Tolloid cleavage activates latent GDF8 by priming the pro‐complex for dissociation. (18th January 2018)

• Record Type: Journal Article
• Authors: Le, Viet Q; Iacob, Roxana E; Tian, Yuan; McConaughy, William; Jackson, Justin; Su, Yang; Zhao, Bo; Engen, John R; Pirruccello‐Straub, Michelle; Springer, Timothy A
• Is Part Of: EMBO journal. Volume 37:Number 3(2018)
• Page Start: 384
• Page End: 397
• Publication Date: 2018-01-18
• Subjects: conformational dynamics -- growth factor activation -- myostatin -- prodomain -- TGF‐β; Molecular biology -- Periodicals; 572.805
• DOI: 10.15252/embj.201797931
• Languages: English
• ISSNs: 0261-4189

Abstract

Abstract: Growth differentiation factor 8 (GDF8)/myostatin is a latent TGF‐β family member that potently inhibits skeletal muscle growth. Here, we compared the conformation and dynamics of precursor, latent, and Tolloid‐cleaved GDF8 pro‐complexes to understand structural mechanisms underlying latency and activation of GDF8. Negative stain electron microscopy (EM) of precursor and latent pro‐complexes reveals a V‐shaped conformation that is unaltered by furin cleavage and sharply contrasts with the ring‐like, cross‐armed conformation of latent TGF‐β1. Surprisingly, Tolloid‐cleaved GDF8 does not immediately dissociate, but in EM exhibits structural heterogeneity consistent with partial dissociation. Hydrogen–deuterium exchange was not affected by furin cleavage. In contrast, Tolloid cleavage, in the absence of prodomain–growth factor dissociation, increased exchange in regions that correspond in pro‐TGF‐β1 to the α1‐helix, latency lasso, and β1‐strand in the prodomain and to the β6′‐ and β7′‐strands in the growth factor. Thus, these regions are important in maintaining GDF8 latency. Our results show that Tolloid cleavage activates latent GDF8 by destabilizing specific prodomain–growth factor interfaces and primes the growth factor for release from the prodomain. Synopsis: Comparison of conformation and dynamics between precursor, furin‐cleaved (latent), and Tolloid‐cleaved pro‐complexes of the muscle mass regulator GDF8/myostatin show how Tolloid cleavage destabilizes prodomain/growth factor interfaces that mediate latency, thus priming the pro‐complex for dissociation. Negative‐stain electron microscopy shows that precursor and latent GDF8 pro‐complexes adopt a V‐shaped, open‐armed conformation, indicating that furin cleavage does not alter pro‐complex conformation. Tolloid cleavage (i.e. activation) does not immediately dissociate the GDF8 pro‐complex, but induces structural heterogeneity consistent with partial dissociation. Hydrogen‐deuterium exchange experiments show that Tolloid cleavage increases structural dynamics of the α1‐helix, latency lasso, and β1 strand in the prodomain and of the β6′‐7′ strands in the growth factor, underscoring their importance in latency of GDF8. Abstract : Structural and dynamics analysis shows that Tolloid cleavage destabilizes the precursor of the muscle mass regulator myostatin/GDF8 to promote release of mature growth factor.