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Foster AD, Downing P, Figredo E, Polain N, Stott A, Layfield R, Rea SL. ALS-associated TBK1 variant p.G175S is defective in phosphorylation of p62 and impacts TBK1-mediated signalling and TDP-43 autophagic degradation. Mol Cell Neurosci 2020; 108:103539. [PMID: 32835772 DOI: 10.1016/j.mcn.2020.103539] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Revised: 08/13/2020] [Accepted: 08/14/2020] [Indexed: 12/11/2022] Open
Abstract
Mutations affecting SQSTM1 coding for p62 and TANK-Binding Kinase 1 (TBK1) have been implicated in amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). TBK1 is a serine-threonine kinase that regulates p62's activity as an autophagy receptor via phosphorylation and also has roles in neuroinflammatory signalling pathways. The mechanisms underlying ALS and FTLD pathogenesis as a result of TBK1 mutations are incompletely understood, however, loss of TBK1 function can lead to dysregulated autophagy and mitophagy. Here, we report that an ALS-associated TBK1 variant affecting the kinase domain, p.G175S, is defective in phosphorylation of p62 at Ser-403, a modification critical for regulating its ubiquitin-binding function, as well as downstream phosphorylation at Ser-349. Consistent with these findings, expression of p.G175S TBK1 was associated with decreased induction of autophagy compared to wild type and reduced degradation of the ALS-linked protein TDP-43. Expression of wild type TBK1 increased NF-κB signalling ~300 fold in comparison to empty vector cells, whereas p.G175S TBK1 was unable to promote NF-κB signalling above levels observed in empty vector transfected cells. We also noted a hitherto unknown role for TBK1 as a suppressor of oxidative stress (Nrf2) signalling and show that p.G175S TBK1 expressing cells lose this inhibitory function. Our data suggest that TBK1 ALS mutations may broadly impair p62-mediated cell signalling, which ultimately may reduce neuronal survival, in addition TDP-43 was not efficiently degraded, together these effects may contribute to TBK1 mutation associated ALS and FTLD pathogenesis.
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Affiliation(s)
- A D Foster
- Harry Perkins Institute of Medical Research, Centre for Medical Research, University of Western Australia, Nedlands, Western Australia, Australia; Department of Endocrinology and Diabetes, Sir Charles Gairdner Hospital, Nedlands, Western Australia, Australia; Perron Institute for Neurological and Translational Science, Centre for Neuromuscular and Neurological Disorders, University of Western Australia, Nedlands, Western Australia, Australia; Centre for Molecular Medicine and Innovative Therapeutics, Murdoch University, Health Research Building, Discovery Way, Murdoch, WA, Australia
| | - P Downing
- School of Health Sciences, Notre Dame University, Fremantle, Western Australia, Australia
| | - E Figredo
- School of Health Sciences, Notre Dame University, Fremantle, Western Australia, Australia
| | - N Polain
- Centre for Molecular Medicine and Innovative Therapeutics, Murdoch University, Health Research Building, Discovery Way, Murdoch, WA, Australia
| | - A Stott
- Harry Perkins Institute of Medical Research, Centre for Medical Research, University of Western Australia, Nedlands, Western Australia, Australia; Department of Endocrinology and Diabetes, Sir Charles Gairdner Hospital, Nedlands, Western Australia, Australia
| | - R Layfield
- School of Health Sciences, Notre Dame University, Fremantle, Western Australia, Australia; School of Life Sciences, University of Nottingham, Nottingham, United Kingdom
| | - S L Rea
- Harry Perkins Institute of Medical Research, Centre for Medical Research, University of Western Australia, Nedlands, Western Australia, Australia; Department of Endocrinology and Diabetes, Sir Charles Gairdner Hospital, Nedlands, Western Australia, Australia; Perron Institute for Neurological and Translational Science, Centre for Neuromuscular and Neurological Disorders, University of Western Australia, Nedlands, Western Australia, Australia; Centre for Molecular Medicine and Innovative Therapeutics, Murdoch University, Health Research Building, Discovery Way, Murdoch, WA, Australia.
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