Tài liệu Báo cáo khoa học: Identification and characterization of an R-Smad ortholog (SmSmad1B) from

Identification and characterization of an R-Smad ortholog

(SmSmad1B) from Schistosoma mansoni

Joelle M. Carlo1

*, Ahmed Osman1,2*, Edward G. Niles1

, Wenjie Wu2

, Marcelo R. Fantappie2

,

Francisco M. B. Oliveira2 and Philip T. LoVerde1,2

1 Department of Microbiology and Immunology, School of Medicine and Biomedical Sciences, State University of New York, NY, USA

2 Southwest Foundation for Biomedical Research, San Antonio, TX, USA

The multicellular, dioecious parasite Schistosoma

mansoni has a complex life cycle consisting of both

free-living and host-dependent stages. The signaling

mechanisms underlying the growth and development

of S. mansoni during these stages have remained

largely undefined. In the human host, S. mansoni para￾sites develop from schistosomules to adults, and can

survive in the host mesenteric circulation for years.

The implication that host molecules may be exploited

by schistosomes to enhance the parasites’ development

Keywords

bone morphogenic protein; Schistosoma

mansoni; Smad; transforming growth

factor-b

Correspondence

P. T. LoVerde, South-west Foundation for

Biomedical Research, PO Box 7620, NW

Loop 410, San Antonio, TX 78227-5301,

USA

Fax: +1 210 670 3322

Tel: +1 216 258 5892

E-mail: [email protected]

Database

The nucleotide sequence described here is

available in the GenBank database under the

accession number AY666164

*These authors contributed equally to this

work

(Received 14 February 2007, revised 5 June

2007, accepted 11 June 2007)

doi:10.1111/j.1742-4658.2007.05930.x

Smad proteins are the cellular mediators of the transforming growth fac￾tor-b superfamily signals. Herein, we describe the isolation of a fourth

Smad gene from the helminth Schistosoma mansoni, a receptor-regulated

Smad (R-Smad) gene termed SmSmad1B. The SmSmad1B protein is com￾posed of 380 amino acids, and contains conserved MH1 and MH2 domains

separated by a short 42 amino acid linker region. The SmSmad1B gene

(> 10.7 kb) is composed of five exons separated by four introns. On the

basis of phylogenetic analysis, SmSmad1B demonstrates homology to

Smad proteins involved in the bone morphogenetic protein pathway. Sm￾Smad1B transcript is expressed in all stages of schistosome development,

and exhibits the highest expression level in the cercariae stage. By immuno￾localization experiments, the SmSmad1B protein was detected in the cells

of the parenchyma of adult schistosomes as well as in female reproductive

tissues. Yeast two-hybrid experiments revealed an interaction between Sm￾Smad1B and the common Smad, SmSmad4. As determined by yeast three￾hybrid assays and pull-down assays, the presence of the wild-type or

mutated SmTbRI receptor resulted in a decreased interaction between

SmSmad1B and SmSmad4. These results suggest the presence of a non￾functional interaction between SmSmad1B and SmTbRI that does not give

rise to the phosphorylation and the release of SmSmad1B to form a het￾erodimer with SmSmad4. SmSmad1B, as well as the schistosome bone

morphogenetic protein-related Smad SmSmad1 and the transforming

growth factor-b-related SmSmad2, interacted with the schistosome coacti￾vator proteins SmGCN5 and SmCBP1 in pull-down assays. In all, these

data suggest the involvement of SmSmad1B in critical biological processes

such as schistosome reproductive development.

Abbreviations

AP-1, activator protein-1; 3-AT, 3-amino-1,2,4-triazole; BAC, bacterial artificial chromosome; b-gal, b-galactosidase; BMP, bone morphogenetic

protein; Co-Smad, common Smad; DPE, downstream promoter element; ERK, extracellular signal-regulated kinase; EST, expressed

sequence tag; Gal4AD, Gal4 activation domain; Gal4BD, Gal4 DNA-binding domain; GST, glutathione S-transferase; MBP, maltose-binding

protein; MH, Mad homology domain; R-Smad, receptor-regulated Smad; SmGCP, schistosome gynecophoral canal protein; TGFb,

transforming growth factor-b.

FEBS Journal 274 (2007) 4075–4093 ª 2007 The Authors Journal compilation ª 2007 FEBS 4075