Chaperone-Like Activity of HSPB5: The Effects of Quaternary Structure Dynamics and Crowding

Polyamines putrescine and spermidine as modulators of protein aggregation rate: The effect on DTT-induced aggregation of α-lactalbumin

Protein aggregation is undesirable for cells due to its possible toxicity, and is also undesirable in biotechnology and pharmaceuticals. Polyamines are known to be capable of both suppressing and stimulating protein aggregation. In the present work polyamines (spermidine, putrescine) have been shown to alter the pathway of α-lactalbumin aggregation induced by dithiothreitol, leading to the formation of larger protein particles during the initial stages of aggregation and promoting the later stage of sticking of aggregates. According to the aggregation kinetics data, polyamines accelerate protein aggregation in a concentration-dependent manner, with a maximum at 50 mM spermidine and 100 mM putrescine. With a further increase in polyamines concentration the effect of aggregation acceleration decreased, thus, the modulation of the aggregation rate by polyamines was shown. A comparison of the aggregation kinetics and hydrodynamic radii growth data registered by dynamic light scattering with the data obtained by asymmetric flow field-flow fractionation and analytical ultracentrifugation allowed us to describe the early stages of aggregation and formation of initial α-lactalbumin clusters. Our results provide a deeper insight into the mechanism of amorphous aggregation of α-lactalbumin and polyamines action on protein aggregation and protein-protein interaction in general.

Linalool acts as a chemical chaperone by inhibiting amyloid-β aggregation

Linalool is a neuroprotective monoterpene found in essential oils from aromatic plants. Linalool's effectiveness in AD animal models has been established previously, but its mechanisms of action remain unclear. Therefore, this study aims to investigate whether linalool binds directly to the amyloid beta (Aβ) fibrils to understand it's role in preventing neurodegeneration. The anti-aggregation ability of Linalool was determined using Dithiothreitol (DTT), and thermal aggregation assays followed by Thioflavin T (ThT) binding assay. AD animals were treated with Linalool, and Thioflavin T staining was used to check the binding of linalool to Aβ fibrils in rat brain tissue sections. Preliminary studies revealed the anti-aggregation potential of linalool under the thermal and chemical stimulus. Further, in ThT binding assay Linalool inhibited Aβ aggregation, binding directly to Aβ fibrils. The reduced fluorescence intensity of ThT in AD brain tissues following linalool administration, highlights its neuroprotective potential as a therapeutic agent for AD.

Biological effects and mechanism of β-amyloid aggregation inhibition by penetrable recombinant human HspB5-ACD structural domain protein

Alzheimer's disease (AD) is a global medical challenge. Studies have shown that neurotoxicity caused by pathological aggregation of β-amyloid (Aβ) is an important factor leading to AD. Therefore, inhibiting the pathological aggregation of Aβ is the key to treating AD. The recombinant human HspB5-ACD structural domain protein (AHspB5) prepared by our group in the previous period has been shown to have anti-amyloid aggregation effects, but its inability to penetrate biological membranes has limited its development. In this study, we prepared a recombinant fusion protein (T-AHspB5) of TAT and AHspB5. In vitro experiments showed that T-AHspB5 inhibited the formation of Aβ1-42 protofibrils and had the ability to penetrate the blood-brain barrier; in cellular experiments, T-AHspB5 prevented Aβ1-42-induced oxidative stress damage, apoptosis, and inflammatory responses in neuronal cells, and its mechanism of action was related to microglia activation and mitochondria-dependent apoptotic pathway. In animal experiments, T-AHspB5 improved memory and cognitive dysfunction and inhibited pathological changes of AD in APP/PS1 mice. In conclusion, this paper is expected to reveal the intervention mechanism and biological effect of T-AHspB5 on pathological aggregation of Aβ1-42, provide a new pathway for the treatment of AD, and lay the foundation for the future development and application of T-AHspB5.

Change in the Kinetic Regime of Aggregation of Yeast Alcohol Dehydrogenase in the Presence of 2-Hydroxypropyl-β-cyclodextrin

Chemical chaperones are low-molecular-weight compounds that suppress protein aggregation. They can influence different stages of the aggregation process-the stage of protein denaturation, the nucleation stage and the stage of aggregate growth-and this may lead to a change in the aggregation kinetic regime. Here, the possibility of changing the kinetic regime in the presence of a chemical chaperone 2-hydroxypropyl-β-cyclodextrin (2-HP-β-CD) was investigated for a test system based on the thermally induced aggregation of yeast alcohol dehydrogenase (yADH) at 56 °C. According to differential scanning calorimetry data, 2-HP-β-CD did not affect the stage of the protein molecule unfolding. Dynamic light scattering data indicated changes in the aggregation kinetics of yADH during the nucleation and aggregate growth stages in the presence of the chaperone. The analysis of kinetic curves showed that the order of aggregation with respect to protein (nc), calculated for the stage of aggregate growth, changed from nc = 1 to nc = 2 with the addition of 100 mM 2-HP-β-CD. The mechanism of 2-HP-β-CD action on the yADH thermal aggregation leading to a change in its kinetic regime of aggregation is discussed.

αB-Crystallin Peptide Fused with Elastin-like Polypeptide: Intracellular Activity in Retinal Pigment Epithelial Cells Challenged with Oxidative Stress

BACKGROUND

Oxidative stress-induced retinal degeneration is among the main contributing factors of serious ocular pathologies that can lead to irreversible blindness. αB-crystallin (cry) is an abundant component of the visual pathway in the vitreous humor, which modulates protein and cellular homeostasis. Within this protein exists a 20 amino acid fragment (mini-cry) with both chaperone and antiapoptotic activity. This study fuses this mini-cry peptide to two temperature-sensitive elastin-like polypeptides (ELP) with the goal of prolonging its activity in the retina.

METHODS

The biophysical properties and chaperone activity of cry-ELPs were confirmed by mass spectrometry, cloud-point determination, and dynamic light scattering 'DLS'. For the first time, this work compares a simpler ELP architecture, cry-V96, with a previously reported ELP diblock copolymer, cry-SI. Their relative mechanisms of cellular uptake and antiapoptotic potential were tested using retinal pigment epithelial cells (ARPE-19). Oxidative stress was induced with H2O2 and comparative internalization of both cry-ELPs was made using 2D and 3D culture models. We also explored the role of lysosomal membrane permeabilization by confocal microscopy.

RESULTS

The results indicated successful ELP fusion, cellular association with both 2D and 3D cultures, which were enhanced by oxidative stress. Both constructs suppressed apoptotic signaling (cleaved caspase-3); however, cry-V96 exhibited greater lysosomal escape.

CONCLUSIONS

ELP architecture is a critical factor to optimize delivery of therapeutic peptides, such as the anti-apoptotic mini-cry peptide; furthermore, the protection of mini-cry via ELPs is enhanced by lysosomal membrane permeabilization.

Effects of Molecular Crowding and Betaine on HSPB5 Interactions, with Target Proteins Differing in the Quaternary Structure and Aggregation Mechanism

The aggregation of intracellular proteins may be enhanced under stress. The expression of heat-shock proteins (HSPs) and the accumulation of osmolytes are among the cellular protective mechanisms in these conditions. In addition, one should remember that the cell environment is highly crowded. The antiaggregation activity of HSPB5 and the effect on it of either a crowding agent (polyethylene glycol (PEG)) or an osmolyte (betaine), or their mixture, were tested on the aggregation of two target proteins that differ in the order of aggregation with respect to the protein: thermal aggregation of glutamate dehydrogenase and DTT-induced aggregation of lysozyme. The kinetic analysis of the dynamic light-scattering data indicates that crowding can decrease the chaperone-like activity of HSPB5. Nonetheless, the analytical ultracentrifugation shows the protective effect of HSPB5, which retains protein aggregates in a soluble state. Overall, various additives may either improve or impair the antiaggregation activity of HSPB5 against different protein targets. The mixed crowding arising from the presence of PEG and 1 M betaine demonstrates an extraordinary effect on the oligomeric state of protein aggregates. The shift in the equilibrium of HSPB5 dynamic ensembles allows for the regulation of its antiaggregation activity. Crowding can modulate HSPB5 activity by affecting protein-protein interactions.

Effect of Betaine and Arginine on Interaction of αB-Crystallin with Glycogen Phosphorylase b

Protein-protein interactions (PPIs) play an important role in many biological processes in a living cell. Among them chaperone-client interactions are the most important. In this work PPIs of αB-crystallin and glycogen phosphorylase b (Phb) in the presence of betaine (Bet) and arginine (Arg) at 48 °C and ionic strength of 0.15 M were studied using methods of dynamic light scattering, differential scanning calorimetry, and analytical ultracentrifugation. It was shown that Bet enhanced, while Arg reduced both the stability of αB-crystallin and its adsorption capacity (AC₀) to the target protein at the stage of aggregate growth. Thus, the anti-aggregation activity of αB-crystallin increased in the presence of Bet and decreased under the influence of Arg, which resulted in inhibition or acceleration of Phb aggregation, respectively. Our data show that chemical chaperones can influence the tertiary and quaternary structure of both the target protein and the protein chaperone. The presence of the substrate protein also affects the quaternary structure of αB-crystallin, causing its disassembly. This is inextricably linked to the anti-aggregation activity of αB-crystallin, which in turn affects its PPI with the target protein. Thus, our studies contribute to understanding the mechanism of interaction between chaperones and proteins.

The crystallin alpha B (HSPB5)-tripartite motif containing 33 (TRIM33) axis mediates myocardial fibrosis induced by angiotensinogen II through transforming growth factor-β (TGF-β1)-Smad3/4 signaling

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.

Regulation by Different Types of Chaperones of Amyloid Transformation of Proteins Involved in the Development of Neurodegenerative Diseases

The review highlights various aspects of the influence of chaperones on amyloid proteins associated with the development of neurodegenerative diseases and includes studies conducted in our laboratory. Different sections of the article are devoted to the role of chaperones in the pathological transformation of alpha-synuclein and the prion protein. Information about the interaction of the chaperonins GroE and TRiC as well as polymer-based artificial chaperones with amyloidogenic proteins is summarized. Particular attention is paid to the effect of blocking chaperones by misfolded and amyloidogenic proteins. It was noted that the accumulation of functionally inactive chaperones blocked by misfolded proteins might cause the formation of amyloid aggregates and prevent the disassembly of fibrillar structures. Moreover, the blocking of chaperones by various forms of amyloid proteins might lead to pathological changes in the vital activity of cells due to the impaired folding of newly synthesized proteins and their subsequent processing. The final section of the article discusses both the little data on the role of gut microbiota in the propagation of synucleinopathies and prion diseases and the possible involvement of the bacterial chaperone GroE in these processes.

Effect of Trehalose on Oligomeric State and Anti-Aggregation Activity of αB-Crystallin

αB-Crystallin (αB-Cr), one of the main crystalline lens proteins, along with other crystallins maintains lens transparency suppressing protein aggregation and thus preventing cataractogenesis. αB-Cr belongs to the class of molecular chaperones; being expressed in many tissues it has a dynamic quaternary structure, which is essential for its chaperone-like activity. Shift in the equilibrium between ensembles of oligomers of different size allows regulating the chaperone activity. Trehalose is known to inhibit protein aggregation in vivo and in vitro, and it is widely used in biotechnology. The results of studying the effect of trehalose on the chaperone-like activity of crystallins can serve as a basis for the design of drugs delaying cataractogenesis. We have studied the trehalose effect on the quaternary structure and anti-aggregation activity of αB-Cr using muscle glycogen phosphorylase b (Phb) as a target protein. According to the dynamic light scattering data, trehalose affects the nucleation stage of Phb thermal aggregation at 48°C, and an increase in the αB-Cr adsorption capacity (AC₀) is the main effect of trehalose on the aggregation process in the presence of the protein chaperone (AC₀ increases 1.5-fold in the presence of 66 mM trehalose). According to the sedimentation analysis data, trehalose stabilizes the dimeric form of Phb at the stages of denaturation and dissociation and enhances the interaction of αB-Cr with the target protein. Moreover, trehalose shifts the equilibrium between the αB-Cr oligomers towards the smaller forms. Thus, trehalose affects the quaternary structure of αB-Cr and increases its anti-aggregation activity at the nucleation stage.

Case report: Fatal infantile hypertonic myofibrillar myopathy with compound heterozygous mutations in the CRYAB gene

BACKGROUND

Fatal infantile hypertonic myofibrillar myopathy (FIHMM) is an autosomal recessive hereditary disease characterized by amyotrophy, progressive flexion contracture and ankylosis of the trunk and limb muscles, apnea and respiratory failure, and increased creatine phosphate levels. It is caused by mutations in the CRYAB gene, and only around 18 cases including genetic mutations have been reported worldwide. All patients with FIHMM develop respiratory distress, progressive stiffness of the limbs, and have a poor prognosis. However, no effective treatment for CRYAB-associated respiratory failure has been reported. Here, we report a case of FIHMM with a novel heterozygous missense mutation.

CASE PRESENTATION

A 2-year-old female developed scoliosis of the lumbar spine and restrictive ventilatory dysfunction in infancy. She was admitted to the hospital with labored breathing on the third day after the second injection of inactivated poliomyelitis vaccine. Acute respiratory failure, pneumothorax, and cardiac arrest arose in the patient during hospitalization, and progressive stiffness of the trunk and limb muscles appeared, accompanied by obvious abdominal distension and an increase in phosphocreatine kinase levels. Screenings for genetic metabolic diseases in the blood and urine were normal. Electromyography revealed mild myogenic damage. A muscle biopsy indicated the accumulation of desmin, α-crystallin, and myotilin in the musculus biceps brachii, and dense granules were observed in muscle fibers using electron microscopy. Mutation analysis of CRYAB revealed a novel heterozygous missense mutation in the proband, c.302A > C (p.His101Pro) and c.3G > A (p.Met1Ile), which inherited from her asymptomatic, heterozygous carrier parents, respectively. The proband was finally diagnosed as FIHMM. One month after the FIHMM diagnosis, the child died of respiratory failure.

CONCLUSION

We report a case of FIHMM with a novel heterozygous missense mutation of CRYAB. This finding might improve our understanding of FIHMM and highlight a novel mutation in the Chinese population.

Structural and functional studies of D109A human αB-crystallin contributing to the development of cataract and cardiomyopathy diseases

αB-crystallin (heat shock protein β5/HSPB5) is a member of the family of small heat shock proteins that is expressed in various organs of the human body including eye lenses and muscles. Therefore, mutations in the gene of this protein (CRYAB) might have many pathological consequences. A new mutation has recently been discovered in the α-crystallin domain of this chaperone protein which replaces aspartate 109 with alanine (D109A). This mutation can cause myofibrillar myopathy (MFM), cataracts, and cardiomyopathy. In the current study, several spectroscopic and microscopic analyses, as well as gel electrophoresis assessment were applied to elucidate the pathogenic contribution of human αB-crystallin bearing D109A mutation in development of eye lens cataract and myopathies. The protein oligomerization, chaperone-like activity and chemical/thermal stabilities of the mutant and wild-type protein were also investigated in the comparative assessments. Our results suggested that the D109A mutation has a significant impact on the important features of human αB-crystallin, including its structure, size of the protein oligomers, tendency to form amyloid fibrils, stability, and chaperone-like activity. Given the importance of aspartate 109 in maintaining the proper structure of the α-crystallin domain, its role in the dimerization and chaperone-like activity, as well as preserving protein stability through the formation of salt bridges; mutation at this important site might have critical consequences and can explain the genesis of myopathy and cataract disorders. Also, the formation of large light-scattering aggregates and disruption of the chaperone-like activity by D109A mutation might be considered as important contributing factors in development of the eye lens opacity.