RESUMEN
Defective heme synthesis may cause acute porphyrias, which are associated with a wide array of neurological disturbances involving both the central and peripheral nervous systems. Thus, the understanding of the roles of heme in neuronal cell function may provide insights into the molecular events underlying the pathogenesis of neuropathies associated with defective heme synthesis. In this report, we use rat pheochromocytoma (PC12) clonal cells as a model system for studying the role of heme in neuronal cell survival. We examined the effects of inhibition of heme synthesis on signaling pathways and gene expression in nerve growth factor (NGF)-induced PC12 cells. We found that succinyl acetone-induced heme deficiency selectively caused apoptosis in NGF-induced PC12 cells. Further, we found that in succinyl acetone-treated, NGF-induced cells, the pro-survival Ras-ERK1/2 signaling pathway was inactivated and the pro-apoptotic JNK signaling pathway was activated. In these cells, the activation of caspase and the cleavage of nuclear poly (ADP-ribose) polymerase (PARP) were also evident. Importantly, microarray gene expression analysis showed that more than 20 key neuronal genes that were induced by NGF were suppressed by succinyl acetone. These genes include those encoding survival motor neuron protein, synaptic vesicle protein SVOP, and neural cell adhesion molecule NCAM. These results indicate that heme is important for neuronal cell signaling and the proper functioning of neuronal cells.
Asunto(s)
Apoptosis/genética , Regulación Enzimológica de la Expresión Génica/genética , Hemo/deficiencia , Degeneración Nerviosa/genética , Neuronas/metabolismo , Porfirias/complicaciones , Animales , Apoptosis/efectos de los fármacos , Caspasas/efectos de los fármacos , Caspasas/metabolismo , Supervivencia Celular/efectos de los fármacos , Supervivencia Celular/genética , Colágeno Tipo XI/efectos de los fármacos , Colágeno Tipo XI/metabolismo , Proteína de Unión a Elemento de Respuesta al AMP Cíclico/efectos de los fármacos , Proteína de Unión a Elemento de Respuesta al AMP Cíclico/genética , Proteína de Unión a Elemento de Respuesta al AMP Cíclico/metabolismo , Regulación hacia Abajo/efectos de los fármacos , Regulación hacia Abajo/fisiología , Inhibidores Enzimáticos , Regulación Enzimológica de la Expresión Génica/efectos de los fármacos , Hemo/biosíntesis , Heptanoatos , Sistema de Señalización de MAP Quinasas/efectos de los fármacos , Sistema de Señalización de MAP Quinasas/fisiología , Proteínas de la Membrana/efectos de los fármacos , Proteínas de la Membrana/genética , Proteínas de la Membrana/metabolismo , Degeneración Nerviosa/metabolismo , Degeneración Nerviosa/fisiopatología , Proteínas del Tejido Nervioso/efectos de los fármacos , Proteínas del Tejido Nervioso/genética , Proteínas del Tejido Nervioso/metabolismo , Moléculas de Adhesión de Célula Nerviosa/efectos de los fármacos , Moléculas de Adhesión de Célula Nerviosa/genética , Moléculas de Adhesión de Célula Nerviosa/metabolismo , Neuronas/efectos de los fármacos , Neuronas/patología , Células PC12 , Poli(ADP-Ribosa) Polimerasa-1 , Poli(ADP-Ribosa) Polimerasas , Porfirias/metabolismo , Porfirias/fisiopatología , ARN Mensajero/efectos de los fármacos , ARN Mensajero/metabolismo , Proteínas de Unión al ARN/efectos de los fármacos , Proteínas de Unión al ARN/genética , Proteínas de Unión al ARN/metabolismo , Ratas , Proteínas del Complejo SMN , Regulación hacia Arriba/efectos de los fármacos , Regulación hacia Arriba/fisiología , Proteínas de Transporte Vesicular/efectos de los fármacos , Proteínas de Transporte Vesicular/genética , Proteínas de Transporte Vesicular/metabolismoRESUMEN
Defective heme synthesis in mammals has been suspected of causing neuropathy associated with porphyrias and lead poisoning. To determine the molecular action of heme in neuronal cells, we examined the effect of the inhibition of heme synthesis on nerve growth factor (NGF) signaling in PC12 cells. We found that the inhibition of heme synthesis by succinyl acetone interferes with NGF-induced neurite outgrowth in PC12 cells. Furthermore, we show that heme deficiency obliterates the activation of the signaling intermediates of the Ras-mitogen-activated protein kinase signaling pathway and its downstream target, the transcription activator cyclic AMP response element-binding protein. Strikingly, microarray expression analysis shows that the inhibition of heme synthesis selectively diminishes the induction of expression of a subset of neuron-specific genes by NGF, such as Ras and neurofilament proteins, whereas NGF induces the expression of several major classes of neuronal genes that encode regulatory and structural proteins at three days after induction. Our data provide insights into how heme deficiency interferes with NGF signaling and abrogates programs of neuronal gene expression, thus ultimately causing defective neuronal functions.