Human lysozyme gene mutations cause hereditary systemic amyloidosis

Sound-mediated nucleation and growth of amyloid fibrils

Mechanical energy, specifically in the form of ultrasound, can induce pressure variations and temperature fluctuations when applied to an aqueous media. These conditions can both positively and negatively affect protein complexes, consequently altering their stability, folding patterns, and self-assembling behavior. Despite much scientific progress, our current understanding of the effects of ultrasound on the self-assembly of amyloidogenic proteins remains limited. In the present study, we demonstrate that when the amplitude of the delivered ultrasonic energy is sufficiently low, it can induce refolding of specific motifs in protein monomers, which is sufficient for primary nucleation; this has been revealed by MD. These ultrasound-induced structural changes are initiated by pressure perturbations and are accelerated by a temperature factor. Furthermore, the prolonged action of low-amplitude ultrasound enables the elongation of amyloid protein nanofibrils directly from natively folded monomeric lysozyme protein, in a controlled manner, until it reaches a critical length. Using solution X-ray scattering, we determined that nanofibrillar assemblies, formed either under the action of sound or from natively fibrillated lysozyme, share identical structural characteristics. Thus, these results provide insights into the effects of ultrasound on fibrillar protein self-assembly and lay the foundation for the potential use of sound energy in protein chemistry.

Significance Statement

Understanding how and why proteins form amyloid fibrils is crucial for research into various diseases, including neurodegeneration. Ultrasound is routinely used in research settings as a tool for generating amyloid seeds (nucleation sites) from mature fibrils, which accelerate the rate of fibril growth. However, ultrasound can have various effects on aqueous media including temperature, extreme shear, and free radicals. Here we show that when the ultrasound parameters are precisely adjusted, they can be utilized as a tool for amyloid growth directly from the natively folded monomers. Thus, it is possible to induce minor changes in the folding of proteins, which trigger nucleation and accelerate amyloid growth. This knowledge lays the foundation for the potential use of sound in protein chemistry.

The inhibition of fibril formation of lysozyme by sucrose and trehalose

The two disaccharides, trehalose and sucrose, have been compared in many studies due to their structural similarity. Both possess the ability to stabilise and reduce aggregation of proteins. Trehalose has also been shown to inhibit the formation of highly structured protein aggregates called amyloid fibrils. This study aims to compare how the thermal stability of the protein lysozyme at low pH (2.0 and 3.5) is affected by the presence of the two disaccharides. We also address the anti-aggregating properties of the disaccharides and their inhibitory effects on fibril formation. Differential scanning calorimetry confirms that the thermal stability of lysozyme is increased by the presence of trehalose or sucrose. The effect is slightly larger for sucrose. The inhibiting effects on protein aggregation are investigated using small-angle X-ray scattering which shows that the two-component system consisting of lysozyme and water (Lys/H2O) at pH 2.0 contains larger aggregates than the corresponding system at pH 3.5 as well as the sugar containing systems. In addition, the results show that the particle-to-particle distance in the sugar containing systems (Lys/Tre/H2O and Lys/Suc/H2O) at pH 2.0 is longer than at pH 3.5, suggesting larger protein aggregates in the former. Finally, the characteristic distance separating β-strands in amyloid fibrils is observed for the Lys/H2O system at pH 2.0, using wide-angle X-ray scattering, while it is not clearly observed for the sugar containing systems. This study further shows that the two disaccharides stabilise the native fold of lysozyme by increasing the denaturation temperature. However, other factors, such as a weakening of hydrophobic interactions and hydrogen bonding between proteins, might also play a role in their inhibitory effect on amyloid fibril formation.

Protein Nanotubes as Advanced Material Platforms and Delivery Systems

Protein nanotubes (PNTs) as state-of-the-art nanocarriers are promising for various potential applications both in the food and pharmaceutical industries. Derived from edible starting sources like α-lactalbumin, lysozyme, and ovalbumin, PNTs bear properties of biocompatibility and biodegradability. Their large specific surface area and hydrophobic core facilitate chemical modification and loading of bioactive substances, respectively. Moreover, their enhanced permeability and penetration ability across biological barriers such as intestinal mucus, extracellular matrix, and thrombus clot, make it promising platforms for health-related applications. Most importantly, their simple preparation processes enable large-scale production, supporting applications in the biomedical and nanotechnological fields. Understanding the self-assembly principles is crucial for controlling their morphology, size, and shape, and thus provides the ground to a multitude of applications. Here, the current state-of-the-art of PNTs including their building materials, physicochemical properties, and self-assembly mechanisms are comprehensively reviewed. The advantages and limitations, as well as challenges and prospects for their successful applications in biomaterial and pharmaceutical sectors are then discussed and highlighted. Potential cytotoxicity of PNTs and the need of regulations as critical factors for enabling in vivo applications are also highlighted. In the end, a brief summary and future prospects for PNTs as advanced platforms and delivery systems are included.

"Nature or nurture" - How environmental factors influence the conformational memory of amyloid fibrils

Amyloid fibrils are complex protein structures with multilayered chiral architecture, that are known to self-propagate. The replication of the mother seed structure by daughter fibrils is known as conformational or templated memory. Using vibrational circular dichroism (VCD), electronic circular dichroism (ECD), transmission electron microscopy (TEM), and cryo-electron microscopy (cryo-EM) we have shown that environmental factors (here agitation) can be a competing force against the templated growth of human lysozyme fibrils. In the cross-seeding experiment non-agitated daughters preserved the structure of agitated mothers, whereas agitated daughters did not always exhibit the same characteristics as their non-agitated mothers. This pattern was reflected on various levels of fibril architecture (secondary structure, protofilament handedness, morphology), demonstrating that the structural indeterminism originates from deeper levels of the fibril structure. This observation may contribute to a better understanding of the processes behind fibril formation.

Fibril structures of TFG protein mutants validate the identification of TFG as a disease-related amyloid protein by the IMPAcT method

We previously presented a bioinformatic method for identifying diseases that arise from a mutation in a protein's low-complexity domain that drives the protein into pathogenic amyloid fibrils. One protein so identified was the tropomyosin-receptor kinase-fused gene protein (TRK-fused gene protein or TFG). Mutations in TFG are associated with degenerative neurological conditions. Here, we present experimental evidence that confirms our prediction that these conditions are amyloid-related. We find that the low-complexity domain of TFG containing the disease-related mutations G269V or P285L forms amyloid fibrils, and we determine their structures using cryo-electron microscopy (cryo-EM). These structures are unmistakably amyloid in nature and confirm the propensity of the mutant TFG low-complexity domain to form amyloid fibrils. Also, despite resulting from a pathogenic mutation, the fibril structures bear some similarities to other amyloid structures that are thought to be nonpathogenic and even functional, but there are other factors that support these structures' relevance to disease, including an increased propensity to form amyloid compared with the wild-type sequence, structure-stabilizing influence from the mutant residues themselves, and double-protofilament amyloid cores. Our findings elucidate two potentially disease-relevant structures of a previously unknown amyloid and also show how the structural features of pathogenic amyloid fibrils may not conform to the features commonly associated with pathogenicity.

Human lysozyme inhibits the fibrillation of serum amyloid a protein from systemic AA amyloidosis

BACKGROUND

Systemic AA amyloidosis is a world-wide occurring protein misfolding disease in humans and animals that arises from the formation of amyloid fibrils from serum amyloid A (SAA) protein and their deposition in multiple organs.

OBJECTIVE

To identify new agents that prevent fibril formation from SAA protein and to determine their mode of action.

MATERIALS AND METHODS

We used a cell model for the formation of amyloid deposits from SAA protein to screen a library of peptides and small proteins, which were purified from human hemofiltrate. To clarify the inhibitory mechanism the obtained inhibitors were characterised in cell-free fibril formation assays and other biochemical methods.

RESULTS

We identified lysozyme as an inhibitor of SAA fibril formation. Lysozyme antagonised fibril formation both in the cell model as well as in cell-free fibril formation assays. The protein binds SAA with a dissociation constant of 16.5 ± 0.6 µM, while the binding site on SAA is formed by segments of positively charged amino acids.

CONCLUSION

Our data imply that lysozyme acts in a chaperone-like fashion and prevents the aggregation of SAA protein through direct, physical interactions.

Amphiphilic (di-)gradient copoly(2-oxazoline)s are potent amyloid fibril formation inhibitors

MOTIVATION

Amyloidoses are diseases caused by the accumulation of normally soluble proteins in the form of insoluble amyloids, leading to the gradual dysfunction and failure of various organs and tissues. Inhibiting amyloid formation is therefore an important therapeutic target.

HYPOTHESIS

We hypothesized that mono- and di-gradient amphiphilic copolymers of hydrophilic 2-(m)ethyl-2-oxazoline and hydrophobic 2-aryl-2-oxazolines may inhibit amyloid fibril formation.

EXPERIMENTS

In the model system with hen egg white lysozyme (HEWL) as amyloidogenic protein we determined the effect of these polymers on the amyloid formation by making use of the thioflavin T fluorescence, transmission electron microscopy, isothermal titration calorimetry, and dynamic light scattering.

FINDINGS

We found that some gradient copolymers possess very potent concentration-dependent inhibitory effects on HEWL amyloid formation. Structure-activity relationship revealed that copolymers with higher ratios of aromatic monomeric units had stronger amyloid suppression effects, most plausibly due to the combination of hydrophobic and π-π interactions. The measurements also revealed that the polymers that inhibit amyloid formation most plausibly do so in the form of micelles that interact with the growing amyloid fibril ends, not with isolated HEWL molecules in solution. These findings suggest the potential use of these gradient copolymers as therapeutic agents for amyloidoses.

First Report of Lysozyme Amyloidosis with p.F21L/T88N Amino Acid Substitutions in a Russian Family

Lysozyme amyloidosis is caused by an amino acid substitution in the sequence of this protein. In our study, we described a clinical case of lysozyme amyloidosis in a Russian family. In our work, we described in detail the histological changes in tissues that appeared as a result of massive deposition of amyloid aggregates that affected almost all organ systems, with the exception of the central nervous system. We determined the type of amyloidosis and mutations using mass spectrometry. Using mass spectrometry, the protein composition of tissue samples of patient 1 (autopsy material) and patient 2 (biopsy material) with histologically confirmed amyloid deposits were analyzed. Amino acid substitutions p.F21L/T88N in the lysozyme sequence were identified in both sets of samples and confirmed by sequencing of the lysozyme gene of members of this family. We have shown the inheritance of these mutations in the lysozyme gene in members of the described family. For the first time, we discovered a mutation in the first exon p.F21L of the lysozyme gene, which, together with p.T88N amino acid substitution, led to amyloidosis in members of the studied family.

Suppression of human lysozyme aggregation by a novel copper-based complex of 3,4-dimethoxycinnamic acid

In this work, a new Cu(II)-based complex as a chemotherapeutic drug agent, formulated as[Cu(DCA)4(H2O)2]⋅4H2O⋅4MeOH, (DCA = 3,4-dimethoxycinnamic acid), namely 1 was successfully synthesized utilizing DCA as a ligand to arrest fibrillation in Human lysozyme. The 1 was thoroughly characterized by single crystal X-ray diffraction (SC-XRD), spectroscopic (UV-Vis and FTIR) techniques, PXRD, and TGA analysis. Its crystal structure reveals a paddle wheel network around central copper metal ions. The Cu(II) metal ions exhibit a distorted square pyramidal configuration. The fluorescence titration studies showed moderate binding interaction of 1 with HuL with Ka of 6.3x105 M-1 at pH-2, 25 °C due to its interaction withAsp53, Tyr63, Val110, and Ala111 as shown by docking and simulation studies. 1suppresses the HuL fibrillation in a concentration-dependent manner, as demonstrated by ThT assay. At 200 µM concentration, it leads to the formation of smaller species of the protein in comparison to the control sample, as suggested by Light Scattering studies. The species formed are less hydrophobic and retain their native α-helix structure compared to the control samples, which are hydrophobic and form β-sheet rich amyloids as shown by ANS hydrophobicity assay and CD spectroscopy, respectively. Furthermore, morphological analysis of the species by AFM has demonstrated that, unlike mature amyloid fibrils in the control sample, HuL forms small-size aggregates in the presence of 1 under similar fibrillation conditions. It can be concluded that 1 effectively suppresses HuL fibrillation due to moderate binding to the protein.Communicated by Ramaswamy H. Sarma.

Langmuir monolayer of lysozyme at variable subphase pH conditions: a comprehensive study on structure, morphology and hysteresis behaviour

Formation of a pure Langmuir monolayer of lysozyme at the air-water interface and its investigation by means of a surface pressure (π)-mean molecular area (A) isotherm has been accomplished under different subphase pH conditions. A normalized area-time curve confirms the stable nature of the lysozyme monolayer whose compressibility variation with an increased surface pressure at specific subphase pH has also been studied from π-A isotherms. The monolayers exhibit irreversible hysteresis behaviour irrespective of subphase pH conditions, as evidenced from successive compression-expansion π-A isotherm cycles. Comparison of surface thermodynamics under hysteresis with subphase pH variation confirms that the monolayer at subphase pH ≈ 4.0 involves a greater amount of energy to attain and retain the ordered and compact monolayer than the other two pH conditions (pH ≈ 7.0 and 9.5). In situ visualization of lysozyme monolayers by Brewster angle microscopy suggests the homogeneous and stripe-like pattern formation at lower and higher surface pressure respectively. Further investigations of lysozyme films at solid surfaces have been carried out with atomic force microscopy and X-ray reflectivity (XRR) analysis. Structural reversibility of lysozyme molecules under compression-expansion-compression of the monolayer is revealed from the comparison of height profiles of AFM images and electron density profiles as extracted from XRR analysis of the films deposited during both first and second compressions of the monolayer. The mechanism of the structural rearrangement of lysozyme molecules with surface pressure variation at different subphase pH is explored, correlating macroscopic and microscopic information.

The impact of modified polystyrene on lysozyme fibrillation studied by surface-enhanced Raman spectroscopy (SERS)

Nanoplastics could modulate the fibrillation of amyloid proteins. However, many chemical functional groups are adsorbed to change the interfacial chemistry of nanoplastics in the real world. Herein, this study aimed to investigate the effects of polystyrene (PS), carboxyl modified PS (PS-COOH), and amino modified PS (PS-NH₂) on the fibrillation of hen egg-white lysozyme (HEWL). Due to the differences in the interfacial chemistry, concentration was considered an essential factor. PS-NH₂ (10 μg/mL) could promote the fibrillation of HEWL similar to PS (50 μg/mL) and PS-COOH (50 μg/mL). Moreover, promoting the primary nucleation step of amyloid fibril formation was the primary reason. The differences in spatial conformation of HEWL were characterized by Fourier transform-infrared spectroscopy and surface enhanced Raman spectroscopy (SERS). Strikingly, a particular signal of SERS of HEWL incubated with PS-NH₂ at 1610 cm^-1 was found due to the interaction between amino group of PS-NH₂ and tryptophan (or tyrosine) of HEWL. Therefore, a new perspective was provided to understand the regulation of interfacial chemistry of nanoplastics on the fibrillation of amyloid proteins. Additionally, this study suggested that SERS could be a powerful method to investigate the interactions between proteins and nanoparticles.

Green tea leaf constituents inhibit the formation of lysozyme amyloid aggregates: An effect of mutual interactions

Amyloidoses represent a group of pathological conditions characterized by amyloid fibrils accumulating in the form of deposits in intra- or extracellular space, leading to tissue damage. The lysozyme from hen egg-white (HEWL) is often used as a universal model protein to study the anti-amyloid effects of small molecules. The in vitro anti-amyloid activity and mutual interactions of green tea leaf constituents: (-)-epigallocatechin gallate (EGCG), (-)-epicatechin (EC), gallic acid (GA), caffeine (CF) and their equimolar mixtures were studied. The inhibition of HEWL amyloid aggregation was monitored by a Thioflavin T fluorescence assay and atomic force microscopy (AFM). The interactions of the analyzed molecules with HEWL were interpreted by ATR-FTIR and protein-small ligand docking studies. EGCG was the only substance efficiently inhibiting amyloid formation (IC₅₀ ~ 193 μM), slowing the aggregation process, reducing the number of fibrils and partially stabilizing the secondary structure of HEWL. Compared to EGCG alone, EGCG-containing mixtures displayed lower overall anti-amyloid efficacy. The decrease in efficiency results from (a) the spatial interference of GA, CF and EC with EGCG while binding to HEWL, (b) the propensity of CF to form a less active adduct with EGCG, which participates in interactions with HEWL in parallel with pure EGCG. This study confirms the importance of interaction studies, revealing the possible antagonistic behavior of molecules when combined.

Effects of the aspect ratio of plasmonic gold nanorods on the inhibition of lysozyme amyloid formation

Amyloid formation due to altered protein folding and aggregation has gained significant attention due to its association with neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease, Huntington's disease, and systemic lysozyme amyloidosis. Amyloids are characterized by parallel and anti-parallel cross-β-strands arranged to form stacks of sheets that provide stability and rigidity to the amyloid core. The prototypic protein Hen Egg White Lysozyme (HEWL) has been extensively used to understand protein hydrolysis, fragmentation, folding, misfolding, and amyloid formation. In the present study, we have examined the efficacy of plasmonic gold nanorods (GNRs) as an anti-amyloid agent against HEWL amyloids. Our results reveal that (i) the amyloid inhibition by plasmonic GNRs is dependent on their aspect ratio, (ii) the large aspect ratio GNRs ameliorate amyloid assembly completely, and (iii) GNRs interfere at several stages along the lysozyme fibril-formation pathway and block the conversion of monomeric and oligomeric intermediates into mature fibrils. Using a multi-parametric approach, we demonstrate that GNRs drive HEWL into off-pathway and amyloid-incompetent forms. To establish GNRs as generic amyloid inhibitors, we extended our studies to another archetypal protein, Bovine Serum Albumin (BSA), and observed similar results of GNRs inhibiting BSA aggregation. We believe that our results will pave the way for the potential use of GNRs with current therapeutics to reduce the burden of amyloid-related diseases.

Mechanistic and biophysical insight into the inhibitory and disaggregase role of antibiotic moxifloxacin on human lysozyme amyloid formation

Lysozyme amyloidosis is a systemic non-neuropathic disease caused by the accumulation of amyloids of mutant lysozyme. Presently, therapeutic interventions targeting lysozyme amyloidosis, remain elusive with only therapy available for lysozyme amyloidosis being supportive management. In this work, we examined the effects of moxifloxacin, a synthetic fluoroquinolone antibiotic on the amyloid formation of human lysozyme. The ability of moxifloxacin to interfere with lysozyme amyloid aggregation was examined using various biophysical methods like Rayleigh light scattering, Thioflavin T fluorescence assay, transmission electron microscopy and docking method. The reduction in scattering and ThT fluorescence along with extended lag phase in presence of moxifloxacin, suggest that the antibiotic inhibits and impedes the lysozyme fibrillation in concentration dependent manner. From ANS experiment, we deduce that moxifloxacin is able to decrease the hydrophobicity of the protein molecule thereby preventing aggregation. Our CD and DLS results show that moxifloxacin stabilizes the protein in its native monomeric structure, thus also showing retention of lytic activity upto 69% and inhibition of cytotoxicity at highest concentration of moxifloxacin. The molecular docking showed that moxifloxacin forms a stable complex of -7.6 kcal/mol binding energy and binds to the aggregation prone region of lysozyme thereby stabilising it and preventing aggregation. Moxifloxacin also showed disaggregase potential by disrupting fibrils and decreasing the β-sheet content of the fibrils. Our current study, thus highlight the anti-amyloid and disaggregase property of an antibiotic moxifloxacin and hence sheds light on the future of antibiotics against protein aggregation, a hallmark event in many neurodegenerative diseases.

Elucidating the inhibitory effects of rationally designed novel hexapeptide against hen egg white lysozyme fibrillation at acidic and physiological pH

Inhibition of highly ordered cross-β-sheet-rich aggregates of misfolded amyloid proteins using rationally designed sequence-based short peptides is a promising therapeutic strategy for the treatment of neurodegenerative diseases. Here, we have explored the anti-amyloidogenic potency of a rationally designed hexapeptide (Tyr-Pro-Gln-Ile-Pro-Asn) on in vitro hen egg white lysozyme (HEWL) amyloid fibril formation at acidic pH and physiological pH using computational docking as well as various biophysical techniques such as fluorescence spectroscopy, UV-vis spectroscopy, FTIR spectroscopy, confocal microscopy and TEM. The peptide was designed based on the aggregation-prone region (APR) of HEWL and thus referred to as SqP1 (Sequence-based Peptide 1). SqP1 showed over 70% inhibition of HEWL amyloid formation at pH 2.2 and approximately 50% inhibition at pH 7.5. We propose that SqP1 binds to the APR of HEWL and interacts strongly with the Trp62/Trp63, ultimately stabilizing monomeric HEWL at both the pH conditions and preventing conformation changes in the structure of HEWL, leading to the formation of amyloidogenic fibrillar structures. A sequence-based peptide inhibitor of HEWL amyloid formation was not reported previously, making this a critical study that will further emphasize the importance of short synthetic peptides as amyloid inhibitors.

Evaluating the inhibitory potential of natural compound luteolin on human lysozyme fibrillation

Numerous pathophysiological conditions known as amyloidosis, have been connected to protein misfolding leading to aggregation of proteins. Inhibition of cytotoxic aggregates or disaggregation of the preformed fibrils is thus one of the important strategies in the prevention of such diseases. Growing interest and exploration of identification of small molecules mainly natural compounds can prevent or delay amyloid fibril formation. We examined the mechanism of interaction and inhibition of human lysozyme (HL) aggregates with luteolin (LT). Biophysical and computational approaches have been employed to study the effect of LT on HL amyloid aggregation. Transmission Electronic Microscopy, Thioflavin T fluorescence, UV-vis spectroscopy, and RLS demonstrates that LT inhibit HL fibril formation. ANS fluorescence and hemolytic assay was also employed to examine the effect of the LT on toxicity of HL aggregation. Docking and molecular dynamics results showed that LT interacted with HL via hydrophobic and hydrogen interactions, thus reducing fibrillation levels. These findings highlight the benefit of polyphenols as safe therapy for preventing amyloid related diseases.

Metal-Organic Frameworks as Sensors for Human Amyloid Diseases

Metal-organic frameworks (MOFs) are versatile compounds with emergent applications in the fabrication of biosensors for amyloid diseases. They hold great potential in biospecimen protection and unprecedented probing capabilities for optical and redox receptors. In this Review, we summarize the main methodologies employed in the fabrication of MOF-based sensors for amyloid diseases and collect all available data in the literature related to their performance (detection range, limit of detection, recovery, time of analysis, among other parameters). Nowadays, MOF sensors have evolved to a point where they can, in some cases, outperform technologies employed in the detection of several amyloid biomarkers (amyloid β peptide, α-synuclein, insulin, procalcitonin, and prolactin) present in biological fluids, such as cerebrospinal fluid and blood. A special emphasis has been given by researchers on Alzheimer's disease monitoring to the detriment of other amyloidosis that are underexploited despite their societal relevance (e.g., Parkinson's disease). There are still important obstacles to overcome in order to selectively detect the various peptide isoforms and soluble amyloid species associated with Alzheimer's disease. Furthermore, MOF contrast agents for imaging peptide soluble oligomers in living humans are also scarce (if not nonexistent), and action in this direction is unquestionably required to clarify the contentious link between the amyloidogenic species and the disease, guiding research toward the most promising therapeutic strategies.

Differential effects of DTT on HEWL amyloid fibrillation and fibril morphology at different pH

Proteins can transform from their native state to a state having fibrillar aggregates characterized by cross β sheet structure. The fibrillar aggregates are known as amyloid and have been linked to several disorders. Disulfide bonds in proteins are one of the important factors that determine the propensity of aggregation. Hen Egg White Lysozyme (HEWL) was used by us as a model protein to decipher the role disulfide bonds play in the amyloid fibril formation and fibril morphology by using Dithiothreitol (DTT) as reducing agent at pH 2.7 and pH 7.4. We found that DTT can have different effects on HEWL amyloid depending on pH and the buffer used for preparing the amyloid fibrils. Our studies highlight the critical role of non-native disulfide bonds in amyloidogenesis and how disruption of these bonds can greatly affect the fibrillation process. Overall, these studies throw light on the fibrillation mechanism and can be explored further in designing effective inhibitors against amyloidosis.

Lysozyme amyloidosis-a report on a large German cohort and the characterisation of a novel amyloidogenic lysozyme gene variant

Lysozyme-derived (ALys) amyloidosis is a rare type of hereditary amyloidosis. Nine amyloidogenic variants and ∼30 affected families have been described worldwide. The most common manifestations are renal dysfunction, gastrointestinal tract symptoms, and sicca syndrome. We report on the clinical course of ten patients from six families representing one of the largest cohorts published so far. Seven patients carried the W64R variant showing the whole spectrum of ALys-associated symptoms. Two patients-a mother-son pair-carried a novel lysozyme variant, which was associated with nephropathy and peripheral polyneuropathy. In accordance with previous findings, the phenotype resembled within these families but did not correlate with the genotype. To gain insights into the effect of the variants at the molecular level, we analysed the structure of lysozyme and performed comparative computational predictions on aggregation propensity and conformational stability. Our study supports that decreased conformational stability is a key factor for lysozyme variants to be prone to aggregation. In summary, ALys amyloidosis is a very rare, but still heterogeneous disease that can manifest at an early age. Our newly identified lysozyme variant is associated with nephropathy and peripheral polyneuropathy. Further research is needed to understand its pathogenesis and to enable the development of new treatments.

Insights on Aggregation of Hen Egg-White Lysozyme from Raman Spectroscopy and MD Simulations

Protein misfolding and aggregation play a significant role in several neurodegenerative diseases. In the present work, the spontaneous aggregation of hen egg-white lysozyme (HEWL) in an alkaline pH 12.2 at an ambient temperature was studied to obtain molecular insights. The time-dependent changes in spectral peaks indicated the formation of β sheets and their effects on the backbone and amino acids during the aggregation process. Introducing iodoacetamide revealed the crucial role of intermolecular disulphide bonds amidst monomers in the aggregation process. These findings were corroborated by Molecular Dynamics (MD) simulations and protein-docking studies. MD simulations helped establish and visualize the unfolding of the proteins when exposed to an alkaline pH. Protein docking revealed a preferential dimer formation between the HEWL monomers at pH 12.2 compared with the neutral pH. The combination of Raman spectroscopy and MD simulations is a powerful tool to study protein aggregation mechanisms.

Renal amyloidosis: a new time for a complete diagnosis

Amyloidoses are a group of disorders in which soluble proteins aggregate and deposit extracellularly in tissues as insoluble fibrils, causing organ dysfunction. Clinical management depends on the subtype of the protein deposited and the affected organs. Systemic amyloidosis may stem from anomalous proteins, such as immunoglobulin light chains or serum amyloid proteins in chronic inflammation or may arise from hereditary disorders. Hereditary amyloidosis consists of a group of rare conditions that do not respond to chemotherapy, hence the identification of the amyloid subtype is essential for diagnosis, prognosis, and treatment. The kidney is the organ most frequently involved in systemic amyloidosis. Renal amyloidosis is characterized by acellular pathologic Congo red-positive deposition of amyloid fibrils in glomeruli, vessels, and/or interstitium. This disease manifests with heavy proteinuria, nephrotic syndrome, and progression to end-stage kidney failure. In some situations, it is not possible to identify the amyloid subtype using immunodetection methods, so the diagnosis remains indeterminate. In cases where hereditary amyloidosis is suspected or cannot be excluded, genetic testing should be considered. Of note, laser microdissection/mass spectrometry is currently the gold standard for accurate diagnosis of amyloidosis, especially in inconclusive cases. This article reviews the clinical manifestations and the current diagnostic landscape of renal amyloidosis.

Curcumin-loaded protein imprinted mesoporous nanosphere for inhibiting amyloid aggregation

Some natural variants of human lysozyme are associated with systemic non-neurological amyloidosis that leads to amyloid protein fibril deposition in different tissues. Inhibition of amyloid fibrillation by nanomaterials is considered to be an effective approach to treating amyloidosis. Here, we prepared a targeted, highly loaded curcumin lysozyme-imprinted nanosphere (CUR-MIMS) that could effectively inhibit the aggregation of lysozyme with lysozyme adsorption capacity of 193.57 mg g^-1 and the imprinting factor (IF) of 3.72. CUR-MIMS could bind to lysozyme through hydrophobic interactions and effectively reduce the hydrophobicity of the total solvent-exposed surface in lysozyme fibrillation, thus reducing the self-assembly process triggered by hydrophobic interactions. Thioflavin T (ThT) analysis demonstrated that CUR-MIMS inhibited the aggregation of amyloid fibrils in a dose-dependent manner (inhibition efficiency of 56.07 %). Circular dichroism (CD) spectrum further illustrated that CUR-MIMS could significantly inhibit the transition of lysozyme from α-helix structure to β-sheet. More importantly, biological experiments proved the good biocompatibility of CUR-MIMS, which indicated the potential of our system as a future therapeutic platform for amyloidosis.

Role of salts and solvents on the defibrillation of food dye "sunset yellow" induced hen egg white lysozyme amyloid fibrils

Several food dyes are known to induce amyloid fibrillation when interacting with proteins. Here, we studied the role of sunset yellow (SY) in the amyloid fibrillation of hen egg white lysozyme (HEWL) and characterized the changes using spectroscopy techniques. Turbidity results showed that SY dye induces aggregation in HEWL in concentrations dependent manner. The aggregation induced by SY dye is kinetically very fast, no lag phase was detected, and the kinetics process follows an isodesmic kinetics pathway. The SY-dye induce aggregates have cross-β secondary structure confirmed by far-UV CD measurements. The effect of salts and solvents was also seen on SY-induced aggregates. Turbidity, far-UV CD, and kinetics results suggest that certain concentrations of NaCl and (NH₄)₂SO₄ solubilize the SY-induce amyloid fibrils, but (NH₄)₂SO₄ is more effective. Similarly, solvents are also solubilized the SY-induces HEWL amyloid fibrillation but the order of defibrillation is as follows: Isopropanol> ethanol > methanol which signified that isopropanol is more effective than other solvents. The salts and solvents data suggest that the electrostatic, as well as hydrophobic interaction, is responsible for SY-induced amyloid fibrillation. These conformational changes should be examined, more seriously for the purpose of food safety.

Inhibitory Effect of Epigallocatechin Gallate-Silver Nanoparticles and Their Lysozyme Bioconjugates on Biofilm Formation and Cytotoxicity

Biofilms are multicellular communities of microbial cells that grow on natural and synthetic surfaces. They have become the major cause for hospital-acquired infections because once they form, they are very difficult to eradicate. Nanotechnology offers means to fight biofilm-associated infections. Here, we report on the synthesis of silver nanoparticles (AgNPs) with the antibacterial ligand epigallocatechin gallate (EGCG) and the formation of a lysozyme protein corona on AgNPs, as shown by UV-vis, dynamic light scattering, and circular dichroism analyses. We further tested the activity of EGCG-AgNPs and their lysozyme bioconjugates on the viability of Bacillus subtilis cells and biofilm formation. Our results showed that, although EGCG-AgNPs presented no antibacterial activity on planktonic B. subtilis cells, they inhibited B. subtilis biofilm formation at concentrations larger than 40 nM, and EGCG-AgNP-lysozyme bioconjugates inhibited biofilms at concentrations above 80 nM. Cytotoxicity assays performed with human cells showed a reverse trend, where EGCG-AgNPs barely affected human cell viability while EGCG-AgNP-lysozyme bioconjugates severely hampered viability. Our results therefore demonstrate that EGCG-AgNPs may be used as noncytotoxic antibiofilm agents.

The current state of amyloidosis therapeutics and the potential role of fluorine in their treatment

Amyloidosis, commonly known as amyloid-associated diseases, is characterized by improperly folded proteins accumulating in tissues and eventually causing organ damage, which is linked to several disorders ranging from neurodegenerative to peripheral diseases. It has an enormous societal and financial impact on the global health sector. Due to the complexity of protein misfolding and intertwined aggregation, there are no effective disease-modifying medications at present, and the condition is likely mis/non-diagnosed half of the time. Nonetheless, over the last two decades, substantial research into aggregation processes has revealed the possibilities of new intervention approaches. On the other hand, fluorine has been a rising star in therapeutic development for numerous neurodegenerative illnesses and other peripheral diseases. In this study, we revised and emphasized the possible significance of fluorine-modified therapeutic molecules and fluorine-modified nanoparticles (NPs) in the modulation of amyloidogenic proteins, including insulin, amyloid beta peptide (Aβ), prion protein (PrP), transthyretin (TTR) and Huntingtin (htt).

Pomegranate seed polyphenol-based nanosheets as an efficient inhibitor of amyloid fibril assembly and cytotoxicity of HEWL

Poor water solubility and low bioavailability are considered as two main factors restricting therapeutic applications of natural polyphenols in relation to various disorders including amyloid-related diseases. Among various strategies developed to overcome these limitations, nanonization has attracted considerable attention. Herein, we compared the potency of bulk and nano forms of the polyphenolic fraction of pomegranate seed (PFPS) for modulating Hen Egg White Lysozyme (HEWL) amyloid fibril formation. Prepared PFPS nanosheets using direct oxidative pyrolysis were characterized by employing a range of spectroscopic and microscopic techniques. We found that the nano form can inhibit the assembly process and disintegrate preformed fibrils of HEWL much more effective than the bulk form of PFPS. Moreover, MTT-based cell viability and hemolysis assays showed the capacity of both bulk and nano forms of PFPS in attenuating HEWL amyloid fibril-induced toxicity, where the nano form was more effective. On the basis of thioflavin T results, a delay in the initiation of amyloid fibril assembly of HEWL appears to be the mechanism of action of PFPS nanosheets. We suggest that the improved efficiency of PFPS nanosheets in modulating the HEWL fibrillation process may be attributed to their increased surface area in accord with the surface-assistance model. Our results may present polyphenol-based nanosheets as a powerful approach for drug design against amyloid-related diseases.

PFPS nanosheets modulate the amyloid fibrillation of HEWL much more effective than the bulk form of PFPS. Based on the thioflavin T results, a delay in the initiation of the assembly process appears to be the mechanism of action of PFPS nanosheets.

Lysozyme amyloid fibril: Regulation, application, hazard analysis, and future perspectives

Self-assembly of misfolded proteins into ordered fibrillar aggregates known as amyloid results in various human diseases. However, more and more proteins, whether in human body or in food, have been found to be able to form amyloid fibrils with in-depth researches. As a model protein for amyloid research, lysozyme has always been the focus of research in various fields. Firstly, the formation mechanisms of amyloid fibrils are discussed concisely. Researches on the regulation of lysozyme amyloid fibrils are helpful to find suitable therapeutic drugs and unfriendly substances. And this review article summarizes a number of exogenous substances including small molecules, nanoparticles, macromolecules, and polymers. Small molecules are mainly connected to lysozyme through hydrophobic interaction, electrostatic interaction, π-π interaction, van der Waals force and hydrogen bond. Nanoparticles inhibit the formation of amyloid fibers by stabilizing lysozyme and fixing β-sheet. Besides, the applications of lysozyme amyloid fibrils in food-related fields are considered furtherly due to outstanding physical and mechanical properties. Nevertheless, the potential health threats are still worthy of our attention. Finally, we also give suggestions and opinions on the future research direction of lysozyme amyloid fibrils.

Graphene Oxide/Silver Nanoparticles Platforms for the Detection and Discrimination of Native and Fibrillar Lysozyme: A Combined QCM and SERS Approach

We propose a sensing platform based on graphene oxide/silver nanoparticles arrays (GO/AgNPs) for the detection and discrimination of the native and toxic fibrillar forms of an amyloid-prone protein, lysozyme, by means of a combination of Quartz Crystal Microbalance (QCM) and Surface Enhanced Raman Scattering (SERS) measurements. The GO/AgNPs layer system was obtained by Langmuir-Blodgett assembly of the silver nanoparticles followed by controlled adsorption of GO sheets on the AgNPs array. The adsorption of native and fibrillar lysozyme was followed by means of QCM, the measurements provided the kinetics and the mechanism of adsorption as a function of protein concentration as well as the mass and thickness of the adsorbed protein on both nanoplatforms. The morphology of the protein layer was characterized by Confocal Laser Scanning Microscopy experiments on Thioflavine T-stained samples. SERS experiments performed on arrays of bare AgNPs and of GO coated AgNP after native, or fibrillar, lysozyme adsorption allowed for the discrimination of the native form and toxic fibrillar structure of lysozyme. Results from combined QCM/SERS studies indicate a general construction paradigm for an efficient sensing platform with high selectivity and low detection limit for native and amyloid lysozyme.

Molecular Dynamics of Lysozyme Amyloid Polymorphs Studied by Incoherent Neutron Scattering

Lysozyme amyloidosis is a hereditary disease, which is characterized by the deposition of lysozyme amyloid fibrils in various internal organs. It is known that lysozyme fibrils show polymorphism and that polymorphs formed at near-neutral pH have the ability to promote more monomer binding than those formed at acidic pH, indicating that only specific polymorphs become dominant species in a given environment. This is likely due to the polymorph-specific configurational diffusion. Understanding the possible differences in dynamical behavior between the polymorphs is thus crucial to deepen our knowledge of amyloid polymorphism and eventually elucidate the molecular mechanism of lysozyme amyloidosis. In this study, molecular dynamics at sub-nanosecond timescale of two kinds of polymorphic fibrils of hen egg white lysozyme, which has long been used as a model of human lysozyme, formed at pH 2.7 (LP27) and pH 6.0 (LP60) was investigated using elastic incoherent neutron scattering (EINS) and quasi-elastic neutron scattering (QENS). Analysis of the EINS data showed that whereas the mean square displacement of atomic motions is similar for both LP27 and LP60, LP60 contains a larger fraction of atoms moving with larger amplitudes than LP27, indicating that the dynamical difference between the two polymorphs lies not in the averaged amplitude, but in the distribution of the amplitudes. Furthermore, analysis of the QENS data showed that the jump diffusion coefficient of atoms is larger for LP60, suggesting that the atoms of LP60 undergo faster diffusive motions than those of LP27. This study thus characterizes the dynamics of the two lysozyme polymorphs and reveals that the molecular dynamics of LP60 is enhanced compared with that of LP27. The higher molecular flexibility of the polymorph would permit to adjust its conformation more quickly than its counterpart, facilitating monomer binding.

Anti-amyloidogenic property of gold nanoparticle decorated quercetin polymer nanorods in pH and temperature induced aggregation of lysozyme

Quercetin is an abundant plant polyphenol effective against several diseases due to its antioxidant and anti-inflammatory activity. Herein, we report novel polymeric quercetin nanorods and the former decorated with gold nanoparticles for the first time. The prepared conjugates quercetin-polyvinylpyrrolidone (Q-PVP) and quercetin-polyvinylpyrrolidone-gold nanoparticles (Q-PVP-Au) were characterized by UV-visible spectroscopy, Fourier transform infrared, dynamic light scattering, and zeta potential measurements. The surface morphology of conjugates was analyzed by field emission scanning electron microscopy. These conjugates exhibit harmonized rod-like morphology with a narrow size distribution. Furthermore, the quercetin conjugates with nanorod morphology exhibited enhanced and prolonged drug release over a long period. The synthesized conjugates were investigated for lysozyme aggregation kinetics. ThT binding assay, fibril size measurement, and electron microscopy results revealed that conjugates could suppress fibrillogenesis in lysozyme. The highest amyloid aggregation inhibition activity (IC₅₀) was obtained against Q-PVP and Q-PVP-Au at 32 μg mL⁻¹ and 30 μg mL⁻¹ respectively. The amyloid aggregate disintegration activity (DC₅₀) obtained against Q-PVP and Q-PVP-Au was 27 μg mL⁻¹ and 29 μg mL⁻¹ respectively. The present quercetin conjugates exhibit enhanced bioavailability and stability. They were potent inhibitors of lysozyme aggregation that may find applications as a therapeutic agent in neurological diseases like Alzheimer's and Parkinson's.

Q-PVP, and Q-PVP-Au conjugates for inhibition of HEWL aggregation.

Inhibition of the formation of lysozyme fibrillar assemblies by the isoquinoline alkaloid coralyne

The isoquinoline alkaloid coralyne can efficiently attenuate fibrillogenesis in lysozyme.

Inhibition and disruption of amyloid formation by the antibiotic levofloxacin: A new direction for antibiotics in an era of multi-drug resistance

Neurodegenerative diseases are a group of debilitating maladies involving protein aggregation. To this day, all advances in neurodegenerative disease therapeutics have helped symptomatically but have not prevented the root cause of the disease, i.e., the aggregation of involved proteins. Antibiotics are becoming increasingly obsolete due to the rising multidrug resistance strains of bacteria. Thus, antibiotics, if put to different use as therapeutics against other diseases, could pave a new direction to the world of antibiotics. Hence, we studied the antibiotic levofloxacin for its potential anti-amyloidogenic behavior using human lysozyme, a protein involved in non-systemic amyloidosis, as a model system. At the sub-stoichiometric level, levofloxacin was able to inhibit amyloid formation in human lysozyme as observed by various spectroscopic and microscopic methods, with IC₅₀ values as low as 8.8 ± 0.1 μM. Levofloxacin also displayed a retarding effect on seeding phenomena by elongating the lag-phase (from 0 to 88 h) at lower concentration, and arresting lysozyme fibrillation at the lag stage in sub-stoichiometric concentrations. Structural and computational analyses provided mechanistic insight showing that levofloxacin stabilizes the lysozyme in the native state by binding to the aggregation-prone residues, and thereby inhibiting amyloid fibrillation. Levofloxacin also showed the property of disrupting amyloid fibrils into a smaller polymeric form of proteins which were less cytotoxic as confirmed by hemolytic assay. Therefore, we throw new light on levofloxacin as an amyloid inhibitor and disruptor which could pave way to utilization of levofloxacin as a potential therapeutic against non-systemic amyloidosis and neurodegenerative diseases.

Targeting disorders in unstructured and structured proteins in various diseases

Intrinsically disordered proteins (IDPs) and intrinsically disordered protein regions (IDPRs) are proteins and protein segments that usually do not acquire well-defined folded structures even under physiological conditions. They are abundantly present and challenge the "one sequence-one structure-one function" theory due to a lack of stable secondary and/or tertiary structure. Due to conformational flexibility, IDPs/IDPRs can bind with multiple interacting partners with high-specificity and low-affinity and perform essential biological functions associated with signalling, recognition and regulation. Mis-functioning and mis-regulation of IDPs and IDPRs causes disorder in disordered proteins and disordered protein segments which results in numerous human diseases, such as cancer, Parkinson's disease (PD), Alzheimer's disease (AD), diabetes, metabolic disorders, systemic disorders and so on. Due to the strong connection of IDPs/IDPRs with human diseases they are considered potentential targets for drug therapy. Since they disobey the "one sequence-one structure-one function" concept, IDPs/IDPRs are complex systems for drug targeting. This review summarises various protein disorder diseases and different methods for therapeutic targeting of disordered proteins/segments. Targeting IDPs/IDPRs for diseases will open up a new era of rational drug design and drug discovery.

The impact of folding modes and deuteration on the atomic resolution structure of hen egg-white lysozyme

The biological function of a protein is intimately related to its structure and dynamics, which in turn are determined by the way in which it has been folded. In vitro refolding is commonly used for the recovery of recombinant proteins that are expressed in the form of inclusion bodies and is of central interest in terms of the folding pathways that occur in vivo. Here, biophysical data are reported for in vitro-refolded hydrogenated hen egg-white lysozyme, in combination with atomic resolution X-ray diffraction analyses, which allowed detailed comparisons with native hydrogenated and refolded perdeuterated lysozyme. Distinct folding modes are observed for the hydrogenated and perdeuterated refolded variants, which are determined by conformational changes to the backbone structure of the Lys97-Gly104 flexible loop. Surprisingly, the structure of the refolded perdeuterated protein is closer to that of native lysozyme than that of the refolded hydrogenated protein. These structural differences suggest that the observed decreases in thermal stability and enzymatic activity in the refolded perdeuterated and hydrogenated proteins are consequences of the macromolecular deuteration effect and of distinct folding dynamics, respectively. These results are discussed in the context of both in vitro and in vivo folding, as well as of lysozyme amyloidogenesis.

A Pilot Study of Rare Renal Amyloidosis Based on FFPE Proteomics

Renal amyloidosis typically manifests albuminuria, nephrotic-range proteinuria, and ultimately progresses to end-stage renal failure if diagnosed late. Different types of renal amyloidosis have completely different treatments and outcomes. Therefore, amyloidosis typing is essential for disease prognosis, genetic counseling and treatment. Thirty-six distinct proteins currently known to cause amyloidosis that have been described as amyloidogenic precursors, immunohistochemistry (IHC) or immunofluorescence (IF), can be challenging for amyloidosis typing especially in rare or hereditary amyloidosis in clinical practice. We made a pilot study that optimized the proteomics pre-processing procedures for trace renal amyloidosis formalin-fixed paraffin-embedded (FFPE) tissue samples, combined with statistical and bioinformatics analysis to screen out the amyloidosis-related proteins to accurately type or subtype renal amyloidosis in order to achieve individual treatment. A sensitive, specific and reliable FFPE-based proteomics analysis for trace sample manipulation was developed for amyloidosis typing. Our results not only underlined the great promise of traditional proteomics and bioinformatics analysis using FFPE tissues for amyloidosis typing, but also proved that retrospective diagnosis and analysis of previous cases laid a solid foundation for personalized treatment.

The role of amyloids in Alzheimer's and Parkinson's diseases

With varying clinical symptoms, most neurodegenerative diseases are associated with abnormal loss of neurons. They share the same common pathogenic mechanisms involving misfolding and aggregation, and these visible aggregates of proteins are deposited in the central nervous system. Amyloid formation is thought to arise from partial unfolding of misfolded proteins leading to the exposure of hydrophobic surfaces, which interact with other similar structures and give rise to form dimers, oligomers, protofibrils, and eventually mature fibril aggregates. Accumulating evidence indicates that amyloid oligomers, not amyloid fibrils, are the most toxic species that causes Alzheimer's disease (AD) and Parkinson's disease (PD). AD has recently been recognized as the 'twenty-first century plague', with an incident rate of 1% at 60 years of age, which then doubles every fifth year. Currently, 5.3 million people in the US are afflicted with this disease, and the number of cases is expected to rise to 13.5 million by 2050. PD, a disorder of the brain, is the second most common form of dementia, characterized by difficulty in walking and movement. Keeping the above views in mind, in this review we have focused on the roles of amyloid in neurodegenerative diseases including AD and PD, the involvement of amyloid in mitochondrial dysfunction leading to neurodegeneration, are also considered in the review.

Man does not live by intrinsically unstructured proteins alone: The role of structured regions in aggregation

Protein misfolding is a topic that is of primary interest both in biology and medicine because of its impact on fundamental processes and disease. In this review, we revisit the concept of protein misfolding and discuss how the field has evolved from the study of globular folded proteins to focusing mainly on intrinsically unstructured and often disordered regions. We argue that this shift of paradigm reflects the more recent realisation that misfolding may not only be an adverse event, as originally considered, but also may fulfil a basic biological need to compartmentalise the cell with transient reversible granules. We nevertheless provide examples in which structure is an important component of a much more complex aggregation behaviour that involves both structured and unstructured regions of a protein. We thus suggest that a more comprehensive evaluation of the mechanisms that lead to aggregation might be necessary.

A study on the interaction of the amyloid fibrils of α-synuclein and hen egg white lysozyme with biological membranes

Alpha-synuclein (α-syn) aggregation and mitochondrial dysfunction are considered as two of the main factors associated with Parkinson's disease (PD). In the present investigation, the effectiveness of the amyloid fibrils obtained from α-syn with those of hen egg white lysozyme (HEWL), as disease-related and-unrelated proteins, to damage rat brain and rat liver mitochondria have been investigated. This was extended by looking at SH-SY5Y human neuroblastoma cells and erythrocytes, thereby investigating the significance of structural characteristics of amyloid fibrils related to their interactions with biomembranes obtained from various sources. Results presented clearly demonstrate substantial differences in the response of tested biomembranes to toxicity induced by α-syn/HEWL amyloid fibrils, highlighting a structure-function relationship. We found that fibrillar aggregates of α-syn, but not HEWL, caused a significant increase in mitochondrial ROS, loss of membrane potential, and mitochondrial swelling, in a dose-dependent manner. Toxicity was found to be more pronounced in brain mitochondria, as compared to liver mitochondria. For SH-SY5Y cells and erythrocytes, however, both α-syn and HEWL amyloid fibrils showed the capacity to induce toxicity. Taken together, these results may suggest selective toxicity of α-syn amyloid fibrils to mitochondria mediated likely by their direct interaction with the outer mitochondrial membrane, indicating a correlation between specific structural characteristics of α-syn fibrils and an organelle strongly implicated in PD pathology.

Systemic Amyloidosis: a Contemporary Overview

Amyloidosis constitutes a large spectrum of diseases characterized by an extracellular deposition of a fibrillar aggregate, generating insoluble and toxic amasses that may be deposited in tissues in bundles with an abnormal cross-β-sheet conformation, known as amyloid. Amyloid may lead to a cell damage and an impairment of organ function. Several different proteins are recognized as able to produce amyloid fibrils with a different tissue tropism related to the molecular structure. The deposition of amyloid may occur as a consequence of the presence of an abnormal protein, caused by high plasma levels of a normal protein, or as a result of the aging process along with some environmental factors. Although amyloidosis is rare, amyloid deposits play a role in several conditions as degenerative diseases. Thus, the development of antiamyloid curative treatments may be a rational approach to treat neurodegenerative conditions like Alzheimer's disease in the future. Nowadays, novel treatment options are currently refined through controlled trials, as new drug targets and different therapeutic approaches have been identified and validated through modern advances in basic research. Fibril formation stabilizers, proteasome inhibitors, and immunotherapy revealed promising results in improving the outcomes of patients with systemic amyloidosis, and these novel algorithms will be effectively combined with current treatments based on chemotherapeutic regimens. The aim of this review is to provide an update on diagnosis and treatment for systemic amyloidosis.

Clinical ApoA-IV amyloid is associated with fibrillogenic signal sequence

Apolipoprotein A‐IV amyloidosis is an uncommon form of the disease normally resulting in renal and cardiac dysfunction. ApoA‐IV amyloidosis was identified in 16 patients attending the National Amyloidosis Centre and in eight clinical samples received for histology review. Unexpectedly, proteomics identified the presence of ApoA‐IV signal sequence residues (p.18‐43 to p.20‐43) in 16/24 trypsin‐digested amyloid deposits but in only 1/266 non‐ApoA‐IV amyloid samples examined. These additional signal residues were also detected in the cardiac sample from the Swedish patient in which ApoA‐IV amyloid was first described, and in plasma from a single cardiac ApoA‐IV amyloidosis patient. The most common signal‐containing peptide observed in ApoA‐IV amyloid, p.20‐43, and to a far lesser extent the N‐terminal peptide, p.21‐43, were fibrillogenic in vitro at physiological pH, generating Congo red‐positive fibrils. The addition of a single signal‐derived alanine residue to the N‐terminus has resulted in markedly increased fibrillogenesis. If this effect translates to the mature circulating protein in vivo, then the presence of signal may result in preferential deposition as amyloid, perhaps acting as seed for the main circulating native form of the protein; it may also influence other ApoA‐IV‐associated pathologies. © 2021 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

Understanding the Role of Protein Glycation in the Amyloid Aggregation Process

Protein function and flexibility is directly related to the native distribution of its structural elements and any alteration in protein architecture leads to several abnormalities and accumulation of misfolded proteins. This phenomenon is associated with a range of increasingly common human disorders, including Alzheimer and Parkinson diseases, type II diabetes, and a number of systemic amyloidosis characterized by the accumulation of amyloid aggregates both in the extracellular space of tissues and as intracellular deposits. Post-translational modifications are known to have an active role in the in vivo amyloid aggregation as able to affect protein structure and dynamics. Among them, a key role seems to be played by non-enzymatic glycation, the most unwanted irreversible modification of the protein structure, which strongly affects long-living proteins throughout the body. This study provided an overview of the molecular effects induced by glycation on the amyloid aggregation process of several protein models associated with misfolding diseases. In particular, we analyzed the role of glycation on protein folding, kinetics of amyloid formation, and amyloid cytotoxicity in order to shed light on the role of this post-translational modification in the in vivo amyloid aggregation process.

Discovery of a tetracyclic indole alkaloid that postpones fibrillation of hen egg white lysozyme protein

Protein aggregation, such as amyloid fibril formation, is molecular hallmark of many neurodegenerative disorders including Alzheimer's, Parkinson's, and Prion disease. Indole alkaloids are well-known as the compounds having the ability to inhibit protein fibrillation. In this study, we experimentally and computationally have investigated the anti-amyloid property of a derivative of a synthesized tetracyclic indole alkaloid (TCIA), possessing capable functional groups. The fibrillation reaction of Hen White Egg Lysozyme (HEWL) was performed in absence and presence of the indole alkaloid. For quantitative analysis, we used Thioflovin T binding assay which showed ~50% reduction in fibril formation in the presence of 20 μM TCIA. Using TEM imaging, we observed a significant morphological change in our model protein in the presence of TCIA. In addition, we exploited FT-IR assay by which Amide I peak's shifting toward lower wavenumber was clearly observed. Using Molecular Docking, the interaction of the inhibitor (TCIA) with the protein's amyloidogenic region was modeled. Also, different biophysical parameters were calculated by Molecular Dynamics (MD) simulation. Various biochemical assays, conformational change, and hydrophobicity exposure of the protein during amyloid formation indicated that the compound assists HEWL to keep its native structure via destabilizing β-sheet structure.

Free energy simulations to understand the effect of Met → Ala mutations at positions 205, 206 and 213 on stability of human prion protein

Prion diseases are a family of infectious amyloid diseases affecting human and animals. Prion propagation in transmissible spongiform encephalopathies is associated with the unfolding and conversion of normal cellular prion protein into its pathogenic scrapie form. Understanding the fundamentals of prion protein aggregation caused by mutations is crucial to unravel the pathology of prion diseases. To help understand the contributions of individual residues to the stability of the human prion protein, we have carried out free energy simulations based on atomistic molecular dynamics trajectories. We focus on Met → Ala mutations at positions 205, 206 and 213, which are mostly buried residues located on helix 3 of the protein. The simulations predicted that all three mutations destabilize the prion protein. Changes in unfolding free energy upon mutation, ∆∆G, are 3.10 ± 0.79, 2.00 ± 0.26 and 3.06 ± 0.66 kcal/mol for M205A, M206A and M213A, respectively, in excellent agreement with the corresponding experimental values of 3.09 ± 0.28, 1.50 ± 0.34 and 3.12 ± 0.27 kcal/mol [T. Hart et al. (2009) PNAS 106, 5651-5656]. Component analysis indicates that the major contributions to the loss of protein stability arise from van der Waals interactions for the M205A and M206A mutations, and from van der Waals and covalent energy terms for M213A. Interestingly, while free energy contributions from a majority of residues neighboring the mutation sites tend to stabilize the wild type, there are a few residues stabilizing the mutant side chains. Our results show that this approach to free energy calculation can be very useful for understanding the detailed mechanism of human prion protein stability.

Elevated temperatures accelerate the formation of toxic amyloid fibrils of hen egg-white lysozyme

The formation of amyloid fibrils is critical for neurodegenerative diseases. Some physiochemical conditions can promote the conversion of proteins from soluble globular shapes into insoluble well‐organized amyloid fibrils. The aim of this study was to investigate the effect of temperatures on amyloid fibrils formation in vitro using the protein model of hen egg‐white lysozyme (HEWL). The HEWL fibrils were prepared at temperatures of 37, 45, 50 and 57°C in glycine solution of pH 2.2. Under transmission electron microscopy, we found the well‐organized HEWL amyloid fibrils at temperatures of 45, 50 and 57°C after 10 days of incubation. Thioflavin T and Congo red florescence assays confirmed that the formation and growth of HEWL fibrils displayed a temperature‐dependent increase, and 57°C produced the most amounts. Meanwhile, the surface hydrophobicity of aggregates was greatly increased by ANS binding assay, and β‐sheet contents by circular dichroism analysis were increased by 17.8%, 22.0% and 34.9%, respectively. Furthermore, the HEWL fibrils formed at 57°C caused significant cytotoxicity in SH‐SY5Y cells after 48 hr exposure, and the cell viability determined by MTT assay was decreased, with 81.35 ± 0.29% for 1 μM, 61.45 ± 2.62% for 2 μM, and 11.58 ± 0.39% (p < .01) for 3 μM. Nuclear staining results also confirmed the apoptosis features. These results suggest that the elevated temperatures could accelerate protein unfolding of the native structure and formation of toxic amyloid fibrils, which can improve understanding the mechanisms of the unfolding and misfolding process of prion protein.