AXOTRANSMAP · Assembling a functional map of axonal signalling endosomes

The polarisation of neurons in somatodendritic and axonal compartments allows signal propagation over long distances. Despite the important role played by electrical signals, fast axonal transport is crucial for long-range communication between the soma and distal synapses, which is carried out by vesicular transport mechanisms. Neurotrophins and their receptors are internalised at axon terminals by clathrin-mediated endocytosis and conveyed by signalling endosomes to the soma, where they activate transcriptional responses regulating neuronal homeostasis and survival. However, little is known about the identity and the dynamics of the organelles involved.The aim of my project is to build a functional and physical map of axonal retrograde carriers in specific neuronal types, which are the target of important human diseases. For this purpose, I will exploit a new developed affinity purification strategy using the binding fragment of tetanus neurotoxin (HC) conjugated to monocrystalline iron oxide nanoparticles (MIONs).At different time points after internalisation, retrograde carriers will be magnetically purified and submitted to mass-spectrometry analysis. The kinetics of endosomal maturation will be assessed using quantitative label-free SILAC protocols. These results will uncover new components of signalling endosomes and identify dysfunctions of this pathway that are at the basis of motor and sensory neuropathies.