Small heat shock proteins and the cytoskeleton: an essential interplay for cell integrity?

KRIT1 loss-of-function induces a chronic Nrf2-mediated adaptive homeostasis that sensitizes cells to oxidative stress: Implication for Cerebral Cavernous Malformation disease

KRIT1 (CCM1) is a disease gene responsible for Cerebral Cavernous Malformations (CCM), a major cerebrovascular disease of proven genetic origin affecting 0.3-0.5% of the population. Previously, we demonstrated that KRIT1 loss-of-function is associated with altered redox homeostasis and abnormal activation of the redox-sensitive transcription factor c-Jun, which collectively result in pro-oxidative, pro-inflammatory and pro-angiogenic effects, suggesting a novel pathogenic mechanism for CCM disease and raising the possibility that KRIT1 loss-of-function exerts pleiotropic effects on multiple redox-sensitive mechanisms. To address this possibility, we investigated major redox-sensitive pathways and enzymatic systems that play critical roles in fundamental cytoprotective mechanisms of adaptive responses to oxidative stress, including the master Nrf2 antioxidant defense pathway and its downstream target Glyoxalase 1 (Glo1), a pivotal stress-responsive defense enzyme involved in cellular protection against glycative and oxidative stress through the metabolism of methylglyoxal (MG). This is a potent post-translational protein modifier that may either contribute to increased oxidative molecular damage and cellular susceptibility to apoptosis, or enhance the activity of major apoptosis-protective proteins, including heat shock proteins (Hsps), promoting cell survival. Experimental outcomes showed that KRIT1 loss-of-function induces a redox-sensitive sustained upregulation of Nrf2 and Glo1, and a drop in intracellular levels of MG-modified Hsp70 and Hsp27 proteins, leading to a chronic adaptive redox homeostasis that counteracts intrinsic oxidative stress but increases susceptibility to oxidative DNA damage and apoptosis, sensitizing cells to further oxidative challenges. While supporting and extending the pleiotropic functions of KRIT1, these findings shed new light on the mechanistic relationship between KRIT1 loss-of-function and enhanced cell predisposition to oxidative damage, thus providing valuable new insights into CCM pathogenesis and novel options for the development of preventive and therapeutic strategies.

Type III Intermediate Filaments Desmin, Glial Fibrillary Acidic Protein (GFAP), Vimentin, and Peripherin

SummaryType III intermediate filament (IF) proteins assemble into cytoplasmic homopolymeric and heteropolymeric filaments with other type III and some type IV IFs. These highly dynamic structures form an integral component of the cytoskeleton of muscle, brain, and mesenchymal cells. Here, we review the current ideas on the role of type III IFs in health and disease. It turns out that they not only offer resilience to mechanical strains, but, most importantly, they facilitate very efficiently the integration of cell structure and function, thus providing the necessary scaffolds for optimal cellular responses upon biochemical stresses and protecting against cell death, disease, and aging.

αB-crystallin is a sensor for assembly intermediates and for the subunit topology of desmin intermediate filaments

Mutations in the small heat shock protein chaperone CRYAB (αB-crystallin/HSPB5) and the intermediate filament protein desmin, phenocopy each other causing cardiomyopathies. Whilst the binding sites for desmin on CRYAB have been determined, desmin epitopes responsible for CRYAB binding and also the parameters that determine CRYAB binding to desmin filaments are unknown. Using a combination of co-sedimentation centrifugation, viscometric assays and electron microscopy of negatively stained filaments to analyse the in vitro assembly of desmin filaments, we show that the binding of CRYAB to desmin is subject to its assembly status, to the subunit organization within filaments formed and to the integrity of the C-terminal tail domain of desmin. Our in vitro studies using a rapid assembly protocol, C-terminally truncated desmin and two disease-causing mutants (I451M and R454W) suggest that CRYAB is a sensor for the surface topology of the desmin filament. Our data also suggest that CRYAB performs an assembly chaperone role because the assembling filaments have different CRYAB-binding properties during the maturation process. We suggest that the capability of CRYAB to distinguish between filaments with different surface topologies due either to mutation (R454W) or assembly protocol is important to understanding the pathomechanism(s) of desmin-CRYAB myopathies.

Mammalian HspB1 (Hsp27) is a molecular sensor linked to the physiology and environment of the cell

Constitutively expressed small heat shock protein HspB1 regulates many fundamental cellular processes and plays major roles in many human pathological diseases. In that regard, this chaperone has a huge number of apparently unrelated functions that appear linked to its ability to recognize many client polypeptides that are subsequently modified in their activity and/or half-life. A major parameter to understand how HspB1 is dedicated to interact with particular clients in defined cellular conditions relates to its complex oligomerization and phosphorylation properties. Indeed, HspB1 structural organization displays dynamic and complex rearrangements in response to changes in the cellular environment or when the cell physiology is modified. These structural modifications probably reflect the formation of structural platforms aimed at recognizing specific client polypeptides. Here, I have reviewed data from the literature and re-analyzed my own studies to describe and discuss these fascinating changes in HspB1 structural organization.

Protein phosphatase 2A inhibition and subsequent cytoskeleton reorganization contributes to cell migration caused by microcystin-LR in human laryngeal epithelial cells (Hep-2)

The major toxic mechanism of Microcystin-LR is inhibition of the activity of protein phosphatase 2A (PP2A), resulting in a series of cytotoxic effects. Our previous studies have demonstrated that microcystin-LR (MCLR) induced very different molecular effects in normal cells and the tumor cell line SMMC7721. To further explore the MCLR toxicity mechanism in tumor cells, human laryngeal epithelial cells (Hep-2) was examined in this study. Western blot, immunofluorescence, immunoprecipitation, and transwell migration assay were used to detect the effects of MCLR on PP2A activity, PP2A substrates, cytoskeleton, and cell migration. The results showed that the protein level of PP2A subunits and the posttranslational modification of the catalytic subunit were altered and that the binding of the AC core enzyme as well as the binding of PP2A/C and α4, was also affected. As PP2A substrates, the phosphorylation of MAPK pathway members, p38, ERK1/2, and the cytoskeleton-associated proteins, Hsp27, VASP, Tau, and Ezrin were increased. Furthermore, MCLR induced reorganization of the cytoskeleton and promoted cell migration. Taken together, direct covalent binding to PP2A/C, alteration of the protein levels and posttranslational modification, as well as the binding of subunits, are the main pattern for the effects of MCLR on PP2A in Hep-2. A dose-dependent change in p-Tau and p-Ezrin due to PP2A inhibition may contribute to the changes in the cytoskeleton and be related to the cell migration in Hep-2. Our data provide a comprehensive exposition of the MCLR mechanism on tumor cells. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 890-903, 2017.

Functional state of the Hsp27 chaperone as a molecular marker of an unfavorable course of larynx cancer

BACKGROUND

The small heat shock protein 27 kDA (Hsp27) acts as an ATP-independent chaperone in protein folding, but is also implicated in architecture of the cytoskeleton, cell migration, metabolism, cell survival, growth/differentiation, mRNA stabilization, and tumor progression.

OBJECTIVE

To study the intracellular localization of phosphorylated and non-phosphorylated forms of Hsp27 in squamous cell carcinoma of the larynx (SCCL) and to evaluate their relationship with regional lymphatic metastasis and overall five-year survival.

METHODS

Tumor biopsies of larynx tissue were collected from 50 patients who were between the ages of 30 to 80 years and had a confirmed diagnosis of squamous cell carcinoma of the larynx. Immunohistochemistry was used to determine the intracellular localization of the phosphorylated and non-phosphorylated forms of Hsp27.

RESULTS

The study revealed that the Hsp27 chaperone was expressed in both the cytoplasm and the nucleus of tumor cells in SCCL. The biopsies of patients with lymph node metastases showed significantly higher expression of the phosphorylated and unphosphorylated forms of Hsp27 in the nucleus compared to those of patients without lymph node metastases. At the same time, the cytoplasmic expression of Hsp27 in these patients did not differ statistically. Analysis of the overall five-year survival rates showed that negative Hsp27 expression in the nucleus of tumor cells is associated with the survival rate of patients with SCCL.

CONCLUSION

The nuclear expression of phosphorylated and unphosphorylated forms of Hsp27 is a molecular marker of unfavorable squamous cell carcinoma of the larynx associated with lymphogenous metastasis and decreased total five-year survival.

The Potential Functions of Small Heat Shock Proteins in the Uterine Musculature during Pregnancy

The small heat shock protein B (HSPB) family is comprised of eleven members with many being induced by physiological stressors. In addition to being molecular chaperones, it is clear these proteins also play important roles in cell death regulation, cytoskeletal rearrangements, and immune system activation. These processes are important for the uterine smooth muscle or myometrium during pregnancy as it changes from a quiescent tissue, during the majority of pregnancy, to a powerful and contractile tissue at labor. The initiation and progression of labor within the myometrium also appears to require an inflammatory response as it is infiltrated by immune cells and it produces pro-inflammatory mediators. This chapter summarizes current knowledge on the expression of HSPB family members in the myometrium during pregnancy and speculates on the possible roles of these proteins during myometrial programming and transformation of the myometrium into a possible immune regulatory tissue.

AMP-activated protein kinase-mediated expression of heat shock protein beta 1 enhanced insulin sensitivity in the skeletal muscle

Activation of AMP-activated protein kinase (AMPK) has been viewed as an important target for the treatment of insulin resistance. Here, by proteomic analysis, we found that expression of heat shock protein beta-1 (HSPB1) was induced by the AMP analog 5-aminoimidazole-4-carboxamide 1-β-D-ribofuranoside in palmitate-induced insulin-resistant cells. Overexpression of AMPKα2, or activation of AMPKα via acute/chronic exercise training, increased HSPB1 expression in the skeletal muscle. In AMPKα2^-/- mice, HSPB1 expression was downregulated in the quadriceps muscles. Exercise did not increase HSPB1 expression in AMPKα2^-/- mice. Moreover, overexpression of HSPB1 enhanced insulin sensitivity in palmitate-induced insulin-resistant cells and restored metabolic phenotypes associated with defective AMPK. Finally, HSPB1 was required for AMPK-mediated activation of the class IIa histone deacetylases and glucose uptake in the skeletal muscle. Our results demonstrate that AMPK-mediated HSPB1 expression enhanced insulin sensitivity in the skeletal muscle.

Aspirin upregulates αB-Crystallin to protect the myocardium against heat stress in broiler chickens

We established in vivo and in vitro models to investigate the role of αB-Crystallin (CryAB) and assess the ability of aspirin (ASA) to protect the myocardium during prolonged heat stress. Thirty-day-old chickens were divided into three groups (n = 90): heat stress (HS, 40±1 °C); ASA(−)HS(+), 1 mg/kg ASA orally 2 h before heat stress; and ASA(+)HS(−), pretreated with aspirin, no heat stress (25 °C). Hearts were excised after 0, 1, 2, 3, 5, 7, 10, 15 and 24 h. Heat stress increased body temperature, though the ASA(−)HS(+) group had significantly higher temperatures than the ASA(+)HS(+) group at all time points. Compared to ASA(+)HS(+), the ASA(−)HS(+) group displayed increased sensitivity to heat stress. Pathological analysis revealed the ASA (+)HS(+) myocardium showed less severe changes (narrowed, chaotic fibers; fewer necrotic cells) than the ASA(−)HS(+) group (bleeding and extensive cell death). In vitro, ASA-pretreatment significantly increased primary chicken myocardial cell survival during heat stress. ELISAs indicated ASA induced CryAB in vivo to protect against heat stress-induced myocardial damage, but ASA did not induce CryAB in primary chicken myocardial cells. The mechanisms by which ASA induces the expression of CryAB in vivo and protects the myocardium during heat stress merit further research.

Small Heat Shock Proteins and Distal Hereditary Neuropathies

Classification of small heat shock proteins (sHsp) is presented and processes regulated by sHsp are described. Symptoms of hereditary distal neuropathy are described and the genes whose mutations are associated with development of this congenital disease are listed. The literature data and our own results concerning physicochemical properties of HspB1 mutants associated with Charcot-Marie-Tooth disease are analyzed. Mutations of HspB1, associated with hereditary motor neuron disease, can be accompanied by change of the size of HspB1 oligomers, by decreased stability under unfavorable conditions, by changes in the interaction with protein partners, and as a rule by decrease of chaperone-like activity. The largest part of these mutations is accompanied by change of oligomer stability (that can be either increased or decreased) or by change of intermonomer interaction inside an oligomer. Data on point mutation of HspB3 associated with axonal neuropathy are presented. Data concerning point mutations of Lys141 of HspB8 and those associated with hereditary neuropathy and different forms of Charcot-Marie-Tooth disease are analyzed. It is supposed that point mutations of sHsp associated with distal neuropathies lead either to loss of function (for instance, decrease of chaperone-like activity) or to gain of harmful functions (for instance, increase of interaction with certain protein partners).

Exercise-induced ROS in heat shock proteins response

Cells have evolved multiple and sophisticated stress response mechanisms aiming to prevent macromolecular (including proteins, lipids, and nucleic acids) damage and to maintain or re-establish cellular homeostasis. Heat shock proteins (HSPs) are among the most highly conserved, ubiquitous, and abundant proteins in all organisms. Originally discovered more than 50 years ago through heat shock stress, they display multiple, remarkable roles inside and outside cells under a variety of stresses, including also oxidative stress and radiation, recognizing unfolded or misfolded proteins and facilitating their restructuring. Exercise consists in a combination of physiological stresses, such as metabolic disturbances, changes in circulating levels of hormones, increased temperature, induction of mild to severe inflammatory state, increased production of reactive oxygen and nitrogen species (ROS and RNS). As a consequence, exercise is one of the main stimuli associated with a robust increase in different HSPs in several tissues, which appears to be also fundamental in facilitating the cellular remodeling processes related to the training regime. Among all factors involved in the exercise-related modulation of HSPs level, the ROS production in the contracting muscle or in other tissues represents one of the most attracting, but still under discussion, mechanism. Following exhaustive or damaging muscle exercise, major oxidative damage to proteins and lipids is likely involved in HSP expression, together with mechanically induced damage to muscle proteins and the inflammatory response occurring several days into the recovery period. Instead, the transient and reversible oxidation of proteins by physiological concentrations of ROS seems to be involved in the activation of stress response following non-damaging muscle exercise. This review aims to provide a critical update on the role of HSPs response in exercise-induced adaptation or damage in humans, focusing on experimental results where the link between redox homeostasis and HSPs expression by exercise has been addressed. Further, with the support of in vivo and in vitro studies, we discuss the putative molecular mechanisms underlying the ROS-mediated modulation of HSP expression and/or activity during exercise.

Rapid proteomic responses to a near-lethal heat stress in the salt marsh mussel Geukensia demissa

Acute heat stress perturbs cellular function on a variety of levels, leading to protein dysfunction and aggregation, oxidative stress and loss of metabolic homeostasis. If these challenges are not overcome quickly, the stressed organism can die. To better understand the earliest tissue-level responses to heat stress, we examined the proteomic response of gill from Geukensia demissa, an extremely eurythermal mussel from the temperate intertidal zone of eastern North America. We exposed 15°C-acclimated individuals to an acute near-lethal heat stress (45°C) for 1 h, and collected gill samples from 0 to 24 h of recovery. The changes in protein expression we found reveal a coordinated physiological response to acute heat stress: proteins associated with apoptotic processes were increased in abundance during the stress itself (i.e. at 0 h of recovery), while protein chaperones and foldases increased in abundance soon after (3 h). The greatest number of proteins changed abundance at 6 h; these included oxidative stress proteins and enzymes of energy metabolism. Proteins associated with the cytoskeleton and extracellular matrix also changed in abundance starting at 6 h, providing evidence of cell proliferation, migration and tissue remodeling. By 12 h, the response to acute heat stress was diminishing, with fewer stress and structural proteins changing in abundance. Finally, the proteins with altered abundances identified at 24 h suggest a return to the pre-stress anabolic state.

Desmin and αB-crystallin interplay in the maintenance of mitochondrial homeostasis and cardiomyocyte survival

The association of desmin with the α-crystallin Β-chain (αΒ-crystallin; encoded by CRYAB), and the fact that mutations in either one of them leads to heart failure in humans and mice, suggests a potential compensatory interplay between the two in cardioprotection. To address this hypothesis, we investigated the consequences of αΒ-crystallin overexpression in the desmin-deficient (Des^-/-) mouse model, which possesses a combination of the pathologies found in most cardiomyopathies, with mitochondrial defects as a hallmark. We demonstrated that cardiac-specific αΒ-crystallin overexpression ameliorates all these defects and improves cardiac function to almost wild-type levels. Protection by αΒ-crystallin overexpression is linked to maintenance of proper mitochondrial protein levels, inhibition of abnormal mitochondrial permeability transition pore activation and maintenance of mitochondrial membrane potential (Δψ_m). Furthermore, we found that both desmin and αΒ-crystallin are localized at sarcoplasmic reticulum (SR)-mitochondria-associated membranes (MAMs), where they interact with VDAC, Mic60 - the core component of mitochondrial contact site and cristae organizing system (MICOS) complex - and ATP synthase, suggesting that these associations could be crucial in mitoprotection at different levels.

HSPB3 protein is expressed in motoneurons and induces their survival after lesion-induced degeneration

The human small heat shock proteins (HSPBs) form a family of molecular chaperones comprising ten members (HSPB1-HSPB10), whose functions span from protein quality control to cytoskeletal dynamics and cell death control. Mutations in HSPBs can lead to human disease and particularly point mutations in HSPB1 and HSPB8 are known to lead to peripheral neuropathies. Recently, a missense mutation (R7S) in yet another member of this family, HSPB3, was found to cause an axonal motor neuropathy (distal hereditary motor neuropathy type 2C, dHMN2C). Until now, HSPB3 protein localization and function in motoneurons (MNs) have not yet been characterized. Therefore, we studied the endogenous HSPB3 protein distribution in the spinal cords of chicken and mouse embryos and in the postnatal nervous system (central and peripheral) of chicken, mouse and human. We further investigated the impact of wild-type and mutated HSPB3 on MN cell death via overexpressing these genes in ovo in an avian model of MN degeneration, the limb-bud removal. Altogether, our findings represent a first step for a better understanding of the cellular and molecular mechanisms leading to dHMN2C.

Induction of expression and phosphorylation of heat shock protein B5 (CRYAB) in rat myometrium during pregnancy and labour

During pregnancy the myometrium undergoes a programme of differentiation induced by endocrine, cellular, and biophysical inputs. Small heat shock proteins (HSPs) are a family of ten (B1–B10) small-molecular-weight proteins that not only act as chaperones, but also assist in processes such as cytoskeleton rearrangements and immune system activation. Thus, it was hypothesized that HSPB5 (CRYAB) would be highly expressed in the rat myometrium during the contractile and labour phases of myometrial differentiation when such processes are prominent. Immunoblot analysis revealed that myometrial CRYAB protein expression significantly increased from day (D) 15 to D23 (labour;P<0.05). In correlation with these findings, serine 59-phosphorylated (pSer59) CRYAB protein expression significantly increased from D15 to D23, and was also elevated 1-day post-partum (P<0.05). pSer59-CRYAB was detected in the cytoplasm of myocytes within both uterine muscle layers mid- to late-pregnancy. In unilaterally pregnant rats, pSer59-CRYAB protein expression was significantly elevated in the gravid uterine horns at both D19 and D23 of gestation compared with non-gravid horns. Co-immunolocalization experiments using the hTERT-human myometrial cell line and confocal microscopy demonstrated that pSer59-CRYAB co-localized with the focal adhesion protein FERMT2 at the ends of actin filaments as well as with the exosomal marker CD63. Overall, pSer59-CRYAB is highly expressed in myometrium during late pregnancy and labour and its expression appears to be regulated by uterine distension. CRYAB may be involved in the regulation of actin filament dynamics at focal adhesions and could be secreted by exosomes as a prelude to involvement in immune activation in the myometrium.

Age-dependent transcriptional and epigenomic responses to light exposure in the honey bee brain

Light is a powerful environmental stimulus of special importance in social honey bees that undergo a behavioral transition from in-hive to outdoor foraging duties. Our previous work has shown that light exposure induces structural neuronal plasticity in the mushroom bodies (MBs), a brain center implicated in processing inputs from sensory modalities. Here, we extended these analyses to the molecular level to unravel light-induced transcriptomic and epigenomic changes in the honey bee brain. We have compared gene expression in brain compartments of 1- and 7-day-old light-exposed honey bees with age-matched dark-kept individuals. We have found a number of differentially expressed genes (DEGs), both novel and conserved, including several genes with reported roles in neuronal plasticity. Most of the DEGs show age-related changes in the amplitude of light-induced expression and are likely to be both developmentally and environmentally regulated. Some of the DEGs are either known to be methylated or are implicated in epigenetic processes suggesting that responses to light exposure are at least partly regulated at the epigenome level. Consistent with this idea light alters the DNA methylation pattern of bgm, one of the DEGs affected by light exposure, and the expression of microRNA miR-932. This confirms the usefulness of our approach to identify candidate genes for neuronal plasticity and provides evidence for the role of epigenetic processes in driving the molecular responses to visual stimulation.

Heat shock proteins in the retina: Focus on HSP70 and alpha crystallins in ganglion cell survival

Heat shock proteins (HSPs) belong to a superfamily of stress proteins that are critical constituents of a complex defense mechanism that enhances cell survival under adverse environmental conditions. Cell protective roles of HSPs are related to their chaperone functions, antiapoptotic and antinecrotic effects. HSPs' anti-apoptotic and cytoprotective characteristics, their ability to protect cells from a variety of stressful stimuli, and the possibility of their pharmacological induction in cells under pathological stress make these proteins an attractive therapeutic target for various neurodegenerative diseases; these include Alzheimer's, Parkinson's, Huntington's, prion disease, and others. This review discusses the possible roles of HSPs, particularly HSP70 and small HSPs (alpha A and alpha B crystallins) in enhancing the survival of retinal ganglion cells (RGCs) in optic neuropathies such as glaucoma, which is characterized by progressive loss of vision caused by degeneration of RGCs and their axons in the optic nerve. Studies in animal models of RGC degeneration induced by ocular hypertension, optic nerve crush and axotomy show that upregulation of HSP70 expression by hyperthermia, zinc, geranyl-geranyl acetone, 17-AAG (a HSP90 inhibitor), or through transfection of retinal cells with AAV2-HSP70 effectively supports the survival of injured RGCs. RGCs survival was also stimulated by overexpression of alpha A and alpha B crystallins. These findings provide support for translating the HSP70- and alpha crystallin-based cell survival strategy into therapy to protect and rescue injured RGCs from degeneration associated with glaucomatous and other optic neuropathies.

αB-Crystallin Regulates Subretinal Fibrosis by Modulation of Epithelial-Mesenchymal Transition

Subretinal fibrosis is an end stage of neovascular age-related macular degeneration, characterized by fibrous membrane formation after choroidal neovascularization. An initial step of the pathogenesis is an epithelial-mesenchymal transition (EMT) of retinal pigment epithelium cells. αB-crystallin plays multiple roles in age-related macular degeneration, including cytoprotection and angiogenesis. However, the role of αB-crystallin in subretinal EMT and fibrosis is unknown. Herein, we showed attenuation of subretinal fibrosis after regression of laser-induced choroidal neovascularization and a decrease in mesenchymal retinal pigment epithelium cells in αB-crystallin knockout mice compared with wild-type mice. αB-crystallin was prominently expressed in subretinal fibrotic lesions in mice. In vitro, overexpression of αB-crystallin induced EMT, whereas suppression of αB-crystallin induced a mesenchymal-epithelial transition. Transforming growth factor-β2-induced EMT was further enhanced by overexpression of αB-crystallin but was inhibited by suppression of αB-crystallin. Silencing of αB-crystallin inhibited multiple fibrotic processes, including cell proliferation, migration, and fibronectin production. Bone morphogenetic protein 4 up-regulated αB-crystallin, and its EMT induction was inhibited by knockdown of αB-crystallin. Furthermore, inhibition of αB-crystallin enhanced monotetraubiquitination of SMAD4, which can impair its nuclear localization. Overexpression of αB-crystallin enhanced nuclear translocation and accumulation of SMAD4 and SMAD5. Thus, αB-crystallin is an important regulator of EMT, acting as a molecular chaperone for SMAD4 and as its potential therapeutic target for preventing subretinal fibrosis development in neovascular age-related macular degeneration.

l-glutamine and l-alanine supplementation increase glutamine-glutathione axis and muscle HSP-27 in rats trained using a progressive high-intensity resistance exercise

In this study we investigated the chronic effects of oral l-glutamine and l-alanine supplementation, either in their free or dipeptide form, on glutamine-glutathione (GLN-GSH) axis and cytoprotection mediated by HSP-27 in rats submitted to resistance exercise (RE). Forty Wistar rats were distributed into 5 groups: sedentary; trained (CTRL); and trained supplemented with l-alanyl-l-glutamine, l-glutamine and l-alanine in their free form (GLN+ALA), or free l-alanine (ALA). All trained animals were submitted to a 6-week ladder-climbing protocol. Supplementations were offered in a 4% drinking water solution for 21 days prior to euthanasia. Plasma glutamine, creatine kinase (CK), myoglobin (MYO), and erythrocyte concentration of reduced GSH and glutathione disulfide (GSSG) were measured. In tibialis anterior skeletal muscle, GLN-GSH axis, thiobarbituric acid reactive substances (TBARS), and the expression of heat shock factor 1 (HSF-1), 27-kDa heat shock protein (HSP-27), and glutamine synthetase were determined. In CRTL animals, high-intensity RE reduced muscle glutamine levels and increased GSSG/GSH rate and TBARS, as well as augmented plasma CK and MYO levels. Conversely, l-glutamine-supplemented animals showed an increase in plasma and muscle levels of glutamine, with a reduction in GSSG/GSH rate, TBARS, and CK. Free l-alanine administration increased plasma glutamine concentration and lowered muscle TBARS. HSF-1 and HSP-27 were high in all supplemented groups when compared with CTRL (p < 0.05). The results presented herein demonstrate that l-glutamine supplemented with l-alanine, in both a free or dipeptide form, improve the GLN-GSH axis and promote cytoprotective effects in rats submitted to high-intensity RE training.

Small Heat Shock Proteins Are Novel Common Determinants of Alcohol and Nicotine Sensitivity in Caenorhabditis elegans

Addiction to drugs is strongly determined by multiple genetic factors. Alcohol and nicotine produce distinct pharmacological effects within the nervous system through discrete molecular targets; yet, data from family and twin analyses support the existence of common genetic factors for addiction in general. The mechanisms underlying addiction, however, are poorly described and common genetic factors for alcohol and nicotine remain unidentified. We investigated the role that the heat shock transcription factor, HSF-1, and its downstream effectors played as common genetic modulators of sensitivity to addictive substances. Using Caenorhabditis elegans, an exemplary model organism with substance dose-dependent responses similar to mammals, we demonstrate that HSF-1 altered sensitivity to both alcohol and nicotine. Using a combination of a targeted RNAi screen of downstream factors and transgenic approaches we identified that these effects were contingent upon the constitutive neuronal expression of HSP-16.48, a small heat shock protein (HSP) homolog of human α-crystallin. Furthermore we demonstrated that the function of HSP-16.48 in drug sensitivity surprisingly was independent of chaperone activity during the heat shock stress response. Instead we identified a distinct domain within the N-terminal region of the HSP-16.48 protein that specified its function in comparison to related small HSPs. Our findings establish and characterize a novel genetic determinant underlying sensitivity to diverse addictive substances.

Heat Shock Protein 27 Plays a Pivotal Role in Myofibroblast Differentiation and in the Development of Bleomycin-Induced Pulmonary Fibrosis

Heat shock protein 27 (HSP27) is a member of the small molecular weight HSP family. Upon treatment with transforming growth factor β1 (TGF-β1), we observed upregulation of HSP27 along with that of α-smooth muscle actin (α-SMA), a marker of myofibroblast differentiation, in cultured human and mouse lung fibroblasts. Furthermore, by using siRNA knockdown, we demonstrated that HSP27 was involved in cell survival and upregulation of fibronectin, osteopontin (OPN) and type 1 collagen, all functional markers of myofibroblast differentiation, in TGF-β1-treated MRC-5 cells. In lung tissues of bleomycin-treated mice, HSP27 was strongly upregulated and substantially co-localized with α-SMA, OPN and type I collagen but not with proSP-C (a marker of type II alveolar epithelial cells), E-cadherin (a marker of epithelial cells) or F4/80 (a marker of macrophages). A similar co-localization of HSP27 and α-SMA was observed in lung tissues of patients with idiopathic pulmonary fibrosis. Furthermore, airway delivery of HSP27 siRNA effectively suppressed bleomycin-induced pulmonary fibrosis in mice. Collectively, our findings indicate that HSP27 is critically involved in myofibroblast differentiation of lung fibroblasts and may be a promising therapeutic target for lung fibrotic diseases.

Expression profiles of heat shock protein 27 and αB-crystallin and their effects on heat-stressed rat myocardial cells in vitro and in vivo

The present study established a heat-stressed rat heart model, and used an H9c2 myocardial cell line to investigate the expression profiles of heat shock protein (Hsp)27 and αB-crystallin, both in vivo and in vitro. Rats and myocardial cells were subjected to 42 ˚C for 0, 20, 40, 60, 80 or 100 min, following which the mRNA and protein expression levels of Hsp27 and αB-crystallin were measured. Following heat shock, the protein expression levels of Hsp27 and αB-crystallin were significantly decreased in the rat heart cells in vivo, whereas their mRNA levels were significantly increased. The opposing association between the protein and mRNA expression levels of Hsp27 and αB-crystallin suggests that the progression from mRNA into proteins via translation may delayed, or proteins may exist as either oligomers or in the phosphorylated form under heat stress. In vitro, Hsp27 and αB-crystallin exhibited similar reductions in the protein levels at 40 and 60 min, then increased to normal values following 80 min of heat stress. However, the mRNA levels were not consistent with the protein levels. The mRNA levels of Hsp27 and αB-crystallin did however exhibit similar tendencies following 60 min of heat stress. The present study investigated these apparently conflicting results between the in vitro cell line and the in vivo body system. The results demonstrated that the protein and mRNA expression levels of Hsp27 and αB-crystallin exhibited similar trends in vivo and in vitro, respectively. These results were confirmed by analysis with STRING 9.1 software, which indicated that Hsp27 and αB-crystallin are co-expressed in rat myocardial cells. However, the individual cell lines and whole body system exhibited different trends in Hsp27 and αB-crystallin levels prior to and following heat stress, thus require further investigation.

Phenyl Saligenin Phosphate Induced Caspase-3 and c-Jun N-Terminal Kinase Activation in Cardiomyocyte-Like Cells

At present, little is known about the effect(s) of organophosphorous compounds (OPs) on cardiomyocytes. In this study, we have investigated the effects of phenyl saligenin phosphate (PSP), two organophosphorothioate insecticides (diazinon and chlorpyrifos), and their acutely toxic metabolites (diazoxon and chlorpyrifos oxon) on mitotic and differentiated H9c2 cardiomyoblasts. OP-induced cytotoxicity was assessed by monitoring MTT reduction, LDH release, and caspase-3 activity. Cytotoxicity was not observed with diazinon, diazoxon, or chlorpyrifos oxon (48 h exposure; 200 μM). Chlorpyrifos-induced cytotoxicity was only evident at concentrations >100 μM. In marked contrast, PSP displayed pronounced cytotoxicity toward mitotic and differentiated H9c2 cells. PSP triggered the activation of JNK1/2 but not ERK1/2, p38 MAPK, or PKB, suggesting a role for this pro-apoptotic protein kinase in PSP-induced cell death. The JNK1/2 inhibitor SP 600125 attenuated PSP-induced caspase-3 and JNK1/2 activation, confirming the role of JNK1/2 in PSP-induced cytotoxicity. Fluorescently labeled PSP (dansylated PSP) was used to identify novel PSP binding proteins. Dansylated PSP displayed cytotoxicity toward differentiated H9c2 cells. 2D-gel electrophoresis profiles of cells treated with dansylated PSP (25 μM) were used to identify proteins fluorescently labeled with dansylated PSP. Proteomic analysis identified tropomyosin, heat shock protein β-1, and nucleolar protein 58 as novel protein targets for PSP. In summary, PSP triggers cytotoxicity in differentiated H9c2 cardiomyoblasts via JNK1/2-mediated activation of caspase-3. Further studies are required to investigate whether the identified novel protein targets of PSP play a role in the cytotoxicity of this OP, which is usually associated with the development of OP-induced delayed neuropathy.

Role of cellular cytoskeleton in epithelial-mesenchymal transition process during cancer progression

Currently, cancer metastases remain a major clinical problem that highlights the importance of recognition of the metastatic process in cancer diagnosis and treatment. A critical process associated with the metastasis process is the transformation of epithelial cells toward the motile mesenchymal state, a process called epithelial-mesenchymal transition (EMT). Increasing evidence suggests the crucial role of the cytoskeleton in the EMT process. The cytoskeleton is composed of the actin cytoskeleton, the microtubule network and the intermediate filaments that provide structural design and mechanical strength that is necessary for the EMT. The dynamic reorganization of the actin cytoskeleton is a prerequisite for the morphology, migration and invasion of cancer cells. The microtubule network is the cytoskeleton that provides the driving force during cell migration. Intermediate filaments are significantly rearranged, typically switching from cytokeratin-rich to vimentin-rich networks during the EMT process, accompanied by a greatly enhanced cell motility capacity. In the present review, the recent novel insights into the different cytoskeleton underlying EMT are summarized. There are numerous advances in our understanding of the fundamental role of the cytoskeleton in cancer cell invasion and migration.

BmHSP20.8 is Localized in the Mitochondria and has a Molecular Chaperone Function In Vitro

Heat shock proteins (HSPs) are abundant and ubiquitous in almost all organisms from bacteria to mammals. BmHSP20.8 is a small (sHSP) in Bombyx mori that contains a 561 bp open reading frame that encodes a protein of 186 amino acid residues with a predicted molecular mass of 20.8 kDa. The subcellular localization prediction indicated that BmHSP20.8 is likely distributed in the mitochondria with a 51% probability. To identify the subcellular localization of BmHSP20.8, three recombinant vectors were constructed and used to transfect BmN cells. The cytoplasmic and mitochondrial proteins were extracted 72 h after transfection. The Western blot showed that recombinant BmHSP20.8 exists only in the mitochondria. To locate the mitochondrial localization signal domain of BmHSP20.8 more accurately, we cloned four truncated recombinant vectors. The Western blot analysis of the cytoplasmic and mitochondrial proteins showed that the mitochondrial localization signal domain of BmHSP20.8 is located between amino acids 143 to 186. We constructed the pETduet-HIS-SUMO-BmHSP20.8 vector and a soluble BmHSP20.8 was expressed. In a citrate synthase (CS) thermal aggregation experiment, we found that the recombinant BmHSP20.8 protein can protect CS from aggregating at 43 and 48 °C and thus exhibited molecular chaperone activity. Taken together, the results showed that BmHSP20.8 could be a mitochondrial protein and has a molecular chaperone activity, suggesting an important role in mitochondria.

Characterization of Mutants of Human Small Heat Shock Protein HspB1 Carrying Replacements in the N-Terminal Domain and Associated with Hereditary Motor Neuron Diseases

Physico-chemical properties of the mutations G34R, P39L and E41K in the N-terminal domain of human heat shock protein B1 (HspB1), which have been associated with hereditary motor neuron neuropathy, were analyzed. Heat-induced aggregation of all mutants started at lower temperatures than for the wild type protein. All mutations decreased susceptibility of the N- and C-terminal parts of HspB1 to chymotrypsinolysis. All mutants formed stable homooligomers with a slightly larger apparent molecular weight compared to the wild type protein. All mutations analyzed decreased or completely prevented phosphorylation-induced dissociation of HspB1 oligomers. When mixed with HspB6 and heated, all mutants yielded heterooligomers with apparent molecular weights close to ~400 kDa. Finally, the three HspB1 mutants possessed lower chaperone-like activity towards model substrates (lysozyme, malate dehydrogenase and insulin) compared to the wild type protein, conversely the environmental probe bis-ANS yielded higher fluorescence with the mutants than with the wild type protein. Thus, in vitro the analyzed N-terminal mutations increase stability of large HspB1 homooligomers, prevent their phosphorylation-dependent dissociation, modulate their interaction with HspB6 and decrease their chaperoning capacity, preventing normal functioning of HspB1.

Antifibrotic role of αB-crystallin inhibition in pleural and subpleural fibrosis

Idiopathic pulmonary fibrosis (IPF) is a devastating disease characterized by myofibroblast proliferation and extracellular-matrix accumulation. IPF typically starts in subpleural lung regions, and recent studies suggest that pleural mesothelial cells play a role in the onset of the disease. The transition of mesothelial cells into myofibroblasts (mesothelio-mesenchymal transition) is induced by the profibrotic cytokine, transforming growth factor (TGF)-β1, and is thought to play a role in the development and progression of IPF. The Mothers Against Decapentaplegic homolog (Smad)-dependent pathway is the main TGF-β1 pathway involved in fibrosis. αB-crystallin is constitutively expressed in the lungs, and is inducible by stress, acts as a chaperon, and is known to play a role in cell cytoskeleton architecture. We recently showed that the lack of αB-crystallin hampered TGF-β1 signaling by favoring Smad4 monoubiquitination and nuclear export. We demonstrate here, for the first time, that αB-crystallin is strongly overexpressed in the pleura of fibrotic lungs from patients with IPF and in rodent models of pleural/subpleural fibrosis. αB-crystallin-deficient mice are protected from pleural/subpleural fibrosis induced by the transient adenoviral-mediated overexpression of TGF-β1 or the intrapleural injection of bleomycin combined with carbon particles. We show that αB-crystallin inhibition hampers Smad4 nuclear localization in pleural mesothelial cells and the consequent characteristics of mesothelio-mesenchymal transition. αB-crystallin-deficient mesothelial cells fail to acquire the properties of myofibroblasts, thus limiting their migration in vivo and the progression of fibrosis in the lung parenchyma. In conclusion, our work demonstrates that αB-crystallin may be a key target for the development of specific drugs in the treatment of IPF.

Attempt to optimize some properties of fluorescent chimeras of human small heat shock protein HspB1 by modifying linker length and nature

Chimerical proteins consisting of enhanced yellow fluorescent protein (EYFP) connected by linkers of different length and nature to the N-terminal end of small heat shock protein HspB1 were obtained and characterized. To obtain fluorescent chimeras with properties similar to those of unmodified small heat shock protein, we used either 12-residue-long linkers of different nature (highly flexible Gly-Ser linker (L1), rigid α-helical linker (L2), or rigid Pro-Ala linker (L3)) or highly flexible Gly-Ser linker consisting of 12, 18, or 21 residues. The wild-type HspB1 formed large stable oligomers consisting of more than 20 subunits. Independent of the length or the nature of the linker, all the fluorescent chimeras formed small (5-9 subunits) oligomers tending to dissociate at low protein concentration. Chaperone-like activity of the wild-type HspB1 and its fluorescent chimeras were compared using lysozyme as a model protein substrate. Under the conditions used, all the fluorescent chimeras possessed higher chaperone-like activity than the wild-type HspB1. Chaperone-like activity of fluorescent chimeras with L1 and L3 linkers was less different from that of the wild-type HspB1 compare to the chaperone-like activity of chimeras with rigid L2 linker. Increase in the length of L1 linker from 12 up to 21 residues leads to decrease in the difference in the chaperone-like activity between the wild-type protein and its fluorescent chimeras. Since the N-terminal domain of small heat shock proteins participates in formation of large oligomers, any way of attachment of fluorescent protein to the N-terminal end of HspB1 leads to dramatic changes in its oligomeric structure. Long flexible linkers should be used to obtain fluorescent chimeras with chaperone-like properties similar to those of the wild-type HspB1.

The regulation of connective tissue growth factor expression influences the viability of human trabecular meshwork cells

Connective tissue growth factor (CTGF) induces extracellular matrix (ECM) synthesis and contractility in human trabecular meshwork (HTM) cells. Both processes are involved in the pathogenesis of primary open-angle glaucoma. To date, little is known about regulation and function of CTGF expression in the trabecular meshwork (TM). Therefore, we analysed the effects of different aqueous humour proteins and stressors on CTGF expression in HTM cells. HTM cells from three different donors were treated with endothelin-1, insulin-like growth factor (IGF)-1, angiotensin-II, H₂O₂ and heat shock and were analysed by immunohistochemistry, real-time RT-PCR and Western blotting. Viability after H₂O₂ treatment was measured in CTGF silenced HTM-N cells and their controls. Latrunculin A reduced expression of CTGF by about 50% compared to untreated HTM cells, whereas endothelin-1, IGF-1, angiotensin-II, heat shock and oxidative stress led to a significant increase. Silencing of CTGF resulted in a delayed expression of αB-crystallin and in reduced cell viability in comparison to the controls after oxidative stress. Conversely, CTGF treatment led to a higher cell viability rate after H₂O₂ treatment. CTGF expression is induced by factors that have been linked to glaucoma. An increased level of CTGF appears to protect TM cells against damage induced by stress. The beneficial effect of CTGF for viability of TM cells is likely associated with the effects on increased ECM synthesis and higher contractility of the TM, thereby contributing to reduced aqueous humour outflow facility causing increased intraocular pressure.

Cryopreservation effects on Wharton's Jelly Stem Cells proteome

Cryopreservation is the only method for long-term storage of viable cells and tissues used for cellular therapy, stem cell transplantation and/or tissue engineering. However, the freeze-thaw process strongly contributes to cell and tissue damage through several mechanisms, including oxidative stress, cell injury from intracellular ice formation and altered physical cellular properties. Our previous proteomics investigation was carried out on Wharton's Jelly Stem Cells (WJSCs) having similar properties to adult mesenchymal stem cells and thus representing a rich source of primitive cells to be potentially used in regenerative medicine. The aim of the present work was to investigate molecular changes that occur in WJSCs proteome in different experimental conditions: fresh primary cell culture and frozen cell. To analyze changes in protein expression of WJSCs undergoing different culturing procedures, we performed a comparative proteomic analysis (2DE followed by MALDI-TOF MS/MS nanoESI-Q-TOF MS coupled with nanoLC) between WJSCs from fresh and frozen cell culturing, respectively. Frozen WJSCs showed qualitative and quantitative changes compared to cells from fresh preparation, expressing proteins involved in replication, cellular defence mechanism and metabolism, that could ensure freeze-thaw survival. The results of this study could play a key role in elucidating possible mechanisms related to maintaining active proliferation and maximal cellular plasticity and thus making the use of WJSCs in cell therapy safe following bio-banking.

Behavioral and proteomic analysis of stress response in zebrafish (Danio rerio)

The purpose of this study is to determine the behavioral and proteomic consequences of shock-induced stress in zebrafish (Danio rerio) as a vertebrate model. Here we describe the behavioral effects of exposure to predictable and unpredictable electric shock, together with quantitative tandem mass tag isobaric labeling workflow to detect altered protein candidates in response to shock exposure. Behavioral results demonstrate a hyperactivity response to electric shock and a suppression of activity to a stimulus predicting shock. On the basis of the quantitative changes in protein abundance following shock exposure, eight proteins were significantly up-regulated (HADHB, hspa8, hspa5, actb1, mych4, atp2a1, zgc:86709, and zgc:86725). These proteins contribute crucially in catalytic activities, stress response, cation transport, and motor activities. This behavioral proteomic driven study clearly showed that besides the rapid induction of heat shock proteins, other catalytic enzymes and cation transporters were rapidly elevated as a mechanism to counteract oxidative stress conditions resulting from elevated fear/anxiety levels.

Research on the efficacy of Celastrus Orbiculatus in suppressing TGF-β1-induced epithelial-mesenchymal transition by inhibiting HSP27 and TNF-α-induced NF-κ B/Snail signaling pathway in human gastric adenocarcinoma

BACKGROUND

Celastrus orbiculatus has been used as a folk medicine in China for the treatment of many diseases. In the laboratory, the ethyl acetate extract of Celastrus orbiculatus (COE) displays a wide range of anticancer functions. However, the inhibition of the metastasis mechanism of COE in gastric cancer cells has not been investigated so far.

METHODS

The present study was undertaken to determine if the anti-metastasis effect of COE was involved in inhibiting of epithelial-mesenchymal transition (EMT) of human gastric adenocarcinoma SGC-7901 cells. In vitro, a well-established experimental EMT model involving transforming growth factor β1 (TGF-β1) was applied. Viability, invasion and migration, protein and mRNA expression of tumor cells were analyzed by MTT assay, transwell assay, western blot and real-time PCR, respectively. The molecular targets of COE in SGC-7901 cells were investigated by two-dimensional gel electrophoresis (2-DE) and MALDI-TOF-TOF mass spectrometer. Overexpression of heat shock protein 27 (HSP27) was performed by transfected with the recombinant retroviral expression plasmid. In vivo, the anti-metastasis mechanisms of COE in the peritoneal gastric cancer xenograft model was explored and the effect was tested.

RESULTS

The non-cytostatic concentrations of COE effectively inhibited TGF-β1 induced EMT process in SGC-7901 cells, which is characterized by prevented morphological changes, increased E-cadherin expression and decreased Vimentin, N-cadherin expression. Moreover, COE inhibited invasion and migration induced by TGF-β1. Using a comparative proteomics approach, four proteins were identified as differently expressed, with HSP27 protein being one of the most significantly down-regulated proteins induced by COE. Moreover, the activation of nuclear factor κB (NF-κB)/Snail signaling pathway induced by tumor necrosis factor-α (TNF-α) was also attenuated under the pretreatment of COE. Interestingly, overexpression of HSP27 significantly decreases the inhibitory effect of COE on EMT and the NF-κB/Snail pathway. Furthermore, COE significantly reduced the number of peritoneal metastatic nodules in the peritoneal gastric cancer xenograft model.

CONCLUSIONS

Taken together, these results suggest that COE inhibits the EMT by suppressing the expression of HSP27, correlating with inhibition of NF-κB/Snail signal pathways in SGC-7901 cells. Based on these results, COE may be considered a novel anti-cancer agent for the treatment of metastasis in gastric cancer.

Effect of disulfide crosslinking on thermal transitions and chaperone-like activity of human small heat shock protein HspB1

Temperature-induced conformational changes of reduced and oxidized HspB1 crosslinked by disulfide bond between single Cys137 of neighboring monomers were analyzed by means of different techniques. Heating of reduced HspB1 was accompanied by irreversible changes of Trp fluorescence, whereas oxidized HspB1 underwent completely reversible changes of fluorescence. Increase of the temperature in the range of 20-70 °C was accompanied by self-association of both reduced and oxidized protein. Further increase of the temperature led to formation of heterogeneous mixture of large self-associated complexes of reduced HspB1 and to formation of smaller and less heterogeneous complexes of oxidized HspB1. Heat-induced changes of oligomeric state of reduced HspB1 were only partially reversible, whereas the corresponding changes of oligomeric state of oxidized HspB1 were almost completely reversible. Oxidation resulted in decrease of chaperone-like activity of HspB1. It is concluded that oxidative stress, inducing formation of disulfide bond, can affect stability and conformational mobility of human HspB1.

Overexpression of heat shock protein 27 (HSP27) increases gemcitabine sensitivity in pancreatic cancer cells through S-phase arrest and apoptosis

We previously established a role for HSP27 as a predictive marker for therapeutic response towards gemcitabine in pancreatic cancer. Here, we investigate the underlying mechanisms of HSP27-mediated gemcitabine sensitivity. Utilizing a pancreatic cancer cell model with stable HSP27 overexpression, cell cycle arrest and apoptosis induction were analysed by flow cytometry, nuclear staining, immunoblotting and mitochondrial staining. Drug sensitivity studies were performed by proliferation assays. Hyperthermia was simulated using mild heat shock at 41.8°C. Upon gemcitabine treatment, HSP27-overexpressing cells displayed an early S-phase arrest subsequently followed by a strongly increased sub-G1 fraction. Apoptosis was characterized by PARP-, CASPASE 3-, CASPASE 8-, CASPASE 9- and BIM- activation along with a mitochondrial membrane potential loss. It was reversible through chemical caspase inhibition. Importantly, gemcitabine sensitivity and PARP cleavage were also elicited by heat shock-induced HSP27 overexpression, although to a smaller extent, in a panel of pancreatic cancer cell lines. Finally, HSP27-overexpressing pancreatic cancer cells displayed an increased sensitivity also towards death receptor-targeting agents, suggesting another pro-apoptotic role of HSP27 along the extrinsic apoptosis pathway. Taken together, in contrast to the well-established anti-apoptotic properties of HSP27 in cancer, our study reveals novel pro-apoptotic functions of HSP27—mediated through both the intrinsic and the extrinsic apoptotic pathways—at least in pancreatic cancer cells. HSP27 could represent a predictive marker of therapeutic response towards specific drug classes in pancreatic cancer and provides a novel molecular rationale for current clinical trials applying the combination of gemcitabine with regional hyperthermia in pancreatic cancer patients.

Characterization of small HSPs from Anemonia viridis reveals insights into molecular evolution of alpha crystallin genes among cnidarians

Gene family encoding small Heat-Shock Proteins (sHSPs containing α-crystallin domain) are found both in prokaryotic and eukaryotic organisms; however, there is limited knowledge of their evolution. In this study, two small HSP genes termed AvHSP28.6 and AvHSP27, both organized in one intron and two exons, were characterised in the Mediterranean snakelocks anemone Anemonia viridis. The release of the genome sequence of Hydra magnipapillata and Nematostella vectensis enabled a comprehensive study of the molecular evolution of α-crystallin gene family among cnidarians. Most of the H. magnipapillata sHSP genes share the same gene organization described for AvHSP28.6 and AvHSP27, differing from the sHSP genes of N. vectensis which mainly show an intronless architecture. The different genomic organization of sHSPs, the phylogenetic analyses based on protein sequences, and the relationships among Cnidarians, suggest that the A.viridis sHSPs represent the common ancestor from which H. magnipapillata genes directly evolved through segmental genome duplication. Additionally retroposition events may be considered responsible for the divergence of sHSP genes of N. vectensis from A. viridis. Analyses of transcriptional expression profile showed that AvHSP28.6 was constitutively expressed among different tissues from both ectodermal and endodermal layers of the adult sea anemones, under normal physiological conditions and also under different stress condition. Specifically, we profiled the transcriptional activation of AvHSP28.6 after challenges with different abiotic/biotic stresses showing induction by extreme temperatures, heavy metals exposure and immune stimulation. Conversely, no AvHSP27 transcript was detected in such dissected tissues, in adult whole body cDNA library or under stress conditions. Hence, the involvement of AvHSP28.6 gene in the sea anemone defensome is strongly suggested.

Characterization of human small heat shock protein HspB1 that carries C-terminal domain mutations associated with hereditary motor neuron diseases

Physico-chemical properties of four mutants (T164A, T180I, P182S and R188W) of human small heat shock protein HspB1 (Hsp27) associated with neurodegenerative diseases were analyzed by means of fluorescence spectroscopy, dynamic light scattering, size-exclusion chromatography and measurement of chaperone-like activity. Mutation T164A was accompanied by destabilization of the quaternary structure and decrease of thermal stability without any significant changes of chaperone-like activity. Mutations T180I and P182S are adjacent or within the conserved C-terminal motif IPI/V. Replacement T180⇒I leading to the formation of hydrophobic cluster consisting of three Ile produced small increase of thermal stability without changes of chaperone-like activity. Mutation P182S induced the formation of metastable large oligomers of HspB1 with apparent molecular weight of more than 1000kDa. Oligomers of P182S have very low thermal stability and undergo irreversible aggregation at low temperature. The P182S mutant forms mixed oligomers with the wild type HspB1 and the properties of these mixed oligomers are intermediate between those of the wild type HspB1 and its mutant. Mutation R188W did not significantly affect quaternary structure or thermal stability of HspB1, but was accompanied by a pronounced decrease of its chaperone-like activity. All mutations analyzed are associated with hereditary motor neuropathies or Charcot-Marie-Tooth disease type 2; however, molecular mechanisms underlying pathological effects are specific for each of these mutants.

Heat-shock protein 27 (HSP27, HSPB1) is up-regulated by MET kinase inhibitors and confers resistance to MET-targeted therapy

The tyrosine kinase encoded by the MET oncogene is activated by gene mutation or amplification in tumors, which in most instances maintain addiction, i.e., dependency, to MET activation. This makes MET an attractive candidate for targeted therapies. Here we show that, in 3/3 MET-addicted human gastric cancer cell lines, MET kinase inhibition resulted in a 3- to 4-fold increased expression of the antiapoptotic small heat-shock protein of 27 kDa (HSP27, HSPB1). HSP27 increase depended on the inhibition of the MEK/ERK pathway and on heat-shock factor 1 (HSF1) and hypoxia-inducible factor-1α (HIF-1α) regulation. Importantly, HSP27-silenced MET-addicted cells underwent 2- and 3-fold more apoptosis following MET inhibition in vitro and in vivo, respectively. Likewise, in human cancer cells susceptible to epidermal growth factor receptor (EGFR) inhibition, EGFR inhibitors induced HSP27 expression and were strengthened by HSP27 suppression. In control cell lines that were not affected by drugs targeting MET or EGFR, these drugs did not induce HSP27 increase. Therefore, in cancer therapies targeting the MET pathway, the induction of HSP27 might limit the efficacy of anti-MET agents. As HSP27 increase also impairs the effectiveness of EGFR inhibitors and is known to protect cells from chemotherapeutics, the induction of HSP27 by targeted agents might strongly affect the success of combination treatments.

A small heat shock protein is essential for thermotolerance and intracellular survival of Leishmania donovani

Leishmania parasites must survive and proliferate in two vastly different environments – the guts of poikilothermic sandflies and the antigen-presenting cells of homeothermic mammals. The change of temperature during the transmission from sandflies to mammals is both a key trigger for the progression of their life cycle and for elevated synthesis of heat shock proteins, which have been implicated in their survival at higher temperatures. Although the functions of the main heat shock protein families in the Leishmania life cycle have been studied, nothing is known about the roles played by small heat shock proteins. Here, we present the first evidence for the pivotal role played by the Leishmania donovani 23-kDa heat shock protein (which we called HSP23), which is expressed preferentially during the mammalian stage where it assumes a perinuclear localisation. Loss of HSP23 causes increased sensitivity to chemical stressors and renders L. donovani non-viable at 37°C. Consequently, HSP23-null mutants are non-infectious to primary macrophages in vitro. All phenotypic effects could be abrogated by the introduction of a functional HSP23 transgene into the null mutant, confirming the specificity of the mutant phenotype. Thus, HSP23 expression is a prerequisite for L. donovani survival at mammalian host temperatures and a crucial virulence factor.

alphaB-crystallin is a marker of aggressive breast cancer behavior but does not independently predict for patient outcome: a combined analysis of two randomized studies

BACKGROUND

alphaB-crystallin is a small heat shock protein that has recently been characterized as an oncoprotein correlating with the basal core phenotype and with negative prognostic factors in breast carcinomas. The purpose of this study was to evaluate alphaB-crystallin with respect to clinicopathological parameters and the outcome of patients with operable high-risk breast cancer.

METHODS

A total of 940 tumors were examined, derived from an equal number of patients who had participated in two randomized clinical trials (paclitaxel-containing regimen in 793 cases). Immunohistochemistry for ER, PgR, HER2, Ki67, CK5, CK14, CK17, EGFR, alphaB-crystallin, BRCA1 and p53 was performed. BRCA1 mutation data were available in 89 cases.

RESULTS

alphaβ-crystallin was expressed in 170 cases (18.1%) and more frequently in triple-negative breast carcinomas (TNBC) (45% vs. 14.5% non-TNBC, p < 0.001). alphaB-crystallin protein expression was significantly associated with high Ki67 (Pearson chi-square test, p < 0.001), p53 (p = 0.002) and basal cytokeratin protein expression (p < 0.001), BRCA1 mutations (p = 0.045) and negative ER (p < 0.001) and PgR (p < 0.001). Its overexpression, defined as >30% positive neoplastic cells, was associated with adverse overall survival (Wald's p = 0.046). However, alphaB-crystallin was not an independent prognostic factor upon multivariate analysis. No interaction between taxane-based therapy and aβ-crystallin expression was observed.

CONCLUSIONS

In operable high-risk breast cancer, alphaB-crystallin protein expression is associated with poor prognostic features indicating aggressive tumor behavior, but it does not seem to have an independent impact on patient survival or to interfere with taxane-based therapy.

TRIAL REGISTRATIONS

ACTRN12611000506998 (HE10/97 trial) and ACTRN12609001036202 (HE10/00 trial).

Microtubules and their role in cellular stress in cancer

Microtubules are highly dynamic structures, which consist of α- and β-tubulin heterodimers, and are involved in cell movement, intracellular trafficking, and mitosis. In the context of cancer, the tubulin family of proteins is recognized as the target of the tubulin-binding chemotherapeutics, which suppress the dynamics of the mitotic spindle to cause mitotic arrest and cell death. Importantly, changes in microtubule stability and the expression of different tubulin isotypes as well as altered post-translational modifications have been reported for a range of cancers. These changes have been correlated with poor prognosis and chemotherapy resistance in solid and hematological cancers. However, the mechanisms underlying these observations have remained poorly understood. Emerging evidence suggests that tubulins and microtubule-associated proteins may play a role in a range of cellular stress responses, thus conferring survival advantage to cancer cells. This review will focus on the importance of the microtubule-protein network in regulating critical cellular processes in response to stress. Understanding the role of microtubules in this context may offer novel therapeutic approaches for the treatment of cancer.

Toward the identification of a subset of unexplained infertility: a sperm proteomic approach

OBJECTIVE

To investigate the male gamete proteome and its relation to blastocyst development and reproductive success.

DESIGN

Experimental study.

SETTING

Research laboratory.

PATIENT(S)

Male infertility patients (n=12) with no known male factor infertility, donated motile sperm after intracytoplasmic sperm injection during an oocyte donor in vitro fertilization cycle.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Proteomic profiles of sperm from normozoospermic males.

RESULT(S)

Patients were grouped based on day-5 embryo development: group A=good blastocyst development (>35%≥grade 3 BB) and group B=poor blastocyst development (<15%≥grade 3 BB). No differences between the groups were observed for sperm concentration, motility, or Kruger morphology. The in vitro fertilization outcome was statistically significantly different with higher viable implantation rates observed for group A (A=80% vs. B=48%). Proteomic analysis of the motile sperm samples revealed 49 proteins with statistically significantly differential abundance in relation to blastocyst development (>1.5-fold). Twenty-nine proteins showed decreased abundance for group B, including several proteins involved in spermatogenesis, and 20 proteins showed increased abundance for group B, including several heat shock proteins.

CONCLUSION(S)

An altered sperm proteome was observed with respect to poor blastocyst development and in vitro fertilization outcome in donor oocyte cycles despite normal sperm testing parameters. These data could represent a novel subset of male factor infertility. Ongoing investigation into the male factor contribution to idiopathic infertility may result in improved patient care and enhanced outcomes.