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Perspective

Reversing deleterious protein aggregation with re-engineered protein disaggregases

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Pages 1379-1383 | Received 19 Mar 2014, Accepted 30 Mar 2014, Published online: 02 Apr 2014

Abstract

Aberrant protein folding is severely problematic and manifests in numerous disorders, including amyotrophic lateral sclerosis (ALS), Parkinson disease (PD), Huntington disease (HD), and Alzheimer disease (AD). Patients with each of these disorders are characterized by the accumulation of mislocalized protein deposits. Treatments for these disorders remain palliative, and no available therapeutics eliminate the underlying toxic conformers. An intriguing approach to reverse deleterious protein misfolding is to upregulate chaperones to restore proteostasis. We recently reported our work to re-engineer a prion disaggregase from yeast, Hsp104, to reverse protein misfolding implicated in human disease. These potentiated Hsp104 variants suppress TDP-43, FUS, and α-synuclein toxicity in yeast, eliminate aggregates, reverse cellular mislocalization, and suppress dopaminergic neurodegeneration in an animal model of PD. Here, we discuss this work and its context, as well as approaches for further developing potentiated Hsp104 variants for application in reversing protein-misfolding disorders.

Proteins must fold properly to function effectively.Citation1 Therefore, protein folding is essential for all life.Citation1 Accordingly, protein misfolding is associated with numerous fatal neurodegenerative disorders, including amyotrophic lateral sclerosis (ALS), Parkinson disease (PD), Huntington disease (HD), and Alzheimer disease (AD).Citation1-Citation3 Each of these disorders is associated with the accumulation of misfolded aggregates of specific proteins.Citation2 In certain patients with ALS, the RNA-binding proteins TDP-43 and FUS form aggregates that accumulate in the cytoplasm, whereas these proteins would normally be predominantly soluble within the nucleus and shuttling to and from the cytoplasm.Citation4-Citation8 In patients with PD, α-synuclein (α-syn) takes on a cross-β amyloid conformation and accumulates in Lewy bodies.Citation9 While amyloid accumulation has long been presumed to be the underlying cause of α-syn toxicity, and, indeed, pure amyloid forms of α-syn suffice to initiate disease de novo,Citation10,Citation11 it has also been suggested that it is not the amyloid fibers, but instead the pre-amyloid oligomers that are the toxic species.Citation1,Citation3 There are no therapies that eliminate any of these misfolded conformers, and available therapeutics remain palliative. It is therefore essential to develop novel strategies to target the underlying cause of these disorders: protein misfolding and aggregation.

Numerous strategies have been explored to reverse protein aggregation and restore proteostasis. One strategy is to enhance the activity of cellular chaperones. For instance, Hsp70 mediates protein folding and serves to proofread and repair proteins.Citation12 Thus, Hsp70 is a plausible candidate for upregulation to enhance protein folding and restore proteostasis. Indeed, upregulation of Hsp70 suppresses polyglutamine-induced neurodegeneration in Drosophila.Citation13,Citation14 Moreover, Hsp70 is a critical component of the protein disaggregase machinery of metazoa, and when combined with Hsp110 and Hsp40 can resolve disordered aggregates and slowly depolymerize amyloid.Citation15-Citation19 Chaperones in the Hsp100 family of proteins possess an even more powerful and rapid disaggregase activity, disassembling proteins from aggregated conformations in collaboration with Hsp110, Hsp70, and Hsp40.Citation16,Citation17,Citation20,Citation21 Using proteins in the Hsp100 family to reverse human disease phenotypes is intriguing, because the ability of Hsp100 proteins to rapidly untangle proteins from pre-existing inclusions would seem to have far greater therapeutic value than solely preventing aggregation.Citation20,Citation22 While Hsp100 proteins are highly conserved in eubacteria and the vast majority of eukaryotes, Hsp104 from the budding yeast Saccharomyces cerevisiae is of particular interest, because it is the only protein known to rapidly disassemble amyloid and toxic preamyloid oligomers, but has no metazoan homolog.Citation20,Citation22-Citation24 S. cerevisiae maintain a complex mechanism of genetic regulation requiring the construction and disassembly of yeast prions, and Hsp104 is critical in mediating these processes.Citation25 Our lab and others have explored applying Hsp104 to human disease models.Citation14,Citation23,Citation24,Citation26,Citation27 In addition to applying native Hsp104, we have also aimed to engineer Hsp104 to have enhanced activity against different substrates implicated in neurodegeneration in an effort to restore proteostasis.Citation26 Recently, we reported the development of potentiated Hsp104 variants that disaggregate TDP-43, FUS, and α-syn.Citation26 The potentiated Hsp104 variants not only suppress toxicity of these substrates in yeast, but they also restore the proper localization of these proteins and mitigate neurodegeneration in a C. elegans model of PD. Here, we further discuss the context of our work, the isolation of these variants, as well as future directions in the development of Hsp104 variants for use in a therapeutic context.

Applying Chaperones to Restore Proteostasis

Overexpression of expanded polyglutamine tracts causes neurodegeneration in Drosophila, providing a useful platform to assess the reversal of polyglutamine-mediated neurodegeneration.Citation13 Using this model, Hsp70 was discovered to suppress aggregation of polyglutamine and degeneration in Drosophila.Citation14,Citation28 Additionally, co-expression of human Hsp110 and Hsp40 suppresses the toxicity and aggregation of polyglutamine in Drosophila.Citation29 We recently expressed Hsp70 or Hsp104 in a Drosophila model of spinocerebellar ataxia.Citation14 Here, Hsp104 suppressed toxicity after the onset of polyglutamine-induced degeneration.Citation14 Importantly, in the same system, while Hsp70 inhibits degeneration, it is unable to reverse degeneration.Citation14 Hsp104 has also been demonstrated to eliminate aggregates of various other substrates implicated in neurodegenerative disease.Citation23,Citation24 Hsp104 disassembles preformed α-syn amyloid fibers as well as its preamyloid oligomeric precursors.Citation23,Citation24 In addition, Hsp104 suppressed α-syn-induced dopaminergic neurodegeneration in the rat substantia nigra.Citation24 Furthermore, we have demonstrated that Hsp104 disassembles preformed aggregates and amyloids comprised of Aβ, tau, polyglutamine, and amylin in vitro.Citation23 However, these activities were modest and required very high levels of Hsp104, which presents a barrier to further developing Hsp104 as a strategy for reversing neurodegeneration. We recently broached this issue with the development of re-engineered Hsp104 variants.Citation26 These potentiated variants are highly active, with disaggregase and ATPase activity far greater than wild-type Hsp104 (Hsp104WT). Additionally, in yeast and C. elegans, these variants suppress toxicity, reverse mislocalization, and suppress dopaminergic neurodegeneration in situations where Hsp104WT is ineffective.Citation26 To isolate these variants, we constructed large libraries of Hsp104 mutants and implemented yeast models of proteotoxicity as a platform to screen these libraries for Hsp104 variants that potently suppress proteotoxicity.

Strategies for Re-Engineering Hsp104

Hsp104 is an AAA+ protein comprised of 5 domains: an N-terminal domain, 2 nucleotide binding domains (NBDs), a middle domain, and C-terminal domain.Citation30 The protein forms a 2-tiered hexamer with a central pore, through which substrate is threaded.Citation30,Citation31 Hsp104 is very large, consisting of 6 102-kDa monomers, and its structure remains poorly understood. Therefore, Hsp104 is a relatively poor candidate for rational design.Citation32 Initially, we hypothesized that the substrate-binding loop regions that line the central channel of Hsp104Citation31 could be optimized against specific substrates. However, we have noted only subtle rescue phenotypes and more typically detrimental effects when mutating these positions.Citation26 Therefore, we instead adopted a broader approach to library construction. We utilized a domain-specific random mutagenesis approach to construct libraries with high diversity in restricted regions of the protein. We selected the middle domain of Hsp104 for randomization, because the middle domain facilitates ATPase activity, communication between NBD1 and NBD2, intrinsic disaggregase activity, and interactions with Hsp70.Citation26,Citation30 Restricting mutations to just the middle domain was key, as limiting the size of the randomized region allowed for greater depth of coverage. Additionally, this strategy allowed for sequencing to be restricted to a length allowing a single sequencing reaction per variant.

Yeast Models of Proteotoxicity

Yeast are an ideal model system for studying protein misfolding, as they grow rapidly, and excellent genetic tools are available to manipulate yeast.Citation33 Additionally, the yeast genome is highly conserved to that of humans. Thus many fundamental cellular processes, including mechanisms for the regulation of proteostasis, are highly conserved between yeast and mammalian cells.Citation33,Citation34 Furthermore, upon overexpression of several different substrates implicated in various neurodegenerative diseases, many phenotypes noted in patients with these disorders are recapitulated in yeast.Citation33,Citation34 For instance when TDP-43 and FUS are overexpressed in yeast, they form cytoplasmic aggregates, while normally the proteins should translocate between the nucleus and cytoplasm.Citation35-Citation37 Similarly, in certain patients with ALS, cytoplasmic aggregates of TDP-43 or FUS are present, and the proteins are thus excluded from entering the nucleus.Citation4 When α-syn is overexpressed in yeast, it also forms cytoplasmic aggregates.Citation38 In PD patients, cytoplasmic aggregates of α-syn are found, while normally the protein should accumulate at the plasma membrane.Citation9 Thus, yeast provide an excellent platform for screening proteins or other agents for toxicity suppressors. Indeed, yeast overexpressing TDP-43 was used to identify Pbp1 as an enhancer of TDP-43 toxicity.Citation39 It was then determined that polyglutamine expansions in the human homolog of Pbp1, ataxin 2, is one of the leading genetic risk factors for ALS.Citation39 Additionally, yeast overexpressing α-syn was used to screen small molecules to identify those that protect cells from α-syn aggregation and toxicity.Citation40 Using these methods, the compound NAB2 was identified to rescue α-syn pathological phenotypes in cortical neurons from iPS cells of PD patients harboring α-syn mutations.Citation40,Citation41 Thus, we envisioned these yeast models to be an ideal platform for screening libraries of Hsp104 variants.

Isolating Potentiated Hsp104 Variants

Using these yeast proteinopathy models, we screened the library of Hsp104 middle domain variants and isolated a series of potentiated variants.Citation26 We identified point mutations in helices 1, 2, and 3 of the middle domain, as well as in the small domain of NBD1.Citation26 At several of these positions, we introduced additional mutations to other amino acids.Citation26 Surprisingly, at each position we tested, we could introduce both conservative and nonconservative mutations to potentiate Hsp104. We selected alanine 503 to mutate to all amino acids, and, astonishingly, we could mutate position 503 to any amino acid, with the exception of proline, to activate Hsp104.Citation26 There are no other examples, to our knowledge, of instances where mutation to any amino acid yields the same gain of therapeutic function phenotype. We hypothesize that loss of amino acid identity at this position and select others likely leads to a structural perturbation that mimics an allosteric activation event.

Hsp104 has likely been tuned through evolution to be highly regulated in recognizing substrates appropriate for disaggregation. Dysregulation of Hsp104 substrate recognition could lead to unfolding of essential proteins and, therefore, toxicity. Thus, it is very surprising that such a diverse array of mutations in disparate regions of the protein can lead to a generic gain of therapeutic function. Therefore, we suggest that Hsp104 has been tuned to be a tightly regulated protein. We propose that the middle domain serves as a capacitor, which is braced to unleash activity. Fine structural changes in the middle domain perturb the structure sufficiently to activate Hsp104, leading to unfolding of nearly any misfolded substrate encountered. This dysregulation is likely the source of the subtle temperature-sensitive phenotype at elevated temperatures (poor growth at 37 °C) noted for some of the variants.Citation26

Testing Hsp104 Variants in Animal Models

While yeast are an ideal model system for screening for potentiated Hsp104 variants and assessing aggregation, they can never fully recapitulate the complex biology of the metazoan nervous system. Thus, it is essential to also assess candidates that reverse protein aggregation in animal models. We tested a subset of the variants in a transgenic C. elegans model of PD. C. elegans are an ideal system for studying neurodegeneration, because they are of invariant lineage, and the dopaminergic neurons can be easily counted by co-expressing a fluorescent marker protein targeted selectively to the neurons. α-Syn can be targeted to the dopaminergic neurons, leading to a time-dependent loss of neuronal activity.Citation26,Citation42,Citation43 We targeted α-syn and Hsp104 to the dopaminergic neurons, and observed for Hsp104A503S and Hsp104Y257F:A503V:Y662F a strong inhibition of dopaminergic neurodegeneration.Citation26 It will next be essential to test these variants in mammalian models, such as the rat substantia nigra model used to establish suppression of α-syn toxicity and neurodegeneration by Hsp104WT.Citation24

Fine-Tuning Potentiated Hsp104 Activity

Potentiated Hsp104 variants are highly promising for reversing protein aggregation disorders. To our knowledge, there are no other molecules known, protein or otherwise, that reverse TDP-43, FUS, and α-syn aggregation. However, the variants that we have developed are nonspecific. That is, most of the potentiated Hsp104 variants suppress the toxicity of TDP-43, FUS, and α-syn. While none of the variants are specific to a single substrate, Hsp104D498V, Hsp104Y507V, and Hsp104D504C strongly rescue α-syn and FUS toxicity, but not TDP-43 toxicity.Citation26 Hsp104D504V behaves similarly, strongly rescuing α-syn and FUS toxicity but only mildly rescuing TDP-43 toxicity.Citation26 Thus, these variants are likely activated against many other substrates that may not necessarily be misfolded. We hypothesize that this non-specific activity is the basis for the temperature-sensitive phenotype (poor growth at 37 °C) we have noted for several variants, which ranged from subtle for Hsp104A503S and Hsp104Y257F:A503V:Y662F to more severe for Hsp104A503V 26. However, the variants do not display a growth defect at 30 °C, so we do not believe this to be a problematic phenotype.Citation26 Nonetheless, to move forward in applying Hsp104 variants to different diseases, it will be essential to fine-tune their substrate specificity. For instance, variants that are selected for disaggregation of TDP-43 but do not suppress α-syn toxicity will likely have greater overall substrate specificity and a diminished temperature-sensitive phenotype.

Using the methods we have developed, it will be challenging to identify variants that disaggregate a single substrate, as this could potentially entail manual screening of many variants. Thus, it will be important to develop new strategies for identifying substrate-specific variants. Additionally, it will be important to implement more directed approaches to variant design to develop substrate-specific variants. For instance, mutating the substrate-binding tyrosine residues that line the pore of Hsp104 in a potentiated background may allow for enhanced substrate specificity.

Outlook

The application of chaperones to reversing neurodegenerative disease is a promising approach for restoring proteostasis. Hsp104 is a particularly promising chaperone for use in this context, as it is uniquely capable of rapidly disassembling amyloid. Alternatively the metazoan Hsp110, Hsp70, and Hsp40 system, which slowly depolymerizes amyloid, could be evolved to enhance its activity.Citation15 Additionally, Hsp104 could likely be potentiated against any protein, which may be valuable for solubilizing proteins that are difficult to purify.

To further develop Hsp104 variants for potential use as therapeutics, it will be essential to further fine-tune their substrate specificity. It is also essential to further test these variants in rodent models. Ultimately, we envision that direct injection or gene therapy could be used to introduce Hsp104 into patients in transient bursts. Regardless of the potential therapeutic applications of potentiated chaperones, our workCitation14,Citation26 and that of othersCitation27,Citation28 has established that using chaperones to divert disease-associated proteins to their nonpathogenic states may be a highly promising strategy for halting and reversing neurodegenerative disease.

Abbreviations:
Hsp=

heat shock protein

ALS=

amyotrophic lateral sclerosis

PD=

Parkinson disease

HD=

Huntington disease

AD=

Alzheimer disease

α-syn=

α-synuclein

NBD=

nucleotide binding domain

AAA+=

ATPases associated with diverse activities

Disclosure of Potential Conflicts of Interest

No potential conflicts of interest were disclosed.

Acknowledgments

Our studies were supported by: an American Heart Association Post-Doctoral Fellowship (M.E.J); NIH Director’s New Innovator Award DP2OD002177, NIH grants R21NS067354, R21HD074510, and R01GM099836, a Muscular Dystrophy Association Research Award (MDA277268), Packard Center for ALS Research at Johns Hopkins University, Target ALS, and an Ellison Medical Foundation New Scholar in Aging Award (J.S.).

References

  • Dobson CM. Protein folding and misfolding. Nature 2003; 426:884 - 90; http://dx.doi.org/10.1038/nature02261; PMID: 14685248
  • Forman MS, Trojanowski JQ, Lee VM. Neurodegenerative diseases: a decade of discoveries paves the way for therapeutic breakthroughs. Nat Med 2004; 10:1055 - 63; http://dx.doi.org/10.1038/nm1113; PMID: 15459709
  • Morimoto RI. Stress, aging, and neurodegenerative disease. N Engl J Med 2006; 355:2254 - 5; http://dx.doi.org/10.1056/NEJMcibr065573; PMID: 17124027
  • Robberecht W, Philips T. The changing scene of amyotrophic lateral sclerosis. Nat Rev Neurosci 2013; 14:248 - 64; http://dx.doi.org/10.1038/nrn3430; PMID: 23463272
  • King OD, Gitler AD, Shorter J. The tip of the iceberg: RNA-binding proteins with prion-like domains in neurodegenerative disease. Brain Res 2012; 1462:61 - 80; http://dx.doi.org/10.1016/j.brainres.2012.01.016; PMID: 22445064
  • Neumann M, Sampathu DM, Kwong LK, Truax AC, Micsenyi MC, Chou TT, Bruce J, Schuck T, Grossman M, Clark CM, et al. Ubiquitinated TDP-43 in frontotemporal lobar degeneration and amyotrophic lateral sclerosis. Science 2006; 314:130 - 3; http://dx.doi.org/10.1126/science.1134108; PMID: 17023659
  • Vance C, Rogelj B, Hortobágyi T, De Vos KJ, Nishimura AL, Sreedharan J, Hu X, Smith B, Ruddy D, Wright P, et al. Mutations in FUS, an RNA processing protein, cause familial amyotrophic lateral sclerosis type 6. Science 2009; 323:1208 - 11; http://dx.doi.org/10.1126/science.1165942; PMID: 19251628
  • Kwiatkowski TJ Jr., Bosco DA, Leclerc AL, Tamrazian E, Vanderburg CR, Russ C, Davis A, Gilchrist J, Kasarskis EJ, Munsat T, et al. Mutations in the FUS/TLS gene on chromosome 16 cause familial amyotrophic lateral sclerosis. Science 2009; 323:1205 - 8; http://dx.doi.org/10.1126/science.1166066; PMID: 19251627
  • Cushman M, Johnson BS, King OD, Gitler AD, Shorter J. Prion-like disorders: blurring the divide between transmissibility and infectivity. J Cell Sci 2010; 123:1191 - 201; http://dx.doi.org/10.1242/jcs.051672; PMID: 20356930
  • Luk KC, Kehm V, Carroll J, Zhang B, O’Brien P, Trojanowski JQ, Lee VM. Pathological α-synuclein transmission initiates Parkinson-like neurodegeneration in nontransgenic mice. Science 2012; 338:949 - 53; http://dx.doi.org/10.1126/science.1227157; PMID: 23161999
  • Guo JL, Covell DJ, Daniels JP, Iba M, Stieber A, Zhang B, Riddle DM, Kwong LK, Xu Y, Trojanowski JQ, et al. Distinct α-synuclein strains differentially promote tau inclusions in neurons. Cell 2013; 154:103 - 17; http://dx.doi.org/10.1016/j.cell.2013.05.057; PMID: 23827677
  • Kim YE, Hipp MS, Bracher A, Hayer-Hartl M, Hartl FU. Molecular chaperone functions in protein folding and proteostasis. Annu Rev Biochem 2013; 82:323 - 55; http://dx.doi.org/10.1146/annurev-biochem-060208-092442; PMID: 23746257
  • Warrick JM, Paulson HL, Gray-Board GL, Bui QT, Fischbeck KH, Pittman RN, Bonini NM. Expanded polyglutamine protein forms nuclear inclusions and causes neural degeneration in Drosophila.. Cell 1998; 93:939 - 49; http://dx.doi.org/10.1016/S0092-8674(00)81200-3; PMID: 9635424
  • Cushman-Nick M, Bonini NM, Shorter J. Hsp104 suppresses polyglutamine-induced degeneration post onset in a drosophila MJD/SCA3 model. PLoS Genet 2013; 9:e1003781; http://dx.doi.org/10.1371/journal.pgen.1003781; PMID: 24039611
  • Torrente MP, Shorter J. The metazoan protein disaggregase and amyloid depolymerase system: Hsp110, Hsp70, Hsp40, and small heat shock proteins. Prion 2014; 7; PMID: 24401655
  • Duennwald ML, Echeverria A, Shorter J. Small heat shock proteins potentiate amyloid dissolution by protein disaggregases from yeast and humans. PLoS Biol 2012; 10:e1001346; http://dx.doi.org/10.1371/journal.pbio.1001346; PMID: 22723742
  • Shorter J. The mammalian disaggregase machinery: Hsp110 synergizes with Hsp70 and Hsp40 to catalyze protein disaggregation and reactivation in a cell-free system. PLoS One 2011; 6:e26319; http://dx.doi.org/10.1371/journal.pone.0026319; PMID: 22022600
  • Rampelt H, Kirstein-Miles J, Nillegoda NB, Chi K, Scholz SR, Morimoto RI, Bukau B. Metazoan Hsp70 machines use Hsp110 to power protein disaggregation. EMBO J 2012; 31:4221 - 35; http://dx.doi.org/10.1038/emboj.2012.264; PMID: 22990239
  • Mattoo RU, Sharma SK, Priya S, Finka A, Goloubinoff P. Hsp110 is a bona fide chaperone using ATP to unfold stable misfolded polypeptides and reciprocally collaborate with Hsp70 to solubilize protein aggregates. J Biol Chem 2013; 288:21399 - 411; http://dx.doi.org/10.1074/jbc.M113.479253; PMID: 23737532
  • Shorter J. Hsp104: a weapon to combat diverse neurodegenerative disorders. Neurosignals 2008; 16:63 - 74; http://dx.doi.org/10.1159/000109760; PMID: 18097161
  • Glover JR, Lindquist S. Hsp104, Hsp70, and Hsp40: a novel chaperone system that rescues previously aggregated proteins. Cell 1998; 94:73 - 82; http://dx.doi.org/10.1016/S0092-8674(00)81223-4; PMID: 9674429
  • Vashist S, Cushman M, Shorter J. Applying Hsp104 to protein-misfolding disorders. Biochem Cell Biol 2010; 88:1 - 13; http://dx.doi.org/10.1139/O09-121; PMID: 20130674
  • DeSantis ME, Leung EH, Sweeny EA, Jackrel ME, Cushman-Nick M, Neuhaus-Follini A, Vashist S, Sochor MA, Knight MN, Shorter J. Operational plasticity enables hsp104 to disaggregate diverse amyloid and nonamyloid clients. Cell 2012; 151:778 - 93; http://dx.doi.org/10.1016/j.cell.2012.09.038; PMID: 23141537
  • Lo Bianco C, Shorter J, Régulier E, Lashuel H, Iwatsubo T, Lindquist S, Aebischer P. Hsp104 antagonizes alpha-synuclein aggregation and reduces dopaminergic degeneration in a rat model of Parkinson disease. J Clin Invest 2008; 118:3087 - 97; http://dx.doi.org/10.1172/JCI35781; PMID: 18704197
  • Sweeny EA, Shorter J. Prion proteostasis: Hsp104 meets its supporting cast. Prion 2008; 2:135 - 40; http://dx.doi.org/10.4161/pri.2.4.7952; PMID: 19242125
  • Jackrel ME, DeSantis ME, Martinez BA, Castellano LM, Stewart RM, Caldwell KA, Caldwell GA, Shorter J. Potentiated Hsp104 variants antagonize diverse proteotoxic misfolding events. Cell 2014; 156:170 - 82; http://dx.doi.org/10.1016/j.cell.2013.11.047; PMID: 24439375
  • Vacher C, Garcia-Oroz L, Rubinsztein DC. Overexpression of yeast hsp104 reduces polyglutamine aggregation and prolongs survival of a transgenic mouse model of Huntington’s disease. Hum Mol Genet 2005; 14:3425 - 33; http://dx.doi.org/10.1093/hmg/ddi372; PMID: 16204350
  • Warrick JM, Chan HYE, Gray-Board GL, Chai Y, Paulson HL, Bonini NM. Suppression of polyglutamine-mediated neurodegeneration in Drosophila by the molecular chaperone HSP70. Nat Genet 1999; 23:425 - 8; http://dx.doi.org/10.1038/70532; PMID: 10581028
  • Kuo Y, Ren S, Lao U, Edgar BA, Wang T. Suppression of polyglutamine protein toxicity by co-expression of a heat-shock protein 40 and a heat-shock protein 110. Cell Death Dis 2013; 4:e833; http://dx.doi.org/10.1038/cddis.2013.351; PMID: 24091676
  • DeSantis ME, Shorter J. The elusive middle domain of Hsp104 and ClpB: location and function. Biochim Biophys Acta 2012; 1823:29 - 39; http://dx.doi.org/10.1016/j.bbamcr.2011.07.014; PMID: 21843558
  • Tessarz P, Mogk A, Bukau B. Substrate threading through the central pore of the Hsp104 chaperone as a common mechanism for protein disaggregation and prion propagation. Mol Microbiol 2008; 68:87 - 97; http://dx.doi.org/10.1111/j.1365-2958.2008.06135.x; PMID: 18312264
  • Saibil H. Chaperone machines for protein folding, unfolding and disaggregation. Nat Rev Mol Cell Biol 2013; 14:630 - 42; http://dx.doi.org/10.1038/nrm3658; PMID: 24026055
  • Gitler AD. Beer and bread to brains and beyond: can yeast cells teach us about neurodegenerative disease?. Neurosignals 2008; 16:52 - 62; http://dx.doi.org/10.1159/000109759; PMID: 18097160
  • Khurana V, Lindquist S. Modelling neurodegeneration in Saccharomyces cerevisiae: why cook with baker’s yeast?. Nat Rev Neurosci 2010; 11:436 - 49; http://dx.doi.org/10.1038/nrn2809; PMID: 20424620
  • Johnson BS, McCaffery JM, Lindquist S, Gitler AD. A yeast TDP-43 proteinopathy model: Exploring the molecular determinants of TDP-43 aggregation and cellular toxicity. Proc Natl Acad Sci U S A 2008; 105:6439 - 44; http://dx.doi.org/10.1073/pnas.0802082105; PMID: 18434538
  • Sun Z, Diaz Z, Fang X, Hart MP, Chesi A, Shorter J, Gitler AD. Molecular determinants and genetic modifiers of aggregation and toxicity for the ALS disease protein FUS/TLS. PLoS Biol 2011; 9:e1000614; http://dx.doi.org/10.1371/journal.pbio.1000614; PMID: 21541367
  • Ju S, Tardiff DF, Han H, Divya K, Zhong Q, Maquat LE, Bosco DA, Hayward LJ, Brown RH Jr., Lindquist S, et al. A yeast model of FUS/TLS-dependent cytotoxicity. PLoS Biol 2011; 9:e1001052; http://dx.doi.org/10.1371/journal.pbio.1001052; PMID: 21541368
  • Outeiro TF, Lindquist S. Yeast cells provide insight into alpha-synuclein biology and pathobiology. Science 2003; 302:1772 - 5; http://dx.doi.org/10.1126/science.1090439; PMID: 14657500
  • Elden AC, Kim H-J, Hart MP, Chen-Plotkin AS, Johnson BS, Fang X, Armakola M, Geser F, Greene R, Lu MM, et al. Ataxin-2 intermediate-length polyglutamine expansions are associated with increased risk for ALS. Nature 2010; 466:1069 - 75; http://dx.doi.org/10.1038/nature09320; PMID: 20740007
  • Tardiff DF, Jui NT, Khurana V, Tambe MA, Thompson ML, Chung CY, Kamadurai HB, Kim HT, Lancaster AK, Caldwell KA, et al. Yeast reveal a “druggable” Rsp5/Nedd4 network that ameliorates α-synuclein toxicity in neurons. Science 2013; 342:979 - 83; http://dx.doi.org/10.1126/science.1245321; PMID: 24158909
  • Chung CY, Khurana V, Auluck PK, Tardiff DF, Mazzulli JR, Soldner F, Baru V, Lou Y, Freyzon Y, Cho S, et al. Identification and rescue of α-synuclein toxicity in Parkinson patient-derived neurons. Science 2013; 342:983 - 7; http://dx.doi.org/10.1126/science.1245296; PMID: 24158904
  • Berkowitz LA, Hamamichi S, Knight AL, Harrington AJ, Caldwell GA, Caldwell KA. Application of a C. elegans dopamine neuron degeneration assay for the validation of potential Parkinson’s disease genes. J Vis Exp 2008; e835; PMID: 19066512
  • Cooper AA, Gitler AD, Cashikar A, Haynes CM, Hill KJ, Bhullar B, Liu K, Xu K, Strathearn KE, Liu F, et al. α-synuclein blocks ER-Golgi traffic and Rab1 rescues neuron loss in Parkinson’s models. Science 2006; 313:324 - 8; http://dx.doi.org/10.1126/science.1129462; PMID: 16794039

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