An Expanded Polyproline Domain Maintains Mutant Huntingtin Soluble in vivo and During Aging
Huntington’s disease is a dominantly inherited neurodegenerative disorder caused by the expansion of a CAG repeat, encoding for the amino acid glutamine (Q), present in the first exon of the protein huntingtin. Over the threshold of Q39 HTT exon 1 (HTTEx1) tends to misfold and aggregate into large i...
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Frontiers Media S.A.
2021-10-01
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| Series: | Frontiers in Molecular Neuroscience |
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| Online Access: | https://www.frontiersin.org/articles/10.3389/fnmol.2021.721749/full |
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| author | Maria Lucia Pigazzini Maria Lucia Pigazzini Mandy Lawrenz Anca Margineanu Gabriele S. Kaminski Schierle Janine Kirstein Janine Kirstein |
| author_facet | Maria Lucia Pigazzini Maria Lucia Pigazzini Mandy Lawrenz Anca Margineanu Gabriele S. Kaminski Schierle Janine Kirstein Janine Kirstein |
| author_sort | Maria Lucia Pigazzini |
| collection | DOAJ |
| description | Huntington’s disease is a dominantly inherited neurodegenerative disorder caused by the expansion of a CAG repeat, encoding for the amino acid glutamine (Q), present in the first exon of the protein huntingtin. Over the threshold of Q39 HTT exon 1 (HTTEx1) tends to misfold and aggregate into large intracellular structures, but whether these end-stage aggregates or their on-pathway intermediates are responsible for cytotoxicity is still debated. HTTEx1 can be separated into three domains: an N-terminal 17 amino acid region, the polyglutamine (polyQ) expansion and a C-terminal proline rich domain (PRD). Alongside the expanded polyQ, these flanking domains influence the aggregation propensity of HTTEx1: with the N17 initiating and promoting aggregation, and the PRD modulating it. In this study we focus on the first 11 amino acids of the PRD, a stretch of pure prolines, which are an evolutionary recent addition to the expanding polyQ region. We hypothesize that this proline region is expanding alongside the polyQ to counteract its ability to misfold and cause toxicity, and that expanding this proline region would be overall beneficial. We generated HTTEx1 mutants lacking both flanking domains singularly, missing the first 11 prolines of the PRD, or with this stretch of prolines expanded. We then followed their aggregation landscape in vitro with a battery of biochemical assays, and in vivo in novel models of C. elegans expressing the HTTEx1 mutants pan-neuronally. Employing fluorescence lifetime imaging we could observe the aggregation propensity of all HTTEx1 mutants during aging and correlate this with toxicity via various phenotypic assays. We found that the presence of an expanded proline stretch is beneficial in maintaining HTTEx1 soluble over time, regardless of polyQ length. However, the expanded prolines were only advantageous in promoting the survival and fitness of an organism carrying a pathogenic stretch of Q48 but were extremely deleterious to the nematode expressing a physiological stretch of Q23. Our results reveal the unique importance of the prolines which have and still are evolving alongside expanding glutamines to promote the function of HTTEx1 and avoid pathology. |
| first_indexed | 2024-12-18T00:23:50Z |
| format | Article |
| id | doaj.art-f23ad7c67f1d443d98b3d5a369fb13d2 |
| institution | Directory Open Access Journal |
| issn | 1662-5099 |
| language | English |
| last_indexed | 2024-12-18T00:23:50Z |
| publishDate | 2021-10-01 |
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| series | Frontiers in Molecular Neuroscience |
| spelling | doaj.art-f23ad7c67f1d443d98b3d5a369fb13d22022-12-21T21:27:17ZengFrontiers Media S.A.Frontiers in Molecular Neuroscience1662-50992021-10-011410.3389/fnmol.2021.721749721749An Expanded Polyproline Domain Maintains Mutant Huntingtin Soluble in vivo and During AgingMaria Lucia Pigazzini0Maria Lucia Pigazzini1Mandy Lawrenz2Anca Margineanu3Gabriele S. Kaminski Schierle4Janine Kirstein5Janine Kirstein6Department of Molecular Physiology and Cell Biology, Leibniz Research Institute for Molecular Pharmacology in the Forschungsverbund Berlin e.V. (FMP), Berlin, GermanyNeuroCure Cluster of Excellence, Charité Universitätsmedizin Berlin, Berlin, GermanyDepartment of Molecular Physiology and Cell Biology, Leibniz Research Institute for Molecular Pharmacology in the Forschungsverbund Berlin e.V. (FMP), Berlin, GermanyAdvanced Light Microscopy, Max-Delbrück Centrum for Molecular Medicine (MDC), Berlin, GermanyMolecular Neuroscience Group, Department of Chemical Engineering and Biotechnology, University of Cambridge, Cambridge, United KingdomDepartment of Molecular Physiology and Cell Biology, Leibniz Research Institute for Molecular Pharmacology in the Forschungsverbund Berlin e.V. (FMP), Berlin, GermanyDepartment of Cell Biology, University of Bremen, Bremen, GermanyHuntington’s disease is a dominantly inherited neurodegenerative disorder caused by the expansion of a CAG repeat, encoding for the amino acid glutamine (Q), present in the first exon of the protein huntingtin. Over the threshold of Q39 HTT exon 1 (HTTEx1) tends to misfold and aggregate into large intracellular structures, but whether these end-stage aggregates or their on-pathway intermediates are responsible for cytotoxicity is still debated. HTTEx1 can be separated into three domains: an N-terminal 17 amino acid region, the polyglutamine (polyQ) expansion and a C-terminal proline rich domain (PRD). Alongside the expanded polyQ, these flanking domains influence the aggregation propensity of HTTEx1: with the N17 initiating and promoting aggregation, and the PRD modulating it. In this study we focus on the first 11 amino acids of the PRD, a stretch of pure prolines, which are an evolutionary recent addition to the expanding polyQ region. We hypothesize that this proline region is expanding alongside the polyQ to counteract its ability to misfold and cause toxicity, and that expanding this proline region would be overall beneficial. We generated HTTEx1 mutants lacking both flanking domains singularly, missing the first 11 prolines of the PRD, or with this stretch of prolines expanded. We then followed their aggregation landscape in vitro with a battery of biochemical assays, and in vivo in novel models of C. elegans expressing the HTTEx1 mutants pan-neuronally. Employing fluorescence lifetime imaging we could observe the aggregation propensity of all HTTEx1 mutants during aging and correlate this with toxicity via various phenotypic assays. We found that the presence of an expanded proline stretch is beneficial in maintaining HTTEx1 soluble over time, regardless of polyQ length. However, the expanded prolines were only advantageous in promoting the survival and fitness of an organism carrying a pathogenic stretch of Q48 but were extremely deleterious to the nematode expressing a physiological stretch of Q23. Our results reveal the unique importance of the prolines which have and still are evolving alongside expanding glutamines to promote the function of HTTEx1 and avoid pathology.https://www.frontiersin.org/articles/10.3389/fnmol.2021.721749/fullC. eleganshuntingtin (HTT)polyQprolineaggregationfluorescence life time imaging |
| spellingShingle | Maria Lucia Pigazzini Maria Lucia Pigazzini Mandy Lawrenz Anca Margineanu Gabriele S. Kaminski Schierle Janine Kirstein Janine Kirstein An Expanded Polyproline Domain Maintains Mutant Huntingtin Soluble in vivo and During Aging Frontiers in Molecular Neuroscience C. elegans huntingtin (HTT) polyQ proline aggregation fluorescence life time imaging |
| title | An Expanded Polyproline Domain Maintains Mutant Huntingtin Soluble in vivo and During Aging |
| title_full | An Expanded Polyproline Domain Maintains Mutant Huntingtin Soluble in vivo and During Aging |
| title_fullStr | An Expanded Polyproline Domain Maintains Mutant Huntingtin Soluble in vivo and During Aging |
| title_full_unstemmed | An Expanded Polyproline Domain Maintains Mutant Huntingtin Soluble in vivo and During Aging |
| title_short | An Expanded Polyproline Domain Maintains Mutant Huntingtin Soluble in vivo and During Aging |
| title_sort | expanded polyproline domain maintains mutant huntingtin soluble in vivo and during aging |
| topic | C. elegans huntingtin (HTT) polyQ proline aggregation fluorescence life time imaging |
| url | https://www.frontiersin.org/articles/10.3389/fnmol.2021.721749/full |
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