Browsing by Author "Hetz, Claudio"

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    Lack of Activation of the Unfolded Protein Response in Mouse and Cellular Models of Niemann-Pick Type C Disease
    (2011) Klein Posternack, Andrés David; Mosqueira Montero, Matías José; Martínez, Gabriela; Robledo Plaza, Fermín Alberto; González Bustos, Marcela Paz; Caballero, Benjamín; Cancino Lobos, Gonzalo; Álvarez Rojas, Alejandra Beatriz; Hetz, Claudio; Zanlungo Matsuhiro, Silvana
    Background: Niemann-Pick type C (NPC) disease is a fatal lysosomal storage disease related to progressive neurode-generation secondary to abnormal intracellular accumulation of cholesterol. Signs of endoplasmic reticulum (ER) stress have been reported in other lipidoses. Adaptation to ER stress is mediated by the unfolded protein response (UPR), an integrated signal transduction pathway that attenuates stress or triggers apoptosis of irreversibly damaged cells. Objective: To investigate the possible engagement of ER stress responses in NPC models. Methods: We used NPC1 deficient mice and an NPC cell-based model by knocking down the expression of NPC1 to measure several UPR markers through different approaches. Results: Despite expectations that the UPR will be activated in NPC, our results indicate a lack of ER stress reactions in the cerebellum of symptomatic mice. Similarly, knocking down NPC1 in Neuro2a cells leads to clear cholesterol accumulation without evidence of UPR activation. Conclusion: Our results suggest that cholesterol overload and neuronal dysfunction in NPC is not associated with ER stress, which contrasts with recent reports suggesting the activation of the UPR in other lysosomal storage diseases. Copyright (c) 2010 S. Karger AG, Basel
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    Oxidative stress activates the c-Abl/p73 proapoptotic pathway in Niemann-Pick type C neurons
    (2010) Klein Posternack, Andrés David; Maldonado Vera, Carola Patricia; Vargas Rojas, Lina Marcela; González Bustos, Marcela Paz; Robledo Plaza, Fermín Alberto; Pérez de Arce Guzman, Karen Andrea; Muñoz, Francisco J.; Hetz, Claudio; Álvarez, Alejandra R.; Zanlungo Matsuhiro, Silvana
    Niemann-Pick type C (NPC) is a neurodegenerative disease characterized by the intralysosomal accumulation of cholesterol leading to neuronal apoptosis. We have previously reported the activation of the c-Abl/p73 proapoptotic pathway in the cerebellum of NPC mice; however, upstream signals underlying the engagement of this pathway remain unknown. Here, we investigate the possible role of oxidative stress in the activation of c-Abl/p73 using different in vitro and in vivo NPC models. Our results indicate a close temporal correlation between the appearance of nitrotyrosine (N-Tyr; a post-translational tyrosine modification caused by oxidative stress) and the activation of c-Abl/p73 in NPC models. To test the functional role of oxidative stress in NPC, we have treated NPC neurons with the antioxidant NAC and observed a dramatic decrease of c-Abl/p73 activation and a reduction in the levels of apoptosis in NPC models. In conclusion, our data suggest that oxidative stress is the main upstream stimulus activating the c-Abl/p73 pathway and neuronal apoptosis in NPC neurons.