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Defective recognition of LC3B by mutant SQSTM1/p62 implicates impairment of autophagy as a pathogenic mechanism in ALS-FTLD

Goode, Alice; Butler, Kevin; Long, Jed; Cavey, James; Scott, Daniel; Shaw, Barry; Sollenberger, Jill; Gell, Christopher; Johansen, Terje; Oldham, Neil J.; Searle, Mark; Layfield, Robert

Authors

Alice Goode

Kevin Butler

Jed Long

James Cavey

Barry Shaw

Jill Sollenberger

Christopher Gell

Terje Johansen

NEIL OLDHAM neil.oldham@nottingham.ac.uk
Professor of Biomolecular Spectrometry

Mark Searle



Abstract

Growing evidence implicates impairment of autophagy as a candidate pathogenic mechanism in the spectrum of neurodegenerative disorders which includes amyotrophic lateral sclerosis and frontotemporal lobar degeneration (ALS-FTLD). SQSTM1, which encodes the autophagy receptor SQSTM1/p62, is genetically associated with ALS-FTLD, although to date autophagy-relevant functional defects in disease-associated variants have not been described. A key protein-protein interaction in autophagy is the recognition of lipid-anchored ATG8/LC3 within the phagophore membrane by SQSTM1, mediated through its LC3-interacting region (LIR), and notably some ALS-FTLD mutations map to this region. Here we show that although representing a conservative substitution and predicted to be benign, the ALS-associated L341V mutation of SQSTM1 is defective in recognition of LC3B. We place our observations on a firm quantitative footing by showing the L341V-mutant LIR is associated with a ~3-fold reduction in LC3B binding affinity and using protein NMR we rationalise the structural basis for the effect. This functional deficit is realised in motor neurone-like cells, with L341V mutant EGFP-mCherry-SQSTM1 less readily incorporated into acidic autophagic vesicles than wild-type. Our data supports a model in which the L341V mutation limits the critical step of SQSTM1 recruitment to the phagophore. The oligomeric nature of SQSTM1 which presents multiple LIRs to template growth of the phagophore potentially gives rise to avidity effects which amplify the relatively modest impact of any single mutation on LC3B binding. Over the lifetime of a neurone impaired autophagy could expose a vulnerability which ultimately tips the balance from cell survival towards cell death.

Journal Article Type Article
Publication Date Jul 2, 2016
Journal Autophagy
Print ISSN 1554-8627
Electronic ISSN 1554-8635
Publisher Taylor & Francis Open
Peer Reviewed Peer Reviewed
Volume 12
Issue 7
Pages 1094-1104
APA6 Citation Goode, A., Butler, K., Long, J., Cavey, J., Scott, D., Shaw, B., …Layfield, R. (2016). Defective recognition of LC3B by mutant SQSTM1/p62 implicates impairment of autophagy as a pathogenic mechanism in ALS-FTLD. Autophagy, 12(7), 1094-1104. https://doi.org/10.1080/15548627.2016.1170257
DOI https://doi.org/10.1080/15548627.2016.1170257
Publisher URL http://www.tandfonline.com/doi/full/10.1080/15548627.2016.1170257
Copyright Statement Copyright information regarding this work can be found at the following address: http://eprints.nottingh.../end_user_agreement.pdf
Additional Information Version of Record of this manuscript has been published and is available in
Autophagy 2016, www.tandfonline.com/doi/full/10.1080/15548627.2016.1170257
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