Age-dependent neurodegenerative diseases progressively form aggregates containing both shared components (e.g.， TDP-43， phosphorylated tau) and proteins specific to each disease. We investigated whether diverse neuropathies might have additional aggregation-prone proteins in common， discoverable by proteomics. Caenorhabditis elegans expressing unc-54p/Q40::YFP， a model of polyglutamine array diseases such as Huntington's， accrues aggregates in muscle 2-6 days posthatch. These foci， isolated on antibody-coupled magnetic beads， were characterized by high-resolution mass spectrometry. Three Q40::YFP-associated proteins were inferred to promote aggregation and cytotoxicity， traits reduced or delayed... More
Age-dependent neurodegenerative diseases progressively form aggregates containing both shared components (e.g.， TDP-43， phosphorylated tau) and proteins specific to each disease. We investigated whether diverse neuropathies might have additional aggregation-prone proteins in common， discoverable by proteomics. Caenorhabditis elegans expressing unc-54p/Q40::YFP， a model of polyglutamine array diseases such as Huntington's， accrues aggregates in muscle 2-6 days posthatch. These foci， isolated on antibody-coupled magnetic beads， were characterized by high-resolution mass spectrometry. Three Q40::YFP-associated proteins were inferred to promote aggregation and cytotoxicity， traits reduced or delayed by their RNA interference knockdown. These RNAi treatments also retarded aggregation/cytotoxicity in Alzheimer's disease models， nematodes with muscle or pan-neuronal Aβ₁₋₄₂ expression and behavioral phenotypes. The most abundant aggregated proteins are glutamine/asparagine-rich， favoring hydrophobic interactions with other random-coil domains. A particularly potent modulator of aggregation， CRAM-1/HYPK， contributed < 1% of protein aggregate peptides， yet its knockdown reduced Q40::YFP aggregates 72-86% (P < 10(-6) ). In worms expressing Aβ₁₋₄₂， knockdown of cram-1 reduced β-amyloid 60% (P < 0.002) and slowed age-dependent paralysis > 30% (P < 10(-6)). In wild-type worms， cram-1 knockdown reduced aggregation and extended lifespan， but impaired early reproduction. Protection against seeded aggregates requires proteasome function， implying that normal CRAM-1 levels promote aggregation by interfering with proteasomal degradation of misfolded proteins. Molecular dynamic modeling predicts spontaneous and stable interactions of CRAM-1 (or human orthologs) with ubiquitin， and we verified that CRAM-1 reduces degradation of a tagged-ubiquitin reporter. We propose that CRAM-1 exemplifies a class of primitive chaperones that are initially protective and highly beneficial for early reproduction， but ultimately impair aggregate clearance and limit longevity.
