RESUMEN
Endoplasmic reticulum (ER) stress has been implicated in the pathogenesis of CNS diseases such as Alzheimer's disease, Parkinson's disease, and cerebral ischemia. In the present study, we found that Akt activation is regulated dually by ER stress in primary cultured glial cells. We observed that Akt activation was increased by short-term exposure to ER stress but was down-regulated by long-term exposure to ER stress. ER stress-induced Akt activation was mediated through phosphatidylinositol 3-kinase (PI3K) because the PI3K inhibitors, LY294002 and wortmannin, inhibited Akt activation. Moreover, Akt was localized in the ER, as assessed by immunohistochemistry, and ER stress increased microsomally localized Akt activation. These results suggest that Akt plays an important role in stress conditions, which impair ER function.
Asunto(s)
Retículo Endoplásmico/enzimología , Neuroglía/enzimología , Proteínas Proto-Oncogénicas c-akt/biosíntesis , Animales , Animales Recién Nacidos , Encéfalo/citología , Células Cultivadas , Regulación hacia Abajo , Retículo Endoplásmico/efectos de los fármacos , Activación Enzimática , Inmunohistoquímica , Ratones , Ratones Endogámicos C57BL , Neuroglía/efectos de los fármacos , Fosfatidilinositol 3-Quinasas/fisiología , Inhibidores de las Quinasa Fosfoinosítidos-3 , Proteínas Proto-Oncogénicas c-akt/genética , Fracciones Subcelulares/enzimología , Tapsigargina/farmacología , Tunicamicina/farmacología , Regulación hacia ArribaRESUMEN
Endoplasmic reticulum stress contributes to several diseases such as neurodegenerative disorders and diabetes. In the previous report, we found that phosphatidylinositol 3-kinase (PI3K) down-regulation is important for inducing CHOP expression, an endoplasmic reticulum stress-induced transcription factor. In the present study, we investigated the effect of 4-(2-aminoethyl)-benzenesulfonyl fluoride (AEBSF), a serine protease inhibitor, on PI3K inhibitor-induced CHOP expression. We found that AEBSF completely inhibited PI3K inhibitor-induced CHOP expression at both mRNA and protein levels. It is suggested that AEBSF is an important drug from a pharmacological point of view and the results may have important implications for understanding endoplasmic reticulum stress-related diseases.
Asunto(s)
Inhibidores de las Quinasa Fosfoinosítidos-3 , Inhibidores de Serina Proteinasa/farmacología , Sulfonas/farmacología , Factor de Transcripción CHOP/genética , Animales , Células Cultivadas , Retículo Endoplásmico/metabolismo , Regulación de la Expresión Génica/efectos de los fármacos , Ratones , ARN Mensajero/análisis , Serina Endopeptidasas/fisiologíaRESUMEN
Stress signals that impair the function of the endoplasmic reticulum (ER) can lead to an accumulation of unfolded proteins in the ER causing cell death. Recent studies have indicated that ER stress contributes to several diseases such as neurodegenerative disorders or diabetes. In the present study, we found that Akt down-regulation is important for inducing CHOP expression, an ER stress-induced transcription factor. Treatment with tunicamycin or thapsigargin, ER stress inducers, caused dephosphorylation of Akt from 12 to 24 h and induced cell death. Interestingly, treatment with a PI3K inhibitor alone induced CHOP expression and caused cell death. However, a MEK1 inhibitor induced neither CHOP expression nor cell death. These results indicate that the inactivation of Akt by ER stress induces CHOP expression and causes cell death. Therefore, Akt plays an important role in ER stressed condition and may have important implications for understanding ER stress-related diseases.