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Background: Lupus nephritis (LN) is an inflammatory disease of the kidneys affecting patients with systemic lupus erythematosus. Current immunosuppressive and cytotoxic therapies are associated with serious side effects and fail to protect 20-40% of LN patients from end-stage renal disease. In this study, we investigated whether a small heat shock protein, HSPB5, can reduce kidney inflammation and the clinical manifestations of the disease in NZB/W F1 mice. Furthermore, we investigated whether HSPB5 can enhance the effects of methylprednisolone, a standard-of-care drug in LN, in an endotoxemia mouse model., Methods: NZB/W F1 mice were treated with HSPB5, methylprednisolone, or vehicle from 23 to 38 weeks of age. Disease progression was evaluated by weekly proteinuria scores. At the end of the study, the blood, urine, spleens, and kidneys were collected for the assessment of proteinuria, blood urea nitrogen, kidney histology, serum IL-6 and anti-dsDNA levels, immune cell populations, and their phenotypes, as well as the transcript levels of proinflammatory chemokine/cytokines in the kidneys. HSPB5 was also evaluated in combination with methylprednisolone in a lipopolysaccharide-induced endotoxemia mouse model; serum IL-6 levels were measured at 24 h post-endotoxemia induction., Results: HSPB5 significantly reduced terminal proteinuria and BUN and substantially improved kidney pathology. Similar trends, although to a lower extent, were observed with methylprednisolone treatment. Serum IL-6 levels and kidney expression of BAFF, IL-6, IFNγ, MCP-1 (CCL2), and KIM-1 were reduced, whereas nephrin expression was significantly preserved compared to vehicle-treated mice. Lastly, splenic Tregs and Bregs were significantly induced with HSPB5 treatment. HSPB5 in combination with methylprednisolone also significantly reduced serum IL-6 levels in endotoxemia mice., Conclusions: HSPB5 treatment reduces kidney inflammation and injury, providing therapeutic benefits in NZB/W F1 mice. Given that HSPB5 enhances the anti-inflammatory effects of methylprednisolone, there is a strong interest to develop HSBP5 as a therapeutic for the treatment of LN., (© 2022. The Author(s).)

Myocardial fibrosis, a common pathological manifestation of cardiac remodeling (CR), often leads to heart failure (HF) and even death. The underlying molecular mechanism of the role of TRIM33 in Ang II-induced myocardial fibrosis is not fully understood. We found that TRIM33 was specifically upregulated in CFs and myocardial tissue after Ang II stimulation. Adult mice induced by Ang II were used as in vivo models, and Ang II-induced neonatal mouse primary cardiac fibroblasts (CFs) were used as in vitro models. The level of CF fibrosis in vitro was assessed by CF proliferation, migration, activation and extracellular matrix (ECM) synthesis. In addition, Masson staining, the heart weight/body weight (HW/BW) ratio and echocardiography were used to evaluate the in vivo effect of TRIM33. TRIM33 expression was specifically upregulated in CFs and myocardial tissue after Ang II stimulation. In in vitro experiments, we found that TRIM33 knockdown promoted Ang II-induced CF proliferation, while TRIM33 overexpression weakened Ang II-induced CF proliferation, migration, activation and collagen synthesis. Mechanistically, we showed that TRIM33, negatively regulated by HSPB5, mediated its antifibrotic effect by inhibiting the activation of TGF-β1 and its downstream genes, Smad3 and Smad4. Finally, TRIM33 overexpression suppressed fibrosis and promoted cardiac repair and functional recovery in Ang II-induced mice. Our results clearly establish that TRIM33 limits cardiac fibrosis by hindering CF proliferation, migration, activation and collagen synthesis. Enhancing these beneficial functions of TRIM33 by a targeting vector might be a novel therapeutic strategy for CR.

HSPB5 (heat shock protein B5), also known as αB-crystallin, is one of the most widespread and populous of the ten human small heat shock proteins (sHsps). Over the past decades, extensive research has been conducted on HSPB5. However, few studies have statistically analyzed these publications. Herein, we conducted a bibliometric analysis to track the global research trend and current development status of HSPB5 research from the Web of Science Core Collection (WoSCC) database between 1985 and 2020. Our results demonstrate that 1220 original articles cited 54,778 times in 391 scholarly journals were published. Visualization analyses reveal that the Journal of Biological Chemistry was the most influential journal with 85 articles. The USA dominated this field with 520 publications (42.62%), followed by Japan with 149 publications (12.21%), and Kato contributed the largest number of publications. Most related publications were published in journals focusing on biochemistry molecular biology, cell biology, neurosciences neurology, and ophthalmology. In addition, keyword co-occurrence analyses identify three predominant research topics: expression of HSPB5, chaperone studies for HSPB5, and pathological studies of HSPB5. This study provides valuable guidance for researchers and leads to collaborative opportunities between diverse research interests to be integrated for HSPB5 research., (© 2021. Cell Stress Society International.)

Background: HSPB5 is an ATP-independent molecular chaperone that is induced by heat shock or other proteotoxic stresses. HSPB5 is cytoprotective against stress both intracellularly and extracellularly. It acts as a potential therapeutic candidate in ischemia-reperfusion and neurodegenerative diseases., Results: In this paper, we constructed a recombinant plasmid that expresses and extracellularly secrets a HSPB5-Fc fusion protein (sHSPB5-Fc) at 0.42 μg/ml in CHO-K1 cells. This sHSPB5-Fc protein contains a Fc-tag at the C-terminal extension of HSPB5, facilitating protein-affinity purification. Our study shows that sHSPB5-Fc inhibits heat-induced aggregation of citrate synthase in a time and dose dependent manner in vitro. Administration of sHSPB5-Fc protects lens epithelial cells against cisplatin- or UVB-induced cell apoptosis. It also decreases GFP-Htt ex1 -Q74 insolubility, and reduces the size and cytotoxicity of GFP-Htt ex1 -Q74 aggregates in PC-12 cells., Conclusion: This recombinant sHSPB5-Fc exhibits chaperone activity to protect cells against proteotoxicity.

Oxidative stress is one of the major and continuous stresses, an organism encounters during its lifetime. Tissues such as the brain, liver and muscles are more prone to damage by oxidative stress due to their metabolic activity, differences in physiological and adaptive processes. One of the defence mechanisms against continuous oxidative stress is a set of small heat shock proteins. αB-Crystallin/HSPB5, a small heat shock protein, gets upregulated under stress and acts as a molecular chaperone. In addition to acting as a molecular chaperone, HSPB5 is shown to have a role in other cytoprotective functions such as inhibition of apoptosis, prevention of oxidative stress and stabilisation of cytoskeletal system. Such protection in vivo, at the organism level, particularly in a tissue-dependent manner, has not been investigated. We have expressed HSPB5 in fat body (liver), neurons and specifically in dopaminergic and motor neurons in Drosophila and investigated its protective effect against paraquat-induced oxidative stress. We observed that expression of HSPB5 in neurons and fat body confers protection against paraquat-induced oxidative stress. Expression in dopaminergic neurons showed a higher protective effect. Our results clearly establish the protective ability of HSPB5 in vivo; the extent of protection, however, varies depending on the tissue in which it is expressed. Interestingly, neuronal expression of HSPB5 resulted in an improvement in negative geotropic behaviour, whereas specific expression in muscle tissue did not show such a beneficial effect.

Background: αB-crystallin is a promiscuous protein involved in numerous cell functions. Mutations in CRYAB have been found in patients with different pathological phenotypes that are not properly understood. Patients can present different diseases like cataracts, muscle weakness, myopathy, cardiomyopathy, respiratory insufficiency or dysphagia, but also a variable combination of these pathologies has been found. These mutations can show either autosomal dominant or recessive mode of inheritance and variable penetrance and expressivity. This is the first report of congenital cataracts and myopathy described in childhood due to a CRYAB mutation with autosomal dominant mode of inheritance., Methods: The whole exome sequence was subjected to phenotype-driven analysis and a novel variant in CRYAB was detected: c.514delG, p.(Ala172ProfsTer14). The mutation was located in the C-terminal domain of the protein, which is essential for chaperone activity. The deduced protein was analyzed searching for alterations of the relevant physico-chemical properties described for this domain. A muscle biopsy was also tested for CRYAB with immunohistochemical and histoenzymatic techniques., Results: CRYAB displayed a mild immunoreactivity in the subsarcolemmal compartment with no pathological sarcoplasmic accumulation. It agrees with an alteration of the physico-chemical properties predicted for the C-terminal domain: hydrophobicity, stiffness, and isomerization., Conclusions: The described mutation leads to elongation of the protein at the carboxi-terminal domain (CTD) with altered properties, which are essential for solubility and activity. It suggests that can be the cause of the severe conditions observed in this patient., (© 2020 The Authors. Molecular Genetics & Genomic Medicine published by Wiley Periodicals LLC.)

Small heat-shock proteins (sHSPs) are ATP-independent molecular chaperones that interact with partially unfolded proteins, preventing their aberrant aggregation, thereby exhibiting a chaperone-like activity. Dynamics of the quaternary structure plays an important role in the chaperone-like activity of sHSPs. However, relationship between the dynamic structure of sHSPs and their chaperone-like activity remains insufficiently characterized. Many factors (temperature, ions, a target protein, crowding etc.) affect the structure and activity of sHSPs. The least studied is an effect of crowding on sHSPs activity. In this work the chaperone-like activity of HSPB5 was quantitatively characterized by dynamic light scattering using two test systems, namely test systems based on heat-induced aggregation of muscle glycogen phosphorylase b (Ph b ) at 48 °C and dithiothreitol-induced aggregation of α-lactalbumin at 37 °C. Analytical ultracentrifugation was used to control the oligomeric state of HSPB5 and target proteins. The possible anti-aggregation functioning of suboligomeric forms of HSPB5 is discussed. The effect of crowding on HSPB5 anti-aggregation activity was characterized using Ph b as a target protein. The duration of the nucleation stage was shown to decrease with simultaneous increase in the relative rate of aggregation of Ph b in the presence of HSPB5 under crowded conditions. Crowding may subtly modulate sHSPs activity.

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 H 2 O 2 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 H 2 O 2 "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., Competing Interests: Declaration of competing interest The authors declare that there are not conflicts of interest., (Copyright © 2020. Published by Elsevier Inc.)

Small heat shock proteins (sHSPs) delay protein aggregation in an ATP-independent manner by interacting with client proteins that are in states susceptible to aggregation, including destabilized states related to cellular stress. Up-regulation of sHSPs under stress conditions supports their critical role in cellular viability. Widespread distribution of sHSPs in most organisms implies conservation of function, but it remains unclear whether sHSPs implement common or distinct mechanisms to delay protein aggregation. Comparisons among various studies are confounded by the use of different model client proteins, different assays for both aggregation and sHSP/client interactions, and variable experimental conditions used to mimic cellular stress. To further define sHSP/client interactions and their relevance to sHSP chaperone function, we implemented multiple strategies to characterize sHSP interactions with α-lactalbumin, a model client whose aggregation pathway is well defined. We compared the chaperone activity of human αB-crystallin (HSPB5) with HSPB5 variants that mimic states that arise under conditions of cellular stress or disease. The results show that these closely related sHSPs vary not only in their activity under identical conditions but also in their interactions with clients. Importantly, under nonstress conditions, WT HSPB5 delays client aggregation solely through transient interactions early in the aggregation pathway, whereas HSPB5 mutants that mimic stress-activated conditions can also intervene at later stages of the aggregation pathway to further delay client protein aggregation., (© 2019 Delbecq and Klevit.)

αB-Crystallin (HSPB5) is a small heat-shock protein that is composed of dimers that then assemble into a polydisperse ensemble of oligomers. Oligomerisation is mediated by heterologous interactions between the C-terminal tail of one dimer and the core "α-crystallin" domain of another and stabilised by interactions made by the N-terminal region. Comparatively little is known about the latter contribution, but previous studies have suggested that residues in the region 54-60 form contacts that stabilise the assembly. We have generated mutations in this region (P58A, S59A, S59K, R56S/S59R and an inversion of residues 54-60) to examine their impact on oligomerisation and chaperone activity in vitro. By using native mass spectrometry, we found that all the αB-crystallin mutants were assembly competent, populating similar oligomeric distributions to wild-type, ranging from 16-mers to 30-mers. However, circular dichroism spectroscopy, intrinsic tryptophan and bis-ANS fluorescence studies demonstrated that the secondary structure differs to wild type, the 54-60 inversion mutation having the greatest impact. All the mutants exhibited a dramatic decrease in exposed hydrophobicity. We also found that the mutants in general were equally active as the wild-type protein in inhibiting the amorphous aggregation of insulin and seeded amyloid fibrillation of α-synuclein in vitro, except for the 54-60 inversion mutant, which was significantly less effective at inhibiting insulin aggregation. Our data indicate that alterations in the part of the N-terminal region proximal to the core domain do not drastically affect the oligomerisation of αB-crystallin, reinforcing the robustness of αB-crystallin in functioning as a molecular chaperone.

The glial stress protein alpha B-crystallin (HSPB5) is an endogenous agonist for Toll-like receptor 2 in CD14 + cells. Following systemic administration, HSPB5 acts as a potent inhibitor of neuroinflammation in animal models and reduces lesion development in multiple sclerosis patients. Here, we show that systemically administered HSPB5 rapidly crosses the blood-brain barrier, implicating microglia as additional targets for HSPB5 along with peripheral monocytes and macrophages. To compare key players in the HSPB5-induced protective response of human macrophages and microglia, we applied weighted gene co-expression network analysis on transcript expression data obtained 1 and 4 h after activation. This approach identified networks of genes that are co-expressed in all datasets, thus reducing the complexity of the nonsynchronous waves of transcripts that appear after activation by HSPB5. In both cell types, HSPB5 activates a network of highly connected genes that appear to be functionally equivalent and consistent with the therapeutic effects of HSPB5 in vivo, since both networks include factors that suppress apoptosis, the production of proinflammatory factors, and the development of adaptive immunity. Yet, hub genes at the core of the network in either cell type were strikingly different. They prominently feature the well-known tolerance-promoting programmed-death ligand 1 as a key player in the macrophage response to HSPB5, and the immune-regulatory enzyme cyclooxygenase-2 (COX-2) in that of microglia. This latter finding indicates that despite its reputation as a potential target for nonsteroidal anti-inflammatory drugs, microglial COX-2 plays a central role in the therapeutic effects of HSPB5 during neuroinflammation. GLIA 2017;65:460-473., (© 2017 Wiley Periodicals, Inc.)

αB-crystallin, also called HspB5, is a molecular chaperone able to interact with unfolding proteins. By interacting, it inhibits further unfolding, thereby preventing protein aggregation and allowing ATP-dependent chaperones to refold the proteins. αB-crystallin belongs to the family of small heat-shock proteins (sHsps), which in humans consists of 10 different members. The protein forms large oligomeric complexes, containing up to 40 or more subunits, which in vivo consist of heterooligomeric complexes formed by a mixture of αB-crystallin and other sHsps. αB-crystallin is highly expressed in the lens and to a lesser extent in several other tissues, among which heart, skeletal muscle and brain. αB-crystallin plays a role in several cellular processes, such as signal transduction, protein degradation, stabilization of cytoskeletal structures and apoptosis. Mutations in the αB-crystallin gene can have detrimental effects, leading to pathologies such as cataract and cardiomyopathy. This review describes the biological roles of αB-crystallin, with a special focus on its function in the eye lens, heart muscle and brain. In addition its therapeutic potential is discussed., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

The human small heat-shock protein αB-crystallin is an extremely difficult molecule to study, with its inherent structural dynamics posing unique challenges to all biophysical and structural biology techniques. Here we highlight how the polydispersity and quaternary dynamics of αB-crystallin are intrinsically inter-twined, and how this can impact on measurements of the oligomeric distribution. We show that, in spite of these difficulties, considerable understanding of the varied fluctuations αB-crystallin undergoes at equilibrium has emerged in the last few years. By reporting on data obtained from a variety of biophysical techniques, we demonstrate how the αB-crystallin solution ensemble is governed by molecular motions of varying amplitude and time-scales spanning several orders of magnitude. We describe how these diverse measurements are being used to construct an integrated view of the dynamical structure of αB-crystallin, and highlight areas that require further interrogation. With its study motivating the refinement of experimental techniques, and the development of new approaches to combine the hybrid datasets, we conclude that αB-crystallin continues to represent a paradigm for dynamical biology., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Background: αB-crystallin (HspB5) is a chaperone whose role as a marker of innate immunity activation as well as its therapeutic potential have recently been investigated in several inflammatory diseases: multiple sclerosis, myocardial ischemia, and Guillain-Barré syndrome., Aim: The aim of this study is to determine the role of αB-crystallin in chronic obstructive pulmonary disease (COPD) pathogenesis and inflammation., Materials: Plasma levels of αB-crystallin were studied in 163 patients: 52 healthy non-COPD smokers; 20 COPD smokers in Global Initiative for Chronic Obstructive Lung Disease (GOLD) stages I-II; 43 COPD smokers in GOLD stages III-IV. Forty-eight patients were diagnosed with acute inflammatory respiratory disease. The plasma levels of αB-crystallin antibodies were determined by an enzyme-linked immunosorbent assay (Calbiochem), and were confirmed with Western blotting. Tissue expression of the protein was compared in three different groups of patients: COPD smokers, COPD nonsmokers, and in patients with age-related emphysema., Results: The mean level of anti-αB-crystallin antibodies in non-COPD smokers was 0.291 nm. In COPD smokers it was 0.352 nm and, in patients with inflammatory lung diseases, 0.433 nm. There was a statistically significant difference between COPD smokers and healthy non-COPD smokers (P = 0.010). The same could be observed comparing the group of patients with acute inflammation and non-COPD healthy smokers (P = 0.007). There was no statistically significant difference between patients with mild/moderate inflammation and those with severe COPD. Tissue detection of the protein showed that it was significantly overexpressed in COPD smokers in comparison to COPD nonsmokers and was only slightly expressed in patients with age-related emphysema., Conclusion: αB-crystallin is increased in patients with inflammatory lung diseases. Though unspecific, it could be used in a panel of markers discerning COPD smokers from healthy nonsmokers. As αB-crystallin is a regulator of innate immunity and a therapeutic anti-inflammatory agent, its exact role in COPD pathogenesis and therapy should be explored further.