The BMP7/ActRII Extracellular Domain Complex Provides New Insights into the Cooperative Nature of Receptor Assembly

Greenwald, Jason; Groppe, Jay C.; Gray, Peter C.; Wiater, Ezra; Kwiatkowski, Witek; Vale, Wylie; Choe, Senyon

doi:10.1016/s1097-2765(03)00094-7

Cited by 249 publications

(303 citation statements)

References 59 publications

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“…The complex structure of BMP-7 dimer bound to the ActRII-ECD shows that the ActRII-ECD makes contact with only one of the dimer subunits (23). The binding interface revealed by the x-ray structure agrees with the binding affinities available for mutants of ActRII (24), activin-A (25,26), and BMP-2 (27).…”

supporting

confidence: 54%

Identification of a Functional Binding Site for Activin on the Type I Receptor ALK4

Harrison¹,

Gray²,

Koerber

et al. 2003

Journal of Biological Chemistry

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Activins, like other members of the transforming growth factor-␤ (TGF-␤) superfamily, initiate signaling by assembling a complex of two types of transmembrane serine/threonine receptor kinases classified as type II (ActRII or ActRIIB) and type I (ALK4). A kinase-deleted version of ALK4 can form an inactive complex with activin and ActRII/IIB and thereby acts in a dominant negative manner to block activin signaling. Using the complex structure of bone morphogenetic protein-2 bound to its type I receptor (ALK3) as a guide, we introduced extracellular domain mutations in the context of the truncated ALK4 (ALK4-trunc) construct and assessed the ability of the mutants to inhibit activin function. We have identified five hydrophobic amino acid residues on the ALK4 extracellular domain (Leu 40 , Ile 70 , Val 73 , Leu 75 , and Pro 77 ) that, when mutated to alanine, have substantial effects on ALK4-trunc dominant negative activity. In addition, eleven mutants partially affected activin binding to ALK4. Together, these residues likely constitute the binding surface for activin on ALK4. Cross-linking studies measuring binding of 125 Iactivin-A to the ALK4-trunc mutants in the presence of ActRII implicated the same residues. Our results indicate that there is only a partial overlap of the binding sites on ALK4 and ALK3 for activin-A and bone morphogenetic protein-2, respectively. In addition three of the residues required for activin binding to ALK4 are conserved on the type I TGF-␤ receptor ALK5, suggesting the corresponding region on ALK5 may be important for TGF-␤ binding.Activins are members of the transforming growth factor-␤ (TGF-␤) 1 superfamily, which also includes the TGF-␤ (1) and bone morphogenetic protein (BMP) (2) families. These structurally related but functionally diverse polypeptides control the growth and differentiation of many cell types (3-5). In addition, activins regulate the production of follicle-stimulating hormone and other hormones by the anterior pituitary (6 -8) and have diverse endocrine, paracrine, and autocrine actions throughout the reproductive (9), immune (10, 11), hematopoietic (12, 13), endocrine (7), and central nervous systems (14). Activins also play key roles in numerous pathophysiologic processes including carcinogenesis (15). Activins (ϳ26 kDa) are disulfide-linked dimers of related polypeptides consisting of two ␤ chains (activin-A (␤A-␤A), activin-AB (␤A-␤B), and activin-B (␤B-␤B)) (16). The structure of these factors is determined by several conserved cysteine residues that form disulfide bonds in the tightly folded cystine-knot motif that is shared by TGF-␤ superfamily members (17).The signaling events initiated by activin require binding of two types of transmembrane serine/threonine receptor kinases classified as type II (ActRII or ActRIIB) and type I (ALK4). Both receptors are transmembrane proteins with ligand binding activity in the extracellular domain and serine/threonine kinase activity in the intracellular domain (15). The activin type II receptors are the primary li...

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supporting

confidence: 54%

Identification of a Functional Binding Site for Activin on the Type I Receptor ALK4

Harrison¹,

Gray²,

Koerber

et al. 2003

Journal of Biological Chemistry

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“…The high resolution crystal structures of TGF-␤2 (21,22), TGF-␤3 (23), and more recently, the soluble ECD of the type II receptor (24), and the complex of the ECD-T␤RII and TGF-␤3 (25) have been solved, in addition to those of the BMPR1A⅐BMP2 (26) and ActRII⅐BMP7 complexes (27). In aggregate, these studies suggest that TGF-␤ receptor and ligand interactions may involve a cooperative model of binding with direct protein-protein contact between the type II and type I receptors as part of the assembly process, whereas the BMP/ActRII and BMP ligands may utilize an allosteric model of binding in which the type II and type I receptors do not necessarily make contact with each other.…”

Section: Discussionmentioning

confidence: 99%

“…In addition, the extracellular domain of T␤RII alone (24), and in complex with TGF-␤3 (25), have also been crystallized. These structures yield qualitatively different information than the crystal structure of the BMP type IA receptor (BMPR1A)⅐ BMP-2 complex (26) and the activin type II receptor (ActRII)⅐ BMP-7 complex (27). In aggregate, these studies suggest that the TGF-␤ receptor and ligand interactions may involve a cooperative model of binding in which the extracellular domains of the type II and type I receptors make physical contact, whereas the BMP/ActRII and BMP ligands may utilize an allosteric model of binding in which the extracellular domains of the type II and type I receptors do not interact.…”

mentioning

confidence: 98%

In the Absence of Type III Receptor, the Transforming Growth Factor (TGF)-β Type II-B Receptor Requires the Type I Receptor to Bind TGF-β2

Babitt

Pirani

et al. 2004

Journal of Biological Chemistry

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Transforming growth factor ␤ (TGF-␤) ligands exert their biological effects through type II (T␤RII) and type I receptors (T␤RI). Unlike TGF-␤1 and -␤3, TGF-␤2 appears to require the co-receptor betaglycan (type III receptor, T␤RIII) for high affinity binding and signaling. Recently, the T␤RIII null mouse was generated and revealed significant non-overlapping phenotypes with the TGF-␤2 null mouse, implying the existence of T␤RIII independent mechanisms for TGF-␤2 signaling. Because a variant of the type II receptor, the type II-B receptor (T␤RII-B), has been suggested to mediate TGF-␤2 signaling in the absence of T␤RIII, we directly tested the ability of T␤RII-B to bind TGF-␤2. Here we show that the soluble extracellular domain of the type II-B receptor (sT␤RII-B.Fc) bound TGF-␤1 and TGF-␤3 with high affinity (K d values ‫؍‬ 31.7 ؎ 22.8 and 74.6 ؎ 15.8 pM, respectively), but TGF-␤2 binding was undetectable at corresponding doses. Similar results were obtained for the soluble type II receptor (sT␤RII.Fc). However, sT␤RII.Fc or sT␤RII-B.Fc in combination with soluble type I receptor (sT␤RI.Fc) formed a high affinity complex that bound TGF-␤2, and this complex inhibited TGF-␤2 in a biological inhibition assay. These results show that TGF-␤2 has the potential to signal in the absence of T␤RIII when sufficient TGF-␤2, T␤RI, and T␤RII or T␤RII-B are present. Our data also support a cooperative model for receptor-ligand interactions, as has been suggested by crystallization studies of TGF-␤ receptors and ligands. Our cell-free binding assay system will allow for testing of models of receptor-ligand complexes prior to actual solution of crystal structures.Transforming growth factor-␤ (TGF-␤) 1 represents a large superfamily of dimeric growth factors that include the TGF-␤s, inhibins, activins, Mullerian inhibiting substance, growth and differentiation factors, and bone morphogenetic proteins (BMPs) in mammals (1, 2). These cytokines play important roles in an array of processes such as growth, differentiation, and development (3). There are three TGF-␤ isoforms that share a high degree of homology and overlapping biological activities (4). However, distinct expression patterns and unique, isoform-specific phenotypes of the corresponding knockout mice demonstrate significant non-redundancy of TGF-␤ function (5-9).TGF-␤s exert their biological effects through three cell surface receptors designated as type I, II, and III (T␤RI, T␤RII, and T␤RIII) (2), all of which have been cloned (10 -13). In addition, the type II-B receptor (T␤RII-B), an alternatively spliced isoform of T␤RII containing an insert of 26 amino acids replacing Val 51 , has also been identified (14 -16). Type I and type II receptors have intracellular serine/threonine kinase domains, whereas the type III receptor has only a short intracellular domain. On binding of TGF-␤ ligands, constitutively active type II receptors recruit and phosphorylate type I receptors; the activated type I receptor kinase then interacts with and phosphorylates downstream signaling ...

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“…The solved crystal structures of BMP2 and BMP7 with their receptors have provided the basis of receptor binding to BMP ligands (37)(38)(39). Two epitopes are involved in the binding of BMPs to their receptors ( Supplementary Fig.…”

Section: Epitope Binningmentioning

confidence: 99%

Effective Inhibition of Bone Morphogenetic Protein Function by Highly Specific Llama-Derived Antibodies

Calpe

Wagner

Khattabi³

et al. 2015

Molecular Cancer Therapeutics

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Bone morphogenetic proteins (BMP) have important but distinct roles in tissue homeostasis and disease, including carcinogenesis and tumor progression. A large number of BMP inhibitors are available to study BMP function; however, as most of these antagonists are promiscuous, evaluating specific effects of individual BMPs is not feasible. Because the oncogenic role of the different BMPs varies for each neoplasm, highly selective BMP inhibitors are required. Here, we describe the generation of three types of llama-derived heavy chain variable domains (VHH) that selectively bind to either BMP4, to BMP2 and 4, or to BMP2, 4, 5, and 6. These generated VHHs have high affinity to their targets and are able to inhibit BMP signaling. Epitope binning and docking modeling have shed light into the basis for their BMP specificity. As opposed to the wide structural reach of natural inhibitors, these small molecules target the grooves and pockets of BMPs involved in receptor binding. In organoid experiments, specific inhibition of BMP4 does not affect the activation of normal stem cells. Furthermore, in vitro inhibition of cancer-derived BMP4 noncanonical signals results in an increase of chemosensitivity in a colorectal cancer cell line. Therefore, because of their high specificity and low off-target effects, these VHHs could represent a therapeutic alternative for BMP4 þ malignancies.

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The BMP7/ActRII Extracellular Domain Complex Provides New Insights into the Cooperative Nature of Receptor Assembly

Cited by 249 publications

References 59 publications

Identification of a Functional Binding Site for Activin on the Type I Receptor ALK4

Identification of a Functional Binding Site for Activin on the Type I Receptor ALK4

In the Absence of Type III Receptor, the Transforming Growth Factor (TGF)-β Type II-B Receptor Requires the Type I Receptor to Bind TGF-β2

Effective Inhibition of Bone Morphogenetic Protein Function by Highly Specific Llama-Derived Antibodies

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