TIGGRIN, A NOVEL DROSOPHILA EXTRACELLULAR-MATRIX PROTEIN THAT FUNCTIONS AS A LIGAND FOR DROSOPHILA ALPHA(PS2)BETA(PS) INTEGRINS

Genetic and other studies of Drosophila integrins have implicated thes e extracellular matrix receptors in various morphogenetic events, but identification of their endogenous ligands has been elusive. We report the biochemical purification and cloning of tiggrin, a novel extracel lular matrix protein from Drosophila. This 255x10(3) M(r) polypeptide contains the potential integrin recognition sequence Arg-Gly-Asp (RGD) and 16 repeats of a novel 73-77 amino acid motif. The tiggrin gene is at chromosome locus 26D1-2 and is expressed by embryonic hemocytes an d fat body cells. Tiggrin protein is detected in matrices, especially at muscle attachment sites that also strongly express integrins. Tiggr in-coated surfaces support primary embryo cell culture and provide exc ellent substrates for alpha(PS2)beta(PS) integrin-mediated cell spread ing. Soluble RGD-peptides inhibit this cell spreading.