Self-oligomerization and protein aggregation of alpha-synuclein in the presence of Coomassie Brilliant Blue

Onosma glomeratum Y. L. Liu polysaccharide alleviates LPS-induced pulmonary inflammation via NF-κB signal pathway

As a traditional Chinese medicinal and edible homologous plant, Onosma glomeratum Y. L. Liu has been used for treating lung diseases in Tibet. In this study, a pectin polysaccharide, OGY-LLPA, with a molecular weight of 62,184 Da, was isolated and characterized by GC-MS and NMR analysis. It mainly consists of galacturonic acid (GalA), galactose (Gal), rhamnose (Rha), and arabinose (Ara), with a linear main chain of galacturonic acid (homogalacturonan, HG) inserted by part of rhamnose galacturonic acid (rhamnogalacturonan, RG), attaching with arabinogalactan (AG) branches at RG-I. Both in the LPS-induced A549 cell model and LPS-induced pneumonia mouse model, OGY-LLPA demonstrated strong anti-inflammatory effects, even comparable to DEX, indicating its potential as an anti-pneumonia candidate agent. Moreover, low-dose OGY-LLPA alleviated LPS-induced pulmonary inflammation by inhibiting the NF-κB signaling pathway. Overall, these findings could not only contribute to the utilization of Onosma glomeratum Y. L. Liu., but also provides a theoretical basis for the treatment of inflammation-related diseases.

Animal Models for the Investigation of P2X7 Receptors

The P2X7 receptor is a trimeric ligand-gated cation channel activated by extracellular adenosine 5'-triphosphate. The study of animals has greatly advanced the investigation of P2X7 and helped to establish the numerous physiological and pathophysiological roles of this receptor in human health and disease. Following a short overview of the P2X7 distribution, roles and functional properties, this article discusses how animal models have contributed to the generation of P2X7-specific antibodies and nanobodies (including biologics), recombinant receptors and radioligands to study P2X7 as well as to the pharmacokinetic testing of P2X7 antagonists. This article then outlines how mouse and rat models have been used to study P2X7. These sections include discussions on preclinical disease models, polymorphic P2X7 variants, P2X7 knockout mice (including bone marrow chimeras and conditional knockouts), P2X7 reporter mice, humanized P2X7 mice and P2X7 knockout rats. Finally, this article reviews the limited number of studies involving guinea pigs, rabbits, monkeys (rhesus macaques), dogs, cats, zebrafish, and other fish species (seabream, ayu sweetfish, rainbow trout and Japanese flounder) to study P2X7.

Involvement of molecular chaperone in protein-misfolding brain diseases

Protein misfolding causes aggregation and build-up in a variety of brain diseases. There are numeral molecules that are linked with the protein homeostasis mechanism. Molecular chaperones are one of such molecules that are responsible for protection against protein misfolded and aggregation-induced neurotoxicity. Many studies have explored the participation of molecular chaperones in Parkinson's disease, Alzheimer's disease, Amyotrophic lateral sclerosis, and Huntington's diseases. In this review, we highlighted the constructive role of molecular chaperones in neurological diseases characterized by protein misfolding and aggregation and their capability to control aberrant protein interactions at an early stage thus successfully suppressing pathogenic cascades. A comprehensive understanding of the protein misfolding associated with brain diseases and the molecular basis of involvement of chaperone against aggregation-induced cellular stress might lead to the progress of new therapeutic intrusion-related to protein misfolding and aggregation.

In vitro models of synucleinopathies: informing on molecular mechanisms and protective strategies

Alpha-synuclein (α-Syn) is a central player in Parkinson's disease (PD) and in a spectrum of neurodegenerative diseases collectively known as synucleinopathies. The protein was first associated with PD just over 20 years ago, when it was found to (i) be a major component of Lewy bodies and (ii) to be also associated with familial forms of PD. The characterization of α-Syn pathology has been achieved through postmortem studies of human brains. However, the identification of toxic mechanisms associated with α-Syn was only achieved through the use of experimental models. In vitro models are highly accessible, enable relatively rapid studies, and have been extensively employed to address α-Syn-associated neurodegeneration. Given the diversity of models used and the outcomes of the studies, a cumulative and comprehensive perspective emerges as indispensable to pave the way for further investigations. Here, we subdivided in vitro models of α-Syn pathology into three major types: (i) models simulating α-Syn fibrillization and the formation of different aggregated structures in vitro, (ii) models based on the intracellular expression of α-Syn, reporting on pathogenic conditions and cellular dysfunctions induced, and (iii) models using extracellular treatment with α-Syn aggregated species, reporting on sites of interaction and their downstream consequences. In summary, we review the underlying molecular mechanisms discovered and categorize protective strategies, in order to pave the way for future studies and the identification of effective therapeutic strategies. This article is part of the Special Issue "Synuclein".

High-Density Single-Layer Coating of Gold Nanoparticles onto Multiple Substrates by Using an Intrinsically Disordered Protein of α-Synuclein for Nanoapplications

Functional graffiti of nanoparticles onto target surface is an important issue in the development of nanodevices. A general strategy has been introduced here to decorate chemically diverse substrates with gold nanoparticles (AuNPs) in the form of a close-packed single layer by using an omni-adhesive protein of α-synuclein (αS) as conjugated with the particles. Since the adsorption was highly sensitive to pH, the amino acid sequence of αS exposed from the conjugates and its conformationally disordered state capable of exhibiting structural plasticity are considered to be responsible for the single-layer coating over diverse surfaces. Merited by the simple solution-based adsorption procedure, the particles have been imprinted to various geometric shapes in 2-D and physically inaccessible surfaces of 3-D objects. The αS-encapsulated AuNPs to form a high-density single-layer coat has been employed in the development of nonvolatile memory, fule-cell, solar-cell, and cell-culture platform, where the outlying αS has played versatile roles such as a dielectric layer for charge retention, a sacrificial layer to expose AuNPs for chemical catalysis, a reaction center for silicification, and biointerface for cell attachment, respectively. Multiple utilizations of the αS-based hybrid NPs, therefore, could offer great versatility to fabricate a variety of NP-integrated advanced materials which would serve as an indispensable component for widespread applications of high-performance nanodevices.

Reduction of cytotoxicity of benzalkonium chloride and octenidine by Brilliant Blue G

The irritative effects of preservatives found in ophthalmologic solution, or of antiseptics used for skin disinfection is a consistent problem for the patients. The reduction of the toxic effects of these compounds is desired. Brilliant Blue G (BBG) has shown to meet the expected effect in presence of benzalkonium chloride (BAK), a well known preservative in ophthalmic solutions, and octenidine dihydrochloride (Oct), used as antiseptic in skin and wound disinfection. BBG shows a significant protective effect on human corneal epithelial (HCE) cells against BAK and Oct toxicity, increasing the cell survival up to 51 % at the highest BAK or Oct concentration tested, which is 0.01 %, both at 30 min incubation. Although BBG is described as a P2x7 receptor antagonist, other selective P2x7 receptor antagonists, OxATP (adenosine 5’-triphosphate-2’,3’-dialdehyde) and DPPH (N’-(3,5-dichloropyridin-4-yl)-3-phenylpropanehydrazide), did not reduce the cytotoxicity of neither BAK nor Oct. Therefore we assume that the protective effect of BBG is not due to its action on the P2x7 receptor. Brilliant Blue R (BBR), a dye similar to BBG, was also tested for protective effect on BAK and Oct toxicity. In presence of BAK no significant protective effect was observed. Instead, with Oct a comparable protective effect was seen with that of BBG. To assure that the bacteriostatic effect is not affected by the combinations of BAK/BBG, Oct/BBG and Oct/BBR, bacterial growth inhibition was analyzed on different Gram-negative and Gram-positive bacteria. All combinations of BAK or Oct with BBG hinder growth of Gram-positive bacteria. The combinations of 0.001 % Oct and BBR above 0.025 % do not hinder the growth of B. subtilis. For Gram-negative bacteria, BBG and BBR reduce, but do not abolish, the antimicrobial effect of BAK nor of Oct. In conclusion, the addition of BBG at bacterial inhibitory concentrations is suggested in the ready-to-use ophthalmic preparations and antiseptic solutions.

Robust polydiacetylene-based colorimetric sensing material developed with amyloid fibrils of α-synuclein

Robust polydiacetylene-based colorimetric sensing material has been developed with amyloid fibrils of α-synuclein in the presence of 10,12-pentacosadiynoic acid (PCDA) by taking advantage of the specific fatty acid interaction of α-synuclein and structural regularity of the self-assembled product of amyloid fibrils. PCDA facilitated not only self-oligomerization of α-synuclein but also its fibrillation into the fibrils with increased thickness. Upon UV irradiation, the PCDA-containing amyloid fibrils (AF-PCDAs) turned blue, which then became red following heat treatment. The blue-to-red color transition was also observed with other stimuli of pH and ethanol. AF-PCDAs were demonstrated to be mechanically stable since not only the individual colors of blue and red but also their colorimetric transition were not affected by a number of sonications which readily disrupted the polydiaceylene (PDA) vesicles with the instant loss of color. Therefore, AF-PCDA can be considered to be a novel PDA-based colorimetric sensing material with high mechanical strength, which has the potential to be employed in various areas involving advanced sensing technologies.

Applying chaperones to protein-misfolding disorders: molecular chaperones against α-synuclein in Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the accumulation of a protein called α-synuclein (α-syn) into inclusions known as lewy bodies (LB) within neurons. This accumulation is also due to insufficient formation and activity of dopamine produced in certain neurons within the substantia nigra. Lewy bodies are the pathological hallmark of the idiopathic disorder and the cascade that allows α-synuclein to misfold, aggregate and form these inclusions has been the subject of intensive research. Targeting these early steps of oligomerization is one of the main therapeutic approaches in order to develop neurodegenerative-modifying agents. Because the folding and refolding of alpha synuclein is the key point of this cascade, we are interested in this review to summarize the role of some molecular chaperones proteins such as Hsp70, Hsp90 and small heat shock proteins (sHsp) and Hsp 104. Hsp70 and its co-chaperone, Hsp70 and small heat shock proteins can prevent neurodegeneration by preventing α-syn misfolding, oligomerization and aggregation in vitro and in Parkinson disease animal models. Hsp104 is able to resolve disordered protein aggregates and cross beta amyloid conformers. Together, these chaperones have a complementary effect and can be a target for therapeutic intervention in PD.

Techniques for Monitoring Protein Misfolding and Aggregation in Vitro and in Living Cells

Protein misfolding and aggregation have been considered important in understanding many neurodegenerative diseases and recombinant biopharmaceutical production. Therefore, various traditional and modern techniques have been utilized to monitor protein aggregation in vitro and in living cells. Fibril formation, morphology and secondary structure content of amyloidogenic proteins in vitro have been monitored by molecular probes, TEM/AFM, and CD/FTIR analyses, respectively. Protein aggregation in living cells has been qualitatively or quantitatively monitored by numerous molecular folding reporters based on either fluorescent protein or enzyme. Aggregation of a target protein is directly correlated to the changes in fluorescence or enzyme activity of the folding reporter fused to the target protein, which allows non-invasive monitoring aggregation of the target protein in living cells. Advances in the techniques used to monitor protein aggregation in vitro and in living cells have greatly facilitated the understanding of the molecular mechanism of amyloidogenic protein aggregation associated with neurodegenerative diseases, optimizing culture conditions to reduce aggregation of biopharmaceuticals expressed in living cells, and screening of small molecule libraries in the search for protein aggregation inhibitors.

α-Synuclein in central nervous system and from erythrocytes, mammalian cells, and Escherichia coli exists predominantly as disordered monomer

Since the discovery and isolation of α-synuclein (α-syn) from human brains, it has been widely accepted that it exists as an intrinsically disordered monomeric protein. Two recent studies suggested that α-syn produced in Escherichia coli or isolated from mammalian cells and red blood cells exists predominantly as a tetramer that is rich in α-helical structure (Bartels, T., Choi, J. G., and Selkoe, D. J. (2011) Nature 477, 107-110; Wang, W., Perovic, I., Chittuluru, J., Kaganovich, A., Nguyen, L. T. T., Liao, J., Auclair, J. R., Johnson, D., Landeru, A., Simorellis, A. K., Ju, S., Cookson, M. R., Asturias, F. J., Agar, J. N., Webb, B. N., Kang, C., Ringe, D., Petsko, G. A., Pochapsky, T. C., and Hoang, Q. Q. (2011) Proc. Natl. Acad. Sci. 108, 17797-17802). However, it remains unknown whether or not this putative tetramer is the main physiological form of α-syn in the brain. In this study, we investigated the oligomeric state of α-syn in mouse, rat, and human brains. To assess the conformational and oligomeric state of native α-syn in complex mixtures, we generated α-syn standards of known quaternary structure and conformational properties and compared the behavior of endogenously expressed α-syn to these standards using native and denaturing gel electrophoresis techniques, size-exclusion chromatography, and an oligomer-specific ELISA. Our findings demonstrate that both human and rodent α-syn expressed in the central nervous system exist predominantly as an unfolded monomer. Similar results were observed when human α-syn was expressed in mouse and rat brains as well as mammalian cell lines (HEK293, HeLa, and SH-SY5Y). Furthermore, we show that α-syn expressed in E. coli and purified under denaturing or nondenaturing conditions, whether as a free protein or as a fusion construct with GST, is monomeric and adopts a disordered conformation after GST removal. These results do not rule out the possibility that α-syn becomes structured upon interaction with other proteins and/or biological membranes.

Real-time analysis of amyloid fibril formation of α-synuclein using a fibrillation-state-specific fluorescent probe of JC-1

α-Synuclein is a pathological component of PD (Parkinson's disease) by participating in Lewy body formation. JC-1 (5,5′,6,6′-tetrachloro-1,1,3,3′-tetraethylbenzimidazolyl carbocyanine iodide) has been shown to interact with α-synuclein at the acidic C-terminal region with a Kd of 2.6 μM. JC-1 can discriminated between the fibrillation states of α-synuclein (monomeric, oligomeric intermediate and fibrillar forms) by emitting the enhanced binding fluorescence of different colours at 590, 560 and 538 nm respectively with the common excitation at 490 nm. The fibrillation-state-specific interaction of JC-1 allowed us to perform real-time analyses of the α-synuclein fibrillation in the presence of iron as a fibrillation inducer, rifampicin as a fibrillation inhibitor, baicalein as a defibrillation agent and dequalinium as a protofibril inducer. In addition, various α-synuclein fibrils with different morphologies prepared with specific ligands such as metal ions, glutathione, eosin and lipids were monitored with their characteristic JC-1-binding fluorescence spectra. FRET (fluorescence resonance energy transfer) between thioflavin-T and JC-1 was also employed to specifically identify the amyloid fibrils of α-synuclein. Taken together, we have introduced JC-1 as a powerful and versatile probe to explore the molecular mechanism of the fibrillation process of α-synuclein in vitro. It could be also useful in high-throughput drug screening. The specific α-synuclein interaction of JC-1 would therefore contribute to our complete understanding of the molecular aetiology of PD and eventual development of diagnostic/therapeutic strategies for various α-synucleinopathies.

Examination of dye-protein interaction by gel-permeation chromatography

The interaction of Cibacron blue F3G-A with two therapeutic proteins, recombinant human growth hormone and recombinant human interferon-alpha2b, has been examined by applying gel-permeation chromatography in combination with the absorption difference spectroscopy. The complexes of these proteins with Cibacron blue F3G-A have been isolated, and their absorbance spectra have been registered. The influence of Cibacron blue F3G-A on the oligomeric state of proteins has been investigated. It was found that Cibacron blue F3G-A promotes the generation of interferon-alpha2b dimers at pH 5.0.

Dequalinium-induced Protofibril Formation of α-Synuclein

alpha-Synuclein is the major constituent of Lewy bodies, a pathological signature of Parkinson disease, found in the degenerating dopaminergic neurons of the substantia nigra pars compacta. Amyloidosis generating the insoluble fibrillar protein deposition has been considered to be responsible for the cell death observed in the neurodegenerative disorder. In order to develop a controlling strategy toward the amyloid formation, 1,1'-(1,10-decanediyl)-bis-[4-a-mino-2-methylquinolinium] (dequalinium), was selected and examined in terms of its specific molecular interaction with alpha-synuclein. The protein was self-oligomerized by dequalinium, which gave rise to the ladder formation on N-[2-hydroxy-1,1-bis(hydroxymethyl)ethyl]glycine/SDS-PAGE in the presence of a coupling reagent of N-(ethoxycarbonyl)-2-ethoxy-1,2-dihydroquinoline. The double-headed structure of dequalinium with the two cationic 4-aminoquinaldinium rings was demonstrated to be critical for the protein self-oligomerization. The dequalinium-binding site was located on the acidic C-terminal region of the protein with an approximate dissociation constant of 5.5 mum. The protein self-oligomerization induced by the compound has resulted in the protofibril formation of alpha-synuclein before it has developed into amyloids. The protofibrils were demonstrated to affect the membrane intactness of liposomes, and they have also been shown to influence cell viability of human neuroblastoma cells. In addition, dequalinium treatment of the alpha-synuclein-overexpressing cells exerted a significant cell death. Therefore, it is pertinent to consider that dequalinium could be used as a molecular probe to assess toxic mechanisms related to the amyloid formation of alpha-synuclein. Ultimately, the compound could be employed to develop therapeutic and preventive strategies toward alpha-synucleinopathies including Parkinson disease.

Lipid interaction of alpha-synuclein during the metal-catalyzed oxidation in the presence of Cu2+ and H2O2

Alpha-synuclein co-exists with lipids in the Lewy bodies, a pathological hallmark of Parkinson's disease. Molecular interaction between alpha-synuclein and lipids has been examined by observing lipid-induced protein self-oligomerization in the presence of a chemical coupling reagent of N-(ethoxycarbonyl)-2-ethoxy-1,2-dihydroquinoline. Lipids such as phosphatidic acid, phosphatidylinositol, phosphatidylserine, phosphatidylethanolamine, and even arachidonic acid induced the self-oligomerization whereas phosphatidylcholine did not affect the protein. Because the oligomerizations occurred from critical micelle concentrations of the lipids, the self interaction of alpha-synuclein was shown to be a lipid-surface dependent phenomenon with head group specificity. By employing beta-synuclein and a C-terminally truncated alpha-synuclein (alpha-syn97), the head-group dependent self-oligomerization was demonstrated to occur preferentially at the N-terminal region while the fatty acid interaction leading to the protein self-association required the presence of the acidic C-terminus of alpha-synuclein. In the presence of Cu2+ and H2O2, phosphatidylinositol (PI), along with other acidic lipids, actually enhanced the metal-catalyzed oxidative self-oligomerization of alpha-synuclein. The dityrosine crosslink formation responsible for the PI-enhanced covalent self-oligomerization was more sensitive to variation of copper concentrations than that of H2O2 during the metal-catalyzed oxidation. The enhancement by PI was shown to be due to facilitation of copper localization to the protein because actual binding affinity between copper and alpha-synuclein increased from Kd of 44.7 microm to 5.9 microm in the presence of the lipid. Taken together, PI not only affects alpha-synuclein to be more self-interactive by providing the lipid surface, but also enhances the metal-catalyzed oxidative protein self-oligomerization by facilitating copper localization to the protein when the metal and H2O2 are provided. This observation therefore could be implicated in the formation of Lewy bodies as lipids and metal-catalyzed oxidative stress have been considered to be a part of pathological causes leading to the neurodegeneration.

Lipid droplet binding and oligomerization properties of the Parkinson's disease protein alpha-synuclein

alpha-Synuclein is a major component of the fibrillary lesion known as Lewy bodies and Lewy neurites that are the pathologic hallmarks of Parkinson's disease (PD). In addition, point mutations in the alpha-synuclein gene imply alpha-synuclein dysfunction in the pathology of inherited forms of PD. alpha-Synuclein is a member of a family of proteins found primarily in the brain and is concentrated within presynaptic terminals. Here, we address the localization and membrane binding characteristics of wild type and PD mutants of alpha-synuclein in cultured cells. In cells treated with high concentrations of fatty acids, wild type alpha-synuclein accumulated on phospholipid monolayers surrounding triglyceride-rich lipid droplets and was able to protect stored triglycerides from hydrolysis. PD mutant synucleins showed variable distributions on lipid droplets and were less effective in regulating triglyceride turnover. Chemical cross-linking demonstrated that synuclein formed small oligomers within cells, primarily dimers and trimers, that preferentially associated with lipid droplets and cell membranes. Our results suggest that the initial phases of synuclein aggregation may occur on the surfaces of membranes and that pathological conditions that induce cross-linking of synuclein may enhance the propensity for subsequent synuclein aggregation.