Structure, properties, and functions of the human small heat-shock protein HSP22 (HspB8, H11, E2IG1): A critical review

The role of heat shock protein B8 in neuronal protection against oxidative stress and mitochondrial dysfunction: A literature review

Excessive oxidative stress triggers cerebrovascular and neurodegenerative diseases resulting in acute and chronic brain injury. However, the underlying mechanisms remain unknown. Levels of small heat shock protein B8 (HSPB8), which is highly expressed in the brain, are known to be significantly elevated in cerebral injury models. Exogenous HSPB8 protects the brain against mitochondrial damage. One potential mechanism underlying this protection is that HSPB8 overexpression alleviates the mitochondria-dependent pathways of apoptosis; mitochondrial biogenesis, fission, and mitophagy. Overexpression of HSPB8 may therefore have potential as a clinical therapy for cerebrovascular and neurodegenerative diseases. This review provides an overview of advances in the protective effects of HSPB8 against excessive cerebral oxidative stress, including the modulation of mitochondrial dysfunction and potent signaling pathways.

Hsp22 pretreatment protection against LPS-induced hippocampal injury by alleviating neuroinflammation and apoptosis by regulating the NLRP3/Caspase1/IL-1β signaling pathway in mice

Neuroinflammation is an important reason for the occurrence and development of cognitive impairment. The Lentiviral vector Hsp22 was constructed for intracerebroventricular injection pretreatment, LPS was used to induce the cognitive impairment model in mice, and the Morris water maze was used to examine the changes in cognitive behavior in mice. LPS was used to induce BV-2 microglial cells, and plasmid pretreatment was used to overexpress Hsp22. HE staining, Nissl staining, immunohistochemistry, immunofluorescence, ELISA and protein blotting were used to examine microglial activation, changes in inflammatory factors, changes in pathway proteins and apoptosis. The results showed that LPS induced microglial expression of NLRP3/Caspase-1/IL-1β signaling pathway protein Iba1, and the inflammatory protein and inflammatory factors IL-1β, IL-6 and TNF-α, the expression of Bax increased significantly, Bcl2 expression decreased, and the learning and memory abilities of mice decreased significantly. Preconditioning with the Hsp22-overexpressing lentivirus attenuated LPS-induced activation of hippocampal microglia, the expression of inflammatory factors and pathway proteins, and apoptosis, and improved cognitive impairment in mice. In addition, plasmid-mediated Hsp22 overexpression reversed LPS-induced inflammation. These findings suggest that Hsp22 overexpression is a promising method for the treatment of cognitive impairment.

Heat Shock Protein 22 in Physiological and Pathological Hearts: Small Molecule, Large Potentials

Small heat shock protein 22 (HSP22) belongs to the superfamily of heat shock proteins and is predominantly expressed in the heart, brain, skeletal muscle, and different types of cancers. It has been found that HSP22 is involved in variant cellular functions in cardiomyocytes and plays a vital role in cardiac protection against cardiomyocyte injury under diverse stress. This review summarizes the multiple functions of HSP22 in the heart and the underlying molecular mechanisms through modulating gene transcription, post-translational modification, subcellular translocation of its interacting proteins, and protein degradation, facilitating mitochondrial function, cardiac metabolism, autophagy, and ROS production and antiapoptotic effect. We also discuss the association of HSP22 in cardiac pathologies, including human dilated cardiomyopathy, pressure overload-induced heart failure, ischemic heart diseases, and aging-related cardiac metabolism disorder. The collected information would provide insights into the understanding of the HSP22 in heart diseases and lead to discovering the therapeutic targets.

Quaternary Structure and Hetero-Oligomerization of Recombinant Human Small Heat Shock Protein HspB7 (cvHsp)

In this study, a reliable and simple method of untagged recombinant human HspB7 preparation was developed. Recombinant HspB7 is presented in two oligomeric forms with an apparent molecular weight of 36 kDa (probably dimers) and oligomers with an apparent molecular weight of more than 600 kDa. By using hydrophobic and size-exclusion chromatography, we succeeded in preparation of HspB7 dimers. Mild oxidation promoted the formation of large oligomers, whereas the modification of Cys 126 by iodoacetamide prevented it. The deletion of the first 13 residues or deletion of the polySer motif (residues 17–29) also prevented the formation of large oligomers of HspB7. Cys-mutants of HspB6 and HspB8 containing a single-Cys residue in the central part of the β7 strand in a position homologous to that of Cys137 in HspB1 can be crosslinked to the wild-type HspB7 through a disulfide bond. Immobilized on monoclonal antibodies, the wild-type HspB6 interacted with the wild-type HspB7. We suppose that formation of heterodimers of HspB7 with HspB6 and HspB8 may be important for the functional activity of these small heat shock proteins.

The influence of hypoxia on the cardiac transcriptomes of two estuarine species - C. variegatus and F. grandis

Increased nutrient loading has led to eutrophication of coastal shelf waters which has resulted in increased prevalence of persistent hypoxic zones - areas in which the dissolved oxygen content of the water drops below 2 mg/L. The northern Gulf of Mexico, fed primarily by the Mississippi River watershed, undergoes annual establishment of one of the largest hypoxic zones in the world. Exposure to hypoxia can induce physiological impacts in fish cardiac systems that include bradycardia, changes in stroke volume, and altered cardiovascular vessel development. While these impacts have been addressed at the functional level, there is little information regarding the molecular basis for these changes. This study used transcriptomic analysis techniques to interrogate the effects of hypoxia exposure on the developing cardiovascular system in newly hatched larvae of two estuarine species that occupy the same ecological niche - the sheepshead minnow (Cyprinodon variegatus) and the Gulf killifish (Fundulus grandis). Results suggest that while differential gene expression is largely distinct between the two species, downstream impacts on pathways and functional responses such as reduced cardiac hypertrophy, modulation of blood pressure, and increased incidence of apoptosis appear to be conserved. Further, differences in the magnitude of these conserved responses may suggest that the length of embryonic development could impart a level of resiliency to hypoxic perturbation in early life stage fish.

Reactive oxygen species: the root cause of nanoparticle-induced toxicity in Drosophila melanogaster

Nanotechnology is a rapidly developing technology in the twenty-first century. Nanomaterials are extensively used in numerous industries including cosmetics, food, medicines, industries, agriculture, etc. Along with its wide application toxicity is also reported from studies of various model organisms including Drosophila. The toxicity reflects cytotoxicity, genotoxicity, and teratogenicity. The current study correlates the toxicity as a consequence of reactive oxygen species (ROS) generated owing to the presence of nanoparticles with the living cell. ROS mainly includes hydroxyl ions, peroxide ions, superoxide anions, singlet oxygen, and hypochlorous acids. An elevated level of ROS can damage the cells by various means. To protect the body from excess ROS, living cells possess a set of antioxidant enzymes which includes peroxidase, glutathione peroxidase, and catalase. If the antioxidant enzymes cannot nullify the elevated ROS level than DNA damage, cell damage, cytotoxicity, apoptosis, and uncontrolled cell regulations occur resulting in abnormal physiological and genotoxic conditions. Herewith, we are reporting various morphological and physiological defects caused after nanoparticle treatment as a function of redox imbalance.

The Archaeal Small Heat Shock Protein Hsp17.6 Protects Proteins from Oxidative Inactivation

Small heat shock proteins (sHsps) are widely distributed among various types of organisms and function in preventing the irreversible aggregation of thermal denaturing proteins. Here, we report that Hsp17.6 from Methanolobus psychrophilus exhibited protection of proteins from oxidation inactivation. The overexpression of Hsp17.6 in Escherichia coli markedly increased the stationary phase cell density and survivability in HClO and H₂O₂. Treatments with 0.2 mM HClO or 10 mM H₂O₂ reduced malate dehydrogenase (MDH) activity to 57% and 77%, whereas the addition of Hsp17.6 recovered the activity to 70-90% and 86-100%, respectively. A similar effect for superoxide dismutase oxidation was determined for Hsp17.6. Non-reducing sodium dodecyl sulfate polyacrylamide gel electrophoresis assays determined that the Hsp17.6 addition decreased H₂O₂-caused disulfide-linking protein contents and HClO-induced degradation of MDH; meanwhile, Hsp17.6 protein appeared to be oxidized with increased molecular weights. Mass spectrometry identified oxygen atoms introduced into the larger Hsp17.6 molecules, mainly at the aspartate and methionine residues. Substitution of some aspartate residues reduced Hsp17.6 in alleviating H₂O₂- and HClO-caused MDH inactivation and in enhancing the E. coli survivability in H₂O₂ and HClO, suggesting that the archaeal Hsp17.6 oxidation protection might depend on an "oxidant sink" effect, i.e., to consume the oxidants in environments via aspartate oxidation.

Heat Shock Protein 22 Attenuates Doxorubicin-Induced Cardiotoxicity via Regulating Inflammation and Apoptosis

Background

The antitumor effect of doxorubicin (DOX) is limited by its acute and chronic toxicity to the heart, which causes heart injury. Heat shock protein 22 (Hsp22) is a protein proved to exert anti-apoptosis and anti-inflammatory effects in other diseases and physical conditions. In this study, we aim to explore whether Hsp22 could exert a protective role during cardiac injury in response to DOX.

Methods

The overexpression of Hsp22 was mediated via adenovirus vector to clarify the role of Hsp22 in the cardiac injury caused by DOX. DOX-induced acute heart injury mouse model was established by single intraperitoneal injection of DOX (15 mg/kg). Subsequently, cardiac staining and molecular biological analysis were performed to analyze the morphological and biochemical effects of Hsp22 on cardiac injury. H9c2 cells were used for validation in vitro.

Results

An increase in the expression level of Hsp22 was observed in DOX-treated heart tissue. Furthermore, cardiac-specific overexpression of Hsp22 showed reduced cardiac dysfunction, decrease in inflammatory response, and reduction in cell apoptosis in injury heart and cardiomyocytes induced by DOX in vivo and in vitro. Moreover, the suppression of Toll-like receptor (TLR)4/NOD-, LRR-, and pyrin domain-containing protein 3 (NLRP3) was associated with the protective effect of Hsp22. Finally, the protective effect of Hsp22 cardiac function was almost abolished by overexpression of NLRP3 in DOX-treated mice.

Conclusion

In summary, Hsp22 overexpression in the heart could suppress cardiac injury in response to DOX treatment through blocking TLR4/NLRP3 activation. Hsp22 may become a new therapeutic method for treating cardiac injury induced by DOX in cancer patients.

Molecular characterization and function analysis of Epinephelus coioides Hsp22 response to SGIV and Vribro alginolyticus infection

Heat shock protein 22 (Hsp22) is an important regulatory factor response to various stresses in mammals. In this study, the full length cDNA of Epinephelus coioides Hsp22, which was 1680bp in length, with a 289 bp 5' UTR, a 725 bp 3'UTR, and a 666 bp open reading frame encoding 221 amino acids, was obtained. E. coioides Hsp22 contains a highly conserved α-crystallin domain. E. coioides Hsp22 mRNA was detected in all tissues examined by quantitative real-time PCR, with the highest expression in blood, followed by the spleen, skin, gill, head kidney, muscle, heart, liver, trunk kidney, stomach, pyloric caeca, intestine, brain and thymus. The expression patterns of E. coioides Hsp22 response to infection with Singapore grouper iridovirus (SGIV) and Vribro alginolyticus, the important pathogens of E. coioides, were studied. The expression levels of the gene were up-regulated in the tissues examined. Subcellular localization analysis demonstrated that E. coioides Hsp22 was distributed in both the cytoplasm and nucleus. In addition, E. coioides Hsp22 significantly inhibited the SGIV-induced cell apoptosis. In summary, the E. coioides Hsp22 might play a critical role in pathogenic stimulation.

L-3-n-Butylphthalide Protects HSPB8 K141N Mutation-Induced Oxidative Stress by Modulating the Mitochondrial Apoptotic and Nrf2 Pathways

Charcot-Marie-Tooth disease (CMT), also known as hereditary motor and sensory neuropathy, is the most common inherited peripheral nerve disorder. Missense mutations, such as K141N, in the small heat shock protein HSPB8 are known to cause distal hereditary motor neuropathy 2A (dHMN2A) or Charcot-Marie-Tooth neuropathy type 2L (CMT2L). However, of critical clinical significance, very few specific therapies for this disease exist. In the present study, we investigated the impact of mutant K141N HSPB8 on mitochondrial distribution and function in a cellular model of CMT2L. Our results indicate that K141N HSPB8 induced mitochondrial aggregation and caused increased oxidative stress injury. As an extraction from Chinese celery Apium graveolens Linn seeds, L-3-n-Butylphthalide (NBP), has been reported to exert many neuroprotective effects, we interrogated whether NBP could elicit a protective effect on the cell injury typically caused by HSPB8 K141N mutations. We found NBP could reverse the pathological processes induced by HSPB8 K141N mutation via an antioxidant effect, modulation of the Bax/Bcl-2 mitochondrial apoptotic and Nrf2 pathways. We propose a novel function of HSPB8, highlighting the consequence of the K141N pathogenic mutation. Furthermore, we suggest NBP may have promising therapeutic potential in the treatment of CMT2L.

The functional roles of the unstructured N- and C-terminal regions in αB-crystallin and other mammalian small heat-shock proteins

Small heat-shock proteins (sHsps), such as αB-crystallin, are one of the major classes of molecular chaperone proteins. In vivo, under conditions of cellular stress, sHsps are the principal defence proteins that prevent large-scale protein aggregation. Progress in determining the structure of sHsps has been significant recently, particularly in relation to the conserved, central and β-sheet structured α-crystallin domain (ACD). However, an understanding of the structure and functional roles of the N- and C-terminal flanking regions has proved elusive mainly because of their unstructured and dynamic nature. In this paper, we propose functional roles for both flanking regions, based around three properties: (i) they act in a localised crowding manner to regulate interactions with target proteins during chaperone action, (ii) they protect the ACD from deleterious amyloid fibril formation and (iii) the flexibility of these regions, particularly at the extreme C-terminus in mammalian sHsps, provides solubility for sHsps under chaperone and non-chaperone conditions. In the eye lens, these properties are highly relevant as the crystallin proteins, in particular the two sHsps αA- and αB-crystallin, are present at very high concentrations.

Chaperonopathies: Spotlight on Hereditary Motor Neuropathies

Distal hereditary motor neuropathies (dHMN) are a group of rare hereditary neuromuscular disorders characterized by an atrophy that affects peroneal muscles in the absence of sensory symptoms. To date, 23 genes are thought to be responsible for dHMN, four of which encode chaperones: DNAJB2, which encodes a member of the HSP40/DNAJ co-chaperone family; and HSPB1, HSPB3, and HSPB8, encoding three members of the small heat shock protein family. While around 30 different mutations in HSPB1 have been identified, the remaining three genes are altered in many fewer cases. Indeed, a mutation of HSPB3 has only been described in one case, whereas a few cases have been reported carrying mutations in DNAJB2 and HSPB8, most of them caused by a founder c.352+1G>A mutation in DNAJB2 and by mutations affecting the K141 residue in the HSPB8 chaperone. Hence, their rare occurrence makes it difficult to understand the pathological mechanisms driven by such mutations in this neuropathy. Chaperones can assemble into multi-chaperone complexes that form an integrated chaperone network within the cell. Such complexes fulfill relevant roles in a variety of processes, such as the correct folding of newly synthesized proteins, in which chaperones escort them to precise cellular locations, and as a response to protein misfolding, which includes the degradation of proteins that fail to refold properly. Despite this range of functions, mutations in some of these chaperones lead to diseases with a similar clinical profile, suggesting common pathways. This review provides an overview of the genetics of those dHMNs that share a common disease mechanism and that are caused by mutations in four genes encoding chaperones: DNAJB2, HSPB1, HSPB3, and HSPB8.

H11/HSPB8 Restricts HIV-2 Vpx to Restore the Anti-Viral Activity of SAMHD1

Virus-host interactions play vital roles in viral replication and virus-induced pathogenesis. Viruses rely entirely upon host cells to reproduce progeny viruses; however, host factors positively or negatively regulate virus replication by interacting with viral proteins. The elucidation of virus-host protein interaction not only provides a better understanding of the molecular mechanisms by which host cells combat viral infections, but also facilitates the development of new anti-viral therapeutics. Identification of relevant host factors requires techniques that enable comprehensive characterization of virus-host protein interactions. In this study, we developed a proteomic approach to systematically identify human protein kinases that interact potently with viral proteins. For this purpose, we synthesized 412 full-length human protein kinases using the wheat germ cell-free protein synthesis system, and screened them for their association with a virus protein using the amplified luminescent proximity homogenous assay (AlphaScreen). Using this system, we attempted to discover a robust anti-viral host restriction mechanism targeting virus protein X (Vpx) of HIV-2. The screen identified H11/HSPB8 as a Vpx-binding protein that negatively regulates the stability and function of Vpx. Indeed, overexpression of H11/HSPB8 promoted the degradation of Vpx via the ubiquitin-proteasome pathway and inhibited its interaction with SAMHD1, a host restriction factor responsible for blocking replication of HIV. Conversely, targeted knockdown of H11/HSPB8 in human trophoblast cells, which ordinarily express high levels of this protein, restored the expression and function of Vpx, making the cells highly susceptible to viral replication. These results demonstrate that our proteomic approach represents a powerful tool for revealing virus-host interaction not yet identified by conventional methods. Furthermore, we showed that H11/HSPB8 could be a potential host regulatory factor that may prevent placental infection of HIV-2 during pregnancy.

Heat shock proteins: a therapeutic target worth to consider

Heat shock proteins (HSPs) are the molecular chaperones, that are not only expressed during the normal growth process of cell cycle consecutively, but also get induced in cells during various stress conditions produced by cellular insult, environmental changes, temperature, infections, tumors etc. According to their molecular weight and functions, HSPs are divided into five major families. HSP90, HSP70, HSP60 and HSP100 are the most studied members of the family. Experimental studies have proved that overexpression and/or inhibition of HSPs play an important role in maintaining the tolerance and cell viability under above-described stress conditions. HSP90 is found to be a promising the candidate for the diagnosis, prognosis and treatment of cancer. Similarly, HSP70, HSP60 and small HSPs experimentally and clinically have potential for the treatment of neurodegenerative disease, ischemia, cell death, autoimmunity, graft rejection, etc. In a way, exploring, the cytoprotective and immunoregulatory role of HSPs can open a new avenue for the drug discovery and treatment of critical diseases.

α-Casein inhibition mechanism in concanavalin A aggregation process

The inhibition of the aggregation in protein solutions is currently a subject of great interest in many research fields, from the study of protein-misfolding related diseases to pharmaceutics, biotechnology, and food science. α(s1)-Casein, one of the four types of caseins, which are the largest protein component of bovine milk, has been found to hinder the aggregation process of several proteins, including the amyloid β-peptide, involved in Alzheimer's disease. To shed light into the mechanisms by which casein exerts this chaperon-like protective action, we studied its effect on the different steps of the aggregation process of concanavalin A, by means of both static and dynamic light scattering, thioflavin T and ANS fluorescence, circular dichroism, and atomic force microscopy. Our results show that casein has a poor effect on the first step of the process leading to the formation of amyloid-like structures. On the contrary, it has a marked effect on the second step of the process, ascribable to clusters condensation and compaction, up to the formation of very large aggregates. Such an effect requires a molar ratio of casein larger than that necessary to inhibit the fibrillogenesis of the amyloid β-peptide, thus, suggesting a different mechanism of interaction of casein, depending on both conformational properties and relative size of the aggregating molecules.

Cellular internalization and stress response of ingested amorphous silica nanoparticles in the midgut of Drosophila melanogaster

BACKGROUND

Amorphous silica nanoparticles (aSNPs) are used for various applications including food industry. However, limited in vivo studies are available on absorption/internalization of ingested aSNPs in the midgut cells of an organism. The study aims to examine cellular uptake of aSNPs (<30nm) in the midgut of Drosophila melanogaster (Oregon R(+)) owing to similarities between the midgut tissue of this organism and human and subsequently cellular stress response generated by these nanoparticles.

METHODS

Third instar larvae of D. melanogaster were exposed orally to 1-100μg/mL of aSNPs for 12-36h and oxidative stress (OS), heat shock genes (hsgs), membrane destabilization (Acridine orange/Ethidium Bromide staining), cellular internalization (TEM) and apoptosis endpoints.

RESULTS

A significant increase was observed in OS endpoints in the midgut cells of exposed Drosophila in a concentration- and time-dependent manner. Significantly increased expression of hsp70 and hsp22 along with caspases activation, membrane destabilization and mitochondrial membrane potential loss was also observed. TEM analysis showed aSNPs-uptake in the midgut cells of exposed Drosophila via endocytic vesicles and by direct membrane penetration.

CONCLUSION

aSNPs after their internalization in the midgut cells of exposed Drosophila larvae show membrane destabilization along with increased cellular stress and cell death.

GENERAL SIGNIFICANCE

Ingested aSNPs show adverse effects on the cells of GI tract of the exposed organism thus their industrial use as a food-additive may raise concern to human health.

Early membrane initiated transcriptional effects of estrogens in breast cancer cells: First pharmacological evidence for a novel membrane estrogen receptor element (ERx)

The complexity of estrogen actions mainly relies to the presence of different identified receptors (ERα, ERβ, their isoforms, and GPR30/GPER) and their discrete cellular distribution. Depending on the localization of the receptor that mediates estrogen effects, nuclear and extra-nuclear actions have been described. The latter can trigger a number of signaling events leading also to transcriptional modifications. In an attempt to clarify the nature of the receptor(s) involved in the membrane initiated effect of estrogens on gene expression, we performed a whole transcriptome analysis of breast cancer cell lines with different receptor profiles (T47D, MCF7, MDA-MB-231, SK-BR-3). A pharmacological approach was conducted with the use of estradiol (E(2)) or membrane-impermeable E(2)-BSA in the absence or presence of a specific ERα-β or GPR30/GPER antagonist. Our results clearly show that in addition to the ERα isoforms and/or GPR30/GPER that mainly mediate the transcriptional effect of E(2)-BSA, there is a specific transcriptional signature (found in T47D and MCF-7 cells) suggesting the presence of an unidentified membrane ER element (ERx). Analysis of its signature and phenotypic verification revealed that important cell function such as apoptosis, transcriptional regulation, and growth factor signaling are associated with ERx.

Molecular basis of axonal dysfunction and traffic impairments in CMT

Charcot-Marie-Tooth disease (CMT) is one of the most common inherited neurological disorders. It comprises a group of diseases caused by mutations in genes involved in Schwann cells homeostasis and neuronal function that affect the peripheral nerves. So far mutations in more than 33 genes have been identified causing either the demyelinating form (CMT1) or the axonal form (CMT2). Genes involving a large variety of unrelated functions may lead to the same phenotype when mutated. Our review will focus on the common link between genes causing axonal phenotypes like MFN2, KIF1B, DYNC1H1, Rab7, TRPV4, ARSs, NEFL, HSPB1, MPZ, and HSPB8. While KIF1B and DYNC1H1, two genes coding for molecular motors, are directly linked to axonal transport, the involvement of the other CMT2-causing genes in this function is less obvious. However, the last years have seen a growing list of evidence demonstrating that intracellular trafficking and mitochondrial dynamics might be dysfunctional in CMT2, and these mechanisms might present a common link between dissimilar CMT2-causing genes. The involvement of impaired transport in the pathogenesis of other rare neurological diseases or recessive CMT2 is also discussed.

Small heat shock proteins HSP27 (HspB1), αB-crystallin (HspB5) and HSP22 (HspB8) as regulators of cell death

Hsp27, αB-crystallin and HSP22 are ubiquitous small heat shock proteins (sHsp) whose expression is induced in response to a wide variety of unfavorable physiological and environmental conditions. These sHsp protect cells from otherwise lethal conditions mainly by their involvement in cell death pathways such as necrosis, apoptosis or autophagy. At a molecular level, the mechanisms accounting for sHsp functions in cell death are (1) prevention of denatured proteins aggregation, (2) regulation of caspase activity, (3) regulation of the intracellular redox state, (4) function in actin polymerization and cytoskeleton integrity and (5) proteasome-mediated degradation of selected proteins. In cancer cells, these sHsp are often overexpressed and associated with increased tumorigenicity, cancer cells metastatic potential and resistance to chemotherapy. Altogether, these properties suggest that Hsp27, αB-crystallin and Hsp22 are appropriate targets for modulating cell death pathways. In the present, we briefly review recent reports showing molecular evidence of cell death regulation by these sHsp and co-chaperones. This article is part of a Directed Issue entitled: Small HSPs in physiology and pathology.

Developmental expression pattern of Hspb8 mRNA in the mouse brain: analysis through online databases

Hspb8 is a member of the Hspb family of chaperone-like proteins. It is involved in several neural disorders such as Alzheimer's disease, amyotrophic lateral sclerosis, hereditary distal motor neuropathy, and Charcot-Marie-Tooth's disease. In this work, we aimed to characterize its expression pattern in the mouse brain, by using the information available at online databases of high-throughput in situ hybridization. Therefore, we downloaded and analyzed the image series from these databases showing Hspb8 mRNA expression from embryonic to adult and aging stages. In early gestational embryos, Hspb8 was expressed in the hippocampal anlagen and in the ventricular layer of rhombomere 4. At perinatal stages, there appeared transitory expression in the dentate gyrus and the cerebellar cortex. From perinatal to aging stages, the neurons of the mesencephalic trigeminal nucleus and cranial motor nuclei displayed stable and strong Hspb8 expression. Additionally, along these stages there was moderate and relatively homogenous expression in the anterodorsal thalamic, lateral mammillary, arcuate hypothalamic and medial habenular nuclei, and in the locus coeruleus. In its turn, the basal ganglia, cerebellar inner granular layer and diverse sensory and reticular formation nuclei of the hindbrain contained scattered cells with strong expression. In conclusion, Hspb8 mRNA is constitutively expressed in specific brain structures across ontogeny, so that eventually they could be affected by the malfunction or deregulation of this molecule.

Large potentials of small heat shock proteins

Modern classification of the family of human small heat shock proteins (the so-called HSPB) is presented, and the structure and properties of three members of this family are analyzed in detail. Ubiquitously expressed HSPB1 (HSP27) is involved in the control of protein folding and, when mutated, plays a significant role in the development of certain neurodegenerative disorders. HSPB1 directly or indirectly participates in the regulation of apoptosis, protects the cell against oxidative stress, and is involved in the regulation of the cytoskeleton. HSPB6 (HSP20) also possesses chaperone-like activity, is involved in regulation of smooth muscle contraction, has pronounced cardioprotective activity, and seems to participate in insulin-dependent regulation of muscle metabolism. HSPB8 (HSP22) prevents accumulation of aggregated proteins in the cell and participates in the regulation of proteolysis of unfolded proteins. HSPB8 also seems to be directly or indirectly involved in regulation of apoptosis and carcinogenesis, contributes to cardiac cell hypertrophy and survival and, when mutated, might be involved in development of neurodegenerative diseases. All small heat shock proteins play important "housekeeping" roles and regulate many vital processes; therefore, they are considered as attractive therapeutic targets.

The Gln32Lys polymorphism in HSP22 of Zhikong scallop Chlamys farreri is associated with heat tolerance

Background

Heat shock protein 22 is a member of small heat shock proteins with molecular chaperone activity. Though their multiple functions have been well characterized, there is no report about the association between the polymorphisms of HSP22 and heat tolerance.

Methodology

Three single nucleotide polymorphisms were identified in HSP22 from scallop Chlamys farreri (CfHSP22), and the +94 C-A locus was found to be nonsynonymous. Three genotypes at locus +94, A/A, A/C and C/C, were revealed by using Bi-PASA PCR analysis, and their frequencies were 19.5%, 27.6% and 52.9% in the heat resistant stock, while 9.3%, 17.4% and 73.3% in the heat susceptible stock, respectively. The frequency differences of the three genotypes were significant (P<0.05) between the two stocks. After incubating at 30°C for 84 h, the cumulative mortality of scallops with +94 C/C genotype and +94 A/C genotypes was 95% and 90%, respectively, which was significantly higher (P<0.01) than that of scallops with +94 A/A genotype (70%). The molecular chaperone activity of two His-tagged fusion proteins, rCfHSP22Q with +94 C/C genotype and rCfHSP22K with +94 A/A genotype were analyzed by testing the ability of protecting citrate synthase (CS) against thermal inactivation in vitro. After incubated with rCfHSP22Q or rCfHSP22K at 38°C for 1 h, the activity of CS lost 50% and 45%, and then recovered to 89% and 95% of the original activity following 1 h restoration at 22°C, respectively, indicating that the mutation from Gln to Lys at this site might have an impact on molecular chaperone activities of CfHSP22.

Conclusions

These results implied that the polymorphism at locus +94 of CfHSP22 was associated with heat tolerance of scallop, and the +94 A/A genotype could be a potential marker available in future selection of Zhikong scallop with heat tolerance.

Hsp22 (HspB8/H11) knockdown induces Sam68 expression and stimulates proliferation of glioblastoma cells

Sam68 (Src-associated protein in mitosis 68 kDa) is a multifunctional protein, known to govern cellular signal transduction, transcription, RNA metabolism, proliferation, apoptosis, and HIV-1 replication. Although intrinsic mechanisms that modulate Sam68 function are beginning to emerge, the regulatory events contributing to its expression remain elusive. We previously reported that heat shock protein-22 (Hsp22) antagonizes Sam68 function in rev-response element (RRE)-mediated gene expression. We now demonstrate that Sam68 levels correlate inversely with Hsp22 in a variety of cells, including U87, Jurkat, 293T, and U-937. In U87 glioblastoma cells, which contained high levels of Hsp22 than other cell lines tested, Hsp22 knockdown dramatically increased both Sam68 mRNA and protein, altered cellular morphology, and enhanced cell proliferation. This heightened proliferation was associated with a sharp decrease in G(0) /G(1) and a corresponding increase in S and G(2) /M phases in exponentially growing cultures. The increased S phase population in turn correlated with enhanced expression of cell cycle regulatory proteins such as cyclin E, cyclin A, ribonucleotide reductase (RNR), and proliferating cell nuclear antigen (PCNA), which are required for the transition of cells from G(1) to S phase. Collectively, our results demonstrate for the first time that Hsp22 regulates Sam68 expression and the ratio of Sam68 to Hsp22 may determine the proliferative potential of glioblastoma cells.

HSPB8 is methylated in hematopoietic malignancies and overexpression of HSPB8 exhibits antileukemia effect

HSPB8 has been shown to be involved in regulation of cell proliferation and apoptosis, and it has also been found to have divergent properties in solid tumors. The purpose of this study was to investigate the expression and function of HSPB8 in hematopoietic malignancies. Expression and induced expression of HSPB8 was evaluated in hematopoietic tumor cell lines and bone marrow samples from patients with leukemia. Methylation status was investigated by methylation-specific polymerase chain reaction. The role of HSPB8 in hematopoietic malignancies was addressed by reintroducing HSPB8 expression into the K562 (leukemia) and Namalwa (lymphoma) cell lines. Expression of HSPB8 was absent in hematopoietic tumor cell lines and primary patient and normal volunteer samples. Promoter DNA methylation of HSPB8 was observed in these cells. HSPB8 expression could be restored after demethylation treatment with 5-aza-2'-deoxycytidine. Overexpression of HSPB8 reduced colony formation of both K562 and Namalwa cell lines, inhibited the cell growth of Namalwa in vitro, and suppressed tumor formation of K562 cells in vivo. The present study demonstrates that HSPB8 is silenced by DNA methylation in hematopoietic malignant and normal cells and its expression can be induced by treatment with 5-aza-2'-deoxycytidine. Overexpression of HSPB8 may have an antitumor activity in chronic myelogenous leukemia and lymphoma.

Truncation attenuates molecular chaperoning and apoptosis inhibition by p26, a small heat shock protein from Artemia franciscana

The small heat shock proteins (sHSPs), which prevent irreversible protein denaturation and inhibit apoptosis, consist of an amino-terminus, the canonical α-crystallin domain, and a carboxy-terminal extension. It remains difficult, however, to define sHSP structure-function relationships and with this in mind p26, an sHSP from the crustacean Artemia franciscana, was truncated by deletion mutagenesis. Wild-type p26 cDNA and three truncated variants inserted into the eukaryotic expression vector pcDNA3.1/HisC were used to generate stably transfected 293H cells. p26 shielded transfected cells against death upon exposure to heat and oxidative stress. Truncation reduced chaperone activity, with cells synthesizing the p26 α-crystallin domain being the least resistant. Wild-type p26 inhibited apoptosis in transfected cells, with protection against oxidation-generated apoptosis being more effective than that against heat-induced apoptosis. Truncation reduced p26 apoptotic inhibitory activity, with the α-crystallin domain again being the least effective. The results show that a crustacean sHSP functions effectively in mammalian cells, demonstrating interchangeability of these proteins between distantly related organisms and indicating similarities in their mechanisms of action. Moreover, maximal activity was observed for full-length p26, indicating that structural elements required for chaperone activity and apoptosis inhibition reside throughout the protein.

Heat shock proteins and Drosophila aging

Since their discovery in Drosophila, the heat shock proteins (Hsps) have been shown to regulate both stress resistance and life-span. Aging is characterized by increased oxidative stress and the accumulation of abnormal (malfolded) proteins, and these stresses induce Hsp gene expression through the transcription factor HSF. In addition, a subset of Hsps is induced by oxidative stress through the JNK signaling pathway and the transcription factor Foxo. The Hsps counteract the toxicity of abnormal proteins by facilitating protein refolding and turnover, and through other mechanisms including inhibition of apoptosis. The Hsps are up-regulated in tissue-specific patterns during aging, and their expression correlates with, and sometimes predicts, life span, making them ideal biomarkers of aging. The tools available for experimentally manipulating gene function and assaying healthspan in Drosophila provides an unparalleled opportunity to further study the role of Hsps in aging.

Proproliferative functions of Drosophila small mitochondrial heat shock protein 22 in human cells

Aging is a complex process accompanied by a decreased capacity of cells to cope with random damages induced by reactive oxygen species, the natural by-products of energy metabolism, leading to protein aggregation in various components of the cell. Chaperones are important players in the aging process as they prevent protein misfolding and aggregation. Small chaperones, such as small heat shock proteins, are involved in the refolding and/or disposal of protein aggregates, a feature of many age-associated diseases. In Drosophila melanogaster, mitochondrial Hsp22 (DmHsp22), is localized in the mitochondrial matrix and is preferentially up-regulated during aging. Its overexpression results in an extension of life span (>30%) (Morrow, G., Samson, M., Michaud, S., and Tanguay, R. M. (2004) FASEB J. 18, 598-599 and Morrow, G., Battistini, S., Zhang, P., and Tanguay, R. M. (2004) J. Biol. Chem. 279, 43382-43385). Long lived flies expressing Hsp22 also have an increased resistance to oxidative stress and maintain locomotor activity longer. In the present study, the cross-species effects of Hsp22 expression were tested. DmHsp22 was found to be functionally active in human cells. It extended the life span of normal fibroblasts, slowing the aging process as evidenced by a lower level of the senescence associated beta-galactosidase. DmHsp22 expression in human cancer cells increased their malignant properties including anchorage-independent growth, tumor formation in nude mice, and resistance to a variety of anticancer drugs. We report that the DmHsp22 interacts and inactivates wild type tumor suppressor protein p53, which may be one possible way of its functioning in human cells.

The taming of small heat-shock proteins: crystallization of the alpha-crystallin domain from human Hsp27

Small heat-shock proteins (sHsps) are ubiquitous molecular chaperones. sHsps function as homooligomers or heterooligomers that are prone to subunit exchange and structural plasticity. Here, a procedure for obtaining diffraction-quality crystals of the alpha-crystallin domain of human Hsp27 is presented. Initially, limited proteolysis was used to delineate the corresponding stable fragment (residues 90-171). This fragment could be crystallized, but examination of the crystals using X-rays indicated partial disorder. The surface-entropy reduction approach was applied to ameliorate the crystal quality. Consequently, a double mutant E125A/E126A of the 90-171 fragment yielded well ordered crystals that diffracted to 2.0 A resolution.

Gene expression and muscle fiber function in a porcine ICU model

Skeletal muscle wasting and impaired muscle function in response to mechanical ventilation and immobilization in intensive care unit (ICU) patients are clinically challenging partly due to 1) the poorly understood intricate cellular and molecular networks and 2) the unavailability of an animal model mimicking this condition. By employing a unique porcine model mimicking the conditions in the ICU with long-term mechanical ventilation and immobilization, we have analyzed the expression profile of skeletal muscle biopsies taken at three time points during a 5-day period. Among the differentially regulated transcripts, extracellular matrix, energy metabolism, sarcomeric and LIM protein mRNA levels were downregulated, while ubiquitin proteasome system, cathepsins, oxidative stress responsive genes and heat shock proteins (HSP) mRNAs were upregulated. Despite 5 days of immobilization and mechanical ventilation single muscle fiber cross-sectional areas as well as the maximum force generating capacity at the single muscle fiber level were preserved. It is proposed that HSP induction in skeletal muscle is an inherent, primary, but temporary protective mechanism against protein degradation. To our knowledge, this is the first study that isolates the effect of immobilization and mechanical ventilation in an ICU condition from various other cofactors.

Proteome of synaptosome-associated proteins in spinal cord dorsal horn after peripheral nerve injury

Peripheral nerve injury may lead to neuroadaptive changes of cellular signals in spinal cord that are thought to contribute to central mechanisms underlying neuropathic pain. Here we used a 2-DE-based proteomic technique to determine the global expression changes of synaptosome-associated proteins in spinal cord dorsal horn after unilateral fifth spinal nerve injury (SNI). The fifth lumbar dorsal horns ipsilateral to SNI or sham surgery were harvested on day 14 post-surgery, and the total soluble and synaptosomal fractions were isolated. The proteins derived from the synaptosomal fraction were resolved by 2-DE. We identified 27 proteins that displayed different expression levels after SNI, including proteins involved in transmission and modulation of noxious information, cellular metabolism, membrane receptor trafficking, oxidative stress, apoptosis, and degeneration. Six of the 27 proteins were chosen randomly and further validated in the synaptosomal fraction by Western blot analysis. Unexpectedly, Western blot analysis showed that only one protein in the total soluble fraction exhibited a significant expression change after SNI. The data indicate that peripheral nerve injury changes not only protein expression but also protein subcellular distribution in dorsal horn cells. These changes might participate in the central mechanism that underlies the maintenance of neuropathic pain.

Nuclear and extranuclear pathway inputs in the regulation of global gene expression by estrogen receptors

Whereas estrogens exert their effects by binding to nuclear estrogen receptors (ERs) and directly altering target gene transcription, they can also initiate extranuclear signaling through activation of kinase cascades. We have investigated the impact of estrogen-mediated extranuclear-initiated pathways on global gene expression by using estrogen-dendrimer conjugates (EDCs), which because of their charge and size remain outside the nucleus and can only initiate extranuclear signaling. Genome-wide cDNA microarray analysis of MCF-7 breast cancer cells identified a subset of 17beta-estradiol (E2)-regulated genes ( approximately 25%) as EDC responsive. The EDC and E2-elicited increases in gene expression were due to increases in gene transcription, as observed in nuclear run-on assays and RNA polymerase II recruitment and phosphorylation. Treatment with antiestrogen or ERalpha knockdown using small interfering RNA abolished EDC-mediated gene stimulation, whereas GPR30 knockdown or treatment with a GPR30-selective ligand was without effect, indicating ER as the mediator of these gene regulations. Inhibitors of MAPK kinase and c-Src suppressed both E2 and EDC stimulated gene expression. Of note, in chromatin immunoprecipitation assays, EDC was unable to recruit ERalpha to estrogen-responsive regions of regulated genes, whereas ERalpha recruitment by E2 was very effective. These findings suggest that other transcription factors or kinases that are downstream effectors of EDC-initiated extranuclear signaling cascades are recruited to regulatory regions of EDC-responsive genes in order to elicit gene stimulation. This study thus highlights the importance of inputs from both nuclear and extranuclear ER signaling pathways in regulating patterns of gene expression in breast cancer cells.