Axogenic effect of estrogen in male rat hypothalamic neurons involves Ca2+, PKC and ERK signaling

CAMBIASSO, M.J., GOROSITO S.V

Villa Gualino, Torino, Italia

Congreso; IV Meeting Steroids and Nervous System; 2007

CONSEJO SUPERIOR DE INVESTIGACIONES CIENTIFICAS

17-b-estradiol (E2) stimulates the growth of axons in male derived hypothalamic neurons in vitro [3,4]. This effect is not exerted through the classical intracellular oestrogen receptor (ER) but depends on a membrane mechanism [2] in which the tyrosine kinase receptor type B participates [1,5]. More recently, we showed that E2 rapidly induced phosphorylation of the extracellular signal-regulated kinases 1/2 (ERK) mitogen-activated protein kinases (MAPK) [6]. In the present study we investigate the intracellular signaling cascades that mediate the axogenic effect of E2. Treatment with an intracellular Ca2+ chelator, a Ca2+-dependent PKC inhibitor, or two specific inhibitors of MEK-ERK pathway completely inhibited the E2-induced axogenesis. E2 and the membrane impermeant construct E2BSA rapidly induced phosphorylation of ERK, which was blocked by the specific inhibitor of ERK pathway UO126 but not by the ER antagonist ICI 182,780. Decrease of intracellular free Ca2+ or disruption of PKC activation by Ro 32-0432 attenuate ERK activation, indicating the confluence of signals in the MAPK pathway. Sub-cellular analysis of ERK demonstrated that the phospho-ERK signal is transduced to the nucleus by E2. We also have shown that E2 increased phoshorylation of CREB via ERK signaling. In summary, this study demonstrates that E2 induces axogenesis in male-hypothalamic neurons through activation of the calcium-dependent PKC and ERK pathway leading to increased CREB phosphorylation, events required to induce axon elongation.