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Transforming Growth Factor β Can Stimulate Smad1 Phosphorylation Independently of Bone Morphogenic Protein Receptors*

By Katharine H. Wrighton, Xia Lin, Paul B. Yu and Xin-Hua Feng

Abstract

Transforming growth factor-β (TGFβ) superfamily ligands control a diverse set of cellular processes by activating type I and type II serine-threonine receptor kinases. Canonical TGFβ signaling is mediated via the TβRI/ALK5 type I receptor that phosphorylates Smad2 and Smad3 in their SXS motif to facilitate their activation and subsequent role in transcriptional regulation. Canonical bone morphogenic protein (BMP) signaling is mediated via the ALK1/2/3/6 type I receptors that phosphorylate Smad1, Smad5, and Smad8 in their SXS motif. However, studies in endothelial cells have shown that TGFβ can also lead to the phosphorylation of Smad1, dependent on ALK1 receptor activity. Here we present data showing that TGFβ can significantly induce Smad1 phosphorylation in several non-endothelial cell lineages. Additionally, by using chemical inhibitors specific for the TGFβ/activin/nodal (ALK4/5/7) and BMP (ALK1/2/3/6) type I receptors, we show that in some cell types TGFβ induces Smad1 phosphorylation independently of the BMP type I receptors. Thus, TGFβ-mediated Smad1 phosphorylation appears to occur via different receptor complexes in a cell type-specific manner

Topics: Mechanisms of Signal Transduction
Publisher: American Society for Biochemistry and Molecular Biology
OAI identifier: oai:pubmedcentral.nih.gov:2665096
Provided by: PubMed Central
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