scholarly journals Bone Morphogenetic Protein Receptor Complexes on the Surface of Live Cells: A New Oligomerization Mode for Serine/Threonine Kinase Receptors

2000 ◽  
Vol 11 (3) ◽  
pp. 1023-1035 ◽  
Author(s):  
Lilach Gilboa ◽  
Anja Nohe ◽  
Tanja Geissendörfer ◽  
Walter Sebald ◽  
Yoav I. Henis ◽  
...  
Keyword(s):  
Bone Morphogenetic Proteins ◽  
Transforming Growth Factor ◽  
Transforming Growth Factor Β ◽  
Live Cells ◽  
Type I ◽  
Serine Threonine Kinase ◽  
Threonine Kinase ◽  
Receptor Complexes ◽  
Bmp Receptors ◽  
Protein Receptor

The bone morphogenetic proteins (BMPs) play important roles in embryogenesis and normal cell growth. The BMP receptors belong to the family of serine/threonine kinase receptors, whose activation has been investigated intensively for the transforming growth factor-β (TGF-β) receptor subfamily. However, the interactions between the BMP receptors, the composition of the active receptor complex, and the role of the ligand in its formation have not yet been investigated and were usually assumed to follow the same pattern as the TGF-β receptors. Here we demonstrate that the oligomerization pattern of the BMP receptors is different and is more flexible and susceptible to modulation by ligand. Using several complementary approaches, we investigated the formation of homomeric and heteromeric complexes between the two known BMP type I receptors (BR-Ia and BR-Ib) and the BMP type II receptor (BR-II). Coimmunoprecipitation studies detected the formation of heteromeric and homomeric complexes among all the BMP receptor types even in the absence of ligand. These complexes were also detected at the cell surface after BMP-2 binding and cross-linking. Using antibody-mediated immunofluorescence copatching of epitope-tagged receptors, we provide evidence in live cells for preexisting heteromeric (BR-II/BR-Ia and BR-II/BR-Ib) and homomeric (BR-II/BR-II, BR-Ia/ BR-Ia, BR-Ib/ BR-Ib, and also BR-Ia/ BR-Ib) oligomers in the absence of ligand. BMP-2 binding significantly increased hetero- and homo-oligomerization (except for the BR-II homo-oligomer, which binds ligand poorly in the absence of BR-I). In contrast to previous observations on TGF-β receptors, which were found to be fully homodimeric in the absence of ligand, the BMP receptors show a much more flexible oligomerization pattern. This novel feature in the oligomerization mode of the BMP receptors allows higher variety and flexibility in their responses to various ligands as compared with the TGF-β receptors.

Reversible ubiquitination regulates the Smad/TGF-β signalling pathway

2006 ◽  
Vol 34 (5) ◽  
pp. 761-763 ◽  
Author(s):  
S.J. Wicks ◽  
T. Grocott ◽  
K. Haros ◽  
M. Maillard ◽  
P. ten Dijke ◽  
...  
Keyword(s):  
Transforming Growth Factor ◽  
Transforming Growth Factor Β ◽  
Type I ◽  
Serine Threonine Kinase ◽  
Full Spectrum ◽  
Threonine Kinase ◽  
Pathological Conditions ◽  
C Terminus ◽  
Β Receptor ◽  
Fine Tune

TGF-β (transforming growth factor-β) signals through serine/threonine kinase receptors and intracellular Smad transcription factors. An important regulatory step involves specific ubiquitination by Smurfs (Smad–ubiquitin regulatory factors), members of the HECT (homologous to E6-associated protein C-terminus) ubiquitin ligase family, which mediate the proteasomal degradation of Smads and/or receptors. Recently, we have defined a novel interaction between Smads and UCH37 (ubiquitin C-terminal hydrolase 37), a DUB (de-ubiquitinating enzyme) that could potentially counteract Smurf-mediated ubiquitination. We have demonstrated specific interactions between UCH37 and inhibitory Smad7, as well as weaker associations with Smad2 and Smad3. Importantly, Smad7 can act as an adaptor able to recruit UCH37 to the type I TGF-β receptor. Consequently, UCH37 dramatically up-regulates TGF-β-dependent gene expression by de-ubiquitinating and stabilizing the type I TGF-β receptor. Our findings suggest that competing effects of ubiquitin ligases and DUBs in complex with Smad7 can serve to fine-tune responses to TGF-βs under various physiological and pathological conditions. Studies are currently under way using activity-based HA (haemagglutinin)-tagged ubiquitin probes to identify the full spectrum of DUBs that impact on Smad/TGF-β signalling activity.

scholarly journals Characterization of a Bone Morphogenetic Protein-responsive Smad-binding Element

2000 ◽  
Vol 11 (2) ◽  
pp. 555-565 ◽  
Author(s):  
Kiyoshi Kusanagi ◽  
Hirofumi Inoue ◽  
Yasuhiro Ishidou ◽  
Hiromu K. Mishima ◽  
Masahiro Kawabata ◽  
...  
Keyword(s):  
Bone Morphogenetic Proteins ◽  
Transforming Growth Factor ◽  
Specific Interaction ◽  
Transforming Growth Factor Β ◽  
Serine Threonine Kinase ◽  
Bmp Receptors ◽  
Morphogenetic Protein ◽  
Smad Phosphorylation ◽  
Smad Proteins ◽  
Smad Binding Element

Bone morphogenetic proteins (BMPs) are pleiotropic growth and differentiation factors belonging to the transforming growth factor-β (TGF-β) superfamily. Signals of the TGF-β-like ligands are propagated to the nucleus through specific interaction of transmembrane serine/threonine kinase receptors and Smad proteins. GCCGnCGC has been suggested as a consensus binding sequence for DrosophilaMad regulated by a BMP-like ligand, Decapentaplegic. Smad1 is one of the mammalian Smads activated by BMPs. Here we show that Smad1 binds to this motif upon BMP stimulation in the presence of the common Smad, Smad4. The binding affinity is likely to be relatively low, because Smad1 binds to three copies of the motif weakly, but more repeats of the motif significantly enhance the binding. Heterologous reporter genes (GCCG-Lux) with multiple repeats of the motif respond to BMP stimulation but not to TGF-β or activin. Mutational analyses reveal several bases critical for the responsiveness. A natural BMP-responsive reporter, pTlx-Lux, is activated by BMP receptors in P19 cells but not in mink lung cells. In contrast, GCCG-Lux responds to BMP stimulation in both cells, suggesting that it is a universal reporter that directly detects Smad phosphorylation by BMP receptors.

Bone Morphogenetic Proteins and Their Receptors in the Eye

2007 ◽  
Vol 232 (8) ◽  
pp. 979-992 ◽  
Author(s):  
Robert J. Wordinger ◽  
Abbot F. Clark
Keyword(s):  
Growth Factor ◽  
Bone Morphogenetic Proteins ◽  
Transforming Growth Factor ◽  
Transforming Growth Factor Β ◽  
Bmp Signaling ◽  
Receptor Expression ◽  
Future Research ◽  
Cellular Functions ◽  
Ocular Tissues ◽  
Bmp Receptors

The human genome encodes at least 42 different members of the transforming growth factor-β superfamily of growth factors. Bone morphogenetic proteins (BMPs) are the largest subfamily of proteins within the transforming growth factor-β superfamily and are involved in numerous cellular functions including development, morphogenesis, cell proliferation, apoptosis, and extracellular matrix synthesis. This article first reviews BMPs and BMP receptors, BMP signaling pathways, and mechanisms controlling BMP signaling. Second, we review BMP and BMP receptor expression during embryonic ocular development/ differentiation and in adult ocular tissues. Lastly, future research directions with respect to BMP, BMP receptors, and ocular tissues are suggested.

scholarly journals ALK7, a Receptor for Nodal, Is Dispensable for Embryogenesis and Left-Right Patterning in the Mouse

2004 ◽  
Vol 24 (21) ◽  
pp. 9383-9389 ◽  
Author(s):  
Henrik Jörnvall ◽  
Eva Reissmann ◽  
Olov Andersson ◽  
Mehrnaz Mehrkash ◽  
Carlos F. Ibáñez
Keyword(s):  
Transforming Growth Factor ◽  
Transforming Growth Factor Β ◽  
Limb Bud ◽  
Mutant Mice ◽  
Type I ◽  
Vertebrate Development ◽  
Serine Threonine Kinase ◽  
Genes Encoding ◽  
Limb Malformations

ABSTRACT Mesendoderm formation and left-right patterning during vertebrate development depend upon selected members of the transforming growth factor β superfamily, particularly Nodal and Nodal-related ligands. Two type I serine/threonine kinase receptors have been identified for Nodal, ALK4 and ALK7. Mouse embryos lacking ALK4 fail to produce mesendoderm and die shortly after gastrulation, resembling the phenotype of Nodal knockout mice. Whether ALK4 contributes to left-right patterning is still unknown. Here we report the generation and initial characterization of mice lacking ALK7. Homozygous mutant mice were born at the expected frequency and remained viable and fertile. Viability at weaning was not different from that of the wild type in ALK7 −/−; Nodal +/− and ALK7 −/−; ALK4 +/− compound mutants. ALK7 and ALK4 were highly expressed in interdigital regions of the developing limb bud. However, ALK7 mutant mice displayed no skeletal abnormalities or limb malformations. None of the left-right patterning abnormalities and organogenesis defects identified in mice carrying mutations in Nodal or in genes encoding ActRIIA and ActRIIB coreceptors, including heart malformations, pulmonary isomerism, right-sided gut, and spleen hypoplasia, were observed in mice lacking ALK7. Finally, the histological organization of the cerebellum, cortex, and hippocampus, all sites of significant ALK7 expression in the rodent brain, appeared normal in ALK7 mutant mice. We conclude that ALK7 is not an essential mediator of Nodal signaling during mesendoderm formation and left-right patterning in the mouse but may instead mediate other activities of Nodal and related ligands in the development or function of particular tissues and organs.

scholarly journals Transforming Growth Factor-β Induces Formation of a Dithiothreitol-resistant Type I/Type II Receptor Complex in Live Cells

1999 ◽  
Vol 274 (9) ◽  
pp. 5716-5722 ◽  
Author(s):  
Rebecca G. Wells ◽  
Lilach Gilboa ◽  
Yin Sun ◽  
Xuedong Liu ◽  
Yoav I. Henis ◽  
...  
Keyword(s):  
Growth Factor ◽  
Transforming Growth Factor ◽  
Transforming Growth Factor Β ◽  
Live Cells ◽  
Type I ◽  
Receptor Complex ◽  
Type Ii

scholarly journals The N domain of Smad7 is essential for specific inhibition of transforming growth factor-β signaling

2001 ◽  
Vol 155 (6) ◽  
pp. 1017-1028 ◽  
Author(s):  
Aki Hanyu ◽  
Yasuhiro Ishidou ◽  
Takanori Ebisawa ◽  
Tomomasa Shimanuki ◽  
Takeshi Imamura ◽  
...  
Keyword(s):  
Growth Factor ◽  
Bone Morphogenetic Proteins ◽  
Transforming Growth Factor ◽  
Transforming Growth Factor Β ◽  
Amino Acid Sequences ◽  
Bmp Signaling ◽  
Type I ◽  
Specific Inhibition ◽  
Amino Terminal ◽  
Carboxy Terminal

Inhibitory Smads (I-Smads) repress signaling by cytokines of the transforming growth factor-β (TGF-β) superfamily. I-Smads have conserved carboxy-terminal Mad homology 2 (MH2) domains, whereas the amino acid sequences of their amino-terminal regions (N domains) are highly divergent from those of other Smads. Of the two different I-Smads in mammals, Smad7 inhibited signaling by both TGF-β and bone morphogenetic proteins (BMPs), whereas Smad6 was less effective in inhibiting TGF-β signaling. Analyses using deletion mutants and chimeras of Smad6 and Smad7 revealed that the MH2 domains were responsible for the inhibition of both TGF-β and BMP signaling by I-Smads, but the isolated MH2 domains of Smad6 and Smad7 were less potent than the full-length Smad7 in inhibiting TGF-β signaling. The N domains of I-Smads determined the subcellular localization of these molecules. Chimeras containing the N domain of Smad7 interacted with the TGF-β type I receptor (TβR-I) more efficiently, and were more potent in repressing TGF-β signaling, than those containing the N domain of Smad6. The isolated N domain of Smad7 physically interacted with the MH2 domain of Smad7, and enhanced the inhibitory activity of the latter through facilitating interaction with TGF-β receptors. The N domain of Smad7 thus plays an important role in the specific inhibition of TGF-β signaling.

scholarly journals Cooperative Inhibition of Bone Morphogenetic Protein Signaling by Smurf1 and Inhibitory Smads

2003 ◽  
Vol 14 (7) ◽  
pp. 2809-2817 ◽  
Author(s):  
Gyo Murakami ◽  
Tetsuro Watabe ◽  
Kunio Takaoka ◽  
Kohei Miyazono ◽  
Takeshi Imamura
Keyword(s):  
Bone Morphogenetic Proteins ◽  
Mammalian Cells ◽  
Transforming Growth Factor ◽  
Transforming Growth Factor Β ◽  
Bmp Signaling ◽  
Type I ◽  
Protein Signaling ◽  
Reporter Construct ◽  
Bone Morphogenetic Protein Signaling ◽  
Morphogenetic Protein

Smad ubiquitin regulatory factor (Smurf) 1 binds to receptor-regulated Smads for bone morphogenetic proteins (BMPs) Smad1/5 and promotes their degradation. In addition, Smurf1 associates with transforming growth factor-β type I receptor through the inhibitory Smad (I-Smad) Smad7 and induces their degradation. Herein, we examined whether Smurf1 negatively regulates BMP signaling together with the I-Smads Smad6/7. Smurf1 and Smad6 cooperatively induced secondary axes in Xenopus embryos. Using a BMP-responsive promoter-reporter construct in mammalian cells, we found that Smurf1 cooperated with I-Smad in inhibiting BMP signaling and that the inhibitory activity of Smurf1 was not necessarily correlated with its ability to bind to Smad1/5 directly. Smurf1 bound to BMP type I receptors via I-Smads and induced ubiquitination and degradation of these receptors. Moreover, Smurf1 associated with Smad1/5 indirectly through I-Smads and induced their ubiquitination and degradation. Smurf1 thus controls BMP signaling with and without I-Smads through multiple mechanisms.

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