Kinesin­1 is required for axonal pathfinding and cannabinoid­induced axonal development by mediating the axonal transport of CB1 receptor.

TMM SAEZ; M ALLOATTI; TL FALZONE; LE CROMBERG; DM GELMAN; MG OTERO; VM POZO DEVOTO

San Diego

Congreso; 46th Annual Meeting of the Society for Neuroscience.; 2016

Society for Neuroscience.

During development, axonal navigation through the intricate architecture of the brain depends on the proper presentation and positioning of guidance receptors, which allow for the correct reading of external clues. Receptors for axonal growth and guidance are shifted to axons and localized in growth cones, where they are activated by attractive or repulsive guidance cues resulting in axonal pathfinding decisions. However, little is known about the crucial mechanisms controlling the proper trafficking of these receptors involved in neural circuits wiring. The endocannabinoid (eCB) system has been identified as an important regulator of axonal outgrowth and pathfinding. eCBs mediate the motility and directional turning of axons by activating type 1 cannabinoid receptor (CB1R) in the axonal growth cone. Although cargo delivery mediated by molecular motors is essential in developing neurons, the mechanism underlying the directional axonal transport of CB1R remains basically unknown. To test the hypothesis that CB1R delivery to the growth cone depends on kinesin-1 mediated axonal transport, we used mice lacking the kinesin light chain 1 (klc1) subunit of the anterograde motor kinesin-1. We performed L1-NCAM staining and axon-tracing experiments in developing klc1-/- brains and found pathfinding defects in corticothalamic and thalamocortical axonal tracts, which resemble those in CB1R knockout mice. Using live imaging of fluorescent CB1R tagged vesicles in wildtype and klc1-/- neurons, we revealed the dependency of Kinesin-1 in CB1R transport towards the axonal growth cone. Next, to assess the role of kinesin-1 on CB1R-mediated axonal development, primary cortical cultures of wildtype and klc1-/- neurons were treated with pharmacologic modulators of the CB1R (WIN55-212,22, ACEA and AM251). We demonstrated that kinesin-1 is required for the correct axonal growth cone remodeling and outgrowth-induced by CB1R agonist and antagonist. Altogether, our results suggest that kinesin-1-mediated axonal transport of CB1R is required for a normal eCB signaling and is also required for proper axonal pathfinding.