ERp29 inhibition attenuates TCA toxicity via affecting p38/p53- dependent pathway in human trophoblast HTR-8/SVeno cells

Intrahepatic cholestasis of pregnancy (ICP) is a liver disorder occurred in pregnant women, and the mechanism for such disease is still unclear. The bioinformatics analysis of our previous study has revealed the abnormal expression of endoplasmic reticulum protein 29 (ERp29) in placental tissue of ICP patients. In this study, the function of ERp29 was further explored using in vitro model of ICP. The results showed that up-regulation of ERp29 occurred in TCA (taurocholic acid)-treated human trophoblast HTR-8/SVeno cells, and ERp29 inhibition reversed TCA toxicity via attenuating G2/M arrest and cell apoptosis. Mechanical study revealed ERp29 inhibition suppressed phosphorylation and kinase activity of p38, thus subsequently affecting expression and phosphorylation of p53 (ser18) as well as the transcriptional activity of p53. The conduction of this study might confirm the important role of ERp29 in ICP and which would be helpful for the development of target therapeutic method for ICP.

Fine-Tuning of σE Activation Suppresses Multiple Assembly-Defective Mutations in Escherichia coli

The Gram-negative outer membrane (OM) is a selectively permeable asymmetric bilayer that allows vital nutrients to diffuse into the cell but prevents toxins and hydrophobic molecules from entering. Functionally and structurally diverse β-barrel outer membrane proteins (OMPs) build and maintain the permeability barrier, making the assembly of OMPs crucial for cell viability. In this work, we characterize an assembly-defective mutant of the maltoporin LamB, LamBG439D We show that the folding defect of LamBG439D results in an accumulation of unfolded substrate that is toxic to the cell when the periplasmic protease DegP is removed. Selection for suppressors of this toxicity identified the novel mutant degSA323E allele. The mutant DegSA323E protein contains an amino acid substitution at the PDZ/protease domain interface that results in a partially activated conformation of this protein. This activation increases basal levels of downstream σE stress response signaling. Furthermore, the enhanced σE activity of DegSA323E suppresses a number of other assembly-defective conditions without exhibiting the toxicity associated with high levels of σE activity. We propose that the increased basal levels of σE signaling primes the cell to respond to envelope stress before OMP assembly defects threaten cell viability. This finding addresses the importance of envelope stress responses in monitoring the OMP assembly process and underpins the critical balance between envelope defects and stress response activation.IMPORTANCE Gram-negative bacteria, such as Escherichia coli, inhabit a natural environment that is prone to flux. In order to cope with shifting growth conditions and the changing availability of nutrients, cells must be capable of quickly responding to stress. Stress response pathways allow cells to rapidly shift gene expression profiles to ensure survival in this unpredictable environment. Here we describe a mutant that partially activates the σE stress response pathway. The elevated basal level of this stress response allows the cell to quickly respond to overwhelming stress to ensure cell survival.

Pancreatic β-cell failure mediated by mTORC1 hyperactivity and autophagic impairment

Hyperactivation of the mammalian target of rapamycin complex 1 (mTORC1) in β-cells is usually found as a consequence of increased metabolic load. Although it plays an essential role in β-cell compensatory mechanisms, mTORC1 negatively regulates autophagy. Using a mouse model with β-cell-specific deletion of Tsc2 (βTsc2(-/-)) and, consequently, mTORC1 hyperactivation, we focused on the role that chronic mTORC1 hyperactivation might have on β-cell failure. mTORC1 hyperactivation drove an early increase in β-cell mass that later declined, triggering hyperglycemia. Apoptosis and endoplasmic reticulum stress markers were found in islets of older βTsc2(-/-) mice as well as accumulation of p62/SQSTM1 and an impaired autophagic response. Mitochondrial mass was increased in β-cells of βTsc2(-/-) mice, but mitophagy was also impaired under these circumstances. We provide evidence of β-cell autophagy impairment as a link between mTORC1 hyperactivation and mitochondrial dysfunction that probably contributes to β-cell failure.

Autophagy defends pancreatic β cells from human islet amyloid polypeptide-induced toxicity

Type 2 diabetes (T2D) is characterized by a deficiency in β cell mass, increased β cell apoptosis, and extracellular accumulation of islet amyloid derived from islet amyloid polypeptide (IAPP), which β cells coexpress with insulin. IAPP expression is increased in the context of insulin resistance, the major risk factor for developing T2D. Human IAPP is potentially toxic, especially as membrane-permeant oligomers, which have been observed to accumulate within β cells of patients with T2D and rodents expressing human IAPP. Here, we determined that β cell IAPP content is regulated by autophagy through p62-dependent lysosomal degradation. Induction of high levels of human IAPP in mouse β cells resulted in accumulation of this amyloidogenic protein as relatively inert fibrils within cytosolic p62-positive inclusions, which temporarily averts formation of toxic oligomers. Mice hemizygous for transgenic expression of human IAPP did not develop diabetes; however, loss of β cell-specific autophagy in these animals induced diabetes, which was attributable to accumulation of toxic human IAPP oligomers and loss of β cell mass. In human IAPP-expressing mice that lack β cell autophagy, increased oxidative damage and loss of an antioxidant-protective pathway appeared to contribute to increased β cell apoptosis. These findings indicate that autophagy/lysosomal degradation defends β cells against proteotoxicity induced by oligomerization-prone human IAPP.

Metabolic reprogramming of stromal fibroblasts through p62-mTORC1 signaling promotes inflammation and tumorigenesis

The tumor microenvironment plays a critical role in cancer progression, but the precise mechanisms by which stromal cells influence the epithelium are poorly understood. Here we show that p62 levels were reduced in the stroma of several tumors and that its loss in the tumor microenvironment or stromal fibroblasts resulted in increased tumorigenesis of epithelial prostate cancer cells. The mechanism involves the regulation of cellular redox through an mTORC1/c-Myc pathway of stromal glucose and amino acid metabolism, resulting in increased stromal IL-6 production, which is required for tumor promotion in the epithelial compartment. Thus, p62 is an anti-inflammatory tumor suppressor that acts through the modulation of metabolism in the tumor stroma.

SQSTM1/p62/A170 regulates the severity of Legionella pneumophila pneumonia by modulating inflammasome activity

Sequestosome1/A170/p62 (SQSTM1) is a scaffold multifunctional protein involved in several cellular events, such as signal transduction, cell survival, cell death, and inflammation. SQSTM1 expression by macrophages is induced in response to environmental stresses; however, its role in macrophage-mediated host responses to environmental stimuli, such as infectious pathogens, remains unclear. In this study, we investigated the role of SQSTM1 in host responses to Legionella pneumophila, an intra-cellular pathogen that infects macrophages, in both an SQSTM1-deficient (SQSTM1(-/-) ) mouse model and macrophages from these mice. Compared with wild-type (WT) macrophages, the production and secretion of the proinflammatory cytokine IL-1β was significantly enhanced in SQSTM1(-/-) macrophages after infection with L. pneumophila. Inflammasome activity, indicated by the level of IL-18 and caspase-1 activity, was also elevated in SQSTM1(-/-) macrophages after infection with L. pneumophila. SQSTM1 may interact with nucleotide-binding oligomerization domain-like receptor family, caspase recruitment domain-containing 4 and nucleotide-binding oligomerization domain like receptor family, pyrin domain containing 3 proteins to inhibit their self-dimerization. Acute pulmonary inflammation induced by L. pneumophila and silica was enhanced in SQSTM1(-/-) mice with an increase in IL-1β levels in the bronchoalveolar lavage fluids. These findings suggest that SQSTM1 is a negative regulator of acute pulmonary inflammation, possibly by regulating inflammasome activity and subsequent proinflammatory cytokine production.

The small heat shock protein p26 aids development of encysting Artemia embryos, prevents spontaneous diapause termination and protects against stress

Artemia franciscana embryos enter diapause as encysted gastrulae, a physiological state of metabolic dormancy and enhanced stress resistance. The objective of this study was to use RNAi to investigate the function of p26, an abundant, diapause-specific small heat shock protein, in the development and behavior of encysted Artemia embryos (cysts). RNAi methodology was developed where injection of Artemia females with dsRNA specifically eliminated p26 from cysts. p26 mRNA and protein knock down were, respectively, confirmed by RT-PCR and immuno-probing of western blots. ArHsp21 and ArHsp22, diapause-related small heat shock proteins in Artemia cysts sharing a conserved α-crystallin domain with p26, were unaffected by injection of females with dsRNA for p26, demonstrating the specificity of protein knock down. Elimination of p26 delayed cyst release from females demonstrating that this molecular chaperone influences the development of diapause-destined embryos. Although development was slowed the metabolic activities of cysts either containing or lacking p26 were similar. p26 inhibited diapause termination after prolonged incubation of cysts in sea water perhaps by a direct effect on termination or indirectly because p26 is necessary for the preservation of diapause maintenance. Cyst diapause was however, terminated by desiccation and freezing, a procedure leading to high mortality within cyst populations lacking p26 and indicating the protein is required for stress tolerance. Cysts lacking p26 were also less resistant to heat shock. This is the first in vivo study to show that knock down of a small heat shock protein slows the development of diapause-destined embryos, suggesting a role for p26 in the developmental process. The same small heat shock protein prevents spontaneous termination of diapause and provides stress protection to encysted embryos.

Acute inducible ablation of GRP78 reveals its role in hematopoietic stem cell survival, lymphogenesis and regulation of stress signaling

GRP78, a master regulator of the unfolded protein response (UPR) and cell signaling, is required for inner cell mass survival during early embryonic development. However, little is known about its role in adult hematopoietic stem cells (HSCs) and hematopoiesis. Here we generated a conditional knockout mouse model that acutely deletes Grp78 in the adult hematopoietic system. Acute GRP78 ablation resulted in a significant reduction of HSCs, common lymphoid and myeloid progenitors, and lymphoid cell populations in the mutant mice. The GRP78-null induced reduction of the HSC pool could be attributed to increased apoptosis. Chimeric mice with Grp78 deletion only in the hematopoietic cells also showed a loss of HSCs and lymphopenia, suggesting a cell intrinsic effect. Analysis of GRP78 deficient bone marrow (BM) cells showed constitutive activation of all the major UPR signaling pathways, including activation of eIF2α, ATF6, xbp-1 splicing, as well as caspase activation. A multiplex cytokine assay further revealed alteration in select cytokine and chemokine serum levels in the mutant mice. Collectively, these studies demonstrate that GRP78 plays a pleiotropic role in BM cells and contributes to HSC survival and the maintenance of the lymphoid lineage.

Novel mechanism of anti-apoptotic function of 78-kDa glucose-regulated protein (GRP78): endocrine resistance factor in breast cancer, through release of B-cell lymphoma 2 (BCL-2) from BCL-2-interacting killer (BIK)

Activation of the intrinsic apoptotic pathway represents a major mechanism for breast cancer regression resulting from anti-estrogen therapy. The BH3-only protein BIK is inducible by estrogen-starvation and anti-estrogen treatment and plays an important role in anti-estrogen induced apoptosis of breast cancer cells. BIK is predominantly localized to the endoplasmic reticulum where it regulates BAX/BAK-dependent release of Ca(2+) from the endoplasmic reticulum stores and cooperates with other BH3-only proteins such as NOXA to cause rapid release of cytochrome c from mitochondria and activate apoptosis. BIK is also known to inactivate BCL-2 through complex formation. Previously, we demonstrated that apoptosis triggered by BIK in estrogen-starved human breast cancer cells is suppressed by GRP78, a major endoplasmic reticulum chaperone. Here we described the isolation of a novel clonal human breast cancer cell line (MCF-7/BUS-10) resistant to long-term estrogen deprivation. These cells exhibit elevated level of GRP78, which protects them from estrogen starvation-induced apoptosis. Our studies revealed that overexpression of GRP78 suppresses apoptosis induced by BIK and NOXA, either alone or in combination. Surprisingly, the interaction of GRP78 with BIK does not require its BH3 domain, which has been implicated in all previous BIK protein interactions. We further showed GRP78 and BCL-2 form independent complex with BIK and that increased expression of GRP78 decreases BIK binding to BCL-2. Our findings provide the first evidence that GRP78 can decrease BCL-2 sequestration by BIK at the endoplasmic reticulum, thus uncovering a potential new mechanism whereby GRP78 confers endocrine resistance in breast cancer.

[Effect of ClpE depletion on the bacterial protein expression profiles of Streptococcus pneumoniae]

OBJECTIVE

To investigate the effect of ClpE on the protein expression profiles of Streptococcus pneumoniae.

METHODS

clpE-deficient Streptococcus pneumoniae strain was constructed by long flanking homology-polymerase chain reaction (LFH-PCR) and identified by PCR and sequencing. The total bacterial proteins were analyzed by two-dimensional gel electrophoresis and imaging analysis, and the differentially expressed protein spots were excised by dot-gel digestion with trypsin. Peptide mass fingerprinting (PMF) was obtained by analysis of the fragment length by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS). The PMF was analyzed using software to identify the proteins.

RESULTS

The number of matched protein spots of the two gels was 61%. By sequence database searching, 4 out of the 17 differential protein spots were identified, namely hypoxanthine-guanine, pyrrolidone-carboxylate peptidase1, formate-tetrahydrofolate ligase, and bifunctional protein pyrR.

CONCLUSION

clpE gene-deficient Streptococcus pneumoniae expresses fewer kinds of proteins at also lower levels than the wild-type bacteria, suggesting that ClpE allows the bacteria to adapt to different host environments by inducing the expression of special proteins.

Role of Hsp104 in the propagation and inheritance of the [Het-s] prion

The chaperones of the ClpB/HSP100 family play a central role in thermotolerance in bacteria, plants, and fungi by ensuring solubilization of heat-induced protein aggregates. In addition in yeast, Hsp104 was found to be required for prion propagation. Herein, we analyze the role of Podospora anserina Hsp104 (PaHsp104) in the formation and propagation of the [Het-s] prion. We show that DeltaPaHsp104 strains propagate [Het-s], making [Het-s] the first native fungal prion to be propagated in the absence of Hsp104. Nevertheless, we found that [Het-s]-propagon numbers, propagation rate, and spontaneous emergence are reduced in a DeltaPaHsp104 background. In addition, inactivation of PaHsp104 leads to severe meiotic instability of [Het-s] and abolishes its meiotic drive activity. Finally, we show that DeltaPaHSP104 strains are less susceptible than wild type to infection by exogenous recombinant HET-s(218-289) prion amyloids. Like [URE3] and [PIN(+)] in yeast but unlike [PSI(+)], [Het-s] is not cured by constitutive PaHsp104 overexpression. The observed effects of PaHsp104 inactivation are consistent with the described role of Hsp104 in prion aggregate shearing in yeast. However, Hsp104-dependency appears less stringent in P. anserina than in yeast; presumably because in Podospora prion propagation occurs in a syncitium.

Structure, function, property, and role in neurologic diseases and other diseases of the sHsp22

Small heat shock proteins are members of the heat shock proteins family. They share important identical features: 1) they form the conserved structure 'alpha-crystallin domain' with about 80-100 residues in the C-terminal part of the proteins; 2) they have monomeric molecular masses ranging in 12-43 kDa; 3) they associate into large oligomers consisting in many cases of subunits; 4) they increase expression under stress conditions; 5) they exhibit a highly dynamic structure; and 6) they play a chaperone-like role. Hsp22 (also known as HspB8, H11, and E2IG1) retains the structural motif of the 'alpha-crystallin' family of Hsps and is a member of the superfamily of sHsps. Hsp22 displays chaperone activity, autokinase activity, and trigger or block apoptosis activity. It differs from canonical family members existing as a monomer. A decrease in the HspB8 activity may contribute to the development of some neurologic diseases and others.

Type I IFN induction in response to Listeria monocytogenes in human macrophages: evidence for a differential activation of IFN regulatory factor 3 (IRF3)

Listeria monocytogenes is a prototypic bacterium for studying innate and adaptive cellular immunity as well as host defense. Using human monocyte-derived macrophages, we report that an infection with a wild-type strain, but not a listeriolysin O-deficient strain, of the Gram-positive bacterium L. monocytogenes induces expression of IFN-beta and a bioactive type I IFN response. Investigating the activation of signaling pathways in human macrophages after infection revealed that a wild-type strain and a hemolysin-deficient strain of L. monocytogenes activated the NF-kappaB pathway and induced a comparable TNF response. p38 MAPK and activating transcription factor 2 were phosphorylated following infection with either strain, and IFN-beta gene expression induced by wild-type L. monocytogenes was reduced when p38 was inhibited. However, neither IFN regulatory factor (IRF) 3 translocation to the nucleus nor posttranslational modifications and dimerizations were observed after L. monocytogenes infection. In contrast, vesicular stomatitis virus and LPS triggered IRF3 activation and signaling. When IRF3 was knocked down using small interfering RNA, a L. monocytogenes-induced IFN-beta response remained unaffected whereas a vesicular stomatitis virus-triggered response was reduced. Evidence against the possibility that IRF7 acts in place of IRF3 is provided. Thus, we show that wild-type L. monocytogenes induced an IFN-beta response in human macrophages and propose that this response involves p38 MAPK and activating transcription factor 2. Using various stimuli, we show that IRF3 is differentially activated during type I IFN responses in human macrophages.

Demyelination, astrogliosis, and accumulation of ubiquitinated proteins, hallmarks of CNS disease in hsf1-deficient mice

The heat shock transcription factors (Hsfs) are responsible for the heat shock response, an evolutionarily conserved process for clearance of damaged and aggregated proteins. In organisms such as Caenorhabditis elegans, which contain a single Hsf, reduction in the level of Hsf is associated with the appearance of age-related phenotypes and increased accumulation of protein aggregates. Mammalian cells express three hsfs (hsf1, hsf2, hsf4) and their role in CNS homeostasis remains unclear. In this study, we examined the effects of deletion of single or multiple hsf genes in the CNS using mutant mice. Our results show that hsf1-/- mice display progressive myelin loss that accompanies severe astrogliosis and this is exacerbated in the absence of either the hsf2 or hsf4 gene. Magnetic resonance imaging and behavioral studies indicate reduction in the white matter tracts of the corpus callosum, and deficiencies in motor activity, respectively, in aged hsf1-/- mice. Concomitantly, hsf1-/- aged CNS exhibit increased activated microglia and apoptotic cells that are mainly positive for GFAP, an astrocyte-specific marker. Studies based on the expression of short-lived ubiquitinated green fluorescent protein (GFPu) in living hsf1-/- cells indicate that they exhibit reduced ability to degrade ubiquitinated proteins, accumulate short-lived GFPu, and accumulate aggregates of the Huntington's model of GFP containing trinucleotide repeats (Q103-GFP). Likewise, hsf1-/- brain and astrocytes exhibit higher than wild-type levels of ubiquitinated proteins, increased levels of protein oxidation, and increased sensitivity to oxidative stress. These studies indicate a critical role for mammalian hsf genes, but specifically hsf1, in the quality control mechanisms and maintenance of CNS homeostasis during the organism's lifetime.

Differential requirement of unfolded protein response pathway for calreticulin expression in Caenorhabditis elegans

Accumulation of unfolded proteins in the endoplasmic reticulum triggers the unfolded protein response (UPR) pathway, which increases the expression of chaperones to maintain the homeostasis. Calreticulin is a calcium-binding chaperone located in the lumen of endoplasmic reticulum (ER). Here we show that in response to a UPR inducing reagent, tunicamycin, the expression of calreticulin (crt-1) is specifically up-regulated in Caenorhabditis elegans. Tunicamycin (TM) induced expression of the crt-1 requires IRE-1 and XBP-1 but is ATF-6 and PEK-1 independent. Analysis of the crt-1 promoter reveals a putative XBP-1 binding site at the -284 to -278 bp region, which was shown to be necessary for TM-mediated induction. Genetic analysis of crt-1 mutants and mutants of UPR pathway genes show various degrees of developmental arrest upon TM treatment. Our results suggest that the TM-induced UPR pathway culminates in the up-regulation of crt-1, which protects the worm from deleterious accumulation of unfolded proteins in the ER. Knockdown of the crt-1, pdi-2, or pdi-3 increased the crt-1 expression, whereas knockdown of the hsp-3 or hsp-4 did not have any effect on crt-1 expression, indicating the existence of complex compensatory networks to cope up with ER stress.

Filamentous morphology in GroE-depleted Escherichia coli induced by impaired folding of FtsE

The chaperonin GroE (GroEL and the cochaperonin GroES) is the only chaperone system that is essential for the viability of Escherichia coli. It is known that GroE-depleted cells exhibit a filamentous morphology, suggesting that GroE is required for the folding of proteins involved in cell division. Although previous studies, including proteome-wide analyses of GroE substrates, have suggested several targets of GroE in cell division, there is no direct in vivo evidence to identify which substrates exhibit obligate dependence on GroE for folding. Among the candidate substrates, we found that prior excess production of FtsE, a protein engaged in cell division, completely suppressed the filamentation of GroE-depleted E. coli. The GroE depletion led to a drastic decrease in FtsE, and the cells exhibited a known phenotype associated with impaired FtsE function. In the GroE-depleted filamentous cells, the localizations of FtsA and ZipA, both of which assemble with the FtsZ septal ring before FtsE, were normal, whereas FtsX, the interaction partner of FtsE, and FtsQ, which is recruited after FtsE, did not localize to the ring, suggesting that the decrease in FtsE is a cause of the filamentous morphology. Finally, a reconstituted cell-free translation system revealed that the folding of newly translated FtsE was stringently dependent on GroEL/GroES. Based on these findings, we concluded that FtsE is a target substrate of the GroE system in E. coli cell division.

Hsp27 knockdown using nucleotide-based therapies inhibit tumor growth and enhance chemotherapy in human bladder cancer cells

Heat shock protein 27 (Hsp27) is a cytoprotective chaperone that is phosphoactivated during cell stress that prevents aggregation and/or regulate activity and degradation of certain client proteins. Recent evidence suggests that Hsp27 may be involved in tumor progression and the development of treatment resistance in various tumors, including bladder cancer. The purpose of this study was to examine, both in vitro and in vivo, the effects of overexpression of Hsp27 and, correspondingly, the down-regulation of Hsp27 using small interfering (si) RNA and OGX-427, a second-generation antisense oligonucleotide targeting Hsp27. Hsp27 overexpression increased UMUC-3 cell growth and resistance to paclitaxel. Both OGX-427 and Hsp27 siRNA decreased Hsp27 protein and mRNA levels by >90% in a dose- and sequence-specific manner in human bladder cancer UMUC-3 cells. OGX-427 or Hsp27 siRNA treatment induced apoptosis and enhanced sensitivity to paclitaxel in UMUC-3 cells. In vivo, OGX-427 significantly inhibited tumor growth in mice, enhanced sensitivity to paclitaxel, and induced significantly higher levels of apoptosis compared with xenografts treated with control oligonucleotides. Collectively, these findings suggest that Hsp27 knockdown with OGX-427 and combined therapy with paclitaxel could be a novel strategy to inhibit the progression of bladder cancer.

Spontaneous recovery of pathogenicity by Leishmania major hsp100-/- alters the immune response in mice

By using repeated mouse infection cycles, we obtained an escape variant with restored infectivity and pathogenicity that originated from a single, noninfectious hsp100-/- gene (formerly known as DeltaclpB) replacement clone of Leishmania major, the causative agent of cutaneous leishmaniasis. This isolate elicited increased infiltration of immune cells to the site of infection and altered the polarization of the immune response in BALB/c mice from a predominantly TH2 type to a TH1 type. A clonal analysis resulted in isolation of two clones with antagonistic properties. While one clone exhibited restored infectivity in isolated macrophages but caused no persistent infection in the mouse model, the second clone was unable to infect macrophages in vitro but could establish a lasting infection and form progressive lesions in BALB/c mice. Our results add to the evidence that the TH1-TH2 dichotomy of the early immune response against L. major not only depends on the genetic predisposition of the host but also depends on intrinsic properties of the parasite.

Listeriolysin O-deficient Listeria monocytogenes as a vaccine delivery vehicle: antigen-specific CD8 T cell priming and protective immunity

Strains of Listeria monocytogenes (LM) that are deficient in the virulence factor listeriolysin O (LLO) are highly attenuated and are thought not to elicit protective immunity. This failure has been attributed to the inability of the bacterium to enter the host cell cytosol and access MHC class I Ag processing machinery. We reexamined this issue using recombinant strains of LM that are deficient in LLO but express an additional CD8 T cell epitope derived from lymphocytic choriomeningitis virus. After infection with LLO-deficient strains, we find sizable priming of epitope-specific CD8 T cells and the development of a functional memory cell population. Mice primed with the LLO-deficient LM strain are equally resistant against high-dose challenge with virulent LM as mice primed with wild-type virulent bacteria and also resist heterologous challenge with lymphocytic choriomeningitis virus. Interestingly, priming with a low dose of LLO-deficient LM, which occurred in environment of reduced inflammation (IFN-gamma), allowed rapid amplification of Ag-specific CD8 T cells by booster immunization, despite an undetectable primary response. We conclude that the generation of protective immunity by LLO-deficient strains of LM does in fact occur and that this highly attenuated LM strain may be a useful platform for vaccine delivery.

Cytosolic entry controls CD8+-T-cell potency during bacterial infection

Interaction with host immunoreceptors during microbial infection directly impacts the magnitude of the ensuing innate immune response. How these signals affect the quality of the adaptive T-cell response remains poorly understood. Utilizing an engineered strain of the intracellular pathogen Listeria monocytogenes that infects cells but fails to escape from the phagosome, we demonstrate the induction of long-lived memory T cells that are capable of secondary expansion and effector function but are incapable of providing protective immunity. We demonstrate that microbial invasion of the cytosol is required for dendritic cell activation and integration of CD40 signaling, ultimately determining the ability of the elicited CD8+-T-cell pool to protect against lethal wild-type L. monocytogenes challenge. These results reveal a crucial role for phagosomal escape, not for delivery of antigen to the class I major histocompatibility complex pathway but for establishing the appropriate cellular context during CD8+-T-cell priming.

L2DTL/CDT2 interacts with the CUL4/DDB1 complex and PCNA and regulates CDT1 proteolysis in response to DNA damage

The CUL4 (cullin 4) proteins are the core components of a new class of ubiquitin E3 ligases that regulate cell cycle, DNA replication and DNA damage response. To determine the composition of CUL4 ubiquitin E3 ligase complex, we used anti-CUL4 antibody affinity chromatography to isolate the proteins that associated with human CUL4 complexes and identified them by mass-spectrometry. A novel and conserved WD40 domain-containing protein, the human homologue of Drosophila lethal(2) denticleless protein (L2DTL) or fission yeast CDT2, was found to associate with CUL4 and DDB1. L2DTL also interacts with replication licensing protein CDT1 in vivo. Loss of L2DTL in Drosophila S2 and human cells suppressed proteolysis of CDT1 in response to DNA damage. We further isolated the human L2DTL complexes by anti-L2DTL immuno-affinity chromatography from HeLa cells and found it associates with DDB1, components of the COP9-signalosome complex (CSN) and PCNA. We found that PCNA interacts with CDT1 and loss of PCNA suppressed CDT1 proteolysis after DNA damage. Our data also revealed that in vivo, inactivation of L2DTL causes the dissociation of DDB1 from the CUL4 complex. Our studies suggest that L2DTL and PCNA interact with CUL4/DDB1 complexes and are involved in CDT1 degradation after DNA damage.

L2DTL/CDT2 and PCNA Interact with p53 and Regulate p53 Polyubiquitination and Protein Stability through MDM2 and CUL4A/DDB1 Complexes

The CUL4-ROC1 E3 ligase complex regulates genome stability, replication and cell cycle progression. A novel WD40 domain-containing protein, L2DTL/CDT2 and PCNA were identified as proteins associated with CUL4/DDB1 complexes. Inactivation of CUL4A, L2DTL, PCNA, DDB1 or ROC1 induced p53 stabilization and growth arrest. L2DTL, PCNA and DDB1/CUL4A complexes were found to physically interact with p53 tumor suppressor and its regulator MDM2/HDM2. The isolated CUL4A complexes display potent and robust polyubiquitination activity towards p53 and this activity is dependent on L2DTL, PCNA, DDB1, ROC1 and MDM2/HDM2. We also found that the interaction between p53 and CUL4 complex is regulated by DNA damage. Our data further showed that MDM2/HDM2 is rapidly proteolyzed in response to UV irradiation and this process is regulated by CUL4/DDB1 and PCNA. Our studies demonstrate that PCNA, L2DTL and the DDB1-CUL4A complex play critical and differential roles in regulating the protein stability of p53 and MDM2/HDM2 in unstressed and stressed cells.

RETRACTED: Si RNA inhibition of GRP58 associated with decrease in mitomycin C-induced DNA cross-linking and cytotoxicity

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the Office of Integrity of the University of Maryland due to data entered in Fig 3 of the publication that were not supported by raw data, in addition to the fact that the statistical evaluations were adultered.

CRYAB and HSPB2 deficiency increases myocyte mitochondrial permeability transition and mitochondrial calcium uptake

Double knockout (DKO) of the small heat shock proteins CRYAB and HSPB2 increases necrosis and apoptosis induced by ischemia/reperfusion (I/R) in vitro, but the mechanisms involved are unknown. We examined [Ca2+]i during metabolic inhibition (MI) changes in [Ca2+]m induced by exposure to elevated [Ca2+]i, and whether mitochondria in isolated DKO ventricular myocytes (VM) are more susceptible than wild type (WT) to induction of the mitochondrial permeability transition (MPT). The rise in [Ca2+]i in DKO myocytes during metabolic inhibition (MI) was less than in WT, and ouabain caused a greater increase in [Ca2+]m in DKO than in WT. These findings suggested that Ca2+ uptake was increased in mitochondria in DKO myocytes. Measurements of Rhod 2 fluorescence during exposure of permeabilized VM to 1000 nM [Ca2+] for 5 min confirmed that DKO myocytes have enhanced mitochondrial Ca2+ uptake, and this difference between DKO and WT myocyte mitochondria was eliminated by inhibition of NO synthesis. MPT was induced more readily by ouabain, PAO, or TMRM in DKO myocytes than in WT. Thus, Ca2+ uptake by mitochondria is increased in DKO VM by a NO-dependent mechanism. This can predispose to the development of MPT, and increased VM injury during I/R. These findings indicate an important role of CRYAB and/or HSPB2 in mitochondrial function.

Role of heat-shock factor 2 in cerebral cortex formation and as a regulator of p35 expression

Heat-shock factors (HSFs) are associated with multiple developmental processes, but their mechanisms of action in these processes remain largely enigmatic. Hsf2-null mice display gametogenesis defects and brain abnormalities characterized by enlarged ventricles. Here, we show that Hsf2-/- cerebral cortex displays mispositioning of neurons of superficial layers. HSF2 deficiency resulted in a reduced number of radial glia fibers, the architectural guides for migrating neurons, and of Cajal-Retzius cells, which secrete the positioning signal Reelin. Therefore, we focused on the radial migration signaling pathways. The levels of Reelin and Dab1 tyrosine phosphorylation were reduced, suggesting that the Reelin cascade is affected in Hsf2-/- cortices. The expression of p35, an activator of cyclin-dependent kinase 5 (Cdk5), essential for radial migration, was dependent on the amount of HSF2 in gain- and loss-of-function systems. p39, another Cdk5 activator, displayed reduced mRNA levels in Hsf2-/- cortices, which, together with the lowered p35 levels, decreased Cdk5 activity. We demonstrate in vivo binding of HSF2 to the p35 promoter and thereby identify p35 as the first target gene for HSF2 in cortical development. In conclusion, HSF2 affects cellular populations that assist in radial migration and directly regulates the expression of p35, a crucial actor of radial neuronal migration.

Analysis of Escherichia coli global gene expression profiles in response to overexpression and deletion of CspC and CspE

The Escherichia coli cold shock protein CspA family consists of nine proteins (CspA to CspI), of which two, CspE and CspC, are constitutively produced at 37 degrees C and are involved in regulation of expression of genes encoding stress response proteins but can also perform an essential function during cold acclimation. In this study, we analyzed global transcript profiles of cells lacking cspE and cspC as well as cells individually overexpressing these proteins or a CspE mutant that is unable to melt nucleic acids and is defective in cold acclimation. The analysis reveals sets of genes whose expression (i) is regulated by CspC and CspE at physiological temperature or cold shock conditions and (ii) depends on the nucleic acid melting function of CspE. Bioinformatic analysis of the latter group reveals that many of those genes contain promoter-proximal sequences that can block transcript elongation and may be targeted by the nucleic acid melting function of CspE.

Cutting edge: a novel nonoxidative phagosomal mechanism exerted by cathepsin-D controls Listeria monocytogenes intracellular growth

Deciphering how Listeria monocytogenes exploits the host cell machinery to invade mammalian cells is a key issue in understanding the pathogenesis of this food-borne pathogen, which can cause diseases ranging from gastroenteritis to meningitis and abortion. In this study, we show that the lysosomal aspartyl-protease cathepsin-D (Ctsd) is of considerable importance for nonoxidative listericidal defense mechanisms. We observed enhanced susceptibility to L. monocytogenes infection of fibroblasts and bone-marrow macrophages and increased intraphagosomal viability of bacteria in fibroblasts isolated from Ctsd-deficient mice compared with wild type. These findings are further supported by prolonged survival of L. monocytogenes in Ctsd-deficient mice after infection. Transient transfection of Ctsd in wild-type cells was sufficient to revert these wild-type phagosomes back to microbicidal compartments. Based on infection experiments with mutant bacteria, in vitro degradation, and immunoprecipitation experiments, we suggest that a major target of cathepsin D is the main virulence factor listeriolysin O.

[Expression deficiency of JWA enhanced DNA damage and delayed DNA repair in HeLa cells induced by benzo (a) pyrene exposure]

OBJECTIVE

To investigate the role of JWA gene in benzo (a) pyrene [B (a) P] induced DNA damage and repair effects in HeLa cells.

METHODS

The antisense JWA express vector (pEGFP-C1-asJWA) was constructed and stably transfected into HeLa cells. JWA deficient HeLa cells (asJWA-HeLa) was then screened and established. The general characteristics of asJWA-HeLa cells were investigated. DNA damage and repair cell culture model was conducted by treating the cells with 50 micromol/L B (a) P plus S9 for 3 hours and then the cells were maintained further 0, 1, 3, and 24 hours for DNA repairing. The damaged DNA was detected by single cell gel electrophoresis assay (comet assay).

RESULTS

JWA deficient HeLa cells (with a 31% of JWA protein expression as compared with the control) were obtained successfully. Compared with the empty vector transfected cells (C1-HeLa) and the untransfected HeLa cells, asJWA-HeLa cells were more sensitive to B (a) P exposure and with a delayed DNA repair process.

CONCLUSION

The JWA determined might function as a potential effective environmental responsive gene and actively participate the process of B (a) P exposure associated with intracellular signal pathways of DNA damage and repair.

Consequences of ERp57 Deletion on Oxidative Folding of Obligate and Facultative Clients of the Calnexin Cycle

Members of the protein-disulfide isomerase superfamily catalyze the formation of intra- and intermolecular disulfide bonds, a rate-limiting step of protein folding in the endoplasmic reticulum (ER). Here we compared maturation of one obligate and two facultative calnexin substrates in cells with and without ERp57, the calnexin-associated, glycoprotein-specific oxidoreductase. ERp57 deletion did not prevent the formation of disulfide bonds during co-translational translocation of nascent glycopolypeptides in the ER. It affected, however, the post-translational phases of oxidative influenza virus hemagglutinin (HA) folding, resulting in significant loss of folding efficiency for this obligate calnexin substrate. Without ERp57, HA also showed reduced capacity to recover from an artificially induced aberrant conformation, thus revealing a crucial role of ERp57 during post-translational reshuffling to the native set of HA disulfides. ERp57 deletion did not affect maturation of the model facultative calnexin substrates E1 and p62 (and of most cellular proteins, as shown by lack of induction of ER stress). ERp72 was identified as one of the ER-resident oxidoreductases associating with the orphan ERp57 substrates to maintain their folding competence.

High-level resistance to oxidative stress in Lactococcus lactis conferred by Bacillus subtilis catalase KatE

Lactococcus lactis, a lactic acid bacterium widely used for food fermentations, is often exposed to damaging stress conditions. In particular, oxidative stress leads to DNA, protein and membrane damages that can be lethal. As L. lactis has no catalase, the impact of production of the Bacillus subtilis haem catalase KatE on its oxidative stress resistance was tested. This cytoplasmic catalase was engineered for extracellular expression in L. lactis with an optimization strategy based on fusion to the nisin-inducible promoter and a lactococcal signal peptide (SP(Usp45)). The production of KatE by L. lactis conferred an 800-fold increase in survival after 1 h exposure to 4 mM hydrogen peroxide, and a 160-fold greater survival in long-term (3 days) survival of aerated cultures in a cydA mutant, which is unable to respire. The presence of KatE protected DNA from oxidative damage and limited its degradation after long-term aeration in a cydA/recA mutant, defective in DNA repair. L. lactis is thus able to produce active catalase that can provide efficient antioxidant activity.

Impaired assembly of the major histocompatibility complex class I peptide-loading complex in mice deficient in the oxidoreductase ERp57

The thiol-oxidoreductase ERp57 is an integral component of the peptide-loading complex of the major histocompatibility complex (MHC) class I pathway, but its function is unknown. To investigate its function in antigen presentation, we generated ERp57-deficient mice. Death in utero caused by ubiquitous ERp57 deletion was prevented by specific deletion in the B cell compartment. We demonstrate that ERp57 was central for recruitment of MHC class I molecules into the loading complex. In ERp57-deficient cells, we found short-lived interaction of MHC class I molecules with the loading complex. Thus, in the steady state, very few MHC class I molecules were present in the loading complex. Surface H-2K(b)-peptide expression and stability were reduced, and presentation of a model antigen was decreased. Our results indicate that ERp57 does not influence the redox state of MHC class I molecules but is an essential structural component required for stable assembly of the peptide-loading complex.

Additive inhibition of complement deposition by pneumolysin and PspA facilitates Streptococcus pneumoniae septicemia

Streptococcus pneumoniae is a common cause of septicemia in the immunocompetent host. To establish infection, S. pneumoniae has to overcome host innate immune responses, one component of which is the complement system. Using isogenic bacterial mutant strains and complement-deficient immune naive mice, we show that the S. pneumoniae virulence factor pneumolysin prevents complement deposition on S. pneumoniae, mainly through effects on the classical pathway. In addition, using a double pspA-/ply- mutant strain we demonstrate that pneumolysin and the S. pneumoniae surface protein PspA act in concert to affect both classical and alternative complement pathway activity. As a result, the virulence of the pspA-/ply- strain in models of both systemic and pulmonary infection is greatly attenuated in wild-type mice but not complement deficient mice. The sensitivity of the pspA-/ply- strain to complement was exploited to demonstrate that although early innate immunity to S. pneumoniae during pulmonary infection is partially complement-dependent, the main effect of complement is to prevent spread of S. pneumoniae from the lungs to the blood. These data suggest that inhibition of complement deposition on S. pneumoniae by pneumolysin and PspA is essential for S. pneumoniae to successfully cause septicemia. Targeting mechanisms of complement inhibition could be an effective therapeutic strategy for patients with septicemia due to S. pneumoniae or other bacterial pathogens.

Ischemia-induced increase of stiffness of αB-crystallin/HSPB2-deficient myocardium

The two small heat shock proteins (sHSPs), alphaB-crystallin and HSPB2, have been shown to translocate within a few minutes of cardiac ischemia from the cytosol to myofibrils; and it has been suggested that their chaperone-like properties might protect myofibrillar proteins from unfolding or aggregation during stress conditions. Further evidence of an important role for HSPs in muscle function is provided by the fact that mutations of the alphaB-crystallin gene cause myopathy and cardiomyopathy. In the present study, we subjected isolated papillary muscles of alphaB-crystallin/HSPB2-deficient mice to simulated ischemia and reperfusion. During ischemia in alphaB-crystallin/HSPB2-deficient muscles, the development of contracture started earlier and reached a higher value compared to the wildtype mice. The recovery of contracture of alphaB-crystallin/HSPB2-deficient muscles was also attenuated during the simulated reperfusion period. However, twitch force was not significantly altered at any time of the experiment. This suggests that during ischemic insults, alphaB-crystallin/HSPB2 may not be important for the contraction process itself, but rather serve to maintain muscular elasticity.

Involvement of peroxiredoxin I in protecting cells from radiation-induced death

Peroxiredoxin I (Prx-I), a key member of the peroxiredoxin family, reduces peroxides and equivalents through the thioredoxin system. Our previous work has shown that expression of Prx-I in mammalian cells increases following ionizing radiation (IR), indicating that Prx-I actively responds to IR-induced reactive oxygen species (ROS) and suggesting that Prx-I plays an important role in protecting cells from IR-induced death. To test this hypothesis, we suppressed the expression of Prx-I in SW480 cells by RNA interference. Our results show that IR induces the expression of Prx-I in SW480 cells in a dose- and time-dependent manner. The recombinant siRNA vector targeting Prx-I dramatically reduced the expression of Prx-I in SW480 cells. When Prx-I was knocked down in SW480 cells, the cells exhibited a decreased growth rate, a reduced antioxidant capability following IR and became more sensitive to IR-induced apoptosis. Together, our results demonstrate that Prx-I plays an important role in protecting cells from IR-induced cell death, which might be through scavenging IR-induced ROS in the cells.

Tid1 Is Required for T Cell Transition from Double-Negative 3 to Double-Positive Stages

Tid1, a DnaJ cochaperone protein, is the mammalian homologue of the Drosophila tumor suppressor Tid56 whose antitumor function is most likely mediated through its capacity to regulate cell differentiation in imaginal discs. We suspected that the mammalian counterpart, tid1, may also be involved in regulating cell differentiation. To investigate this, we exploited the system of T cell development to examine whether tid1 plays a role in this well-defined process. Mice with tid1 specifically deleted in T cells developed thymic atrophy, with dramatic reduction of double-positive and single-positive thymocytes in the tid1(-/-) thymus. Although the subpopulations of tid1(-/-) double-negative (DN) 1-3 thymocytes were normal, the subpopulation of DN4 thymocytes was measurably smaller because of reduced proliferation and significant cell death. Immature tid1(-/-) thymocytes show normal VDJ beta-chain rearrangement and pre-TCR and CD3 expression in both DN3 and DN4 thymocytes, but in DN4 thymocytes, there was significantly reduced expression of the antiapoptotic bcl-2 gene. Restoring the expression level of Bcl-2 protein in tid1(-/-) thymus by introduction of a transgenic human bcl-2 gene resulted in reversal of the developmental defects in tid1(-/-) thymus. Together, these results demonstrate that tid1 is critical in early thymocyte development, especially during transition from the DN3 to double-positive stages, possibly through its regulation of bcl-2 expression, which provides survival signals.

Odf2-deficient mother centrioles lack distal/subdistal appendages and the ability to generate primary cilia

Outer dense fibre 2 (Odf2; also known as cenexin) was initially identified as a main component of the sperm tail cytoskeleton, but was later shown to be a general scaffold protein that is specifically localized at the distal/subdistal appendages of mother centrioles. Here we show that Odf2 expression is suppressed in mouse F9 cells when both alleles of Odf2 genes are deleted. Unexpectedly, the cell cycle of Odf2(-/-) cells does not seem to be affected. Immunofluorescence and ultrathin-section electron microscopy reveals that in Odf2(-/-) cells, distal/subdistal appendages disappear from mother centrioles, making it difficult to distinguish mother from daughter centrioles. In Odf2(-/-) cells, however, the formation of primary cilia is completely suppressed, although approximately 25% of wild-type F9 cells are ciliated under the steady-state cell cycle. The loss of primary cilia in Odf2(-/-) F9 cells can be rescued by exogenous Odf2 expression. These findings indicate that Odf2 is indispensable for the formation of distal/subdistal appendages and the generation of primary cilia, but not for other cell-cycle-related centriolar functions.

A type I DnaJ homolog, DjA1, regulates androgen receptor signaling and spermatogenesis

Two type I DnaJ homologs DjA1 (DNAJA1; dj2, HSDJ/hdj-2, rdj1) and DjA2 (DNAJA2; dj3, rdj2) work similarly as a cochaperone of Hsp70s in protein folding and mitochondrial protein import in vitro. To study the in vivo role of DjA1, we generated DjA1-mutant mice. Surprisingly, loss of DjA1 in mice led to severe defects in spermatogenesis that involve aberrant androgen signaling. Transplantation experiments with green fluorescent protein-labeled spermatogonia into DjA1(-/-) mice revealed a primary defect of Sertoli cells in maintaining spermiogenesis at steps 8 and 9. In Sertoli cells of DjA1(-/-) mice, the androgen receptor markedly accumulated with enhanced transcription of several androgen-responsive genes, including Pem and testin. Disruption of Sertoli-germ cell adherens junctions was also evident in DjA1(-/-) mice. Experiments with DjA1(-/-) fibroblasts and primary Sertoli cells indicated aberrant androgen receptor signaling. These results revealed a critical role of DjA1 in spermiogenesis and suggest that DjA1 and DjA2 are not functionally equivalent in vivo.

Cutting edge: cross-presentation of cell-associated antigens to MHC class I molecule is regulated by a major transcription factor for heat shock proteins

The ability for the professional APC to cross-present Ag to MHC class I from parenchymal cells is essential for priming as well as tolerance of CD8+ T cells against intracellular Ags. Since cross-presentations of non-cell-associated free Ags are inefficient, the roles of molecular chaperones or heat shock proteins (HSPs) in chaperoning Ags to APCs have been postulated. We herein genetically addressed this hypothesis using mice that were defective of heat shock factor 1 (Hsf1), a major transcription factor for HSPs. Hsf1(-/-) mice have a decreased expression of several HSPs including HSP90 and HSP70. Using multiple Ag systems, we demonstrated that cross-priming of Ag-specific CD8+ T cells was inefficient when Ag expression was restricted to Hsf1(-/-) non-APCs. Our study provides the first genetic evidence for the roles of Hsf1 in regulating cross-presentation of MHC class I-associated Ags.

Decreased lifespan in the absence of expression of the mitochondrial small heat shock protein Hsp22 in Drosophila

Aging is a well regulated biological process involving oxidative stress and macromolecular damages. Three main pathways have been shown to influence lifespan, the insulin/insulin-like growth factor-1 pathway, the silent regulator pathway, and the target of rapamycin pathway. Among many proteins influencing lifespan, two transcription factors, FOXO and the heat shock factor, have been shown to be involved in the aging process and in small heat shock proteins (sHsps) expression following stress and during lifespan. We have recently shown that overexpressing the mitochondrial Hsp22 increases Drosophila melanogaster lifespan by 32% and resistance to oxidative stress. Here we show that flies that are not expressing this mitochondrial small Hsp22 have a 40% decrease in lifespan. These flies die faster than their matched control and display a decrease of 30% in locomotor activity compared with controls. The absence of Hsp22 also sensitizes flies to mild stress. These data support a key role of sHsps in aging and underline the importance of mitochondrial sHsps in this process.

Identification by a differential proteomic approach of heat shock protein 27 as a potential marker of atherosclerosis

BACKGROUND

We hypothesized that normal and pathological vessel walls display a differential pattern of secreted proteins. We have recently set up the conditions for comparing secretomes from carotid atherosclerotic plaques and control arteries using a proteomic approach to assess whether differentially secreted proteins could represent markers for atherosclerosis.

METHODS AND RESULTS

Normal endartery segments and different regions of endarterectomy pieces (noncomplicated/complicated plaques) were incubated in protein-free medium, and the released proteins were analyzed by 2D electrophoresis (2-DE). Among the differently secreted proteins, we have identified heat shock protein-27 (HSP27). Surprisingly, compared with control arteries, HSP27 release was drastically decreased in atherosclerotic plaques and barely detectable in complicated plaque supernatants. HSP27 was expressed primarily by intact vascular cells of normal arteries and carotid plaques (immunohistochemistry). Plasma detection of soluble HSP27 showed that circulating HSP27 levels are significantly decreased in the blood of patients with carotid stenosis relative to healthy subjects (0.19 [0.1 to 1.95] versus 83 [71.8 to 87.8]) ng/mL, P<0.0001).

CONCLUSIONS

HSP27 secretion is decreased in complicated atherosclerotic plaques, and sHSP27 plasma levels are decreased in atherosclerotic patients compared with healthy subjects. Plasma sHSP27 levels could be a potential index of atherosclerosis, although further validation is needed in large patient cohorts.

Phenotypic characterization of mouse embryonic fibroblasts lacking heat shock factor 2

In murine cells, the heat shock response is regulated by a transcription factor, HSF1, which triggers the transcription of heat shock genes. HSF2 has been shown to be involved in meiosis and mouse brain development. We characterized the effects of the absence of HSF2 in mouse embryonic fibroblasts (MEFs). The temperature threshold of the heat shock response appeared lowered in Hsf2(-/-) MEFS as monitored by the synthesis of heat shock protein HSP70. In contrast to unstressed wild type MEFS, HSP70 and HSF1 are localized in the nucleus of unstressed Hsf2(-/-) MEFS, a characteristic of stressed cells. HSF1 is not activated for DNA-binding at unstressed temperature in Hsf2(-/-) MEFS. Therefore, the absence of HSF2 induces some but not all of the characteristics of the stress response. In addition, Hsf2(-/-) MEFS exhibited proliferation defects, altered morphology, remodeling of the fibronectin network.

Requirement of the Listeria monocytogenes broad-range phospholipase PC-PLC during infection of human epithelial cells

In this study, we investigated the requirement of the Listeria monocytogenes broad-range phospholipase C (PC-PLC) during infection of human epithelial cells. L. monocytogenes is a facultative intracellular bacterial pathogen of humans and a variety of animal species. After entering a host cell, L. monocytogenes is initially surrounded by a membrane-bound vacuole. Bacteria promote their escape from this vacuole, grow within the host cell cytosol, and spread from cell to cell via actin-based motility. Most infection studies with L. monocytogenes have been performed with mouse cells or an in vivo mouse model of infection. In all mouse-derived cells tested, the pore-forming cytolysin listeriolysin O (LLO) is absolutely required for lysis of primary vacuoles formed during host cell entry. However, L. monocytogenes can escape from primary vacuoles in the absence of LLO during infection of human epithelial cell lines Henle 407, HEp-2, and HeLa. Previous studies have shown that the broad-range phospholipase C, PC-PLC, promotes lysis of Henle 407 cell primary vacuoles in the absence of LLO. Here, we have shown that PC-PLC is also required for lysis of HEp-2 and HeLa cell primary vacuoles in the absence of LLO expression. Furthermore, our results indicated that the amount of PC-PLC activity is critical for the efficiency of vacuolar lysis. In an LLO-negative derivative of L. monocytogenes strain 10403S, expression of PC-PLC has to increase before or upon entry into human epithelial cells, compared to expression in broth culture, to allow bacterial escape from primary vacuoles. Using a system for inducible PC-PLC expression in L. monocytogenes, we provide evidence that phospholipase activity can be increased by elevated expression of PC-PLC or Mpl, the enzyme required for proteolytic activation of PC-PLC. Lastly, by using the inducible PC-PLC expression system, we demonstrate that, in the absence of LLO, PC-PLC activity is not only required for lysis of primary vacuoles in human epithelial cells but is also necessary for efficient cell-to-cell spread. We speculate that the additional requirement for PC-PLC activity is for lysis of secondary double-membrane vacuoles formed during cell-to-cell spread.

Tailoring host immune responses to Listeria by manipulation of virulence genes -- the interface between innate and acquired immunity

Although attenuated strains of microbial pathogens have triggered vaccine development from its origin, the role of virulence factors in determining host immunity has remained largely unexplored. Using the murine listeriosis model, we investigated whether the induction and expansion of protective and inflammatory T cell responses may be modified by selective manipulation of virulence genes. We intentionally deleted specific genes of Listeria monocytogenes, including those encoding the positive regulatory factor (prfA), hemolysin (hly), the actin nucleator (actA), and phospholipase B (plcB). The resulting strains showed decisive differences in their immunogenic properties. In particular, we identified a double-deletion mutant that retained Listeria's profound ability to induce protective CD8(+) T cells, but that is strongly attenuated and exhibits a significantly reduced ability to induce CD4(+) T cell-mediated inflammation. We conclude that this mutant, L. monocytogenes DeltaactADeltaplcB, is at present the most promising mutant for a bacterial vaccine vector and is able to safely induce potent CD8(+) T cell-mediated immunity.

[Heat shock during the development of brain structures of Drosophila: the memory development in the l(1)ts403 mutant of Drosophila melanogaster]

The structures and functions of many genes are homologous in Drosophila and humans. Therefore, studying pathological processes in Drosophila, in particular neurogenerative processes accompanied by progressive memory loss, helps to understand the ethiology of corresponding human disorders and to develop therapeutic strategies. It is believed that the development of neurogenerative diseases might result from alterations in the functioning of the heat shock/chaperone machinery. In view of this, we used Drosophila mutant l(1)ts403 with defective synthesis of heat shock proteins for studying learning and memory in a test of conditioned courtship suppression following a heat shock given at different developmental stages. High learning indices were registered immediately and 30 min after training both in the intact controls and in flies subjected to different developmental heat shocks. This indicated normal learning and memory acquisition in the mutant. At the same time, memory retention (3 h after training) suffered to different extent depending on the developmental stage. The remote effects of heat shock given during the formation of the mushroom bodies indicated the important role of this brain structure in the memory formation. The observed memory defects may result from alterations both in mRNA transport and in the functions of molecular chaperones in the l(1)ts403 mutant.

[Therapeutic strategy for fibrotic diseases by regulating the expression of collagen-specific molecular chaperone HSP47]

Through disruption of the hsp47 gene in mice, we found that HSP47, a collagen-specific molecular chaperone residing in the endoplasmic reticulum, is essential for mouse development. Improper triple helix formation was observed in hsp47-null embryos, and no collagen fibrils in the mesenchyme or basement membranes between the mesenchyme and epithelial cell layers were seen in those mice, which resulted in embryonic lethality. Interestingly, constitutive expression of HSP47 is always correlated with that of collagens in various cells or tissues. HSP47 is markedly up-regulated during the progression of fibrosis in the liver, kidney, lung, and so on. A preliminary experiment showed that down-regulation of HSP47 caused the reduction in the progression of fibrosis by down-regulating the accumulation of collagens in the tissues, which suggests a novel strategy for the therapy of fibrotic diseases including liver cirrhosis.

Mouse heat shock transcription factor 1 deficiency alters cardiac redox homeostasis and increases mitochondrial oxidative damage

In this study, using heat shock factor 1 (Hsf1) knockout mice as a model, we tested the hypothesis that HSF1-dependent regulation of heat shock proteins (Hsps) is required to maintain redox state and attenuate oxidative damage in the normal heart. Here we report that, in mice, HSF1 deficiency reduces cardiac expression of Hsp25, alphaB-crystallin and Hsp70, but not Hsp60 and Hsp90. Consistent with the downregulation of Hsp25, for example, a significantly lower glutathione (GSH)/glutathione disulfate (GSSG) ratio was associated with the decreased activity, but not protein content, of glucose 6-phosphate dehydrogenase. Con sequently, superoxide was generated at a higher rate, and several mitochondrial proteins, including adenine nucleotide translocase 1 (ANT1), were more oxidized by HSF1 deficiency in vivo. Oxidative damage to ANT1 protein, a structural component of the mitochondrial permeability transition pore (MPTP), decreases its catalytic activity and increases MPTP opening, respectively. Taken together, our results indicate for the first time that constitutive expression of HSP chaperones requires HSF1 activity, and that such HSF1-dependent requirements are directly and functionally linked to maintain redox homeostasis and antioxidative defenses at normal (37 degrees C) temperature.

IS186 insertion at a hot spot in the lon promoter as a basis for lon protease deficiency of Escherichia coli B: identification of a consensus target sequence for IS186 transposition

The radiation sensitivity of Escherichia coli B was first described more than 50 years ago, and the genetic locus responsible for the trait was subsequently identified as lon (encoding Lon protease). We now show that both E. coli B and the first reported E. coli K-12 lon mutant, AB1899, carry IS186 insertions in opposite orientations at a single site in the lon promoter region and that this site represents a natural hot spot for transposition of the insertion sequence (IS) element. Our analysis of deposited sequence data for a number of other IS186 insertion sites permitted the deductions that (i) the consensus target site sequence for IS186 transposition is 5'-(G)(> or =4)(N)(3-6)(C)(> or =4)-3', (ii) the associated host sequence duplication varies within the range of 6 to 12 bp and encompasses the N(3-6) sequence, and (iii) in a majority of instances, at least one end of the duplication is at the G-N (or N-C) junction. IS186-related sequences were absent in closely related bacterium Salmonella enterica serovar Typhimurium, indicating that this IS element is a recent acquisition in the evolutionary history of E. coli.

Prion-dependent switching between respiratory competence and deficiency in the yeast nam9-1 mutant

Nam9p is a protein of the mitochondrial ribosome. The respiration-deficient Saccharomyces cerevisiae strain MB43-nam9-1 expresses Nam9-1p containing the point mutation S82L. Respiratory deficiency correlates with a decrease in the steady level of some mitochondrially encoded proteins and the complete lack of mitochondrially encoded cytochrome oxidase subunit 2 (Cox2). De novo synthesis of Cox2 in MB43-nam9-1 is unaffected, indicating that newly synthesized Cox2 is rapidly degraded. Respiratory deficiency of MB43-nam9-1 is overcome by transient overexpression of HSP104, by deletion of HSP104, by transient exposure to guanidine hydrochloride, and by expression of the C-terminal portion of Sup35, indicating an involvement of the yeast prion [PSI(+)]. Respiratory deficiency of MB43-nam9-1 can be reinduced by transfer of cytosol from S. cerevisiae that harbors [PSI(+)]. We conclude that nam9-1 causes respiratory deficiency only in combination with the cytosolic prion [PSI(+)], presenting the first example of a synthetic effect between cytosolic [PSI(+)] and a mutant mitochondrial protein.