Slow Amyloid Nucleation via α-Helix-Rich Oligomeric Intermediates in Short Polyglutamine-Containing Huntingtin Fragments

Jayaraman, Murali; Kodali, Ravindra; Sahoo, Bankanidhi; Thakur, Ashwani Kumar; Mayasundari, Anand; Mishra, Rakesh; Peterson, Cynthia B.; Wetzel, Ronald

doi:10.1016/j.jmb.2011.12.010

Cited by 176 publications

(433 citation statements)

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“…Because the suppressors greatly increased the total accumulation of Htt103Q, our PrD suppressors must prevent the formation of oligomers and/or promote their sequestration. PolyQ-expanded Htt exon-1, in vitro, forms an α-helical oligomer early in the aggregation process (40). It is possible that the suppressor PrDs intercalate into such α-helix-rich oligomers and promote their assembly into the large coaggregated foci.…”

Section: Discussionmentioning

confidence: 99%

Prion-like proteins sequester and suppress the toxicity of huntingtin exon 1

Kayatekin

Matlack

Hesse

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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Expansions of preexisting polyglutamine (polyQ) tracts in at least nine different proteins cause devastating neurodegenerative diseases. There are many unique features to these pathologies, but there must also be unifying mechanisms underlying polyQ toxicity. Using a polyQ-expanded fragment of huntingtin exon-1 (Htt103Q), the causal protein in Huntington disease, we and others have created tractable models for investigating polyQ toxicity in yeast cells. These models recapitulate key pathological features of human diseases and provide access to an unrivalled genetic toolbox. To identify toxicity modifiers, we performed an unbiased overexpression screen of virtually every protein encoded by the yeast genome. Surprisingly, there was no overlap between our modifiers and those from a conceptually identical screen reported recently, a discrepancy we attribute to an artifact of their overexpression plasmid. The suppressors of Htt103Q toxicity recovered in our screen were strongly enriched for glutamine-and asparagine-rich prion-like proteins. Separated from the rest of the protein, the prion-like sequences of these proteins were themselves potent suppressors of polyQ-expanded huntingtin exon-1 toxicity, in both yeast and human cells. Replacing the glutamines in these sequences with asparagines abolished suppression and converted them to enhancers of toxicity. Replacing asparagines with glutamines created stronger suppressors. The suppressors (but not the enhancers) coaggregated with Htt103Q, forming large foci at the insoluble protein deposit in which proteins were highly immobile. Cells possessing foci had fewer (if any) small diffusible oligomers of Htt103Q. Until such foci were lost, cells were protected from death. We discuss the therapeutic implications of these findings.protein misfolding | prions P rotein misfolding and aggregation underlie many neurodegenerative diseases. The causes of protein misfolding are numerous and include single amino acid changes and expansions of amino acid repeats. Polyglutamine (polyQ) expansions are an infamous example of the latter and are responsible for at least nine neurodegenerative conditions, including Huntington disease (HD). In most of these diseases the polyQ-expanded protein is expressed throughout the body, but tissue damage is restricted to the nervous system and, often, to a subset of cells depending on the causal protein. Thus, there are important cell type-specific determinants of toxicity, and these are specific to particular proteins. Despite these differences, disease severity is tightly linked to the number of glutamines. Progressively earlier onset occurs as the number of glutamines increases beyond a critical threshold of ∼35-45 residues (1). Moreover, in all cases, pathology is associated with misfolded forms of the polyQ-expanded protein.Thus, common features that arise from the expansions and result from shared aspects of polyQ-driven protein misfolding must contribute to pathology. Given the diverse nature of both the proteins bearing the polyQ tract and t...

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Section: Discussionmentioning

confidence: 99%

Prion-like proteins sequester and suppress the toxicity of huntingtin exon 1

Kayatekin

Matlack

Hesse

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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“…40,41 CD spectra and molecular dynamics simulations 42 suggest that the N-terminal sequence by itself has a tendency to take on some α-helical secondary structure, while expanded polyQ was shown to aquire a β-sheet conformation. 43 Formation of amyloid-like fibrils with β-sheet structure is observed with many protein sequences and is linked to many neurodegenerative conditions, including Parkinson, Huntington and Alzheimer diseases.…”

Section: Discussionmentioning

confidence: 99%

Huntingtin protein interactions altered by polyglutamine expansion as determined by quantitative proteomic analysis

et al. 2012

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“…The NT17 tract has been shown to be critical for the formation of α-helix-rich oligomeric intermediates by Jayaraman et al (14). We, therefore, first construct the aggregation free energy profile for six NT17-Q20 monomers in a simulation box at the nominal laboratory concentration of the study by Wetzel (19).…”

Section: N-terminal Region Facilitates the Aggregation Of Nt 17 -Q 20mentioning

confidence: 99%

“…Structural characterization of the aggregates (13,14,(18)(19)(20) has shown that, even when there are flanking sequences, polyQ remains the fiber core and adopts a β-hairpin conformation. In this paper, we use energy landscape analysis to provide a detailed molecular picture of the aggregation process of the peptide encoded by HTT exon 1, focusing on how the flanking sequences influence aggregation.…”

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confidence: 99%

“…Using the associative memory, water-mediated interactions, structure and energy model (AWSEM), previous simulations by our group have successfully explained how the change of critical nucleus size arises from the differences in the propensity of monomeric polyQ repeats of different lengths to form β-hairpins: the longer repeats fold into hairpins intramolecularly before they aggregate (9). The aggregation of the diseasecausing peptide is, however, further complicated by the presence of flanking amino acid sequences in fragments encoded by HTT exon 1. Experiments indicate that the addition of NT17 at the N terminus of polyQ enormously accelerates the aggregation, probably by encouraging the formation of prefibrillar oligomers (10)(11)(12)(13)(14)(15)(16), whereas the addition of the proline-rich region at the C terminus decreases the rate of aggregation apparently without changing fundamentally the mechanism (10,16,17). Structural characterization of the aggregates (13,14,(18)(19)(20) has shown that, even when there are flanking sequences, polyQ remains the fiber core and adopts a β-hairpin conformation.…”

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confidence: 99%

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Aggregation landscapes of Huntingtin exon 1 protein fragments and the critical repeat length for the onset of Huntington’s disease

Chen

Wolynes

2017

Proc. Natl. Acad. Sci. U.S.A.

104

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Huntington's disease (HD) is a neurodegenerative disease caused by an abnormal expansion in the polyglutamine (polyQ) track of the Huntingtin (HTT) protein. The severity of the disease depends on the polyQ repeat length, arising only in patients with proteins having 36 repeats or more. Previous studies have shown that the aggregation of N-terminal fragments (encoded by HTT exon 1) underlies the disease pathology in mouse models and that the HTT exon 1 gene product can self-assemble into amyloid structures. Here, we provide detailed structural mechanisms for aggregation of several protein fragments encoded by HTT exon 1 by using the associative memory, water-mediated, structure and energy model (AWSEM) to construct their free energy landscapes. We find that the addition of the N-terminal 17-residue sequence (NT 17 ) facilitates polyQ aggregation by encouraging the formation of prefibrillar oligomers, whereas adding the C-terminal polyproline sequence (P 10 ) inhibits aggregation. The combination of both terminal additions in HTT exon 1 fragment leads to a complex aggregation mechanism with a basic core that resembles that found for the aggregation of pure polyQ repeats using AWSEM. At the extrapolated physiological concentration, although the grand canonical free energy profiles are uphill for HTT exon 1 fragments having 20 or 30 glutamines, the aggregation landscape for fragments with 40 repeats has become downhill. This computational prediction agrees with the critical length found for the onset of HD and suggests potential therapies based on blocking early binding events involving the terminal additions to the polyQ repeats.Huntington's disease | aggregation | solubility | aggregation free energy landscape | critical length H untingtin (HTT) is a huge protein (3,100 amino acid residues) that has been implicated in a variety of physiological functions (1, 2). Having an expanded polyglutamine (polyQ) region of 36 or more glutamine residues in the N terminus of HTT leads to Huntington's disease as witnessed by the deposition of large intracellular protein aggregates or inclusion bodies, which are comprised primarily of N-terminal fragments coded by the exon 1 sequence of the mutant HTT (2-5). These N-terminal fragments, each composed of an N-terminal 17-residue sequence (NT17), a polyQ sequence that has expanded in length, and a proline-rich region afterward, originate from proteolysis of HTT (2, 3). The aggregation of the HTT exon 1 product is, therefore, believed to cause Huntington's disease. Clinical studies have shown an inverse correlation between polyQ length and age of disease onset (5). By implicating polymer physics in the disease process, this regularity has intrigued biophysicists for decades.Expanded polyQ sequences, more generally, are associated with nine known neurodegenerative diseases (4). Biophysical chemists have, therefore, focused on first understanding the aggregation of pure polyQ peptides. The rate of aggregation of polyQ peptides is length-dependent, and primary nucleation is rate-limiti...

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Slow Amyloid Nucleation via α-Helix-Rich Oligomeric Intermediates in Short Polyglutamine-Containing Huntingtin Fragments

Cited by 176 publications

References 74 publications

Prion-like proteins sequester and suppress the toxicity of huntingtin exon 1

Prion-like proteins sequester and suppress the toxicity of huntingtin exon 1

Huntingtin protein interactions altered by polyglutamine expansion as determined by quantitative proteomic analysis

Aggregation landscapes of Huntingtin exon 1 protein fragments and the critical repeat length for the onset of Huntington’s disease

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