Synaptic localization of C9orf72 regulates post-synaptic glutamate receptor 1 levels
Abstract A hexanucleotide repeat expansion in a noncoding region of C9orf72 is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Reduction of select or total C9orf72 transcript and protein levels is observed in postmortem C9-ALS/FTD tissue, and l...
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| Format: | Article |
| Language: | English |
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BMC
2019-10-01
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| Series: | Acta Neuropathologica Communications |
| Subjects: | |
| Online Access: | http://link.springer.com/article/10.1186/s40478-019-0812-5 |
| _version_ | 1828868492652183552 |
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| author | Shangxi Xiao Paul M. McKeever Agnes Lau Janice Robertson |
| author_facet | Shangxi Xiao Paul M. McKeever Agnes Lau Janice Robertson |
| author_sort | Shangxi Xiao |
| collection | DOAJ |
| description | Abstract A hexanucleotide repeat expansion in a noncoding region of C9orf72 is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Reduction of select or total C9orf72 transcript and protein levels is observed in postmortem C9-ALS/FTD tissue, and loss of C9orf72 orthologues in zebrafish and C. elegans results in motor deficits. However, how the reduction in C9orf72 in ALS and FTD might contribute to the disease process remains poorly understood. It has been shown that C9orf72 interacts and forms a complex with SMCR8 and WDR41, acting as a guanine exchange factor for Rab GTPases. Given the known synaptosomal compartmentalization of C9orf72-interacting Rab GTPases, we hypothesized that C9orf72 localization to synaptosomes would be required for the regulation of Rab GTPases and receptor trafficking. This study combined synaptosomal and post-synaptic density preparations together with a knockout-confirmed monoclonal antibody for C9orf72 to assess the localization and role of C9orf72 in the synaptosomes of mouse forebrains. Here, we found C9orf72 to be localized to both the pre- and post-synaptic compartment, as confirmed by both post-synaptic immunoprecipitation and immunofluorescence labelling. In C9orf72 knockout (C9-KO) mice, we demonstrated that pre-synaptic Rab3a, Rab5, and Rab11 protein levels remained stable compared with wild-type littermates (C9-WT). Strikingly, post-synaptic preparations from C9-KO mouse forebrains demonstrated a complete loss of Smcr8 protein levels, together with a significant downregulation of Rab39b and a concomitant upregulation of GluR1 compared with C9-WT mice. We confirmed the localization of Rab39b downregulation and GluR1 upregulation to the dorsal hippocampus of C9-KO mice by immunofluorescence. These results indicate that C9orf72 is essential for the regulation of post-synaptic receptor levels, and implicates loss of C9orf72 in contributing to synaptic dysfunction and related excitotoxicity in ALS and FTD. |
| first_indexed | 2024-12-13T05:32:05Z |
| format | Article |
| id | doaj.art-eaf039e67a234a998104f02f75917a01 |
| institution | Directory Open Access Journal |
| issn | 2051-5960 |
| language | English |
| last_indexed | 2024-12-13T05:32:05Z |
| publishDate | 2019-10-01 |
| publisher | BMC |
| record_format | Article |
| series | Acta Neuropathologica Communications |
| spelling | doaj.art-eaf039e67a234a998104f02f75917a012022-12-21T23:58:02ZengBMCActa Neuropathologica Communications2051-59602019-10-017111310.1186/s40478-019-0812-5Synaptic localization of C9orf72 regulates post-synaptic glutamate receptor 1 levelsShangxi Xiao0Paul M. McKeever1Agnes Lau2Janice Robertson3Tanz Centre for Research in Neurodegenerative Diseases, University of TorontoTanz Centre for Research in Neurodegenerative Diseases, University of TorontoTanz Centre for Research in Neurodegenerative Diseases, University of TorontoTanz Centre for Research in Neurodegenerative Diseases, University of TorontoAbstract A hexanucleotide repeat expansion in a noncoding region of C9orf72 is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Reduction of select or total C9orf72 transcript and protein levels is observed in postmortem C9-ALS/FTD tissue, and loss of C9orf72 orthologues in zebrafish and C. elegans results in motor deficits. However, how the reduction in C9orf72 in ALS and FTD might contribute to the disease process remains poorly understood. It has been shown that C9orf72 interacts and forms a complex with SMCR8 and WDR41, acting as a guanine exchange factor for Rab GTPases. Given the known synaptosomal compartmentalization of C9orf72-interacting Rab GTPases, we hypothesized that C9orf72 localization to synaptosomes would be required for the regulation of Rab GTPases and receptor trafficking. This study combined synaptosomal and post-synaptic density preparations together with a knockout-confirmed monoclonal antibody for C9orf72 to assess the localization and role of C9orf72 in the synaptosomes of mouse forebrains. Here, we found C9orf72 to be localized to both the pre- and post-synaptic compartment, as confirmed by both post-synaptic immunoprecipitation and immunofluorescence labelling. In C9orf72 knockout (C9-KO) mice, we demonstrated that pre-synaptic Rab3a, Rab5, and Rab11 protein levels remained stable compared with wild-type littermates (C9-WT). Strikingly, post-synaptic preparations from C9-KO mouse forebrains demonstrated a complete loss of Smcr8 protein levels, together with a significant downregulation of Rab39b and a concomitant upregulation of GluR1 compared with C9-WT mice. We confirmed the localization of Rab39b downregulation and GluR1 upregulation to the dorsal hippocampus of C9-KO mice by immunofluorescence. These results indicate that C9orf72 is essential for the regulation of post-synaptic receptor levels, and implicates loss of C9orf72 in contributing to synaptic dysfunction and related excitotoxicity in ALS and FTD.http://link.springer.com/article/10.1186/s40478-019-0812-5Amyotrophic lateral sclerosisFrontotemporal dementiaC9orf72PSD-95GluR1Rab39b |
| spellingShingle | Shangxi Xiao Paul M. McKeever Agnes Lau Janice Robertson Synaptic localization of C9orf72 regulates post-synaptic glutamate receptor 1 levels Acta Neuropathologica Communications Amyotrophic lateral sclerosis Frontotemporal dementia C9orf72 PSD-95 GluR1 Rab39b |
| title | Synaptic localization of C9orf72 regulates post-synaptic glutamate receptor 1 levels |
| title_full | Synaptic localization of C9orf72 regulates post-synaptic glutamate receptor 1 levels |
| title_fullStr | Synaptic localization of C9orf72 regulates post-synaptic glutamate receptor 1 levels |
| title_full_unstemmed | Synaptic localization of C9orf72 regulates post-synaptic glutamate receptor 1 levels |
| title_short | Synaptic localization of C9orf72 regulates post-synaptic glutamate receptor 1 levels |
| title_sort | synaptic localization of c9orf72 regulates post synaptic glutamate receptor 1 levels |
| topic | Amyotrophic lateral sclerosis Frontotemporal dementia C9orf72 PSD-95 GluR1 Rab39b |
| url | http://link.springer.com/article/10.1186/s40478-019-0812-5 |
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