Origin of the integrin‐mediated signal transduction

Abstract

Sponges (phylum Porifera) represent the phylogenetically oldest metazoan animals. Recently, from the marine sponge Geodia cydonium a first cDNA encoding a putative integrin receptor molecule was isolated. In the present study basic functional experiments have been conducted to test the hypothesis that in sponges integrin polypeptides also function as adhesion molecules and as outside-in signaling molecules. The sponge Suberites domuncula has been used for the experiments because from this sponge only has a cell culture been established. Here we report that aggregation factor (AF)-mediated cell-cell adhesion is blocked by the RGDS peptide which is known to interact with b integrin. Both RGDS and AF were found to stimulate DNA synthesis within 24 h. The b subunit of the integrin receptor was cloned from S. domuncula; the estimated 91-kDa molecule comprises the characteristic signatures. Evolutionary conservation of the b integrin was assessed by comparison with corresponding b integrin subunits from evolutionary higher metazoan taxa. Addition of RGDS or of AF to isolated cells of S. domuncula causes a rapid (within 1±2 min) increase in the intracellular Ca 2+ concentration which is further augmented in the presence of Ca 2+ . Furthermore, incubation of the cells with RGDS or AF causes an activation of the GTP-binding protein Ras. In addition it is shown that after a prolonged incubation of the cells with RGDS and AF the expression of the genes coding for Ras and for calmodulin is upregulated. These results suggest that the integrin receptor functions in the sponge system not only as adhesion molecule but also as a molecule involved in outside-in signaling.Keywords: Suberites domuncula, integrin, calcium, Ras, calmodulin, signal transduction, evolution, RGD(S), aggregation factor. Multicellularity in eukaryotes developed several times in evolution. Striking examples are the transition of unicellular to multicellular species within the volvocine algae (reviewed in [1]) which happened only 50±75 million years ago [2] while that of unicellular to multicellular animals dates back to 600 million years ago [3]. Until recently it remained unsolved if the evolution to multicellularity in Metazoa occurred only once (monophyly) or several times (polyphyly). Studies concentrating on those molecules which are considered to be characteristic for metazoan cells revealed that protein sequences, deduced from cDNAs obtained from the lowest metazoan phylum, the Porifera (sponges), are highly similar to those found in other metazoan phyla.Metazoan cells interact with each other differently than unicellular eukaryotes, especially with respect to (a) G-protein linked transmembrane receptors, (b) transmembrane adhesion molecules and (c) ligand-gated ion channels. Sequence data studies revealed that sponges ± the experiments have been performed mainly with the marine species Geodia cydonium and Suberites domuncula (reviewed in [4]) ± are provided with the G-protein linked transmembrane receptor, the metabotropic glutamate receptor [4a], ...

Phylogenetic evidence for the modular evolution of metazoan signalling pathways

“…Thus, studies of quantitative and spatial expression suggest that integrins play many diverse roles in the cell and tissue biology of cnidarians. Transduction of integrin-mediated signals into upregulated DNA synthesis was also demonstrated in the sponge S. domuncula [161], confirming that the inward transmission of signals from ECM to nucleus was functional before the origin of Porifera. Integrin signalling during development of ctenophores has not been studied but it is reasonable to hypothesize that intracellular signalling through integrins is likely operational in these animals as they possess the complete set of intracellular binding partners.…”

Sponge Bcl-2 homologous protein (BHP2-GC) confers distinct stress resistance to human HEK-293 cells

“…50,51 In addition, FuGENE 6 reagent, PCR-DIG (digoxigenin)-ProbeSynthesis Kit, anti-DIG AP Fab fragments and CDP [disodium 2-chloro-5- (4-methoxyspiro{1,2-dioxetane-3,2'-(5'-chloro)-tricyclo [3.3.1.1. 3,7 ]decan}-4-yl)phenyl phosphate] from Roche Diagnostics (Mannheim; Germany); RPMI-1640 and OptiMEM from Life Technologies (Karlsruhe; Germany); geneticine G418 from Invitrogen (Groningen; The Netherlands); tributyltin and labelled anti-rabbit Ig from Sigma (Deisenhofen; Germany); AC-DEVD-AMC from Peptide Institute (Osaka; Japan); monoclonal anti-Bcl-2 [human] antibodies (mouse) from Santa Cruz (Santa Cruz, Cal; USA); anti-mouse (Cy3 labeled) and anti-rabbit (FITC-labeled) from Dianova (Hamburg; Germany); the mouse anti-Hexa-histidine monoclonal antibody (McAb-anti-His) from Invitrogen (Groningen; The Netherlands).…”

Dynamical patterning modules: a "pattern language" for development and evolution of multicellular form

“…Most sponge cells (sclerocytes) reside within an ECM called the "mesohyl," which constitutes the bulk of the organism's body. These cells bind to the ECM via integrin transmembrane proteins (Wimmer et al, 1999), as in eumetazoans. Sponges also contain epithelial cells (Schröder et al, 2004) and homologs of type IV-like collagen (Boute et al, 1996), which in eumetazoans forms a major component of the sheet-like supporting structure for epithelia, the basal lamina.…”