Estrogen Receptor- Interacts with G13 at the Cell Membrane and Induces Dynamic Rearrangements of the Actin Cytoskeleton Via the RhoA/ROCK/Moesin Pathway

SIMONCINI, T; MANNELLA, P; FORNARI, L; CARUSO, A; GARIBALDI, S; GIRETTI, M; WIILIS, M; SCORTICATI, C; BALDACCI, C; NAFTOLIN, F; GENAZZANI, AR

San Diego, USA

Congreso; The Endocrine Society Annual Metting; 2005

Endocrine Society

Estrogen signaling through non-transcriptional pathways mediates a number of biological actions of this hormone in human cells. One of the observed but yet unexplained actions of estrogen is the ability to induce rapid changes of cell shape and the formation of specialized cell membrane structures, that play a role in cell motility and cross-talk. We observe that estradiol induces a rapid rearrangement of the actin cytoskeleton in human endothelial cells with the formation of a cortical actin complex, together with the dynamic development of cell membrane ruffles and pseudopodia. This process ensues in a few minutes and is coupled with the activation of the actin-regulatory protein, moesin. Moesin activation by estradiol is prevented by antagonists of the estrogen receptor, is replicated by ER-selective ligands and is elicited by a membrane-impermeable form of estradiol, indicating that the process is started by ER at the cell membrane. Furthermore, estrogens actions on moesin and on actin rearrangement are blocked by the G protein antagonist, pertussis toxin but not by MAP kinase or PI3 kinase inhibitors. In agreement, we surprisingly find that cell membrane-ER associates and interacts with G13 at the cell membrane, leading to increased G13 GTP-binding activity and moesin activation. Following G13 activation, the small GTP-binding protein RhoA is activated, leading to the recruitment of the Rho-associated-Kinase, ROCK-2. Transient transfection with negative dominant constructs for G13 or RhoA abolishes the estrogen-dependent rapid activation of G13, RhoA and moesin as well as the actin cytoskeleton rearrangement. ROCK-2 is responsible for the estrogen-dependent thr-phosphorylation of moesin that leads to rapid rearrangements of the actin cytoskeleton. In conclusion, we have identified a novel nongenomic signaling pathway of ER that is implicated in the structural modification of the actin cytoskeleton in endothelial cells. This may explain some of the previously observed effects of estradiol on endothelial cell proliferation and on the repair of vascular damage. Moreover, this original signaling mechanism of ER may be highly relevant in other cell types where estradiol induces proliferation and migration, such as in hormone-dependent cancer cells, providing new pathways to understand and discover mechanistic-driven applications to activate or repress estrogen-dependent effects in human cells.