Open AccessProteins in aggregates functionally impact multiple neurodegenerative disease models by forming proteasome‐blocking complexes
Author(s) -
Ayyadevara Srinivas,
Balasubramaniam Meenakshisundaram,
Gao Yuan,
Yu LiRong,
Alla Ramani,
Shmookler Reis Robert
Publication year - 2015
Publication title -
aging cell
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.103
H-Index - 140
eISSN - 1474-9726
pISSN - 1474-9718
DOI - 10.1111/acel.12296
Subject(s) - gene knockdown , biology , proteasome , protein aggregation , rna interference , microbiology and biotechnology , amyloid (mycology) , protein subunit , caenorhabditis elegans , proteostasis , small interfering rna , biochemistry , rna , genetics , cell culture , botany , gene
Summary 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 RNA i treatments also retarded aggregation/cytotoxicity in Alzheimer's disease models, nematodes with muscle or pan‐neuronal Aβ 1–42 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 Aβ 1–42 , 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.