RESUMEN
The pattern of dendritic branching, together with the density of synapses and receptor composition, defines the electrical properties of a neuron. The development of the dendritic arbor and its additional stabilization are highly orchestrated at the molecular level and are guided by intrinsic mechanisms and extracellular information. Although protein translation is known to contribute to these processes, the role of its local component has not been fully explored. For local translation, mRNAs are transported to dendrites in their dormant form as ribonucleoparticles (RNPs). We hypothesized that disturbing spatial mRNA distribution via RNP targeting may result in severe underdevelopment of the dendritic arbor. Zipcode binding protein 1 (ZBP1) controls ß-actin mRNA transport and translation in dendrites. We showed that proper cellular levels of ZBP1, its ability to engage in mRNA binding, and Src-dependent release of mRNA cargo from ZBP1 are vital for dendritic arbor development in cultured rat hippocampal neurons. Moreover, ß-actin overexpression significantly alleviated the effects of ZBP1 knockdown. These results suggest that ZBP1-dependent dendritic mRNA transport contributes to proper dendritic branching.
Asunto(s)
Dendritas/fisiología , Hipocampo/citología , Neuronas/citología , Proteínas de Unión al ARN/metabolismo , Actinas/genética , Actinas/metabolismo , Animales , Transporte Biológico/genética , Células COS , Células Cultivadas , Chlorocebus aethiops , Dendritas/metabolismo , Embrión de Mamíferos , Regulación de la Expresión Génica/genética , Proteínas Fluorescentes Verdes/genética , Mutación/genética , Neuronas/ultraestructura , Fosforilación , ARN Mensajero/metabolismo , ARN Interferente Pequeño/genética , ARN Interferente Pequeño/metabolismo , Proteínas de Unión al ARN/genética , Ratas , Ratas Wistar , Ribonucleoproteínas/genética , Ribonucleoproteínas/metabolismo , Estadísticas no Paramétricas , Factores de Tiempo , Transfección , Tirosina/genética , Tirosina/metabolismoRESUMEN
Local protein synthesis occurs in axons and dendrites of neurons, enabling fast and spatially restricted responses to a dynamically changing extracellular environment. Prior to local translation, mRNA that is to be translated is packed into ribonucleoprotein particles (RNPs) where RNA binding proteins ensure mRNA silencing and provide a link to molecular motors. ZBP1 is a component of RNP transport particles and is known for its role in the local translation of ß-actin mRNA. Its binding to mRNA is regulated by tyrosine 396 phosphorylation, and this particular modification was shown to be vital for axonal growth and dendritic branching. Recently, additional phosphorylation of ZBP1 at serine 181 (Ser181) was described in non-neuronal cells. In the present study, we found that ZBP1 is also phosphorylated at Ser181 in neurons in a mammalian/mechanistic target of rapamycin complex 2-, Src kinase-, and mRNA binding-dependent manner. Furthermore, Ser181 ZBP1 phosphorylation was essential for the proper dendritic branching of hippocampal neurons that were cultured in vitro and for the proper ZBP1 dendritic distribution and motility.