Effect of Helical Flanking Sequences on the Morphology of Polyglutamine-Containing Fibrils

Kokona, Bashkim; Johnson, Karl A.; Fairman, Robert

doi:10.1021/bi501066q

Cited by 12 publications

(19 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A potential mechanism is N17 helix bundle formation that could bring polyQ regions from different proteins into close proximity (20, 21, 24 -26). Other studies, however, have challenged such a mechanism as substituting the N17 with a coiled-coil helical bundle reduced aggregation (27,28). In contrast to the N17, the PRD generally seems to retard aggregation (15,29,30), but the molecular underpinnings of this inhibitory function remain poorly understood.…”

mentioning

confidence: 99%

The 17-residue-long N terminus in huntingtin controls stepwise aggregation in solution and on membranes via different mechanisms

Pandey

Isas

Rawat

et al. 2018

Journal of Biological Chemistry

129

View full text Add to dashboard Cite

Aggregation of huntingtin protein arising from expanded polyglutamine (polyQ) sequences in the exon-1 region of mutant huntingtin plays a central role in the pathogenesis of Huntington's disease. The huntingtin aggregation pathways are of therapeutic and diagnostic interest, but obtaining critical information from the physiologically relevant htt exon-1 (Httex1) protein has been challenging. Using biophysical techniques and an expression and purification protocol that generates clean, monomeric Httex1, we identified and mapped three distinct aggregation pathways: 1) unseeded in solution; 2) seeded in solution; and 3) membrane-mediated. In solution, aggregation proceeded in a highly stepwise manner, in which the individual domains (N terminus containing 17 amino acids (N17), polyQ, and proline-rich domain (PRD)) become ordered at very different rates. The aggregation was initiated by an early oligomer requiring a pathogenic, expanded Gln length and N17 α-helix formation. In the second phase, β-sheet forms in the polyQ. The slowest step is the final structural maturation of the PRD. This stepwise mechanism could be bypassed by seeding, which potently accelerated aggregation and was a prerequisite for prion-like spreading Remarkably, membranes could catalyze aggregation even more potently than seeds, in a process that caused significant membrane damage. The N17 governed membrane-mediated aggregation by anchoring Httex1 to the membrane, enhancing local concentration and promoting collision via two-dimensional diffusion. Considering its central roles in solution and in membrane-mediated aggregation, the N17 represents an attractive target for inhibiting multiple pathways. Our approach should help evaluate such inhibitors and identify diagnostic markers for the misfolded forms identified here.

show abstract

mentioning

confidence: 99%

The 17-residue-long N terminus in huntingtin controls stepwise aggregation in solution and on membranes via different mechanisms

Pandey

Isas

Rawat

et al. 2018

Journal of Biological Chemistry

129

View full text Add to dashboard Cite

show abstract

“…For all of these polyQ diseases, it is the aggregate formation that leads to the disease. Longer polyQ segments are conducive to β-sheet formation 15 16 17 that are recognized by chaperone proteins as misfolded and produce the aggregates characteristic of the disease 5 18 19 . Other aggregate forming proteins can also become incorporated into Htt-polyQ aggregates 20 21 .…”

mentioning

confidence: 99%

Multiple discrete soluble aggregates influence polyglutamine toxicity in a Huntington’s disease model system

Wang

Laue

et al. 2016

Sci Rep

View full text Add to dashboard Cite

Huntington’s disease (HD) results from expansions of polyglutamine stretches (polyQ) in the huntingtin protein (Htt) that promote protein aggregation, neurodegeneration, and death. Since the diversity and sizes of the soluble Htt-polyQ aggregates that have been linked to cytotoxicity are unknown, we investigated soluble Htt-polyQ aggregates using analytical ultracentrifugation. Soon after induction in a yeast HD model system, non-toxic Htt-25Q and cytotoxic Htt-103Q both formed soluble aggregates 29S to 200S in size. Because current models indicate that Htt-25Q does not form soluble aggregates, reevaluation of previous studies may be necessary. Only Htt-103Q aggregation behavior changed, however, with time. At 6 hr mid-sized aggregates (33S to 84S) and large aggregates (greater than 100S) became present while at 24 hr primarily only mid-sized aggregates (20S to 80S) existed. Multiple factors that decreased cytotoxicity of Htt-103Q (changing the length of or sequences adjacent to the polyQ, altering ploidy or chaperone dosage, or deleting anti-aging factors) altered the Htt-103Q aggregation pattern in which the suite of mid-sized aggregates at 6 hr were most correlative with cytotoxicity. Hence, the amelioration of HD and other neurodegenerative diseases may require increased attention to and discrimination of the dynamic alterations in soluble aggregation processes.

show abstract

“…43 Two mutations on htt NT tract, S13D and S16D, are also known to have an inhibitory effect on htt aggregation 44 and are thought to cause a loss of cross-talk between htt NT and the polyQ tract. 45 htt NT is also known to regulate the aggregation of htt exon 1 fragments on lipid membranes. [46][47][48] To explain the mechanism of htt exon 1 aggregation on lipid membranes Michalek et al 49 proposed a model analogous to the Wetzel's proximity model where the amphiphatic nature of htt NT guides the membrane anchorage and aggregation.…”

Section: Introductionmentioning

confidence: 99%

Assembly of Huntingtin headpiece into α-helical bundles

Özgür

Sayar

2017

Biointerphases

View full text Add to dashboard Cite

Protein aggregation is a hallmark of neurodegenerative disorders. In this group of brain-related disorders, a disease-specific "host" protein or fragment misfolds and adopts a metastatic, aggregate-prone conformation. Often, this misfolded conformation is structurally and thermodynamically different from its native state. Intermolecular contacts, which arise in this non-native state, promote aggregation. In this regard, understanding the molecular principles and mechanisms that lead to the formation of such a non-native state and further promote the formation of the critical nucleus for fiber growth is essential. In this study, the authors analyze the aggregation propensity of Huntingtin headpiece (htt), which is known to facilitate the polyQ aggregation, in relation to the helix mediated aggregation mechanism proposed by the Wetzel group. The authors demonstrate that even though htt displays a degenerate conformational spectrum on its own, interfaces of macroscopic or molecular origin can promote the α-helix conformation, eliminating all other alternatives in the conformational phase space. Our findings indicate that htt molecules do not have a strong orientational preference for parallel or antiparallel orientation of the helices within the aggregate. However, a parallel packed bundle of helices would support the idea of increased polyglutamine concentration, to pave the way for cross-β structures.

show abstract

Effect of Helical Flanking Sequences on the Morphology of Polyglutamine-Containing Fibrils

Cited by 12 publications

References 30 publications

The 17-residue-long N terminus in huntingtin controls stepwise aggregation in solution and on membranes via different mechanisms

The 17-residue-long N terminus in huntingtin controls stepwise aggregation in solution and on membranes via different mechanisms

Multiple discrete soluble aggregates influence polyglutamine toxicity in a Huntington’s disease model system

Assembly of Huntingtin headpiece into α-helical bundles

Contact Info

Product

Resources

About