Alzheimer's Disease (AD) is a devastating neurodegenerative disease that affects millions. AD patients are found to have amyloid deposits of A?42 in extracellular plaques and of tau in neurofibrillary tangles. Unfortunately, amyloids are exceptionally stable and widely believed to be intractable. Moreover, soluble preamyloid oligomers may be more toxic than the fibers themselves. There are currently no therapies that prevent or reverse the formation of amyloid or the dangerous oligomeric species associated with AD, but a promising weapon against these conformers is unexpectedly found in yeast. The protein remodeling factor Hsp104 is able to rapidly disassemble yeast amyloids and remodel oligomers. Surprisingly, despite its seemingly advantageous disaggregation activity, neither Hsp104 nor a clear homolog has been identified in metazoa. The purpose of this study is to evaluate and develop Hsp104 as a tool to combat neurodegeneration associated with amyloidogenesis in AD. This will be investigated by: (1) Establishing whether Hsp104 can disaggregate and remodel aberrant A?42 and tau conformers. Using purified components, fibers or oligomers will be incubated with Hsp104, and disassembly will be assessed using amyloid-binding dyes, sedimentation, electron microscopy, size exclusion chromatography, and oligomer-specific antibodies. Remodeled A?42 and tau species will be tested for ability to 'seed'or nucleate fiber formation, and tau will be evaluated for ability to associate with microtubules to assess possible reactivation following Hsp104 remodeling. (2) Engineering Hsp104 for optimal activity against A?42 and tau. Directed mutations to critical substrate-contacting Hsp104 residues may enhance substrate specificity, as monitored with the techniques above. Also, A?42 disassembly will be coupled to degradation by using a mutant Hsp104 that associates with the bacterial protease ClpP. Hsp104 variants will be assessed for proper assembly and ATPase activity, and ability to disaggregate of non- amyloid substrates. (3) Demonstrating that A?42 and tau products remodeled by Hsp104, or engineered variants, are less toxic. Both A?42 and tau conformers will be evaluated for toxicity by applying to cultured neuroblastoma cells. At a time when age-related neurodegenerative diseases are becoming more prevalent (and are poised to become a substantial social and economic burden), we are in desperate need of a treatment to directly eradicate amyloid and preamyloid oligomer load. Hsp104 could ultimately be employed as a gene therapy treatment for humans with AD to efficiently disassemble amyloid aggregates and neutralize toxic oligomers.
Half of individuals over the age of 85 are afflicted with Alzheimer's disease (AD);with the current increase in life expectancy, the prevalence of age-related neurodegenerative diseases is escalating, resulting in a heavy social and economic burden. There is no effective treatment for the pathological protein accumulations underyling AD, and we are in desperate need of a treatment to directly eradicate amyloid and preamyloid oligomer load. Hsp104 is unique in its ability to disassemble the stable protein interactions occurring during amyloidogenesis, and could ultimately be employed as a gene therapy treatment for humans with AD to efficiently eliminate amyloid aggregates and neutralize toxic oligomers.
|Seither, Katelyn M; McMahon, Heather A; Singh, Nikita et al. (2014) Specific aromatic foldamers potently inhibit spontaneous and seeded A?42 and A?43 fibril assembly. Biochem J 464:85-98|
|Cushman-Nick, Mimi; Bonini, Nancy M; Shorter, James (2013) Hsp104 suppresses polyglutamine-induced degeneration post onset in a drosophila MJD/SCA3 model. PLoS Genet 9:e1003781|
|DeSantis, Morgan E; Leung, Eunice H; Sweeny, Elizabeth A et al. (2012) Operational plasticity enables hsp104 to disaggregate diverse amyloid and nonamyloid clients. Cell 151:778-793|