TDP-43 is a ubiquitylation substrate of the SCF^{cyclin F} complex

Authors

Stephanie L. Rayner, The Faculty of Medicine, Health and Human Sciences
Shu Yang, The Faculty of Medicine, Health and Human Sciences
Natalie E. Farrawell, University of Wollongong
Cyril J. Jagaraj, The Faculty of Medicine, Health and Human Sciences
Flora Cheng, The Faculty of Medicine, Health and Human Sciences
Jennilee M. Davidson, The Faculty of Medicine, Health and Human Sciences
Luan Luu, The Faculty of Medicine, Health and Human Sciences
Alberto G. Redondo, Hospital Universitario 12 de Octubre
Alberto Rábano, Reina Sofia-CIEN Foundation
Daniel Borrego-Hernández, Hospital Universitario 12 de Octubre
Julie D. Atkin, The Faculty of Medicine, Health and Human Sciences
Marco Morsch, The Faculty of Medicine, Health and Human Sciences
Ian P. Blair, The Faculty of Medicine, Health and Human Sciences
Justin J. Yerbury, University of Wollongong
Roger Chung, The Faculty of Medicine, Health and Human Sciences
Albert Lee, The Faculty of Medicine, Health and Human Sciences

Publication Name

Neurobiology of Disease

Abstract

Background: Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterised by the loss of upper and lower motor neurons in the brain and spinal cord. ALS and frontotemporal dementia (FTD) are overlapping diseases with shared pathological features. Affected neurons of people with ALS and FTD typically contain ubiquitin-immunoreactive inclusions, of which TDP-43 (Tar DNA-binding protein of 43 kDa) is a major component. However, what triggers the formation of these abnormal TDP-43 inclusions is unclear. Previously, we identified CCNF mutations in cohorts of familial and sporadic cases of ALS and FTD. CCNF encodes cyclin F, the substrate-binding component of a multiprotein E3 ubiquitin ligase complex that ubiquitylates and subsequently directs a set of protein substrates for proteasomal degradation. Here, we explored the relationship between cyclin F and TDP-43. Methods: We used a series of complementary biochemical approaches including immunoprecipitations, in vitro ubiquitylation assays, immunofluorescence imaging and immunocytochemistry. Unpaired student t-tests were used to determine statistical significance of the results. Results: In this study, we demonstrate that that the SCFcyclin F complex directly mediates the poly-ubiquitylation of TDP-43. Importantly, we demonstrate that cyclin F bearing the pathogenic ALS/FTD mutation, S621G, leads to aberrant ubiquitylation of TDP-43 as well as the accumulation of K48-ubiquitylated TDP-43 in neuron-like cells. Furthermore, we demonstrate that a patient carrying the ALS/FTD cyclin FS195R mutation displayed skein-like cytoplasmic TDP-43 aggregates, implying abnormal TDP-43 degradation in a CCNF mutation bearing patient. Conclusion: In summary, this study reports a direct ubiquitylation mechanism for TDP-43, revealing important insights into the regulation of cyclin F-mediated TDP-43 turnover and clues towards understanding the molecular origins of the ubiquitylated TDP-43 inclusions that are the hallmark pathological feature in ALS and FTD.

Open Access Status

This publication may be available as open access

Volume

167

Article Number

105673

Funding Number

IG2029

Funding Sponsor

Motor Neurone Disease Research Institute of Australia