Androgen has been shown to stimulate proliferation of osteoblast-like MC3T3-E1 cells. However, the molecular mechanism responsible for this effect remains to be elucidated. In the present study we demonstrate herein the non-genomic effect of androgen on osteoblast-like MC3T3-E1 cells involving activation of a PI(3)K/Akt signaling pathway and stimulating proliferation.
In studies of steroids signaling, 5a-dihydrotestosterone (DHT), testosterone and 17b-estradiol but not dexamethasone or progesterone induced a rapid and transient phosphorylation of Akt in MC3T3-E1 cells. The androgen-induced Akt activation reached to the climax after 15 min and gradually diminished to baseline after 60 min. This induction of androgen was unaffected by actinomycin D and was specifically blocked by androgen receptor (AR) antagonist hydroxyflutamide (HF) or transfection of siRNA-AR. Treatment of MC3T3-E1 cells with PI(3)K inhibitor LY294002 or transfection with kinase-deficient Akt blocked androgen-induced cells proliferation.
Moreover, androgen-induced activation of Akt was abolished by inhibitors of Src kinase, Gi-protein and phospholipase C showing the involvement of these effectors in androgen signaling pathway. Further, androgen-induced activation of Akt was dependent on intracellular calcium as shown by the effect of EGTA and intracellular calcium chelator BAPTA/AM.
Fluorescence microscopy showed translocation of phospho-Akt from cytosol into nucleus after androgen treatment but no change in the subcellular distribution of phospho-Akt when HF or LY294002 pretreatment was administered to the cells.
These results strongly suggest that phosphorylation of Akt in osteoblast cells is mediated by androgen receptor and the androgen-induced translocation of Akt is an important step in the androgen/AR signaling pathway that mediates osteoblast cells proliferation.
| Identifer | oai:union.ndltd.org:NSYSU/oai:NSYSU:etd-0708103-151701 |
| Date | 08 July 2003 |
| Creators | Huang, Kai-Lieh |
| Contributors | Chung-Lung Cho, Jiin-Tsuey Cheng, Hong-Yo Kang, Michael Hsiao |
| Publisher | NSYSU |
| Source Sets | NSYSU Electronic Thesis and Dissertation Archive |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0708103-151701 |
| Rights | withheld, Copyright information available at source archive |
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