heat shock proteins of the GroEL or Hsp60 class are highly conserved proteins essential to all living organisms. Even though GroEL proteins are classically considered intracellular proteins, they have been found at the surface of several mucosal pathogens and have been implicated in cell attachment and immune modulation. The purpose of the present study was to investigate the GroEL protein of a gram-positive probiotic bacterium, Lactobacillus johnsonii La1 (NCC 533). Its presence at the bacterial surface was demonstrated using a whole-cell enzyme-linked immunosorbent assay and could be detected in bacterial spent culture medium by immunoblotting. To assess binding of La1 GroEL to mucins and intestinal epithelial cells, the La1 GroEL protein was expressed in Escherichia coli. We report here that La1 recombinant GroEL (rGroEL) binds to mucins and epithelial cells and that this binding is pH dependent. Immunomodulation studies showed that La1 rGroEL stimulates interleukin-8 secretion in macrophages and HT29 cells in a CD14-dependent mechanism. This property is common to rGroEL from other gram-positive bacteria but not to the rGroEL of the gastric pathogen Helicobacter pylori. In addition, La1 rGroEL mediates the aggregation of H. pylori but not that of other intestinal pathogens. Our in vitro results suggest that GroEL proteins from La1 and other lactic acid bacteria might play a role in gastrointestinal homeostasis due to their ability to bind to components of the gastrointestinal mucosa and to aggregate H. pylori.

Hindlimb unloading increases muscle content of cytosolic but not nuclear Id2 and p53 proteins in young adult and aged rats

This study tested the hypothesis that inhibitor of differentiation-2 (Id2), p53, and heat shock proteins (HSP) are responsive to suspension-induced muscle atrophy. Fourteen days of hindlimb suspension were used to unload the hindlimbs and induce atrophy in gastrocnemius muscles of young adult and aged rats. Following suspension, medial gastrocnemius muscle wet weight was reduced by approximately 30%, and the muscle wet weight normalized to the animal body weight decreased by 11 and 15% in young adult and aged animals, respectively. mRNA abundances of Id2, p53, HSP70-2, and HSP27 did not change with suspension, whereas HSP70-1 mRNA content was lower in the suspended muscle compared with the control muscle in both young adult and aged animals. Our immunoblot analyses indicated that protein expressions of HSP70 and HSP60 were not different between suspended and control muscles in both ages, whereas HSP27 protein content was increased in suspended muscle relative to control muscle only in young adult animals. Id2 and p53 protein contents were elevated in the cytosolic fraction of suspended muscle compared with the control muscle in both young and aged animals, but these changes were not found in the nuclear protein fraction. Furthermore, compared with young adult, aged muscles had a lower HSP70-1 mRNA content but higher HSP70-2 mRNA content and protein contents of Id2, p53, HSP70, and HSP27. These findings are consistent with the hypothesis that Id2 and p53 are responsive to unloading-induced muscle atrophy. Moreover, our data indicate that aging is accompanied with altered abundances of HSP70-1 and HSP70-2 mRNA, in addition to Id2, p53, HSP70, and HSP27 protein in rat gastrocnemius muscle.

Chaperonin GroEL meets the substrate protein as a "load" of the rings

Chaperonin GroEL is an essential molecular chaperone that assists protein folding in the cell. With the aid of cochaperonin GroES and ATP, double ring-shaped GroEL encapsulates non-native substrate proteins inside the cavity of the GroEL-ES complex. Although extensive studies have revealed the outline of GroEL mechanism over the past decade, central questions remain: What are the in vivo substrate proteins? How does GroEL encapsulate the substrates inside the cavity in spite of an apparent entropic difficulty? Is the folding inside the GroEL-ES cavity the same as bulk spontaneous folding? In this review I summarize the recent progress on in vivo and in vitro aspects of GroEL. In particular, emerging evidence shows that the substrate protein itself influences the chaperonin GroEL structure and reaction cycle. Finally I propose the mechanistic similarity between GroEL and kinesin, a molecular motor that moves along a microtubule in an ATP-dependent manner.

A nonconserved carboxy-terminal segment of GroEL contributes to reaction temperature

The role of the C-terminal segment of the GroEL equatorial domain was analyzed. To understand the molecular basis for the different active temperatures of GroEL from three bacteria, we constructed a series of chimeric GroELs combining the C-terminal segment of the equatorial domain from one species with the remainder of GroEL from another. In each case, the foreign C-terminal segment substantially altered the active temperature range of the chimera. Substitution of L524 of Escherichia coli GroEL with the corresponding residue (isoleucine) from psychrophilic GroEL resulted in a GroE with approximately wild-type activity at 25 degrees C, but also at 10 degrees C, a temperature at which wild-type E. coli GroE is inactive. In a detailed look at the temperature dependence of the GroELs, normal E. coli GroEL and the L524I mutant became highly active above 14 degrees C and 12 degrees C respectively. Similar temperature dependences were observed in a surface plasmon resonance assay of GroES binding. These results suggested that the C-terminal segment of the GroEL equatorial domain has an important role in the temperature dependence of GroEL. Moreover, E. coli acquired the ability to grow at low temperature through the introduction of cold-adapted chimeric or L524I mutant groEL genes.

Low temperature of GroEL/ES overproduction permits growth of Escherichia coli cells lacking trigger factor DnaK

Escherichia coli trigger factor (TF) and DnaK cooperate in the folding of newly synthesized proteins. The combined deletion of the TF-encoding tig gene and the dnaK gene causes protein aggregation and synthetic lethality at 30 degrees C. Here we show that the synthetic lethality of deltatigdeltadnaK52 cells is abrogated either by growth below 30 degrees C or by overproduction of GroEL/GroES. At 23 degrees C deltatigdeltadnaK52 cells were viable and showed only minor protein aggregation. Overproduction of GroEL/GroES, but not of other chaperones, restored growth of deltatigdeltadnaK52 cells at 30 degrees C and suppressed protein aggregation including proteins >/= 60 kDa, which normally require TF and DnaK for folding. GroEL/GroES thus influences the folding of proteins previously identified as DnaK/TF substrates.

Monitoring macromolecular complexes involved in the chaperonin-assisted protein folding cycle by mass spectrometry

We have used native mass spectrometry to analyze macromolecular complexes involved in the chaperonin-assisted refolding of gp23, the major capsid protein of bacteriophage T4. Adapting the instrumental methods allowed us to monitor all intermediate complexes involved in the chaperonin folding cycle. We found that GroEL can bind up to two unfolded gp23 substrate molecules. Notably, when GroEL is in complex with the cochaperonin gp31, it binds exclusively one gp23. We also demonstrated that the folding and assembly of gp23 into 336-kDa hexamers by GroEL-gp31 can be monitored directly by electrospray ionization mass spectrometry (ESI-MS). These data reinforce the great potential of ESI-MS as a technique to investigate structure-function relationships of protein assemblies in general and the chaperonin-protein folding machinery in particular. A major advantage of native mass spectrometry is that, given sufficient resolution, it allows the analysis at the picomole level of sensitivity of heterogeneous protein complexes with molecular masses up to several million daltons.

Two of the three groEL homologues in Rhizobium leguminosarum are dispensable for normal growth

Although many bacteria contain only a single groE operon encoding the essential chaperones GroES and GroEL, examples of bacteria containing more than one groE operon are common. The root-nodulating bacterium Rhizobium leguminosarum contains at least three operons encoding homologues to Escherichia coli GroEL, referred to as Cpn60.1, Cpn60.2 and Cpn60.3, respectively. We report here a detailed analysis of the requirement for and relative levels of these three proteins. Cpn60.1 is present at higher levels than Cpn60.2, and Cpn60.3 protein could not be detected under any conditions although the cpn60.3 gene is transcribed under anaerobic conditions. Insertion mutations could not be constructed in cpn60.1 unless a complementing copy was present, showing that this gene is essential for growth under the conditions used here. Both cpn60.2 and cpn60.3 could be inactivated with no loss of viability, and a double cpn60.2 cpn60.3 mutant was also constructed which was fully viable. Thus only Cpn60.1 is required for growth of this organism.

HSP60 and CpG-DNA-oligonucleotides differentially regulate LPS-tolerance of hepatic Kupffer cells

BACKGROUND/AIMS

Hepatic Kupffer cells (KC) are major regulators of the immune response to gut-derived bacterial products; uncontrolled activation of KC by bacterial components is of pathogenic relevance in alcoholic hepatitis and septic shock.

METHODS

We examined the role of bacterial lipopolysaccharide (LPS), bacterial and autologous HSP60 and bacterial DNA, which are recognized by innate Toll-like receptors, during activation of murine KC.

RESULTS

In cultivated KC, autologous HSP60 induced a state of LPS-hyporesponsiveness; bacterial DNA did not mitigate the response to subsequent LPS-challenge in vitro; in contrast, pre-treatment of mice with bacterial DNA even significantly increased serum TNF levels, liver function tests and mortality in a model of LPS-induced hemorrhagic liver failure.

CONCLUSION

HSP60 and CpG-DNA differentially modulated the threshold of KC activation by LPS and might therefore contribute to the regulation of inflammatory immunity to gut-derived bacterial compounds.