prodomain of BMP4 is necessary and sufficient to generate stable BMP4/7 heterodimers with enhanced bioactivity in vivo

• Published in: Proceedings of the National Academy of Sciences - PNAS 2015-05, Vol.112 (18), p.E2307-E2316
• Main Authors: Neugebauer, Judith M., Kwon, Sunjong, Kim, Hyung-Seok, Donley, Nathan, Tilak, Anup, Sopory, Shailaja, Christian, Jan L.
• Format: Article
• Language: English
• Subjects: Animals; Biological activity; Biological Sciences; Bone Morphogenetic Protein 4 - chemistry; Bone Morphogenetic Protein 7 - chemistry; Embryonic growth stage; Epitopes - chemistry; Gene Expression Regulation, Developmental; Genetics; HEK293 Cells; Homeostasis; Humans; Ligands; Mice; PNAS Plus; Protein Binding; Protein Multimerization; Protein Structure, Tertiary; Proteins; Recombinant Proteins - chemistry; Signal Transduction; Xenopus
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1501449112

Significance Bone morphogenetic proteins (BMPs) are made as inactive precursor proteins that dimerize and are cleaved to generate a bioactive ligand along with prodomain fragments that lack signaling activity. BMP ligands signal as either homodimers, or as heterodimers that display significantly higher activity in vivo. Recombinant homodimeric BMP ligands are used clinically to stimulate bone healing, but this requires supraphysiological doses due to the short half-life of the implanted protein. The current studies demonstrate that properties intrinsic to the BMP4 prodomain contribute to the formation and activity of BMP homodimers and heterodimers in vivo. Understanding how the prodomain regulates the activity of the ligand when it is made in vivo may lead to changes in the way BMP ligands are used clinically. Bone morphogenetic proteins 4 and 7 (BMP4 and BMP7) are morphogens that signal as either homodimers or heterodimers to regulate embryonic development and adult homeostasis. BMP4/7 heterodimers exhibit markedly higher signaling activity than either homodimer, but the mechanism underlying the enhanced activity is unknown. BMPs are synthesized as inactive precursors that dimerize and are then cleaved to generate both the bioactive ligand and prodomain fragments, which lack signaling activity. Our study reveals a previously unknown requirement for the BMP4 prodomain in promoting heterodimer activity. We show that BMP4 and BMP7 precursor proteins preferentially or exclusively form heterodimers when coexpressed in vivo. In addition, we show that the BMP4 prodomain is both necessary and sufficient for generation of stable heterodimeric ligands with enhanced activity and can enable homodimers to signal in a context in which they normally lack activity. Our results suggest that intrinsic properties of the BMP4 prodomain contribute to the relative bioactivities of homodimers versus heterodimers in vivo. These findings have clinical implications for the use of BMPs as regenerative agents for the treatment of bone injury and disease.