alpha B-crystallin gene induction and phosphorylation by MKK6-activated p38. A potential role for alpha B-crystallin as a target of the p38 branch of the cardiac stress response

HSPB4/CRYAA Protect Photoreceptors during Retinal Detachment in Part through FAIM2 Regulation

Our previous study discussed crystallin family induction in an experimental rat model of retinal detachment. Therefore, we attempted to evaluate the role of α-crystallin in photoreceptor survival in an experimental model of retinal detachment, as well as its association with the intrinsically neuroprotective protein Fas-apoptotic inhibitory molecule 2 (FAIM2). Separation of retina and RPE was induced in rat and mouse eyes by subretinal injection of hyaluronic acid. Retinas were subsequently analyzed for the presence αA-crystallin (HSPB4) and αB-crystallin (HSPB5) proteins using immunohistochemistry and immunoblotting. Photoreceptor death was analyzed using terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL) staining and cell counts. The 661W cells subjected to FasL were used as a cell model of photoreceptor degeneration to assess the mechanisms of the protective effect of αA-crystallin and its dependence on its phosphorylation on T148. We further evaluated the interaction between FAIM2 and αA-crystallin using a co-immunoprecipitation assay. Our results showed that α-crystallin protein levels were rapidly induced in response to retinal detachment, with αA-crystallin playing a particularly important role in protecting photoreceptors during retinal detachment. Our data also show that the photoreceptor intrinsically neuroprotective protein FAIM2 is induced and interacts with α-crystallins following retinal detachment. Mechanistically, our work also demonstrated that the phosphorylation of αA-crystallin is important for the interaction of αA-crystallin with FAIM2 and their neuroprotective effect. Thus, αA-crystallin is involved in the regulation of photoreceptor survival during retinal detachment, playing a key role in the stabilization of FAIM2, serving as an important modulator of photoreceptor cell survival under chronic stress conditions.

Skeletal muscle desmin alterations following revascularization in peripheral artery disease claudicants

Peripheral artery disease (PAD) is characterized by varying severity of arterial stenosis, exercise induced claudication, malperfused tissue precluding normal healing and skeletal muscle dysfunction. Revascularization interventions improve circulation, but post-reperfusion changes within the skeletal muscle are not well characterized. This study investigates if revascularization enhanced hemodynamics increases walking performance with concurrent improvement of mitochondrial function and reverses abnormal skeletal muscle morphological features that develop with PAD. Fifty-eight patients completed walking performance testing and muscle biopsy before and 6 months after revascularization procedures. Muscle fiber morphology, desmin structure, and mitochondria respiration assessments before and after the revascularization were evaluated. Revascularization improved limb hemodynamics, walking function, and muscle morphology. Qualitatively not all participants recovered normal structural architecture of desmin in the myopathic myofibers after revascularization. Heterogenous responses in the recovery of desmin structure following revascularization may be caused by other underlying factors not reversed with hemodynamic improvements. Revascularization interventions clinically improve patient walking ability and can reverse the multiple subcellular functional and structural abnormalities in muscle cells. Further study is needed to characterize desmin structural remodeling with improvements in skeletal muscle morphology and function.

ATF6 protects against protein misfolding during cardiac hypertrophy

Cardiomyocytes activate the unfolded protein response (UPR) transcription factor ATF6 during pressure overload-induced hypertrophic growth. The UPR is thought to increase ER protein folding capacity and maintain proteostasis. ATF6 deficiency during pressure overload leads to heart failure, suggesting that ATF6 protects against myocardial dysfunction by preventing protein misfolding. However, conclusive evidence that ATF6 prevents toxic protein misfolding during cardiac hypertrophy is still pending. Here, we found that activation of the UPR, including ATF6, is a common response to pathological cardiac hypertrophy in mice. ATF6 KO mice failed to induce sufficient levels of UPR target genes in response to chronic isoproterenol infusion or transverse aortic constriction (TAC), resulting in impaired cardiac growth. To investigate the effects of ATF6 on protein folding, the accumulation of poly-ubiquitinated proteins as well as soluble amyloid oligomers were directly quantified in hypertrophied hearts of WT and ATF6 KO mice. Whereas only low levels of protein misfolding was observed in WT hearts after TAC, ATF6 KO mice accumulated increased quantities of misfolded protein, which was associated with impaired myocardial function. Collectively, the data suggest that ATF6 plays a critical adaptive role during cardiac hypertrophy by protecting against protein misfolding.

Desmin and its molecular chaperone, the αB-crystallin: How post-translational modifications modulate their functions in heart and skeletal muscles?

Maintenance of the highly organized striated muscle tissue requires a cell-wide dynamic network through protein-protein interactions providing an effective mechanochemical integrator of morphology and function. Through a continuous and complex trans-cytoplasmic network, desmin intermediate filaments ensure this essential role in heart and in skeletal muscle. Besides their role in the maintenance of cell shape and architecture (permitting contractile activity efficiency and conferring resistance towards mechanical stress), desmin intermediate filaments are also key actors of cell and tissue homeostasis. Desmin participates to several cellular processes such as differentiation, apoptosis, intracellular signalisation, mechanotransduction, vesicle trafficking, organelle biogenesis and/or positioning, calcium homeostasis, protein homeostasis, cell adhesion, metabolism and gene expression. Desmin intermediate filaments assembly requires αB-crystallin, a small heat shock protein. Over its chaperone activity, αB-crystallin is involved in several cellular functions such as cell integrity, cytoskeleton stabilization, apoptosis, autophagy, differentiation, mitochondria function or aggresome formation. Importantly, both proteins are known to be strongly associated to the aetiology of several cardiac and skeletal muscles pathologies related to desmin filaments disorganization and a strong disturbance of desmin interactome. Note that these key proteins of cytoskeleton architecture are extensively modified by post-translational modifications that could affect their functional properties. Therefore, we reviewed in the herein paper the impact of post-translational modifications on the modulation of cellular functions of desmin and its molecular chaperone, the αB-crystallin.

Functional Diversity of Mammalian Small Heat Shock Proteins: A Review

The small heat shock proteins (sHSPs), whose molecular weight ranges from 12∼43 kDa, are members of the heat shock protein (HSP) family that are widely found in all organisms. As intracellular stress resistance molecules, sHSPs play an important role in maintaining the homeostasis of the intracellular environment under various stressful conditions. A total of 10 sHSPs have been identified in mammals, sharing conserved α-crystal domains combined with variable N-terminal and C-terminal regions. Unlike large-molecular-weight HSP, sHSPs prevent substrate protein aggregation through an ATP-independent mechanism. In addition to chaperone activity, sHSPs were also shown to suppress apoptosis, ferroptosis, and senescence, promote autophagy, regulate cytoskeletal dynamics, maintain membrane stability, control the direction of cellular differentiation, modulate angiogenesis, and spermatogenesis, as well as attenuate the inflammatory response and reduce oxidative damage. Phosphorylation is the most significant post-translational modification of sHSPs and is usually an indicator of their activation. Furthermore, abnormalities in sHSPs often lead to aggregation of substrate proteins and dysfunction of client proteins, resulting in disease. This paper reviews the various biological functions of sHSPs in mammals, emphasizing the roles of different sHSPs in specific cellular activities. In addition, we discuss the effect of phosphorylation on the function of sHSPs and the association between sHSPs and disease.

Alpha B-Crystallin in Muscle Disease Prevention: The Role of Physical Activity

HSPB5 or alpha B-crystallin (CRYAB), originally identified as lens protein, is one of the most widespread and represented of the human small heat shock proteins (sHSPs). It is greatly expressed in tissue with high rates of oxidative metabolism, such as skeletal and cardiac muscles, where HSPB5 dysfunction is associated with a plethora of human diseases. Since HSPB5 has a major role in protecting muscle tissues from the alterations of protein stability (i.e., microfilaments, microtubules, and intermediate filament components), it is not surprising that this sHSP is specifically modulated by exercise. Considering the robust content and the protective function of HSPB5 in striated muscle tissues, as well as its specific response to muscle contraction, it is then realistic to predict a specific role for exercise-induced modulation of HSPB5 in the prevention of muscle diseases caused by protein misfolding. After offering an overview of the current knowledge on HSPB5 structure and function in muscle, this review aims to introduce the reader to the capacity that different exercise modalities have to induce and/or activate HSPB5 to levels sufficient to confer protection, with the potential to prevent or delay skeletal and cardiac muscle disorders.

HspB4/αA-Crystallin Modulates Neuroinflammation in the Retina via the Stress-Specific Inflammatory Pathways

PURPOSE

We have previously demonstrated that HspB4/αA-crystallin, a molecular chaperone, plays an important intrinsic neuroprotective role during diabetes, by its phosphorylation on residue 148. We also reported that HspB4/αA-crystallin is highly expressed by glial cells. There is a growing interest in the potential causative role of low-grade inflammation in diabetic retinopathy pathophysiology and retinal Müller glial cells' (MGCs') participation in the inflammatory response. MGCs indeed play a central role in retinal homeostasis via secreting various cytokines and other mediators. Hence, this study was carried out to delineate and understand the regulatory function of HspB4/αA-crystallin in the inflammatory response associated with metabolic stresses.

METHODS

Primary MGCs were isolated from knockout HspB4/αA-crystallin mice. These primary cells were then transfected with plasmids encoding either wild-type (WT), phosphomimetic (T148D), or non-phosphorylatable mutants (T148A) of HspB4/αA-crystallin. The cells were exposed to multiple metabolic stresses including serum starvation (SS) or high glucose with TNF-alpha (HG + T) before being further evaluated for the expression of inflammatory markers by qPCR. The total protein expression along with subcellular localization of NF-kB and the NLRP3 component was assessed by Western blot.

RESULTS

Elevated levels of IL-6, IL-1β, MCP-1, and IL-18 in SS were significantly diminished in MGCs overexpressing WT and further in T148D as compared to EV. The HG + T-induced increase in these inflammatory markers was also dampened by WT and even more significantly by T148D overexpression, whereas T148A was ineffective in either stress. Further analysis revealed that overexpression of WT or the T148D, also led to a significant reduction of Nlrp3, Asc, and caspase-1 transcript expression in serum-deprived MGCs and nearly abolished the NF-kB induction in HG + T diabetes-like stress. This mechanistic effect was further evaluated at the protein level and confirmed the stress-dependent regulation of NLRP3 and NF-kB by αA-crystallin.

CONCLUSIONS

The data gathered in this study demonstrate the central regulatory role of HspB4/αA-crystallin and its modulation by phosphorylation on T148 in retinal MGCs. For the first time, this study demonstrates that HspB4/αA-crystallin can dampen the stress-induced expression of pro-inflammatory cytokines through the modulation of multiple key inflammatory pathways, therefore, suggesting its potential as a therapeutic target for the modulation of chronic neuroinflammation.

Limb-bud and heart (LBH) inhibits cellular migration, invasion and epithelial-mesenchymal transition in nasopharyngeal carcinoma via downregulating αB-crystallin expression

Limb-bud and heart (LBH) gene has received increasing attention in recent cancer studies. Here we investigated the role of the LBH gene in regulating the metastasis capacity and epithelial-mesenchymal transition (EMT) of nasopharyngeal carcinoma (NPC) cells, and its potential mechanism. The expressions of LBH and αB-crystallin (CRYAB) were modulated by lentiviral infection, or plasmid/siRNA transfection, and the phosphorylation of p38 was suppressed by an inhibitor, to explore their functions in modulating NPC cell phenotypes, as well as the relationships of these factors with each other. Cellular proliferation, migration and invasion were examined by RTCA system, Transwell assays and Matrigel Transwell assays respectively. The EMT progression was indicated by RT-qPCR and Western blotting measuring the expressions of EMT biomarkers. NPC xenografts were constrcucted, and formed tumors were sectioned for morphology and immunohistofluorescence. The interaction between LBH and CRYAB was examined by colocalization and Fluorescence resonance energy transfer (FRET) analysis. We reached the conclusion that LBH inhibits the proliferation, migration, invasion and EMT of NPC cells, and its effects were partially achieved by suppressing p38 phosphorylation, which subsequently downregulates the mRNA expression and phosphorylation of CRYAB, while CRYAB directly interacts with LBH in NPC cells. This LBH-related pathway we revealed provides a novel therapeutic target for nasopharyngeal carcinoma research.

HspB5/αB-crystallin phosphorylation at S45 and S59 is essential for protection of the dendritic tree of rat hippocampal neurons

Rarefaction of the dendritic tree leading to neuronal dysfunction is a hallmark of many neurodegenerative diseases and we have shown previously that heat shock protein B5 (HspB5)/αB-crystallin is able to increase dendritic complexity in vitro. The aim of this study was to investigate if this effect is also present in vivo, if HspB5 can counteract dendritic rarefaction under pathophysiological conditions and the impact of phosphorylation of HspB5 in this process. HspB5 and eight mutants inhibiting or mimicking phosphorylation at the three phosphorylation sites serine (S)19, S45, and S59 were over-expressed in cultured rat hippocampal neurons with subsequent investigation of the complexity of the dendritic tree. Sholl analysis revealed significant higher complexity of the dendritic tree after over-expression of wild-type HspB5 and the mutant HspB5-AEE. All other mutants showed no or minor effects. For in vivo investigation in utero electroporation of mouse embryos was applied. At embryonal day E15.5 the respective plasmids were injected, cornu ammonis 1 (CA1) pyramidal cells transfected by electroporation and their basal dendritic trees were analyzed at post-natal day P15. In vivo, HspB5 and HspB5-AEE led to an increase of total dendritic length as well as a higher complexity. Finally, the dendritic effect of HspB5 was investigated under a pathophysiological condition, that is, iron deficiency which reportedly results in dendritic rarefaction. HspB5 and HspB5-AEE but not the non-phosphorylatable mutant HspB5-AAA significantly counteracted the dendritic rarefaction. Thus, our data suggest that up-regulation and selective phosphorylation of HspB5 in neurodegenerative diseases may preserve dendritic morphology and counteract neuronal dysfunction.

The transcription factor CREB acts as an important regulator mediating oxidative stress-induced apoptosis by suppressing αB-crystallin expression

The general transcription factor, CREB has been shown to play an essential role in promoting cell proliferation, neuronal survival and synaptic plasticity in the nervous system. However, its function in stress response remains to be elusive. In the present study, we demonstrated that CREB plays a major role in mediating stress response. In both rat lens organ culture and mouse lens epithelial cells (MLECs), CREB promotes oxidative stress-induced apoptosis. To confirm that CREB is a major player mediating the above stress response, we established stable lines of MLECs stably expressing CREB and found that they are also very sensitive to oxidative stress-induced apoptosis. To define the underlying mechanism, RNAseq analysis was conducted. It was found that CREB significantly suppressed expression of the αB-crystallin gene to sensitize CREB-expressing cells undergoing oxidative stress-induced apoptosis. CREB knockdown via CRISPR/CAS9 technology led to upregulation of αB-crystallin and enhanced resistance against oxidative stress-induced apoptosis. Moreover, overexpression of exogenous human αB-crystallin can restore the resistance against oxidative stress-induced apoptosis. Finally, we provided first evidence that CREB directly regulates αB-crystallin gene. Together, our results demonstrate that CREB is an important transcription factor mediating stress response, and it promotes oxidative stress-induced apoptosis by suppressing αB-crystallin expression.

αB-crystallin response to a pro-oxidant non-cytotoxic environment in murine cardiac cells: An "in vitro" and "in vivo" study

The αB-crystallin (HSPB5) protein is modulated in response to a wide variety of stressors generated by multiple physio-pathological conditions, sustained by reactive oxygen species (ROS) production. In cardiac muscle tissue, this protein regulates various cellular processes, such as protein degradation, apoptosis and the stabilization of cytoskeletal elements. In this work, we studied the role of HSPB5 expression, activation and localization in HL-1 murine cardiomyocytes exposed to pro-oxidant and non-cytotoxic H₂O₂ concentration, as well as in cardiac tissue isolated from mice following an acute, non-damaging endurance exercise. Our results demonstrated that HSPB5 is the most abundant HSP in both cardiac muscle tissue and HL-1 cells when compared to HSPB1 or HSPA1A (≈3-8 fold higher protein concentrations, p < 0.01). The acute exposure of cardiac muscle cells to sustainable level of H₂O₂ "in vitro" or to aerobic non-damaging exercise "in vivo" determined a fast and specific increase of HSPB5 phosphorylation (from 3 up to 25 fold increase, p < 0.01) correlated to an increase in lipid peroxidation (p < 0.05). In both experimental models, p-HSPB5 likely facilitated both the interaction with β-actin, desmin, and α-Filamin 1, the last one identified as new HSPB5 substrate in cardiac cells, as well as the sub-localization of HSPB5 within the same cellular compartment or the re-localization between compartments (i.e., nucleus and cytosol). Taken together, these data point out the role of "oxidative eustress" induced by physiological conditions in activating the molecular machinery devoted to cardiomyocytes' protection and candidate HSPB5 as a putative molecular mediator for the health benefits induced in cardiac tissue by exercise training.

Mesencephalic astrocyte-derived neurotrophic factor is an ER-resident chaperone that protects against reductive stress in the heart

We have previously demonstrated that ischemia/reperfusion (I/R) impairs endoplasmic reticulum (ER)-based protein folding in the heart and thereby activates an unfolded protein response sensor and effector, activated transcription factor 6α (ATF6). ATF6 then induces mesencephalic astrocyte-derived neurotrophic factor (MANF), an ER-resident protein with no known structural homologs and unclear ER function. To determine MANF's function in the heart in vivo, here we developed a cardiomyocyte-specific MANF-knockdown mouse model. MANF knockdown increased cardiac damage after I/R, which was reversed by AAV9-mediated ectopic MANF expression. Mechanistically, MANF knockdown in cultured neonatal rat ventricular myocytes (NRVMs) impaired protein folding in the ER and cardiomyocyte viability during simulated I/R. However, this was not due to MANF-mediated protection from reactive oxygen species generated during reperfusion. Because I/R impairs oxygen-dependent ER protein disulfide formation and such impairment can be caused by reductive stress in the ER, we examined the effects of the reductive ER stressor DTT. MANF knockdown in NRVMs increased cell death from DTT-mediated reductive ER stress, but not from nonreductive ER stresses caused by thapsigargin-mediated ER Ca²⁺ depletion or tunicamycin-mediated inhibition of ER protein glycosylation. In vitro, recombinant MANF exhibited chaperone activity that depended on its conserved cysteine residues. Moreover, in cells, MANF bound to a model ER protein exhibiting improper disulfide bond formation during reductive ER stress but did not bind to this protein during nonreductive ER stress. We conclude that MANF is an ER chaperone that enhances protein folding and myocyte viability during reductive ER stress.

Identification of key genes involved in myocardial infarction

Background

This study focuses on the identification of conserved genes involved in myocardial infarction (MI), and then analyzed the differentially expressed genes (DEGs) between the incident and recurrent events to identify MI-recurrent biomarkers.

Methods

Gene expression data of MI peripheral blood were downloaded from GSE97320 and GSE66360 datasets. We identified the common DEGs in these two datasets by functional enrichment analysis and protein–protein interaction (PPI) network analysis. GSE48060 was further analyzed to validate the conserved genes in MI and to compare the DEGs between the incident and recurrent MI.

Results

A total of 477 conserved genes were identified in the comparison between MI and control. Protein–protein interaction (PPI) network showed hub genes, such as MAPK14, STAT3, and MAPKAPK2. Part of those conserved genes was validated in the analysis of GSE48060. The DEGs in the incident and recurrent MI showed significant differences, including RNASE2 and A2M-AS1 as the potential biomarkers of MI recurrence.

Conclusions

The conserved genes in the pathogenesis of MI were identified, benefit for target therapy. Meanwhile, some specific genes may be used as markers for the prediction of recurrent MI.

Electronic supplementary material

The online version of this article (10.1186/s40001-019-0381-x) contains supplementary material, which is available to authorized users.

Cellular and Molecular Adaptation of Arabian Camel to Heat Stress

To cope with the extreme heat stress and drought of the desert, the Arabian camel (Camelus dromedarius) has developed exceptional physiological and biochemical particularities. Previous reports focused mainly on the physiological features of Arabian camel and neglected its cellular and molecular characteristics. Heat shock proteins are suggested to play a key role in the protein homeostasis and thermotolerance. Therefore, we aim by this review to elucidate the implication of camel HSPs in its physiological adaptation to heat stress and compare them with HSPs in related mammalian species. Correlation of these molecules to the adaptive mechanisms in camel is of special importance to expand our understanding of the overall camel physiology and homeostasis.

The early response of αB-crystallin to a single bout of aerobic exercise in mouse skeletal muscles depends upon fiber oxidative features

Besides its substantial role in eye lens, αB-crystallin (HSPB5) retains fundamental function in striated muscle during physiological or pathological modifications. In this study, we aimed to analyse the cellular and molecular factors driving the functional response of HSPB5 protein in different muscles from mice subjected to an acute bout of non-damaging endurance exercise or in C2C12 myocytes upon exposure to pro-oxidant environment, chosen as “in vivo” and “in vitro” models of a physiological stressing conditions, respectively.

To this end, red (GR) and white gastrocnemius (GW), as sources of slow-oxidative and fast-glycolytic/oxidative fibers, as well as the soleus (SOL), mainly composed of slow-oxidative type fibers, were obtained from BALB/c mice, before (CTRL) and at different times (0′, 15′, 30′ 120′) following 1-h of running. Although the total level of HSPB5 protein was not affected by exercise, we found a significantly increase of phosphorylated HSPB5 (p-HSPB5) only in GR and SOL skeletal muscle with a higher amount of type I and IIA/X myofibers. The fiber-specific activation of HSPB5 was correlated to its interaction with the actin filaments, as well as to an increased level of lipid peroxidation and carbonylated proteins. The role of the pro-oxidant environment in HSPB5 response was investigated in terminally differentiated C2C12 myotubes, where most of HSPB5/pHSPB5 pool was present in the cytosolic compartment in standard culture conditions. As a result of exposure to pro-oxidizing, but not cytotoxic, H₂O₂ concentration, the p-38MAPK-mediated phosphorylation of HSPB5 resulted functional to promote its interaction with the myofibrillar components, such as β-actin, desmin and filamin 1.

This study provides novel information on the molecular pathway underlying the HSPB5 physiological function in skeletal muscle, confirming the contribution of the pro-oxidant environment in HSPB5 activation and interaction with substrate/client myofibrillar proteins, offering new insights for the study of myofibrillar myopathies and cardiomyopathies.

The BAG3-dependent and -independent roles of cardiac small heat shock proteins

Small heat shock proteins (sHSPs) comprise an important protein family that is ubiquitously expressed, is highly conserved among species, and has emerged as a critical regulator of protein folding. While these proteins are functionally important for a variety of tissues, an emerging field of cardiovascular research reveals sHSPs are also extremely important for maintaining normal cardiac function and regulating the cardiac stress response. Notably, numerous mutations in genes encoding sHSPs have been associated with multiple cardiac diseases. sHSPs (HSPB5, HSPB6, and HSPB8) have been described as mediating chaperone functions within the heart by interacting with the cochaperone protein BCL-2-associated anthanogene 3 (BAG3); however, recent reports indicate that sHSPs (HSPB7) can perform other BAG3-independent functions. Here, we summarize the cardiac functions of sHSPs and present the notion that cardiac sHSPs function via BAG3-dependent or -independent pathways.

From Desert to Medicine: A Review of Camel Genomics and Therapeutic Products

Camels have an important role in the lives of human beings, especially in arid regions, due to their multipurpose role and unique ability to adapt to harsh conditions. In spite of its enormous economic, cultural, and biological importance, the camel genome has not been widely studied. The size of camel genome is roughly 2.38 GB, containing over 20,000 genes. The unusual genetic makeup of the camel is the main reason behind its ability to survive under extreme environmental conditions. The camel genome harbors several unique variations which are being investigated for the treatment of several disorders. Various natural products from camels have also been tested and prescribed as adjunct therapy to control the progression of ailments. Interestingly, the camel employs unique immunological and molecular mechanisms against pathogenic agents and pathological conditions. Here, we broadly review camel classification, distribution and breed as well as recent progress in the determination of the camel genome, its size, genetic distribution, response to various physiological conditions, immunogenetics and the medicinal potential of camel gene products.

Hyperosmotic stress stimulates autophagy via the NFAT5/mTOR pathway in cardiomyocytes

Hyperosmotic stress may be initiated during a diverse range pathological circumstances, which in turn results in tissue damage. In this process, the activation of survival signaling, which has the capacity to restore cell homeostasis, determines cell fate. Autophagy is responsible for cell survival and is activated by various pathological stimuli. However, its interplay with hyperosmotic stress and its effect on terminally differentiated cardiac myocytes is unknown. Nuclear factor of activated T‑cells 5 (NFAT5), an osmo‑sensitive transcription factor, mediates the expression of cell survival associated‑genes under hyperosmotic conditions. The present study investigated whether NFAT5 signaling is required in hyperosmotic stress‑induced autophagy. It was demonstrated that the presence of a hyperosmotic stress induced an increase in NFAT5 expression, which in turn triggered autophagy through autophagy‑related protein 5 (Atg5) activation. By contrast, NFAT5 silencing inhibited DNA damage response 1 protein expression, which then initiated the activation of mammalian target of rapamycin signaling. Therefore, the balance between NFAT5‑induced apoptosis and autophagy may serve a critical role in the determination of the fate of cardiomyocytes under hyperosmotic stress. These data suggest that autophagy activation is a beneficial adaptive response to attenuate hyperosmotic stress‑induced cell death. Therefore, increasing autophagy through activation of NFAT5 may provide a novel cardioprotective strategy against hyperosmotic stress‑induced damage.

The role of αB-crystallin in skeletal and cardiac muscle tissues

All organisms and cells respond to various stress conditions such as environmental, metabolic, or pathophysiological stress by generally upregulating, among others, the expression and/or activation of a group of proteins called heat shock proteins (HSPs). Among the HSPs, special attention has been devoted to the mutations affecting the function of the αB-crystallin (HSPB5), a small heat shock protein (sHsp) playing a critical role in the modulation of several cellular processes related to survival and stress recovery, such as protein degradation, cytoskeletal stabilization, and apoptosis. Because of the emerging role in general health and disease conditions, the main objective of this mini-review is to provide a brief account on the role of HSPB5 in mammalian muscle physiopathology. Here, we report the current known state of the regulation and localization of HSPB5 in skeletal and cardiac tissue, making also a critical summary of all human HSPB5 mutations known to be strictly associated to specific skeletal and cardiac diseases, such as desmin-related myopathies (DRM), dilated (DCM) and restrictive (RCM) cardiomyopathy. Finally, pointing to putative strategies for HSPB5-based therapy to prevent or counteract these forms of human muscular disorders.

BYD Ameliorates Oxidative Stress-Induced Myocardial Apoptosis in Heart Failure Post-Acute Myocardial Infarction via the P38 MAPK-CRYAB Signaling Pathway

Aim: Heart failure (HF) post-acute myocardial infarction (AMI) contributes to increasing mortality and morbidity worldwide. Baoyuan decoction (BYD) is a well-known traditional Chinese medicine formula that exhibits myocardial protection clinically. The aim of this study was to identify the effects of BYD on oxidative stress-induced apoptosis in HF post-AMI and characterize the underlying mechanism.

Methods and Results: In our study, we constructed left anterior descending (LAD)-induced AMI rat models and a macrophage-conditioned media (CM)-induced H9C2 injury model. In vivo, BYD could protect cardiac functions, decrease inflammatory cell infiltration and inhibit oxidative stress-induced apoptosis. In vitro, BYD inhibited cellular apoptosis and regulated the expressions of key apoptotic molecules, including reducing the expression of B cell lymphoma-2 (Bcl-2) associated X protein (Bax) and cleaved caspase-3 and -9. Interestingly, the P38 mitogen-activated protein kinase (MAPK)-αB-crystallin (CRYAB) signaling pathway was activated by BYD treatment, and the P38 MAPK inhibitor SB203580 could reverse the protective effects of BYD.

Conclusion: This study identified that BYD protected against oxidative stress-induced myocardial apoptosis via the P38 MAPK-CRYAB pathway. CRYAB may become a novel therapeutic target for AMI.

Proteomics/phosphoproteomics of left ventricular biopsies from patients with surgical coronary revascularization and pigs with coronary occlusion/reperfusion: remote ischemic preconditioning

Remote ischemic preconditioning (RIPC) by repeated brief cycles of limb ischemia/reperfusion reduces myocardial ischemia/reperfusion injury. In left ventricular (LV) biopsies from patients undergoing coronary artery bypass grafting (CABG), only the activation of signal transducer and activator of transcription 5 was associated with RIPC’s cardioprotection. We have now used an unbiased, non-hypothesis-driven proteomics and phosphoproteomics approach to analyze LV biopsies from patients undergoing CABG and from pigs undergoing coronary occlusion/reperfusion without (sham) and with RIPC. False discovery rate-based statistics identified a higher prostaglandin reductase 2 expression at early reperfusion with RIPC than with sham in patients. In pigs, the phosphorylation of 116 proteins was different between baseline and early reperfusion with RIPC and/or with sham. The identified proteins were not identical for patients and pigs, but in-silico pathway analysis of proteins with ≥2-fold higher expression/phosphorylation at early reperfusion with RIPC in comparison to sham revealed a relation to mitochondria and cytoskeleton in both species. Apart from limitations of the proteomics analysis per se, the small cohorts, the sampling/sample processing and the number of uncharacterized/unverifiable porcine proteins may have contributed to this largely unsatisfactory result.

AlphaB-crystallin regulates remyelination after peripheral nerve injury

AlphaB-crystallin (αBC) is a small heat shock protein that is constitutively expressed by peripheral nervous system (PNS) axons and Schwann cells. To determine what role this crystallin plays after peripheral nerve damage, we found that loss of αBC impaired remyelination, which correlated with a reduced presence of myelinating Schwann cells and increased numbers of nonmyelinating Schwann cells. The heat shock protein also seems to regulate the cross-talk between Schwann cells and axons, because expected changes in neuregulin levels and ErbB2 receptor expression after PNS injury were disrupted in the absence of αBC. Such dysregulations led to defects in conduction velocity and motor and sensory functions that could be rescued with therapeutic application of the heat shock protein in vivo. Altogether, these findings show that αBC plays an important role in regulating Wallerian degeneration and remyelination after PNS injury.

HspB5/αB-crystallin increases dendritic complexity and protects the dendritic arbor during heat shock in cultured rat hippocampal neurons

The small heat shock protein ΗspΒ5 (αB-crystallin) exhibits generally cytoprotective functions and possesses powerful neuroprotective capacity in the brain. However, little is known about the mode of action of ΗspΒ5 or other members of the HspB family particularly in neurons. To get clues of the neuronal function of HspBs, we overexpressed several HspBs in cultured rat hippocampal neurons and investigated their effect on neuronal morphology and stress resistance. Whereas axon length and synapse density were not affected by any HspB, dendritic complexity was enhanced by HspB5 and, to a lesser extent, by HspB6. Furthermore, we could show that this process was dependent on phosphorylation, since a non-phosphorylatable mutant of HspB5 did not show this effect. Rarefaction of the dendritic arbor is one hallmark of several neurodegenerative diseases. To investigate if HspB5, which is upregulated at pathophysiological conditions, might be able to protect dendrites during such situations, we exposed HspB5 overexpressing neuronal cultures to heat shock. HspB5 prevented heat shock-induced rarefaction of dendrites. In conclusion, we identified regulation of dendritic complexity as a new function of HspB5 in hippocampal neurons.

Differential phosphorylation-based regulation of αB-crystallin chaperone activity for multipass transmembrane proteins

We have previously shown that αB-crystallin (CRYAB), a small heat shock protein (sHsp) that prevents irreversible aggregation of unfolded protein by an ATP-independent chaperone activity, plays a pivotal role in the biogenesis of multipass transmembrane proteins (TMPs) assisting their folding from the cytosolic side of the endoplasmic reticulum (ER) (D'Agostino et al., 2013). Here we present evidence, based on phosphomimetic substitutions, that the three phosphorytable serine residues at position 19, 45 and 59 of CRYAB play a different regulatory role in this novel chaperone activity: S19 and S45 have a strong inhibitory effect, either alone or in combination, while S59 has not and counteracts the inhibition caused by single phosphomimetic substitutions at S19 and S45. Interestingly, all phosphomimetic substitutions determine the formation of smaller oligomeric complexes containing CRYAB, indicating that the inhibitory effect seen for S19 and S45 cannot be ascribed to the reduction of oligomerization frequently associated to a decreased chaperone activity. These results indicate that phosphorylation finely regulates the chaperone activity of CRYAB with multipass TMPs and suggest a pivotal role for S59 in this process.

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CRYAB chaperone activity toward ATP7B-H1069Q and Fz4-FEVR.

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Phosphomimetic S19D and S45D inhibit CRYAB chaperone activity.

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Phosphomimetic S59D protects CRYAB chaperone activity.

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Pseudo-phosphorylation decreases CRYAB oligomerization.

A novel molecular dynamics approach to evaluate the effect of phosphorylation on multimeric protein interface: the αB-Crystallin case study

BACKGROUND

Phosphorylation is one of the most important post-translational modifications (PTM) employed by cells to regulate several cellular processes. Studying the effects of phosphorylations on protein structures allows to investigate the modulation mechanisms of several proteins including chaperones, like the small HSPs, which display different multimeric structures according to the phosphorylation of a few serine residues. In this context, the proposed study is aimed at finding a method to correlate different PTM patterns (in particular phosphorylations at the monomers interface of multimeric complexes) with the dynamic behaviour of the complex, using physicochemical parameters derived from molecular dynamics simulations in the timescale of nanoseconds.

RESULTS

We have developed a methodology relying on computing nine physicochemical parameters, derived from the analysis of short MD simulations, and combined with N identifiers that characterize the PTMs of the analysed protein. The nine general parameters were validated on three proteins, with known post-translational modified conformation and unmodified conformation. Then, we applied this approach to the case study of αB-Crystallin, a chaperone which multimeric state (up to 40 units) is supposed to be controlled by phosphorylation of Ser45 and Ser59. Phosphorylation of serines at the dimer interface induces the release of hexamers, the active state of αB-Crystallin. 30 ns of MD simulation were obtained for each possible combination of dimer phosphorylation state and average values of structural, dynamic, energetic and functional features were calculated on the equilibrated portion of the trajectories. Principal Component Analysis was applied to the parameters and the first five Principal Components, which summed up to 84 % of the total variance, were finally considered.

CONCLUSIONS

The validation of this approach on multimeric proteins, which structures were known both modified and unmodified, allowed us to propose a new approach that can be used to predict the impact of PTM patterns in multi-modified proteins using data collected from short molecular dynamics simulations. Analysis on the αB-Crystallin case study clusters together all-P dimers with all-P hexamers and no-P dimer with no-P hexamer and results suggest a great influence of Ser59 phosphorylation on chain B.

Regulation of αA- and αB-crystallins via phosphorylation in cellular homeostasis

αA-Crystallin (αA) and αB-crystallin (αB) are small heat shock proteins responsible for the maintenance of transparency in the lens. In non-lenticular tissues, αB is involved in both maintenance of the cytoskeleton and suppression of neurodegeneration amongst other roles. Despite their importance in maintaining cellular health, modifications and mutations to αA and αB appear to play a role in disease states such as cataract and myopathies. The list of modifications that have been reported is extensive and include oxidation, disulphide bond formation, C- and N-terminal truncation, acetylation, carboxymethylation, carboxyethylation, carbamylation, deamidation, phosphorylation and methylation. Such modifications, notably phosphorylation, are alleged to cause changes to chaperone activity by inducing substructural changes and altering subunit exchange dynamics. Although the effect modification has on the activities of αA and αB is contentious, it has been proposed that these changes are responsible for the induction of hyperactivity and are thereby indirectly responsible for protein deposition characteristic of many diseases associated with αA and αB. This review compiles all reported sites of αA and αB modifications, and investigates the role phosphorylation, in particular, plays in cellular processes.

Phosphorylation of αB-crystallin: Role in stress, aging and patho-physiological conditions

BACKGROUND

αB-crystallin, once thought to be a lenticular protein, is ubiquitous and has critical roles in several cellular processes that are modulated by phosphorylation. Serine residues 19, 45 and 59 of αB-crystallin undergo phosphorylation. Phosphorylation of S45 is mediated by p44/42 MAP kinase, whereas S59 phosphorylation is mediated by MAPKAP kinase-2. Pathway involved in S19 phosphorylation is not known.

SCOPE OF REVIEW

The review highlights the role of phosphorylation in (i) oligomeric structure, stability and chaperone activity, (ii) cellular processes such as apoptosis, myogenic differentiation, cell cycle regulation and angiogenesis, and (iii) aging, stress, cardiomyopathy-causing αB-crystallin mutants, and in other diseases.

MAJOR CONCLUSIONS

Depending on the context and extent of phosphorylation, αB-crystallin seems to confer beneficial or deleterious effects. Phosphorylation alters structure, stability, size distribution and dynamics of the oligomeric assembly, thus modulating chaperone activity and various cellular processes. Phosphorylated αB-crystallin has a tendency to partition to the cytoskeleton and hence to the insoluble fraction. Low levels of phosphorylation appear to be protective, while hyperphosphorylation has negative implications. Mutations in αB-crystallin, such as R120G, Q151X and 464delCT, associated with inherited myofibrillar myopathy lead to hyperphosphorylation and intracellular inclusions. An ongoing study in our laboratory with phosphorylation-mimicking mutants indicates that phosphorylation of R120GαB-crystallin increases its propensity to aggregate.

GENERAL SIGNIFICANCE

Phosphorylation of αB-crystallin has dual role that manifests either beneficial or deleterious consequences depending on the extent of phosphorylation and interaction with cytoskeleton. Considering that disease-causing mutants of αB-crystallin are hyperphosphorylated, moderation of phosphorylation may be a useful strategy in disease management. This article is part of a Special Issue entitled Crystallin Biochemistry in Health and Disease.

The case for inhibiting p38 mitogen-activated protein kinase in heart failure

This minireview discusses the evidence that the inhibition of p38 mitogen-activated protein kinases (p38 MAPKs) maybe of therapeutic value in heart failure. Most previous experimental studies, as well as past and ongoing clinical trials, have focussed on the role of p38 MAPKs in myocardial infarction and acute coronary syndromes. There is now growing evidence that these kinases are activated within the myocardium of the failing human heart and in the heart and blood vessels of animal models of heart failure. Furthermore, from a philosophical viewpoint the chronic activation of the adaptive stress pathways that lead to the activation of p38 MAPKs in heart failure is analogous to the chronic activation of the sympathetic, renin-aldosterone-angiotensin and neprilysin systems. These have provided some of the most effective therapies for heart failure. This minireview questions whether similar and synergistic advantages would follow the inhibition of p38 MAPKs.

Hyperglycemia induced expression, phosphorylation, and translocation of αB-crystallin in rat skeletal muscle

αB-Crystallin (αBC) is a member of the small heat shock protein family that responds to a variety of stress and prevents the aggregation of partially unfolded proteins. Chronic hyperglycemia created during diabetes results in skeletal muscle atrophy and leads to diabetic myopathy. The aim of this study was to investigate the role of αBC under chronic hyperglycemia in rat skeletal muscle. Diabetes was induced in Wistar rats by a single i.p injection of streptozotocin and maintained for a period of 12 weeks at the end of which the animals were sacrificed and the muscle was collected. The protein levels of αBC and its phosphorylation status in gastrocnemius muscle were analyzed by immunoblotting. The translocation of phosphorylated αBC was analyzed by detergent solubility assay, co-immunoprecipitation (Co-IP), and immunohistochemistry. The cell death was analyzed by TUNEL assay and by apoptotic markers. The interaction of αBC with Bax was analyzed by Co-IP. Chronic hyperglycemia significantly increased the protein levels of αBC and its phosphorylation at S59 by activation of p38 mitogen-activated protein kinase (p38MAPK) and at S45 by activation of the extracellular regulated protein kinase 1/2 (ERK1/2). Further, phosphorylated αBC translocated and interacted with desmin indicating that phosphorylated αBC forms might be involved in protection of sarcomere structures from disruption in chronic hyperglycemia. Further, Co-IP studies showed an impaired interaction of αBC with Bax which could be one of the possible factors for increased cell death as evidenced by TUNEL assay in diabetic muscle. These results suggest that an increased expression, phosphorylation, translocation of αBC, and its involvement in apoptosis might play a significant role in maintenance of cytoskeletal architecture and protection of cells from apoptosis in diabetic skeletal muscle.

Crystallin αB acts as a molecular guard in mouse decidualization: regulation and function during early pregnancy

Although decidualization is crucial for the establishment of successful pregnancy, the molecular mechanism underlying decidualization remains poorly understood. Crystallin αB (CryAB), a small heat shock protein (sHSP), is up-regulated and phosphorylated in mouse decidua. In mouse primary endometrial stromal cells, CryAB is induced upon progesterone treatment via HIF1α. In addition, CryAB is strongly phosphorylated through the p38-MAPK pathway under stress or during in vitro decidualization. Knockdown of CryAB results in the increase of apoptosis of stromal cells and inhibits decidualization under oxidative or inflammatory stress. Our data indicate that CryAB protects decidualization against stress conditions.

Expression and induction of small heat shock proteins in rat heart under chronic hyperglycemic conditions

The induction of small heat shock proteins (sHsp) is observed under various stress conditions to protect the cells and organisms from adverse events including diabetes. Diabetic cardiomyopathy is a common complication of diabetes. Therefore, in this study, we investigated the expression of sHsp under chronic hyperglycemic conditions in rat heart. Hyperglycemia was induced in WNIN rats by intraperitoneal injection of streptozotocin and maintained for a period of 12weeks. Expression of sHsp, phosphorylation and translocation of phosphoforms of Hsp27 and αB-crystallin (αBC) from cytosolic fraction to cytoskeletal fraction was analyzed. While the expression of MKBP, HspB3, αBC was found to be increased in diabetic heart, expression of Hsp20 was decreased. Chronic hyperglycemia further induced phosphorylation of αBC at S59, S45, Hsp27 at S82, p38MAPK and p44/42MAPK. However, pS59-αBC and pS82-Hsp27 were translocated from detergent-soluble to detergent-insoluble fraction under hyperglycemic conditions. Furthermore, the interaction of pS82-Hsp27 and pS59-αBC with desmin was increased under hyperglycemia. However, the interaction of αBC and pS59-αBC with Bax was impaired by chronic hyperglycemia. These results suggest up regulation of sHsp (MKBP, HspB3 and αBC), phosphorylation and translocation of Hsp27 and αBC to striated sarcomeres and impaired interaction of αBC and pS59-αBC with Bax under chronic hyperglycemia.

Crosstalk between mitogen-activated protein kinases and mitochondria in cardiac diseases: therapeutic perspectives

Cardiovascular diseases cause more mortality and morbidity worldwide than any other diseases. Although many intracellular signaling pathways influence cardiac physiology and pathology, the mitogen-activated protein kinase (MAPK) family has garnered significant attention because of its vast implications in signaling and crosstalk with other signaling networks. The extensively studied MAPKs ERK1/2, p38, JNK, and ERK5, demonstrate unique intracellular signaling mechanisms, responding to a myriad of mitogens and stressors and influencing the signaling of cardiac development, metabolism, performance, and pathogenesis. Definitive relationships between MAPK signaling and cardiac dysfunction remain elusive, despite 30 years of extensive clinical studies and basic research of various animal/cell models, severities of stress, and types of stimuli. Still, several studies have proven the importance of MAPK crosstalk with mitochondria, powerhouses of the cell that provide over 80% of ATP for normal cardiomyocyte function and play a crucial role in cell death. Although many questions remain unanswered, there exists enough evidence to consider the possibility of targeting MAPK-mitochondria interactions in the prevention and treatment of heart disease. The goal of this review is to integrate previous studies into a discussion of MAPKs and MAPK-mitochondria signaling in cardiac diseases, such as myocardial infarction (ischemia), hypertrophy and heart failure. A comprehensive understanding of relevant molecular mechanisms, as well as challenges for studies in this area, will facilitate the development of new pharmacological agents and genetic manipulations for therapy of cardiovascular diseases.

Cardioprotective 3',4'-dihydroxyflavonol attenuation of JNK and p38(MAPK) signalling involves CaMKII inhibition

DiOHF (3',4'-dihydroxyflavonol) is cardioprotective against I/R (ischaemia/reperfusion) injury. The biological activities of flavonols are associated with kinase modulation to alter cell signalling. We thus investigated the effects of DiOHF on the activation of MAPKs (mitogen-activated protein kinases) that regulate the cardiac stress response. In an ovine model of I/R, JNK (c-Jun N-terminal kinase), p38(MAPK), ERK (extracellular-signal-regulated kinase) and Akt were activated, and NP202, a pro-drug of DiOHF, reduced infarct size and inhibited JNK and p38(MAPK) activation, whereas ERK and Akt phosphorylation were unaltered. Similarly, in cultured myoblasts, DiOHF pre-treatment preserved viability and inhibited activation of JNK and p38(MAPK), but not ERK in response to acute oxidative and chemotoxic stress. Furthermore, DiOHF prevented stress-activation of the direct upstream regulators MKK4/7 (MAPK kinase 4/7) and MKK3/6 respectively. We utilized small-molecule affinity purification and identified CaMKII (Ca(2+)/calmodulin-dependent protein kinase II) as a kinase targeted by DiOHF and demonstrated potent CaMKII inhibition by DiOHF in vitro. Moreover, the specific inhibition of CaMKII with KN-93, but not KN-92, prevented oxidative stress-induced activation of JNK and p38(MAPK). The present study indicates DiOHF inhibition of CaMKII and attenuation of MKK3/6→p38(MAPK) and MKK4/7→JNK signalling as a requirement for the protective effects of DiOHF against stress stimuli and myocardial I/R injury.

The cytosolic chaperone α-crystallin B rescues folding and compartmentalization of misfolded multispan transmembrane proteins

The α-crystallin B chain (CRYAB or HspB5) is a cytosolic chaperone belonging to the small heat shock protein family, which is known to help in the folding of cytosolic proteins. Here we show that CRYAB binds the mutant form of at least two multispan transmembrane proteins (TMPs), exerting an anti-aggregation activity. It rescues the folding of mutant Frizzled4, which is responsible for a rare autosomal dominant form of familial exudative vitreoretinopathy (Fz4-FEVR), and the mutant ATP7B Cu transporter (ATP7B-H1069Q) associated with a common form of Wilson's disease. In the case of Fz4-FEVR, CRYAB prevents the formation of inter-chain disulfide bridges between the lumenal ectodomains of the aggregated mutant chains, which enables correct folding and promotes appropriate compartmentalization on the plasma membrane. ATP7B-H1069Q, with help from CRYAB, folds into the proper conformation, moves to the Golgi complex, and responds to copper overload in the same manner as wild-type ATP7B. These findings strongly suggest that CRYAB plays a pivotal role, previously undetected, in the folding of multispan TMPs and, from the cytosol, is able to orchestrate folding events that take place in the lumen of the ER. Our results contribute to the explanation of the complex scenario behind multispan TMP folding; additionally, they serve to expose interesting avenues for novel therapeutic approaches.

Proteomics of old world camelid (Camelus dromedarius): Better understanding the interplay between homeostasis and desert environment

Life is the interplay between structural–functional integrity of biological systems and the influence of the external environment. To understand this interplay, it is useful to examine an animal model that competes with harsh environment. The dromedary camel is the best model that thrives under severe environment with considerable durability. The current proteomic study on dromedary organs explains a number of cellular mysteries providing functional correlates to arid living. Proteome profiling of camel organs suggests a marked increased expression of various cytoskeleton proteins that promote intracellular trafficking and communication. The comparative overexpression of α-actinin of dromedary heart when compared with rat heart suggests an adaptive peculiarity to sustain hemoconcentration–hemodilution episodes associated with alternative drought-rehydration periods. Moreover, increased expression of the small heat shock protein, α B-crystallin facilitates protein folding and cellular regenerative capacity in dromedary heart. The observed unbalanced expression of different energy related dependent mitochondrial enzymes suggests the possibility of mitochondrial uncoupling in the heart in this species. The evidence of increased expression of H+-ATPase subunit in camel brain guarantees a rapidly usable energy supply. Interestingly, the guanidinoacetate methyltransferase in camel liver has a renovation effect on high energy phosphate with possible concomitant intercession of ion homeostasis. Surprisingly, both hump fat tissue and kidney proteomes share the altered physical distribution of proteins that favor cellular acidosis. Furthermore, the study suggests a vibrant nature for adipose tissue of camel hump by the up-regulation of vimentin in adipocytes, augmenting lipoprotein translocation, blood glucose trapping, and challenging external physical extra-stress. The results obtained provide new evidence of homeostasis in the arid habitat suitable for this mammal.

α-Crystallin B prevents apoptosis after H2O2 exposure in mouse neonatal cardiomyocytes

α-Crystallin B (cryAB) is the most abundant small heat shock protein in cardiomyocytes (CMs) and has been shown to have potent antiapoptotic properties. Because the mechanism by which cryAB prevents apoptosis has not been fully characterized, we examined its protective effects at the cellular level by silencing cryAB in mouse neonatal CMs using lentivector-mediated transduction of short hairpin RNAs. Subcellular fractionation of whole hearts showed that cryAB is cytosolic under control conditions, and after H(2)O(2) exposure, it translocates to the mitochondria. Phosphorylated cryAB (PcryAB) is mainly associated with the mitochondria, and any residual cytosolic PcryAB translocates to the mitochondria after H(2)O(2) exposure. H(2)O(2) exposure caused increases in cryAB and PcryAB levels, and cryAB silencing resulted in increased levels of apoptosis after exposure to H(2)O(2). Coimmunoprecipitation assays revealed an apparent interaction of both cryAB and PcryAB with mitochondrial voltage-dependent anion channels (VDAC), translocase of outer mitochondrial membranes 20 kDa (TOM 20), caspase 3, and caspase 12 in mouse cardiac tissue. Our results are consistent with the conclusion that the cardioprotective effects of cryAB are mediated by its translocation from the cytosol to the mitochondria under conditions of oxidative stress and that cryAB interactions with VDAC, TOM 20, caspase 3, and caspase 12 may be part of its protective mechanism.

Global changes in the rat heart proteome induced by prolonged morphine treatment and withdrawal

Morphine belongs among the most commonly used opioids in medical practice due to its strong analgesic effects. However, sustained administration of morphine leads to the development of tolerance and dependence and may cause long-lasting alterations in nervous tissue. Although proteomic approaches enabled to reveal changes in multiple gene expression in the brain as a consequence of morphine treatment, there is lack of information about the effect of this drug on heart tissue. Here we studied the effect of 10-day morphine exposure and subsequent drug withdrawal (3 or 6 days) on the rat heart proteome. Using the iTRAQ technique, we identified 541 proteins in the cytosol, 595 proteins in the plasma membrane-enriched fraction and 538 proteins in the mitochondria-enriched fraction derived from the left ventricles. Altogether, the expression levels of 237 proteins were altered by morphine treatment or withdrawal. The majority of changes (58 proteins) occurred in the cytosol after a 3-day abstinence period. Significant alterations were found in the expression of heat shock proteins (HSP27, α-B crystallin, HSP70, HSP10 and HSP60), whose levels were markedly up-regulated after morphine treatment or withdrawal. Besides that morphine exposure up-regulated MAPK p38 (isoform CRA_b) which is a well-known up-stream mediator of phosphorylation and activation of HSP27 and α-B crystallin. Whereas there were no alterations in the levels of proteins involved in oxidative stress, several changes were determined in the levels of pro- and anti-apoptotic proteins. These data provide a complex view on quantitative changes in the cardiac proteome induced by morphine treatment or withdrawal and demonstrate great sensitivity of this organ to morphine.

A potential role of crystallin in the vitreous bodies of rats after ischemia-reperfusion injury

PURPOSE

Ischemia-reperfusion injury (I/R injury) is known not only to induce hypoxic and oxidative stress, but also to cause retinal degeneration in rats. Crystallins, known to inhibit the formation of reactive oxygen species, reduce apoptotic cell death. Our goal was to clarify not only the role of I/R injury-mediated crystallins, but also to evaluate the correlation of these compounds to anti-inflammation in the vitreous body.

METHODS

Twenty-four Sprague-Dawley rats were used in this study. We induced I/R injury by clamping the optic nerve for 30 minutes and then releasing it. The vitreous bodies were obtained from the experimental and control subjects 24, 48, and 72 hours after I/R injury. Two-dimensional electrophoresis was performed, and the targeted spots were further investigated using matrix-assisted laser desorption-ionization time-of-flight mass spectrometry, spectrophotometry, Western blotting, and histological examination.

RESULTS

After I/R injury, 23 spots were identified as crystallins. The βB2 crystallins were transcriptionally and post-translationally regulated, whereas the αB crystallins were controlled by post-translational modifications in the vitreous bodies of the rats. The total amounts of αA and β crystallins (including isotypes of β crystalline) had increased 48 hours after injury. The phosphorylation of αB crystallin (at serine residues 19, 45, and 59) was significantly increased 48 hours later, whereas phosphorylation of ERK1/2 showed the greatest decrease.

CONCLUSIONS

During hypoxic and oxidation stress, our results suggest that phosphorylated αB crystalline inhibits RAS, resulting in the inactivation of ERK1/2. The phosphorylation of αB crystallin may be associated with the inflammatory suppression in the vitreous body via the I/R injury model system.

Novel roles for α-crystallins in retinal function and disease

α-Crystallins are key members of the superfamily of small heat shock proteins that have been studied in detail in the ocular lens. Recently, novel functions for α-crystallins have been identified in the retina and in the retinal pigmented epithelium (RPE). αB-Crystallin has been localized to multiple compartments and organelles including mitochondria, golgi apparatus, endoplasmic reticulum and nucleus. α-Crystallins are regulated by oxidative and endoplasmic reticulum stress, and inhibit apoptosis-induced cell death. α-Crystallins interact with a large number of proteins that include other crystallins, and apoptotic, cytoskeletal, inflammatory, signaling, angiogenic, and growth factor molecules. Studies with RPE from αB-crystallin deficient mice have shown that αB-crystallin supports retinal and choroidal angiogenesis through its interaction with vascular endothelial growth factor. αB-Crystallin has also been shown to have novel functions in the extracellular space. In RPE, αB-crystallin is released from the apical surface in exosomes where it accumulates in the interphotoreceptor matrix and may function to protect neighboring cells. In other systems administration of exogenous recombinant αB-crystallin has been shown to be anti-inflammatory. Another newly described function of αB-crystallin is its ability to inhibit β-amyloid fibril formation. α-Crystallin minichaperone peptides have been identified that elicit anti-apoptotic function in addition to being efficient chaperones. Generation of liposomal particles and other modes of nanoencapsulation of these minipeptides could offer great therapeutic advantage in ocular delivery for a wide variety of retinal degenerative, inflammatory and vascular diseases including age-related macular degeneration and diabetic retinopathy.

Specific phosphorylation of αA-crystallin is required for the αA-crystallin-induced protection of astrocytes against staurosporine and C2-ceramide toxicity

We previously reported that αA-crystallin and protease-activated receptor are involved in protection of astrocytes against C2-ceramide- and staurosporine-induced cell death (Li et al., 2009). Here, we investigated the molecular mechanism of αA-crystallin-mediated cytoprotection. We found that the expression of mutants mimicking specific phosphorylation of αA-crystallin increases the protection of astrocytes. However, the expression of mutants mimicking unphosphorylation of αA-crystallin results in loss of protection. These data revealed that the phosphorylation of αA-crystallin at Ser122 and Ser148 is required for protection. Furthermore, we explored the mechanism of cytoprotection of astrocytes by αA-crystallin. Application of specific inhibitors of p38 and ERK abrogates the protection of astrocytes by over-expression of αA-crystallin. Thus, p38 and ERK contribute to protective processes by αA-crystallin. This is comparable to our previous results which demonstrated that p38 and ERK regulated protease-activated receptor-2 (PAR-2)/αB-crystallin-mediated cytoprotection. Furthermore, we found that PAR-2 activation increases the expression of αA-crystallin. Thus, endogenous αA-crystallin protects astrocytes via mechanisms, which regulate the expression and/or phosphorylation status of αA-crystallin.

Simultaneous administration of insulin-like growth factor-1 and darbepoetin alfa protects the rat myocardium against myocardial infarction and enhances angiogenesis

Recent studies have shown that insulin growth factor-1 (IGF-1) and either erythropoietin (EPO) or the long-acting EPO analog Darbepoetin alfa (DA) protect the heart against ischemia/reperfusion (I/R) and myocardial infarction (MI). The present study examined the cardioprotective effect of simultaneous treatments with IGF-1 and DA in these models of cardiac injury. Rats were subjected to I/R or MI and were treated with IGF-1, DA, and a combination of IGF-1 and DA, or vehicle treatment. IGF-1 and DA treatments imparted similar protective effect by reducing infarct size. Moreover, these treatments led to improvement of cardiac function after I/R or MI compared to vehicle. In the reperfused heart, apoptosis was reduced with either or both IGF-1 and DA treatments as measured by reduced TUNEL staining and caspase-3 activity. In addition, after MI, treatment with IGF-1 or DA significantly induced angiogenesis. This angiogenic effect was enhanced significantly when IGF-1 and DA were given simultaneously compared to vehicle or either agents alone. These data indicate simultaneous pharmacological treatments with IGF-1 and DA protect the heart against I/R and MI injuries. This protection results in reduced infarct size and improved cardiac function. Moreover, this treatment reduces apoptosis and enhances angiogenesis in the ischemic heart.

Parallel activation of Ca(2+)-induced survival and death pathways in cardiomyocytes by sorbitol-induced hyperosmotic stress

Hyperosmotic stress promotes rapid and pronounced apoptosis in cultured cardiomyocytes. Here, we investigated if Ca(2+) signals contribute to this response. Exposure of cardiomyocytes to sorbitol [600 mosmol (kg water)(-1)] elicited large and oscillatory intracellular Ca(2+) concentration increases. These Ca(2+) signals were inhibited by nifedipine, Cd(2+), U73122, xestospongin C and ryanodine, suggesting contributions from both Ca(2+) influx through voltage dependent L-type Ca(2+) channels plus Ca(2+) release from intracellular stores mediated by IP(3) receptors and ryanodine receptors. Hyperosmotic stress also increased mitochondrial Ca(2+) levels, promoted mitochondrial depolarization, reduced intracellular ATP content, and activated the transcriptional factor cyclic AMP responsive element binding protein (CREB), determined by increased CREB phosphorylation and electrophoretic mobility shift assays. Incubation with 1 mM EGTA to decrease extracellular [Ca(2+)] prevented cardiomyocyte apoptosis induced by hyperosmotic stress, while overexpression of an adenoviral dominant negative form of CREB abolished the cardioprotection provided by 1 mM EGTA. These results suggest that hyperosmotic stress induced by sorbitol, by increasing Ca(2+) influx and raising intracellular Ca(2+) concentration, activates Ca(2+) release from stores and causes cell death through mitochondrial function collapse. In addition, the present results suggest that the Ca(2+) increase induced by hyperosmotic stress promotes cell survival by recruiting CREB-mediated signaling. Thus, the fate of cardiomyocytes under hyperosmotic stress will depend on the balance between Ca(2+)-induced survival and death pathways.

Serine 59 phosphorylation of {alpha}B-crystallin down-regulates its anti-apoptotic function by binding and sequestering Bcl-2 in breast cancer cells

The small heat shock protein (sHSP) αB-crystallin is a new oncoprotein in breast carcinoma that predicts poor clinical outcome in breast cancer. However, although several reports have demonstrated that phosphorylation of sHSPs modify their structural and functional properties, the significance of αB-crystallin phosphorylation in cancer cells has not yet been investigated. In this study, we have characterized the phosphorylation status of αB-crystallin in breast epithelial carcinoma cells line MCF7 submitted to anti-cancer agents like vinblastine. We have showed that the main phosphorylation site of αB-crystallin in response to vinblastine is serine 59 and determined a correlation between this post-translational modification and higher apoptosis level. The overexpression of the serine 59 "pseudophosphorylated" mutant (S59E) induces a significant increase in the apoptosis level of vinblastine-treated MCF7 cells. In contrast, overexpression of wild-type αB-crystallin or "nonphosphorylatable" mutant (S59A) result in a resistance to this microtubule-depolymerizing agent, while inhibition of endogenous levels of αB-crystallin by expression of shRNA lowers it. Analyzing further the molecular mechanism of this phenomenon, we report for the first time that phosphorylated αB-crystallin preferentially interacts with Bcl-2, an anti-apoptotic protein, and this interaction prevents the translocation of Bcl-2 to mitochondria. Hence, this study identifies serine 59 phosphorylation as an important key in the down-regulation of αB-crystallin anti-apoptotic function in breast cancer and suggests new strategies to improve anti-cancer treatments.

Repression of the cardiac myosin light chain-2 gene in skeletal muscle requires site-specific association of antithetic regulator, Nished, and HDACs

The transcriptional activation mechanisms that regulate tissue-specific expression of cardiac muscle genes have been extensively investigated, but little is known of the regulatory events involved in repression of cardiac-specific genes in non-cardiac cells. We have previously reported that Nished, a ubiquitous transcription factor, interacts with a positive sequence element, the Intron Regulatory Element (IRE) as well as a negatively acting element, the Cardiac-Specific Sequence (CSS), in myosin light chain-2 (MLC2v) gene to promote activation and repression of the gene in cardiac and skeletal muscle cells respectively. Here, we show that the negative regulation of cardiac MLC2v gene in skeletal muscle cells is mediated via the interaction of Nished with histone deacetylase (HDAC) co-repressor. Treatment of cells with the HDAC inhibitor, Trichostatin A (TSA), alleviates the repressor activity of Nished in a dose-dependent manner. Co-transfection studies in primary muscle cells in culture and in Nished expressing stable skeletal muscle cell line demonstrate that Nished down-regulates the cardiac MLC2 gene expression when its association is restricted to CSS alone. Chromatin immunoprecipitation data suggest that the CSS-mediated repression of cardiac MLC2v gene in skeletal muscle cells excludes the participation of the positive element IRE despite the presence of an identical Nished binding site. Taken together, it appears that the negative control of MLC2v transcription is based on a dual mode of regulations, one that affords inaccessibility of IRE to Nished and second that promotes the formation of the transcription repression complex at the inhibitory CSS site to silence the cardiac gene in skeletal muscle cell.