RESUMEN
The estrogen receptor (ER) subtypes, ERalpha and ERbeta, modulate numerous signaling cascades in the brain to result in a variety of cell fates including neuronal differentiation. We report here that 17beta-estradiol (E2) rapidly stimulates the autophosphorylation of alpha-Ca(2+)/calmodulin-dependent kinase II (alphaCaMKII) in immortalized NLT GnRH neurons, primary hippocampal neurons, and Cos7 cells co-transfected with ERalpha and alphaCaMKII. The E2-induced alphaCaMKII autophosphorylation is ERalpha- and Ca(2+)/calmodulin (CaM)-dependent. Interestingly, the hormone-dependent association of ERalpha with alphaCaMKII attenuates the positive effect of E2 on alphaCaMKII autophosphorylation, suggesting that ERalpha plays a complex role in modulating alphaCaMKII activity and may function to fine-tune alphaCaMKII-triggered signaling events. However, it appears as though the activating signal of E2 dominates the negative effect of ER since there is a clear, positive downstream response to E2-activated alphaCaMKII; pharmacological inhibitors and RNAi technology show that targets of ERalpha-mediated alphaCaMKII signaling include extracellular signal-regulated kinase 1/2 (ERK1/2), cAMP response element-binding protein (CREB), and microtubule associated protein 2 (MAP2). These findings suggest a novel model for the modulation of alphaCaMKII signaling by ERalpha, which provides a molecular link as to how E2 might influence brain function.
Asunto(s)
Quinasa de la Proteína Quinasa Dependiente de Calcio-Calmodulina/metabolismo , Receptor alfa de Estrógeno/metabolismo , Transducción de Señal/fisiología , Animales , Autorradiografía , Calcio/metabolismo , Quinasa de la Proteína Quinasa Dependiente de Calcio-Calmodulina/genética , Células Cultivadas , Chlorocebus aethiops , Relación Dosis-Respuesta a Droga , Interacciones Farmacológicas , Embrión de Mamíferos , Inhibidores Enzimáticos/farmacología , Estradiol/farmacología , Receptor alfa de Estrógeno/genética , Regulación de la Expresión Génica/efectos de los fármacos , Regulación de la Expresión Génica/fisiología , Hipocampo/citología , Ratones , Mutación/fisiología , Proteínas del Tejido Nervioso/metabolismo , Neuronas/citología , Neuronas/efectos de los fármacos , Neuronas/metabolismo , ARN Interferente Pequeño/farmacología , Transducción de Señal/efectos de los fármacos , Fracciones Subcelulares/efectos de los fármacos , Fracciones Subcelulares/metabolismo , Transfección/métodosRESUMEN
The steroid hormone receptors are characterized by binding to relatively rigid, inflexible endogenous steroid ligands. Other members of the nuclear receptor superfamily bind to conformationally flexible lipids and show a corresponding degree of elasticity in the ligand-binding pocket. Here, we report the X-ray crystal structure of the oestrogen receptor alpha (ERalpha) bound to an oestradiol derivative with a prosthetic group, ortho- trifluoromethlyphenylvinyl, which binds in a novel extended pocket in the ligand-binding domain. Unlike ER antagonists with bulky side groups, this derivative is enclosed in the ligand-binding pocket, and acts as a potent agonist. This work shows that steroid hormone receptors can interact with a wider array of pharmacophores than previously thought through structural plasticity in the ligand-binding pocket.