Full text
| |
| Author(s): |
Fábio Luís Forti
Total Authors: 1
|
| Document type: | Doctoral Thesis |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Conjunto das Químicas (IQ e FCF) (CQ/DBDCQ) |
| Defense date: | 2001-02-01 |
| Examining board members: |
Hugo Aguirre Armelin;
Paulo Lee Ho;
Hernando Antonio Del Portillo Obando;
Laerte de Oliveira;
Wladia Viviani
|
| Advisor: | Hugo Aguirre Armelin |
| Abstract | |
The adrenocorticotropic hormone, ACTH, regulates both function and proliferation of adrenocortical cells binding to a specific receptor, ACTHR, which belongs to superfamily of GPCR (G-protein coupled receptors). ACTHR was cloned a few years ago, but the molecular mechanisms underlying the mitogenic and anti-mitogenic actions of ACTH remain unknown, whose elucidation is aim of this project. The experimental approach was to clone the ACTHR from mouse Y-1 adrenocortical cells and to express the functional receptor in Balb 3T3 fibroblasts and AR-1 cells. Transfectant clones stably expressing the ACTHR respond to ACTH treatments by: a) adenylate cyclase activation and b) induction of fos and jun genes. On the other hand, experiments of DNA synthesis and cellular proliferation showed that ACTH has not mitogenic or anti-mitogenic effects in ACTHR transfectants. c-fos gene was used as a target to test signal transduction pathways activated by ACTH into 3T3 ACTHR transfectants. The results showed that PKA, PKC and MAPK have no relevant contribution on the ACTH c-fos induction in 3T3 ACTHR transfectants suggesting that ACTHR can activate signal transduction pathways still not identified. This conclusion prompted us to search for another signal transduction pathways triggered by ACTHR in Y-1 adrenocortical cells. This search led to the detection of high constitutive levels of activated AKT/PKB in Y-1 adrenocortical cells, which are dependent on PI3K and SRC. ACTH causes a strong and rapid downregulation of activated AKT in a Gs/Adenylate Cyclase/cAMP/PKA dependent manner. Apparently, dephosphorylation of AKT promoted by ACTH releases transcription factors that induce p27'IND.Kip1', a likely mechanism underlying ACTH anti-mitogenic effects in adrenocortical cells. (AU) | |