Biological outputs of insulin/IGF signaling are regulated through essential mediators, such as IRSs, PI3-kinase, and PKB/Akt. These mediators serve critical roles in signal propagation, feedback, and as junctions for crosstalk with other pathways. Abnormal insulin/IGF signaling results in disease, such as obesity, diabetes, and cancer. Given the vital role of this signaling pathway to human health, unraveling its regulatory mechanisms is crucial. Components of this pathway are highly conserved throughout evolution. PTEN, one of the well-defined regulators of this pathway, functions as a lipid phosphatase that negatively regulates insulin/IGF-1 signaling at the PIP3 level, a phosphoinositol that is upregulated by activated PI3-kinase in both Drosophila and mammals. To discover genetic modulators of PTEN in Drosophila, we performed a loss-of-function genetic screen to identify molecules that modify the phenotype elicited by PTEN overexpression in the Drosophila eye. From this screen, we identified a member of the Dbl-family, the guanine nucleotide exchange factor DRhoGEF2, which suppresses the PTEN-overexpression eye phenotype via its effects on dPKB/dAkt activation. By conducting a genetic rescue, we established that PDZ-RhoGEF, a member of the regulator of G-protein signal (RGS)-like domain containing Rho GEFs (RGS-RhoGEFs) subfamily of Dbl-family GEFs, is the mammalian counterpart of DRhoGEF2. PDZ-RhoGEF is essential for cell proliferation and survival through ROCK-dependent activation of IRS/PI3-kinase signaling cascade, which has a major impact on adipose tissue homeostasis. Through an integrative approach, we have demonstrated that DRhoGEF2/PDZ-RhoGEF-dependent signaling has tissue-specific effects on insulin/IGF-signaling throughput in both Drosophila and mammals. Particularly, we have demonstrated the role played by PDZ-RhoGEF in diet related pathology, provides an alternative therapeutic opportunity in disease intervention.
| Identifer | oai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/29969 |
| Date | 15 September 2011 |
| Creators | Jang, Ying-Ju |
| Contributors | Mak, Tak Wah |
| Source Sets | University of Toronto |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
Page generated in 0.002 seconds