DROSOPHILA PS1 INTEGRIN IS A LAMININ RECEPTOR AND DIFFERS IN LIGAND SPECIFICITY FROM PS2

We have expressed Drosophila position-specific (PS) integrins on the s urfaces of Schneider S2 cells and tested for adhesion and spreading on various matrix molecules. We report that PS1 integrin is a laminin re ceptor and that PS1 and PS2 integrins promote cell spreading on two di fferent Drosophila extracellular matrix molecules, laminin and tiggrin , respectively. The differing ligand specificities of these two integr ins, combined with data on the in vivo expression patterns of the inte grins and their ligands, lead to a model for the structure of integrin -dependent attachments in the pupal wing and embryonic muscles of Dros ophila.