TY - JOUR
T1 - Expression of functional Schistosoma mansoni Smad4
T2 - Role in Erk-mediated transforming growth factor β (TGF-β) down-regulation
AU - Osman, Ahmed
AU - Niles, Edward G.
AU - LoVerde, Philip T.
PY - 2004/2/20
Y1 - 2004/2/20
N2 - Members of the transforming growth factor (TGF)-β superfamily play pivotal roles in cell migration, differentiation, adhesion, pattern formation, and apoptosis. The family of Smad proteins acts as intracellular signal transducers of TGF-β and related peptides. Smad4, a common mediator Smad (co-Smad), performs a central role in transmitting signals from TGF-β, BMP, and activins. Schistosoma mansoni receptor-regulated Smad1 and SmSmad2 were previously identified and shown to act in TGF-β signaling. Herein, we report the identification and characterization of a Smad4 homologue from S. mansoni and provide details about its role in mediation and down-regulation of TGF-β signaling in schistosomes. In order to identify the schistosome co-Smad, we designed degenerate primers based on the sequence of the conserved MH1/MH2 domains of Smad4 proteins, which were used in PCR to amplify a 137-bp PCR product. A S. mansoni adult worm pair cDNA library was screened resulting in the isolation of a cDNA clone that encodes a 738 amino acid protein (SmSmad4). SmSmad4 was shown to interact with schistosome R-Smads (SmSmad1 and SmSmad2) in vivo and in vitro. The interaction with SmSmad2 was dependent on the receptor-mediated phosphorylation of SmSmad2. In addition, several potential phosphorylation sites for Erk1/2 kinases were identified in the SmSmad4 linker region and shown to be phosphorylated in vitro by an active mutant of mammalian Erk2. Furthermore, Erk-mediated phosphorylation of SmSmad4 decreased its interaction with the receptor-activated form of SmSmad2, in vitro. SmSmad4 was shown to complement a human Smad4 deficiency through the restoration of TGF-β-responsiveness in MDA-MB-468 breast cancer cells.
AB - Members of the transforming growth factor (TGF)-β superfamily play pivotal roles in cell migration, differentiation, adhesion, pattern formation, and apoptosis. The family of Smad proteins acts as intracellular signal transducers of TGF-β and related peptides. Smad4, a common mediator Smad (co-Smad), performs a central role in transmitting signals from TGF-β, BMP, and activins. Schistosoma mansoni receptor-regulated Smad1 and SmSmad2 were previously identified and shown to act in TGF-β signaling. Herein, we report the identification and characterization of a Smad4 homologue from S. mansoni and provide details about its role in mediation and down-regulation of TGF-β signaling in schistosomes. In order to identify the schistosome co-Smad, we designed degenerate primers based on the sequence of the conserved MH1/MH2 domains of Smad4 proteins, which were used in PCR to amplify a 137-bp PCR product. A S. mansoni adult worm pair cDNA library was screened resulting in the isolation of a cDNA clone that encodes a 738 amino acid protein (SmSmad4). SmSmad4 was shown to interact with schistosome R-Smads (SmSmad1 and SmSmad2) in vivo and in vitro. The interaction with SmSmad2 was dependent on the receptor-mediated phosphorylation of SmSmad2. In addition, several potential phosphorylation sites for Erk1/2 kinases were identified in the SmSmad4 linker region and shown to be phosphorylated in vitro by an active mutant of mammalian Erk2. Furthermore, Erk-mediated phosphorylation of SmSmad4 decreased its interaction with the receptor-activated form of SmSmad2, in vitro. SmSmad4 was shown to complement a human Smad4 deficiency through the restoration of TGF-β-responsiveness in MDA-MB-468 breast cancer cells.
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U2 - 10.1074/jbc.M310949200
DO - 10.1074/jbc.M310949200
M3 - Article
C2 - 14630909
AN - SCOPUS:1342282987
SN - 0021-9258
VL - 279
SP - 6474
EP - 6486
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
IS - 8
ER -