Induction of Chinese hamster HSP27 gene expression in mouse cells confers resistance to heat shock. HSP27 stabilization of the microfilament organization

Proteomic analysis of vascular endothelial growth factor-induced endothelial cell differentiation reveals a role for chloride intracellular channel 4 (CLIC4) in tubular morphogenesis

Formation of new vessels from pre-existing capillaries demands extensive reprogramming of endothelial cells through transcriptional and post-transcriptional events. We show that 120 protein spots in a two-dimensional isoelectric focusing/electrophoretic analysis were affected during vascular endothelial growth factor-A-induced endothelial cell tubular morphogenesis in vitro, as a result of changes in charge or expression level of the corresponding proteins. For about 22% of the spots, the protein products could be identified, of which several previously have been implicated in cytoskeletal reorganization and angiogenesis. One such protein was heat shock protein 27, a chaperone involved in beta-actin rearrangement that was identified as regulated in degree of serine phosphorylation. We also identified regulation of chloride intracellular channel 4 (CLIC4), the expression of which decreased during tubular morphogenesis. CLIC4 was expressed at high levels in resting vessels, whereas expression was modulated during pathological angiogenesis such as in tumor vessels. The subcellular localization of CLIC4 in endothelial cells was dependent on whether cells were engaged in proliferation or tube formation. Antisense- and small interfering RNA-mediated suppression of CLIC4 expression led to arrest in tubular morphogenesis. Our data implicate CLIC4 in formation of a vessel lumen.

Blocking tumor cell migration and invasion with biphenyl isoxazole derivative KRIBB3, a synthetic molecule that inhibits Hsp27 phosphorylation

Cell migration is a prerequisite for cancer invasion and metastasis, suggesting cell motility as a potential therapeutic target for cancer treatment. A synthetic library was screened to identify inhibitors of tumor cell migration. From this, we discovered that CAC-1098 (aurintricarboxylic acid) and CBI-0997 (5-(2,4-dimethoxy-5-ethylphenyl)-4-(4-bromophenyl) isoxazole) inhibited migration of MDA-MB-231 cells with IC50 = 5 and 50 nM, respectively. We synthesized KRIBB3 (5-(5-ethyl-2-hydroxy-4-methoxyphenyl)-4-(4-methoxyphenyl) isoxazole) by replacing the bromide group of CBI-0997 with a methoxyl group. Like CBI-0997, KRIBB3 has anti-migratory and anti-invasive activities in MDA-MB-231 cells. Because KRIBB3 has a better drug-like structure, we focused our effort on further understanding its anti-migratory mechanism. Biotinyl-KRIBB3 was synthesized as an affinity probe for identification of KRIBB3-binding proteins. Using affinity chromatography, we identified Hsp27 as a target protein of KRIBB3 in vitro. Treatment of MDA-MB-231 cells with phorbol 12-myristate 13-acetate induced protein kinase C-dependent phosphorylation of Hsp27 and tumor cell migration. In contrast, treatment of MDA-MB-231 cells with KRIBB3 blocked phorbol 12-myristate 13-acetate-induced phosphorylation of Hsp27 and tumor cell migration. Furthermore, overexpression of Hsp27 antagonized the inhibitory effect of KRIBB3 on tumor cell invasion, and knockdown of Hsp27 using small interfering RNA inhibited tumor cell migration. Overall, our results demonstrate that KRIBB3 inhibits tumor cell migration and invasion by blocking protein kinase C-dependent phosphorylation of Hsp27 through its direct binding to Hsp27.

Overexpression of heat-shock protein 20 in rat heart myogenic cells confers protection against simulated ischemia/reperfusion injury

AIM

To explore whether overexpression of the small heat shock protein HSP20 in rat cardiomyocytes protects against simulated ischemia/reperfusion (SI/R) injury.

METHODS

Recombinant adenovirus expressing HSP20 was used to infect rat H9c2 cardiomyocytes at high efficiency, as assessed by green fluorescent protein. H9c2 cells were subjected to SI/R stress; survival was estimated through assessment of lactate dehydrogenase and cell apoptosis through caspase-3 activity.

RESULTS

Overexpression of HSP20 decreased lactate dehydrogenase release by 21.5% and caspase-3 activity by 58.8%. Pretreatment with the protein kinase C inhibitor Ro-31-8220 (0.1 micromol/L) for 30 min before SI/R canceled the protective effect of HSP20. The selective mitochondrial K+ATP channel inhibitor 5-hydroxydecanoate (100 micromol/L) had a similar effect. However, the non-selective K+ATP channel inhibitor glibenclamide (100 micromol/L) had no significant effect.

CONCLUSION

These data indicate that the protective effect of HSP20 in vitro is primarily due to reduced necrotic and apoptotic death of cardiomyocytes, possibly via the protein kinase C/mitochondrial K+ATP pathway.

Constitutive expression of heat shock protein p23 correlates with proneural territories in imaginal discs ofDrosophila melanogaster

2-DE followed by MALDI-TOF was used to purify and identify a Drosophila protein (catalogued as SSP 6002) that showed marked differences in the level of expression in the different imaginal discs of third instar larvae. Fingerprinting showed that the spot of interest was the heat shock 23 polypeptide (hsp23). We characterized the kinetics of its induction by heat shock in wing imaginal discs and raised an antiserum against the denatured protein, which recognizes a single unphosphorylated spot on 2-D gels. The difference in its expression in discs was corroborated by analyzing its level in the imaginal discs of postbithorax mutants. We also investigated the developmental expression of hsp23 in imaginal discs with antiserum raised against the native protein. Its spatial and temporal pattern of expression is related to the proneural territories and maintained even under heat shock conditions. In addition, its pattern of expression is regulated by transcription factors and signaling pathways (notch and epidermal growth factor receptor) involved in proneural specification.

Small heat shock protein 27 (Hsp27) expression is highly induced in rat myometrium during late pregnancy and labour

The underlying mechanisms that regulate uterine contractions during labour are still poorly understood. A candidate regulatory protein is heat shock protein 27 (Hsp27). It belongs to the small heat shock protein family and can regulate actin cytoskeleton dynamics, act as a chaperone, and may regulate contractile protein activation. As a result, we hypothesized that Hsp27 expression would be highly induced during late pregnancy and labour. Hsp27 mRNA expression was significantly elevated (P <0.05) on days 17 to 22 of gestation. In addition, immunoblot analysis demonstrated that detection of total Hsp27 increased (P <0.05) between day 21 and 1 day post-partum (PP) inclusive. Since phosphorylation of Hsp27 has been reported to be a prerequisite for smooth muscle contraction, we examined the temporal and spatial expression of Ser-15 phosphorylated Hsp27. Immunoblot analysis showed that the detection of Ser-15 phosphorylated Hsp27 significantly increased (P <0.05) between days 19 and 23 (active labour) inclusive, in parallel with detection of total Hsp27. Immunocytochemical analysis of Ser-15 phosphorylated Hsp27 expression in situ demonstrated that phosphorylated Hsp27 in circular muscle became detectable in peri-nuclear and membrane regions on days 19 to 22, but was primarily restricted to the cytoplasm on days 23 to PP. In contrast, phosphorylated Hsp27 in longitudinal muscle was primarily detected in myocyte membranes on days 15 to 22, and then also became detectable in the cytoplasm of myocytes on days 23 and PP. Our results demonstrate that Hsp27 expression is highly upregulated during late pregnancy and labour and suggest that Hsp27 is a potential candidate contraction-associated protein.

JWA--a novel environmental-responsive gene, involved in estrogen receptor-associated signal pathway in MCF-7 and MDA-MB-231 breast carcinoma cells

The pyrethroid insecticide fenvalerate and the organophosphorus insecticide phoxim are now the most widely used agents for indoor pest control in China. Fenvalerate was shown to mimic estrogenic activity, whereas phoxim did not induce similar effects. Our previous studies demonstrated that JWA, a novel retinoic acid-inducible and cytoskeleton-associated gene, is also a potential environmental-responsive gene with increased expression to oxidative and heat-shock stresses. In the present study, the influence of both fenvalerate and phoxim was examined on the expression of JWA in MCF-7 (ER+) and MDA-MB-231 (ER-) human breast carcinoma cell lines. Concentrations of 0.01, 1, and 100 micromol/L of fenvalerate or phoxim were selected to treat both MCF-7 and MDA-MB-231 cells at 1, 3, and 5 d, respectively. The MTT results only showed that fenvalerate stimulated MCF-7 cell proliferation. Western blot assay was employed to detect the expressions of JWA and heat-shock proteins (hsp27 and hsp70). The results showed that after treatment with fenvalerate, both JWA and hsp70 showed similar expression patterns in the both cell lines; however, all the expression patterns of JWA, hsp27, and hsp70 were evidently reversed between ER+ and ER- cells. In addition, phoxim-treated cells showed a concentration-dependent relationship in JWA expression at all time points. These results suggest that JWA has similar functions with respect to hsp27 and hsp70, and might be a novel signal molecule in estrogen receptor-related signal transduction pathways in mammalian cells.

Substitution of the unique cysteine residue of murine Hsp25 interferes with the protective activity of this stress protein through inhibition of dimer formation

Murine small stress protein [heat shock protein 25 (Hsp25)] expression confers thermotolerance and protection against oxidative stress. Hsp25 is an oligomeric ATP-independent phospho-chaperone that can generate a glutathione-dependent pro-reducing state in cells that are normally devoid of small stress protein constitutive expression. Hsp25 contains only one cysteine residue (position 141) that is highly susceptible to oxidation. We have explored the significance of this reactive residue by generating a mutant in which cysteine-141 was substituted by an alanine residue (C141A mutant). We report here that the C141A mutant did not form dimers when expressed in either murine L929 or human HeLa cells, hence, demonstrating that cysteine-141 regulates Hsp25 dimer formation. The C141A mutant also interfered with the dimerization of human Hsp27, a constitutively expressed small stress protein in HeLa cells. The mutated polypeptide showed a decreased ability to multimerize, but its expression was still able to induce cellular protection against oxidative stress. The C141A mutant was, however, less efficient than the wild-type protein in counteracting staurosporine-induced apoptosis, and it showed no in vivo chaperone activity. Hence, the cellular protection mediated against different stressors may require specific structural organizations of Hsp25 that are differently altered by the mutation. Of interest, when expressed concomitantly with wild-type Hsp25, the C141A polypeptide induced a dominant-negative effect, a phenomenon that may result from the ability of small stress proteins to interact and multimerize with each other.

Small heat shock proteins HSP27 and alphaB-crystallin: cytoprotective and oncogenic functions

Heat shock protein-27 (HSP27) and alphaB-crystallin are ubiquitous small heat shock proteins whose expression is induced in response to a wide variety of physiological and environmental insults. They allow the cells to survive in otherwise lethal conditions. Various mechanisms have been proposed to account for the cytoprotective functions of these small heat shock proteins. First, these proteins are powerful molecular chaperones whose main function is to prevent the aggregation of nascent and stress-accumulated misfolded proteins. Second, they interact directly with various components of the tightly regulated programmed cell death machinery, upstream and downstream of the mitochondrial events. Third, they appear to play a role in the proteasome-mediated degradation of selected proteins. Both HSP27 and alphaB-crystallin were also proposed to participate in the development of neurodegenerative diseases and malignant tumors in which their overexpression could induce drug resistance. Altogether, these properties suggest that these small heat shock proteins are appropriate targets for modulating cell death pathways.

Preheating accelerates mitogen-activated protein (MAP) kinase inactivation post-heat shock via a heat shock protein 70-mediated increase in phosphorylated MAP kinase phosphatase-1

Heat shock (HS) activates mitogen-activated protein (MAP) kinases. Although prior exposure to nonlethal HS makes cells refractory to the lethal effect of a subsequent HS, it is unclear whether this also occurs in MAP kinase activation. This study was undertaken to evaluate the effect of a heat pretreatment on MAP kinase activation by a subsequent HS and to elucidate its possible mechanism. Preheating did not make BEAS-2B cells refractory to extracellular signal-regulated protein kinase (ERK) and c-Jun N-terminal kinase (JNK) activation by a second HS but accelerated their inactivation after HS. The rapid inactivation of ERK and JNK was dependent on de novo protein synthesis and associated with the up-regulation of heat shock protein 70 (HSP70). Moreover, the inhibition of phosphatase activity reversed this rapid inactivation. MAP kinase phosphatase-1 (MKP-1) expression was increased by HS, and the presence of its phosphorylated form (p-MKP-1) correlated with the observed rapid ERK and JNK inactivation. Blocking induction of p-MKP-1 with antisense MKP-1 oligonucleotides suppressed the rapid inactivation of ERK and JNK in preheated cells. HSP70 overexpression caused the early phosphorylation of MKP-1. Moreover, MKP-1 phosphorylation and the rapid inactivation of ERK were inhibited by blocking HSP70 induction in preheated cells. In addition, MKP-1 was insolubilized by HS, and HSP70 associated physically with MKP-1, suggesting that a chaperone effect of HSP70 might have caused the early phosphorylation of MKP-1. These results indicate that preheating accelerated MAP kinase inactivation after a second HS and that this is related to a HSP70-mediated increase in p-MKP-1.

Conserved methionines in chloroplasts

Heat shock proteins counteract heat and oxidative stress. In chloroplasts, a small heat shock protein (Hsp21) contains a set of conserved methionines, which date back to early in the emergence of terrestrial plants. Methionines M49, M52, M55, M59, M62, M67 are located on one side of an amphipathic helix, which may fold back over two other conserved methionines (M97 and M101), to form a binding groove lined with methionines, for sequence-independent recognition of peptides with an overall hydrophobic character. The sHsps protect other proteins from aggregation by binding to their hydrophobic surfaces, which become exposed under stress. Data are presented showing that keeping the conserved methionines in Hsp21 in a reduced form is a prerequisite to maintain such binding. The chloroplast generates reactive oxygen species under both stress and unstressed conditions, but this organelle is also a highly reducing cellular compartment. Chloroplasts contain a specialized isoform of the enzyme, peptide methionine sulfoxide reductase, the expression of which is light-induced. Recombinant proteins were used to measure that this reductase can restore Hsp21 methionines after sulfoxidation. This paper also describes how methionine sulfoxidation-reduction can be directly assessed by mass spectrometry, how methionine-to-leucine substitution affects Hsp21, and discusses the possible role for an Hsp21 methionine sulfoxidation-reduction cycle in quenching reactive oxygen species.

Proteomics in cancer cell research: an analysis of therapy resistance

Proteomics, the global analysis of expressed cellular proteins, provides powerful tools for the detailed comparison of proteins from normal and neoplastic tissue. In particular, cancer cell culture models are suited for applying proteomics techniques, such as two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and mass spectrometry, to identify specific protein expression profiles and/or proteins that may be associated with a defined phenotype of the cancer cells. As an instance of such an application of proteomics techniques, the detailed proteome analyses of different drug-resistant and thermoresistant cancer cell lines will be discussed. Finally, the potential roles of newly identified factors in a distinct biological mechanism have to be proven by functional studies. This experimental validation strategy will be discussed for two different factors identified by 2D-PAGE analyses of drug-resistant carcinoma cell lines, the "transporter associated with antigen presentation 1" (TAP1) and 14-3-3sigma.

Nuclear and cytoskeletal alterations of in vitro matured porcine oocytes under hyperthermia

The effects of heat shock (HS) on the nucleus and cytoskeleton of in vitro matured pig oocytes were examined in this study. Porcine cumulus-oocyte complexes (COCs) were aspirated from 3 to 6 mm diameter follicles and subjected to standard in vitro maturation (IVM) procedures for 42 hr. In Experiment 1, IVM-derived oocytes were then randomly allocated to different HS treatments at 41.5 degrees C for 0 (control, C0h, n = 101), 1 (HS1h, n = 113), 2 (HS2h, n = 104), and 4 hr (HS4h, n = 111), respectively. An additional control group of oocytes was cultured for 4 hr without HS (C4h, n = 93). Immunocytochemical staining was performed using anti-tubulins and FITC-conjugated mouse IgG for microtubule (MT) labeling. The chromatin and microfilaments (MFs) were stained using Hoechst 33342 and rhodamine-phalloidin, respectively. In the severe HS (4 hr), the chromosomes of the MII oocytes became an aggregated chromatin structure and separated into groups. The spindle MTs were completely depolymerized or formed MT arrays. The relative fluorescence intensity (RFI) or amount of the MF structures including transzona processes (TZPs), vitelline ring (VR), and pericytoplasmic MF, were changed in various degrees. The reversibility of these alterations in the chromatin and the cytoskeleton depended on the duration of the HS. In general, abnormalities in the chromosomes, spindle MTs and the percentages of oocytes with pericytoplasmic MTs increased with length of HS treatment. The size of the spindle and the RFI of MFs in the HS oocytes were also altered. The significant changes in the nucleus and the cytoskeleton in porcine oocytes after HS may be associated with reduced development under hyperthermia and, perhaps, with the low pregnancy rates in domestic species during hot seasons.

In vivo heat shock preconditioning mitigates calcium overload during ischaemia/reperfusion in the isolated, perfused rat heart

Heat shock (HS) pretreatment of the heart is effective in mitigating the deleterious effects of ischaemia/reperfusion. The main objective of this study was to determine whether the beneficial effect of HS is associated with the preservation of intracellular Ca2+ handling in the ischaemic/reperfused, isolated rat heart. Twenty-four hours after raising body core temperature to 42 degrees C for 15 min, rat hearts were perfused according to Langendorff and subjected to 30 min ischaemia followed by 20 min reperfusion. Cyclic changes of cytoplasmic calcium ion [Ca2+i] levels were measured by surface fluorometry using Indo-1 AM. Reperfused HS hearts showed improved recovery of contractile function compared with control hearts: end-diastolic pressure: 45+/-11 vs. 64+/-22 mmHg; developed pressure: 72+/-12 vs. 41+/-20 mmHg; maximum rate of pressure increase (+dP/dtmax): 1,513+/-305 vs. 938+/-500 mmHg/s; maximum rate of pressure decrease (-dP/dtmax): -1,354+/-304 vs. -806+/-403 mmHg/s. HS hearts displayed a significantly lower end-diastolic cytosolic [Ca2+] ([Ca2+]i) after reinstallation of flow. The dynamic parameters of the Ca2+i transients, i.e. the maximum rate of increase/decrease (+/-dCa2+i/dtmax) and amplitude, did not differ between reperfused control and HS hearts. The novel finding of this study is that improved performance of the HS-preconditioned heart after an ischaemic insult is associated with a reduced end-diastolic Ca2+i load, and most likely, preserved Ca2+ sensitivity of the myocardial contractile machinery.

Inactivity-induced modulation of Hsp20 and Hsp25 content in rat hindlimb muscles

Denervation decreases small heat shock protein (HSP) content in the rat soleus muscle; however, it is unknown whether this change is due to inactivity or absence of a nerve-muscle connection. Spinal cord isolation (SI) is a model of inactivity with an intact neuromuscular connection. After 7 days of SI, Hsp20 and Hsp25 levels in the soleus, plantaris, and adductor longus muscles were lower than in control rats, whereas Hsp20 was unchanged and Hsp25 increased in the tibialis anterior. The results for the soleus indicate that these small HSPs respond to inactivity and that this response is not influenced by neural activity-independent factors. Furthermore, the data indicate that these HSPs are impacted to a greater degree in muscles that are predominantly slow or have an antigravity function than in flexor muscles. Understanding the regulation of these HSPs during chronic reductions in neuromuscular activity may have valuable applications for conditions such as spinal cord injury.

Overexpression of heat shock protein Hsp27 protects against cerulein-induced pancreatitis

BACKGROUND & AIMS

Heat shock protein (Hsp) 27 regulates actin cytoskeletal dynamics, and overexpression of Hsp27 in fibroblasts protects against stress in a phosphorylation-dependent manner. Induction of Hsps occurs in acute pancreatitis, but Hsp27 has not been ascribed a specific role. To examine whether Hsp27 would ameliorate acute pancreatitis, we generated transgenic mice overexpressing human Hsp27 (huHsp27) or Hsp27 with the phosphorylatable residues Ser(15,78,82) mutated to aspartic acid (huHsp27-3D) to mimic phosphorylation or to alanine (huHsp27-3A), which is nonphosphorylatable.

METHODS

huHsp27 was expressed at high levels in the exocrine pancreas by use of a cytomegalovirus promoter. Protein expression was analyzed by Western blotting and immunofluorescence. Acute pancreatitis was induced with 6 or 12 hourly cerulein injections (50 microg/kg intraperitoneally) and its severity assessed by measuring serum amylase and lipase levels, pancreatic trypsin activity, edema, and morphologic changes by quantitative scoring of multiple histologic sections and visualization of filamentous actin. Systemic inflammatory effects were monitored by measuring lung myeloperoxidase activity (a marker of neutrophil infiltration).

RESULTS

huHsp27 protein was overexpressed in the pancreas and localized to pancreatic acini. Acute pancreatitis was ameliorated by overexpression of huHsp27 and the huHsp27-3D mutant, which were associated with suppression of pancreatic trypsin activity and acinar cell injury and preservation of the actin cytoskeleton. In contrast, these changes were unaffected by overexpression of the nonphosphorylatable huHsp27-3A mutant.

CONCLUSIONS

Pancreatic overexpression of huHsp27 protects against cerulein-induced acute pancreatitis in a specific phosphorylation-dependent manner and is associated with preservation of the actin cytoskeleton.

Influences of Follicular Size on Parthenogenetic Activation and in Vitro Heat Shock on the Cytoskeleton in Cattle Oocytes

The availability of cow ovaries from the slaughterhouse has been very limited in Taiwan. To maximize the use of cow ovaries for research purposes, whole ovary dissection was performed and the developmental competence of the oocytes derived from different sizes of follicles was assessed by the rates of in vitro maturation (IVM) and parthenogenetic activation of the oocytes in Experiment 1 (Exp 1). Cumulus-oocyte complexes (COCs) derived from small (1-2 mm) and large (3-8 mm) follicles were subjected to standard IVM culture for 24 h. Mature oocytes were selected and then parthenogenetically activated using A23187 (5 microm, 5 min) or thimerosal (200 microm, 10 min) alone or combined with 6-dimethylaminopurine (2.5 mm and 3.5 h, respectively). Activation rates of the oocytes, neither from the large nor small follicles, were affected by different activation treatments (single or combined stimuli). Whereas maturation rates for the oocytes from large follicles were superior to those from small follicles in both the single (59% vs 45%) and combined treatments (76% vs 40%; p < 0.05). To understand how prolonged heat shock (HS) influences cytoskeletal configurations of mature bovine oocytes, in Experiment 2 (Exp 2), matured oocytes derived from large follicles were randomly allocated to different durations of HS treatments at 41.5 degrees C for 0 (C0h, control, n = 12), 1 (HS1h, n = 28), 2 (HS2h, n = 31), and 4 h (HS4h, n = 30). An additional control group was cultured for 4 h without HS (38.5 degrees C, 4 h, n = 35). Alterations in nuclear structures, microtubules (MTs), and microfilaments (MFs) of the oocytes were examined. Abnormalities in the chromosomes, spindle MTs and the percentages of oocytes with cytoplasmic MTs increased with time of HS treatment. The intensity of the MF distribution in the HS oocytes was also altered. Significant changes in the cytoskeleton after HS may be associated with the reduced development under hyperthermia and, perhaps, with the low pregnancy rates of the animals during hot seasons.

Proteome comparison of alveolar macrophages with monocytes reveals distinct protein characteristics

Alveolar macrophages (AMs) are a subset of tissue macrophages situated in the alveolar milieu. Compared with their precursor blood monocytes, AMs exhibit distinct physiologic functions unique to their anatomic location. However, the molecular details that control monocyte differentiation into AMs remain unknown. This study employed a proteomic approach to define protein characteristics that distinguish AMs from monocytes. AMs and monocytes were obtained from six nonsmoking, healthy donors. Whole cell lysates from each donor's AMs and monocytes were analyzed by two-dimensional (2D) gel electrophoreses. The protein density for each protein spot in a 2D gel was compared between these two cell types. Proteins that demonstrated consistent level changes of greater than 2.5-fold in all six donors were subjected to tandem mass spectrometry for protein identity. Using this process, we revealed proteome changes in AMs that relate to their physiologic roles in proteolysis, actin reorganization, and cellular adaptation in the unique alveolar milieu. By comparison, blood monocytes displayed higher levels of the proteins involved in transcription, metabolism, inflammation, and in the control of proteolysis. These results provide new insights into the biology of mononuclear phagocytes and set a basis for future causality studies.

Essential Role of the NH2-terminal WD/EPF Motif in the Phosphorylation-activated Protective Function of Mammalian Hsp27

Hsp27 is expressed at high levels after mild heat shock and contributes to making cells extremely resistant to subsequent treatments. The activity of the protein is regulated at the transcriptional level, but also by phosphorylation, which occurs rapidly during stress and is responsible for causing the dissociation of large 700-kDa Hsp27 oligomers into dimers. We investigated the mechanism by which phosphorylation and oligomerization modulate the protective activity of Chinese hamster Hsp27. In contrast to oligomer dissociation, which only required Ser90 phosphorylation, activation of Hsp27 thermoprotective activity required the phosphorylation of both Ser90 and Ser15. Replacement of Ser90 by Ala90, which prevented the dissociation of the oligomer upon stress, did cause a severe defect in the protective activity. Dissociation was, however, not a sufficient condition to activate the protein because replacement of Ser15 by Ala15, which caused little effect in the oligomeric organization of the protein, also yielded an inactive protein. Analyzes of mutants with short deletions in the NH2 terminus identified the Hsp27 WD/EPF or PF-rich domain as essential for protection, maintenance of the oligomeric structure, and in vitro chaperone activity of the protein. In light of a three-dimensional model of Hsp27 based on the crystallographic structure of wheat Hsp16.9, we propose that the conserved WD/EPF motif of mammalian Hsp27 mediates important intramolecular interactions with hydrophic surfaces of the alpha-crystallin domain of the protein. These interactions are destabilized by Ser90 phosphorylation, making the motif free to interact with heterologous molecular targets upon the additional phosphorylation of the nearby Ser15.

Protein cryoprotective activity of a cytosolic small heat shock protein that accumulates constitutively in chestnut stems and is up-regulated by low and high temperatures

Heat shock, and other stresses that cause protein misfolding and aggregation, trigger the accumulation of heat shock proteins (HSPs) in virtually all organisms. Among the HSPs of higher plants, those belonging to the small HSP (sHSP) family remain the least characterized in functional terms. We analyzed the occurrence of sHSPs in vegetative organs of Castanea sativa (sweet chestnut), a temperate woody species that exhibits remarkable freezing tolerance. A constitutive sHSP subject to seasonal periodic changes of abundance was immunodetected in stems. This protein was identified by matrix-assisted laser-desorption ionization time of flight mass spectrometry and internal peptide sequencing as CsHSP17.5, a cytosolic class I sHSP previously described in cotyledons. Expression of the corresponding gene in stems was confirmed through cDNA cloning and reverse transcription-PCR. Stem protein and mRNA profiles indicated that CsHSP17.5 is significantly up-regulated in spring and fall, reaching maximal levels in late summer and, especially, in winter. In addition, cold exposure was found to quickly activate shsp gene expression in both stems and roots of chestnut seedlings kept in growth chambers. Our main finding is that purified CsHSP17.5 is very effective in protecting the cold-labile enzyme lactate dehydrogenase from freeze-induced inactivation (on a molar basis, CsHSP17.5 is about 400 times more effective as cryoprotectant than hen egg-white lysozyme). Consistent with these observations, repeated freezing/thawing did not affect appreciably the chaperone activity of diluted CsHSP17.5 nor its ability to form dodecameric complexes in vitro. Taken together, these results substantiate the hypothesis that sHSPs can play relevant roles in the acquisition of freezing tolerance.

HSP70 interacts with ribosomal subunits of thermotolerant cells

The expression of heat shock or stress proteins (hsps) is a widespread response to stress that results in the protection of cells from subsequent insults, coined stress tolerance. Stress tolerance is apparently due to the preservation of several cellular structures and processes, such as translation. Protection of protein synthesis has been correlated with the presence of Hsp70. In the present study, Hsp70 was found to interact with translating ribosomes. This interaction is due to the preferential binding of Hsp70 to the 40S ribosomal subunit. Additionally, Hsp70 seems to interact weakly with nascent polypeptides within the 60S subunit. The interaction between Hsp70 and ribosomal subunits could also be observed in vitro conditions. Binding of Hsp70 to ribosomes was salt resistant, suggesting that this protein is not bound to transiently associated translational factors. Moreover, protection of protein synthesis requires new gene expression. We speculate that the binding of Hsp70 to ribosomes is part of a mechanism to guarantee the rapid and abundant protein synthesis during stress, particularly the translation of mRNAs encoding for hsps.

HSP25 Is Involved in Two Steps of the Differentiation of PAM212 Keratinocytes

HSP25 is a member of the small heat shock protein family. This 25-kDa protein exhibits a highly specific distribution during mouse embryonic development. Although multiple functions have been proposed for HSP25, the role it plays during differentiation is still unknown. High levels of HSP25 can be detected in embryonic and adult skin. During epidermis differentiation, the concentration of HSP25 increases with the distance of keratinocytes from the basal layer, in parallel with the extent of keratinization. We used an ex vivo cellular system, PAM212 cells, to analyze quantitatively and qualitatively the dynamics of HSP25 production and phosphorylation during the differentiation of keratinocytes. Our observations suggest that HSP25 is involved in two steps of PAM212 keratinocyte differentiation. Shortly after the induction of differentiation, a transient hyperphosphorylation of HSP25 seems to be essential for the expression of differentiation markers. Later, the chaperone-active form of HSP25 is organized progressively into characteristic aggregates involved in the dynamics of keratin filament networks.

Role of heat shock protein 27 in cytoskeletal remodeling of the airway smooth muscle cell

Remodeling of the airway smooth muscle (ASM) cell has been proposed to play an important role in airway hyperresponsiveness. Using a functional assay, we have assessed remodeling of the cultured rat ASM cell and the role of heat shock protein (HSP) 27 in that process. To probe remodeling dynamics, we measured spontaneous motions of an individual Arg-Gly-Asp-coated microbead that was anchored to the cytoskeleton. We reasoned that the bead could not move unless the microstructure to which it is attached rearranged; if so, then its mean square displacement (MSD) would report ongoing internal reorganizations over time. Each bead displayed a random, superdiffusive motion; MSD increased with time as approximately t(1.7), whereas an exponent of unity would be expected for a simple passive diffusion. Increasing concentrations of cytochalasin-D or latrunculin-A caused marked increases in the MSD, whereas colchicine did not. Treatments with PDGF or IL-1beta, but not transforming growth factor-beta, caused decreases in the MSD, the extent of which rank-ordered with the relative potency of these agents in eliciting the phosphorylation of HSP27. The chemical stressors anisomycin and arsenite each increased the levels of HSP27 phosphorylation and, at the same time, decreased bead motions. In particular, arsenite prevented and even reversed the effects of cytochalasin-D on bead motions. Finally, ASM cells overexpressing phospho-mimicking human HSP27, but not wild-type or phosphorylation-deficient HSP27, exhibited decreases in bead motions that were comparable to the arsenite response. Taken together, these results show that phosphorylated HSP27 favors reduced bead motions that are probably due to stabilization of the actin cytoskeleton.

Differentiation stage-specific activation of p38 mitogen-activated protein kinase isoforms in primary human erythroid cells

p38alpha, p38beta, p38gamma, and p38delta are four isoforms of p38 mitogen-activated protein (MAP) kinase (MAPK) involved in multiple cellular functions such as cell proliferation, differentiation, apoptosis, and inflammation response. In the present study, we examined the mRNA expression pattern of each of the four isoforms during erythroid differentiation of primary erythroid progenitors. We show that p38alpha and p38gamma transcripts are expressed in early hematopoietic progenitors as well as in late differentiating erythroblasts, whereas p38delta mRNA is only expressed and active during the terminal phase of erythroid differentiation. On the other hand, p38beta is minimally expressed in early CD34(+) hematopoietic progenitors but not expressed in lineage-committed erythroid progenitors. We also determined the phosphorylation/activation of p38alpha, MAPK kinase 3/6, and MAPKAP-2 in response to erythropoietin and stem cell factor. We found that phosphorylation of p38alpha, MAPK kinase kinase 3/6 and MAPKAP-2 occurs only upon growth factor withdrawal in primary erythroid progenitors. Moreover, our data indicate that activation of p38alpha does not induce apoptosis or promote proliferation of erythroid progenitors. On the other hand, under steady-state culture conditions, both p38alpha and p38delta isoforms are increasingly phosphorylated activated in the terminal phase of differentiation. This increased phosphorylation/activity was accompanied by up-regulation of heat shock protein 27 phosphorylation. Finally, we demonstrate that tumor necrosis factor alpha, an inflammatory cytokine that is modulated by p38alpha, is expressed by differentiating erythroblasts and inhibition of p38alpha or tumor necrosis factor alpha results in reduction in differentiation. Taken together, our data demonstrate that both p38alpha and delta isoforms function to promote the late-stage differentiation of primary erythroid progenitors and are likely to be involved in functions related to erythrocyte membrane remodeling and enucleation.

A role for the cytoskeleton in heat-shock-mediated thermoprotection of locust neuromuscular junctions

A prior hyperthermic stress (heat shock) can induce thermoprotection of neuromuscular transmission in Locusta migratoria extensor tibiae muscle measured 4 h after the onset of the heat shock. It is not clear what effect an acute hyperthermic stress may have on the nervous system's ability to tolerate thermal stress, that is, before increased expression of heat-shock proteins. We found that over consecutive thermal stress tests, failure temperature was not altered in either heat-shock or control animals. This suggests that protective mechanisms are not established in the short term (within one hour). Various members of the heat-shock protein family interact with elements of the cytoskeleton. We found that preexposure of the preparation to cytoskeletal stabilizing drugs induced thermoprotection, while preexposure to cytoskeletal disrupting drugs disrupted the ability to confer and maintain thermoprotection. We conclude that thermoprotection relies on a stable cytoskeleton and suggest that members of the heat shock protein family are involved.

Cytoskeletal disruption and small heat shock protein translocation immediately after lengthening contractions

The purposes of this study were to determine whether, immediately after lengthening contractions, 1) levels of specific force-transmitting cytoskeletal elements are reduced in skeletal muscle cells and 2) cytosolic small heat shock proteins (HSPs) translocate to structures prone to disruption. Western blot analysis demonstrated decreased concentrations of z-disk proteins alpha-actinin and plectin and membrane scaffolding proteins dystrophin and beta-spectrin in muscle exposed to lengthening contractions compared with contralateral control muscle. Lengthening contractions also resulted in immediate translocation of constitutively expressed HSP25 and alphaB-crystallin from the soluble to the insoluble fraction of muscle homogenates, and cryosections showed translocation from a diffuse, cytosolic localization to striations that corresponded to z-disks. Lengthening contraction-induced translocation of HSP25 and alphaB-crystallin was associated with phosphorylation of these small HSPs, which may trigger their protective activity. In summary, these findings demonstrate loss of z-disk and membrane scaffolding proteins immediately after lengthening contractions, and concomitant translocation of HSP25 and alphaB-crystallin to the z-disk, which may help to stabilize or repair cytoskeletal elements at this site.

p38 mitogen-activated protein kinase protects glomerular epithelial cells from complement-mediated cell injury

In the passive Heymann nephritis (PHN) model of rat membranous nephropathy, complement C5b-9 causes sublytic injury of glomerular epithelial cells (GEC). We previously showed that sublytic concentration of C5b-9 triggers a variety of biological events in GEC. In the current study, we demonstrate that complement activates p38 MAPK in GEC and address the role of p38 in complement-mediated cell injury. When cultured rat GEC were stimulated with complement, p38 kinase activity and phosphorylation were increased by approximately 2.4-fold, compared with control. Treatment with p38 inhibitors significantly augmented complement-mediated cytotoxicity. In contrast, when the constitutively active mutant of transforming growth factor-beta-activated kinase 1 (TAK1), a kinase upstream of p38, was expressed in GEC in an inducible manner, cytotoxicity was significantly reduced, compared with uninduced cells. p38 inhibitors abolished the protective effect of TAK1 expression. By analogy to cultured cells, p38 activity was also increased in glomeruli from rats with PHN and treatment with the p38 inhibitor FR-167653 increased proteinuria. Complement induced phosphorylation of MAPK-associated protein kinase-2 (MAPKAPK-2), a kinase downstream of p38 in GEC. Heat shock protein (HSP27) is a cytoskeleton-interacting substrate of MAPKAPK-2. Overexpression of the wild-type HSP27, but not a non-phosphorylatable mutant, markedly reduced complement-mediated GEC injury. In summary, complement activates p38 MAPK in GEC in vitro and in glomeruli from rats with PHN. The activation of p38 MAPK appears to be cytoprotective for GEC against complement-mediated GEC injury. Phosphorylation of HSP27 may mediate this cytoprotection.

Translational thermotolerance provided by small heat shock proteins is limited to cap-dependent initiation and inhibited by 2-aminopurine

Heat shock results in inhibition of general protein synthesis. In thermotolerant cells, protein synthesis is still rapidly inhibited by heat stress, but protein synthesis recovers faster than in naive heat-shocked cells, a phenomenon known as translational thermotolerance. Here we investigate the effect of overexpressing a single heat shock protein on cap-dependent and cap-independent initiation of translation during recovery from a heat shock. When overexpressing alphaB-crystallin or Hsp27, cap-dependent initiation of translation was protected but no effect was seen on cap-independent initiation of translation. When Hsp70 was overexpressed however, both cap-dependent and -independent translation were protected. This finding indicates a difference in the mechanism of protection mediated by small or large heat shock proteins. Phosphorylation of alphaB-crystallin and Hsp27 is known to significantly decrease their chaperone activity; therefore, we tested phosphorylation mutants of these proteins in this system. AlphaB-crystallin needs to be in its non-phosphorylated state to give protection, whereas phosphorylated Hsp27 is more potent in protection than the unphosphorylatable form. This indicates that chaperone activity is not a prerequisite for protection of translation by small heat shock proteins after heat shock. Furthermore, we show that in the presence of 2-aminopurine, an inhibitor of kinases, among which is double-stranded RNA-activated kinase, the protective effect of overexpressing alphaB-crystallin is abolished. The synthesis of the endogenous Hsps induced by the heat shock to test for thermotolerance is also blocked by 2-aminopurine. Most likely the protective effect of alphaB-crystallin requires synthesis of the endogenous heat shock proteins. Translational thermotolerance would then be a co-operative effect of different heat shock proteins.

Thyroxine pretreatment increases basal myocardial heat-shock protein 27 expression and accelerates translocation and phosphorylation of this protein upon ischaemia

Thyroxine pretreatment increases the tolerance of the heart to ischaemia, and heat-shock protein 27 (HSP27) is considered to play an important role in cardioprotection. The present study investigated whether long-term thyroxine administration can induce changes in the expression, translocation and phosphorylation of HSP27 at baseline and upon ischaemic stress. L-Thyroxine (T(4)) was administered to Wistar rats (25 microg/100 g/day s.c.) for 2 weeks, while normal animals served as controls. Hearts from normal and thyroxine-treated rats were perfused in Langendorff mode and subjected to 10 or 20 min of zero-flow global ischaemia only or to 20 min of ischaemia followed by 45 min of reperfusion. Total and phospho-HSP27 expression were assessed at different times in the Triton-soluble (cytosol-membrane), S fraction, and the Triton-insoluble (cytoskeleton-nucleus) fraction, P fraction. Postischaemic recovery of left ventricular developed pressure at 45 min of reperfusion was expressed as % of the initial value. In hearts from thyroxine-treated animals, the levels of basal total HSP27 and phospho-HSP27 in the P fraction were significantly increased as compared to normal. In response to ischaemia, in hearts from thyroxine-treated rats, the levels of total HSP27 and phospho-HSP27 were found to be significantly increased in the P fraction at 10 and 20 min of ischaemia as compared to preischaemic values, whereas in normal hearts, the levels of total HSP27 and phospho-HSP27 were significantly increased at 20 min only. Postischaemic functional recovery was significantly greater in thyroxine-treated than in untreated hearts. In summary, long-term thyroxine pretreatment results in an increased basal expression and phosphorylation of HSP27 and in an earlier and sustained redistribution of HSP27 from the S to the P fraction in response to ischaemia. This effect might be of important therapeutic relevance.

Hsp27, Hsp70, and metallothionein in MDCK and LLC-PK1 renal epithelial cells: effects of prolonged exposure to cadmium

Cadmium is a widely distributed industrial and environmental toxin. The principal target organ of chronic sublethal cadmium exposure is the kidney. In renal epithelial cells, acute high-dose cadmium exposure induces differential expression of proteins, including heat shock proteins. However, few studies have examined heat shock protein expression in cells after prolonged exposure to cadmium at sublethal concentrations. Here, we assayed total cell protein, neutral red uptake, cell death, and levels of metallothionein and heat shock proteins Hsp27 and inducible Hsp70 in cultures of MDCK and LLC-PK1 renal epithelial cells treated with cadmium for 3 days. Treatment with cadmium at concentrations equal to or greater than 10 microM (LLC-PK1) or 25 microM (MDCK) reduced measures of cell vitality and induced cell death. However, a concentration-dependent increase in Hsp27 was detected in both cell types treated with as little as 5 microM cadmium. Accumulation of Hsp70 was correlated only with cadmium treatment at concentrations also causing cell death. Metallothionein was maximally detected in cells treated with cadmium at concentrations that did not reduce cell vitality, and further increases were not detected at greater concentrations. These results reveal that heat shock proteins accumulate in renal epithelial cells during prolonged cadmium exposure, that cadmium induces differential expression of heat shock protein in epithelial cells, and that protein expression patterns in epithelial cells are specific to the cadmium concentration and degree of cellular injury. A potential role for Hsp27 in the cellular response to sublethal cadmium-induced injury is also implicated by our results.

Administration of brain-derived neurotrophic factor suppresses the expression of heat shock protein 27 in rat retinal ganglion cells following axotomy

Optic nerve transection results in the apoptotic cell death of the majority of retinal ganglion cells by 14 days. The neurotrophin brain-derived neurotrophic factor (BDNF) enhances survival of retinal ganglion cells. In addition, the small heat shock protein Hsp27, with its anti-apoptotic effects, may be important for neuron survival following axotomy or trophic factor withdrawal. We recently reported the induction and expression of Hsp27 in a subset of retinal ganglion cells following axotomy. Here we have examined the effect of BDNF administration on the expression of Hsp27 in axotomized adult rodent retinal ganglion cells. Retinal ganglion cells were pre-labeled with Fluorogold prior to optic nerve transection and concomitant intraocular injection of BDNF or vehicle. Hsp27 immunofluorescence was examined in retinal sections from 4 to 28 days following injury. Consistent with previous survival studies, the number of Fluorogold-labeled retinal ganglion cells declined from 100% at 4 days to approximately 15% by 14 days following axotomy and vehicle injection. In contrast, with BDNF administration, retinal ganglion cell survival was maintained at 100% to 7 days following axotomy. We report that the number of Hsp27-positive injured retinal ganglion cells, as detected by immunohistochemical staining, was decreased by 50% in BDNF-treated retinas, when compared with vehicle-treated controls. This decreased expression of Hsp27 in response to BDNF treatment was seen both at early (4 days) and delayed (14 days) times. BDNF following optic nerve transection significantly reduced the expression of Hsp27 in retinal ganglion cells. These results indicate that BDNF may down-regulate alternate cell survival pathways, including the stress-induced expression of Hsp27, and may help to explain the failure of chronic neurotrophin treatment to maintain long-term retinal ganglion cell survival.

Identification of alpha-tubulin as an hsp105alpha-binding protein by the yeast two-hybrid system

Hsp105alpha is a mammalian stress protein that belongs to the HSP105/110 family. Hsp105alpha prevents stress-induced apoptosis in neuronal cells and binds to Hsp70/Hsc70 and suppresses the Hsp70 chaperone activity in vitro. In this study, to further elucidate the function of Hsp105alpha, we searched for Hsp105alpha-binding proteins by screening a mouse FM3A cell cDNA library with full-length Hsp105alpha using the yeast two-hybrid system and obtained alpha-tubulin as an Hsp105alpha-binding protein. Hsp105alpha bound directly to alpha-tubulin both in vitro and in vivo. Indirect immunofluorescence analysis with anti-Hsp105 and anti-alpha-tubulin antibodies indicated that Hsp105alpha was colocalized with microtubules. Furthermore, the disorganization of microtubules induced by heat shock was prevented in Hsp105alpha-overexpressing COS-7 cells. These findings suggested that Hsp105alpha associates with alpha-tubulin and microtubules in cells and plays a role in protection of microtubules under conditions of stress.

Interleukin-11-induced heat shock protein 25 confers intestinal epithelial-specific cytoprotection from oxidant stress

BACKGROUND & AIMS

The mechanisms of interleukin-11 (IL-11) cytoprotection in intestinal epithelial injury are largely unknown. IL-11 protects barrier integrity during oxidant stress, a common endpoint of numerous types of intestinal injury including ischemia and immune-mediated inflammation. Because heat shock proteins (hsp) are cytoprotective in intestinal epithelia, we hypothesized that IL-11-conferred cytoprotection is mediated by inducible hsps.

METHODS

IL-11 receptor (IL-11R) activation was determined using phospho-specific antibodies to STAT3. IL-11 induction of hsp72 and hsp25 was determined by immunoblot in IEC-18 crypt and young adult mouse colon colonic epithelial cells. Epithelial resistance to oxidant injury by monochloramine was determined by (51)Cr release. Stable hsp anti-sense IEC-18 cell clones were obtained by electroporation and hygromycin B selection. The IL-11 effect on hsp25 distribution was characterized by analysis of Triton x-100 insoluble fractions, 2-D isoelectric focusing gels, and confocal microscopy.

RESULTS

IL-11R signaling was detected in all cells under study. IL-11 induces hsp25 in an intestinal epithelial-specific manner that significantly preserves cellular viability in the presence of monochloramine. This effect was significantly reversed in intestinal epithelia stably expressing anti-sense to hsp25. IL-11 induced a shift of hsp25 to Triton x-100 insoluble fractions containing cytoskeletal elements, which was not associated with altered hsp25 phosphorylation. The shift was not paralleled by increased hsp25 co-localization with F-actin by confocal microscopy.

CONCLUSIONS

The induction of hsp25 by IL-11 confers epithelial-specific cytoprotection that is independent of phosphorylation-dependent co-localization of hsp25 to F-actin, thereby contributing to the protective effects of IL-11 in models of intestinal epithelial injury.

HSP27 is markedly induced in Schwann cell columns and associated regenerating axons

It is well known that regenerating axons enter Schwann cell (SC) columns, within which they grow to reinnervate the appropriate targets. The current study detected a marked induction of a 27-kDa heat shock protein (HSP27) in the SC columns of crush-injured rat sciatic nerves. Immunohistochemical studies showed the first appearance of strong HSP27-immunoreactive linear structures in the proximal stump near an injury site 7 h after an operation. The HSP27-immunoreactive linear structures crossed the injury site to the distal stump 2 days after the operation. They then extended in a more proximal and more distal direction and were found to have propagated through the entire length of the nerve 1 week after the operation. This pattern of expression was maintained until 3 weeks after the operation. Double-immunofluorescent labeling and confocal laser microscopy confirmed that the linear structures consisted of SC columns and associated multiple axons. The HSP27-immunoreactive SC columns expressed glial fibrillary acidic protein, but not S-100 protein. Electron microscopy and immunoelectron microscopy demonstrated that reactive Schwann cells (SCs) and the associated axons with an outgrowing profile exhibited a strong immunoreactivity to HSP27, with the former containing a greater number of bundles of intermediate filaments. It is suggested that HSP27 may play an essential role in axonal outgrowth, especially by contributing to cytoskeletal dynamics in SCs.

Pulpal regeneration after cavity preparation, with special reference to close spatio-relationships between odontoblasts and immunocompetent cells

The regeneration process of the odontoblast cell layer incident to tooth injury, especially its relationship with immunocompetent cells in pulp healing, has not been fully understood. The purpose of the present study was to clarify this relationship between odontoblasts and immunocompetent cells in the process of pulp regeneration following cavity preparation in rat molars by immunocytochemistry for heat shock protein (Hsp) 25 as well as class II major histocompatibility complex (MHC) molecules. In untreated control teeth, intense Hsp 25-immunoreactivity was found in the cell bodies of odontoblasts and their processes within the predentin, whereas class II MHC-positive cells were predominantly located beneath the odontoblast cell layer. Cavity preparation caused the destruction of the odontoblast layer to form an edematous lesion and the shift of class II MHC-positive cells with the injured odontoblasts toward the pulp core at the affected site. Some damaged odontoblasts without apparent cytoplasmic processes, round in profile, retained the immunoreactivity for Hsp25, suggesting the survival of a part of the odontoblasts against artificial external stimuli. Twelve hours after cavity preparation, numerous class II MHC-positive cells appeared along the pulp-dentin border and extended their processes deep into the exposed dentinal tubules. By postoperative 72 hours, newly differentiated odontoblasts with Hsp 25-immunoreactivity were arranged at the pulp-dentin border, but the class II MHC-positive cells moved from the pulp-dentin border to the subodontoblastic layer. These findings indicate that the time course of changes in the expression of Hsp 25-immunoreactivity reflects the regeneration process of odontoblasts. The functional roles of Hsp 25-positive odontoblasts and immunocompetent cells such as class II MHC-positive cells in the process of pulp regeneration after cavity preparation are discussed in conjunction with our previous experimental data.

Heat shock protein 27 delivered via a herpes simplex virus vector can protect neurons of the hippocampus against kainic-acid-induced cell loss

Heat shock proteins are expressed in response to cellular stress and can protect cells from further stress and facilitate recovery. Heat shock protein 27 is of particular interest because it has been implicated in a range of protective roles including protein chaperoning, stabilising elements of the cytoskeleton and as an active inhibitor of apoptosis. In the present study, we have examined the potential of administration of exogenous HSP27 to confer protection against KA-induced neuronal cell death in vivo. We aimed to exploit the neurotropic specificity of herpes simplex virus-1 based virus vectors, which have been rendered replication-incompetent, to infect neurons of the hippocampus. The systemic administration of kainic acid, an analogue of glutamate, causes seizures resulting in neuronal damage and is an established animal model of epilepsy. Neuron loss is particularly prominent in the hippocampus and the mode of death is at least partly apoptotic in nature. We show that the overexpression of HSP27 in these neurons can significantly augment their survival following kainic acid administration. In contrast, injection of a control virus expressing beta-galactosidase does not confer protection. This is the first time that protection by exogenously expressed HSP27 has been demonstrated in an in vivo model of neuronal cell death.

Interaction of the small heat shock protein with molecular mass 25 kDa (hsp25) with actin

The interaction of heat shock protein with molecular mass 25 kDa (HSP25) and its point mutants S77D + S81D (2D mutant) and S15D + S77D + S81D (3D mutant) with intact and thermally denatured actin was analyzed by means of fluorescence spectroscopy and ultracentrifugation. Wild type HSP25 did not affect the polymerization of intact actin. The HSP25 3D mutant decreased the initial rate without affecting the maximal extent of intact actin polymerization. G-actin heated at 40-45 degrees C was partially denatured, but retained its ability to polymerize. The wild type HSP25 did not affect polymerization of this partially denatured actin. The 3D mutant of HSP25 increased the initial rate of polymerization of partially denatured actin. Heating at more than 55 degrees C induced complete denaturation of G-actin. Completely denatured G-actin cannot polymerize, but it aggregates at increased ionic strength. HSP25 and especially its 2D and 3D mutants effectively prevent salt-induced aggregation of completely denatured actin. It is concluded that the interaction of HSP25 with actin depends on the state of both actin and HSP25. HSP25 predominantly acts as a chaperone and preferentially interacts with thermally unfolded actin, preventing the formation of insoluble aggregates.

Interferon-gamma downregulates Hsp27 expression and suppresses the negative regulation of cell death in oral squamous cell carcinoma lines

Interferon-gamma (IFN-gamma) induced cell death in five oral squamous cell carcinoma (SCC) lines. Cell death was specific to IFN-gamma treatment and did not occur with either IFN-alpha or TNF-alpha. IFN-gamma did not induce typical apoptotic phenotype in cells, such as morphological changes and DNA ladder formation. Caspase-3 was partially activated by IFN-gamma. Protein levels of molecular chaperones were examined in cells treated with IFN-gamma. Among these, levels of heat shock protein 27 (Hsp27) were specifically reduced upon IFN-gamma treatment of oral SCC cells. Recombinant clones overexpressing Hsp27 were more resistant to IFN-gamma-induced cell death than parent cells. Conversely, cells expressing a dominant-negative mutant of Hsp27, in which three serine residues (15, 78 and 82) were replaced by glycine, were hypersensitive to the effects of IFN-gamma and exhibited a typical apoptotic phenotype. Pretreatment of cells with IFN-gamma enhanced apoptotic cell death induced by cisplatin. Our data suggest that IFN-gamma suppresses Hsp27 expression in oral SCC cells and blocks the inhibitory effects of this molecular chaperone on apoptotic cell death. Moreover, IFN-gamma initiates the transition of oral SCC cells to the proapoptotic and/or aborted apoptotic state. Hsp27 plays a crucial role in the inhibition of apoptosis of oral SCC cells. Our findings highlight the importance of employing IFN-gamma in combination with certain anticancer drugs as treatments for oral cancer. We suggest that Hsp27 plays a significant role in the IFN-gamma-induced sensitization of oral SCC cells to anticancer drugs.

Expression levels of heat shock proteins in enterocyte-like Caco-2 cells after exposure to Salmonella enteritidis

The enterocytes of the small intestine are occasionally exposed to pathogenic bacteria, such as Salmonella enteritidis 857, an etiologic agent of intestinal infections in humans. The expression of the heat shock response by enterocytes may be part of a protective mechanism developed against pathogenic bacteria in the intestinal lumen. We aimed at investigating whether S. enteritidis 857 is able to induce a heat shock response in crypt- and villus-like Caco-2 cells and at establishing the extent of the induction. To establish whether S. enteritidis 857 interfered with the integrity of the cell monolayer, the transepithelial electrical resistance (TEER) of filter-grown, differentiated (villus-like) Caco-2 cells was measured. We clearly observed damage to the integrity of the cell monolayer by measuring the TEER. The stress response was screened in both crypt- and villus-like Caco-2 cells exposed to heat (40-43 degrees C) or to graded numbers (10(1)-10(8)) of bacteria and in villus-like cells exposed to S. enteritidis 857 endotoxin. Expression of the heat shock proteins Hsp70 and Hsp90 was analyzed by polyacrylamide gel electrophoresis and immunoblotting with monoclonal antibodies. Exposure to heat or Salmonella resulted in increased levels of Hsp70 and Hsp90 in a temperature-effect or Salmonella-dose relationship, respectively. Incubation of Caco-2 cells with S. enteritidis 857 endotoxin did not induce heat shock gene expression. We conclude that S. enteritidis 857 significantly increases the levels of stress proteins in enterocyte-like Caco-2 cells. However, our data on TEER clearly indicate that this increase is insufficient to protect the cells.

Structure and properties of avian small heat shock protein with molecular weight 25 kDa

The primary structure of chicken small heat shock protein (sHsp) with apparent molecular weight 25 kDa was refined and it was shown that this protein has conservative primary structure 74RALSRQLSSG(83) at Ser77 and Ser81, which are potential sites of phosphorylation. Recombinant wild-type chicken Hsp25, its three mutants, 1D (S15D), 2D (S77D+S81D) and 3D (S15D+S77D+S81D), as well as delR mutant with the primary structure 74RALS-ELSSG(82) at potential sites of phosphorylation were expressed and purified. It has been shown that the avian tissues contain three forms of Hsp25 having pI values similar to that of the wild-type protein, 1D and 2D mutants that presumably correspond to nonphosphorylated, mono- and di-phosphorylated forms of Hsp25. Recombinant wild-type protein, its 1D mutant and Hsp25, isolated from chicken gizzard, form stable high molecular weight oligomeric complexes. The delR, 2D and 3D mutants tend to dissociate and exist in the form of a mixture of high and low molecular weight oligomers. Point mutations mimicking phoshorylation decrease chaperone activity of Hsp25 measured by reduction of dithiothreitol induced aggregation of alpha-lactalbumin, but increase the chaperone activity of Hsp25 measured by heat induced aggregation of alcohol dehydrogenase. It is concluded that avian Hsp25 has a more stable quaternary structure than its mammalian counterparts and mutations mimicking phosphorylation differently affect chaperone activity of avian Hsp25, depending on the nature of target protein and the way of denaturing.

Changes in oligomerization are essential for the chaperone activity of a small heat shock protein in vivo and in vitro

The ability of small heat shock proteins (sHSPs) to prevent thermal aggregation of other proteins may require disassembly and reassembly of sHSP oligomers. We investigated the role of changes in sHSP oligomerization by studying a mutant with reduced oligomeric stability. In HSP16.6, the single sHSP in the cyanobacterium Synechocystis sp. PCC 6803, the mutation L66A causes oligomer instability and reduced chaperone activity in vitro. Because thermotolerance of Synechocystis depends on HSP16.6, a phenotype that is enhanced in a deltaClpB1 strain, the effect of mutations can also be assayed in vivo. L66A causes severe defects in thermotolerance, suggesting that oligomeric stability of sHSPs is required for cellular function. This hypothesis was supported by a selection for intragenic suppressors of L66A, which identified mutations that stabilize oligomers of both L66A and wild-type HSP16.6. Analysis of both over- and under-oligomerizing mutants suggests that sHSPs must disassemble before they can release substrates. Furthermore, the suppressor mutations not only restore in vivo activity to L66A, they also ameliorate chaperone defects in vitro, and thus provide the first direct evidence for a chaperone function of an sHSP in cellular thermotolerance.

Expression of heat shock protein 27 (HSP27) in human temporomandibular joint discs of patients with internal derangement

Heat shock proteins (HSPs) are believed to represent a cellular stress response mechanism that protects intracellular proteins from damaging events. Some studies have demonstrated an enhanced expression of large-molecular-weight HSPs in diseased systematic joints. Small heat shock proteins, and among these HSP27, have been studied to a lesser extent. HSP27 has cytoprotective and biosynthetic functions within chondrocytes, and it is an estrogen-associated protein that is under hormonal modulation. To improve understanding at a molecular level of the pathophysiology of certain temporomandibular joint disorders, the authors carried out this immunohistochemical study to assess the presence of HSP27 in human TMJ discs. Twelve adult human TMJ discs (10 diseased and 2 healthy discs) and 5 TMJ fetal human discs were used in this study. Adult discs and TMJ tissues of human fetuses were fixed in 10% buffered formalin. Samples were then processed for histologic examination. Sections were immunohistochemically stained using the streptavidin-biotin detection method. No reaction product for HSP27 in the discs of fetuses was noted. HSP27 was weakly expressed in normal TMJ discs and highly up-regulated in discs of patients showing new vessel formation and chondroid metaplasia. Any correlation between gender and HSP27 was found in the sample, being the up-regulation of HSP27 related mostly to major histopathological changes. This different pattern of HSP27 immunostaining in human TMJ discs detected in the authors' specimens suggests that the expression of this small HSP is functionally modulated. In fact HSP27 up-regulates in internal derangement specimens with major histopathological changes; on the other hand, it is not expressed or only weakly expressed in TMJ discs of fetuses and normal TMJ discs.

Immunohistochemical localization of heat shock protein 25 (HSP 25) during root formation of the rat molar

The present study investigated the immunohistochemical localization of heat shock protein 25 (HSP 25) of rat molar teeth during root formation. Most, probably all, cells of the epithelial rest of Malassez (ERM cells) had immunoreaction for laminin, a marker protein for basement membrane. During root formation, HSP 25 immunoreactivity was observed in odontoblasts, cells at the subodontoblastic layer, and those in close proximity to the acellular cementum. HSP 25-immunopositive cells at the subodontoblastic layer were present only at the apical region. Most HSP 25-immunoreactive cells in close proximity to the cementum lacked laminin immunoreactivity. However, at postnatal day 28 a small number of cells showed immunoreaction for both HSP 25 and laminin at the cervical and bifurcational regions. Under the electron microscope, most HSP 25-immunoreactive cells along the surface of the cementum were round and contained rich organelles such as mitochondria and rough endoplasmic reticulum. They lay between fiber bundles of the periodontal ligament. The localization and morphological features of these HSP 25-immunoreactive cells resemble those of cementoblasts. On the other hand, HSP 25-immunoreactive cells at the cervical region were oval and contained few cell organelles. They were closely apposed to each other, and separated from the surrounding tissues with basal lamina. These features were similar to those of mature ERM cells. In contrast, cells with microvillus-like processes and relatively rich mitochondria, which were similar to immature ERM cells, had no immunoreaction for HSP 25. These results suggest that HSP 25 may be involved in shape alterations of ERM cells, cementoblasts, and odontoblasts during differentiation.

Hsp70 and thermal pretreatment mitigate developmental damage caused by mitotic poisons in Drosophila

To assess the ability of the heat-inducible molecular chaperone heat-shock protein 70 (Hsp70) to mitigate a specific developmental lesion, we administered the antimicrotubule drugs vinblastine (VB) and colchicine (COL) to larvae of Drosophila engineered to express differing levels of Hsp70 after heat pretreatment (HP). VB and COL decreased survival during metamorphosis, disrupted development of the adult eye and other structures as well as their precursor imaginal disks, and induced chromosome nondisjunction in the wing imaginal disk as indicated by the somatic mutation and recombination test (SMART) assay. Hsp70-inducing HP reduced many of these effects. For the traits viability, adult eye morphology, eye imaginal disk morphology, cell death in the eye imaginal disks, and single and total mutant clone formation in the SMART assay, HP reduced the impact of VB to a greater extent in Drosophila with 6 hsp70 transgenes than in a sister strain from which the transgenes had been excised. Because the extra-copy strain has higher levels of Hsp70 than does the excision strain but is otherwise almost identical in genetic background to the excision strain, these outcomes are attributable to Hsp70. The hsp70 copy number had a variable interaction with HP and COL administration.

Up-regulation of Hsp27 plays a role in the resistance of human colon carcinoma HT29 cells to photooxidative stress

The Photofrin-resistant cell line (HT29-P14) was used in the present study to investigate the mechanism(s) involved in Photofrin-mediated photodynamic therapy (PDT). We compared gene expression profiles between the resistant cell line and its parental cell line (HT29) using DNA microarray analysis. A significant up-regulation of small heat shock protein 27 (Hsp27) was found in HT29-P14 cells. The elevated Hsp27 level may play an important role in the resistance of HT29-P14 to Photofrin-PDT. To test this hypothesis, we stably transfected HT29 cells with human Hsp27 complementary DNA. The potential role of Hsp27 in the resistance to PDT was examined in Hsp27-overexpressing cells. Stable trasnfected cells (H13) showed an increased survival after Photofrin-PDT, suggesting that the up-regulation of Hsp27 is related to the induced resistance to Photofrin-PDT. Phosphorylation of Hsp27 has been suggested to play an important role in cytoprotection. We have examined the phosphorylation activity of Hsp27 among the parental and resistant cells, as well as the overexpression cells. An elevated level of Hsp27 resulted in an increased ability of phosphorylation in both resistant and overexpressing cells after PDT. The activation of the phosphorylation of Hsp27 induced by PDT was not mediated by the p38 mitogen-activated protein kinase. These data suggest that Hsp27 may play an important role in mediating the adaptive response to Photofrin-PDT-induced oxidative stress and that the pathways leading to Hsp27 phosphorylation may contribute to the resistance of the cells to photooxidative damage.

Injury to retinal ganglion cells induces expression of the small heat shock protein Hsp27 in the rat visual system

Optic nerve transection results in apoptotic cell death of most adult rat retinal ganglion cells that begins at 4 days and leaves few surviving neurons at 14 days post-injury [Berkelaar et al. (1994) J. Neurosci. 14, 4368-4374]. The small heat shock protein Hsp27 has recently been shown to play a role in sensory neuron survival following peripheral nerve axotomy [Lewis et al. (1999) J. Neurosci. 19, 8945-8953]. To investigate the role of Hsp27 in injured CNS sensory neurons, we have studied the induction and cell-specific expression of Hsp27 in rat retinal ganglion cells 1-28 days after optic nerve transection. Immunohistochemical results indicate that Hsp27 is not present at detectable levels in the ganglion cell layer of control (uninjured) or sham-operated control rats. In contrast, Hsp27 is detected in retinal ganglion cells from 4 to 28 days following axotomy. Furthermore, the percentage of surviving retinal ganglion cells that are Hsp27-positive increased over the same time period. Hsp27 is also detected in glial fibrillary acidic protein-positive astrocytes in the optic layer of the superior colliculus from 4 to 28 days after optic nerve transection. These experiments demonstrate that transection of the optic nerve results in the expression of Hsp27 in three distinct regions of the rat visual system: sensory retinal ganglion cells in the eye, glial cells of the optic tract, and astrocytes in the optic layer of the superior colliculus. Hsp27 may be associated with enhanced survival of a subset of retinal ganglion cells, providing evidence of a protective role for Hsp27 in CNS neuronal injury.