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Proc Natl Acad Sci U S A. 2018 Jan 30;115(5):E866-E875. doi: 10.1073/pnas.1714622115. Epub 2018 Jan 18.

Molecular characterization of latent GDF8 reveals mechanisms of activation.

Author information

1
Department of Molecular Genetics, Biochemistry, and Microbiology, University of Cincinnati, Cincinnati, OH 45267.
2
Harvard Stem Cell Institute, Harvard University, Cambridge, MA 02138.
3
Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, MA 02138.
4
Biomedicine Discovery Institute, Department of Physiology, Monash University, Clayton, VIC 3800, Australia.
5
Baker Heart and Diabetes Institute, Melbourne, VIC 3004, Australia.
6
Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, United Kingdom.
7
Department of Biochemistry and Molecular Biology, Monash University, Clayton, VIC 3800, Australia.
8
Department of Physiology, University of Melbourne, Parkville, VIC 3010, Australia.
9
Department of Neurology, University of Washington School of Medicine, Seattle, WA 98195.
10
Biomedicine Discovery Institute, Department of Physiology, Monash University, Clayton, VIC 3800, Australia; craig.harrison@monash.edu tom.thompson@uc.edu.
11
Hudson Institute of Medical Research, Clayton, VIC 3168, Australia.
12
Department of Molecular Genetics, Biochemistry, and Microbiology, University of Cincinnati, Cincinnati, OH 45267; craig.harrison@monash.edu tom.thompson@uc.edu.

Abstract

Growth/differentiation factor 8 (GDF8), or myostatin, negatively regulates muscle mass. GDF8 is held in a latent state through interactions with its N-terminal prodomain, much like TGF-β. Using a combination of small-angle X-ray scattering and mutagenesis, we characterized the interactions of GDF8 with its prodomain. Our results show that the prodomain:GDF8 complex can exist in a fully latent state and an activated or "triggered" state where the prodomain remains in complex with the mature domain. However, these states are not reversible, indicating the latent GDF8 is "spring-loaded." Structural analysis shows that the prodomain:GDF8 complex adopts an "open" configuration, distinct from the latency state of TGF-β and more similar to the open state of Activin A and BMP9 (nonlatent complexes). We determined that GDF8 maintains similar features for latency, including the alpha-1 helix and fastener elements, and identified a series of mutations in the prodomain of GDF8 that alleviate latency, including I56E, which does not require activation by the protease Tolloid. In vivo, active GDF8 variants were potent negative regulators of muscle mass, compared with WT GDF8. Collectively, these results help characterize the latency and activation mechanisms of GDF8.

KEYWORDS:

GDF8; GDF8 prodomain; latent activation; myostatin activation; myostatin prodomain

PMID:
29348202
PMCID:
PMC5798348
DOI:
10.1073/pnas.1714622115
[Indexed for MEDLINE]
Free PMC Article

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