RuvbL1 and RuvbL2 enhance aggresome formation and disaggregate amyloid fibrils

The aggresome is an organelle that recruits aggregated proteins for storage and degradation. We performed an siRNA screen for proteins involved in aggresome formation and identified novel mammalian AAA+ protein disaggregases RuvbL1 and RuvbL2. Depletion of RuvbL1 or RuvbL2 suppressed aggresome formation and caused buildup of multiple cytoplasmic aggregates. Similarly, downregulation of RuvbL orthologs in yeast suppressed the formation of an aggresome-like body and enhanced the aggregate toxicity. In contrast, their overproduction enhanced the resistance to proteotoxic stress independently of chaperone Hsp104. Mammalian RuvbL associated with the aggresome, and the aggresome substrate synphilin-1 interacted directly with the RuvbL1 barrel-like structure near the opening of the central channel. Importantly, polypeptides with unfolded structures and amyloid fibrils stimulated the ATPase activity of RuvbL. Finally, disassembly of protein aggregates was promoted by RuvbL. These data indicate that RuvbL complexes serve as chaperones in protein disaggregation. Synopsis The AAA+ ATPase RuvbL is required for aggresome formation and serves as a protein disaggregase that can disassemble amyloids in mammalian and yeast cells. Depletion of AAA+ ATPases RuvbL1 or RuvbL2 enhances aggregation of certain proteins in mammalian cells and inhibits aggresome formation. RuvbL directly interacts with aggresome substrates, and the site of interaction is in the proximity to the internal channel of its barrel-like structure. Purified RuvbL inhibits seeding and promotes fragmentation of amyloid fibrils. RuvbL depletion slows down disassembly of protein aggregates in mammalian cells and enhances proteotoxicity. In yeast, RuvbL orthologs protect from heat shock and protein toxicity independently of Hsp104. The AAA+ ATPase RuvbL is required for aggresome formation and serves as a protein disaggregase that can disassemble amyloids in mammalian and yeast cells.