Dynamic remodeling of ribosomes and endoplasmic reticulum in axon terminals of motoneurons
In neurons, endoplasmic reticulum forms a highly dynamic network that enters axons and presynaptic terminals and plays a central role in Ca2+ homeostasis and synapse maintenance. However, the underlying mechanisms involved in regulation of its dynamic remodeling as well as its function in axon development and presynaptic differentiation remain elusive. Here, we used high resolution microscopy and live cell imaging to investigate rapid movements of endoplasmic reticulum and ribosomes in axons of cultured motoneurons after stimulation with Brain-derived neurotrophic factor. Our results indicate that the endoplasmic reticulum extends into axonal growth cone filopodia where its integrity and dynamic remodeling are regulated mainly by actin and its motor protein myosin VI. Additionally, we found that in axonal growth cones, ribosomes assemble into 80S subunits within seconds and associate with ER in response to extracellular stimuli which describes a novel function of axonal ER in dynamic regulation of local translation. Summary statementIn axonal growth cones of motoneurons, dynamic remodeling of ER is coordinated through drebrin A-mediated actin and microtubule crosstalk and contributes to local translation as response to BDNF stimulation.