Overexpression of HSP10 correlates with HSP60 and Mcl-1 levels and predicts poor prognosis in non-small cell lung cancer patients

BACKGROUND

HSP60 and its partner HSP10 are members of heat shock proteins (HSPs) family, which help mitochondrial protein to fold correctly. Mcl-1, a member of the Bcl-2 family, plays a crucial role in regulation of cell apoptosis. Aberrant expression of HSP10, HSP60 and Mcl-1 is involved in the development of many tumors.

OBJECTIVE

To examine the association between expression of HSP10, HSP60 and Mcl-1 and clinicopathological features of non-small cell lung cancer (NSCLC).

METHODS

Tissue microarrays including 53 non-cancerous lung tissues (Non-CLT) and 354 surgically resected NSCLC were stained with anti-HSP10, anti-HSP60 and anti-Mcl-1 antibodies respectively by immunohistochemistry.

RESULTS

Higher expression of HSP10, HSP60 and Mcl-1 was found in NSCLC compared with Non-CLT. Both individual and combined HSP10 and HSP60 expression in patients with clinical stage III was higher than that in stage I ∼ II. Expression of HSP10 showed a positive correlation with HSP60 and Mcl-1. Overall survival time of NSCLC patients was remarkably shorter with elevated expression of HSP10, HSP60 and Mcl-1 alone and in combination. Moreover overexpression of HSP10 and Mcl-1 was poor independent prognostic factor for lung adenocarcinoma patients.

CONCLUSIONS

High expression of HSP10, HSP60 and Mcl-1 might act as novel biomarker of poor prognosis for NSCLC patients.

Stress response of a clinical Enterococcus faecalis isolate subjected to a novel antimicrobial surface coating

Emerging antibiotic resistance among pathogenic bacteria, paired with their ability to form biofilms on medical and technical devices, represents a serious problem for effective and long-term decontamination in health-care environments and gives rise to an urgent need for new antimicrobial materials. Here we present the impact of AGXX^®, a novel broad-spectrum antimicrobial surface coating consisting of micro-galvanic elements formed by silver and ruthenium, on the transcriptome of Enterococcus faecalis. A clinical E. faecalis isolate was subjected to metal stress by growing it for different periods in presence of the antimicrobial coating or silver-coated steel meshes. Subsequently, total RNA was isolated and next-generation RNA sequencing was performed to analyze variations in gene expression in presence of the antimicrobial materials with focus on known stress genes. Exposure to the antimicrobial coating had a large impact on the transcriptome of E. faecalis. After 24min almost 1/5 of the E. faecalis genome displayed differential expression. At each time-point the cop operon was strongly up-regulated, providing indirect evidence for the presence of free Ag⁺-ions. Moreover, exposure to the antimicrobial coating induced a broad general stress response in E. faecalis. Genes coding for the chaperones GroEL and GroES and the Clp proteases, ClpE and ClpB, were among the top up-regulated heat shock genes. Differential expression of thioredoxin, superoxide dismutase and glutathione synthetase genes indicates a high level of oxidative stress. We postulate a mechanism of action where the combination of Ag⁺-ions and reactive oxygen species generated by AGXX^® results in a synergistic antimicrobial effect, superior to that of conventional silver coatings.

Improving the productivity of recombinant protein in Escherichia coli under thermal stress by coexpressing GroELS chaperone system

Here, we demonstrate that the overexpression of the GroELS chaperone system, which assists the folding of intracellular proteins and prevents aggregation of its biological targets, can enhance the thermotolerance of Escherichia coli strains and facilitate the production of recombinant protein under thermal stress. The overexpression of GroELS led to an about 2-fold higher growth rate of E. coli XL-1 blue than control at 45 degrees and induced the growth of the strain even at 50 degrees , although the growth was not sustained in the second-round culture. The effect of GroELS overexpression was also effective on other E. coli strains such as JM109, DH5alpha, and BL21. Finally, we have shown that coexpression of GroELS allows us to produce recombinant protein even at 50 degrees , a temperature at which the protein production based on E. coli is not efficient. This study indicates that the employment of the GroELS overexpression system can expand the range of environmental conditions for E. coli.

Rational engineering of human cytochrome P450 2B6 for enhanced expression and stability: importance of a Leu264->Phe substitution

Despite the emerging importance of human P450 2B6 in xenobiotic metabolism, thorough biochemical and biophysical characterization has been impeded as a result of low expression in Escherichia coli. Comparison with similar N-terminal truncated and C-terminal His-tagged constructs (rat P450 2B1dH, rabbit 2B4dH, and dog 2B11dH) revealed that P450 2B6dH showed the lowest thermal stability, catalytic tolerance to temperature, and chemical stability against guanidinium chloride-induced denaturation. Eleven P450 2B6dH mutants were rationally engineered based on sequence comparison with the three other P450 2B enzymes and the solvent accessibility of residues in the ligand-free crystal structure of P450 2B4dH. L198M, L264F, and L390P showed approximately 3-fold higher expression than P450 2B6dH. L264F alone showed enhanced stability against thermal and chemical denaturation compared with P450 2B6dH and was characterized further functionally. L264F showed similar preferential inhibition by pyridine over imidazole derivatives as P450 2B6dH. The Leu(264)-->Phe substitution did not alter the K(s) for inhibitors or the substrate benzphetamine, the K(m) for 7-ethoxy-4-(trifluoromethyl)coumarin, or the benzphetamine metabolite profiles. The enhanced stability and monodisperse nature of L264F made it suitable for isothermal titration calorimetry studies. Interaction of 1-benzylimidazole with L264F yielded a clear binding isotherm with a distinctly different thermodynamic signature from P450 2B4dH. The inhibitor docked differently in the binding pocket of a P450 2B6 homology model than in 2B4, highlighting the different chemistry of the active site of these two enzymes. Thus, L264F is a good candidate to further explore the unique structure-function relationships of P450 2B6 using X-ray crystallography and solution thermodynamics.

The proteomic alterations of Thermoanaerobacter tengcongensis cultured at different temperatures

Thermoanaerobacter tengcongensis, one of many thermophilic organisms, survives harsh living conditions in temperatures ranging from 50 to 80 degrees C. In this comprehensive analysis, we present a robust approach, 2-DE and MALDI-TOF MS, to compare and identify the bacterial proteins responding to the temperature stress. In total, 164 spots of 2-DE were found with the significant changes in spot volume at three culture temperatures, 55, 75, and 80 degrees C, respectively; furthermore, 87 unique proteins were characterized by MS. Our results reveal that the electrophoretic images of the bacterial proteins, extracted from two culture temperatures (55 and 75 degrees C), had similar patterns; however, the bacteria cultured at 80 degrees C had dramatically decreased their spot volumes. Additionally, the temperature-sensitive proteins are broadly divided into two groups: specific expression at certain temperatures and consistent changes of expression responsive to temperature. For instance, three proteins closely related with redox regulation, dihydrolipoamide acyltransferase, NADH:ubiquinone oxidoreductase, and ferredoxin, were only detected in the bacteria cultured at 55 degrees C. Whereas, two chaperonins, GroES and GroEL, were found to show a consistent increase during the elevated temperatures with the determinations, either by MS or Western blot. The proteomic information, thus expedites our understanding of the molecular mechanisms regarding how thermophilic bacteria adapt to the alterations in living environment.

Inclusion body anatomy and functioning of chaperone-mediated in vivo inclusion body disassembly during high-level recombinant protein production in Escherichia coli

During production in recombinant Escherichia coli, the human basic fibroblast growth factor (hFGF-2) partly aggregates into stable cytoplasmic inclusion bodies. These inclusion bodies additionally contain significant amounts of the heat-shock chaperone DnaK, and putative DnaK substrates such as the elongation factor Tu (ET-Tu) and the metabolic enzymes dihydrolipoamide dehydrogenase (LpdA), tryptophanase (TnaA), and d-tagatose-1,6-bisphosphate aldolase (GatY). Guanidinium hydrochloride induced disaggregation studies carried out in vitro on artificial aggregates generated through thermal aggregation of purified hFGF-2 revealed identical disaggregation profiles as hFGF-2 inclusion bodies indicating that the heterogenic composition of inclusion bodies did not influence the strength of interactions of hFGF-2 in aggregates formed in vivo as inclusion bodies compared to those generated in vitro from native and pure hFGF-2 through thermal aggregation. Compared to unfolding of native hFGF-2, higher concentrations of denaturant were required to dissolve hFGF-2 aggregates showing that more energy is required for disruption of interactions in both types of protein aggregates compared to the unfolding of the native protein. In vivo dissolution of hFGF-2 inclusion bodies was studied through coexpression of chaperones of the DnaK and GroEL family and ClpB and combinations thereof. None of the chaperone combinations was able to completely prevent the initial formation of inclusion bodies, but upon prolonged incubation mediated disaggregation of otherwise stable inclusion bodies. The GroEL system was particularly efficient in inclusion body dissolution but did not lead to a corresponding increase in soluble hFGF-2 rather was promoting the proteolysis of the recombinant growth factor. Coproduction of the disaggregating DnaK system and ClpB in conjunction with small amounts of the chaperonins GroELS was most efficient in disaggregation with concomitant formation of soluble hFGF-2. Thus, fine-balanced coproduction of chaperone combinations can play an important role in the production of soluble recombinant proteins with a high aggregation propensity not through prevention of aggregation but predominantly through their disaggregating properties.

An improved strategy for high-level production of TEV protease in Escherichia coli and its purification and characterization

Because of its stringent sequence specificity, tobacco etch virus (TEV) protease emerges as a useful reagent with wide application in the cleavage of recombinant fusion proteins. However, the solubility of TEV protease expressed in Escherichia coli is extremely low. In the present study, we introduced a more efficient system to improve and facilitate the soluble production of TEV protease in E. coli. Optimal expression of soluble His6-TEV was achieved by examining the contribution of chaperone co-expression and lower temperature fermentation. When further purified by Ni(2+) affinity chromatography, 65mg of His6-TEV was isolated with purity over 95% from 1L of culture. The enzyme activity of His6-TEV was generally characterized by using GST-EGFP and His6-L-TNF fusion protein as substrates, which contained a TEV cleavage site between two moieties.

Detection and identification of heat shock protein 10 as a biomarker in colorectal cancer by protein profiling

Although colorectal cancer is one of the best-characterized tumors with regard to the multistep progression, it remains one of the most frequent and deadly neoplasms. For a better understanding of the molecular mechanisms behind the process of tumorigenesis and tumor progression, changes in protein expression between microdissected normal and tumorous colonic epithelium were analyzed. Cryostat sections from colorectal tumors, adenoma tissue, and adjacent normal mucosa were laser-microdissected and analyzed using ProteinChip Arrays. The derived MS profiles exhibited numerous statistical differences. One peak showing significantly high expression in the tumor was purified by reverse-phase chromatography and SDS-PAGE. The protein band of interest was passively eluted from the gel and identified as heat shock protein 10 (HSP 10) by tryptic digestion, peptide mapping, and MS/MS analysis. This tumor marker was further characterized by immunohistochemistry. Analysis of HSP 10-positive tissue by ProteinChip technology confirmed the identity of this protein. This work demonstrates that biomarker in colorectal cancer can be detected, identified, and assessed by a proteomic approach comprising tissue microdissection, protein profiling, and immunological techniques. In our experience, histological defined microdissected tissue areas should be used to identify proteins that might be responsible for tumorigenesis.

HSP-10 in ovarian cancer: expression and suppression of T-cell signaling

OBJECTIVE

Suppressed T-cell activation is a hallmark of advanced ovarian cancer. Studies in pregnancy have demonstrated similar T-cell dysfunction mediated, at least in part, by HSP10, identified as "early pregnancy factor." This pilot study addresses the presence of HSP10 in the circulation of ovarian cancer patients and assesses its role in suppressing CD3-zeta.

METHODS

Sera were obtained from ovarian cancer patients (n = 10) and age-matched noncancer-bearing female controls (n = 9). HSP10 presence was determined semiquantitatively by Western immunoblotting in sera, ascites, and ovarian tumor cell conditioned media. The consequences of HSP10 on CD3-zeta suppression were defined using a Jurkat cell bioassay, using unfractionated patient sera, sera with HSP10 removed by immunoprecipitation and the immunoprecipitate.

RESULTS

HSP10 was detected in both sera and ascites of patients with ovarian cancer; however, it was not detectable in controls. HSP10 was also detected in the culture media of ovarian tumor cells. Sera containing HSP10 suppressed T-cell CD3-zeta expression, which correlated with HSP10 levels (r2 = 0.839). When HSP10 was removed from the sera, the ability to suppress CD3-zeta was diminished and the immunoprecipitated material was capable of suppressing CD3-zeta.

CONCLUSIONS

HSP10 appears to be produced and released from ovarian tumor cells and is detectable in the peripheral blood and ascites of patients. This circulating HSP10 appears to suppress T-cell expression of CD3-zeta, a key component of T-cell activation. Our findings indicate that, as in pregnancy, production and release of HSP10 may be a critical factor in the suppression of T-cell activation, allowing the tumor to escape immune surveillance.

Expression, purification, and characterization of a novel recombinant fusion protein, rhTPO/SCF, in Escherichia coli

Thrombopoietin (TPO) is the principal regulatory cytokine of megakaryopoiesis and thrombopoiesis and promotes all aspects of megakaryocyte development. Stem cell factor (SCF) is mainly a pleiotropic cytokine acting on hematopoiesis by promoting the survival and proliferation of hematopoietic stem cells and has a potent synergistic effect on megakaryopoiesis in the presence of TPO. Here, we report the construction, expression, and purification of a novel recombinant human thrombopoietin/stem cell factor (rhTPO/SCF) fusion protein, which consists of a truncated human thrombopoietin (1-157 a.a.) plus a truncated human stem cell factor (1-145 a.a.), linked by a peptide (GGGGSPGGSGGGGSGG). The TPO/SCF gene was cloned into the Escherichia coli expression vector pET28a and expressed in BL21(DE3) strain. The rhTPO/SCF constituted up to 6% of the total bacterial protein. Co-expression with E. coli chaperones, Trigger Factor (TF) and GroES/GroEL, and lowering cultivation temperature cooperatively improved the solubility of expressed rhTPO/SCF, resulting in about fourfold increase in the yield soluble rhTPO/SCF. The rhTPO/SCF was purified to homogeneity using anion exchange followed by metal affinity chromatography. Western blot analysis confirmed the identity of the purified protein. rhTPO/SCF stimulated a dose-dependent cell proliferation in both TF1 and Mo7e cell lines.

Improvement in the expression of CYP2B6 by co-expression with molecular chaperones GroES/EL in Escherichia coli

Improvement of CYP2B6 expression was examined by co-expression with molecular chaperones GroES/EL. Although a CO-reduced difference spectrum was not detected in Escherichia coli transformed only by the CYP2B6-expressing vector, co-expression of GroES/EL resulted in high-level expression which reached over 2000 nmol P450/L. CYP2B6 was purified from the E. coli membrane with a high yield. Purified CYP2B6 showed 7-ethoxy-4-trifluoromethylcoumarin O-deethylase activity in a reconstitution system. This expression system would be useful for the production of large amounts of active CYP2B6 and for the detailed analysis of the enzyme.

The expression of HSP60 and HSP10 in large bowel carcinomas with lymph node metastase

Background

The involvement of Heat Shock Proteins (HSP) in cancer development and progression is a widely debated topic. The objective of the present study was to evaluate the presence and expression of HSP60 and HSP10 in a series of large bowel carcinomas and locoregional lymph nodes with and without metastases.

Methods

82 Astler and Coller's stage C2 colorectal cancers, of which 48 well-differentiated and 34 poorly-differentiated, were selected along with 661 lymph nodes, including 372 with metastases and 289 with reactive hyperplasia only, from the same tumours. Primitive tumours and both metastatic and reactive lymph nodes were studied; specifically, three different compartments of the lymph nodes, secondary follicle, paracortex and medullary sinus, were also analysed. An immunohistochemical research for HSP60 and HSP10 was performed and the semiquantitative results were analysed by statistical analysis to determine the correlation between HSPs expression and 1) tumour grading; 2) degree of inflammation; 3) number of lymph nodes involved; 4) lymph node compartment hyperplasia. Moreover, western blotting was performed on a smaller group of samples to confirm the immunohistochemical results.

Results

Our data show that the expression of HSP60, in both primary tumour and lymph node metastasis, is correlated with the tumoral grade, while the HSP10 expression is not. Nevertheless, the levels of HSP10 are commonly higher than the levels of HSP60. In addition, statistical analyses do not show any correlation between the degree of inflammation and the immunopositivity for both HSP60 and HSP10. Moreover, we find a significant correlation between the presence of lymph node metastases and the positivity for both HSP60 and HSP10. In particular, metastatic lymph nodes show a higher percentage of cells positive for both HSP60 and HSP10 in the secondary follicles, and for HSP10 in the medullary sinuses, when compared with hyperplastic lymph nodes.

Conclusion

HSP60 and HSP10 may have diagnostic and prognostic significance in the management of this tumour and their overexpression in tumoral cells may be functionally related to tumoral progression. We hypothesise that their expression in follicular and medullary cells of lymph nodes may be induced by formation of metastases. Further studies based on these observations could lead to a better understanding of the HSPs involvement in colorectal cancer progression, as well as other neoplasms.

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.

Purification and characterization of mouse CYP27B1 overproduced by an Escherichia coli system coexpressing molecular chaperonins GroEL/ES

The expression of mouse CYP27B1 in Escherichia coli has been dramatically enhanced by coexpression of GroEL/ES. To reveal the enzymatic properties of CYP27B1, we measured its hydroxylation activity toward vitamin D3 and 1alpha-hydroxyvitamin D3 (1alpha(OH)D3) in addition to the physiological substrate 25(OH)D3. Surprisingly, CYP27B1 converted vitamin D3 to 1alpha,25(OH)D3. Both 1alpha-hydroxylation activity toward vitamin D3, and 25-hydroxylation activity toward 1alpha(OH)D3 were observed. The Km and Vmax values for 25-hydroxylation activity toward 1alpha(OH)D3 were estimated to be 1.7 microM and 0.51 mol/min/mol P450, respectively, while those for 1alpha-hydroxylation activity toward 25(OH)D3 were 0.050 microM and 2.73 mol/min/mol P450, respectively. Note that the substrate must be fixed in the opposite direction in the substrate-binding pocket of CYP27B1 between 1alpha-hydroxylation and 25-hydroxylation. Based on these results and the fact that human CYP27A1 and Streptomyces CYP105A1 also convert vitamin D3 to 1alpha,25(OH)D3, 1alpha-hydroxylation, and 25-hydroxylation of vitamin D3 appear to be closely linked together.

Transcriptional analysis of the groES-groEL1, groEL2, and dnaK genes in Corynebacterium glutamicum: characterization of heat shock-induced promoters

The appropriate conditions to switch on the heat shock promoters in Corynebacterium glutamicum were defined by Northern blot analysis. Transcriptional patterns were characterized for the groEL2 gene and the groES-groEL1 and dnaK operons. Transcriptional start points of these genes were determined by primer extension analysis, allowing the identification of CIRCE and HAIR boxes close to the -10 and -35 regions of the promoters. The presence of both CIRCE and HAIR sequences within a single promoter (P-groEL2) in bacteria is described for the first time. In addition, the dnaK promoter showed -10 and -35 sequences similar to those recognized by SigH of Mycobacterium and SigR of Streptomyces close to a second transcription start region with -10 and -35 boxes typical of promoters for housekeeping genes.

Tight binding of deoxyribonucleotide triphosphates to human thymidine kinase 2 expressed in Escherichia coli. Purification and partial characterization of its dimeric and tetrameric forms

Human thymidine kinase 2 (hTK2) phosphorylates pyrimidine deoxyribonucleosides to the corresponding nucleoside monophosphates, using a nucleotide triphosphate as a phosphate donor. In this study, hTK2 was cloned and expressed at high levels in Escherichia coli as a fusion protein with maltose-binding protein. Induction of a heat-shock response by ethanol and coexpression of plasmid-encoded GroEL/ES chaperonins at 28 degrees C minimized the nonspecific aggregation of the hybrid protein and improved the recovery of three homooligomeric forms of the properly folded enzyme, i.e., dimer > tetramer > hexamer. The dimer and the tetramer were isolated in stable and highly purified forms after proteolytic removal of the fusion partner. Both oligomers contained a substoichiometric amount of deoxyribonucleotide triphosphates (dTTP > dCTP > dATP), known to be strong feedback inhibitors of the enzyme. Steady-state kinetic studies were consistent with the presence of endogenous inhibitors, and both oligomeric forms revealed a lag phase of at least approximately 5 min, which was abolished on preincubation with substrate (dThd or dCyd). The rather similar kinetic properties of the two oligomeric forms indicate that the basic functional unit is a dimer. Molecular docking experiments with a modeled hTK2 three-dimensional structure accurately predicted the binding positions at the active site of the natural substrates (dThd, dCyd, and ATP) and inhibitors (dTTP and dCTP), with highly conserved orientations obtained for all ligands. The calculated relative nonbonded interaction energies are in agreement with the biochemical data and show that the inhibitor complexes have lower stabilization energies (higher affinity) than the substrates.

DnaK and DnaJ facilitated the folding process and reduced inclusion body formation of magnesium transporter CorA overexpressed in Escherichia coli

Overexpression of CorA, the major magnesium transporter from bacterial inner membrane, in Escherichia coli resulted in the synthesis of 60mg of protein per liter of culture, most of which however was in the form of inclusion bodies. The levels of inclusion body formation were reduced by lowering the cell culture temperature. To dissect CorA inclusion body formation and the folding process involved, we co-expressed the protein with various chaperones and other folding modulators. Expression of DnaK/DnaJ (Hsp70) prevented inclusion bodies from forming and resulted in the integration of more CorA into the membrane. GroEL/GroES (Hsp60/Hsp10) were less effective at reducing CorA inclusion body formation. Co-expression with either Ffh/4.5S-RNA, the signal recognition particle, or SecA, the ATPase that drives protein insertion into the membrane, had little effect on CorA folding. These results indicate: (1) that CorA inclusion bodies form immediately after synthesis at 37 degrees C, (2) that CorA solubility in the cytosol can be increased by co-expressing a chaperone system, (3) membrane targeting is probably not a rate-limiting factor, and (4) that membrane insertion becomes a limitation only when large amounts of soluble CorA are present in the cytosol. These co-expression systems can be used for producing other membrane proteins in large quantities.

Low temperature or GroEL/ES overproduction permits growth of Escherichia coli cells lacking trigger factor and 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.

Consortium of fold-catalyzing proteins increases soluble expression of cyclohexanone monooxygenase in recombinant Escherichia coli

The cyclohexanone monooxygenase ( CHMO) gene of Acinetobacter sp. NCIMB 9871 was simultaneously expressed with the genes encoding molecular chaperones and foldases in Escherichia coli. While the expression of the CHMO gene alone resulted in the formation of inclusion bodies, coexpression of the chaperone or foldase genes remarkably increased the production of soluble CHMO enzyme in recombinant E. coli. Furthermore, it was found that molecular chaperones were more beneficial than foldases for enhancing active CHMO enzyme production. The recombinant E. coli strain simultaneously expressing the genes for CHMO, GroEL/GroES and DnaK/DnaJ/GrpE showed a specific CHMO activity of 111 units g(-1) cell protein, corresponding to a 38-fold enhancement in CHMO activity compared with the control E. coli strain expressing the CHMO gene alone.

Identification of proteins induced at low pH in Lactococcus lactis

The Gram-positive bacterium Lactococcus lactis is of major importance to the dairy industry due to its conversion of lactose to lactic acid leading to the acidification of milk. To investigate which proteins are induced when L. lactis is exposed to conditions of low pH, we used two-dimensional gel electrophoresis to follow how protein expression changes with the degree of acidification. We found that reducing the pH of the growth medium with hydrochloric acid induced the synthesis of a small subset of proteins. The majority of these proteins were induced both after a minor (pH 5.5) and a major (pH 4.5) reduction in pH. Among the most strongly induced proteins, we identified the oxidative stress proteins superoxide dismutase and alkylhydroperoxidase as well as the autoinducer synthesis protein, LuxS. We also observed a differential induction of heat shock proteins by low pH as members of the CtsR regulon, ClpE and ClpP were induced at both pH 5.5 and 4.5, while HrcA-regulated chaperones, GroEL, GroES, DnaK and GrpE were induced only at pH 4.5. In addition, we identified two proteins repressed by low pH that proved to be the L. lactis HPr protein of the phosphoenolpyruvate sugar phosphotransferase system and the trigger factor known to participate in the folding of newly synthesized polypeptides.

Phylogenetic reconstruction of Gram-positive organisms based on comparative sequence analysis of molecular chaperones from the ruminal microorganismRuminococcus flavefaciensFD-1

Primers designed on the basis of nucleotide sequences conserved in DnaK and GroEL from Gram-positive organisms were used to PCR amplify internal regions of the cognate genes from the anaerobic ruminal cellulolytic bacterium Ruminococcus flavefaciens FD-1. Genome walking was then utilized to elucidate the remainder of the sequences in addition to upstream and downstream regions. The full sequence of the gene encoding the GroES protein (groES) was found directly upstream from groEL. The deduced amino acid sequence of the groEL gene showed the highest homology with the amino acid sequence of the Clostridium thermocellum GroEL protein (72% amino acid identity). Similarly, translation of the groES nucleotide sequence showed highest homology to the C. thermocellum GroES protein (61% amino acid identity). Analysis of the upstream region of this chaperonin operon revealed a CIRCE regulatory element 45 bp upstream from the putative start of the groES ORF. The deduced amino acid sequence of the putative dnaK gene showed the highest homology with the amino acid sequence of the Clostridium acetobutylicum DnaK protein (68% amino acid identity). Phylogenetic analyses based on the translated sequences reiterate this relationship between R. flavefaciens and the Clostridia. However, when the nucleotide sequences of Gram-positive organisms are analyzed, a different topology occurs of the relationship between high- and low-G+C Gram-positive organisms to the 16S rRNA interpretation.

Immunohistochemical evaluation of PCNA, p53, HSP60, HSP10 and MUC-2 presence and expression in prostate carcinogenesis

BACKGROUND

The study of the expression of different biological markers in non-neoplastic, pre-neoplastic and neoplastic lesions of prostate could help to better understand their role in carcinogenesis and to find new diagnostic and prognostic tools.

MATERIALS AND METHODS

In the present work we evaluated, by immunohistochemistry, the presence and the expression of PCNA, p53, HSP60, HSP10 and MUC-2 in a series of nodular hyperplasia, low- and high-grade prostatic intraepithelial lesions and adenocarcinomas.

RESULTS

Our data confirmed that: 1) PCNA expression could be related to the grade of progression of cancer; and that 2) p53 mutation could be a late event in prostate carcinogenesis. Moreover, we reported that: 1) HPS60 and HPS10 were overexpressed early in prostate carcinogenesis; and that 2) MUC-2 is absent in both tumoral and non-tumoral prostatic tissue.

CONCLUSION

We suggest the further examination, by molecular and genetic studies, of the role of HSP60 and HSP10 during carcinogenesis of the prostate as well as of other organs.

A mitochondrial specific stress response in mammalian cells

Cells respond to a wide variety of stresses through the transcriptional activation of genes that harbour stress elements within their promoters. While many of these elements are shared by genes encoding proteins representative of all subcellular compartments, cells can also respond to stresses that are specific to individual organelles, such as the endoplasmic reticulum un folded protein response. Here we report on the discovery and characterization of a mitochondrial stress response in mammalian cells. We find that the accumulation of unfolded protein within the mitochondrial matrix results in the transcriptional upregulation of nuclear genes encoding mitochondrial stress proteins such as chaperonin 60, chaperonin 10, mtDnaJ and ClpP, but not those encoding stress proteins of the endoplasmic reticulum. Analysis of the chaperonin 60/10 bidirectional promoter identified a CHOP element as the mitochondrial stress response element. Dominant-negative mutant forms of CHOP and overexpression of CHOP revealed that this transcription factor, in association with C/EBPbeta, regulates expression of mitochondrial stress genes in response to the accumulation of unfolded proteins.

Expression of active human C1 inhibitor serpin domain in Escherichia coli

Human C1 inhibitor is a highly glycosylated serine protease inhibitor of the serpin family. The protein contains two disulfide bonds. In this study, an N-terminally truncated form of recombinant C1 inhibitor was overexpressed in Escherichia coli strains BL21(DE3) and AD494(DE3), the latter enabling the formation of disulfide bonds within the cytoplasm. With both strains, a major fraction of the recombinant protein produced appeared to be insoluble. However, the soluble fraction of lysates from strain AD494(DE3) inhibited the C1s target protease in functional assays. Recombinant C1 inhibitor produced in this strain also displayed the ability to complex with C1s in vitro. In contrast, lysates from strain BL21(DE3) displayed no C1 inhibitor activity. These data support the notion that glycosylation is not important, whereas disulfide bond formation appears to be essential for the production of an active recombinant C1 inhibitor. Thus, bacterial strains that permit the formation of disulfide bonds may represent a reliable system for the production of recombinant C1 inhibitor. However, a major obstacle to large-scale production will be to produce the protein in a soluble form. Attempts to increase the yield of soluble protein by coexpression of the GroEL/ES chaperonins resulted in an increase in solubility.

Production and purification of SV40 major capsid protein (VP1) in Escherichia coli strains deficient for the GroELS chaperone machine

Production of the major capsid protein of SV40, VP1, is of great interest for the study on capsid assembly in vitro. Production of soluble His6-VP1 in Escherichia coli strains deficient in the GroELS chaperone machine was substantially higher than in the wild-type strain. The His6-VP1 produced in a groEL mutant strain was readily purified. The protein was able to form higher-order structures as evidenced by analysis of the soluble fraction by gel filtration, by sedimentation in sucrose gradient, and by electron microscopy. We propose the use of groE mutants for the production of the major capsid protein of SV40 and perhaps also other papovaviruses.