The protein kinase Akt is activated by signals from membrane bound receptors, and serves as the effector molecule for various cellular functions, such as cell cycle progression, apoptosis, glucose metabolism, and regulation of translation. The Akt proteins (Akt1, 2 and 3) play a pivotal role in development of human cancers including carcinomas of the prostate, ovary and central nervous system. The goal of this proposal is to identify target proteins of Akt that are involved in the transforming activity of Akt. Several targets of Akt have been published, but their role in oncogenicity by Akt is largely unknown. The PI has identified additional candidate Akt targets through a yeast two-hybrid screen, and will incorporate these targets with the studies of several known targets. First, the mechanism of Akt mediated regulation of FKHR (forkhead in rhabdomyosarcoma) will be examined. Current dogma suggests that phosphorylation of this transcription factor is an endpoint for its regulation; however, the PI proposes subsequent proteolytic degradation plays a significant role, and has preliminary data to support such a novel mechanism. Second, cross talk on oncogenicity will be studied between Akt and beta-catenin, which is activated in many human cancers of the colon, the prostate and the liver. Finally, candidate Akt interacting proteins isolated by yeast two-hybrid screening will be evaluated for their role as Akt targets with PLZF (promyelocytic leukemia zinc finger) as a putative target. Each of these nuclear transcriptional regulators, FKHR, beta-catenin, PLZF, may be a major player in Akt oncogenicity, either singly or in cooperation with one another. The PI has shown that constitutively active Akt proteins induce neoplastic transformation of CEF (chicken embryo fibroblasts) and rapidly induce tumors in chickens, thus providing excellent functional assays for Akt targets. The PI has extensive experience with this system and will apply such a model given its sensitivity for transformation by oncoproteins. Specifically, this proposal seeks to define the relevance of each target of Akt in oncogenicity, and the mechanism through which Akt regulates these proteins. With a broad view, identification of relevant targets of Akt and understanding their roles in oncogenesis will reveal novel molecular targets for therapeutic applications for human cancers that involve Akt aberration.
