Human alphaA- and alphaB-crystallins bind to Bax and Bcl-X(S) to sequester their translocation during staurosporine-induced apoptosis

The activation of LBH-CRYAB signaling promotes cardiac protection against I/R injury by inhibiting apoptosis and ferroptosis

Myocardial ischemia-reperfusion (I/R) injury stands out among cardiovascular diseases, and current treatments are considered unsatisfactory. For cardiomyocytes (CMs) in ischemic tissues, the upregulation of Limb-bud and Heart (LBH) and αB-crystallin (CRYAB) and their subsequent downregulation in the context of cardiac fibrosis have been verified in our previous research. Here, we focused on the effects and mechanisms of activated LBH-CRYAB signaling on damaged CMs during I/R injury, and confirmed the occurrence of mitochondrial apoptosis and ferroptosis during I/R injury. The application of inhibitors, ectopic expression vectors, and knockout mouse models uniformly verified the role of LBH in alleviating both apoptosis and ferroptosis of CMs. p53 was identified as a mutual downstream effector for both LBH-CRYAB-modulated apoptosis and ferroptosis inhibition. In mouse models, LBH overexpression was confirmed to exert enhanced cardiac protection against I/R-induced apoptosis and ferroptosis, suggesting that LBH could serve as a promising target for the development of I/R therapy.

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.

SUMO1-regulated DBC1 promotes p53-dependent stress-induced apoptosis of lens epithelial cells

Deleted in breast cancer 1 (DBC1) was initially identified from a homozygously deleted region in human chromosome 8p21. It has been well established that DBC1 plays a dual role during cancer development. Depending on the physiological context, it can promote or inhibit tumorigenesis. Whether it plays a role in lens pathogenesis remains elusive. In the present study, we demonstrated that DBC1 is highly expressed in lens epithelial cells from different vertebrates and in retina pigment epithelial cells as well. Moreover, DBC1 is SUMOylated through SUMO1 conjugation at K591 residue in human and mouse lens epithelial cells. The SUMOylated DBC1 is localized in the nucleus and plays an essential role in promoting stress-induced apoptosis. Silence of DBC1 attenuates oxidative stress-induced apoptosis. In contrast, overexpression of DBC1 enhances oxidative stress-induced apoptosis, and this process depends on p53. Mechanistically, DBC1 interacts with p53 to regulate its phosphorylation status at multiple sites and the SUMOylation of DBC1 enhances its interaction with p53. Together, our results identify that DBC1 is an important regulator mediating stress-induced apoptosis in lens, and thus participates in control of lens cataractogenesis.

Mini-αA Upregulates the miR-155-5p Target Gene CDK2 and Plays an Antiapoptotic Role in Retinal Pigment Epithelial Cells during Oxidative Stress

Background

Age-related macular degeneration (AMD) is the leading cause of serious vision loss in the elderly. Regulating microRNA (miRNA) gene expression offers exciting new avenues for treating AMD. This study aimed to investigate whether miRNAs and their target genes play an antiapoptotic role during oxidative stress-induced apoptosis of retinal pigment epithelial (RPE) cells via mini-αA.

Methods

ARPE-19 cells were treated with 3.5 mM NaIO3 for 48 h to establish a retinal degeneration model. Cells were treated with mini-αA (10, 15, and 20 μM) for 4 h. miR-155-5p was knocked down and overexpressed. Cell viability and apoptosis were measured using the Cell Counting Kit-8 assay and flow cytometry, respectively. The reactive oxygen species level was detected by flow cytometry. miR-155-5p target genes were predicted via bioinformatics. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes analyses were performed for miR-155-5p target genes. A quantitative real-time polymerase chain reaction was performed to detect miRNAs and cell cycle-related target genes. Western blotting was performed to measure the levels of apoptotic pathway genes encoding Bcl-2, Bax, cleaved caspase-3, and cyclin-dependent kinase 2 (CDK2). Dual-luciferase reporter gene assay was performed to verify the targeted binding relationship between miR-155-5p and CDK2.

Results

NaIO3 can induce oxidative damage and promote apoptosis. Conversely, mini-αA had inhibitory effects and could reverse the oxidative damage and apoptosis triggered by NaIO3 in the retinal degeneration model. The expression of miR-155-5p was upregulated in cells treated with NaIO3 and was downregulated after mini-αA treatment. Furthermore, miR-155-5p can target the following cell cycle-related and proliferation-related genes: CDK2, CDK4, CCND1, and CCND2. Moreover, our study indicated that miR-155-5p was involved in the antioxidative damage and antiapoptotic effects of mini-αA via CDK2 regulation.

Conclusions

miR-155-5p promotes the antioxidative damage and antiapoptotic effects of mini-αA during oxidative stress-induced apoptosis of RPE cells via CDK2 regulation. This study provides a new therapeutic target for AMD.

Peptains block retinal ganglion cell death in animal models of ocular hypertension: implications for neuroprotection in glaucoma

Ocular hypertension is a significant risk factor for vision loss in glaucoma due to the death of retinal ganglion cells (RGCs). This study investigated the effects of the antiapoptotic peptides peptain-1 and peptain-3a on RGC death in vitro in rat primary RGCs and in mouse models of ocular hypertension. Apoptosis was induced in primary rat RGCs by trophic factor deprivation for 48 h in the presence or absence of peptains. The effects of intravitreally injected peptains on RGC death were investigated in mice subjected to retinal ischemic/reperfusion (I/R) injury and elevated intraocular pressure (IOP). I/R injury was induced in mice by elevating the IOP to 120 mm Hg for 1 h, followed by rapid reperfusion. Ocular hypertension was induced in mice by injecting microbeads (MB) or silicone oil (SO) into the anterior chamber of the eye. Retinal flatmounts were immunostained with RGC and activated glial markers. Effects on anterograde axonal transport were determined by intravitreal injection of cholera toxin-B. Peptain-1 and peptain-3a inhibited neurotrophic factor deprivation-mediated RGC apoptosis by 29% and 35%, respectively. I/R injury caused 52% RGC loss, but peptain-1 and peptain-3a restricted RGC loss to 13% and 16%, respectively. MB and SO injections resulted in 31% and 36% loss in RGCs following 6 weeks and 4 weeks of IOP elevation, respectively. Peptain-1 and peptain-3a inhibited RGC death; the loss was only 4% and 12% in MB-injected eyes and 16% and 15% in SO-injected eyes, respectively. Anterograde transport was defective in eyes with ocular hypertension, but this defect was substantially ameliorated in peptain-injected eyes. Peptains suppressed ocular hypertension-mediated retinal glial activation. In summary, our results showed that peptains block RGC somal and axonal damage and neuroinflammation in animal models of glaucoma. We propose that peptains have the potential to be developed as therapeutics against neurodegeneration in glaucoma.

The role of heat shock proteins in metastatic colorectal cancer: A review

Heat shock proteins (HSPs) are a large molecular chaperone family classified by their molecular weights, including HSP27, HSP40, HSP60, HSP70, HSP90, and HSP110. HSPs are likely to have antiapoptotic properties and participate actively in various processes such as tumor cell proliferation, invasion, metastases, and death. In this review, we discuss comprehensively the functions of HSPs associated with the progression of colorectal cancer (CRC) and metastasis and resistance to cancer therapy. Taken together, HSPs have numerous clinical applications as biomarkers for cancer diagnosis and prognosis and potential therapeutic targets for CRC and its related metastases.

MAB21L1 promotes survival of lens epithelial cells through control of αB-crystallin and ATR/CHK1/p53 pathway

The male abnormal gene family 21 (mab21), was initially identified in C. elegans. Since its identification, studies from different groups have shown that it regulates development of ocular tissues, brain, heart and liver. However, its functional mechanism remains largely unknown. Here, we demonstrate that Mab21L1 promotes survival of lens epithelial cells. Mechanistically, Mab21L1 upregulates expression of αB-crystallin. Moreover, our results show that αB-crystallin prevents stress-induced phosphorylation of p53 at S-20 and S-37 through abrogating the activation of the upstream kinases, ATR and CHK1. As a result of suppressing p53 activity by αB-crystallin, Mab21L1 downregulates expression of Bak but upregulates Mcl-1 during stress insult. Taken together, our results demonstrate that Mab21L1 promotes survival of lens epithelial cells through upregulation of αB-crystallin to suppress ATR/CHK1/p53 pathway.

Crystallins Play a Crucial Role in Glaucoma and Promote Neuronal Cell Survival in an In Vitro Model Through Modulating Müller Cell Secretion

Purpose

The aim of this study was to explore the roles of crystallins in the context of aging in glaucoma and potential mechanisms of neuroprotection in an experimental animal model of glaucoma.

Methods

Intraocular pressure (IOP) was significantly elevated for 8 weeks in animals at different ages (10 days, 12 weeks, and 44 weeks) by episcleral vein cauterization. Retinal ganglion cells (RGCs) were quantified by anti-Brn3a immunohistochemical staining (IHC). Proteomics using ESI-LTQ Orbitrap XL-MS was used to analyze the presence and abundance of crystallin isoforms the retinal samples, respectively. Neuroprotective property and localization of three selected crystallins CRYAB, CRYBB2, and CRYGB as most significantly changed in retina and retinal layers were determined by IHC. Their expressions and endocytic uptakes into Müller cells were analyzed by IHC and Western blotting. Müller cell secretion of neurotrophic factors into the supernatant following CRYAB, CRYBB2, and CRYGB supplementation in vitro was measured via microarray.

Results

IOP elevation resulted in significant RGC loss in all age groups (P < 0.001). The loss increased with aging. Proteomics analysis revealed in parallel a significant decrease of crystallin abundance – especially CRYAB, CRYBB2, and CRYGB. Significant neuroprotective effects of CRYAB, CRYBB2, and CRYGB after addition to retinal cultures were demonstrated (P < 0.001). Endocytic uptake of CRYAB, CRYBB2, and CRYGB was seen in Müller cells with subsequent increased secretion of various neurotrophic factors into the supernatant, including nerve growth factor, clusterin, and matrix metallopeptidase 9.

Conclusions

An age-dependent decrease in CRYAB, CRYBB2, and CRYGB abundance is found going along with increased RGC loss. Addition of CRYAB, CRYBB2, and CRYGB to culture protected RGCs in vitro. CRYAB, CRYBB2, and CRYGB were uptaken into Müller cells. Secretion of neurotrophic factors was increased as a potential mode of action.

iTRAQ proteomics of sentinel lymph nodes for identification of extracellular matrix proteins to flag metastasis in early breast cancer

Patients with early breast cancer are affected by metastasis to axillary lymph nodes. Metastasis to these nodes is crucial for staging and quality of surgery. Sentinel Lymph Node Biopsy that is currently used to assess lymph node metastasis is not effective. This necessitates identification of biomarkers that can flag metastasis. Early stage breast cancer patients were recruited. Surgical resection of breast was followed by identification of sentinel lymph nodes. Fresh frozen section biopsy was used to assign metastatic and non-metastatic sentinel lymph nodes. Discovery phase included iTRAQ proteomics coupled with mass spectrometric analysis to identify differentially expressed proteins. Data is available via ProteomeXchange with identifier PXD027668. Validation was done by bioinformatic analysis and ELISA. There were 2398 unique protein groups and 109 differentially expressed proteins comparing metastatic and non-metastatic lymph nodes. Forty nine proteins were up-regulated, and sixty proteins that were down regulated in metastatic group. Bioinformatic analysis showed ECM-receptor interaction pathways to be implicated in lymph node metastasis. ELISA confirmed up-regulation of ECM proteins in metastatic lymph nodes. ECM proteins have requisite parameters to be developed as a diagnostic tool to assess status of sentinel lymph nodes to guide surgical intervention in early breast cancer.

αA-Crystallin Mediated Neuroprotection in the Retinal Neurons Is Independent of Protein Kinase B

Phosphatidylinositol 3-kinase (PI3K)/Akt signal pathway mediates pro-survival function in neurons. In the retina, PI3K/AKT/mTOR signaling pathway is related to the early pathogenesis of diabetic retinopathy. Signaling molecules in the membrane-initiated signaling pathway exhibiting neuroprotective function interacts with the PI3K/Akt pathway as an important survival pathway. Molecular chaperone α-crystallins are known to potentially interact and/or regulate various pro-survival and pro-apoptotic proteins to regulate cell survival. Among these demonstrated mechanisms, they are well-reported to regulate and inhibit apoptosis by interacting and sequestrating the proapoptotic proteins such as Bax and Bcl-Xs. We studied the importance of metabolic stress-induced enhanced Akt signaling and αA-crystallin interdependence for exhibiting neuroprotection in metabolically challenged retinal neurons. For the first time, this study has revealed that αA-crystallin and activated Akt are significantly neuroprotective in the stressed retinal neurons, independent of each other. Furthermore, the study also highlighted that significant inhibition of the PI3K-Akt pathway does not alter the neuroprotective ability of αA-crystallin in stressed retinal neurons. Interestingly, our study also demonstrated that in the absence of Akt activation, αA-crystallin inhibits the translocation of Bax in the mitochondria during metabolic stress, and this function is regulated by the phosphorylation of αA-crystallin on residue 148.

Crystallin Alpha-B Overexpression as a Possible Marker of Reactive Astrogliosis in Human Cerebral Contusions

The pathophysiology of traumatic brain injury (TBI) has not yet been fully elucidated. Crystallin alpha-B (CRYAB) is a molecular chaperone that apparently tries to stabilize the rapid thickening of the intermediate filaments of glial fibrillary acidic protein (GFAP) during the process of reactive astrogliosis in response to TBI. Previous analyses of the gene expression profile in human brain contusion tissue showed us an exacerbated CRYAB overexpression. Here, we used 3, 3’-diaminobenzidine (DAB) immunohistochemistry and immunofluorescence to verify CRYAB overexpression and to describe its expression and distribution in samples of contused cortical tissue derived from emergency decompressive surgery after severe TBI. The histological expression of CRYAB was mainly seen in subcortical white matter astrocytes of injured tissue. Most of the cells that overexpressed GFAP in the analyzed tissue also overexpressed CRYAB, a finding corroborated by the co-localization of the two markers. The only difference was the presence of a few pyramidal neurons that expressed CRYAB in layer V of the cerebral cortex. The selective vulnerability of layer V of the cerebral cortex during TBI could explain the expression of CRYAB in neurons of this cortical layer. Our results indicate a parallel behavior in the cellular expression of CRYAB and GFAP during the subacute response to TBI. These results lead us to postulate CRYAB as a possible marker of reactive astrogliosis in contused cortical tissue.

The small heat shock protein HSPB5 attenuates the severity of lupus nephritis in lupus-prone mice

Lupus nephritis (LN) is a common and serious complication of systemic lupus erythematosus. The current treatments for LN are accompanied with severe immunotoxicity and have limits of effectiveness. Since our in vitro experiments demonstrated that a small heat shock protein (HSP), alpha-B crystallin (HSPB5; CRYAB), selectively modulates myeloid cells towards anti-inflammatory and tolerogenic phenotypes, the aim of this study was to investigate whether HSPB5 can attenuate the severity of LN. MRL/lpr mice were treated intravenously with HSPB5 at 2.5 or 10 μg/dose twice per week after disease onset, from 11 to 21 weeks of age. Disease progression was monitored by weekly measurements of proteinuria, and sera, spleens, and kidneys were collected for assessment at the terminal time point. Treatment with 10 μg HSPB5 substantially reduced endocapillary proliferation and tubular atrophy, which significantly reduced proteinuria and blood urea nitrogen (BUN). Compared to vehicle, 10 μg HSPB5 treatment substantially decreased activation/proliferation of splenocytes, increased IL-10+ macrophages, T and B regulatory cells (Treg, Breg), increased serum IL-10, and lowered expression of IL-6 in kidneys, which correlated with improved kidney function and pathology. This study demonstrated the utility of exogenous human HSPB5 to attenuate severe nephropathy in MRL/lpr mice and provides evidence in favour of a novel therapeutic approach for lupus nephritis.

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.

Salvianolic acid A relieves cognitive disorder after chronic cerebral ischemia: Involvement of Drd2/Cryab/NF-κB pathway

Chronic cerebral ischemia (CCI) refers to long-term hypoperfusion of cerebral blood flow with the main clinical manifestations of progressive cognitive impairment. The pathological mechanism of CCI is complex, and there is a lack of effective treatments. Salvianolic acid A (SalA) is a neuroprotective extract of Salvia miltiorrhiza with the effects of anti-inflammation and anti-apoptosis. In this study, the effect of SalA on cognitive function and Drd2/Cryab/NF-κB signaling pathway in rats with CCI was investigated. Morris water maze and open field test were used to observe the effects of SalA on the cognitive function of CCI rats. The pathological changes in the brain were observed by HE, Nissl, and LFB staining. TUNEL staining, enzyme-linked immunosorbent assay, and western blot analysis were used to detect the inflammatory and apoptosis in the cortex and hippocampus. The expression of Drd2/Cryab/NF-κB pathway-related molecules and Drd2 localization were detected by western blotting and dual immunofluorescence, respectively. SH-SY5Y cells were exposed to chronic hypoglycemic and hypoxic injury in vitro, and Drd2 inhibitor haloperidol was used to verify the involved pathway. The results showed that SalA could improve the cognitive function of CCI rats, reduce pathological damage of cortex and hippocampus, inhibit neuroinflammation and apoptosis, and suppress the activation of NF-κB by regulating Drd2/Cryab pathway. And SalA inhibited NF-κB activation and nuclear translocation in SH-SY5Y cells by upregulating Drd2/Cryab pathway, which was reversed by haloperidol interference. In conclusion, SalA could relieve CCI-induced cognitive impairment in rats, at least partly through the Drd2/Cryab/NF-κB pathway.

Extracellular vesicle-associated small heat shock proteins as therapeutic agents in neurodegenerative diseases and beyond

Increasing evidence points towards using extracellular vesicles (EVs) as a therapeutic strategy in neurodegenerative diseases such as multiple sclerosis, Parkinson's, and Alzheimer's disease. EVs are nanosized carriers that play an essential role in intercellular communication and cellular homeostasis by transporting an active molecular cargo, including a large variety of proteins. Recent publications demonstrate that small heat shock proteins (HSPBs) exhibit a beneficial role in neurodegenerative diseases. Moreover, it is defined that HSPBs target the autophagy and the apoptosis pathway, playing a prominent role in chaperone activity and cell survival. This review elaborates on the therapeutic potential of EVs and HSPBs, in particular HSPB1 and HSPB8, in neurodegenerative diseases. We conclude that EVs and HSPBs positively influence neuroinflammation, central nervous system (CNS) repair, and protein aggregation in CNS disorders. Moreover, we propose the use of HSPB-loaded EVs as advanced nanocarriers for the future development of neurodegenerative disease therapies.

Effect of Structural Changes Induced by Deletion of 54FLRAPSWF61 Sequence in αB-crystallin on Chaperone Function and Anti-Apoptotic Activity

Previously, we showed that the removal of the 54-61 residues from αB-crystallin (αBΔ54-61) results in a fifty percent reduction in the oligomeric mass and a ten-fold increase in chaperone-like activity. In this study, we investigated the oligomeric organization changes in the deletion mutant contributing to the increased chaperone activity and evaluated the cytoprotection properties of the mutant protein using ARPE-19 cells. Trypsin digestion studies revealed that additional tryptic cleavage sites become susceptible in the deletion mutant than in the wild-type protein, suggesting a different subunit organization in the oligomer of the mutant protein. Static and dynamic light scattering analyses of chaperone-substrate complexes showed that the deletion mutant has more significant interaction with the substrates than wild-type protein, resulting in increased binding of the unfolding proteins. Cytotoxicity studies carried out with ARPE-19 cells showed an enhancement in anti-apoptotic activity in αBΔ54-61 as compared with the wild-type protein. The improved anti-apoptotic activity of the mutant is also supported by reduced caspase activation and normalization of the apoptotic cascade components level in cells treated with the deletion mutant. Our study suggests that altered oligomeric assembly with increased substrate affinity could be the basis for the enhanced chaperone function of the αBΔ54-61 protein.

PP-1β and PP-2Aα modulate cAMP response element-binding protein (CREB) functions in aging control and stress response through de-regulation of αB-crystallin gene and p300-p53 signaling axis

The function of the transcription factor, cAMP response element‐binding protein (CREB), is activated through S133 phosphorylation by PKA and others. Regarding its inactivation, it is not well defined. cAMP response element‐binding protein plays an essential role in promoting cell proliferation, neuronal survival and the synaptic plasticity associated with long‐term memory. Our recent studies have shown that CREB is an important player in mediating stress response. Here, we have demonstrated that CREB regulates aging process through suppression of αB‐crystallin and activation of the p300‐p53‐Bak/Bax signaling axis. First, we determined that two specific protein phosphatases, PP‐1β and PP‐2Aα, can inactivate CREB through S133 dephosphorylation. Subsequently, we demonstrated that cells expressing the S133A‐CREB, a mutant mimicking constant dephosphorylation at S133, suppress CREB functions in aging control and stress response. Mechanistically, S133A‐CREB not only significantly suppresses CREB control of αB‐crystallin gene, but also represses CREB‐mediated activation of p53 acetylation and downstream Bak/Bax genes. cAMP response element‐binding protein suppression of αB‐crystallin and its activation of p53 acetylation are major molecular events observed in human cataractous lenses of different age groups. Together, our results demonstrate that PP‐1β and PP‐2Aα modulate CREB functions in aging control and stress response through de‐regulation of αB‐crystallin gene and p300‐p53‐Bax/Bak signaling axis, which regulates human cataractogenesis in the aging lens.

Aging-dependent loss of GAP junction proteins Cx46 and Cx50 in the fiber cells of human and mouse lenses accounts for the diminished coupling conductance

The homeostasis of the ocular lens is maintained by a microcirculation system propagated through gap junction channels. It is well established that the intercellular communications of the lens become deteriorative during aging. However, the molecular basis for this change in human lenses has not been well defined. Here, we present evidence to show that over 90% of Cx46 and Cx50 are lost in the fiber cells of normal human lenses aged 50 and above. From transparent to cataractous lenses, while Cx43 was upregulated, both Cx46 and Cx50 were significantly down-regulated in the lens epithelia. During aging of mouse lenses, Cx43 remained unchanged, but both Cx46 and Cx50 were significantly downregulated. Under oxidative stress treatment, mouse lenses develop in vitro cataractogenesis. Associated with this process, Cx43 was significantly upregulated, in contrast, Cx46 and Cx50 were sharply downregulated. Together, our results for the first time reveal that downregulation in Cx46 and Cx50 levels appears to be the major reason for the diminished coupling conductance, and the aging-dependent loss of Cx46 and Cx50 promotes senile cataractogenesis.

Quantitative proteomic analysis to capture the role of heat-accumulated proteins in moss plant acquired thermotolerance

At dawn of a scorching summer day, land plants must anticipate upcoming extreme midday temperatures by timely establishing molecular defences that can keep heat-labile membranes and proteins functional. A gradual morning pre-exposure to increasing sub-damaging temperatures induces heat-shock proteins (HSPs) that are central to the onset of plant acquired thermotolerance (AT). To gain knowledge on the mechanisms of AT in the model land plant Physcomitrium patens, we used label-free LC-MS/MS proteomics to quantify the accumulated and depleted proteins before and following a mild heat-priming treatment. High protein crowding is thought to promote protein aggregation, whereas molecular chaperones prevent and actively revert aggregation. Yet, we found that heat priming (HP) did not accumulate HSP chaperones in chloroplasts, although protein crowding was six times higher than in the cytosol. In contrast, several HSP20s strongly accumulated in the cytosol, yet contributing merely 4% of the net mass increase of heat-accumulated proteins. This is in poor concordance with their presumed role at preventing the aggregation of heat-labile proteins. The data suggests that under mild HP unlikely to affect protein stability. Accumulating HSP20s leading to AT, regulate the activity of rare and specific signalling proteins, thereby preventing cell death under noxious heat stress.

Therapeutic Potential of α-Crystallins in Retinal Neurodegenerative Diseases

The chaperone and anti-apoptotic activity of α-crystallins (αA- and αB-) and their derivatives has received increasing attention due to their tremendous potential in preventing cell death. While originally known and described for their role in the lens, the upregulation of these proteins in cells and animal models of neurodegenerative diseases highlighted their involvement in adaptive protective responses to neurodegeneration associated stress. However, several studies also suggest that chronic neurodegenerative conditions are associated with progressive loss of function of these proteins. Thus, while external supplementation of α-crystallin shows promise, their potential as a protein-based therapeutic for the treatment of chronic neurodegenerative diseases remains ambiguous. The current review aims at assessing the current literature supporting the anti-apoptotic potential of αA- and αB-crystallins and its potential involvement in retinal neurodegenerative diseases. The review further extends into potentially modulating the chaperone and the anti-apoptotic function of α-crystallins and the use of such functionally enhanced proteins for promoting neuronal viability in retinal neurodegenerative disease.

The E3 Ligase PIAS1 Regulates p53 Sumoylation to Control Stress-Induced Apoptosis of Lens Epithelial Cells Through the Proapoptotic Regulator Bax

Protein sumoylation is one of the most important post-translational modifications regulating many biological processes (Flotho A & Melchior F. 2013. Ann Rev. Biochem. 82:357–85). Our previous studies have shown that sumoylation plays a fundamental role in regulating lens differentiation (Yan et al., 2010. PNAS, 107(49):21034-9.; Gong et al., 2014. PNAS. 111(15):5574–9). Whether sumoylation is implicated in lens pathogenesis remains elusive. Here, we present evidence to show that the protein inhibitor of activated STAT-1 (PIAS1), a E3 ligase for sumoylation, is implicated in regulating stress-induced lens pathogenesis. During oxidative stress-induced cataractogenesis, expression of PIAS1 is significantly altered at both mRNA and protein levels. Upregulation and overexpression of exogenous PIAS1 significantly enhances stress-induced apoptosis. In contrast, silence of PIAS1 with CRISPR/Cas9 technology attenuates stress-induced apoptosis. Mechanistically, different from other cells, PIAS1 has little effect to activate JNK but upregulates Bax, a major proapoptotic regulator. Moreover, Bax upregulation is derived from the enhanced transcription activity of the upstream transcription factor, p53. As revealed previously in other cells by different laboratories, our data also demonstrate that PIAS1 promotes SUMO1 conjugation of p53 at K386 residue in lens epithelial cells and thus enhances p53 transcription activity to promote Bax upregulation. Silence of Bax expression largely abrogates PIAS1-mediated enhancement of stress-induced apoptosis. Thus, our results demonstrated that PIAS1 promotes oxidative stress-induced apoptosis through positive control of p53, which specifically upregulates expression of the downstream proapoptotic regulator Bax. As a result, PIAS1-promoted apoptosis induced by oxidative stress is implicated in lens pathogenesis.

Physiological and pathological functions of βB2-crystallins in multiple organs: a systematic review

Crystallins, the major constituent proteins of mammalian lenses, are significant not only for the maintenance of eye lens stability, transparency, and refraction, but also fulfill various physiopathological functions in extraocular tissues. βB2-crystallin, for example, is a multifunctional protein expressed in the human retina, brain, testis, ovary, and multiple tumors. Mutations in the βB2 crystallin gene or denaturation of βB2-crystallin protein are associated with cataracts, ocular pathologies, and psychiatric disorders. A prominent role for βB2-crystallins in axonal growth and regeneration, as well as in dendritic outgrowth, has been demonstrated after optic nerve injury. Studies in βB2-crystallin-null mice revealed morphological and functional abnormalities in testis and ovaries, indicating βB2-crystallin contributes to male and female fertility in mice. Interestingly, although pathogenic significance remains obscure, several studies identified a clear correlation between βB2 crystallin expression and the prognosis of patients with breast cancer, colorectal cancer, prostate cancer, renal cell carcinoma, and glioblastoma in the African American population. This review summarizes the physiological and pathological functions of βB2-crystallin in the eye and other organs and tissues and discusses findings related to the expression and potential role of βB2-crystallin in tumors.

Presence and activation of pro-inflammatory macrophages are associated with CRYAB expression in vitro and after peripheral nerve injury

BACKGROUND

Inflammation constitutes both positive and negative aspects to recovery following peripheral nerve injury. Following damage to the peripheral nervous system (PNS), immune cells such as macrophages play a beneficial role in creating a supportive environment for regrowing axons by phagocytosing myelin and axonal debris. However, a prolonged inflammatory response after peripheral nerve injury has been implicated in the pathogenesis of negative symptoms like neuropathic pain. Therefore, the post-injury inflammation must be carefully controlled to prevent secondary damage while allowing for regeneration. CRYAB (also known as alphaB-crystallin/HSPB5) is a small heat shock protein that has many protective functions including an immunomodulatory role in mouse models of multiple sclerosis, spinal cord injury, and stroke. Because its expression wanes and rebounds in the early and late periods respectively after PNS damage, and CRYAB null mice with sciatic nerve crush injury display symptoms of pain, we investigated whether CRYAB is involved in the immune response following PNS injury.

METHODS

Sciatic nerve crush injuries were performed in age-matched Cryab knockout (Cryab-/-) and wildtype (WT) female mice. Nerve segments distal to the injury site were processed by immunohistochemistry for macrophages and myelin while protein lysates of the nerves were analyzed for cytokines and chemokines using Luminex and enzyme-linked immunosorbent assay (ELISA). Peritoneal macrophages from the two genotypes were also cultured and polarized into pro-inflammatory or anti-inflammatory phenotypes where their supernatants were analyzed for cytokines and chemokines by ELISA and protein lysates for macrophage antigen presenting markers using western blotting.

RESULTS

We report that (1) more pro-inflammatory CD16/32+ macrophages are present in the nerves of Cryab-/- mice at days 14 and 21 after sciatic nerve crush-injury compared to WT counterparts, and (2) CRYAB has an immunosuppressive effect on cytokine secretion [interleukin (IL)-β, IL-6, IL-12p40, tumor necrosis factor (TNF)-α] from pro-inflammatory macrophages in vitro.

CONCLUSIONS

CRYAB may play a role in curbing the potentially detrimental pro-inflammatory macrophage response during the late stages of peripheral nerve regeneration.

Retinal Genomic Fabric Remodeling after Optic Nerve Injury

Glaucoma is a multifactorial neurodegenerative disease, characterized by degeneration of the retinal ganglion cells (RGCs). There has been little progress in developing efficient strategies for neuroprotection in glaucoma. We profiled the retina transcriptome of Lister Hooded rats at 2 weeks after optic nerve crush (ONC) and analyzed the data from the genomic fabric paradigm (GFP) to bring additional insights into the molecular mechanisms of the retinal remodeling after induction of RGC degeneration. GFP considers three independent characteristics for the expression of each gene: level, variability, and correlation with each other gene. Thus, the 17,657 quantified genes in our study generated a total of 155,911,310 values to analyze. This represents 8830x more data per condition than a traditional transcriptomic analysis. ONC led to a 57% reduction in RGC numbers as detected by retrograde labeling with 1,1'-dioctadecyl-3,3,3,3'-tetramethylindocarbocyanine perchlorate (DiI). We observed a higher relative expression variability after ONC. Gene expression stability was used as a measure of transcription control and disclosed a robust reduction in the number of very stably expressed genes. Predicted protein-protein interaction (PPI) analysis with STRING revealed axon and neuron projection as mostly decreased processes, consistent with RGC degeneration. Conversely, immune response PPIs were found among upregulated genes. Enrichment analysis showed that complement cascade and Notch signaling pathway, as well as oxidative stress and kit receptor pathway were affected after ONC. To expand our studies of altered molecular pathways, we examined the pairwise coordination of gene expressions within each pathway and within the entire transcriptome using Pearson correlations. ONC increased the number of synergistically coordinated pairs of genes and the number of similar profiles mainly in complement cascade and Notch signaling pathway. This deep bioinformatic study provided novel insights beyond the regulation of individual gene expression and disclosed changes in the control of expression of complement cascade and Notch signaling functional pathways that may be relevant for both RGC degeneration and remodeling of the retinal tissue after ONC.

Impact of chronic hyperglycemia on Small Heat Shock Proteins in diabetic rat brain

Small heat shock proteins (sHsps) are a family of proteins. Some are induced in response to multiple stimuli and others are constitutively expressed. They are involved in fundamental cellular processes, including protein folding, apoptosis, and maintenance of cytoskeletal integrity. Hyperglycemia created during diabetes leads to neuronal derangements in the brain. In this study, we investigated the impact of chronic hyperglycemia on the expression of sHsps and heat shock transcription factors (HSFs), solubility and aggregation of sHsps and amyloidogenic proteins, and their role in neuronal apoptosis in a diabetic rat model. Diabetes was induced in Sprague-Dawley rats with streptozotocin and hyperglycemia was maintained for 16 weeks. Expressions of sHsps and HSFs were analyzed by qRT-PCR and immunoblotting in the cerebral cortex. Solubility of sHsps and amyloidogenic proteins, including α-synuclein and Tau, was analyzed by the detergent soluble assay. Neuronal cell death was analyzed by TUNEL staining and apoptotic markers. The interaction of sHsps with amyloidogenic proteins and Bax was assessed using co-immunoprecipitation. Hyperglycemia decreased Hsp27 and HSF1, and increased αBC, Hsp22, and HSF4 levels at transcript and protein levels. Diabetes induced the aggregation of αBC, Hsp22, α-synuclein, and pTau, as their levels were higher in the insoluble fraction. Additionally, diabetes impaired the interaction of αBC with α-synuclein and pTau. Furthermore, diabetes reduced the interaction of αBC with Bax, which may possibly contribute to neuronal apoptosis. Together, these results indicate that chronic hyperglycemia induces differential responses of sHsps by altering their expression, solubility, interaction, and roles in apoptosis.

Novel Secreted Protein of Mycoplasma bovis MbovP280 Induces Macrophage Apoptosis Through CRYAB

Mycoplasma bovis causes important diseases and great losses on feedlots and dairy farms. However, there are only a few measures to control M. bovis-related diseases. As in other mycoplasma species, this is predominantly because the virulence related factors of this pathogen are largely unknown. Therefore, in this study, we aimed to identify novel virulence-related factors among the secreted proteins of M. bovis. Using bioinformatic tools to analyze its secreted proteins, we preliminarily predicted 39 secreted lipoproteins, and then selected 11 of them for confirmation based on SignalP scores >0.6 or SceP scores >0.8 and conserved domains. These 11 genes were cloned after gene modification based on the codon bias of Escherichia coli and expressed. Mouse antiserum to each recombinant protein was developed. A western blotting assay with these antisera confirmed that MbovP280 and MbovP475 are strongly expressed and secreted proteins, but only MbovP280 significantly reduced the viability of bovine macrophages (BoMac). In further experiments, MbovP280 induced the apoptosis of BoMac treated with both live M. bovis and MbovP280 protein. The conserved coiled-coil domain of MbovP280 at amino acids 210–269 is essential for its induction of apoptosis. Further, immunoprecipitation, mass spectrometry, and coimmunoprecipitation assays identified the anti-apoptosis regulator αB-crystallin (CRYAB) as an MbovP280-binding ligand. An αβ-crystallin knockout cell line BoMac-cryab⁻, Mbov0280-knockout M. bovis strain T9.297, and its complemented M. bovis strain CT9.297 were constructed and the apoptosis of BoMac-cryab⁻ induced by these strains was compared. The results confirmed that CRYAB is critical for MbovP280 function as an apoptosis inducer in BoMac. In conclusion, in this study, we identified MbovP280 as a novel secreted protein of M. bovis that induces the apoptosis of BoMac via its coiled-coil domain and cellular ligand CRYAB. These findings extend our understanding of the virulence mechanism of mycoplasmal species.

Proteome profiling of different rat brain regions reveals the modulatory effect of prolonged maternal separation on proteins involved in cell death-related processes

Background

Early-life stress in the form of maternal separation can be associated with alterations in offspring neurodevelopment and brain functioning. Here, we aimed to investigate the potential impact of prolonged maternal separation on proteomic profiling of prefrontal cortex, hippocampus and cerebellum of juvenile and young adult rats. A special attention was devoted to proteins involved in the process of cell death and redox state maintenance.

Methods

Long-Evans pups were separated from their mothers for 3 h daily over the first 3 weeks of life (during days 2–21 of age). Brain tissue samples collected from juvenile (22-day-old) and young adult (90-day-old) rats were used for label-free quantitative (LFQ) proteomic analysis. In parallel, selected oxidative stress markers and apoptosis-related proteins were assessed biochemically and by Western blot, respectively.

Results

In total, 5526 proteins were detected in our proteomic analysis of rat brain tissue. Approximately one tenth of them (586 proteins) represented those involved in cell death processes or regulation of oxidative stress balance. Prolonged maternal separation caused changes in less than half of these proteins (271). The observed alterations in protein expression levels were age-, sex- and brain region-dependent. Interestingly, the proteins detected by mass spectrometry that are known to be involved in the maintenance of redox state were not markedly altered. Accordingly, we did not observe any significant differences between selected oxidative stress markers, such as the levels of hydrogen peroxide, reduced glutathione, protein carbonylation and lipid peroxidation in brain samples from rats that underwent maternal separation and from the corresponding controls. On the other hand, a number of changes were found in cell death-associated proteins, mainly in those involved in the apoptotic and autophagic pathways. However, there were no detectable alterations in the levels of cleaved products of caspases or Bcl-2 family members. Taken together, these data indicate that the apoptotic and autophagic cell death pathways were not activated by maternal separation either in adolescent or young adult rats.

Conclusion

Prolonged maternal separation can distinctly modulate expression profiles of proteins associated with cell death pathways in prefrontal cortex, hippocampus and cerebellum of juvenile rats and the consequences of early-life stress may last into adulthood and likely participate in variations in stress reactivity.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40659-021-00327-5.

Function and Fiber-Type Specific Distribution of Hsp60 and αB-Crystallin in Skeletal Muscles: Role of Physical Exercise

Simple Summary

Skeletal muscle represents about 40% of the body mass in humans and it is a copious and plastic tissue, rich in proteins that are subject to continuous rearrangements. Physical exercise is considered a physiological stressor for different organs, in particular for skeletal muscle, and it is a factor able to stimulate the cellular remodeling processes related to the phenomenon of adaptation. All cells respond to various stress conditions by up-regulating the expression and/or activation of a group of proteins called heat shock proteins (HSPs). Although their expression is induced by several stimuli, they are commonly recognized as HSPs due to the first experiments showing their increased transcription after application of heat shock. These proteins are molecular chaperones mainly involved in assisting protein transport and folding, assembling multimolecular complexes, and triggering protein degradation by proteasome. Among the HSPs, a special attention needs to be devoted to Hsp60 and αB-crystallin, proteins constitutively expressed in the skeletal muscle, where they are known to be important in muscle physiopathology. Therefore, here we provide a critical update on their role in skeletal muscle fibers after physical exercise, highlighting the control of their expression, their biological function, and their specific distribution within skeletal muscle fiber-types.

Abstract

Skeletal muscle is a plastic and complex tissue, rich in proteins that are subject to continuous rearrangements. Skeletal muscle homeostasis can be affected by different types of stresses, including physical activity, a physiological stressor able to stimulate a robust increase in different heat shock proteins (HSPs). The modulation of these proteins appears to be fundamental in facilitating the cellular remodeling processes related to the phenomenon of training adaptations such as hypertrophy, increased oxidative capacity, and mitochondrial activity. Among the HSPs, a special attention needs to be devoted to Hsp60 and αB-crystallin (CRYAB), proteins constitutively expressed in the skeletal muscle, where their specific features could be highly relevant in understanding the impact of different volumes of training regimes on myofiber types and in explaining the complex picture of exercise-induced mechanical strain and damaging conditions on fiber population. This knowledge could lead to a better personalization of training protocols with an optimal non-harmful workload in populations of individuals with different needs and healthy status. Here, we introduce for the first time to the reader these peculiar HSPs from the perspective of exercise response, highlighting the control of their expression, biological function, and specific distribution within skeletal muscle fiber-types.

Nucleosomal association and altered interactome underlie the mechanism of cataract caused by the R54C mutation of αA-crystallin

BACKGROUND

αA-crystallin plays an important role in eye lens development. Its N-terminal domain is implicated in several important biological functions. Mutations in certain conserved arginine residues in the N-terminal region of αA-crystallin lead to cataract with characteristic cytoplasmic/nuclear aggregation of the mutant protein. In this study, we attempt to gain mechanistic insights into the congenital cataract caused by the R54C mutation in human αA-crystallin.

METHODS

We used several spectroscopic techniques to investigate the structure and function of the wild-type and R54CαA-crystallin. Immunoprecipitation, chromatin-enrichment followed by western blotting, immunofluorescence and cell-viability assay were performed to study the interaction partners, chromatin-association, stress-like response and cell-death caused by the mutant.

RESULTS

Although R54CαA-crystallin exhibited slight changes in quaternary structure, its chaperone-like activity was comparable to that of wild-type. When expressed in lens epithelial cells, R54CαA-crystallin exhibited a speckled appearance in the nucleus rather than cytoplasmic localization. R54CαA-crystallin triggered a stress-like response, resulting in nuclear translocation of αB-crystallin, disassembly of cytoskeletal elements and activation of caspase 3, leading to apoptosis. Analysis of the "interactome" revealed an increase in interaction of the mutant protein with nucleosomal histones, and its association with chromatin.

CONCLUSIONS

The study shows that alteration of "interactome" and nucleosomal association, rather than loss of chaperone-like activity, is the molecular basis of cataract caused by the R54C mutation in αA-crystallin.

GENERAL SIGNIFICANCE

The study provides a novel mechanism of cataract caused by a mutant of αA-crystallin, and sheds light on the possible mechanism of stress and cell death caused by such nuclear inclusions.

AlphaB-crystallin and breast cancer: role and possible therapeutic strategies

AlphaB-crystallin (HSPB5) is one of the most prominent and well-studied members of the small heat shock protein (sHsp) family. To date, it is known that this protein modulates significant cellular processes and therefore, it is not surprising that its deregulation is involved in various human pathologies, including cancer diseases. Despite the pathogenic significance of HSPB5 in cancer and its regulatory mechanism related to aggressiveness is poorly understood, several reports describe the association of breast carcinoma progression with HSPB5, whose expression is also considered an independent predictor of breast cancer metastasis to the brain. Indeed, numerous authors indicate HSPB5 as a new valuable biomarker for clinicopathological parameters and poor prognosis in breast cancer. Considering the cytoprotective, anti-apoptotic, pro-angiogenic, and pro-metastatic properties of the sHsps, it is not surprising that they are considered as promising targets for anticancer treatment, even though, at present, a deeper understanding of their mode of action is needed to allow the development of precise therapeutic interventions. Data on the direct inhibition of different sHsps demonstrate promising results in cancer pathologies; however, specific strategies against HSPB5 have not been considered. This review highlights the most relevant findings on HSPB5 and its role in breast cancer, as well as the possible strategies in using HSPB5 inhibition for therapeutic purposes.

The Brain Microenvironment Induces DNMT1 Suppression and Indolence of Metastatic Cancer Cells

Brain metastasis is an ineffective process, and many cancer cells enter into an indolent state following extravasation in the brain. Single cell RNA sequencing of melanoma brain metastases reveals that non-proliferating brain metastatic melanoma cells exhibit a pattern of gene expression associated with inhibition of DNA methyltransferase 1 (DNMT1). The brain microenvironment, specifically the combination of reactive astrocytes and mechanically soft surroundings, suppressed DNMT1 expression in various cancer types and caused cell cycle delay. Somewhat unexpectedly, we find that DNMT1 suppression not only induces cell cycle delay but also activates pro-survival signals in brain metastatic cancer cells, including L1CAM and CRYAB. Our results demonstrate that transcriptional changes triggered by DNMT1 suppression is a key step for cancer cells to survive in the brain microenvironment and that they also restrict cancer cell proliferation. The dual consequences of DNMT1 suppression can explain the persistence of indolent cancer cells in the brain microenvironment.

Transcriptomic analysis reveals the role of a peptide derived from CRYAB on the CoCl2-induced hypoxic HL-1 cardiomyocytes

Acute myocardial infarction (AMI) is a life-threatening disease that often results in heart failure. CRYAB, a small heat shock protein, has been shown to have cardioprotective effects against oxidative stress-induced apoptosis in AMI. Previously, we purified a peptide derived from CRYAB (LEDQFFGEH), which we named PDFC. In this study, we determined the function of PDFC on HL-1 cardiomyocytes and explored the mechanism underlying its function. A hypoxic myocardiocyte cell line was generated by stimulation of HL-1 mouse cardiac muscle cells with different concentrations of CoCl₂. Then, the hypoxic HL-1 cells were treated with the synthetic PDFC peptide, and cell proliferation, migration, and apoptosis were assessed to examine the effects of PDFC on HL-1 and hypoxic HL-1 cells. To examine the mechanism underlying the effects of PDFC on hypoxic cells, PDFC-treated hypoxic HL-1 cells were submitted for deep RNA sequencing. Finally, several differentially expressed genes in different pathways were selected for confirmation by RT-qPCR. Hypoxic myocardiocytes were generated by stimulating HL-1 cells with 800 µM CoCl₂ for 24 h, which significantly upregulated HIF-1α. PDFC at 200 µg/ml showed the most positive effects on cell viability. Although hypoxic HL-1 cells and PDFC-treated hypoxic HL-1 cells both showed lower viability and migration and higher levels of apoptosis than untreated HL-1 cells, compared to hypoxic HL-1 cells, PDFC-treated hypoxic HL-1 cells showed higher viability and migration and lower apoptosis. The deep sequencing showed that 812 genes were upregulated and 1946 genes were downregulated. Among these differentially expressed genes, 699 of the upregulated genes and 1488 of the downregulated genes were protein-coding genes. Gene ontology and pathway enrichment analysis showed that the downregulated genes were dominant and that the PI3K-Akt pathway was located in the center of the network. A protein-protein interaction network was constructed, and 892 nodes were determined. In PDFC-treated hypoxic HL-1 cells, Fn1, Pik3r5, and Creb5 were downregulated, while Insr, Bcl2, Mapk14, and Pten were upregulated when compared to the levels in hypoxic HL-1 cells. In conclusion, this study reveals the significant bioactive effect of the CRYAB-derived peptide, PDFC on cardiomyocytes and the underlying mechanism.

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.

Photobiomodulation Mediates Neuroprotection against Blue Light Induced Retinal Photoreceptor Degeneration

Potent neuroprotective effects of photobiomodulation with 670 nm red light (RL) have been demonstrated in several models of retinal disease. RL improves mitochondrial metabolism, reduces retinal inflammation and oxidative cell stress, showing its ability to enhance visual function. However, the current knowledge is limited to the main hypothesis that the respiratory chain complex IV, cytochrome c oxidase, serves as the primary target of RL. Here, we demonstrate a comprehensive cellular, molecular, and functional characterization of neuroprotective effects of 670 nm RL and 810 nm near-infrared light (NIRL) on blue light damaged murine primary photoreceptors. We show that respiratory chain complexes I and II are additional PBM targets, besides complex IV, leading to enhanced mitochondrial energy metabolism. Accordingly, our study identified mitochondria related RL- and NIRL-triggered defense mechanisms promoting photoreceptor neuroprotection. The observed improvement of mitochondrial and extramitochondrial respiration in both inner and outer segments is linked with reduced oxidative stress including its cellular consequences and reduced mitochondria-induced apoptosis. Analysis of regulatory mechanisms using gene expression analysis identified upregulation α-crystallins that indicate enhanced production of proteins with protective functions that point to the rescued mitochondrial function. The results support the hypothesis that energy metabolism is a major target for retinal light therapy.

Zeta-crystallin: a moonlighting player in cancer

Crystallins were firstly found as structural proteins of the eye lens. To this family belong proteins, such as ζ-crystallin, expressed ubiquitously, and endowed with enzyme activity. ζ-crystallin is a moonlighting protein endowed with two main different functions: (1) mRNA binding with stabilizing activity; (2) NADPH:quinone oxidoreductase. ζ-crystallin has been clearly demonstrated to stabilize mRNAs encoding proteins involved in renal glutamine catabolism during metabolic acidosis resulting in ammoniagenesis and bicarbonate ion production that concur to compensate such condition. ζ-crystallin binds also mRNAs encoding for antiapoptotic proteins, such as Bcl-2 in leukemia cells. On the other hand, the physiological role of its enzymatic activity is still elusive. Gathering research evidences and data mined from public databases, we provide a framework where all the known ζ-crystallin properties are called into question, making it a hypothetical pivotal player in cancer, allowing cells to hijack or subjugate the acidity response mechanism to increase their ability to resist oxidative stress and apoptosis, while fueling their glutamine addicted metabolism.

Biomarkers in retinoblastoma

Retinoblastoma (RB) is the most common intraocular malignancy of childhood caused by inactivation of the Rb genes. The prognosis of RB is better with an earlier diagnosis. Many diagnostic approaches and appropriate clinical treatments have been developed to improve clinical outcomes. However, limitations exist when utilizing current methods. Recently, many studies have identified identify new RB biomarkers which can be used in diagnosis, as prognostic indicators and may contribute to understanding the pathogenesis of RB and help determine specific treatment strategies. This review focuses on recent advances in the discovery of RB biomarkers and discusses their clinical utility and challenges from areas such as epigenetics, proteomics and radiogenomics.

Oxidative stress-induced KLF4 activates inflammatory response through IL17RA and its downstream targets in retinal pigment epithelial cells

Age-related macular degeneration (AMD) is a leading cause of irreversible blindness worldwide. Oxidative stress (OS), inflammation and genetics are considered the key pathogenic factors contributing to AMD development. Recent evidence shows the pro-inflammatory interleukin 17 (IL17) signaling is activated in AMD patients and promotes disease pathogenesis. However, the interplay between OS and IL17 signaling, and the regulatory mechanism of IL17 pathway are largely unknown. OS-induced retinal pigment epithelial cell (RPE) damage causes both the initial pathogenesis of AMD and secondary degeneration of rods and cones. Healthy RPE is essential for ocular immune privilege, however, damaged RPE cells can activate inflammatory response. In the present study, we identified IL17RA, the principle receptor of IL17 signaling, is one of the most upregulated inflammatory genes in human RPE cells upon OS exposure. The prominent increase of IL17RA was also observed in RPE and retina of an AMD-like mouse model. Knockdown of IL17RA in RPE cells prevented OS-induced RPE cell apoptosis and reduced the inflammatory response in both RPE and macrophages. Furthermore, we found that transcription factor KLF4 directly activates IL17RA expression, therefore, promotes the production of IL1β and IL8 in an IL17RA-dependent manner. In addition, the mRNA level of KLF4 isoform 2 was positively correlated with that of IL17RA in AMD patients. Together, our study demonstrates an unrevealed relationship between IL17RA and OS, and a new regulatory mechanism of IL17RA by KLF4 in RPE cells. These findings suggest that inhibition of IL17RA as a new potential therapeutic target for AMD through RPE protection and inflammatory suppression upon OS exposure.

Alpha B-Crystallin Overexpression Protects Oligodendrocyte Precursor Cells Against Oxidative Stress-Induced Apoptosis Through the Akt Pathway

Alpha B-crystallin (aBC), a member of the small heat shock protein family, is expressed in mature oligodendrocytes (mOLs), but not in oligodendrocyte precursor cells (OPCs). Our previous study found that the survival rate of OPCs was lower than that of mOLs under oxidative stress, suggesting that aBC may play a protective role in mOLs. In the present study, we investigated the effects of aBC overexpression on oxidative stress-induced cell injury in OPCs and examined the underlying mechanisms. We observed that the survival rates of aBC-overexpressed OPCs were significantly higher than those of control cells under oxidative stress induced by hydrogen peroxide. Akt activities were significantly suppressed by oxidative stress in control OPCs, but not in aBC-overexpressed OPCs. The expressions of Bax and cleaved caspase-3 were decreased, whereas Bcl-2 expression was increased in aBC-overexpressed OPCs under oxidative stress. These findings suggest that low Akt activity in OPCs due to aBC deficiency may cause high susceptibility of OPCs to oxidative stress. The findings may provide new insights into the implication of OPCs in demyelinating diseases.

CRYAB promotes osteogenic differentiation of human bone marrow stem cells via stabilizing β-catenin and promoting the Wnt signalling

Objectives

The osteogenesis differentiation of human bone marrow stem cells (BMSCs) is essential for bone formation and bone homeostasis. In this study, we aim to elucidate novel molecular targets for bone metabolism diseases.

Materials and methods

The dataset GSE80614 which includes mRNA expression profile during BMSCs osteogenic differentiation was obtained from the GEO database (https://www.ncbi.nlm.nih.gov/geo/). The osteogenic differentiation of BMSCs was measured by ALP staining, AR staining and expression of osteogenic markers in vitro. For in vivo assay, we seeded BMSCs onto beta‐tricalcium phosphate (β‐TCP) and transplanted them into muscle pockets of nude mice. Luciferase assay, co‐immunoprecipitation assay and in vitro ubiquitination assay were carried out to investigate the molecular mechanism.

Results

We found that α‐B‐crystallin (CRYAB) expression was elevated during the process of BMSCs osteogenic differentiation. Further studies showed that upregulation of CRYAB significantly enhanced the osteogenic differentiation, while downregulation of CRYAB suppressed it. CRYAB regulated BMSCs osteogenic differentiation mainly through the canonical Wnt/β‐catenin signalling. In addition, we found that CRYAB could physically interact with β‐catenin and protect it from ubiquitination and degradation, which stabilized β‐catenin and promoted the Wnt signalling.

Conclusions

The present study provides evidences that CRYAB is an important regulator of BMSCs osteogenic differentiation by protecting β‐catenin from ubiquitination and degradation and promoting the Wnt signalling. It may serve as a potential therapeutic target for diseases related to bone metabolism.

Role of Heat Shock Proteins in Glaucoma

Glaucoma, one of the most common causes of blindness worldwide, is a multifactorial neurodegenerative disease characterized by damage of retinal ganglion cells and optic nerve degeneration. However, the exact mechanism leading to glaucoma is still not understood. Evidences suggest an immunological involvement in the pathogenesis. Among other immune responses, altered autoantibody patterns were found in glaucoma patients. Especially elevated antibody levels against heat shock proteins (HSPs), like HSP27 or HSP60, were identified. In an animal model, an immunization with these HSPs induced a pressure-independent retinal ganglion cell degeneration and axon loss, hence mimicking glaucoma-like damage. In addition, development of autoreactive antibodies, as well as a glia and T-cell activation, were described in these animals. Recently, we noted that intravitreal HSP27 injection likewise led to a degeneration of retinal ganglion cells and their axons. Therefore, HSP27 might have a direct damaging effect on retinal cells, and might play a key role in glaucoma.

The Sumoylation Modulated Tumor Suppressor p53 Regulates Cell Cycle Checking Genes to Mediate Lens Differentiation

PURPOSE

The tumor suppressor p53 is a master regulator of apoptosis and also plays a key role in cell cycle checking. In our previous studies, we demonstrated that p53 directly regulates Bak in mouse JB6 cells and that p53-Bak signaling axis plays an important role in mediating EGCG-induced apoptosis. Furthermore, we have recently demonstrated that the same p53-Bak apoptotic signaling axis executes an essential role in regulating lens cell differentiation. In addition, we have also shown that p53 controls both transcription factors, C-Maf and Prox-1 as well as lens crystallin genes, αA, β- and γ-crystallins. Here, we have examined whether p53 also regulates other known target genes during its modulation of lens differentiation. The human and mouse lens epithelial cells, FHL124 and αTN4-1 were cultured in Dulbecco's modified Eagle's medium (DMEM) containing 10% fetal bovine serum (FBS) and 1% Penicillin-Streptomycin.

METHODS

Mice used in this study were handled in compliance with the "Protocol for the Care and Use of Laboratory Animals" (Sun Yat-sen University). Adult mice were used for the collection of lens cells. These samples were used for extraction of total proteins. A total of 32 embryonic mice {8 at 14.5 ED, 8 at 17.5 ED and 8 newborns for wild type} were used for immunohistochemistry, which were used for co-localization study. The mRNA levels were analysed with qRT-PCR. The protein levels were determined with western blot analysis and quantitated with Image J.

RESULTS

Immunohistochemistry revealed that both the cell cycle checking genes, p21 and Gadd45α and the apoptotic genes, Bcl-2 and PUMA, display developmental changes associated with p53 during mouse lens development. Knockdown of p53 in the mouse lens epithelial cells caused inhibition of lens differentiation. Associated with this inhibition, the cell cycle genes displayed significant downreglation, the apoptotic genes was also attenuated but to a much less degree. In addition, we found that bFGF can induce dose-dependent upregulation of the upstream kinases, CHK1/2 and ERK1/2, both known to phosphorylate p53 and activate the later. Furthermore, We showed that in both developing lens and human lens epithelial cells, p53 can be co-localized with the catalytic subunit of the protein phoshphatase-1 (PP-1), suggesting that PP-1 regulates p53 phosphorylation status both in vivo and in vitro.

CONCLUSION

Taken together, our results suggest that during mouse lens development, p53 activity is regulated by ERK and CHK kinases-mediated activation, and by PP-1-mediated inactivation. p53 can regulate multiple groups of genes to mediate lens differentiation.

Analysis of the Differential Expression Patterns of Sumoylation Enzymes E1, E2 and E3 in Ocular Cell Lines

PURPOSE

Protein sumoylation is a well established regulatory mechanism to control many cellular processes such as chromatin structure dynamics, transcriptional regulation of gene expression, cell proliferation and differentiation, cell transformation and carcinogenesis, autophagy and senescence. In the vertebrate vision system, we and others have revealed that sumoylation plays important roles in regulating differentiation of several ocular tissues during eye development. To further elucidate the functional mechanisms of sumoylation, in vitro assay systems are needed. Currently, the five major cell lines including αTN4-1, FHL124, HLE, N/N1003A and ARPE-19 have been extensively used to test the biochemical and molecular aspects of normal vision physiology and various disease processes. Thus, we conducted the study on the expression patterns of the three types of sumoylation enzymes, the activating enzymes SAE1 and UBA2, the conjugating enzyme UBC9, and the ligating enzymes such as RanBP2 and PIAS1 in these ocular cell lines.

METHODS

The 5 major ocular cell lines were cultured in Dulbecco's modified Eagle's medium (DMEM) containing fetal bovine serum (FBS) or rabbit serum (RBS) and 1% Penicillin- Streptomycin. The mRNA levels were analysed with qRT-PCR. The protein levels were determined with western blot analysis and quantitated with Image J.

RESULTS

we have obtained the following results: 1) For the mRNAs encoding E1 SAE1 and UBA2, E2 UBC9 and E3 PIAS1, the highest level of expression was observed in αTN4-1 cells; For the mRNA encoding RanBP2, the highest level of expression was detected in N/N1003A cells; 2) In contrast to the mRNA expression patterns, a similar level of the SAE1 protein was observed in the all five cell lines, and so is true with UBA2 protein in all cells except for N/N1003A where over fourfold of enrichment in UBA2 protein was observed compared with other cell lines; 3) A similar level of UBC9 protein was also detected in all cells except for N/N1003A where more than one-fold of decrease in UBC9 level was found compared with other cell lines; 4) For E3 ligases, we did not identify the regular PIAS1 band in N/N1003A cells, the remaining cells have a level of PIAS1 with difference of less than 0.6-fold; all cells except for FHL124 cells have a similar level of RanBP2, and a 70% drop in RanBP2 was observed in FHL124 cell.

CONCLUSIONS

Our determination of the differential expression patterns of the three types of sumoylation enzymes in the 5 ocular cell lines help to understand sumoylation functions in vertebrate eye.

Moonlighting Proteins and Cardiopathy in the Spatial Response of MCF-7 Breast Cancer Cells to Tamoxifen

BACKGROUND

The purpose of this study is to apply quantitative high-throughput proteomics methods to investigate dynamic aspects of protein changes in nucleocytoplasmic distribution of proteins and of total protein abundance for MCF-7 cells exposed to tamoxifen (Tam) in order to reveal the agonistic and antagonistic roles of the drug.

EXPERIMENTAL DESIGN

The MS-based global quantitative proteomics with the analysis of fractions enriched in target subcellular locations is applied to measure the changes in total abundance and in the compartmental abundance/distribution between the nucleus and cytoplasm for several thousand proteins differentially expressed in MCF-7 cells in response to Tam stimulation.

RESULTS

The response of MCF-7 cells to the Tam treatment shows significant changes in subcellular abundance rather than in their total abundance. The bioinformatics study reveals the relevance of moonlighting proteins and numerous pathways involved in Tam response of MCF-7 including some of which may explain the agonistic and antagonistic roles of the drug.

CONCLUSIONS

The results indicate possible protective role of Tam against cardiovascular diseases as well as its involvement in G-protein coupled receptors pathways that enhance breast tissue proliferation.

Moonlighting Proteins and Cardiopathy in the Spatial Response of MCF-7 Breast Cancer Cells to Tamoxifen

BACKGROUND

The purpose of this study is to apply quantitative high-throughput proteomics methods to investigate dynamic aspects of protein changes in nucleocytoplasmic distribution of proteins and of total protein abundance for MCF-7 cells exposed to tamoxifen (Tam) in order to reveal the agonistic and antagonistic roles of the drug.

EXPERIMENTAL DESIGN

The MS-based global quantitative proteomics with the analysis of fractions enriched in target subcellular locations is applied to measure the changes in total abundance and in the compartmental abundance/distribution between the nucleus and cytoplasm for several thousand proteins differentially expressed in MCF-7 cells in response to Tam stimulation.

RESULTS

The response of MCF-7 cells to the Tam treatment shows significant changes in subcellular abundance rather than in their total abundance. The bioinformatics study reveals the relevance of moonlighting proteins and numerous pathways involved in Tam response of MCF-7 including some of which may explain the agonistic and antagonistic roles of the drug.

CONCLUSIONS

The results indicate possible protective role of Tam against cardiovascular diseases as well as its involvement in G-protein coupled receptors pathways that enhance breast tissue proliferation.

Small Heat Shock Proteins, Amyloid Fibrils, and Nicotine Stimulate a Common Immune Suppressive Pathway with Implications for Future Therapies

The α7 nicotinic acetylcholine receptor (α7nAChR) is central to the anti-inflammatory function of the vagus nerve in a physiological mechanism termed the inflammatory reflex. Studies on the inflammatory reflex have been instrumental for the current development of the field of bioelectronic medicine. An independent investigation of the biological role of αB-crystallin (HspB5), the most abundant gene transcript present in active multiple sclerosis lesions in human brains, also led to α7nAChR. Induction of experimental autoimmune encephalomyelitis (EAE) in HspB5^-/- mice results in greater paralytic signs, increased levels of proinflammatory cytokines, and T-lymphocyte activation relative to wild-type animals. Administration of HspB5 was therapeutic in animal models of multiple sclerosis, retinal and cardiac ischemia, and stroke. Structure-activity studies established that residues 73-92 were as potent as the parent protein, but only when it formed amyloid fibrils. Amyloid fibrils and small heat shock proteins (sHsps) selectively bound α7nAChR on peritoneal macrophages (MΦs) and B lymphocytes, converting the MΦs to an immune suppressive phenotype and mobilizing the migration of both cell types from the peritoneum to secondary lymph organs. Here, we review multiple aspects of this work, which may be of interest for developing future therapeutic approaches for multiple sclerosis and other disorders.

Progression of the role of CRYAB in signaling pathways and cancers

CRYAB is a member of the small heat shock protein family, first discovered in the lens of the eye, and involved in various diseases, such as eye and heart diseases and even cancers, for example, breast cancer, lung cancer, prostate cancer, and ovarian cancer. In addition, CRYAB proteins are involved in a variety of signaling pathways including apoptosis, inflammation, and oxidative stress. This review summarizes the recent progress concerning the role of CRYAB in signaling pathways and diseases. Therefore, the role of CRYAB in signaling pathways and cancers is urgently needed. This article reviews the regulation of CRYAB in the apoptotic inflammatory signaling pathway and its role in cancers progression and as a key role in anti-cancer therapy targeting CRYAB in an effort to improve outcomes for patients with metastatic disease.

Recombination and identification of human alpha B-crystallin

AIM

To recombine the human alpha B-crystallin (αB-crystallin) using gene cloning technology and prokaryotic expression vector and confirm the biological activity of recombinant human αB-crystallin.

METHODS

Cloning the human αB-crystallin cDNA according to the nucleotide sequence of the human αB-crystallin, constructing the pET-28/CRYAB prokaryotic expression plasmid by restriction enzyme digestion method, and stably expressing transformed into the Escherichia coli (E. coli) DH5 alpha. The recombinant human αB-crystallin was purified by Q sepharose. By enzyme digestion analysis, Western blotting and sequencing, the recombinant human αB-crystallin was identified and the activity of its molecular protein was detected.

RESULTS

Compared with the gene bank (GeneBank), the cloned human sequence of human αB-crystallin cDNA has the same open reading frame. Identification and sequencing of the cloned human αB-crystallin cDNA in prokaryotic expression vector confirmed the full length sequence, and the vector was constructed successfully. The E. coli containing plasmid pET-28/CRYAB induced by isopropyl-β-D-thiogalactoside successfully expressed the human αB-crystallin. Insulin confirmed that the recombinant human αB-crystallin has a molecular chaperone activity.

CONCLUSION

The prokaryotic expression vector pET-28/CRYAB of recombinant human αB-crystallin is successfully constructed, and the recombinant human αB-crystallin with molecular chaperone activity is obtained, which lay a foundation for the research and application of the recombinant human αB-crystallin and its chaperone activity.

Preclinical stress originates in the rat optic nerve head during development of autoimmune optic neuritis

Optic neuritis is a common manifestation of multiple sclerosis, an inflammatory demyelinating disease of the CNS. Although it is the presenting symptom in many cases, the initial events are currently unknown. However, in the earliest stages of autoimmune optic neuritis in rats, pathological changes are already apparent such as microglial activation and disturbances in myelin ultrastructure of the optic nerves. αB‐crystallin is a heat‐shock protein induced in cells undergoing cellular stress and has been reported to be up‐regulated in both multiple sclerosis and its animal model, experimental autoimmune encephalomyelitis. Therefore, we wished to investigate the timing and localization of its expression in autoimmune optic neuritis. Although loss of oligodendrocytes was not observed until the later disease stages accompanying immune cell infiltration and demyelination, an increase in oligodendrocyte αB‐crystallin was observed during the preclinical stages. This was most pronounced within the optic nerve head and was associated with areas of IgG deposition. Since treatment of isolated oligodendrocytes with sera from myelin oligodendrocyte glycoprotein (MOG)‐immunized animals induced an increase in αB‐crystallin expression, as did passive transfer of sera from MOG‐immunized animals to unimmunized recipients, we propose that the partially permeable blood–brain barrier of the optic nerve head may present an opportunity for blood‐borne components such as anti‐MOG antibodies to come into contact with oligodendrocytes as one of the earliest events in disease development.

Silver nanoparticles affect lens rather than retina development in zebrafish embryos

Silver nanoparticles (AgNPs) have been reported to inhibit specification and differentiation of erythroid cells, chromatophores, and myofibrils during zebrafish embryogenesis. However, the knowledge of biological effects of AgNPs on eye development, especially on lens development is scarce. In this study, embryos were exposed to or injected with 0.4 mg/L AgNPs, and the results indicate that no obvious morphological changes in eye formation were observed in the stressed embryos compared to the controls. However, clefts and vacuoles were observed in lens of embryos from AgNPs stressed group. Additionally, the down-regulated expressions of different lens crystallin isoform genes and the normal expression of retinal genes were observed in AgNPs stressed embryos, suggesting AgNPs might inhibit the development of lens rather than the development of retina in zebrafish embryos. Moreover, no obvious cell apoptosis was observed, but normal nuclear DNA and RNA export was observed in lens cells. Together, the data in this study reveal that AgNPs damage the development of lens rather than retina resulting in eye abnormalities via some unknown mechanisms rather than via triggering cells apoptosis or blocking nuclear DNA or RNA export.

Localization of αA-Crystallin in Rat Retinal Müller Glial Cells and Photoreceptors

Transparent cells in the vertebrate optical tract, such as lens fiber cells and corneal epithelium cells, have specialized proteins that somehow permit only a low level of light scattering in their cytoplasm. It has been shown that both cell types contain (1) beaded intermediate filaments as well as (2) α-crystallin globulins. It is known that genetic and chemical alterations to these specialized proteins induce cytoplasmic opaqueness and visual complications. Crystallins were described previously in the retinal Müller cells of frogs. In the present work, using immunocytochemistry, fluorescence confocal imaging, and immuno-electron microscopy, we found that αA-crystallins are present in the cytoplasm of retinal Müller cells and in the photoreceptors of rats. Given that Müller glial cells were recently described as "living light guides" as were photoreceptors previously, we suggest that αA-crystallins, as in other highly transparent cells, allow Müller cells and photoreceptors to minimize intraretinal scattering during retinal light transmission.