TY - JOUR T1 - Molecular characterization of latent GDF8 reveals mechanisms of activation JF - bioRxiv DO - 10.1101/155614 SP - 155614 AU - Ryan G. Walker AU - Jason C. McCoy AU - Magdalena Czepnik AU - Melanie J. Mills AU - Adam Hagg AU - Kelly L. Walton AU - Thomas Cotton AU - Marko Hyvönen AU - Richard T. Lee AU - Paul Gregorevic AU - Craig A. Harrison AU - Thomas B. Thompson Y1 - 2017/01/01 UR - http://biorxiv.org/content/early/2017/07/28/155614.abstract N2 - 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- and more similar to the ‘open’ state of Activin A and BMP9 (non-latent complexes). We determined that GDFβ8 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 to wild-type GDF8. Collectively, these results help characterize the latency and activation mechanisms of GDF8. ER -