CCT complex restricts neuropathogenic protein aggregation via autophagy

Area of Science:

• Cellular Biology
• Neuroscience
• Protein Homeostasis (Proteostasis)

Background:

• Aberrant protein aggregation is implicated in neurodegenerative diseases.
• Chaperones, such as chaperonin containing TCP-1 (CCT)/TCP-1/TRiC, regulate protein folding and prevent aggregation.
• Mutations in CCT subunits (CCT4/5) are linked to neuropathy, and reduced CCT5 expression is observed in Alzheimer's disease.

Purpose of the Study:

• To investigate the role of CCT integrity in cellular proteostasis, specifically its impact on autophagy and protein aggregation.
• To determine the relationship between CCT function, autophagy, and the aggregation of disease-relevant proteins.

Main Methods:

• Utilized cell culture and Drosophila models to assess CCT function.
• Manipulated CCT subunit expression to induce autophagic flux reduction.
• Analyzed the aggregation of disease-associated proteins (mutant huntingtin, ATXN3, p62) under varying CCT and autophagy conditions.
• Investigated the role of the actin cytoskeleton in CCT-mediated autophagosome degradation.

Main Results:

• CCT integrity is essential for efficient autophagosome degradation, orchestrated by the actin cytoskeleton.
• Reduced CCT function leads to the accumulation and aggregation of autophagy substrates, including disease-relevant proteins.
• Protein aggregation observed upon CCT depletion is primarily a consequence of inhibited autophagy, not a direct loss of CCT's anti-aggregation activity.

Conclusions:

• CCT complex and autophagy are functionally intertwined components of the proteostasis network.
• Defects in autophagy, resulting from compromised CCT activity, contribute to the pathogenesis of diseases associated with protein aggregation.
• Highlights a novel link between CCT function, autophagy, and neurodegenerative disease mechanisms.