Balancing BMP signaling through integrated inputs into the Smad1 linker

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Item Type:	Article
Title:	Balancing BMP signaling through integrated inputs into the Smad1 linker
Creators Name:	Sapkota, G., Alarcon, C., Spagnoli, F.M., Brivanlou, A.H. and Massague, J.
Abstract:	FGF and other Ras/MAPK pathway activators counterbalance BMP action during neurogenesis, bone formation, and other aspects of vertebrate development and homeostasis. BMP receptors signal through C-terminal phosphorylation and nuclear translocation of the transcription factor Smad1, whereas MAPKs catalyze inhibitory phosphorylation in the Smad1 linker region. Here we show that linker phosphorylation restricts Smad1 activity by enabling Smad1 recognition by the HECT-domain ubiquitin ligase Smurf1. Besides causing Smad1 polyubiquitination, Smurf1 binding inhibits the interaction of Smad1 with the nuclear translocation factor Nup214. Consequently, MAPK-dependent Smurf1 binding leads Smad1 alternatively to degradation or cytoplasmic retention. Smad1 linker phosphorylation and Smurf1 act as interdependent inputs to control BMP signaling during mouse osteoblast differentiation and Xenopus neural development. Linker phosphorylation is triggered also by BMP, providing feedback control. The interplay between linker phosphorylation, Smurf-dependent ubiquitination, and nucleoporin exclusion enables regulation of BMP action by diverse signals and biological contexts.
Keywords:	Bone Morphogenetic Proteins, Cultured Cells, Fibroblast Growth Factors, Glycogen Synthase Kinase 3, Mitogen-Activated Protein Kinases, Mitogens, Nuclear Pore Complex Proteins, Phosphorylation, Signal Transduction, Smad1 Protein, Ubiquitin, Ubiquitin-Protein Ligases, Animals, Mice, Xenopus
Source:	Molecular Cell
ISSN:	1097-2765
Publisher:	Cell Press
Volume:	25
Number:	3
Page Range:	441-454
Date:	9 February 2007
Official Publication:	https://doi.org/10.1016/j.molcel.2007.01.006
PubMed:	View item in PubMed

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