Interactome screening of C9orf72 dipeptide repeats reveals VCP sequestration and functional impairment by polyGA

Janja Bozič, Helena Motaln, Anja Pucer Janez, Lara Markič, Priyanka Tripathi, Alfred Yamoah, Eleonora Aronica, Youn Bok Lee, Raphael Heilig, Roman Fischer, Andrew J. Thompson, Anand Goswami, Boris Rogelj*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)

Abstract

Repeat expansions in the C9orf72 gene are a common cause of amyotrophic lateral sclerosis and frontotemporal lobar degeneration, two devastating neurodegenerative disorders. One of the proposed mechanisms of GGGGCC repeat expansion is their translation into non-canonical dipeptide repeats, which can then accumulate as aggregates and contribute to these pathologies. There are five different dipeptide repeat proteins (polyGA, polyGR, polyPR, polyPA and polyGP), some of which are known to be neurotoxic. In the present study, we used BioID2 proximity labelling to identify the interactomes of all five dipeptide repeat proteins consisting of 125 repeats each. We identified 113 interacting partners for polyGR, 90 for polyGA, 106 for polyPR, 25 for polyPA and 27 for polyGP. Gene Ontology enrichment analysis of the proteomic data revealed that these target interaction partners are involved in a variety of functions, including protein translation, signal transduction pathways, protein catabolic processes, amide metabolic processes and RNA-binding. Using autopsy brain tissue from patients with C9orf72 expansion complemented with cell culture analysis, we evaluated the interactions between polyGA and valosin containing protein (VCP). Functional analysis of this interaction revealed sequestration of VCP with polyGA aggregates, altering levels of soluble valosin-containing protein. VCP also functions in autophagy processes, and consistent with this, we observed altered autophagy in cells expressing polyGA. We also observed altered co-localization of polyGA aggregates and p62 in cells depleted of VCP. All together, these data suggest that sequestration of VCP with polyGA aggregates contributes to the loss of VCP function, and consequently to alterations in autophagy processes in C9orf72 expansion disorders.

Original languageEnglish
Pages (from-to)684-699
Number of pages16
JournalBrain
Volume145
Issue number2
DOIs
Publication statusPublished - 1 Feb 2022

Keywords

  • ALS
  • autophagy
  • C9orf72
  • VCP

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