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Harding RJ, Deme JC, Hevler JF, Tamara S, Lemak A, Cantle JP, Szewczyk MM, Begeja N, Goss S, Zuo X, Loppnau P, Seitova A, Hutchinson A, Fan L, Truant R, Schapira M, Carroll JB, Heck AJR, Lea SM, Arrowsmith CH. Huntingtin structure is orchestrated by HAP40 and shows a polyglutamine expansion-specific interaction with exon 1. Commun Biol 2021; 4:1374. [PMID: 34880419 PMCID: PMC8654980 DOI: 10.1038/s42003-021-02895-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2021] [Accepted: 11/09/2021] [Indexed: 12/14/2022] Open
Abstract
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 and in cell models 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 exon 1 region of HTT is dynamic but shows greater conformational variety in the polyglutamine expanded mutant than wildtype exon 1. Our data provide a foundation for future functional and drug discovery studies targeting Huntington's disease and illuminate the structural consequences of HTT polyglutamine expansion.
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Affiliation(s)
- Rachel J Harding
- Structural Genomics Consortium, University of Toronto, Toronto, ON, M5G 1L7, Canada.
| | - Justin C Deme
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford, OX1 3RE, UK
- Central Oxford Structural Molecular Imaging Centre, University of Oxford, South Parks Road, Oxford, OX1 3RE, UK
- Center for Structural Biology, Center for Cancer Research, National Cancer Institute, Frederick, MD, 21702, USA
| | - Johannes F Hevler
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute of Pharmaceutical Sciences, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands
- Netherlands Proteomics Center, Padualaan 8, 3584 CH, Utrecht, The Netherlands
| | - Sem Tamara
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute of Pharmaceutical Sciences, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands
- Netherlands Proteomics Center, Padualaan 8, 3584 CH, Utrecht, The Netherlands
| | - Alexander Lemak
- Princess Margaret Cancer Centre and Department of Medical Biophysics, University of Toronto, Toronto, ON, M5G 1L7, Canada
| | - Jeffrey P Cantle
- Behavioral Neuroscience Program, Department of Psychology, Western Washington University, Bellingham, WA, 98225, USA
| | - Magdalena M Szewczyk
- Structural Genomics Consortium, University of Toronto, Toronto, ON, M5G 1L7, Canada
| | - Nola Begeja
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, L8S 4K1, Canada
| | - Siobhan Goss
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, L8S 4K1, Canada
| | - Xiaobing Zuo
- X-ray Science Division, Argonne National Laboratory, Lemont, IL, 60439, USA
| | - Peter Loppnau
- Structural Genomics Consortium, University of Toronto, Toronto, ON, M5G 1L7, Canada
| | - Alma Seitova
- Structural Genomics Consortium, University of Toronto, Toronto, ON, M5G 1L7, Canada
| | - Ashley Hutchinson
- Structural Genomics Consortium, University of Toronto, Toronto, ON, M5G 1L7, Canada
| | - Lixin Fan
- Basic Science Program, Frederick National Laboratory for Cancer Research, SAXS Core of NCI, National Institutes of Health, Frederick, MD, 21701, USA
| | - Ray Truant
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON, L8S 4K1, Canada
| | - Matthieu Schapira
- Structural Genomics Consortium, University of Toronto, Toronto, ON, M5G 1L7, Canada
- Department of Pharmacology and Toxicology, University of Toronto, Toronto, ON, M5S 1A8, Canada
| | - Jeffrey B Carroll
- Behavioral Neuroscience Program, Department of Psychology, Western Washington University, Bellingham, WA, 98225, USA
| | - Albert J R Heck
- Biomolecular Mass Spectrometry and Proteomics, Bijvoet Center for Biomolecular Research and Utrecht Institute of Pharmaceutical Sciences, Utrecht University, Padualaan 8, 3584 CH, Utrecht, The Netherlands
- Netherlands Proteomics Center, Padualaan 8, 3584 CH, Utrecht, The Netherlands
| | - Susan M Lea
- Sir William Dunn School of Pathology, University of Oxford, South Parks Road, Oxford, OX1 3RE, UK
- Central Oxford Structural Molecular Imaging Centre, University of Oxford, South Parks Road, Oxford, OX1 3RE, UK
- Center for Structural Biology, Center for Cancer Research, National Cancer Institute, Frederick, MD, 21702, USA
| | - Cheryl H Arrowsmith
- Structural Genomics Consortium, University of Toronto, Toronto, ON, M5G 1L7, Canada.
- Princess Margaret Cancer Centre and Department of Medical Biophysics, University of Toronto, Toronto, ON, M5G 1L7, Canada.
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Babbi G, Savojardo C, Martelli PL, Casadio R. Huntingtin: A Protein with a Peculiar Solvent Accessible Surface. Int J Mol Sci 2021; 22:ijms22062878. [PMID: 33809039 PMCID: PMC8001614 DOI: 10.3390/ijms22062878] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2021] [Revised: 03/04/2021] [Accepted: 03/04/2021] [Indexed: 11/30/2022] Open
Abstract
Taking advantage of the last cryogenic electron microscopy structure of human huntingtin, we explored with computational methods its physicochemical properties, focusing on the solvent accessible surface of the protein and highlighting a quite interesting mix of hydrophobic and hydrophilic patterns, with the prevalence of the latter ones. We then evaluated the probability of exposed residues to be in contact with other proteins, discovering that they tend to cluster in specific regions of the protein. We then found that the remaining portions of the protein surface can contain calcium-binding sites that we propose here as putative mediators for the protein to interact with membranes. Our findings are justified in relation to the present knowledge of huntingtin functional annotation.
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Affiliation(s)
- Giulia Babbi
- Biocomputing Group, University of Bologna, Via San Giacomo 9/2, 40126 Bologna, Italy; (G.B.); (C.S.); (R.C.)
| | - Castrense Savojardo
- Biocomputing Group, University of Bologna, Via San Giacomo 9/2, 40126 Bologna, Italy; (G.B.); (C.S.); (R.C.)
| | - Pier Luigi Martelli
- Biocomputing Group, University of Bologna, Via San Giacomo 9/2, 40126 Bologna, Italy; (G.B.); (C.S.); (R.C.)
- Correspondence: ; Tel.: +39-051-2094005
| | - Rita Casadio
- Biocomputing Group, University of Bologna, Via San Giacomo 9/2, 40126 Bologna, Italy; (G.B.); (C.S.); (R.C.)
- Institute of Biomembranes, Bioenergetics and Molecular Biotechnologies, National Research Council, Via Giovanni Amendola 122/O, 70126 Bari, Italy
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Posey AE, Ruff KM, Harmon TS, Crick SL, Li A, Diamond MI, Pappu RV. Profilin reduces aggregation and phase separation of huntingtin N-terminal fragments by preferentially binding to soluble monomers and oligomers. J Biol Chem 2018; 293:3734-3746. [PMID: 29358329 PMCID: PMC5846159 DOI: 10.1074/jbc.ra117.000357] [Citation(s) in RCA: 79] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2017] [Revised: 01/16/2018] [Indexed: 11/06/2022] Open
Abstract
Huntingtin N-terminal fragments (Htt-NTFs) with expanded polyglutamine tracts form a range of neurotoxic aggregates that are associated with Huntington's disease. Here, we show that aggregation of Htt-NTFs, irrespective of polyglutamine length, yields at least three phases (designated M, S, and F) that are delineated by sharp concentration thresholds and distinct aggregate sizes and morphologies. We found that monomers and oligomers make up the soluble M phase, ∼25-nm spheres dominate in the soluble S phase, and long, linear fibrils make up the insoluble F phase. Previous studies showed that profilin, an abundant cellular protein, reduces Htt-NTF aggregation and toxicity in cells. We confirm that profilin achieves its cellular effects through direct binding to the C-terminal proline-rich region of Htt-NTFs. We show that profilin preferentially binds to Htt-NTF M-phase species and destabilizes aggregation and phase separation by shifting the concentration boundaries for phase separation to higher values through a process known as polyphasic linkage. Our experiments, aided by coarse-grained computer simulations and theoretical analysis, suggest that preferential binding of profilin to the M-phase species of Htt-NTFs is enhanced through a combination of specific interactions between profilin and polyproline segments and auxiliary interactions between profilin and polyglutamine tracts. Polyphasic linkage may be a general strategy that cells utilize to regulate phase behavior of aggregation-prone proteins. Accordingly, detailed knowledge of phase behavior and an understanding of how ligands modulate phase boundaries may pave the way for developing new therapeutics against a variety of aggregation-prone proteins.
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Affiliation(s)
- Ammon E Posey
- From the Department of Biomedical Engineering and Center for Biological Systems Engineering, Washington University, St. Louis, Missouri 63130
| | - Kiersten M Ruff
- From the Department of Biomedical Engineering and Center for Biological Systems Engineering, Washington University, St. Louis, Missouri 63130
| | - Tyler S Harmon
- From the Department of Biomedical Engineering and Center for Biological Systems Engineering, Washington University, St. Louis, Missouri 63130
| | - Scott L Crick
- From the Department of Biomedical Engineering and Center for Biological Systems Engineering, Washington University, St. Louis, Missouri 63130
| | - Aimin Li
- the Department of Neurology, Washington University School of Medicine, St. Louis, Missouri 63108
| | - Marc I Diamond
- the Center for Alzheimer's and Neurodegenerative Diseases, University of Texas Southwestern Medical Center, Dallas, Texas 75390, and
| | - Rohit V Pappu
- From the Department of Biomedical Engineering and Center for Biological Systems Engineering, Washington University, St. Louis, Missouri 63130,
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