PROJECT SUMMARY Transforming Growth Factor ? (TGF?) is a secreted protein and the first member of the TGF? su- perfamily of ligands to be described. However, the molecular mechanisms that govern TGF??s ability to switch between its paradoxical growth suppressing and epithelial-mesenchymal transition (EMT) promoting functions remain to be fully elucidated. Since TGF? elicits pleiotropic functions during normal development, adult tissue homeostasis and pathophysiological processes such as cancer and fibrosis, it is essential that future research efforts focus on producing a complete mechanistic understanding of TGF? function. To this end, the objective of this proposal is to investigate the cellular and molecular mechanisms by which PEAK1 (pseudopodium-enriched atypical kinase one) regulates TGF? signaling and mediates TGF?-induced EMT during disease progression. The proposed work is an extension of our recently published and compelling preliminary data showing that (i) PEAK1 mediates TGF?-induced EMT, migration, proliferation and cancer metastasis; (ii) PEAK1 localizes to membrane actin structures and regulates Src/Grb2/MAPK signaling in response to TGF?/fibronectin stimulation; and (iii) inhibition of PEAK1 translation blocks the pathophysiological effects of TGF? signaling. Thus, the central hypoth- esis of this proposal is that eIF5A-driven PEAK1 translation promotes the assembly of a Src/Grb2/PEAK1 complex in the context of membrane ITGB3 activation to enable TGF?-induced MAPK signaling, ZEB1 upregulation and EMT. The approach is innovative because it will employ a combina- tion of state-of-the-art cellular, molecular, biochemical, microscopy, proteomic and model organism methods to elucidate the mechanisms of action for the novel eIF5A/PEAK1 translation and Src/Grb2/PEAK1/MAPK cytoskeletal signaling nodes as novel regulators of TGF?-induced EMT. Furthermore, the proposed research is significant because it will address the following two major challenges and needs within the field of TGF? research: Specific Aim 1 will characterize translational and post-translational mechanisms of TGF?-induced EMT; and Specific Aim 2 will identify context- dependent spatiotemporal dynamics for molecular regulators of TGF? responses. The collective knowledge gained from these mechanistic studies will identify and characterize details of the cellular and molecular contexts in which TGF? is dysregulated to cause disease, and novel methods for block- ing the negative consequences of TGF? signaling.