Cloning and expression of new receptors belonging to the immunoglobulin superfamily from the marine sponge Geodia cydonium |
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Authors: | Barbara Blumbach Bärbel Diehl-Seifert Jürgen Seack Renate Steffen Isabel M Müller W E G Müller |
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Institution: | Institut für Physiologische Chemie, Abteilung Angewandte Molekularbiologie, Universit?t, Duesbergweg 6, D-55099 Mainz; Germany e-mail: WMUELLER@mail.ZDV.UNI-Mainz.DE, Tel.: +6131-395910; Fax.: +6131-395243, DE
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Abstract: | A cDNA encoding a receptor tyrosine kinase (RTK) was previously cloned and expressed from the marine sponge (Porifera) Geodia cydonium. In addition to the two intracellular regions characteristic for RTKs, two immunoglobulin (Ig)-like domains are found in
the extracellular part of the sponge RTK. In the present study it is shown that no further Ig-like domain is present in the
upstream region of the cDNA as well as of the gene hitherto known from the sponge RTK. Two different full-length cDNAs have
been isolated and characterized in the present study, which possess two Ig-like domains, one transmembrane segment, and only
a short intracellular part, without a TK domain. The two deduced polypeptides were preliminarily termed sponge adhesion molecules
(SAM). The longer form of the SAM, GCSAML, encodes a deduced aa sequence, GCSAML, which comprises in the open reading frame 505 amino acids (aa) and has a calculated
M
r of 53911. The short form, GCSAMS, has 313 aa residues and an M
r of 33987. The two Ig-like domains in GCSAML and GCSAMS are highly similar to the corresponding Ig-like domains in the RTKs
from G. cydonium; the substitutions on both the aa and nt level are restricted to a few sites. Phylogenetic analyses revealed that the Ig-like
domain 1 is similar to the human Ig lambda chain variable region, while the Ig-like domain 2 is related more closely to the
human Ig heavy chain variable region. Transplantation experiments (autografting) were performed to demonstrate that the level
of expression of the two new genes, GCSAML and GCSAMS, is upregulated during the self/self fusion process. Immunohistochemical analyses using antibodies raised against the two
Ig-like domains demonstrate a strong expression in the fusion zone between graft and host. This finding has been supported
by northern blotting experiments that revealed that especially GCSAML is strongly upregulated after autografting (up to 12-fold); the expression of GCSAMS reaches a value of 5-fold if compared with the controls. The results presented here demonstrate that the expression of the
new molecules described, comprising two Ig-like domains, is upregulated during the process of autograft fusion.
Received: 17 November 1998 / Revised: 15 March 1999 |
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Keywords: | Sponges Geodia cydonium Ig-like domains Immune system Invertebrates |
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