Identification of Receptors and Signaling Pathways for Orphan Bone Morphogenetic Protein/Growth Differentiation Factor Ligands Based on Genomic Analyses

• Published in: The Journal of biological chemistry 2005-09, Vol.280 (37), p.32122-32132
• Main Authors: Mazerbourg, Sabine, Sangkuhl, Katrin, Luo, Ching-Wei, Sudo, Satoko, Klein, Cynthia, Hsueh, Aaron J.W.
• Format: Article
• Language: English
• Subjects: 3T3 Cells; Animals; Base Sequence; Blotting, Western; Bone Morphogenetic Proteins - chemistry; Bone Morphogenetic Proteins - genetics; Bone Morphogenetic Proteins - metabolism; Cell Differentiation; Cell Line; Cell Proliferation; COS Cells; Cysteine - chemistry; Dimerization; DNA, Complementary - metabolism; Dose-Response Relationship, Drug; Evolution, Molecular; Genes, Reporter; Genomics - methods; Growth Differentiation Factor 6; Growth Differentiation Factors; Humans; Ligands; Mice; Molecular Sequence Data; Oligonucleotides - chemistry; Oligonucleotides, Antisense - chemistry; Peptides - chemistry; Phylogeny; Plasmids - metabolism; Recombinant Proteins - chemistry; Reverse Transcriptase Polymerase Chain Reaction; RNA - metabolism; RNA Interference; Signal Transduction; Transfection
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M504629200

There are more than 30 human transforming growth factor β/bone morphogenetic protein/growth differentiation factor (TGFβ/BMP/GDF)-related ligands known to be important during embryonic development, organogenesis, bone formation, reproduction, and other physiological processes. Although select TGFβ/BMP/GDF proteins were found to interact with type II and type I serine/threonine receptors to activate downstream Smad and other proteins, the receptors and signaling pathways for one-third of these TGFβ/BMP/GDF paralogs are still unclear. Based on a genomic analysis of the entire repertoire of TGFβ/BMP/GDF ligands and serine/threonine kinase receptors, we tested the ability of three orphan BMP/GDF ligands to activate a limited number of phylogenetically related receptors. We characterized the dimeric nature of recombinant GDF6 (also known as BMP13), GDF7 (also known as BMP12), and BMP10. We demonstrated their bioactivities based on the activation of Smad1/5/8-, but not Smad2/3-, responsive promoter constructs in the MC3T3 cell line. Furthermore, we showed their ability to induce the phosphorylation of Smad1, but not Smad2, in these cells. In COS7 cells transfected with the seven known type I receptors, overexpression of ALK3 or ALK6 conferred ligand signaling by GDF6, GDF7, and BMP10. In contrast, transfection of MC3T3 cells with ALK3 small hairpin RNA suppressed Smad signaling induced by all three ligands. Based on the coevolution of ligands and receptors, we also tested the role of BMPRII and ActRIIA as the type II receptor candidates for the three orphan ligands. We found that transfection of small hairpin RNA for BMPRII and ActRIIA in MC3T3 cells suppressed the signaling of GDF6, GDF7, and BMP10. Thus, the present approach provides a genomic paradigm for matching paralogous polypeptide ligands with a limited number of evolutionarily related receptors capable of activating specific downstream Smad proteins.