Site-specific phosphorylation and caspase cleavage of GFAP are new markers of Alexander Disease severity
- University of North Carolina at Chapel Hill, United States
- Thermo Fisher Scientific, United States
- Durham University, United Kingdom
- Columbia University, United States
- National Tsing Hua University, Taiwan, Republic of China
- Mie University Graduate School of Medicine, Japan
Abstract
Alexander Disease (AxD) is a fatal neurodegenerative disorder caused by mutations in glial fibrillary acidic protein (GFAP), which supports the structural integrity of astrocytes. Over 70 GFAP missense mutations cause AxD, but the mechanism linking different mutations to disease-relevant phenotypes remains unknown. We used AxD patient brain tissue and induced pluripotent stem cell (iPSC)-derived astrocytes to investigate the hypothesis that AxD-causing mutations perturb key post-translational modifications (PTMs) on GFAP. Our findings reveal selective phosphorylation of GFAP-Ser13 in patients who died young, independently of the mutation they carried. AxD iPSC-astrocytes accumulated pSer13-GFAP in cytoplasmic aggregates within deep nuclear invaginations, resembling the hallmark Rosenthal fibers observed in vivo. Ser13 phosphorylation facilitated GFAP aggregation and was associated with increased GFAP proteolysis by caspase-6. Furthermore, caspase-6 was selectively expressed in young AxD patients, and correlated with the presence of cleaved GFAP. We reveal a novel PTM signature linking different GFAP mutations in infantile AxD.
Data availability
All data generated or analyzed during this study are included in the manuscript and supporting files. Source data files have been provided for mass spec results in Figure 1 and Supplemental Figure 6.
Article and author information
Author details
Roy Andrew Quinlan
Funding
Elise's Corner Fund (Research Grant)
- Natasha T Snider
United Leukodystrophy Foundation (Research Grant)
- Natasha T Snider
National Science Foundation (Graduate Research Fellowship)
- Rachel A Battaglia
University of North Carolina at Chapel Hill (Department of Cell Biology and Physiology)
- Natasha T Snider
National Institutes of Health (P30 CA016086)
- Victoria J Madden
The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.
Copyright
© 2019, Battaglia et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Site-specific phosphorylation and caspase cleavage of GFAP are new markers of Alexander Disease severity
eLife 8:e47789.
https://doi.org/10.7554/eLife.47789
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