Chromosomal Region Maintenance 1 (CRM1)-dependent Nuclear Export of Smad Ubiquitin Regulatory Factor 1 (Smurf1) Is Essential for Negative Regulation of Transforming Growth Factor-β Signaling by Smad7

Tajima, Yoshitaka; Goto, Kouichiro; Yoshida, Minoru; Shinomiya, Kenichi; Sekimoto, Takeyuki; Yoneda, Yoshihiro; Miyazono, Kohei; Imamura, Takeshi

doi:10.1074/jbc.m212663200

Cited by 82 publications

(51 citation statements)

References 27 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The interaction between the phosphorylated Smad3 and MyoD was observed within 30 min after the addition of TGF-␤. Moreover, the Smurf1⅐Smad7 complex-mediated TGF-␤ receptor degradation requires export of the Smurf1⅐Smad7 complex to the cytoplasm and translocation to the plasma membrane (36,37). This process may require auxiliary factors, and if any one of these factors is absent in C2C12 cells, the Smurf1⅐Smad7 action on cell surface receptors would be inoperable.…”

Section: Discussionmentioning

confidence: 99%

Smurf1 Facilitates Myogenic Differentiation and Antagonizes the Bone Morphogenetic Protein-2-induced Osteoblast Conversion by Targeting Smad5 for Degradation

Ying

Hussain

Zhang

2003

Journal of Biological Chemistry

View full text Add to dashboard Cite

Controlled proteolysis mediated by Smad ubiquitination regulatory factors (Smurfs) plays a crucial role in modulating cellular responses to signaling of the transforming growth factor-␤ (TGF-␤) superfamily. However, it is not clear what influences the selectivity of Smurfs in the individual signaling pathway, nor is it clear the biological function of Smurfs in vivo. Using a mouse C2C12 myoblast cell differentiation system, which is subject to control by both TGF-␤ and bone morphogenetic protein (BMP), here we examine the role of Smurf1 in myogenic differentiation. We show that increased expression of Smurf1 promotes myogenic differentiation of C2C12 cells and blocks the BMP-induced osteogenic conversion but has no effect on the TGF-␤-induced differentiation arrest. Consistent with an inhibitory role in the BMP signaling pathway, the elevated Smurf1 markedly reduces the level of endogenous Smad5, whereas it leaves unaltered that of Smad2, Smad3, and Smad7, which are components of the TGF-␤ pathway. Adding back Smad5 from a different source to the Smurf1-overexpressing cells restores the BMP-mediated osteoblast conversion. Finally, by depletion of the endogenous Smurf1 through small interfering RNA-mediated RNA interference, we demonstrate that Smurf1 is required for the myogenic differentiation of C2C12 cells and plays an important regulatory role in the BMP-2-mediated osteoblast conversion.Smad proteins are principal intracellular signaling mediators of the TGF-␤ 1 superfamily of peptide growth factors that regulate a wide range of biological processes (1-3). As such, controlling Smad activity and protein levels are crucial for proper signaling by TGF-␤ and its related factors. Recent discoveries of Smad ubiquitination regulatory factors (Smurfs), which are members of the HECT domain family of ubiquitin ligases, have implicated a role of the ubiquitination-mediated protein degradation in the signaling pathways of TGF-␤ superfamily (4 -7). Ubiquitination is a covalent attachment of a chain of the highly conserved, 76-amino acid ubiquitin to selected targets, which are subsequently degraded in the 26 S proteasomes (8, 9). This process is catalyzed by sequential actions of three enzymes, the E1 ubiquitin activating enzyme, the E2 ubiquitin-conjugating enzyme, and the E3 ubiquitin ligase. Ubiquitin ligases physically interact with protein substrates, therefore playing a central role in determining substrate specificity. Despite several reports of biochemical evidence for the Smurf-mediated degradation of Smads, important questions remain with regard to the biological significance of this regulation and the specificity of Smurf action.Signaling by the TGF-␤ superfamily of peptide growth factors is mediated by a complex of two types of transmembrane serine/threonine kinase receptors and the intracellular Smad proteins (for reviews, see Refs. 1-3). Three classes of Smads have been defined based on their differences in sequence and function: the receptor-regulated Smads (R-Smads), the common Smad (Smad4), and the inhib...

show abstract

Section: Discussionmentioning

confidence: 99%

Smurf1 Facilitates Myogenic Differentiation and Antagonizes the Bone Morphogenetic Protein-2-induced Osteoblast Conversion by Targeting Smad5 for Degradation

Ying

Hussain

Zhang

2003

Journal of Biological Chemistry

View full text Add to dashboard Cite

show abstract

“…Smurf2, a Smurf1-related E3 ubiquitin ligase, interacts with Smad1, as well as Smad2, and induces their ubiquitin-mediated degradation [14,15]. In addition, Smurfs 1 and 2 interact with nuclear Smad7 and induce translocation of Smad7 to the cytoplasm in a CRM-1 (chromosome region maintenance 1)-dependent fashion [16][17][18]. The Smurf1-Smad7 complex is then targeted to the cell membrane through the N-terminal C2 domain in Smurf1, and associates with TβR-I (TGF-β type I receptor) [19].…”

Section: Introductionmentioning

confidence: 99%

NEDD4-2 (neural precursor cell expressed, developmentally down-regulated 4-2) negatively regulates TGF-β (transforming growth factor-β) signalling by inducing ubiquitin-mediated degradation of Smad2 and TGF-β type I receptor

Kuratomi

Komuro

Goto

et al. 2005

Biochemical Journal

Self Cite

197

143

View full text Add to dashboard Cite

Inhibitory Smad, Smad7, is a potent inhibitor of TGF-β (transforming growth factor-β) superfamily signalling. By binding to activated type I receptors, it prevents the activation of R-Smads (receptor-regulated Smads). To identify new components of the Smad pathway, we performed yeast two-hybrid screening using Smad7 as bait, and identified NEDD4-2 (neural precursor cell expressed, developmentally down-regulated 4-2) as a direct binding partner of Smad7. NEDD4-2 is structurally similar to Smurfs (Smad ubiquitin regulatory factors) 1 and 2, which were identified previously as E3 ubiquitin ligases for R-Smads and TGF-β superfamily receptors. NEDD4-2 functions like Smurfs 1 and 2 in that it associates with TGF-β type I receptor via Smad7, and induces its ubiquitin-dependent degradation. Moreover, NEDD4-2 bound to TGF-β-specific R-Smads, Smads 2 and 3, in a ligand-dependent manner, and induced degradation of Smad2, but not Smad3. However, in contrast with Smurf2, NEDD4-2 failed to induce ubiquitination of SnoN (Ski-related novel protein N), although NEDD4-2 bound to SnoN via Smad2 more strongly than Smurf2. We showed further that overexpressed NEDD4-2 prevents transcriptional activity induced by TGF-β and BMP, whereas silencing of the NEDD4-2 gene by siRNA (small interfering RNA) resulted in enhancement of the responsiveness to TGF-β superfamily cytokines. These data suggest that NEDD4-2 is a member of the Smurf-like C2-WW-HECT (WW is Trp-Trp and HECT is homologous to the E6-accessory protein) type E3 ubiquitin ligases, which negatively regulate TGF-β superfamily signalling through similar, but not identical, mechanisms to those used by Smurfs.

show abstract

“…SMAD7 stably interacts with the activated TGF-␤ receptor type I to prevent association and phosphorylation of SMAD2 and SMAD3 and thus inhibits SMAD2 and SMAD3 nuclear translocation (7). Furthermore, SMAD7 inhibits TGF-␤ responsiveness by promoting degradation of TGF-␤ receptor type I through recruitment of an E3 ubiquitin-protein isopeptide ligase to the TGF-␤ receptor (37)(38)(39)(40). In addition to its inhibitory effects at the TGF-␤ receptor, SMAD7 can function as a transcription repressor in the nucleus by recruiting histone deacetylases to TGF-␤/Smad target genes (41).…”

Section: Overexpression Of Dominant Negative C-jun Abolished Uv Irradmentioning

confidence: 99%

Ultraviolet Irradiation Induces Smad7 via Induction of Transcription Factor AP-1 in Human Skin Fibroblasts

Quan

Torebjörk

Voorhees

et al. 2005

Journal of Biological Chemistry

View full text Add to dashboard Cite

Smad7 functions as an endogenous negative regulator of transforming growth factor-␤ (TGF-␤)/SMAD signaling. The TGF-␤/SMAD pathway is a major regulator of collagen production in connective tissue. Reduced expression of SMAD7 has been reported in TGF-␤-mediated fibrotic diseases, characterized by overproduction of collagen. Solar ultraviolet (UV) irradiation reduces collagen production by fibroblasts in human skin in vivo. We have investigated regulation of Smad7 gene expression by UV irradiation in human skin fibroblasts. UV irradiation transiently increased SMAD7 mRNA and protein levels. Induction of SMAD7 mRNA and protein was maximal within 5 h and returned to initial basal levels 24 h post-UV irradiation. UV irradiation induced Smad7 promoter-reporter activity 3-fold. The Smad7 promoter contains functional enhancer sequences that bind transcription factors SMAD3 and activator protein-1 (AP-1). UV irradiation reduced protein binding to the Smad3 enhancer and increased binding to the AP-1 enhancer. Deletion of the AP-1 binding site in the Smad7 promoter completely abolished UV stimulation of SMAD7 transcription. Deletion of the Smad3 element had no effect on UV irradiation-induced promoter activity. UV irradiation increased mRNA and protein expression of the AP-1 family members, c-Jun and c-Fos, which bound to the AP-1 element in the Smad7 promoter. Furthermore, overexpression of dominant negative c-Jun substantially reduced UV irradiation induction of SMAD7 transcription. These data demonstrate that induction of Smad7 gene expression by UV irradiation is mediated via induction of the transcription factor AP-1 in human skin fibroblasts.

show abstract

Chromosomal Region Maintenance 1 (CRM1)-dependent Nuclear Export of Smad Ubiquitin Regulatory Factor 1 (Smurf1) Is Essential for Negative Regulation of Transforming Growth Factor-β Signaling by Smad7

Cited by 82 publications

References 27 publications

Smurf1 Facilitates Myogenic Differentiation and Antagonizes the Bone Morphogenetic Protein-2-induced Osteoblast Conversion by Targeting Smad5 for Degradation

Smurf1 Facilitates Myogenic Differentiation and Antagonizes the Bone Morphogenetic Protein-2-induced Osteoblast Conversion by Targeting Smad5 for Degradation

NEDD4-2 (neural precursor cell expressed, developmentally down-regulated 4-2) negatively regulates TGF-β (transforming growth factor-β) signalling by inducing ubiquitin-mediated degradation of Smad2 and TGF-β type I receptor

Ultraviolet Irradiation Induces Smad7 via Induction of Transcription Factor AP-1 in Human Skin Fibroblasts

Contact Info

Product

Resources

About