The Polyglutamine Expansion at the N-Terminal of Huntingtin Protein Modulates the Dynamic Configuration and Phosphorylation of the C-Terminal HEAT Domain

Jung, Tae‐Yang; Shin, Baehyun; Tamò, Giorgio E.; Kim, Hyeongju; Vijayvargia, Ravi; Leitner, Alexander; Marcaida, M.J.; Astorga‐Wells, Juan; Jung, Roy; Aebersold, Ruedi; Peraro, Matteo Dal; Hebert, Hans; Seong, Ihn Sik; Song, Ji‐Joon

doi:10.1016/j.str.2020.06.008

Cited by 28 publications

(40 citation statements)

References 75 publications

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“…As reported by Guo and colleagues 20 , we were also unable to express recombinant HAP40 alone, although it is readily expressed in the presence of HTT, a trend that parallels our in vivo observations. In the absence of HAP40, we and others have shown that recombinant HTT self-associates and is conformationally heterogenous in vitro 21,22,34 . Cryo-EM analysis of our apo HTT samples yielded a 12 Å resolution envelope (Figure 3a and b).…”

Section: Resultsmentioning

confidence: 78%

“…Biophysical and biochemical analyses comparing purified HTT and HTT-HAP40 samples have revealed that HAP40-bound forms of HTT exhibit reduced aggregation propensity, greater stability and monodispersity as well as conformational homogeneity 20,21 . Consequently, apo HTT is a more difficult sample to work with for structural and biophysical characterisation, and several studies to date have required cross-linking approaches to constrain the HTT molecule to facilitate its analysis, suggesting HTT-HAP40 interactions may stabilize HTT 22,23 . The biological function of the HTT-HAP40 complex however, remains elusive, and it is not clear if the function of this complex differs from apo HTT in vivo.…”

Section: Introductionmentioning

confidence: 99%

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HAP40 orchestrates huntingtin structure for differential interaction with polyglutamine expanded exon 1

Harding

Deme

Hevler

et al. 2021

Preprint

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Huntington's disease results from expansion of a glutamine-coding CAG tract in the huntingtin (HTT) gene, producing an aberrantly functioning form of HTT. Both wildtype and disease-state HTT form a hetero-dimer with HAP40 of unknown functional relevance. We demonstrate in vivo that HTT and HAP40 cellular abundance are coupled. Integrating data from a 2.6 Å cryo-electron microscopy structure, cross-linking mass spectrometry, small-angle X-ray scattering, and modeling, we provide a near-atomic-level view of HTT, its molecular interaction surfaces and compacted domain architecture, orchestrated by HAP40. Native mass-spectrometry reveals a remarkably stable hetero-dimer, potentially explaining the cellular inter-dependence of HTT and HAP40. The polyglutamine tract containing N-terminal exon 1 region of HTT is dynamic, but shows greater conformational variety in the mutant than wildtype exon 1. By providing novel insight into the structural consequences of HTT polyglutamine expansion, our data provide a foundation for future functional and drug discovery studies targeting Huntington's disease.

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Section: Resultsmentioning

confidence: 78%

Section: Introductionmentioning

confidence: 99%

HAP40 orchestrates huntingtin structure for differential interaction with polyglutamine expanded exon 1

Harding

Deme

Hevler

et al. 2021

Preprint

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“…At the same time, polyQ expansion does not result in an abrupt conformational change of the HTT N-terminus (Bravo-Arredondo et al, 2018; Newcombe et al, 2018; Warner et al, 2017). A recent study showed cryo-EM analyses at ∼10 Å resolution of recombinant 23QHTT and 78QHTT upon GraFix stabilization, in combination with XL-MS, small-angle X-ray scattering and hydrogen-deuterium exchange (Jung et al, 2020). This study indicated that apo HTT (i.e.…”

Section: Discussionmentioning

confidence: 99%

“…Apo HTT, i.e. not bound to HAP40, may be more flexible and undergo subtle conformational changes upon polyQ expansion (Jung et al, 2020). Whether such rearrangements are related to the described loss-or gain-of-function phenotypes of mutant full length HTT in HD (Cisbani and Cicchetti, 2012; Zuccato et al, 2010) requires further investigation.…”

Section: Discussionmentioning

confidence: 99%

“…Furthermore, polyQ expansion renders N-terminal fragments of HTT aggregation-prone in vitro and in vivo (Scherzinger et al, 1997), and similar fragments form inclusion bodies in the brain of HD patient (Difiglia et al, 1995). The effects of polyQ expansion on full length HTT are less well understood, but recent studies reported some conformational changes (Jung et al, 2020; Vijayvargia et al, 2016). However, only low-resolution structures of polyQ-expanded HTT were reported, limiting detailed understanding of the effects of polyQ expansion.…”

Section: Introductionmentioning

confidence: 99%

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PolyQ expansion does not alter the Huntingtin-HAP40 complex

Huang

Guo

et al. 2021

Preprint

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The abnormal amplification of a CAG repeat in the gene coding for huntingtin (HTT) leads to Huntington disease (HD). At the protein level, this translates into the expansion of a poly-glutamine (polyQ) stretch located at the HTT N-terminus, which renders it aggregation-prone by unknown mechanisms. Here we investigated the effects of polyQ expansion on HTT in a complex with its stabilizing interaction partner huntingtin-associated protein 40 (HAP40). Surprisingly, our comprehensive biophysical, crosslinking mass spectrometry and cryo-EM experiments revealed no major differences in the conformation of HTT-HAP40 complexes of various polyQ length, including 17QHTT-HAP40 (wild type), 46QHTT-HAP40 (typical polyQ length in HD patients) and 128QHTT-HAP40 (extreme polyQ length). Thus, HTT polyQ expansion does not alter the global structure of HTT when associated with HAP40.

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Interaction between huntingtin exon 1 and HEAT repeat structure probed by chimeric model proteins

Zhang,

Wu,

Itzhaki

et al. 2023

Protein Science

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Huntington disease (HD) is associated with aggregation of Huntingtin (HTT) protein containing over 35 continuous Q residues within the N‐terminal exon 1 encoded region. The C‐terminal of the HTT protein consists mainly of HEAT repeat structure which serves as a scaffold for multiple cellular activities. Structural and biochemical analysis of the intact HTT protein has been hampered by its huge size (~300 kD) and most in vitro studies to date have focused on the properties of the exon 1 region. To explore the interaction between HTT exon 1 and the HEAT repeat structure, we constructed chimeric proteins containing the N‐terminal HTT exon 1 region and the HEAT repeat protein PR65/A. The results indicate that HTT exon 1 slightly destabilizes the downstream HEAT repeat structure and endows the HEAT repeat structure with more conformational flexibility. Wild‐type and pathological lengths of polyQ did not show differences in the interaction between HTT exon 1 and the HEAT repeats. With the C‐terminal fusion of PR65/A, HTT exon 1 containing pathological lengths of polyQ could still form amyloid fibrils, but the higher‐order architecture of fibrils and kinetics of fibril formation were affected by the C‐terminal fusion of HEAT repeats. This indicates that interaction between HTT exon 1 and HEAT repeat structure is compatible with both normal function of HTT protein and the pathogenesis of HD, and this study provides a potential model for further exploration.This article is protected by copyright. All rights reserved.

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The Polyglutamine Expansion at the N-Terminal of Huntingtin Protein Modulates the Dynamic Configuration and Phosphorylation of the C-Terminal HEAT Domain

Cited by 28 publications

References 75 publications

HAP40 orchestrates huntingtin structure for differential interaction with polyglutamine expanded exon 1

HAP40 orchestrates huntingtin structure for differential interaction with polyglutamine expanded exon 1

PolyQ expansion does not alter the Huntingtin-HAP40 complex

Interaction between huntingtin exon 1 and HEAT repeat structure probed by chimeric model proteins

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