The chaperonin TRiC is blocked by native and glycated prion protein

Contribution of Extracellular Vesicles and Molecular Chaperones in Age-Related Neurodegenerative Disorders of the CNS

Many neurodegenerative disorders are characterized by the abnormal aggregation of misfolded proteins that form amyloid deposits which possess prion-like behavior such as self-replication, intercellular transmission, and consequent induction of native forms of the same protein in surrounding cells. The distribution of the accumulated proteins and their correlated toxicity seem to be involved in the progression of nervous system degeneration. Molecular chaperones are known to maintain proteostasis, contribute to protein refolding to protect their function, and eliminate fatally misfolded proteins, prohibiting harmful effects. However, chaperone network efficiency declines during aging, prompting the onset and the development of neurological disorders. Extracellular vesicles (EVs) are tiny membranous structures produced by a wide range of cells under physiological and pathological conditions, suggesting their significant role in fundamental processes particularly in cellular communication. They modulate the behavior of nearby and distant cells through their biological cargo. In the pathological context, EVs transport disease-causing entities, including prions, α-syn, and tau, helping to spread damage to non-affected areas and accelerating the progression of neurodegeneration. However, EVs are considered effective for delivering therapeutic factors to the nervous system, since they are capable of crossing the blood-brain barrier (BBB) and are involved in the transportation of a variety of cellular entities. Here, we review the neurodegeneration process caused mainly by the inefficiency of chaperone systems as well as EV performance in neuropathies, their potential as diagnostic biomarkers and a promising EV-based therapeutic approach.

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.

Functional genomics screen identifies proteostasis targets that modulate prion protein (PrP) stability

Prion protein (PrP) adopts either a helical conformation (PrPC) or an alternative, beta sheet-rich, misfolded conformation (PrPSc). The PrPSc form has the ability to "infect" PrPC and force it into the misfolded state. Accumulation of PrPSc is associated with a number of lethal neurodegenerative disorders, including Creutzfeldt-Jacob disease (CJD). Knockout of PrPC protects cells and animals from PrPSc infection; thus, there is interest in identifying factors that regulate PrPC stability, with the therapeutic goal of reducing PrPC levels and limiting infection by PrPSc. Here, we assembled a short-hairpin RNA (shRNA) library composed of 25+ shRNA sequences for each of 133 protein homeostasis (aka proteostasis) factors, such as molecular chaperones and co-chaperones. This Proteostasis shRNA Library was used to identify regulators of PrPC stability in HEK293 Hu129M cells. Strikingly, the screen identified a number of Hsp70 family members and their co-chaperones as putative targets. Indeed, a chemical pan-inhibitor of Hsp70s reduced PrPC levels and limited conversion to PrPSc in N2a cells. These results implicate specific proteostasis sub-networks, especially the Hsp70 system, as potential new targets for the treatment of CJD. More broadly, the Proteostasis shRNA Library might be a useful tool for asking which proteostasis factors are important for a given protein.