Miostatina inhibe la vía de señalización IGF-1/PI3K/PLCγ/NFATc3 a través del receptor Activina tipo IB (ActRIB)
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2017
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es
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Universidad Andrés Bello
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Miostatina, un miembro de la familia TGF-β, es una proteína expresada principalmente en el músculo esquelético que cumple un rol inhibidor en la proliferación y diferenciación de células musculares. Miostatina ejerce su acción a través de un complejo de receptores Activina, los cuales median la actividad de los factores de transcripción Smads encargados de regular negativamente el proceso miogénico. Sin embargo, en los últimos años han surgido antecedentes que demuestran que la inhibición del proceso de diferenciación de células musculares por miostatina puede ser regulado de manera independiente a la actividad de los factores de transcripción Smads.
Estudios realizados por nuestro grupo de laboratorio han mostrado que IGF-1 es capaz de inducir de manera transitoria la liberación de calcio desde reservorios intracelulares a través de un mecanismo que involucra la actividad de la PI3K y la PLC. Complementariamente determinamos que la preincubación con miostatina inhibió significativamente la liberación de calcio inducida por IGF-1. Esta observación nos lleva a formular la pregunta acerca de qué mecanismos median la inhibición de liberación de calcio inducida por IGF-1, surgiendo como un candidato el receptor Activina tipo IB. Si bien no existen antecedentes reportados de una interacción entre el receptor Activina tipo IB y componentes de la vía de IGF-1, sí existen reportes de la modulación de la actividad PI3K por parte de receptores de la familia TGF-En base a esto se postuló la siguiente hipótesis de trabajo “El receptor para miostatina Activina tipo IB modula negativamente la vía de señalización IGF-1/PI3K/PLC/NFATc3”. Para comprobar esta hipótesis se determinó el efecto de miostatina en la vía para IGF-1 usando las herramientas de western blot y vector reportero en mioblastos. Para demostrar la participación directa del receptor ActRIB, se realizaron ensayos de knock-down con siRNA para receptores de Activina tipo IB y finalmente se evaluó la interacción mediante inmunoprecipitación de ActRIB y componentes de la vía de IGF-1. Los resultados obtenidos sugieren que el receptor para miostatina se une a la subunidad p85 de la PI3K modulando su actividad, así como la regulación de los demás elementos de la vía de IGF-1. La información obtenida de este proyecto revela aspectos desconocidos de la vía de señalización de miostatina.
Myostatin, a member of the TGF-β family is a protein expressed mainly in the skeletal muscle that plays an inhibitory role in the proliferation and differentiation of muscle cells. Myostatin exerts its actions through a complex of activin receptors, which mediate the activity of Smads transcription factors responsible for down regulation of myogenic processes. However, in recent years there have been studies that show that the inhibition of the differentiation process of muscle cells by myostatin can be regulated independently of the activity of the Smads transcription factors. Studies by our group have shown that IGF-1 induces in a transient manner the release of calcium from intracellular stores via a mechanism that involves PI3K and PLC activity. In addition, we determined that preincubation with myostatin significantly inhibited the release of calcium induced by IGF-1. This observation leads us to ask which mechanism mediates the inhibition of calcium release induced by IGF-1 emerging as a candidate the activin receptor type IB. While there are no reports about the interaction between the activin receptor type IB and components of the IGF-1 signaling pathway, there are reports regarding the modulation of PI3K activity by receptors of the TGF-β family. Based on these observations we proposed the following hypothesis “The myostatin receptor, activin type IB negatively modulates the IGF-1/PI3K/PLC/NFATc3 signaling pathway”. To test this hypothesis, we studied the effect of myostatin on the IGF-1 pathway by western blotting and luciferase reporter vector in skeletal myoblasts. To demonstrate a direct participation of the activin receptor type IB, siRNA knock-down was tested for the activin type IB receptor. Finally, the interaction between the activin type IB receptor and components of the IGF-1 pathway was determined by immunoprecipitation. The information obtained in this project reveals unknown aspects of the myostatin signaling pathway
Myostatin, a member of the TGF-β family is a protein expressed mainly in the skeletal muscle that plays an inhibitory role in the proliferation and differentiation of muscle cells. Myostatin exerts its actions through a complex of activin receptors, which mediate the activity of Smads transcription factors responsible for down regulation of myogenic processes. However, in recent years there have been studies that show that the inhibition of the differentiation process of muscle cells by myostatin can be regulated independently of the activity of the Smads transcription factors. Studies by our group have shown that IGF-1 induces in a transient manner the release of calcium from intracellular stores via a mechanism that involves PI3K and PLC activity. In addition, we determined that preincubation with myostatin significantly inhibited the release of calcium induced by IGF-1. This observation leads us to ask which mechanism mediates the inhibition of calcium release induced by IGF-1 emerging as a candidate the activin receptor type IB. While there are no reports about the interaction between the activin receptor type IB and components of the IGF-1 signaling pathway, there are reports regarding the modulation of PI3K activity by receptors of the TGF-β family. Based on these observations we proposed the following hypothesis “The myostatin receptor, activin type IB negatively modulates the IGF-1/PI3K/PLC/NFATc3 signaling pathway”. To test this hypothesis, we studied the effect of myostatin on the IGF-1 pathway by western blotting and luciferase reporter vector in skeletal myoblasts. To demonstrate a direct participation of the activin receptor type IB, siRNA knock-down was tested for the activin type IB receptor. Finally, the interaction between the activin type IB receptor and components of the IGF-1 pathway was determined by immunoprecipitation. The information obtained in this project reveals unknown aspects of the myostatin signaling pathway
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