Intracellular signaling for estradiol induced axogenesis

S.V. GOROSITO; H.F. CARRER; M.J. CAMBIASSO

Pinamar, Buenos Aires-Argentina

Congreso; XX Reunión Anual de la SAN; 2005

We have previously shown that 17-b-estradiol (E2) (and the plasma membrane-non permeating E2BSA) induces a sustained and strong phosphorylation of ERK (pERK) that is required for E2-induced axogenesis in cultured neurons from male fetuses. Moreover, the Ca2+ antagonist BAPTA and the PKC inhibitor Ro 32-0432 completely abolished the neuritogenic effect of E2.  In order to investigate if PKC and intracellular Ca2+ were involved in MAPK-activation, after 2 DIV hypothalamic neurones were pre-treated for 1h with Ro 32-0432 or BAPTA-AM, pulsed for 15 min with E2 and harvested for Western blotting. Both treatments significantly reduced pERK, indicating the confluence of signals on the MAPK pathway. We asked whether the changes in pERK were significant enough to affect transcriptional activation.  To examine this, we studied the level of CREB phosphorylation, a downstream transcription factor target of MAPK. E2 induced phosphorylation of CREB at Ser133 and the inhibition of MEK1/2 by UO126 completely blocked this effect. In summary, these results demonstrate that E2 induces axogenesis in male-hypothalamic neurons through activation of the MAPK pathway.  Concurrently, calcium signalling through activation of PKC converges onto the same pathway. ERK1/2 is phosphorylated, triggering effects on gene transcription via CREB and regulation of the cytoskeletal machinery, both required to induce axon growth.