This invention relates to nectin polypeptides and polynucleotides, to methods of making such polypeptides and polynucleotides, and to methods of using such polypeptides and polynucleotides to modulate cell adhesion, cell migration, and angiogenesis, to treat conditions related to cell adhesion including endothelial and epithelial cell proliferation, migration, and barrier function, and to identify agents that alter nectin polypeptide activities.