RESUMEN
The transdifferentiation from cardiac fibroblasts to myofibroblasts is an important event in the initiation of cardiac fibrosis. However, the underlying mechanism is not fully understood. Circ-sh3rf3 (circular RNA SH3 domain containing Ring Finger 3) is a novel circular RNA which was induced in hypertrophied ventricles by isoproterenol hydrochloride, and our work has established that it is a potential regulator in cardiac hypertrophy, but whether circ-sh3rf3 plays a role in cardiac fibrosis remains unclear, especially in the conversion of cardiac fibroblasts into myofibroblasts. Here, we found that circ-sh3rf3 was down-regulated in isoproterenol-treated rat cardiac fibroblasts and cardiomyocytes as well as during fibroblast differentiation into myofibroblasts. We further confirmed that circ-sh3rf3 could interact with GATA-4 proteins and reduce the expression of GATA-4, which in turn abolishes GATA-4 repression of miR-29a expression and thus up-regulates miR-29a expression, thereby inhibiting fibroblast-myofibroblast differentiation and myocardial fibrosis. Our work has established a novel Circ-sh3rf3/GATA-4/miR-29a regulatory cascade in fibroblast-myofibroblast differentiation and myocardial fibrosis, which provides a new therapeutic target for myocardial fibrosis.
Asunto(s)
Cardiomiopatías , Fibroblastos , Fibrosis , Miofibroblastos , ARN Circular , Animales , Ratas , Cardiomiopatías/genética , Cardiomiopatías/metabolismo , Cardiomiopatías/patología , Diferenciación Celular/genética , Diferenciación Celular/fisiología , Fibroblastos/metabolismo , Fibrosis/genética , Fibrosis/metabolismo , MicroARNs/genética , MicroARNs/metabolismo , Miocitos Cardíacos/metabolismo , Miofibroblastos/metabolismo , ARN Circular/genética , ARN Circular/metabolismo , Ubiquitina-Proteína Ligasas/genética , Ubiquitina-Proteína Ligasas/metabolismoRESUMEN
GATA-4 is an important transcription factor involved in several developmental processes of the heart, such as cardiac myocyte proliferation, differentiation and survival. The precise mechanisms underlying the regulation of GATA-4 remain unclear, this is especially true for the mechanisms that mediate the post-transcriptional regulation of GATA-4. Here, we demonstrate that miR-200b, a member of the miR-200 family, is a critical regulator of GATA-4. Overexpression of miR-200b leads to the downregulation of GATA-4 mRNA and a decrease in GATA-4 protein levels. Moreover, miR-200b not only inhibits cell growth and differentiation but also reverses the growth response mediated by GATA-4, whereas depletion of miR-200b leads to a slight reversal of the anti-growth response achieved by knocking down endogenous GATA-4. More importantly, the cell cycle-associated gene cyclin D1, which is a downstream target of GATA-4, is also regulated by miR-200b. Thus, miR-200b targets GATA-4 to downregulate the expression of cyclin D1 and myosin heavy chain (MHC), thereby regulating cell growth and differentiation.
Asunto(s)
Ciclo Celular/genética , Factor de Transcripción GATA4/genética , Regulación de la Expresión Génica , MicroARNs/metabolismo , Animales , Apoptosis/genética , Ciclo Celular/fisiología , Puntos de Control del Ciclo Celular/genética , Diferenciación Celular/genética , Diferenciación Celular/fisiología , Línea Celular , Línea Celular Tumoral , Proliferación Celular , Ciclina D1/genética , Ciclina D1/metabolismo , Factor de Transcripción GATA4/metabolismo , Humanos , Ratones , MicroARNs/genética , Desarrollo de Músculos/genética , Miocitos Cardíacos/metabolismo , Cadenas Pesadas de Miosina/genética , Cadenas Pesadas de Miosina/metabolismoRESUMEN
Terminal differentiation failure is an important cause of rhabdomyosarcoma genesis, however, little is known about the epigenetic regulation of aberrant myogenic differentiation. Here, we show that GATA-4 recruits polycomb group proteins such as EZH2 to negatively regulate miR-29a in undifferentiated C2C12 myoblast cells, whereas recruitment of GRIP-1 to GATA-4 proteins displaces EZH2, resulting in the activation of miR-29a during myogenic differentiation of C2C12 cells. Moreover, in poorly differentiated rhabdomyosarcoma cells, EZH2 still binds to the miR-29a promoter with GATA-4 to mediate transcriptional repression of miR-29a. Interestingly, once re-differentiation of rhabdomyosarcoma cells toward skeletal muscle, EZH2 was dispelled from miR-29a promoter which is similar to that in myogenic differentiation of C2C12 cells. Eventually, this expression of miR-29a results in limited rhabdomyosarcoma cell proliferation and promotes myogenic differentiation. We thus establish that GATA-4 can function as a molecular switch in the up- and downregulation of miR-29a expression. We also demonstrate that GATA-4 acts as a tumor suppressor in rhabdomyosarcoma partly via miR-29a, which thus provides a potential therapeutic target for rhabdomyosarcoma.
Asunto(s)
MicroARNs , Rabdomiosarcoma Embrionario , Rabdomiosarcoma , Animales , Ratones , Diferenciación Celular/genética , Proliferación Celular/genética , Proteína Potenciadora del Homólogo Zeste 2/genética , Proteína Potenciadora del Homólogo Zeste 2/metabolismo , Epigénesis Genética , MicroARNs/metabolismo , Mioblastos , Rabdomiosarcoma/patología , Rabdomiosarcoma Embrionario/patologíaRESUMEN
Peroxisome proliferator-activated receptor α (PPARα) is a nuclear hormone receptor that regulates energy metabolism, but its precise mechanisms remain unknown. Here, we demonstrate that the PPARα agonist fenofibrate activated expression of the glucose transporter Glut4. Moreover, PPARα was associated with the Glut4 promoter through GATA sites upon fenofibrate stimulation in cardiomyocytes. This occupancy is achieved through an interaction between amino acids 1-136 of PPARα with amino acids 276-443 of the cardiac transcription factor GATA-6. In addition, the interaction of PPARα with GATA-6 activated Glut4 gene expression, improved glucose consumption, and enhanced activity of mitochondrial citrate synthase in C2C12 myoblasts; both mutants of PPARα (1-101 aa) and GATA-6 (227-331 aa) were unable to cooperate in Glut4 activation. Thus, GATA-6 is an important component of the transcription network required for energy metabolism mediated by PPARα, and these findings provide a molecular basis for understanding the role of GATA-6 proteins in muscle development and disease.