α-synuclein mediated proteasome dynamics in yeast and human cells

• Applicant: Professor Dr. Gerhard H. Braus
• Subject Area: Cell Biology
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 567764271

Protein homeostasis is essential for preserving normal cellular metabolism. It safeguards the integrity of the proteome through accurate biosynthesis, folding, trafficking, and degradation of proteins. The efficiency of these processes diminishes in aging cells, leading to aggregation of aberrant protein structures linked to neurodegenerative diseases such as Parkinson’s disease (PD). PD is characterized by the aggregation of alpha-synuclein (αSyn) into protein inclusions. Accumulation of the protein is accompanied by highly elevated phosphorylation at S129. This posttranslational modification plays a central role in pathogenicity and αSyn turnover. The aggregation and propagation of αSyn disrupts cellular proteostasis, contributing to cellular dysfunction and neuronal death. Expression of αSyn in the budding yeast Saccharomyces cerevisiae leads to toxicity, recognized as significant growth reduction and inclusion formation similar to neurons and early cell death. αSyn expression significantly alters the yeast proteome and disturbs 26S proteasome assembly and activity. This proposal aims to investigate molecular mechanisms governing the impact of αSyn on proteasome dynamics. The focus is on the interplay with the proteasomal activator Blm10/PA200. The conserved Blm10/PA200 family of proteins represent key regulators of proteasome assembly and activity. We recently identified Blm10 in a genome-wide yeast screen for proteins with altered stability. Expression of αSyn increased Blm10 stability, depending on the phosphorylation state of αSyn at S129. Increased amounts of Blm10 are protective for cells, which supports a potential compensatory mechanism to counteract proteasome dysfunction. The primary objectives of this research are twofold: (i) to elucidate how αSyn expression affects proteasome assembly and activities, with a particular focus on the role of Blm10 in yeast cells and its counterpart PA200 in human cells, as well as the contribution of S129 phosphorylation to this process; and (ii) to explore the impact of αSyn on 26S proteasome homeostasis including proteasome sorting into the protective proteasome storage granules, and 26S proteasome degradation by proteaphagy under various stress conditions. A combination of in vivo and in vitro techniques will be employed. This study aims to provide a comprehensive understanding of the mutual relationship between αSyn and the 26S proteasome and the role of key components of the proteostasis network at the molecular level.

• DFG Programme: Research Grants