A large bioactive BMP ligand with distinct signaling properties is produced by alternative proconvertase processing.

Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI 02912, USA.
Science Signaling (Impact Factor: 7.65). 04/2012; 5(218):ra28. DOI: 10.1126/scisignal.2002549
Source: PubMed

ABSTRACT Dimers of conventional transforming growth factor-β (TGF-β) and bone morphogenetic protein (BMP) ligands are composed of two 100- to 140-amino acid peptides that are produced through the proteolytic processing of a proprotein precursor by proconvertases, such as furin. We report the identification of an evolutionarily conserved furin processing site in the amino terminus (NS) of the Glass bottom boat (Gbb; the Drosophila ortholog of vertebrate BMP5, 6, and 7) proprotein that generates a 328-amino acid, active BMP ligand distinct from the conventional 130-amino acid ligand. Gbb38, the large ligand form of Gbb, exhibited greater signaling activity and a longer range than the shorter form Gbb15. The abundance of Gbb15 and Gbb38 varied among different tissues, raising the possibility that differential processing could account for tissue-specific behaviors of BMPs. In human populations, mutations that abolished the NS cleavage site in BMP4, BMP15, or anti-Müllerian hormone were associated with cleft lip with or without cleft palate (BMP4), premature ovarian failure (BMP15), and persistent Müllerian duct syndrome (anti-Müllerian hormone), suggesting the importance of NS processing during development. The identification of this large BMP ligand form and the functional differences between large and small ligands exemplifies the potential for differential proprotein processing to substantially affect BMP and TGF-β signaling output in different tissue and cellular contexts.

  • [Show abstract] [Hide abstract]
    ABSTRACT: The TGF-beta pathway is an evolutionarily conserved signal transduction module that mediates diverse biological processes in animals. In Drosophila, both the BMP and Activin branches are required for viability. Studies rooted in classical and molecular genetic approaches continue to uncover new developmental roles for TGF-beta signaling. We present an overview of the secreted ligands, transmembrane receptors and cellular Smad transducer proteins that comprise the core pathway in Drosophila. An assortment of tools have been developed to conduct tissue-specific loss and gain-of-function experiments for these pathway components. We discuss the deployment of these reagents, with an emphasis on appropriate usage and limitations of the available tools. Throughout, we note reagents that are in need of further improvement of development, and signaling features requiring further study. A general theme is that comparison of phenotypes for ligands, receptors, and Smads can be used to map tissue interactions, and to separate canonical and non-canonical signaling activities. Core TGF-beta signaling components are subject to multiple layers of regulation, and are coupled to context-specific inputs and outputs. In addition to fleshing out how TGF-beta signaling serves the fruit fly, we anticipate that future studies will uncover new regulatory nodes and modes and will continue to advance paradigms for how TGF-beta signaling regulates general developmental processes.
    Methods 03/2014; · 3.22 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: More than a decade has passed since the release of the Drosophila genome and the first predictions of fruit fly regulatory peptides (neuropeptides and peptide hormones). Since then, mass spectrometry-based methods have fuelled the chemical characterisation of regulatory peptides, from 7 Drosophila regulatory peptides in the pre-genomic area to around 60 today. We here review the development of fruit fly peptidomics, present a comprehensive list of the regulatory peptides that have been chemically characterised until today. We also summarise the knowledge on peptide processing in Drosophila, which has strongly profited from a combination of MS-based techniques and the genetic tools available for the fruit fly. This combination has a very high potential to study the functional biology of peptide signalling on all levels, especially with the ongoing developments in quantitative MS in Drosophila.
    EuPA Open Proteomics. 06/2014;
  • [Show abstract] [Hide abstract]
    ABSTRACT: The TGFβ family member Nodal is central to control pluripotent stem cell fate, but its use as a stem cell differentiation factor is limited by low specific activity. During development, Nodal depends on Growth and differentiation factor (Gdf)-1 and on the shared co-receptor Cryptic to specify visceral left-right axis asymmetry. We therefore asked whether the functionality of Nodal can be augmented by Gdf1. Since Nodal and Gdf1 coimmunoprecipitate each other, they were predicted to form heterodimers, possibly to facilitate diffusion or to increase the affinity for signaling receptors. Here, we report that Gdf1 suppresses an unexpected dependence of Nodal on serum proteins and that it is critically required for non-autonomous signaling in cells expressing Cryptic. Nodal, Gdf1 and their cleaved propeptides copurified as a heterodimeric low molecular weight (LMW) complex that stimulated Acvr signaling receptors far more potently than Nodal alone, also in cells expressing Cripto. Even though heterodimerization with Gdf1 did not increase binding of Nodal to Fc fusions of co-receptors or Acvr extracellular domains, it was essential for soluble Acvr2 to inhibit Nodal signaling. This implies that Gdf1 potentiates Nodal activity by stabilizing an LMW fraction that is susceptible to neutralization by soluble Acvr2. Finally, in differentiating human ES cells, endodermal markers were more efficiently induced by Nodal·Gdf1 than by Nodal, suggesting that Nodal·Gdf1 is an attractive new reagent to direct stem cell differentiation.
    Journal of Biological Chemistry 05/2014; 289(25). · 4.60 Impact Factor