Pathogenic mutation in the ALS/FTD gene, CCNF, causes elevated Lys48-linked ubiquitylation and defective autophagy.
- Authors
- Lee, A., Rayner, S.L., Gwee, S.S.L., De Luca, A., Shahheydari, H., Sundaramoorthy, V., Ragagnin, A., Morsch, M., Radford, R., Galper, J., Freckleton, S., Shi, B., Walker, A.K., Don, E.K., Cole, N.J., Yang, S., Williams, K.L., Yerbury, J.J., Blair, I.P., Atkin, J.D., Molloy, M.P., Chung, R.S.
- ID
- ZDB-PUB-170922-17
- Date
- 2017
- Source
- Cellular and molecular life sciences : CMLS 75(2): 335-354 (Journal)
- Registered Authors
- Chung, Roger, Cole, Nicholas, Don, Emily, Morsch, Marco
- Keywords
- Amyotrophic lateral sclerosis, CCNF, Cyclin F, Frontotemporal dementia, Motor neuron disease, Phosphorylation, Ubiquitylation
- MeSH Terms
-
- Amyotrophic Lateral Sclerosis/complications
- Amyotrophic Lateral Sclerosis/genetics*
- Autophagy/genetics*
- Cells, Cultured
- Cyclins/genetics*
- Frontotemporal Dementia/complications
- Frontotemporal Dementia/genetics*
- HEK293 Cells
- Humans
- Lysine/metabolism
- Mutation, Missense/physiology
- Ubiquitination/genetics*
- PubMed
- 28852778 Full text @ Cell. Mol. Life Sci.
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.