Cytoplasmic Dynein Is Required for the Spatial Organization of Protein Aggregates in Filamentous Fungi

• Aspergillus nidulans protein aggregates coalesce into discrete structures
• Microtubules facilitate the formation of Hsp104-positive inclusions
• Cytoplasmic dynein promotes aggregate clearance through their coalescence
• Impaired aggregate clearance impedes trafficking of conventional dynein cargo

SummaryEukaryotes have evolved multiple strategies for maintaining cellular protein homeostasis. One such mechanism involves neutralization of deleterious protein aggregates via their defined spatial segregation. Here, using the molecular disaggregase Hsp104 as a marker for protein aggregation, we describe the spatial and temporal dynamics of protein aggregates in the filamentous fungus Aspergillus nidulans. Filamentous fungi, such as A. nidulans, are a diverse group of species of major health and economic importance and also serve as model systems for studying highly polarized eukaryotic cells. We find that microtubules promote the formation of Hsp104-positive aggregates, which coalesce into discrete subcellular structures in a process dependent on the microtubule-based motor cytoplasmic dynein. Finally, we find that impaired clearance of these inclusions negatively impacts retrograde trafficking of endosomes, a conventional dynein cargo, indicating that microtubule-based transport can be overwhelmed by chronic cellular stress.

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