Effect of bacteriophage-encoded chaperonins on amyloid transformation of α-synuclein.

Controversial information about the role of chaperonins in the amyloid transformation of proteins and, in particular, α-synuclein, requires a more detailed study of the observed effects due to the structure and functional state of various chaperonins. In this work, two types of phage chaperonins, the double-ring EL and the single-ring OBP, were shown to stimulate α-synuclein fibrillation in an ATP-dependent manner. Chaperonin morphology does not affect the stimulation of α-synuclein amyloid transformation. However, the ATP-dependent effect of single- and double-ring chaperonins on this process differs, which can lead to different morphology of resulting fibrils. Fibril formation seems to proceed without substrate encapsulation in the internal cavity of chaperonin, because of the structural features of phage chaperonins and their ability to function without co-chaperonins. In the absence of ATP, both chaperonins, on the contrary, completely prevent α-synuclein amyloid transformation, which provides the possibility of their use as anti-amyloid agents, in the form of incomplete molecules or mutants with suppressed ATPase activity.

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

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

Glycation of glyceraldehyde-3-phosphate dehydrogenase inhibits the binding with α-synuclein and RNA.

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) shows great diversity of functions, interaction partners and post-translational modifications. GAPDH undergoes glycation of positively charged residues in diabetic patient's tissues and therefore may change interaction with partners. The influence of GAPDH glycation on interaction with two important partners, α-synuclein and RNA, has been investigated in silico using molecular dynamics simulations and in vitro using surface plasmon resonance measurements. Since positively charged groove including substrate- and NAD+-binding sites is proposed as potential binding site for α-synuclein and RNA, GAPDH was glycated on residues in grooves and randomly distributed over the whole surface. Lysine residues were replaced with negatively charged carboxymethyl lysine as a widespread advanced glycation end product. As results, GAPDH glycation suppressed the interaction with α-synuclein and RNA. Although the modified GAPDH residues participated in binding with α-synuclein, no stable binding site with both glycated forms was observed. Glycation along the whole GAPDH surface completely suppressed interaction with RNA, whereas the alternative possible RNA binding site was identified in case of groove glycation. The findings were supported by direct measurement of the binding affinity. The obtained results clarify effect of glycation on GAPDH interaction with α-synuclein and RNA and elucidate a possible mechanism of interplay between glycation occurred in diabetes and neurodegenerative diseases, which GAPDH and α-synuclein are involved in.

Glyceraldehyde-3-phosphate dehydrogenase: Aggregation mechanisms and impact on amyloid neurodegenerative diseases.

The review analyses data on specific features of aggregation of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and possible role of this enzyme in the development of neurodegenerative diseases. Different post-translational modifications of the enzyme are considered: oxidation, nitrosylation, and S-glutathionylation of the active site sulfhydryl groups, as well as phosphorylation, glycation and homocysteinylation of other amino acid residues. Modification of the sulfhydryl groups of the enzyme inhibits the enzymatic activity of GAPDH, resulting in slowdown of glycolysis, and may lead to the dissociation of the cofactor NAD from the active site of the enzyme. The resulting apo-GAPDH (without NAD) is less stable and prone to dissociation, denaturation, and subsequent aggregation. These processes could play a crucial role in the translocation of GAPDH subunits from the cytoplasm into the nucleus, which is linked to the induction of apoptosis. Phosphorylation and glycation of GAPDH are presumably involved in the regulation of protein-protein interactions and intracellular localization of the enzyme. Besides, glycation by dicarbonyl compounds and aldehydes may directly inhibit glycolysis. Homocysteinylation of GAPDH may stabilize aggregates of the enzyme by additional disulfide bonding. All types of post-translational modifications affect aggregation of GAPDH. A special attention is given to the role of chaperones in the amyloidogenic transformation of proteins and to confirmation of the hypothesis on blocking of the chaperones by misfolded protein forms. The denatured GAPDH forms were shown to interact directly with amyloidogenic proteins (alpha-synuclein and amyloid-beta peptide) and to play a crucial role in blocking of chaperone system.