title: Smad regulation in TGF-beta signal transduction.
abstract: Smad proteins transduce signals from transforming growth factor-beta (TGF-beta) superfamily ligands that regulate cell proliferation, differentiation and death through activation of receptor serine/threonine kinases. Phosphorylation of receptor-activated Smads (R-Smads) leads to formation of complexes with the common mediator Smad (Co-Smad), which are imported to the nucleus. Nuclear Smad oligomers bind to DNA and associate with transcription factors to regulate expression of target genes. Alternatively, nuclear R-Smads associate with ubiquitin ligases and promote degradation of transcriptional repressors, thus facilitating target gene regulation by TGF-beta. Smads themselves can also become ubiquitinated and are degraded by proteasomes. Finally, the inhibitory Smads (I-Smads) block phosphorylation of R-Smads by the receptors and promote ubiquitination and degradation of receptor complexes, thus inhibiting signalling.
authors.affiliation: Ludwig Institute for Cancer Research, Box 595, SE-751 24 Uppsala, Sweden. Aris.Moustakas@LICR.uu.se
authors.forename: A
authors.initials: A
authors.lastname: Moustakas
authors.forename: S
authors.initials: S
authors.lastname: Souchelnytskyi
authors.forename: C H
authors.initials: CH
authors.lastname: Heldin
mesh_terms: D030201:Activin Receptors, Type I / Q000378:metabolism* / Q000502:physiology; D000818:Animals; D004268:DNA-Binding Proteins / Q000502:physiology; D006801:Humans; D010750:Phosphoproteins / Q000502:physiology; D017346:Protein Serine-Threonine Kinases; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism* / Q000502:physiology; D000077293:Receptor, Transforming Growth Factor-beta Type I; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism* / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*; D051785:Smad Proteins; D051899:Smad2 Protein; D051900:Smad3 Protein; D051901:Smad4 Protein; D051902:Smad5 Protein; D051904:Smad8 Protein; D015534:Trans-Activators / Q000502:physiology; D016212:Transforming Growth Factor beta / Q000502:physiology*
chemical_list: D004268:DNA-Binding Proteins; D010750:Phosphoproteins; D018125:Receptors, Transforming Growth Factor beta; C497782:SMAD2 protein, human; C497790:SMAD3 protein, human; C497796:SMAD4 protein, human; C497797:SMAD5 protein, human; C107514:SMAD9 protein, human; D051785:Smad Proteins; D051899:Smad2 Protein; D051900:Smad3 Protein; D051901:Smad4 Protein; C490811:Smad4 protein, rat; D051902:Smad5 Protein; D051904:Smad8 Protein; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D020794:Receptor Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D030201:Activin Receptors, Type I; D000077293:Receptor, Transforming Growth Factor-beta Type I; D000077294:Receptor, Transforming Growth Factor-beta Type II; C000625843:Tgfbr1 protein, rat