Expression of functional Schistosoma mansoni Smad4: Role in Erk-mediated transforming growth factor β (TGF-β) down-regulation

Ahmed Osman, Edward G. Niles, Philip T Loverde

Research output: Contribution to journalArticle

45 Citations (Scopus)

Abstract

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.

Original languageEnglish (US)
Pages (from-to)6474-6486
Number of pages13
JournalJournal of Biological Chemistry
Volume279
Issue number8
DOIs
StatePublished - Feb 20 2004
Externally publishedYes

Fingerprint

Schistosoma mansoni
Transforming Growth Factors
Smad4 Protein
Down-Regulation
Phosphorylation
Smad Proteins
Activins
Polymerase Chain Reaction
Conserved Sequence
Transducers
Gene Library
Restoration
Cell Movement
Cell Differentiation
Phosphotransferases
Adhesion
Complementary DNA
Clone Cells
Cells
Apoptosis

ASJC Scopus subject areas

  • Biochemistry

Cite this

Expression of functional Schistosoma mansoni Smad4 : Role in Erk-mediated transforming growth factor β (TGF-β) down-regulation. / Osman, Ahmed; Niles, Edward G.; Loverde, Philip T.

In: Journal of Biological Chemistry, Vol. 279, No. 8, 20.02.2004, p. 6474-6486.

Research output: Contribution to journalArticle

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abstract = "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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