Identification and characterisation of two distinct Smad proteins from the fox-tapeworm Echinococcus multilocularis. Int J Parasitol 2003 Dec;33(14):1665-77
Date
11/26/2003Pubmed ID
14636682DOI
10.1016/s0020-7519(03)00208-xScopus ID
2-s2.0-0242551302 (requires institutional sign-in at Scopus site) 38 CitationsAbstract
Members of the transforming growth factor-beta (TGF-beta) family of cytokines and their corresponding receptors regulate cellular key processes such as proliferation and differentiation, and could be involved in communication mechanisms between parasitic helminths and their hosts. A pivotal role in intracellular TGF-beta signalling is played by Smad factors which directly transmit incoming signals from the cell surface receptors to the nucleus. In this study, we have identified and characterised two novel members of the Smad family, EmSmadA and EmSmadB, which are expressed by the human parasite Echinococcus multilocularis. Based on amino acid sequence comparisons, both echinococcal Smad homologues could be classified as members of the R-Smad subfamily. EmSmadB showed a typical domain structure consisting of conserved MH1 and MH2 domains separated by a proline-rich linker region. EmSmadA, on the other hand, lacked an MH1 region and merely contained an MH2 domain, a feature which has so far not been described for R-Smads. Based on the structures of the corresponding chromosomal loci and on sequence features of the conserved L3 loop regions, EmSmadA and EmSmadB are most likely involved in the transmission of TGF-beta- and bone morphogenetic protein (BMP) signals, respectively. Yeast two-hybrid analyses revealed that both Echinococcus Smads are capable of homo- and heterodimer formations. However, while the formation of homodimers for EmSmadB required previous activation of the protein at the C-terminal SSVS motif, EmSmadA homodimers were already formed in the basal state of the factor. Upon expression of the Echinococcus Smads in human cells, EmSmadA, but not EmSmadB, was phosphorylated by the human TGF-beta type I receptor. Furthermore, both factors functionally interacted with human BMP receptors. By reverse transcriptase-PCR experiments, the encoding genes, emsmadA and emsmadB, were shown to be expressed in the larval stages metacestode and protoscolex during an infection of the intermediate host. Taken together, our data suggest an involvement of EmSmadA and EmSmadB in echinococcal developmental processes during natural infections and provide a solid basis for further investigations on TGF-beta signalling mechanisms in cestodes.
Author List
Zavala-Góngora R, Kroner A, Wittek B, Knaus P, Brehm KAuthor
Antje Kroner-Milsch MD, PhD Associate Professor in the Neurosurgery department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
Amino Acid SequenceAnimals
Base Sequence
Carrier Proteins
Cells, Cultured
Echinococcosis, Hepatic
Echinococcus
Foxes
Gene Expression
Genes, Helminth
Helminth Proteins
Host-Parasite Interactions
Humans
Kidney
Larva
Molecular Sequence Data
Reverse Transcriptase Polymerase Chain Reaction
Sequence Analysis, DNA
Sequence Homology, Amino Acid
Transforming Growth Factor beta
