SANE, a Novel LEM Domain Protein, Regulates Bone Morphogenetic Protein Signaling through Interaction with Smad1 (original) (raw)
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Open biology, 2014
Bone morphogenetic proteins (BMPs) control multiple cellular processes in embryos and adult tissues. BMPs signal through the activation of type I BMP receptor kinases, which then phosphorylate SMADs 1/5/8. In the canonical pathway, this triggers the association of these SMADs with SMAD4 and their translocation to the nucleus, where they regulate gene expression. BMPs can also signal independently of SMAD4, but this pathway is poorly understood. Here, we report the discovery and characterization of PAWS1/FAM83G as a novel SMAD1 interactor. PAWS1 forms a complex with SMAD1 in a SMAD4independent manner, and BMP signalling induces the phosphorylation of PAWS1 through BMPR1A. The phosphorylation of PAWS1 in response to BMP is essential for activation of the SMAD4-independent BMP target genes NEDD9 and ASNS. Our findings identify PAWS1 as the first non-SMAD substrate for type I BMP receptor kinases and as a novel player in the BMP pathway. We also demonstrate that PAWS1 regulates the expression of several non-BMP target genes, suggesting roles for PAWS1 beyond the BMP pathway.
Promoting bone morphogenetic protein signaling through negative regulation of inhibitory Smads
The EMBO journal, 2001
Inhibitory Smads, i.e. Smad6 and Smad7, are potent antagonists of the BMP-Smad pathway by interacting with activated bone morphogenetic protein (BMP) type I receptors and thereby preventing the activation of receptor-regulated Smads, or by competing with activated R-Smads for heteromeric complex formation with Smad4. The molecular mechanisms that underlie the regulation of I-Smad activity have remained elusive. Here we report the identification of a cytoplasmic protein, previously termed associated molecule with the SH3 domain of STAM (AMSH), as a direct binding partner for Smad6. AMSH interacts with Smad6, but not with R- and Co-Smads, upon BMP receptor activation in cultured cells. Consistent with this finding, stimulation of cells with BMP induces a co-localization of Smad6 with AMSH in the cytoplasm. Ectopic expression of AMSH prolongs BMP-induced Smad1 phosphorylation, and potentiates BMP-induced activation of transcriptional reporter activity, growth arrest and apoptosis. The ...
Molecular and cellular biology, 2012
In vivo cells receive simultaneous signals from multiple extracellular ligands and must integrate and interpret them to respond appropriately. Here we investigate the interplay between pathways downstream of two transforming growth factor β (TGF-β) superfamily members, bone morphogenetic protein (BMP) and TGF-β. We show that in multiple cell lines, TGF-β potently inhibits BMP-induced transcription at the level of both BMP-responsive reporter genes and endogenous BMP target genes. This inhibitory effect requires the TGF-β type I receptor ALK5 and is independent of new protein synthesis. Strikingly, we show that Smad3 is required for TGF-β's inhibitory effects, whereas Smad2 is not. We go on to demonstrate that TGF-β induces the formation of complexes comprising phosphorylated Smad1/5 and Smad3, which bind to BMP-responsive elements in vitro and in vivo and mediate TGF-β-induced transcriptional repression. Furthermore, loss of Smad3 confers on TGF-β the ability to induce transcrip...
Controlling of bone morphogenetic protein signaling
Cellular Signalling, 2010
Bone morphogenetic proteins (BMPs) are multifunctional growth factors and play crucial roles during embryonic development, skeletal development, and cell fate determination. Their signals are transduced from cell membrane to the nucleus through intracellular signaling mediators. At present, different signaling pathways have been identified, and elaborate of network of regulators involved in the signaling control. The aim of the present review is to describe the recent understanding of BMPs signaling with emphasis on the regulation of its signal transduction at extracellular level, intracellular level, Smad-interacting factors in the nucleus, and Smad-independent signaling pathways, respectively.
Journal of Biological Chemistry, 1998
Members of the transforming growth factor- (TGF-) family transmit signals from membrane to nucleus via intracellular proteins known as Smads. A subclass of Smad proteins has recently been identified that antagonize, rather than transduce, TGF- family signals. Smad7, for example, binds to and inhibits signaling downstream of TGF- receptors. Here we report that the C-terminal MAD homology domain of murine Smad7 (mSmad7) is sufficient for both of these activities. In addition, we show that mSmad7 interacts with activated bone morphogenetic protein (BMP) type I receptors (BMPR-Is), inhibits BMPR-I-mediated Smad phosphorylation, and phenocopies the effect of known BMP antagonists when overexpressed in ventral cells of Xenopus embryos. Xenopus Smad7 (XSmad7, previously termed Smad8) and mSmad7 are nearly identical within their bioactive C-domain, but have quite distinct Ndomains. We found that XSmad7, similar to mSmad7, interacted with BMP and TGF- type I receptors and inhibited receptor-mediated phosphorylation of downstream signal-transducing Smads. However, XSmad7 is a less efficient inhibitor of TR-I-mediated responses in mammalian cells than is mSmad7. Furthermore, overexpression of XSmad7 in Xenopus embryos produces patterning defects that are not observed following overexpression of mSmad7, suggesting that mSmad7 and XSmad7 may preferentially target distinct signaling pathways. Our results are consistent with the possibility that the C-domain of antagonistic Smads is an effector domain whereas the N-domain may confer specificity for distinct signaling pathways.
Smad signaling in skeletal development and regeneration
Cytokine & Growth Factor Reviews, 2009
Smad proteins are intracellular molecules that mediate the canonical signaling cascade of TGFβ superfamily growth factors. The TGFβ superfamily comprises two groups of growth factors, BMPs and TGFβs. Both groups can be further divided into several sub-groups based on sequence homologies and functional similarities. Ligands of the TGFβ superfamily bind to cell surface receptors to activate Smad proteins in the cytoplasm; then the activated Smad proteins translocate into the nucleus to activate or repress specific target gene transcription. Both groups of growth factors play important roles in skeletal development and regeneration. However, whether these effects reflect signaling through canonical Smad pathways, or other non-canonical signaling pathways in vivo remains a mystery. Moreover, the mechanisms utilized by Smad proteins to initiate nuclear events and their interactions with cytoplasmic proteins are still under intensive investigation. This review will discuss the most recent progress understanding Smad signaling in the context of skeletal development and regeneration.
The journal of histochemistry and cytochemistry : official journal of the Histochemistry Society, 2014
Transforming growth factor-β (TGF-β) is an important regulator of cellular homeostasis and disease pathogenesis. Canonical TGF-β signaling occurs through Smad2/3-Smad4 complexes; however, recent in vitro studies suggest that elevated levels of TGF-β may activate a novel mixed Smad complex (Smad2/3-Smad1/5/9), which is required for some of the pro-oncogenic activities of TGF-β. To determine if mixed Smad complexes are evident in vivo, we developed antibodies that can be used with a proximity ligation assay to detect either canonical or mixed Smad complexes in formalin-fixed paraffin-embedded sections. We demonstrate high expression of mixed Smad complexes in the tissues from mice genetically engineered to express high levels of TGF-β1. Mixed Smad complexes were also prominent in 15-16 day gestation mouse embryos and in breast cancer xenografts, suggesting important roles in embryonic development and tumorigenesis. In contrast, mixed Smad complexes were expressed at extremely low leve...
Journal of Biological Chemistry, 2006
Development and repair of the skeletal system and other organs is highly dependent on precise regulation of bone morphogenetic proteins (BMPs), their receptors, and their intracellular signaling proteins known as Smads. The use of BMPs clinically to induce bone formation has been limited in part by the requirement of much higher doses of recombinant proteins in primates than were needed in cell culture or rodents. Therefore, control of cellular responsiveness to BMPs is now a critical area that is poorly understood. We determined that LMP-1, a LIM domain protein capable of inducing de novo bone formation, interacts with Smurf1 (Smad ubiquitin regulatory factor 1) and prevents ubiquitination of Smads. In the region of LMP responsible for bone formation, there is a motif that directly interacts with the Smurf1 WW2 domain and can effectively compete with Smad1 and Smad5 for binding. We have shown that small peptides containing this motif can mimic the ability to block Smurf1 from binding Smads. This novel interaction of LMP-1 with the WW2 domain of Smurf1 to block Smad binding results in increased cellular responsiveness to exogenous BMP and demonstrates a novel regulatory mechanism for the BMP signaling pathway.