C9ORF72, implicated in amytrophic lateral sclerosis and frontotemporal dementia, regulates endosomal trafficking

Manal A. Farg, Vinod Sundaramoorthy, Jessica M. Sultana, Shu Yang, Rachel A K Atkinson, Vita Levina, Mark A. Halloran, Paul A. Gleeson, Ian P. Blair, Kai Y. Soo, Anna E. King, Julie D. Atkin*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

313 Citations (Scopus)
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Abstract

Intronic expansion of a hexanucleotideGGGGCCrepeat in the chromosome9 open reading frame72 (C9ORF72) geneisthemajorcauseoffamilialamyotrophic lateral sclerosis(ALS)andfrontotemporaldementia.However,the cellular function of theC9ORF72 protein remains unknown. Here,wedemonstrate thatC9ORF72 regulates endosomal trafficking. C9ORF72 colocalized with Rab proteins implicated in autophagy and endocytic transport: Rab1, Rab5, Rab7 and Rab11 in neuronal cell lines, primary cortical neurons and human spinal cord motor neurons, consistent with previous predictionsthatC9ORF72 bearsRabguanine exchange factor activity.Consistent with this notion, C9ORF72 was present in the extracellular space and as cytoplasmic vesicles. Depletion of C9ORF72 using siRNA inhibited transport of Shiga toxin fromthe plasmamembrane to Golgi apparatus, internalizationofTrkBreceptorandalteredthe ratio ofautophagosomemarker lightchain3(LC3) II:LC3I, indicatingthat C9ORF72 regulates endocytosis and autophagy. C9ORF72 also colocalized with ubiquilin-2 and LC3-positive vesicles, and co-migrated with lysosome-stained vesicles in neuronal cell lines, providing further evidence thatC9ORF72regulates autophagy. Investigationof proteinsinteractingwithC9ORF72usingmassspectrometry identified other proteins implicated in ALS; ubiquilin-2 and heterogeneous nuclear ribonucleoproteins, hnRNPA2/B1 and hnRNPA1, and actin. Treatment of cells overexpressing C9ORF72 with proteasome inhibitors induced the formation of stress granules positive for hnRNPA1 and hnRNPA2/B1. Immunohistochemistry of C9ORF72 ALS patient motor neurons revealed increased colocalization between C9ORF72 and Rab7 and Rab11 compared with controls, suggesting possible dysregulation of trafficking in patients bearing the C9ORF72 repeat expansion. Hence, this study identifies a role for C9ORF72 in Rab-mediated cellular trafficking.

Original languageEnglish
Article numberddu068
Pages (from-to)3579-3595
Number of pages17
JournalHuman Molecular Genetics
Volume23
Issue number13
DOIs
Publication statusPublished - Jul 2014

Bibliographical note

Copyright the Author(s) 2014. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.
A corrigendum exists for this article, and can be found in Human Molecular Genetics (2017), Volume 26, Issue 20, Pages 4093–4094. At: https://doi.org/10.1093/hmg/ddx309

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