The emerging role of HSP20 as a multifunctional protective agent

8-Br-cGMP activates HSPB6 and increases the antineoplastic activity of quinidine in prostate cancer

Heat shock protein family B [small] member 6 (HSPB6), widely found in various muscles, has been recently identified as a tumor suppressor gene. However, its role in prostate cancer remains unexplored. Herein, we investigated the expression of HSPB6 in prostate cancer and its association with prognosis. Our findings revealed that HSPB6 downregulation in prostate cancer correlated with a poor prognosis. Moreover, we discovered that HSPB6 can be phosphorylated and activated by 8-Br-cGMP, leading to apoptosis in prostate cancer cells by activating Cofilin. Additionally, we demonstrated that knocking down E2F1 by quinidine administration enhances the transcriptional level of HSPB6. Furthermore, we evaluated the combination of quinidine and 8-Br-cGMP as a potential therapeutic strategy for prostate cancer. Our results revealed that the combined treatment was more effective than either treatment alone in inhibiting the growth of prostate cancer through the HSPB6 pathway, both in vitro and in vivo. Overall, our study provides compelling evidence that HSPB6 suppresses malignant behavior in prostate cancer by inducing apoptosis. The combination of quinidine and 8-Br-cGMP emerges as a promising approach for the treatment of prostate cancer.

Cellular functions of heat shock protein 20 (HSPB6) in cancer: A review

Heat shock proteins (HSP) are a large family of peptide proteins that are widely found in cells. Studies have shown that the expression and function of HSPs in cells are very complex, and they can participate in cellular physiological and pathological processes through multiple pathways. Multiple heat shock proteins are associated with cancer cell growth, proliferation, metastasis, and resistance to anticancer drugs, and they play a key role in cancer development by ensuring the correct folding or degradation of proteins in cancer cells. As research hotspots, HSP90, HSP70 and HSP27 have been extensively studied in cancer so far. However, HSP20, also referred to as HSPB6, as a member of the small heat shock protein family, has been shown to play an important role in the cardiovascular system, but little research has been conducted on HSP20 in cancer. This review summarizes the current cellular functions of HSP20 in different cancer types, as well as its effects on cancer proliferation, progression, prognosis, and its other functions in cancer, to illustrate the close association between HSP20 and cancer. We show that, unlike most HSPs, HSP20 mainly plays an active anticancer role in cancer development, which is expected to provide new ideas and help for cancer diagnosis and treatment and research.

Update on new trend and progress of the mechanism of polysaccharides in the intervention of Alzheimer's disease, based on the new understanding of relevant theories: A review

Alzheimer's disease (AD), a neurodegenerative disease with insidious onset and progressive progression, is the main type of dementia. Currently, there is no specific cure for the disease. At the same time, a series of drug developments based on the classic theory, the Aβ cascade hypothesis, have not completed phase III clinical trials, challenging the hypothesis. Polysaccharides obtained from natural products can be used in the treatment of AD, which has attracted academic attention due to its advantages of multi-target, multi-channel, no or modest side effects. The TCM syndrome type of AD is mainly "qi and blood deficiency, kidney essence deficiency", and the medicine is mainly used to replenish qi and blood, kidney and bone marrow. Thus, there has been extensive and in-depth research on polysaccharides obtained from tonic Chinese herbal medicine in China. Based on this background, this paper evaluated the effects and mechanisms of natural polysaccharides on AD by combing and screening English and related literature in recent 5 years and summarized the extraction process and structure-activity relationship of polysaccharides.

A model for COVID-19-induced dysregulation of ACE2 shedding by ADAM17

The angiotensin Converting Enzyme 2 (ACE2) receptor is a key component of the renin-angiotensin-aldesterone system (RAAS) that mediates numerous effects in the cardiovascular system. It is also the cellular point of contact for the coronavirus spike protein. Cleavage of the receptor is both important to its physiological function as well as being necessary for cell entry by the virus. Shedding of ACE2 by the metalloprotease ADAM17 releases a catalytically active soluble form of ACE2, but cleavage by the serine protease TMPRSS2 is necessary for virion internalization. Complicating the issue is the observation that circulating ACE2 can also bind to the virus effectively blocking attachment to the membrane-bound receptor. This work investigates the possibility that the inflammatory response to coronavirus infection can abrogate shedding by ADAM17, thereby favoring cleavage by TMPRSS2 and thus cell entry by the virion.

Potential Roles of Muscle-Derived Extracellular Vesicles in Remodeling Cellular Microenvironment: Proposed Implications of the Exercise-Induced Myokine, Irisin

Extracellular vesicles (EVs) have emerged as key players of intercellular communication and mediate crosstalk between tissues. Metastatic tumors release tumorigenic EVs, capable of pre-conditioning distal sites for organotropic metastasis. Growing evidence identifies muscle cell-derived EVs and myokines as potent mediators of cellular differentiation, proliferation, and metabolism. Muscle-derived EVs cargo myokines and other biological modulators like microRNAs, cytokines, chemokines, and prostaglandins hence, are likely to modulate the remodeling of niches in vital sites, such as liver and adipose tissues. Despite the scarcity of evidence to support a direct relationship between muscle-EVs and cancer metastasis, their indirect attribution to the regulation of niche remodeling and the establishment of pre-metastatic homing niches can be put forward. This hypothesis is supported by the role of muscle-derived EVs in findings gathered from other pathologies like inflammation and metabolic disorders. In this review, we present and discuss studies that evidently support the potential roles of muscle-derived EVs in the events of niche pre-conditioning and remodeling of metastatic tumor microenvironment. We highlight the potential contributions of the integrin-mediated interactions with an emerging myokine, irisin, to the regulation of EV-driven microenvironment remodeling in tumor metastasis. Further research into muscle-derived EVs and myokines in cancer progression is imperative and may hold promising contributions to advance our knowledge in the pathophysiology, progression and therapeutic management of metastatic cancers.

Heat Shock Proteins in Oxidative Stress and Ischemia/Reperfusion Injury and Benefits from Physical Exercises: A Review to the Current Knowledge

Heat shock proteins (HSPs) are molecular chaperones produced in response to oxidative stress (OS). These proteins are involved in the folding of newly synthesized proteins and refolding of damaged or misfolded proteins. Recent studies have been focused on the regulatory role of HSPs in OS and ischemia/reperfusion injury (I/R) where reactive oxygen species (ROS) play a major role. ROS perform many functions, including cell signaling. Unfortunately, they are also the cause of pathological processes leading to various diseases. Biological pathways such as p38 MAPK, HSP70 and Akt/GSK-3β/eNOS, HSP70, JAK2/STAT3 or PI3K/Akt/HSP70, and HSF1/Nrf2-Keap1 are considered in the relationship between HSP and OS. New pathophysiological mechanisms involving ROS are being discovered and described the protein network of HSP interactions. Understanding of the mechanisms involved, e.g., in I/R, is important to the development of treatment methods. HSPs are multifunctional proteins because they closely interact with the antioxidant and the nitric oxide generation systems, such as HSP70/HSP90/NOS. A deficiency or excess of antioxidants modulates the activation of HSF and subsequent HSP biosynthesis. It is well known that HSPs are involved in the regulation of several redox processes and play an important role in protein-protein interactions. The latest research focuses on determining the role of HSPs in OS, their antioxidant activity, and the possibility of using HSPs in the treatment of I/R consequences. Physical exercises are important in patients with cardiovascular diseases, as they affect the expression of HSPs and the development of OS.

Neuroprotective Effects of 2-Substituted 1, 3-Selenazole Amide Derivatives on Amyloid-Beta-Induced Toxicity in a Transgenic Caenorhabditis Elegans Model of Alzheimer's Disease

Alzheimer's disease is an age-related neurodegenerative disease, associated with the presence of extracellular amyloid-β (Aβ) plaques and neurofibrillary tangles. Although the pathogenesis of AD remains unclear, the characteristic feature of AD was reported to be the buildup of Aβ plaques. In this study, we extensively investigated the neuroprotective effects of 2-substituted 1,3-selenazole amide derivatives (CHF11) on Aβ1-42 transgenic Caenorhabditis elegans CL4176. Results showed that worms fed with CHF11 exhibited remarkably reduced paralysis, decreased levels of toxic Aβ oligomers and Aβ plaque deposition, as well as less ROS production in comparison with the untreated worms. The effective concentrations of CHF11 were arranged in the descending order of 100 µM > 10 µM > 1 µM. Real-time PCR analysis showed that there was no significant difference in Aβ expression between CHF11-administered group and the blank control group, suggesting that CHF11-induced reduction in toxic protein deposition may be regulated at the post-transcriptional level. In the meantime, the gene expressions of hsf-1 and its downstream target hsp-12.6 were significantly increased, indicating that CHF11 against Aβ toxicity may involve in HSF-1 signaling pathway in worms. In conclusion, CHF11 exhibits a significant protective effect against β-amyloid-induced toxicity in CL4176 by reducing β-amyloid aggregation and ROS production, which may involve in HSF-1 and downstream target HSP-12.6 pathway.

Inducible expression of heat shock protein 20 protects airway epithelial cells against oxidative injury involving the Nrf2-NQO-1 pathway

BACKGROUND

Heat shock protein (HSP) 20 is a molecular chaperone that exerts multiple protective functions in various kinds of tissues. However, the expression of HSP20 and its specific functions in airway epithelial cells (AECs) remain elusive.

RESULTS

In current study, we first confirmed the inducible expression of HSP20 in mouse AECs and in a human bronchial epithelial cell line BEAS-2B cells, under different oxidant stressors. Then by establishing a HSP20-abundant mouse model with repeated low-level-ozone exposures and stimulating this model with a single high-level ozone exposure, we found that the HSP20 abundance along with its enhanced phosphorylation potentially contributed to the alleviation of oxidative injuries, evidenced by the decreases in the bodyweight reduction, the BAL neutrophil accumulation, the AECs shedding, and the BAL concentrations of albumin and E-cadherin. The biological function of HSP20 and its molecular mechanisms were further investigated in BEAS-2B cells that were transfected with HSP20-, unphosphorylatable HSP20(Ala) or empty vector plasmids prior to the stimulation of H2O2, of which its oxidant capacity has been proved to be similar with those of ozone in an air-liquid culture system. We found that the H2O2-induced intracellular ROS level and the early cell apoptosis were attenuated in the HSP20- but not HSP20(Ala)- transfected cells. The intracellular expression of NQO-1 (mRNA and protein) and the intranuclear content of Nrf2 were significantly increased in the HSP20- transfected cells but not in the HSP20(Ala)- and empty vector-transfected cells after the stimulation of H2O2.

CONCLUSIONS

The inducible expression of HSP20 in AECs by oxidative stress exerts protective roles against oxidative damages, which may involve the activation of the Nrf2-NQO-1 pathway.

Características comunes de las chaperonas pequeñas y diméricas

Las chaperonas moleculares constituyen un mecanismo importante para evitar la muerte celular provocada por la agregación de proteínas. Las chaperonas independientes del ATP son un grupo de proteínas de bajo peso molecular que pueden proteger y ayudar a alcanzar la estructura nativa de las proteínas desplegadas o mal plegadas sin necesidad de un gasto energético. Hemos encontrado que el dominio C-terminal de las catalasas de subunidad grande tiene actividad de chaperona. Por ello, en esta revisión analizamos las características más comunes de las chaperonas pequeñas y más estudiadas como: αB-cristalina, Hsp20, Spy, Hsp33 y Hsp31. En particular, se examina la participación de los aminoácidos hidrofóbicos y de los aminoácidos con carga en el reconocimiento de las proteínas sustrato, así como el papel que tiene la forma dimérica y su oligomerización en la actividad de chaperona. En cada una de esas chaperonas revisaremos la estructura de la proteína, su función, localización celular e importancia para la célula.

Analysis of gene expression profiling of amyloidogenic immunoglobulin light-chains on cultured rat cardiomyocytes

The present study aimed to investigate the toxic effects of different amyloidogenic light-chains (LCs) on cardiomyocytes, and demonstrate the differentially expressed genes (DEGs) and signaling pathways that participate in this process. Cultured cardiomyocytes were treated with recombinant κ LC peptide (AL-09) or with serum from a patient diagnosed with multiple myeloma (λ LC) with cardiac involvement. The 6xHis peptide or serum from healthy patients was used as peptide control or serum control, respectively. Cell viability was determined using CCK-8 assay and apoptosis was analyzed by flow cytometry. The DEGs were detected by RNA sequencing (RNA-Seq), followed by Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses. Changes in gene expression levels were confirmed by reverse transcription-quantitative PCR. The cell viability in the AL-09 peptide-treated (0.2 mg/ml) and patient serum-treated (1:10 dilution) cardiomyocytes decreased to 42 and -72% of the corresponding control groups. The extent of cell apoptosis increased in AL-09-treated cardiomyocytes compared with the control group. RNA-Seq showed 256 DEGs co-existed in the two paired groups, including 127 upregulated and 88 downregulated genes. The KEGG pathways for upregulated expressed genes included the ‘TGF-β signaling pathway’, the ‘Hedgehog signaling pathway’, the ‘ErbB signaling pathway’ and ‘lysine degradation’. The higher mRNA expression of bone morphogenetic protein (Bmp) 4, Bmp6, prostaglandin G/H synthase (Ptgs)1, Ptgs2, epiregulin, Tgfa and procollagen-lysine,2-oxoglutarate 5-dioxygenase 2 were confirmed. The KEGG pathways of downregulated expressed genes included genes involved with the ‘p53 signaling pathway’ and the ‘cell cycle’. The mRNA expression levels of E3 ubiquitin-protein ligase CCNB1IP1 showed significant downregulation in the AL-09 peptide group compared with those in the 6xHis peptide group. In conclusion, cardiomyocytes treated with amyloidogenic λ and κ LCs presented with decreased cell viability compared with controls. Cell apoptosis increased in κ LC-treated cells compared with controls. The gene expression profiles associated with transforming growth factor-β-bone morphogenetic protein, the receptor tyrosine-protein kinase erbB-2 signaling pathways, prostaglandins, collagen production, the p53 signaling pathway and the cell cycle were altered in light-chain-treated cardiomyocytes.

Physico-chemical properties of two point mutants of small heat shock protein HspB6 (Hsp20) with abrogated cardioprotection

Physico-chemical properties of HspB6 S10F and P20L mutants with abrogated cardioprotective activity and associated with different forms of cardiomyopathy were analyzed. Under normal conditions both the wild-type HspB6 and its mutants formed small size oligomers (dimers) with apparent molecular weight of 50-60 kDa. Under crowding conditions (0.5 M trimethylamine N-oxide, TMAO) the wild-type HspB6 remained predominantly dimeric or formed small molecular weight complexes, whereas both mutants tended to form high molecular weight complexes. Catalytic subunit of cAMP-dependent protein kinase phosphorylated the wild-type HspB6 and its S10F mutant with comparable rate. The rate of P20L mutant phosphorylation was higher than that of the wild-type HspB6. S10F and P20L mutations did not affect interaction of phosphorylated HspB6 with universal adapter proteins 14-3-3. The wild-type HspB6 was resistant to heat-induced denaturation and aggregation, whereas both its mutants were denatured and started to aggregate at temperature much lower than its wild-type counterpart. Titration with fluorescent probe bis-ANS was accompanied by larger increase of fluorescence in the case of both mutants than in the case of the wild-type HspB6. Both mutants possessed higher chaperone-like activity than the wild-type protein. It is concluded that both S10F and P20L mutations are accompanied by increase of hydrophobicity of the very N-terminal region of HspB6 leading to increased aggregation at elevated temperature, formation of large complexes under crowding conditions and increased chaperone-like activity measured in vitro. Increased hydrophobicity and self-association can affect substrate specificity and interaction with certain target proteins thus leading to decrease or complete abrogation of cardioprotective activity.

Reshaping cAMP nanodomains through targeted disruption of compartmentalised phosphodiesterase signalosomes

Spatio-temporal regulation of localised cAMP nanodomains is highly dependent upon the compartmentalised activity of phosphodiesterase (PDE) cyclic nucleotide degrading enzymes. Strategically positioned PDE-protein complexes are pivotal to the homeostatic control of cAMP-effector protein activity that in turn orchestrate a wide range of cellular signalling cascades in a variety of cells and tissue types. Unsurprisingly, dysregulated PDE activity is central to the pathophysiology of many diseases warranting the need for effective therapies that target PDEs selectively. This short review focuses on the importance of activating compartmentalised cAMP signalling by displacing the PDE component of signalling complexes using cell-permeable peptide disrupters.

Exercise Rehabilitation Attenuates Cognitive Deficits in Rats with Traumatic Brain Injury by Stimulating the Cerebral HSP20/BDNF/TrkB Signalling Axis

Physical exercise (PE) is an effective method for improving cognitive function among patients with traumatic brain injury (TBI). We previously demonstrated that PE with an infrared-sensing running wheel (ISRW) system provides strong neuroprotection in an experimental animal model of stroke. In this study, we used fluid percussion injury in rats to simulate mild TBI. For rats, we used both passive avoidance learning and the Y-maze tests to evaluate cognitive function. We investigated whether PE rehabilitation attenuated cognitive deficits in rats with TBI and determined the contribution of hippocampal and cortical expression of heat shock protein 20 (HSP20) to PE-mediated cognitive recovery. In addition to increasing hippocampal and cortical expression of HSP20, brain-derived neurotrophic factor (BDNF), and the tropomyosin receptor kinase B (TrkB) ratio, PE rehabilitation significantly attenuated brain contusion and improved cognitive deficits in the rat model. Furthermore, reducing hippocampal and cortical expression of HSP20 with an intracerebral injection of pSUPER hsp20 small interfering RNA significantly diminished the PE-induced overexpression of hippocampal and cortical BDNF and the TrkB ratio and also reversed the beneficial effect of PE in reducing neurotrauma and the cognitive deficits. A positive Pearson correlation was found between HSP20 and BDNF, as well as between HSP20 and TrkB, in the hippocampal and cortical tissues. We thus conclude that post-ischaemic ISRW exercise rehabilitation attenuates cognitive deficits, as well as brain contusions, in TBI rats by stimulating the cerebral HSP20/BDNF/TrkB signalling axis.

Redox Aspects of Chaperones in Cardiac Function

Molecular chaperones are stress proteins that allow the correct folding or unfolding as well as the assembly or disassembly of macromolecular cellular components. Changes in expression and post-translational modifications of chaperones have been linked to a number of age- and stress-related diseases including cancer, neurodegeneration, and cardiovascular diseases. Redox sensible post-translational modifications, such as S-nitrosylation, glutathionylation and phosphorylation of chaperone proteins have been reported. Redox-dependent regulation of chaperones is likely to be a phenomenon involved in metabolic processes and may represent an adaptive response to several stress conditions, especially within mitochondria, where it impacts cellular bioenergetics. These post-translational modifications might underlie the mechanisms leading to cardioprotection by conditioning maneuvers as well as to ischemia/reperfusion injury. In this review, we discuss this topic and focus on two important aspects of redox-regulated chaperones, namely redox regulation of mitochondrial chaperone function and cardiac protection against ischemia/reperfusion injury.

Alteration of heat shock protein 20 expression in preeclamptic patients and its effect in vascular and coagulation function

Preeclampsia (PE) is a pregnancy-specific, multi-system disorder and the leading cause of maternal and perinatal morbidity and mortality in obstetrics worldwide. Excessive vasoconstriction and dysregulated coagulation function are closely associated with PE. Heat shock protein 20 (HSP20) is ubiquitously expressed under normal physiological conditions and has important roles in vascular dilatation and suppression of platelet aggregation. However, the role of HSP20 in the pathogenesis of PE remains unclear. In this study, we collected chorionic plate resistance arteries (CPAs) and serum from 118 healthy pregnant women and 80 women with PE and detected the levels of HSP20 and its phosphorylated form. Both HSP20 and phosphorylated HSP20 were downregulated in CPAs from women with PE. Comparison of the vasodilative ability of CPAs from the two groups showed impaired relaxation responses to acetyl choline in preeclamptic vessels. In addition to the reduced HSP20 in serum from women with PE, the platelet distribution width and mean platelet volume were also decreased, and the activated partial thromboplastin time and thromboplastin time were elevated.With regard to the vital roles of HSP20 in mediating vasorelaxation and coagulation function, the decreased HSP20 might contribute to the pathogenesis of PE.

EphrinA1-Fc attenuates myocardial ischemia/reperfusion injury in mice

EphrinA1, a membrane-bound receptor tyrosine kinase ligand expressed in healthy cardiomyocytes, is lost in injured cells following myocardial infarction. Previously, we have reported that a single intramyocardial injection of chimeric ephrinA1-Fc at the time of ischemia reduced injury in the nonreperfused myocardium by 50% at 4 days post-MI by reducing apoptosis and inflammatory cell infiltration. In a clinically relevant model of acute ischemia (30min)/reperfusion (24hr or 4 days) injury, we now demonstrate that ephrinA1-Fc reduces infarct size by 46% and completely preserves cardiac function (ejection fraction, fractional shortening, and chamber dimensions) in the short-term (24hrs post-MI) as well as long-term (4 days). At 24 hours post-MI, diminished serum inflammatory cell chemoattractants in ephrinA1-Fc-treated mice reduces recruitment of neutrophils and leukocytes into the myocardium. Differences in relative expression levels of EphA-Rs are described in the context of their putative role in mediating cardioprotection. Validation by Western blotting of selected targets from mass spectrometry analyses of pooled samples of left ventricular tissue homogenates from mice that underwent 30min ischemia and 24hr of reperfusion (I/R) indicates that ephrinA1-Fc administration alters several regulators of signaling pathways that attenuate apoptosis, promote autophagy, and shift from FA metabolism in favor of increased glycolysis to optimize anaerobic ATP production. Taken together, reduced injury is due a combination of adaptive metabolic reprogramming, improved cell survival, and decreased inflammatory cell recruitment, suggesting that ephrinA1-Fc enhances the capacity of the heart to withstand an ischemic insult.

Dianxianning improved amyloid β-induced pathological characteristics partially through DAF-2/DAF-16 insulin like pathway in transgenic C. elegans

Dianxianning (DXN) is a traditional Chinese formula, and has been approved in China for treating epilepsy since 1996. Here anti-Alzheimer's disease activity of DXN has been reported. DXN improved AD-like symptoms of paralysis and 5-HT sensitivity of transgenic Aβ1-42 C. elegans. In worms, DXN significantly increased Aβ monomers and decreased the toxic Aβ oligomers, thus reducing Aβ toxicity. DXN significantly suppressed the expression of hsp-16.2 induced by juglone, and up-regulated sod-3 expression. These results indicated that DXN increased stress resistance and protected C. elegans against oxidative stress. Furthermore, DXN could significantly promote DAF-16 nuclear translocation, but it did not activate SKN-1. The inhibitory effect of DXN on the Aβ toxicity was significantly reverted by daf-16 RNAi, rather than skn-1 RNAi or hsf-1 RNAi. These results indicated that DAF-16 is at least partially required for the anti-AD effect of DXN. In conclusion, DXN improved Aβ-induced pathological characteristics partially through DAF-2/DAF-16 insulin like pathway in transgenic worms. Together with our data obtained by Morris water maze test, the results showed that DXN markedly ameliorated cognitive performance impairment induced by scopolamine in mice. All the results support that DXN is a potential drug candidate to treat Alzheimer's diseases.

Small heat shock proteins in ageing and age-related diseases

Small heat shock proteins (sHSPs) are gatekeepers of cellular homeostasis across species, preserving proteome integrity under stressful conditions. Nonetheless, recent evidence suggests that sHSPs are more than molecular chaperones with merely auxiliary role. In contrast, sHSPs have emerged as central lifespan determinants, and their malfunction has been associated with the manifestation of neurological disorders, cardiovascular disease and cancer malignancies. In this review, we focus on the role of sHSPs in ageing and age-associated diseases and highlight the most prominent paradigms, where impairment of sHSP function has been implicated in human pathology.

Selective inhibition of phosphodiesterases 4, 5 and 9 induces HSP20 phosphorylation and attenuates amyloid beta 1-42-mediated cytotoxicity

Phosphodiesterase (PDE) inhibitors are currently under evaluation as agents that may facilitate the improvement of cognitive impairment associated with Alzheimer's disease. Our aim was to determine whether inhibitors of PDEs 4, 5 and 9 could alleviate the cytotoxic effects of amyloid beta 1–42 (Aβ_1–42) via a mechanism involving the small heatshock protein HSP20. We show that inhibition of PDEs 4, 5 and 9 but not 3 induces the phosphorylation of HSP20 which, in turn, increases the colocalisation between the chaperone and Aβ_1–42 to significantly decrease the toxic effect of the peptide. We conclude that inhibition of PDE9 is most effective to combat Aβ_1–42 cytotoxicity in our cell model.

A novel small heat shock protein of Haliotis discus hannai: characterization, structure modeling, and expression profiles under environmental stresses

Small heat shock proteins (sHsps) are a class of chaperones with low molecular weight, feathered by a C-terminal α-crystallin domain (ACD). They participate in reestablishing the stability of partially denatured proteins and therefore contribute to cellular homeostasis. In this work, we identified a sHsp homolog (designated as sHsp19) from Haliotis discus hannai, an economically important farmed mollusk in East Asia. sHsp19 possesses a sHsp hallmark domain, which exhibits the typical fold of ACD as revealed by a three-dimensional model constructed through an iterative threading assembly refinement method. The amino acid sequence sHsp19 shares low identities with any other known sHsps, with percentages below 35 %. Besides, sHsp19 shows relatively distant phylogenetic relationships with sHsps of various mollusks, including two other identified sHsps of abalone subspecies. qRT-PCR analysis indicated that the expression of sHsp19 occurred in multiple tissues. Upon exposure to thermal, oxidative, and multiple toxic metal stresses, the level of sHsp19 mRNA was rapidly elevated in a persistent fashion, with the maximum increase up to 170.58-, 405.84-, and 361.96-fold, respectively. These results indicate sHsp is a novel sHsp that possesses the distinguishing structural feature of sHsps but has remote homologies with known sHsps. It is likely to be important in stress adaptation of abalone and may be applied as a bioindicator for monitoring pollution or detrimental changes of environment in abalone culture.

Expression and localization of the Xenopus laevis small heat shock protein, HSPB6 (HSP20), in A6 kidney epithelial cells

Small heat shock proteins (sHSPs) are molecular chaperones that bind to unfolded protein, inhibit the formation of toxic aggregates and facilitate their refolding and/or degradation. Previously, the only sHSPs that have been studied in detail in the model frog system, Xenopus laevis, were members of the HSP30 family and HSPB1 (HSP27). We now report the analysis of X. laevis HSPB6, an ortholog of mammalian HSPB6. X. laevis HSPB6 cDNA encodes a 168 aa protein that contains an α-crystallin domain, a polar C-terminal extension and some possible phosphorylation sites. X. laevis HSPB6 shares 94% identity with a X. tropicalis HSPB6, 65% with turtle, 59% with humans, 49% with zebrafish and only 50% and 43% with X. laevis HSPB1 and HSP30C, respectively. Phylogenetic analysis revealed that X. laevis HSPB6 grouped more closely with mammalian and reptilian HSPB6s than with fish HSPB6. X. laevis recombinant HSPB6 displayed molecular chaperone properties since it had the ability to inhibit heat-induced aggregation of citrate synthase. Immunoblot analysis determined that HSPB6 was present constitutively in kidney epithelial cells and that heat shock treatment did not upregulate HSPB6 levels. While treatment with the proteasomal inhibitor, MG132, resulted in a 2-fold increase in HSPB6 levels, exposure to cadmium chloride produced a slight increase in HSPB6. These findings were in contrast to HSP70, which was enhanced in response to all three stressors. Finally, immunocytochemical analysis revealed that HSPB6 was present in the cytoplasm in the perinuclear region with some in the nucleus.

Phosphorylated Heat Shock Protein 20 (HSPB6) Regulates Transforming Growth Factor-α-Induced Migration and Invasion of Hepatocellular Carcinoma Cells

Human hepatocellular carcinoma (HCC) is one of the major malignancies in the world. Small heat shock proteins (HSPs) are reported to play an important role in the regulation of a variety of cancer cell functions, and the functions of small HSPs are regulated by post-translational modifications such as phosphorylation. We previously reported that protein levels of a small HSP, HSP20 (HSPB6), decrease in vascular invasion positive HCC compared with those in the negative vascular invasion. Therefore, in the present study, we investigated whether HSP20 is implicated in HCC cell migration and the invasion using human HCC-derived HuH7 cells. The transforming growth factor (TGF)-α-induced migration and invasion were suppressed in the wild-type-HSP20 overexpressed cells in which phosphorylated HSP20 was detected. Phospho-mimic-HSP20 overexpression reduced the migration and invasion compared with unphosphorylated HSP20 overexpression. Dibutyryl cAMP, which enhanced the phosphorylation of wild-type-HSP20, significantly reduced the TGF-α-induced cell migration of wild-type HSP20 overexpressed cells. The TGF-α-induced cell migration was inhibited by SP600125, a c-Jun N-terminal kinases (JNK) inhibitor. In phospho-mimic-HSP20 overexpressed HuH7 cells, TGF-α-stimulated JNK phosphorylation was suppressed compared with the unphosphorylated HSP20 overexpressed cells. Moreover, the level of phospho-HSP20 protein in human HCC tissues was significantly correlated with tumor invasion. Taken together, our findings strongly suggest that phosphorylated HSP20 inhibits TGF-α-induced HCC cell migration and invasion via suppression of the JNK signaling pathway.

Heat shock protein 20 (HSP20) is a novel substrate for protein kinase D1 (PKD1)

Heat shock protein 20 (HSP20) has cardioprotective qualities, which are triggered by PKA phosphorylation. PKD1 is also a binding partner for HSP20, and this prompted us to investigate whether the chaperone was a substrate for PKD1. We delineate the PKD1 binding sites on HSP20 and show for the first time HSP20 is a substrate for PKD1. Phosphorylation of HSP20 by PKD1 is diminished by pharmacological or siRNA reduction of PKD1 activity and is enhanced following PKD1 activation. Our results suggest that both PKA and PKD1 can both phosphorylate HSP20 on serine 16 but that PKA is the most dominant.

Targeting protein-protein interactions in complexes organized by A kinase anchoring proteins

Cyclic AMP is a ubiquitous intracellular second messenger involved in the regulation of a wide variety of cellular processes, a majority of which act through the cAMP – protein kinase A (PKA) signaling pathway and involve PKA phosphorylation of specific substrates. PKA phosphorylation events are typically spatially restricted and temporally well controlled. A-kinase anchoring proteins (AKAPs) directly bind PKA and recruit it to specific subcellular loci targeting the kinase activity toward particular substrates, and thereby provide discrete spatiotemporal control of downstream phosphorylation events. AKAPs also scaffold other signaling molecules into multi-protein complexes that function as crossroads between different signaling pathways. Targeting AKAP coordinated protein complexes with high-affinity peptidomimetics or small molecules to tease apart distinct protein–protein interactions (PPIs) therefore offers important means to disrupt binding of specific components of the complex to better understand the molecular mechanisms involved in the function of individual signalosomes and their pathophysiological role. Furthermore, development of novel classes of small molecules involved in displacement of AKAP-bound signal molecules is now emerging. Here, we will focus on mechanisms for targeting PPI, disruptors that modulate downstream cAMP signaling and their role, especially in the heart.

Decreased expression of heat shock protein 20 in colorectal cancer and its implication in tumorigenesis

Heat shock protein 20 (HSP20), which is a member of the small heat shock protein family, is known to participate in many pathological processes, such as asthma, intimal hyperplasia, and insulin resistance. However, the function of HSP20 in cancer development is not yet fully understood. In this study, we identified HSP20 as a down-regulated protein in 20 resected colorectal cancer (CRC) specimens compared with their paired normal tissues. Because HSP20 proteins were barely detectable in HCT-116 cells (a human colorectal cancer cell line), recombinant adenovirus encoding HSP20 (Ad-HSP20) was used to induce HSP20 overexpression in HCT-116 cells. Infection of Ad-HSP20, but not control adenovirus (Ad-GFP), reduced viability, and induced massive apoptosis in a time-dependent manner. The forced expression of HSP20 enhanced caspase-3/7 activity and down-regulated the anti-apoptotic Bcl-xL and Bcl-2 mRNA and protein levels. In addition, immunohistochemical analysis of 94 CRC specimens for HSP20 protein showed that reduced HSP20 expression was related to advanced TNM stage, lymph node metastasis, and tumor recurrence. Our study shows, for the first time, that expression of the HSP20 protein has a pro-death role in colorectal cancer cells. Therefore, HSP20 may have value as a prognostic tumor marker and its overexpression might be a novel strategy for CRC therapy.

Hsp20 Protects against Oxygen-Glucose Deprivation/Reperfusion-Induced Golgi Fragmentation and Apoptosis through Fas/FasL Pathway

Cerebral ischemia-reperfusion injury plays an important role in the development of tissue injury after acute ischemic stroke. Finding effective neuroprotective agents has become a priority in the treatment of ischemic stroke. The Golgi apparatus (GA) is a pivotal organelle and its protection is an attractive target in the treatment of cerebral ischemia-reperfusion injury. Protective effects of Hsp20, a potential cytoprotective agent due to its chaperone-like activity and involvement in regulation of many vital processes, on GA were assessed in an ischemia-reperfusion injury model. Mouse neuroblastoma Neuro2a (N2a) cells were subjected to oxygen-glucose deprivation/reperfusion (OGDR) insult. OGDR induces Golgi fragmentation, apoptosis, and p115 cleavage in N2a cells. However, transfection with Hsp20 significantly attenuates OGDR-induced Golgi fragmentation and apoptosis. Hsp20 interacts with Bax, decreases FasL and Bax expression, and inhibits caspases 3 and p115 cleavage in N2a cells exposed to OGDR. Our data demonstrate that increased Hsp20 expression protects against OGDR-induced Golgi fragmentation and apoptosis, likely through interaction with Bax and subsequent amelioration of the OGDR-induced elevation in p115 cleavage via the Fas/FasL signaling pathway. This neuroprotective potential of Hsp20 against OGDR insult and the underlying mechanism will pave the way for its potential clinical application for cerebral ischemia-reperfusion related disorders.

The cardioprotective role of small heat-shock protein 20

The small HSP (heat-shock protein) HSP20 is a molecular chaperone that is transiently up-regulated in response to cellular stress/damage. Although ubiquitously expressed in various tissues, it is most highly expressed in skeletal, cardiac and smooth muscle. Phosphorylation at Ser16 by PKA (cAMP-dependent protein kinase) is essential for HSP20 to confer its protective qualities. HSP20 and its phosphorylation have been implicated in a variety of pathophysiological processes, but most prominently cardiovascular disease. A wealth of knowledge of the importance of HSP20 in contractile function and cardioprotection has been gained over the last decade. The present mini-review highlights more recent findings illustrating the cardioprotective properties of HSP20 and its potential as a therapeutic agent.

Chronic nicotine treatment enhances vascular smooth muscle relaxation in rats

AIM

To investigate the effect of chronic nicotine treatment on vascular function and to identify the underlying mechanisms.

METHODS

Adult rats were treated with nicotine (3 mg·kg(-1)·d(-1), sc) for 6 weeks. After the rats were sacrificed, aortic rings were prepared for detecting vascular reactivity, and thoracic aorta and periaortic fat samples were collected for histological and molecular biology studies.

RESULTS

Chronic nicotine treatment significantly reduced periaortic fat, and specifically enhanced smooth muscle relaxation without altering the aortic adventitial fat and endothelium function. Pretreatment with the soluble guanylyl cyclase inhibitor ODQ (3 μmol/L) or PKG inhibitor Rp-8-Br-PET-cGMP (30 μmol/L) abolished the nicotine-induced enhancement of smooth muscle relaxation, whereas the cGMP analogue 8-Br-cGMP could mimic the nicotine-induced enhancement of smooth muscle relaxation. However, the chronic nicotine treatment did not alter PKG protein expression and activity in aortic media.

CONCLUSION

Chronic nicotine treatment enhances vascular smooth muscle relaxation of rats via activation of PKG pathway.

Targeted disruption of the heat shock protein 20-phosphodiesterase 4D (PDE4D) interaction protects against pathological cardiac remodelling in a mouse model of hypertrophy

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A peptide was discovered that disrupts HSP20–phosphodiesterase 4D (PDE4D) complex formation.

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HSP20–PDE4D complex disruption reversed hypertrophic-induced changes in electrical signalling in human cardiac myocytes.

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HSP20–PDE4D complex disruption attenuated the physiological response to pressure/volume overload.

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This physiological response normally results in an increase in cardiac myocyte size.

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Cardiac fibrosis was reduced in mice following treatment with the HSP20–PDE4D disruptor peptide.

Phosphorylated heat shock protein 20 (HSP20) is cardioprotective. Using human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) and a mouse model of pressure overload mediated hypertrophy, we show that peptide disruption of the HSP20–phosphodiesterase 4D (PDE4D) complex results in attenuation of action potential prolongation and protection against adverse cardiac remodelling. The later was evidenced by improved contractility, decreased heart weight to body weight ratio, and reduced interstitial and perivascular fibrosis. This study demonstrates that disruption of the specific HSP20–PDE4D interaction leads to attenuation of pathological cardiac remodelling.

Heat shock protein 20 (HSPB6) regulates TNF-α-induced intracellular signaling pathway in human hepatocellular carcinoma cells

We previously demonstrated that the expression of HSP20, a small heat shock protein, is inversely correlated with the progression of HCC. Inflammation is associated with HCC, and numerous cytokines, including TNF-α, act as key mediators in the progression of HCC. In the present study, we investigated whether HSP20 is implicated in the TNF-α-stimulated intracellular signaling in HCC using human HCC-derived HuH7 cells in the presence of TNF-α. In HSP20-overexpressing HCC cells, the cell growth was retarded compared with that in the control cells under long-term exposure of TNF-α. Because NF-κB pathway is the main intracellular signaling system activated by TNF-α, we investigated the effects of HSP20-overexpression of this pathway. The protein levels of IKK-α, but not IKK-β, in the HSP20-overexpressing cells were decreased. Short-term exposure to TNF-α-induced phosphorylation and degradation of IκB, and the phosphorylation and transactivational activity of NF-κB were suppressed in the HSP20-overexpressing HCC cells. Furthermore, the increase in IKK-α levels was accompanied by a decrease in the HSP20 levels in human HCC tissues. These findings strongly suggest that HSP20 might decrease the IKK-α protein level and that it down-regulates the TNF-α-stimulated intracellular signaling in HCC, thus resulting in the suppression of HCC progression.

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.

Early and late response of Nematostella vectensis transcriptome to heavy metals

Environmental contamination from heavy metals poses a global concern for the marine environment, as heavy metals are passed up the food chain and persist in the environment long after the pollution source is contained. Cnidarians play an important role in shaping marine ecosystems, but environmental pollution profoundly affects their vitality. Among the cnidarians, the sea anemone Nematostella vectensis is an advantageous model for addressing questions in molecular ecology and toxicology as it tolerates extreme environments and its genome has been published. Here, we employed a transcriptome-wide RNA-Seq approach to analyse N. vectensis molecular defence mechanisms against four heavy metals: Hg, Cu, Cd and Zn. Altogether, more than 4800 transcripts showed significant changes in gene expression. Hg had the greatest impact on up-regulating transcripts, followed by Cu, Zn and Cd. We identified, for the first time in Cnidaria, co-up-regulation of immediate-early transcription factors such as Egr1, AP1 and NF-κB. Time-course analysis of these genes revealed their early expression as rapidly as one hour after exposure to heavy metals, suggesting that they may complement or substitute for the roles of the metal-mediating Mtf1 transcription factor. We further characterized the regulation of a large array of stress-response gene families, including Hsp, ABC, CYP members and phytochelatin synthase, that may regulate synthesis of the metal-binding phytochelatins instead of the metallothioneins that are absent from Cnidaria genome. This study provides mechanistic insight into heavy metal toxicity in N. vectensis and sheds light on ancestral stress adaptations.

Regulation of active DNA demethylation by an α-crystallin domain protein in Arabidopsis

DNA methylation patterns are dynamically controlled by DNA methylation and active DNA demethylation, but the mechanisms of regulation of active DNA demethylation are not well understood. Through forward genetic screens for Arabidopsis mutants showing DNA hypermethylation at specific loci and increased silencing of reporter genes, we identified IDM2 (increased DNA methylation 2) as a regulator of DNA demethylation and gene silencing. IDM2 dysfunction causes DNA hypermethylation and silencing of reporter genes and some endogenous genes. These effects of idm2 mutations are similar to those of mutations in IDM1, a regulator of active DNA demethylation. IDM2 encodes an α-crystallin domain protein in the nucleus. IDM2 and IDM1 interact physically and partially colocalize at discrete subnuclear foci. IDM2 is required for the full activity of H3K18 acetylation but not H3K23 acetylation of IDM1 in planta. Our results suggest that IDM2 functions in active DNA demethylation and in antisilencing by regulating IDM1.

The JAK-STAT pathway in hypertrophic stress signaling and genomic stress response

The JAK-STAT signaling pathway plays a central role in transducing stress and growth signals in the hypertrophic heart. Unlike most signal transducers, JAKs and STATs signal in a number of different ways, both within the JAK-STAT pathway and in collaboration with other signaling pathways. In this review, we discuss how IL-6 activates cells lacking IL-6 receptors through trans-signaling and examine JAK-STAT pathway interaction with GPCR-linked pathways both within and between cells. Finally, we discuss recent studies showing how the JAK-STAT pathway can intersect with a general transcriptional regulatory mechanism to effect transcription of STAT-dependent stress response genes.

Synergism of cytotoxicity effects of triptolide and artesunate combination treatment in pancreatic cancer cell lines

BACKGROUND

Triptolide, extracted from the herb Tripteryglum wilfordii Hook.f that has long been used as a natural medicine in China, has attracted much interest for its anti-cancer effects against some kinds of tumours in recent years. Artesunate, extracted from the Chinese herb Artemisia annua, has proven to be effective and safe as an anti-malarial drug that possesses anticancer potential. The present study attempted to clarify if triptolide enhances artesunate-induced cytotoxicity in pancreatic cancer cell lines in vitro and in vivo.

METHODS

In vitro, to test synergic actions, cell viability and apoptosis were analyzed after treatment of pancreatic cancer cell lines with the two agents singly or in combination. The molecular mechanisms of apoptotic effects were also explored using qRT-PCR and Western blotting. In vivo, a tumor xenograft model was established in nude mice, for assessment of inhibitory effects of triptolide and artesunate.

RESULTS

We could show that the combination of triptolide and artesunate could inhibit pancreatic cancer cell line growth, and induce apoptosis, accompanied by expression of HSP 20 and HSP 27, indicating important roles in the synergic effects. Moreover, tumor growth was decreased with triptolide and artesunate synergy.

CONCLUSION

Our result indicated that triptolide and artesunate in combination at low concentrations can exert synergistic anti-tumor effects in pancreatic cancer cells with potential clinical applications.

The phosphorylation of Hsp20 enhances its association with amyloid-β to increase protection against neuronal cell death

Up-regulation of Hsp20 protein levels in response to amyloid fibril formation is considered a key protective response against the onset of Alzheimer's disease (AD). Indeed, the physical interaction between Hsp20 and Aβ is known to prevent Aβ oligomerisation and protects neuronal cells from Aβ mediated toxicity, however, details of the molecular mechanism and regulatory cell signalling events behind this process have remained elusive. Using both conventional MTT end-point assays and novel real time measurement of cell impedance, we show that Hsp20 protects human neuroblastoma SH-SY5Y cells from the neurotoxic effects of Aβ. In an attempt to provide a mechanism for the neuroprotection afforded by Hsp20, we used peptide array, co-immunoprecipitation analysis and NMR techniques to map the interaction between Hsp20 and Aβ and report a binding mode where Hsp20 binds adjacent to the oligomerisation domain of Aβ, preventing aggregation. The Hsp20/Aβ interaction is enhanced by Hsp20 phosphorylation, which serves to increase association with low molecular weight Aβ species and decrease the effective concentration of Hsp20 required to disrupt the formation of amyloid oligomers. Finally, using a novel fluorescent assay for the real time evaluation of morphology-specific Aβ aggregation, we show that phospho-dependency of this effect is more pronounced for fibrils than for globular Aβ forms and that 25mers corresponding to the Hsp20 N-terminal can be used as Aβ aggregate inhibitors. Our report is the first to provide a molecular model for the Hsp20/Aβ complex and the first to suggest that modulation of the cAMP/cGMP pathways could be a novel route to enhance Hsp20-mediated attenuation of Aβ fibril neurotoxicity.

Heat shock protein B6 potently increases non-small cell lung cancer growth

The aim of the present study was to address the effects of heat shock protein B6 (HspB6) on tumor growth and metastasis in BALB/c mice. Lewis lung carcinoma (LLC) cells were subcutaneously injected into BALB/c mice followed by intraperitoneal injection of recombinant HspB6 (HspB6 groups) or phosphate‑buffered saline (control groups). Tumor growth and metastasis were assessed by size measurement and weighing of tumors and cervical lymph nodes, respectively. Chemokine expression in tumor masses was quantified quantitative polymerase chain reaction and western blotting. Tumor cell apoptosis was detected by flow cytometric analysis. The proliferation and migration of LLC cells, stimulated with HspB6, were detected using Cell Counting Kit 8 and wound scratch assays in vitro. Tumors grafted into the BALB/c mice and intraperitoneally injected with HspB6 were significantly bigger in size than those grafted into the control mice. From 7 days following the injection, the weight of cervical lymph nodes in HspB6 groups was higher than that in the control mice. We also revealed that the apoptotic cell number in tumor masses in the HspB6 groups was lower than that of the control mice. CD31 expression of vascular endothelial cells was higher in tumors grafted in HspB6 groups than those grafted in the control mice. Concomitantly, the tumor tissue mRNA and protein expression enhancement of vascular endothelial growth factor, basic fibroblast growth factor and intercellular adhesion molecule 1 were greater in HspB6 mice than in the control mice. HspB6 also inhibited cell apoptosis and enhanced the migration and proliferation of LLCs in vitro. In conclusion, HspB6 exhibited tumor promotion through increasing tumor angiogenesis, tumor metastasis and inhibiting tumor cell apoptosis.

Chaperone function of two small heat shock proteins from maize

Small heat shock proteins (sHsps) are molecular chaperones that protect cells from the effect of heat and other stresses. Some sHsps are also expressed at specific stages of development. In plants different classes of sHsps are expressed in the various cellular compartments. While the Class I (cytosolic) sHsps in wheat and pea have been studied extensively, there are fewer experimental data on Class II (cytosolic) sHsps, especially in maize. Here we report the expression and purification of two Class II sHsps from Zea mays ssp. mays L. (cv. Oh43). The two proteins have almost identical sequences, with the significant exception of an additional nine-amino-acid intervening sequence near the beginning of the N-terminus in one of them. Both ZmHsp17.0-CII and ZmHsp17.8-CII oligomerize to form dodecamers at temperatures below heat shock, and we were able to visualize these dodecamers with TEM. There are significant differences between the two sHsps during heat shock at 43°C: ZmHsp17.8-CII dissociates into smaller oligomers than ZmHsp17.0-CII, and ZmHsp17.8-CII is a more efficient chaperone with target protein citrate synthase. Together with the previous observation that ZmHsp17.0-CII but not ZmHsp17.8-CII is expressed during development, we propose different roles in the cell for these two sHsps.

Arrestin-dependent localization of phosphodiesterases

Many G-protein-coupled receptors trigger the synthesis of cAMP in order to transduce signals from the membrane into the cell cytoplasm. As stimulation of each receptor type results in a specific physiological outcome, compartmentalization of proteins that make, break, and are activated by cAMP underpin receptor-specific responses. Until 2002, it was thought that static compartmentalization of phosphodiesterase 4 (PDE4), conferred by N-terminal targeting sequences, was one way to shape intricate cAMP gradients that formed after receptor activation. Discovery of the PDE4-β-arrestin complex represented a major breakthrough in cAMP signaling, as it spurred the initial realization that PDE4s could be transported to sites of high cAMP to orchestrate destruction of the second messenger at the same time as the receptor's signal to the G-protein is silenced. This chapter charts the scientific process that led to the discovery and characterization of the PDE4-β-arrestin interaction and discusses the known functions of this signaling complex.

Keep your heart in shape: molecular chaperone networks for treating heart disease

Despite major advances in the treatment of cardiac diseases, there is still a great need for drugs capable of counteracting the deterioration of cardiac muscle function in congestive heart failure. The role of misfolded protein accumulation as a causal event in the physiopathology of common cardiac diseases is an important emerging concept. Indeed, diverse stress conditions, including mechanical stretching and oxidative stress, can induce misfolded protein accumulation, causing cardiomyocyte death. Cells react to these stress conditions by activating molecular chaperones, a class of proteins that represents an endogenous salvage machinery, essential for rescuing physiological cell functions and sustaining cell survival. Chaperones, also known as heat shock proteins (Hsps), prevent accumulation of damaged proteins by promoting either their refolding or degradation via the proteasome or the autophagosome systems. In addition, molecular chaperones play a key role in intracellular signalling by controlling conformational changes required for activation/deactivation of signalling proteins, and their assembly in specific signalosome complexes. The key role of molecular chaperones in heart function is highlighted by the fact that a number of genetic mutations in chaperone proteins result in different forms of cardiomyopathies. Moreover, a considerable amount of experimental evidence indicates that increasing expression of chaperone proteins leads to an important cardio-protective role in ischaemia/reperfusion injury, heart failure, and arrhythmia, implicating these molecules as potential innovative therapeutic agents.

Contribution of small heat shock proteins to muscle development and function

Investigations undertaken over the past years have led scientists to introduce the concept of protein quality control (PQC) systems, which are responsible for polypeptide processing. The PQC system monitors proteostasis and involves activity of different chaperones such as small heat shock proteins (sHSPs). These proteins act during normal conditions as housekeeping proteins regulating cellular processes, and during stress conditions. They also mediate the removal of toxic misfolded polypeptides and thereby prevent development of pathogenic states. It is postulated that sHSPs are involved in muscle development. They could act via modulation of myogenesis or by maintenance of the structural integrity of signaling complexes. Moreover, mutations in genes coding for sHSPs lead to pathological states affecting muscular tissue functioning. This review focuses on the question how sHSPs, still relatively poorly understood proteins, contribute to the development and function of three types of muscle tissue: skeletal, cardiac and smooth.

Targeting protein-protein interactions within the cyclic AMP signaling system as a therapeutic strategy for cardiovascular disease

The cAMP signaling system can trigger precise physiological cellular responses that depend on the fidelity of many protein-protein interactions, which act to bring together signaling intermediates at defined locations within cells. In the heart, cAMP participates in the fine control of excitation-contraction coupling, hence, any disregulation of this signaling cascade can lead to cardiac disease. Due to the ubiquitous nature of the cAMP pathway, general inhibitors of cAMP signaling proteins such as PKA, EPAC and PDEs would act non-specifically and universally, increasing the likelihood of serious 'off target' effects. Recent advances in the discovery of peptides and small molecules that disrupt the protein-protein interactions that underpin cellular targeting of cAMP signaling proteins are described and discussed.

The potential role of small heat shock proteins in mitochondria

Mitochondria play a central role in cellular metabolism, calcium homeostasis, redox signaling and cell fates. Mitochondrial homeostasis is tightly regulated, and mitochondrial dysfunction is frequently associated with severe human pathologies. Small heat shock proteins are molecular chaperones that play major roles in development, stress responses, and diseases, and have been envisioned as targets for therapy. The mechanisms that lie behind the cytoprotection of small heat shock proteins are related to the regulation of mitochondrial functions. This review recapitulates the current knowledge of the expression of various small heat shock proteins in mitochondria and discusses their implication in the role of mitochondria and their regulation. Based on their involvement in mitochondrial normal physiology and pathology, a better understanding of their roles and regulation will pave the way for innovative approaches for the successful treatment of a range of stress-related syndromes whose etiology is based upon dysfunction of mitochondria.

Comparative differential proteomic profiles of nonfailing and failing hearts after in vivo thoracic aortic constriction in mice overexpressing FKBP12.6

Chronic pressure overload (PO) induces pathological left ventricular hypertrophy (LVH) leading to congestive heart failure (HF). Overexpression of FKBP12.6 (FK506-binding protein [K]) in mice should prevent Ca2+-leak during diastole and may improve overall cardiac function. In order to decipher molecular mechanisms involved in thoracic aortic constriction (TAC)-induced cardiac remodeling and the influence of gender and genotype, we performed a proteomic analysis using two-dimensional differential in-gel electrophoresis (2D-DIGE), mass spectrometry, and bioinformatics techniques to identify alterations in characteristic biological networks. Wild-type (W) and K mice of both genders underwent TAC. Thirty days post-TAC, the altered cardiac remodeling was accompanied with systolic and diastolic dysfunction in all experimental groups. A gender difference in inflammatory protein expression (fibrinogen, α-1-antitrypsin isoforms) and in calreticulin occurred (males > females). Detoxification enzymes and cytoskeletal proteins were noticeably increased in K mice. Both non- and congestive failing mouse heart exhibited down- and upregulation of proteins related to mitochondrial function and purine metabolism, respectively. HF was characterized by a decrease in enzymes related to iron homeostasis, and altered mitochondrial protein expression related to fatty acid metabolism, glycolysis, and redox balance. Moreover, two distinct differential protein profiles characterized TAC-induced pathological LVH and congestive HF in all TAC mice. FKBP12.6 overexpression did not influence TAC-induced deleterious effects. Huntingtin was revealed as a potential mediator for HF. A broad dysregulation of signaling proteins associated with congestive HF suggested that different sets of proteins could be selected as useful biomarkers for HF progression and might predict outcome in PO-induced pathological LVH.

Different anti-aggregation and pro-degradative functions of the members of the mammalian sHSP family in neurological disorders

The family of the mammalian small heat-shock proteins consists of 10 members (sHSPs/HSPBs: HSPB1-HSPB10) that all share a highly conserved C-terminal alpha-crystallin domain, important for the modulation of both their structural and functional properties. HSPB proteins are biochemically classified as molecular chaperones and participate in protein quality control, preventing the aggregation of unfolded or misfolded proteins and/or assisting in their degradation. Thus, several members of the HSPB family have been suggested to be protective in a number of neurodegenerative and neuromuscular diseases that are characterized by protein misfolding. However, the pro-refolding, anti-aggregation or pro-degradative properties of the various members of the HSPB family differ largely, thereby influencing their efficacy and protective functions. Such diversity depends on several factors, including biochemical and physical properties of the unfolded/misfolded client, the expression levels and the subcellular localization of both the chaperone and the client proteins. Furthermore, although some HSPB members are inefficient at inhibiting protein aggregation, they can still exert neuroprotective effects by other, as yet unidentified, manners; e.g. by maintaining the proper cellular redox state or/and by preventing the activation of the apoptotic cascade. Here, we will focus our attention on how the differences in the activities of the HSPB proteins can influence neurodegenerative and neuromuscular disorders characterized by accumulation of aggregate-prone proteins. Understanding their mechanism of action may allow us to target a specific member in a specific cell type/disease for therapeutic purposes.

Chemical informatics uncovers a new role for moexipril as a novel inhibitor of cAMP phosphodiesterase-4 (PDE4)

PDE4 is one of eleven known cyclic nucleotide phosphodiesterase families and plays a pivotal role in mediating hydrolytic degradation of the important cyclic nucleotide second messenger, cyclic 3′5′ adenosine monophosphate (cAMP). PDE4 inhibitors are known to have anti-inflammatory properties, but their use in the clinic has been hampered by mechanism-associated side effects that limit maximally tolerated doses. In an attempt to initiate the development of better-tolerated PDE4 inhibitors we have surveyed existing approved drugs for PDE4-inhibitory activity. With this objective, we utilised a high-throughput computational approach that identified moexipril, a well tolerated and safe angiotensin-converting enzyme (ACE) inhibitor, as a PDE4 inhibitor. Experimentally we showed that moexipril and two structurally related analogues acted in the micro molar range to inhibit PDE4 activity. Employing a FRET-based biosensor constructed from the nucleotide binding domain of the type 1 exchange protein activated by cAMP, EPAC1, we demonstrated that moexipril markedly potentiated the ability of forskolin to increase intracellular cAMP levels. Finally, we demonstrated that the PDE4 inhibitory effect of moexipril is functionally able to induce phosphorylation of the small heat shock protein, Hsp20, by cAMP dependent protein kinase A. Our data suggest that moexipril is a bona fide PDE4 inhibitor that may provide the starting point for development of novel PDE4 inhibitors with an improved therapeutic window.