Integrins are a family of cellular receptors that mediate attachment of cells to extracellular matrix or other cells. The interactions of integrins with their appropriate ligands are critical for cell survival, proliferation, and other specialized functions of animal cells. The development of tumors is associated with alterations in integrin expression or mutations in proteins mediate integrin functions in cells. These alterations allow tumor cells to survive and proliferate in the absence of natural adhesive interactions and to migrate and metastasize to other sites. Elucidation of the intracellular pathways that mediate those integrin regulated cellular events is critical to understanding the mechanisms involved in oncogenic transformation. The studies in this proposal are designed to dissect the intracellular components that are involved in integrin signaling events by defining the role of known phospholipid kinases and protein tyrosine and serine/threonine kinases in integrin mediated activation of cellular pathways that control cell growth, migration and survival. One section of the proposal focuses on the role of phosphatidylinositol 3'kinases and protein kinase Cs in integrin regulation of the Erk/MAP kinase family through the serine/threonine kinase Raf. In addition, we will pursue several strategies designed to identify novel components of integrin signaling pathways. These involve approaches to purify proteins phosphorylated following activation of integrins and to employ libraries of GFP fusion proteins to identify proteins that localize to integrin-nucleated focal adhesion complexes. In addition, we will use in vitro expression cloning strategies to clone substrates of kinases activated by integrins and 3'phosphatidylinositide binding proteins. These approaches should identify proteins that were previously unrecognized for their role in integrin signaling and allow us to expand our knowledge of how integrin- activated proteins interact to organize signaling pathways that control specific cell functions and possibly reveal new targets for therapeutic intervention in cancer.
