REQUIREMENT OF THE NPXY MOTIF IN THE INTEGRIN BETA-3 SUBUNIT CYTOPLASMIC TAIL FOR MELANOMA CELL-MIGRATION IN-VITRO AND IN-VIVO

The NPXY sequence is highly conserved among integrin beta subunit cyto plasmic tails, suggesting that it plays a fundamental role in regulati ng integrin-mediated function. Evidence is provided that the NPXY stru ctural motif within the beta 3 subunit, comprising residues 744-747, i s essential for cell morphological and migratory responses mediated by integrin alpha v beta 3 in vitro and in vivo. Transfection of CS-1 me lanoma cells with a cDNA encoding the wild-type integrin beta 3 subuni t, results in de novo alpha v beta 3 expression and cell attachment, s preading, and migration on vitronectin. CS-1 cells expressing (alpha v beta 3 with mutations that disrupt the NPXY sequence interact with so luble vitronectin or an RGD peptide, yet fail to attach, spread, or mi grate on immobilized ligand. The biological consequences of these obse rvations are underscored by the finding that CS-1 cells expressing wil d-type alpha v beta 3 acquire the capacity to form spontaneous pulmona ry metastases in the chick embryo when grown on the chorioallantoic me mbrane. However, migration-deficient CS-1 cells expressing alpha v bet a 3 with mutations in the NPXY sequence lose this ability to metastasi ze. These findings demonstrate that the NPXY motif within the integrin beta 3 cytoplasmic tail is essential for alpha v beta 3-dependent pos t-ligand binding events involved in cell migration and the metastatic phenotype of melanoma cells.