The integration of diverse cellular signals is critical to the precise spatial and temporal coordination of virtually all biological processes. Among the widely used regulatory mechanisms to achieve signal integration and biological coordination is protein phosphorylation. We have been investigating the role of specific protein phosphorylation events in controlling cell morphology, adhesion, and migration- processes that are stringently regulated by the Rho GTPases. These studies have revealed a critical role for the p190 Rho GTPase activating proteins (GAPs;p190A and p190B) as signal integrators whose phosphorylation by various intracellular kinases appears to be critical to its role in a variety of cellular processes. Our broad objective is to develop a clear understanding of the regulation of Rho- mediated cellular processes by the RhoGAPs, and the focus of the studies proposed here is to address the role of p190 RhoGAP phosphorylation in the integration of upstream regulatory signals. The following Aims are proposed: 1) To establish the regulatory function of PKC-mediated phosphorylation of p190A RhoGAP. 2) To establish a role for phospho-regulation of p190A in polarized cell migration. 3) To determine the functional role of phosphorylation-regulated protein interactions with the p190 FF domains. 4) To establish the regulation of p190B RhoGAP in IGF-1 signaling in cell adhesion. These 4 Aims reflect a large body of preliminary data that points to these critical phosphorylation events in the role of the p190 GAPs in regulating a variety of cell biological and developmental processes. We have generated the vast majority of reagents required for this analysis, which is expected to reveal substantial new insights into the role of these GAPs as signal integrators or "coincidence sensors" that regulate Rho-dependent cellular processes, including cell migration. Cell migration is an important cellular activity in the context of human cancers, where its role in metastasis, the most lethal aspect of the tumorigenic process, has been clearly established. By identifying regulatory mechanisms that affect cell migration, it should eventually be possible to develop novel therapeutic strategies to prevent or manage cancer metastasis.
The proposed studies address a fundamental issue in the biology of all normal and cancer cells, namely how do the various intracellular proteins integrate a variety of extracellular stimuli to properly "instruct" the cell to respond appropriately? By enhancing our understanding of how cancer cells respond to their environment, we may be able to develop strategies to disrupt the processes in these cells that contribute to their malignant properties of accelerated growth and metastatic spread.