Participación del factor de transcripción CHOP-C/EBP-β en el sistema de reparación mitocondrial UPRmt en la eritropoyesis
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Date
2016
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es
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Universidad Andrés Bello
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Abstract
Las mitocondrias son organelos esenciales para las células. Éstas cumplen variadas e importantes funciones como: el metabolismo de hierro y cobre, producción de hemo y también producción de energía en forma de ATP para la célula. Si las mitocondrias fallan, las células entran en apoptosis estimulado por la acción de las especies reactivas de oxígeno (ROS), que causan daños en la estructura mitocondrial, en su DNA y en sus proteínas. Por esto, la mitocondria tiene métodos de protección contra daños, entre ellos, los sistemas antioxidantes, proteasas triple A, ciclos de biogénesis y autofagia; y por último, el sistema de respuesta a proteínas mal plegadas mitocondrial (UPRmt). En mamíferos se sabe que este sistema, que funciona a través de proteínas chaperonas y proteasas, es activado por un heterodímero compuesto por la proteína homologa a C/EBP (CHOP) y la proteína que interactúa con CCAAT β (C/EBP-β), luego de que la proteína quinasa c-Jun N-Terminal (JNK2) sensa estrés oxidativo en el citosol Uno de los tipos celulares mamíferos que más estrés oxidativo debe soportar, es el eritroide, donde la producción de hemoglobina, causa un gran aumento de ROS en las células. Cuando la producción de hemoglobina comienza, la expresión de CHOP y C/EBP-β aumentan simultáneamente, así como las proteasas y chaperonas mitocondriales que éstas activan, como a la subunidad proteolítica de la proteasa Clp ATP-dependiente (ClpP) y la proteína Heat-shock 60 (Hsp60).
Dada la correlación entre la expresión de las proteínas del UPRmt y la producción de hemoglobina; se puede decir que la el sistema UPRmt es esencial para la diferenciación eritroide. Es por esto que se investiga, en este trabajo, la participación del sistema UPRmt en la eritropoyesis. Durante esta investigación, se determinó que la expresión de CHOP y C/EBP-β, ClpP y Hsp60 aumenta a medida que las células hematopoyéticas se diferencian. También se logró determinar que al silenciar, con RNA de interferencia, las proteínas involucradas en el sistema mitocondrial de proteínas mal plegadas (UPRmt), las células fueron incapaces de alcanzar las etapas finales de la diferenciación. Mientras que a nivel mitocondrial, se provocan bajas en la respiración celular y en el potencial de membrana, aceleración del recambio mitocondrial, aumentos en el estrés oxidativo y en la apoptosis. Esto hace concluir que cuando aumenta el estrés en la mitocondria, la participación del heterodímero CHOP-C/EBP-β en la activación del UPRmt es esencial para la diferenciación eritroide.
Mitochondria are essential organelles for the cells, these organelles performs varied and important functions like: Copper and iron metabolism, heme production, and also energy production in form of ATP, for the cell. If mitochondria fail, cells undergo apoptosis, which occurs by the action of reactive oxygen species (ROS) that cause damage in the mitochondrial structure, DNA and proteins. Because of this, mitochondria have protection methods against damage, such as the antioxidant systems, the triple A proteases, the biogenesis and autophagy cycle and ultimately, the mitochondrial unfolded protein response (UPRmt). In mammals, is known that this system, working through chaperones and proteases, is activated by a heterodimer composed of the C/EBP homolog protein (CHOP) and CCAAT-β interacting protein (C/EBP-β), after the c-Jun N-Terminal protein kinase 2 (JNK2) senses oxidative stress in the mitochondrial matrix. One of the cell types that bears most of oxidative stress is the erythroid type, where the production of hemoglobin causes a great increase in intracellular ROS. When the production of hemoglobin starts, the expression of CHOP and C/EBP-β increases simultaneously, as well as the mitochondrial proteases like ATP-dependent Clp protease proteolytic subunit (ClpP) and chaperones like Heat shock protein 60 (Hsp60). Given this correlation between expression of the UPRmt proteins and the hemoglobin production; it can be said that the UPRmt system is essential for erythroid differentiation. For this reason this work studies the participation of the UPRmt system in erythropoiesis. During this investigation it was determined that expression of CHOP and C/EBP-β and also the expression of ClpP and Hsp60, increases when hematopoietic cells differentiate. Also we determined that when the proteins involved in the UPRmt are silenced with siRNA, the cells were incapable of reaching the final phases of differentiation. At the mitochondrial level, silencing caused low respiration index, and low membrane potential, as well as faster mitochondrial turnover, increased oxidative stress and increased apoptosis. This make conclude when there is an increase in mitochondria stress, the participation of the heterodimer CHOP-C/EBP-β in the activation of the UPRmt is essential for erythroid differentiation.
Mitochondria are essential organelles for the cells, these organelles performs varied and important functions like: Copper and iron metabolism, heme production, and also energy production in form of ATP, for the cell. If mitochondria fail, cells undergo apoptosis, which occurs by the action of reactive oxygen species (ROS) that cause damage in the mitochondrial structure, DNA and proteins. Because of this, mitochondria have protection methods against damage, such as the antioxidant systems, the triple A proteases, the biogenesis and autophagy cycle and ultimately, the mitochondrial unfolded protein response (UPRmt). In mammals, is known that this system, working through chaperones and proteases, is activated by a heterodimer composed of the C/EBP homolog protein (CHOP) and CCAAT-β interacting protein (C/EBP-β), after the c-Jun N-Terminal protein kinase 2 (JNK2) senses oxidative stress in the mitochondrial matrix. One of the cell types that bears most of oxidative stress is the erythroid type, where the production of hemoglobin causes a great increase in intracellular ROS. When the production of hemoglobin starts, the expression of CHOP and C/EBP-β increases simultaneously, as well as the mitochondrial proteases like ATP-dependent Clp protease proteolytic subunit (ClpP) and chaperones like Heat shock protein 60 (Hsp60). Given this correlation between expression of the UPRmt proteins and the hemoglobin production; it can be said that the UPRmt system is essential for erythroid differentiation. For this reason this work studies the participation of the UPRmt system in erythropoiesis. During this investigation it was determined that expression of CHOP and C/EBP-β and also the expression of ClpP and Hsp60, increases when hematopoietic cells differentiate. Also we determined that when the proteins involved in the UPRmt are silenced with siRNA, the cells were incapable of reaching the final phases of differentiation. At the mitochondrial level, silencing caused low respiration index, and low membrane potential, as well as faster mitochondrial turnover, increased oxidative stress and increased apoptosis. This make conclude when there is an increase in mitochondria stress, the participation of the heterodimer CHOP-C/EBP-β in the activation of the UPRmt is essential for erythroid differentiation.
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Tesis (Ingeniero en Biotecnología)
Keywords
Mitocondrias, Factores de Transcripción, Eritropoyesis