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Drosophila melanogaster , as a model system to study the cell biology of neuronal GPCRs
Anne-Lise Gaffuri, doctorante - Ph.D student Crédits : ESPCI ParisTechThe type-1 cannabinoid receptor (CB1R), the neuronal receptor for the major psychoactive substance of marijuana, is one of the most abundant G-protein coupled receptors in the mammalian central nervous system. CB1R is traditionally described as a presynaptic receptor that retrogradely regulates synaptic transmission. In addition to this now relatively well-characterized function, in the last two decades it has become widely recognized that endocannabinoid (eCB) actions in the brain are not limited to the regulation of neurotransmission at established adult synapses. Indeed, eCB and CB1R are now recognized to be involved in brain development at the synaptic, neuronal and network levels.
However, precise mechanisms underlying these processes remain poorly described. Since cellular mechanisms that mediate CB1R-activition dependent neuronal remodeling and subneuronal targeting have been demonstrated to be cell-autonomous, we aimed to combine the power of Drosophila genetics with the experimental accessibility and single-cell resolution of low-density primary neuronal cultures, a tool currently lacking in Drosophila. Moreover, because Drosophila does not have a CB1R ortholog, CB1R cell biology may be observed independently from eCB machinery.
Thus, we first developed and validated an in vitro culture protocol that yields mature and fully differentiated Drosophila neurons.
Secondly, we showed that activation-dependent endocytosis of ectopically expressed CB1R is conserved in Drosophila neurons.
Next, we investigated whether ectopic expression and activation of CB1R in Drosophila modulate neuronal development.
As observed in mammals, we observed that activation of CB1R impairs dendritogenesis in a cell-autonomous manner. For further characterization of our model, we showed that, as with mammals, transient ectopic CB1R expression and activation in mushroom body neurons (the center of olfactory memory in Drosophila) modulate the formation of a consolidated form of aversive memory.
In conclusion, the validation of this new animal model opens new perspectives to better characterize mechanisms underlying modulation of neuronal functions induced by CB1R activity.