Bone Morphogenetic Protein-9

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Bone morphogenetic proteins (BMPs), a subset of the transforming growth factor (TGF)-␤ superfamily, regulate a diverse array of cellular functions during development and in the adult. BMP-9 (also known as growth and differentiation factor (GDF)-2) potently induces osteogenesis and chondrogenesis, has been implicated in the differentiation of cholinergic neurons, and may help regulate glucose metabolism. We have determined the structure of BMP-9 to 2.3 Å and examined the differences between our model and existing crystal structures of other BMPs, both in isolation and in complex with their receptors. TGF-␤ ligands are translated as precursors, with pro-regions that generally dissociate after cleavage from the ligand, but in some cases (including GDF-8 and TGF-␤1, -2, and -3), the pro-region remains associated after secretion from the cell and inhibits binding of the ligand to its receptor. Although the proregion of BMP-9 remains tightly associated after secretion, we find, in several cell-based assays, that the activities of BMP-9 and BMP-9⅐pro-region complex were equivalent. Activin receptor-like kinase 1 (ALK-1), an orphan receptor in the TGF-␤ family, was also identified as a potential receptor for BMP-9 based on surface plasmon resonance studies (BIAcore) and the ability of soluble ALK-1 to block the activity of BMP-9⅐pro-region complex in cell-based assays.Transforming growth factor ␤ (TGF-␤) 1 signaling controls a wide variety of processes over the lifetime of an organism. A subset of this large and well conserved family is the group of bone morphogenetic proteins (BMPs) and growth and differentiation factors (GDFs), which regulate a diverse array of cellular functions, including differentiation, proliferation, organogenesis, axon guidance, apoptosis, and the establishment of left-right asymmetry (1-3). BMPs and GDFs are highly conserved throughout the animal kingdom, with examples ranging from Drosophila to humans. They have frequently been implicated in the treatment of bone disorders and injury, in accordance with their robust ability to generate de novo bone formation.All TGF-␤ ligands are translated as precursor proteins, consisting of an amino-terminal pro-region and a carboxyl-terminal ligand. This precursor forms a disulfide-linked homodimer in the cytoplasm, and the pro-region is then cleaved from the ligand. In most cases, the pro-region disassociates, and the mature ligand is secreted from the cell, but the pro-regions of GDF-8 (also known as myostatin) and TGF-␤1, -2, and -3 remain noncovalently associated with the ligand after secretion and inhibit binding of their ligands to their respective receptors (4 -6). Transgenic mice overexpressing the pro-region of GDF-8 show dramatic increases in muscle mass, further indicating that the pro-region functionally inhibits GDF-8 (7). The proregion of BMP-9 also remains tightly associated after secretion from the cell.BMP signaling is induced when a dimeric ligand binds to the extracellular domains of two type I and two type II receptors (8). This assembl...

mentioning

confidence: 89%

Crystal Structure of BMP-9 and Functional Interactions with Pro-region and Receptors

Brown

Zhao

Baker

et al. 2005

274

276

“…Using this sending cell-free system, we demonstrated that DALLY slows down the degradation rate of DPP protein in the receiving cells. Given that receptor-mediated endocytosis is a major route for BMP degradation (34,35), association with The sending cells were transfected with the indicated amount of dpp cDNA (ng) with or without dally. After co-culture with the receiving cells expressing Mad-FLAG, levels of pMAD and MAD-FLAG were analyzed by immunoblotting using anti-pMAD and anti-FLAG antibodies, respectively.…”

Section: Discussionmentioning

confidence: 99%

Novel Contact-dependent Bone Morphogenetic Protein (BMP) Signaling Mediated by Heparan Sulfate Proteoglycans

Dejima

Kanai

Akiyama

et al. 2011

We previously proposed a model that DALLY, a Drosophila glypican, acts as a trans co-receptor to regulate BMP signaling in the germ line stem cell niche. To investigate the molecular mechanisms of contact-dependent BMP signaling, we developed novel in vitro assay systems to monitor trans signaling using Drosophila S2 cells. Using immunoblot-based as well as single-cell assay systems, we present evidence that Drosophila glypicans indeed enhance BMP signaling in trans in a contactdependent manner in vitro. Our analysis showed that heparan sulfate modification is required for the trans co-receptor activity of DALLY. Two BMP-like molecules, Decapentaplegic (DPP) and Glass bottom boat, can mediate trans signaling through a heparan sulfate proteoglycan co-receptor in S2 cells. The in vitro systems reflect the molecular characteristics of heparan sulfate proteoglycan functions observed previously in vivo, such as ligand specificity and biphasic activity dependent on the ligand dosage. In addition, experiments using a DALLY-coated surface suggested that DALLY regulates DPP signaling in trans by its effect on the stability of DPP protein on the surface of the contacting cells. Our findings provide the molecular foundation for novel contact-dependent signaling, which defines the physical space of the stem cell niche in vivo. Bone morphogenetic proteins (BMPs)2 play critical roles in cell-cell communication during animal development. Remarkably, these molecules mediate both long and short range signaling dependent on context. For example, Decapentaplegic (DPP), a Drosophila homologue of BMPs, acts as a long range morphogen in the developing wing and as a contact-dependent niche factor in the female germ line stem cell (GSC) niche. The molecular basis underlying this differential activity of BMPs is not fully understood.Signaling and distribution of BMPs in a tissue are modulated by a class of carbohydrate-modified molecules, heparan sulfate proteoglycans (HSPGs) (1-3). In addition to BMPs, HSPGs serve as co-receptors for a number of other growth factors and morphogens, including FGF, WNT, and Hedgehog (4). HSPGs generally are thought to regulate growth factor signaling on the surface of the signal-receiving cells (5). It has been reported, however, that HSPGs can regulate signaling in trans from neighboring cells in some cases (6, 7).Recent studies demonstrated that HSPGs are essential regulators of the GSC niche in the Drosophila ovary (8, 9). Although it has been well established that DPP regulates the asymmetric division of a GSC (10), the mechanism by which this secreted molecule differentially regulates two daughter cells has been a mystery. We have found previously that DALLY, a Drosophila HSPG of the glypican type, is expressed specifically in the somatic niche cells (the cap cells) contacting GSCs and is required for GSC maintenance (8). Ectopic dally expression in somatic cells in a wide region of the germarium was sufficient to maintain all the contacting germ line cells as GSC-like undifferentiated cells, thus e...

“…BMP9 is highly expressed in the developing mouse liver, and recombinant human BMP9 stimulates hepatocyte proliferation (22,23). BMP9 has been shown to be a potent synergistic factor for hematopoietic progenitor-cell generation and colony formation and may play a role in the induction and maintenance of the neuronal cholinergic phenotype in the central nervous system (24).…”

Section: Mesenchymal Stem Cells (Mscs)mentioning

confidence: 99%

Hey1 Basic Helix-Loop-Helix Protein Plays an Important Role in Mediating BMP9-induced Osteogenic Differentiation of Mesenchymal Progenitor Cells

Sharff

Song

Luο

et al. 2009

163

260

Pluripotent mesenchymal stem cells (MSCs) are bone marrow stromal progenitor cells that can differentiate into osteogenic, chondrogenic, adipogenic, and myogenic lineages. We previously demonstrated that bone morphogenetic protein (BMP) 9 is one of the most potent and yet least characterized BMPs that are able to induce osteogenic differentiation of MSCs both in vitro and in vivo. Here, we conducted gene expression-profiling analysis and identified that Hey1 of the hairy/Enhancer of splitrelated repressor protein basic helix-loop-helix family was among the most significantly up-regulated early targets in BMP9-stimulated MSCs. We demonstrated that Hey1 expression was up-regulated at the immediate early stage of BMP9-induced osteogenic differentiation. Chromatin immunoprecipitation analysis indicated that Hey1 may be a direct target of the BMP9-induced Smad signaling pathway. Silencing Hey1 expression diminished BMP9-induced osteogenic differentiation both in vitro and in vivo and led to chondrogenic differentiation. Likewise, constitutive Hey1 expression augmented BMP9-mediated bone matrix mineralization. Hey1 and Runx2 were shown to act synergistically in BMP9-induced osteogenic differentiation, and Runx2 expression significantly decreased in the absence of Hey1, suggesting that Runx2 may function downstream of Hey1. Accordingly, the defective osteogenic differentiation caused by Hey1 knockdown was rescued by exogenous Runx2 expression. Thus, our findings suggest that Hey1, through its interplay with Runx2, may play an important role in regulating BMP9-induced osteoblast lineage differentiation of MSCs. Mesenchymal stem cells (MSCs)5 represent a very small fraction of the total population of nucleated cells in bone marrow (1) and are adherent multipotent marrow stromal cells (1-6). Although primarily located within the bone marrow compartment (5, 7, 8), MSCs have been isolated from periosteum, trabecular bone, adipose tissue, synovium, skeletal muscle, and deciduous teeth (9). As members of the transforming growth factor-␤ superfamily, BMPs play an important role in stem cell biology (10, 11) and regulate cell proliferation and differentiation during development (12, 13). Several BMPs have been shown to regulate osteoblast differentiation and subsequent bone formation (12-15). Genetic disruptions of BMPs result in various skeletal and extraskeletal abnormalities during development (14, 16). We have recently conducted a comprehensive analysis of the osteogenic activity of 14 human BMPs and demonstrated that BMP9 is one of the most potent BMPs promoting osteogenic differentiation of MSCs both in vitro and in vivo (17,18). We also demonstrated that osteogenic BMPs regulate a distinct set of downstream targets in MSCs (6,[19][20][21].BMP9 (also known as GDF2) was originally identified from fetal mouse liver cDNA libraries and is a relatively uncharacterized member of the BMP family. BMP9 is highly expressed in the developing mouse liver, and recombinant human BMP9 stimulates hepatocyte proliferation (22,23). BMP9 ha...