title: Repulsive guidance molecule (RGM) family proteins exhibit differential binding kinetics for bone morphogenetic proteins (BMPs).
abstract: Bone morphogenetic proteins (BMPs) are members of the transforming growth factor beta superfamily that exert their effects via type I and type II serine threonine kinase receptors and the SMAD intracellular signaling pathway to regulate diverse biologic processes. Recently, we discovered that the repulsive guidance molecule (RGM) family, including RGMA, RGMB, and RGMC/hemojuvelin (HJV), function as co-receptors that enhance cellular responses to BMP ligands. Here, we use surface plasmon resonance to quantitate the binding kinetics of RGM proteins for BMP ligands. We show that among the RGMs, HJV exhibits the highest affinity for BMP6, BMP5, and BMP7 with K(D) 8.1, 17, and 20 nM respectively, versus 28, 33, and 166 nM for RGMB, and 55, 83, and 63 nM for RGMA. Conversely, RGMB exhibits preferential binding to BMP4 and BMP2 with K(D) 2.6 and 5.5 nM respectively, versus 4.5 and 9.4 nM for HJV, and 14 and 22 nM for RGMA, while RGMA exhibits the lowest binding affinity for most BMPs tested. Among the BMP ligands, RGMs exhibit the highest relative affinity for BMP4 and the lowest relative affinity for BMP7, while none of the RGMs bind to BMP9. Thus, RGMs exhibit preferential binding for distinct subsets of BMP ligands. The preferential binding of HJV for BMP6 is consistent with the functional role of HJV and BMP6 in regulating systemic iron homeostasis. Our data may help explain the mechanism by which BMPs exert cell-context specific effects via a limited number of type I and type II receptors.
authors.affiliation: Program in Anemia Signaling Research, Nephrology Division, Program in Membrane Biology, and Center for Systems Biology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, United States of America.
authors.forename: Qifang
authors.initials: Q
authors.lastname: Wu
authors.forename: Chia Chi
authors.initials: CC
authors.lastname: Sun
authors.forename: Herbert Y
authors.initials: HY
authors.lastname: Lin
authors.forename: Jodie L
authors.initials: JL
authors.lastname: Babitt
mesh_terms: D055417:Bone Morphogenetic Protein 5 / Q000737:chemistry* / Q000235:genetics; D055418:Bone Morphogenetic Protein 6 / Q000737:chemistry* / Q000235:genetics; D055419:Bone Morphogenetic Protein 7 / Q000737:chemistry* / Q000235:genetics; D015816:Cell Adhesion Molecules, Neuronal / Q000737:chemistry* / Q000235:genetics; D002460:Cell Line; D058851:GPI-Linked Proteins / Q000737:chemistry / Q000235:genetics; D017930:Genes, Reporter; D055427:Growth Differentiation Factor 2; D055412:Growth Differentiation Factors / Q000737:chemistry* / Q000235:genetics; D000071020:Hemochromatosis Protein; D015395:Histocompatibility Antigens Class I / Q000737:chemistry* / Q000235:genetics; D006801:Humans; D007700:Kinetics; D008024:Ligands; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000737:chemistry* / Q000235:genetics; D011485:Protein Binding; D011994:Recombinant Proteins / Q000737:chemistry* / Q000235:genetics; D015398:Signal Transduction; D012996:Solutions; D014162:Transfection
chemical_list: C525814:BMP5 protein, human; C525816:BMP6 protein, human; C525819:BMP7 protein, human; D055417:Bone Morphogenetic Protein 5; D055418:Bone Morphogenetic Protein 6; D055419:Bone Morphogenetic Protein 7; D015816:Cell Adhesion Molecules, Neuronal; C525887:GDF2 protein, human; D058851:GPI-Linked Proteins; D055427:Growth Differentiation Factor 2; D055412:Growth Differentiation Factors; C103673:HFE protein, human; D000071020:Hemochromatosis Protein; D015395:Histocompatibility Antigens Class I; D008024:Ligands; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; C522183:RGMA protein, human; C560433:RGMB protein, human; D011994:Recombinant Proteins; D012996:Solutions