Format

Send to

Choose Destination
Cell Mol Life Sci. 2018 Jan;75(2):335-354. doi: 10.1007/s00018-017-2632-8. Epub 2017 Aug 29.

Pathogenic mutation in the ALS/FTD gene, CCNF, causes elevated Lys48-linked ubiquitylation and defective autophagy.

Author information

1
Centre for Motor Neuron Disease Research, Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Macquarie University, 2 Technology Place, North Ryde, NSW, 2109, Australia. albert.lee@mq.edu.au.
2
Australian Proteome Analysis Facility, Macquarie University, Research Park Drive, North Ryde, NSW, 2109, Australia. albert.lee@mq.edu.au.
3
Centre for Motor Neuron Disease Research, Department of Biomedical Sciences, Faculty of Medicine and Health Sciences, Macquarie University, 2 Technology Place, North Ryde, NSW, 2109, Australia.
4
Department of Chemistry and Biomolecular Sciences, Faculty of Science and Engineering, Macquarie University, Research Park Drive, North Ryde, NSW, 2109, Australia.
5
Illawarra Health and Medical Research Institute, School of Biological Sciences, University of Wollongong, Northfields Avenue, Wollongong, NSW, 2522, Australia.
6
Department of Biochemistry and Genetics, La Trobe Institute for Molecular Science, Melbourne, VIC, 3086, Australia.
7
Australian Proteome Analysis Facility, Macquarie University, Research Park Drive, North Ryde, NSW, 2109, Australia.

Abstract

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are fatal neurodegenerative disorders that have common molecular and pathogenic characteristics, such as aberrant accumulation and ubiquitylation of TDP-43; however, the mechanisms that drive this process remain poorly understood. We have recently identified CCNF mutations in familial and sporadic ALS and FTD patients. CCNF encodes cyclin F, a component of an E3 ubiquitin-protein ligase (SCFcyclin F) complex that is responsible for ubiquitylating proteins for degradation by the ubiquitin-proteasome system. In this study, we examined the ALS/FTD-causing p.Ser621Gly (p.S621G) mutation in cyclin F and its effect upon downstream Lys48-specific ubiquitylation in transfected Neuro-2A and SH-SY5Y cells. Expression of mutant cyclin FS621G caused increased Lys48-specific ubiquitylation of proteins in neuronal cells compared to cyclin FWT. Proteomic analysis of immunoprecipitated Lys48-ubiquitylated proteins from mutant cyclin FS621G-expressing cells identified proteins that clustered within the autophagy pathway, including sequestosome-1 (p62/SQSTM1), heat shock proteins, and chaperonin complex components. Examination of autophagy markers p62, LC3, and lysosome-associated membrane protein 2 (Lamp2) in cells expressing mutant cyclin FS621G revealed defects in the autophagy pathway specifically resulting in impairment in autophagosomal-lysosome fusion. This finding highlights a potential mechanism by which cyclin F interacts with p62, the receptor responsible for transporting ubiquitylated substrates for autophagic degradation. These findings demonstrate that ALS/FTD-causing mutant cyclin FS621G disrupts Lys48-specific ubiquitylation, leading to accumulation of substrates and defects in the autophagic machinery. This study also demonstrates that a single missense mutation in cyclin F causes hyper-ubiquitylation of proteins that can indirectly impair the autophagy degradation pathway, which is implicated in ALS pathogenesis.

KEYWORDS:

Amyotrophic lateral sclerosis; CCNF; Cyclin F; Frontotemporal dementia; Motor neuron disease; Phosphorylation; Ubiquitylation

PMID:
28852778
DOI:
10.1007/s00018-017-2632-8
[Indexed for MEDLINE]

Supplemental Content

Full text links

Icon for Springer
Loading ...
Support Center