The primary goal of these studies is to elucidate the mechanisms by which cells undergo controlled cell death, or apoptosis, in response to the expression of specific classes of unligated integrins. In the absence of appropriate ligands or in the presence of integrin antagonists, such integrins can even mediate apoptosis in cells that otherwise remain adherent to their surrounding extracellular matrix. This ability of integrin antagonists to induce death among endothelial cells has been exploited in the treatment of several angiogenesis-dependent diseases. However, the mechanisms by which these antagonists elicit Integrin Mediated Death (IMD) in vivo have remained obscure. Therefore, this proposal is designed characterize IMD, and determine the physiological contributions of this process to tissue remodeling associated with angiogenesis. First, the minimal structural domains within integrins and caspases that are required to effect IMD will be determined. This information will be used in the biochemical characterization of integrin / caspase complexes that form during induction of IMD. Finally, in vivo models will be used to evaluate the role of IMD during the physiological process of angiogenesis. These investigations will improve our understanding of the mechanisms by which unligated integrins induce apoptosis, thus determining whether induction of IMD can be developed as a rational anti-angiogenic therapy.