AKT2 FUNCTION AND ONCOGENIC ACTIVITY

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DESCRIPTION: (adapted from the investigator's abstract) The applicants previously reported amplification/overexpression of the AKT2 oncogene in 10%-20% of human pancreatic and ovarian carcinomas, whereas alterations of the related gene, AKT1, are rarely observed in human cancer. They have demonstrated that overexpression of AKT2 transforms NIH 3T3 cells, and that AKT2 antisense RNA inhibits the tumorigenic phenotype of human pancreatic cancer cells exhibiting amplification/overexpression of AKT2. AKT2 encodes a serine-threonine kinase whose amino-terminus contains a pleckstrin homology (PH) domain characteristic of many signaling molecules. The role of AKT2 in signal transduction has not been explored in detail to date. Recently, the applicants have observed that AKT2 is activated by epidermal growth factor (EGF) through a pathway distinct from that of AKT1. Moreover, they have shown that AKT2 is abundantly expressed in tissues targeted by insulin, e.g., brown fat and muscle, suggesting that the AKT2 kinase could be involved in glucose transport. The broad, long-term objective of this project is to elucidate the normal cellular function of the AKT2 protein and determine the importance of perturbations of the AKT2 gene in human cancers. The proposed experiments are designed to test the hypothesis that AKT2 is an important signal mediator that contributes to the control of cell proliferation, and that aberrant expression of the AKT2 gene contributes to the development or progression of certain human epithelial tumors. The specific aims are threefold: 1) Directly test whether overexpression of Akt2 is oncogenic in transgenic mice. Akt2 transgenic mice will be used to ascertain if overexpression of Akt2 alone is tumorigenic in an in vivo model. To determine if aberrant expression of Akt2 could be important in multistep oncogenesis, tumorigenicity will also be examined in progeny of Akt2 transgenic mice crossed with mice harboring other oncogenic transgenes. 2) Delineate the role of AKT2 in the transduction of EGF- and insulin-mediated signals. To elucidate the normal cellular function of AKT2, they will delineate the specific EGFR signal transduction pathway contributing to the activation of AKT2 and determine the role of AKT2 in glucose transport. 3) Define the interaction between AKT2 and two potentially important signaling partners identified by yeast interaction trapping. To determine the physiological significance of these interactions, we will test whether these two candidate AKT2 interactors can regulate the kinase and transforming activities of AKT2. Overall, the proposed studies will yield important information concerning mechanisms by which AKT2 mediates cellular signals and elucidate mechanisms by which AKT2 alterations contribute to neoplasia.