ON THE ORIGIN OF METAZOAN ADHESION RECEPTORS - CLONING OF INTEGRIN ALPHA-SUBUNIT FROM THE SPONGE GEODIA-CYDONIUM

Integrins are prominent receptors known from vertebrates and the highe r phyla of invertebrates. Until now, no evidence has been provided for the existence of integrins in the lowest Metazoa, the sponges (Porife ra). We have isolated and characterized a cDNA clone encoding the or s ubunit of integrin from the marine sponge Geodia cydonium (GCINTEG). T he open reading frame encodes a polypeptide of 1,086 residues (118 kDa ). The intracellular domain features the sequence 5r-Phe-x-Gly-Phe-Phe -x-Arg, which is different in one residue from the characteristic cons ensus pattern for integrin a subunits. We conclude that sponges, the o ldest multicellular animal phylum, already utilize the structural elem ents which are required for a tuned and controlled interaction among c ells, and between cells and the extracellular matrix.