DCC Mediates Phosphorylation Of Dab1 Induced By Netrin-1

The development processes of mammalian neocortical involve the proliferation,differentiation of neural progenitor cells,migration to specific position,synaptic establishment and myelination,resulting in lamellar structures with different functions.The process includes a series of complex regulatory mechanisms to ensure that the developmental stages are carried out in an orderly and precise manner.The neuronal migration relies on the different neurons choosing the appropriate migration pattern,as well as the delicate transformation of the migration pattern.The correct position of neurons is critical to ensuring their functions,and the abnormalities of the migration processes could lead to a series of neurodevelopmental dysfunctions,including the entire brain malformations such as agyria;and neurobehavioral abnormalities such as autism.At the postnatal stage,neuronal migration plays a very important role in the maintenance of the adult brain’s neural circuit.Therefore,the exploration of the molecular mechanism on the neuronal migration is very important to understand cortical neurodevelopment.Netrin-1 is a guidance cues for neuronal axon,which plays important roles in the migration of cortical neurons and axon growth in the developing nervous system,and promotes the transition from multipolar to bipolar morphology and the tangential migration of the interneurons.DCC acts as a receptor for Netrin-1,which also plays a regulatory role in axonal guidance.We have confirmed that DCC plays an important role in the migration and localization of cortical neurons at previous research.Here we report that DCC silence can shorten the numbers and the lengths of neurites.It is revealed that DCC not only plays a leading role in the process of neuronal axons crossing the cortical midline,but also affects the morphological development of neurons.To explore the molecular mechanism that DCC regulates neuron growth,we find that the phosphorylation level of Dab1 at the 232 tyrosine site was enhanced after Netrin-1 stimulated in neuron.Fyn is the major kinase that regulates Dab1 in the Netrin-1 signaling pathway,and Fyn regulates the phosphorylation of the Dab1Y232 site,independent of the phosphorylation of the Dab1Y185 and Y198 sites.It is well known that Dab1 acts as an intracellular adaptor protein in the Reelin signaling pathway,and Dab1 interacts with other proteins through its phosphorylation of tyrosine sites and PTB domain,which in turn mediate the corresponding physiological functions.Importantly,the Dab1-Y232 is also the site phosphorylated in Reelin signaling and has been confirmed in this study.We then explore the molecular mechanism by which Netrin-1 regulates the phosphorylation of Dab1,and the possible interactive components of the Netrin-1 and Reelin signaling pathways.We demonstrate that DCC mediates Dab1 phosphorylation regulated by Netrin is unidirectional.Reelin cannot regulate the key components of the Netrin-1 signaling conversely.Thus,we conclude Dab1 phosphorylation is performed by Netrin-1-DCC specifically,rather than by the common components of the two signaling pathways.