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The pathogenesis of the various prion diseases is based on the conformational conversion of the prion protein from its physiological cellular form to the insoluble scrapie isoform. Several chaperones, including the Hsp60 family of group I chaperonins, are known to contribute to this transformation, but data on their effects are scarce and conflicting. In this work, two GroEL-like phage chaperonins, the single-ring OBP and the double-ring EL, were found to stimulate monomeric prion protein fibrillation in an ATP-dependent manner. The resulting fibrils were characterised by thioflavin T fluorescence, electron microscopy, proteinase K digestion assay and other methods. In the presence of ATP, chaperonins were found to promote the conversion of prion protein monomers into short amyloid fibrils with their further aggregation into less toxic large clusters. Fibrils generated with the assistance of phage chaperonins differ in morphology and properties from those formed spontaneously from monomeric prion in the presence of denaturants at acidic pH., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

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.

Disruption of amyloid protein aggregates is one of the potential therapies for treatment of neurodegenerative disorders such as prion diseases. Here, for the first time we report that pH-independent cationic pyridylphenylene dendrimers are able to disrupt amyloid protein aggregates at physiological pH as exemplified by inclusion bodies of ovine prion protein. The results show that exposure of inclusion bodies to the dendrimers leads to its partial disaggregation and release of the nanosize protein-dendrimer complexes. The complexes were characterized by SDS PAGE, DLS, and Western blotting methods. Thioflavin T fluorescence clearly demonstrated a decrease of amyloidogenic capability of the prion protein upon exposure to the dendrimers. The complexes formed are stable and do not show further aggregation., (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Modification of protein lysyl residues by homocysteine (Hcy)-thiolactone generates proteins with altered structures and functions. It has been supposed to be one of the factors inducing protein condensation pathologies. To test a hypothesis that N-homocysteinylation may induce structural changes and in particular amyloidogenic conversion, ovine prion protein (PrP) was modified with Hcy-thiolactone and its physico-chemical properties were studied. N-Hcy-PrP formed insoluble multimers. Mass spectrometry analyses showed that at least K197 and K207 residues of PrP were the sites of N-homocysteinylation. Dynamic light scattering measurements revealed large aggregated N-Hcy-PrP particles of 1μm diameter. They were resistant to proteinase K digestion, and enhanced thioflavin T (ThT)-binding fluorescence, what is characteristic of amyloid structures. Infrared spectroscopy measurements showed increased content of beta-sheet in N-Hcy-PrP compared to unmodified PrP. Epifluorescence microscopy in the presence of ThT revealed cluster-like aggregates of N-Hcy-PrP. The collected data indicate that the N-homocysteinylation causes amyloidogenic transformation of PrP in vitro., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Molecular chaperones have been shown to be involved in the processes taking place during the pathogenesis of various amyloid neurodegenerative diseases. However, contradictory literature reports suggest that different molecular chaperones can either stimulate or prevent the formation of amyloid structures from distinct amyloidogenic proteins. In the present work, we concentrated on the effects caused by two molecular chaperonins, ovine TRiC and bacterial GroEL, on the aggregation and conformational state of ovine PrP. Both chaperonins were shown to bind native PrP and to produce amyloid-like forms of ovine PrP enriched with beta-structures but, while GroEL acted in an ATP-dependent manner, TRiC was shown to cause the same effect only in the absence of Mg-ATP (i.e. in the inactive form). In the presence of chaperonin GroEL, ovine PrP was shown to form micellar particles, approximately 100-200nm in diameter, which were observed both by dynamic light scattering assay and by electron microscopy. The content of these particles was significantly higher in the presence of Mg-ATP and, only under these conditions, GroEL produced amyloid-like species enriched with beta-structures. TRiC was shown to induce the formation of amyloid fibrils observed by electron microscopy, but only in the absence of Mg-ATP. This study suggests the important role of the cytosolic chaperonin TRiC in the propagation of amyloid structures in vivo during the development of amyloid diseases and the possible role of the bacterial chaperonin GroEL, located in the intestinal microflora, in the induction of these diseases., (Copyright © 2011 Elsevier B.V. All rights reserved.)

This review discusses a few examples of specific mechanisms mediating the contribution of the GIT microbiota to the development of amyloid neurodegenerative diseases caused by the pathologic transformation of prion protein, or alpha-synuclein. The effect of the bacterial GroE chaperonin system and phage chaperonins (single-ring OBP and double-ring EL) on prion protein transformation has been described. A number of studies have shown that chaperonins stimulate the formation of cytotoxic amyloid forms of prion protein in an ATP-dependent manner. Moreover, it was found that E. coli cell lysates have a similar effect on prion protein, and the efficiency of amyloid transformation correlates with the content of GroE in cells. Data on the influence of some metabolites synthesized by gut microorganisms on the onset of synucleinopathies, such as Parkinson's disease, is provided. In particular, the induction of amyloid transformation of alpha-synuclein from intestinal epithelial cells with subsequent prion-like formation of its pathologic forms in nervous tissues featuring microbiota metabolites is described. Possible mechanisms of microbiota influence on the occurrence and development of amyloid neurodegenerative diseases are considered. [ABSTRACT FROM AUTHOR]

• The pyridylphenylene dendrimers inhibit the formation of PrP oligomers and fibrils. • Dendrimer binding prevents the PrP structural conversion and further fibrillation. • The structural features of the dendrimers are important for anti-amyloid behavior. • The permanent charge & hydrophobic groups enable antiprion activity at any conditions. Misfolding and aggregation of amyloidogenic proteins are responsible for the onset of neurodegenerative diseases. This makes studies directed towards prevention of these processes of particular importance. In this paper we report that cationic pyridylphenylene dendrimers of the second (G2), third (G3) and fourth (G4) generations act as effective suppressors of the amyloid aggregation of the full-length ovine prion protein (PrP). The dendrimers are able to inhibit both the formation of the most toxic soluble oligomers and amyloid fibrils. Dendrimer binding prevents the structural conversion of PrP and further protein fibrillation. The effect is dependent on the dendrimer generation with G4 being the most potent. Importantly, after the treatment with the dendrimers, PrP does not induce the pathological conformational changes in native PrP, indicating the loss of amyloidogenic properties. The cell viability assay reveals the dependence on the cell line and the dendrimer generation used. The observed fundamental principles of the dendrimer interaction with PrP helped us to elucidate the protective effect of the dendrimers and to suggest the potential mechanism of the dendrimer action. Noteworthy, the dendrimers preserve their protective effect regardless of the aggregation conditions applied, indicating the important role of their structural features, e.g. rigidity and permanent charge, in anti-amyloid behavior. [ABSTRACT FROM AUTHOR]

Eight cinnamic acid derivatives were studied as prion inhibitors in vitro and their cytotoxicity was evaluated. Ferulic (3-methoxy-4-hydroxycinnamic) acid, 3,4,5-trimethoxycin- namic acid and methyl 3-ethoxy-4-acetamidoxycinnamate were found to inhibit amyloid fibril formation, seeding, and spontaneous aggregation of recombinant ovine prion protein. None of the compounds demonstrated cytotoxicity on human neuroblastoma SH-SY5Y cells. [ABSTRACT FROM AUTHOR]