The overall goal of this project is to understand the mechanisms by which the integrin and actin cytoskeleton cross-talks with the microtubule (MT) cytoskeleton. Much has been learned about the individual signaling pathways that regulate the actin and MT cytoskeletons. However, for many processes dependent on cell polarization, and for cell migration in particular, we need to understand how the cytoskeletal systems are coordinated to give rise to a polarized cellular activity. For actin, Rho GTPase signaling pathways are known to be regulated by cytokine and growth factor receptors as well as integrin receptors stimulated by interactions with the extracellular matrix. For MTs, Rho GTPase signaling pathways are also regulated by cytokine and growth factor receptors, however, integrin regulation of MTs has only been hinted at and no signaling pathways have been identified. MTs have also been implicated in regulating focal adhesions (FAs), key sites of integrin signaling, yet again, the molecular pathways involved have not been identified. In preliminary studies, we have identified integrin activation as a critical factor in regulating the Rho signaling pathway that controls MT stabilization, and have identified focal adhesion kinase (FAK) and lipid rafts as key intermediates in the integrin signaling to MTs. We will pursue studies with FAK deficient cells to identify the specific lipid raft domain(s) regulated by FAK and will determine how FAK regulates this domain. We will study the role of lipid rafts in regulating MT stability and determine whether rafts provide a signaling or structural platform for stable MTs. We have also developed a system to study the MT dependent turnover of focal adhesions (FAs) and have used this system to identify novel factors, including dynamin, involved in this process. We will use this system to further explore how MTs stimulate the turnover of Fas and the role of dynamin and other factors in the turnover of FAs. Understanding the basic cross-talk pathways we have identified will provide information about the fundamental ways cells integrate their cytoskeletal systems during cell migration, a process of importance for development, wound healing and metastasis.