Abstract
Transforming growth factor-β (TGF-β) family members, which include TGF-βs, activins, and bone morphogenetic proteins (BMPs), elicit their multifunctional effects by binding to and complex formation of type I and type II serine/threonine kinase receptors (see Fig. 1). Each family member signals via distinct combinations of type I and type II receptors, both of which are required for signaling. Upon formation of the heteromeric receptor complex, the type I receptor is phosphorylated by the type II receptor kinase. Phosphorylation occurs predominantly in a region rich in glycine and serine residues (GS domain) in the juxtamembrane domain of the type I receptor, which possibly leads to a conformational change and thereby activates the type I receptor kinase (see Fig. 1) (1–3). The activated type I receptor propagates the signal downstream through transient interaction with, and phosphorylation of, particular Smoeand mad related protein (Smad) molecules (1–3). Certain Smads are phosphorylated directly by activated type I receptors in a differential manner; they are therefore termed pathway-restricted Smads. Whereas Smad2 and Smad3 act in TGF-β and activin pathways, Smad1, Smad5, and Smad8 are thought to act in BMP pathways. Phosphorylation occurs at the two most C-terminal serine residues in a conserved C-terminal Ser-Ser-X-Ser motif (see Fig. 2). Pathway-restricted Smads oligomerize with Smad4, which acts as a common mediator in TGF-β, activin, and BMP signaling. After translocation to the nucleus, the oligomers interact with DNA directly, or in complex with other DNA-binding proteins, and control transcription of target genes (see Figs. 1 and 2). Recently, inhibitory Smads, Smad6, and Smad7, have been identified that antagonize TGF-β family signaling (3).
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Souchelnytskyi, S., Rönnstrand, L., Heldin, CH., Dijke, P.t. (2000). Phosphorylation of Smad Signaling Proteins by Receptor Serine/Threonine Kinases. In: Reith, A.D. (eds) Protein Kinase Protocols. Methods in Molecular Biology™, vol 124. Humana Press. https://doi.org/10.1385/1-59259-059-4:107
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DOI: https://doi.org/10.1385/1-59259-059-4:107
Publisher Name: Humana Press
Print ISBN: 978-0-89603-700-7
Online ISBN: 978-1-59259-059-9
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