Rab43 GTPase directs postsynaptic trafficking and neuron-specific sorting of G protein-coupled receptors

G protein-coupled receptors (GPCRs) are important modulators of synaptic functions. A fundamental but poorly addressed question in neurobiology is how targeted GPCR trafficking is achieved. Rab GTPases are the master regulators of vesicle-mediated membrane trafficking, but their functions in the synaptic presentation of newly synthesized GPCRs are virtually unknown. Here, we investigate the role of Rab43, via dominant-negative inhibition and CRISPR-Cas9-mediated KO, in the export trafficking of alpha 2-adrenergic receptor (alpha 2-AR) and muscarinic acetylcholine receptor (mAChR) in primary neurons and cells. We demonstrate that Rab43 differentially regulates the overall surface expression of endogenous alpha(2)-AR and mAChR, as well as their signaling, in primary neurons. In parallel, Rab43 exerts distinct effects on the dendritic and postsynaptic transport of specific alpha(2B)-AR and M3 mAChR subtypes. More interestingly, the selective actions of Rab43 toward alpha(2B)-AR and M3 mAChR are neuronal cell specific and dictated by direct interaction. These data reveal novel, neuronspecific functions for Rab43 in the dendritic and postsynaptic targeting and sorting of GPCRs and imply multiple forward delivery routes for different GPCRs in neurons. Overall, this study provides important insights into regulatory mechanisms of GPCR anterograde traffic to the functional destination in neurons.

Automated summary

The study reveals that Rab43 plays a role in regulating the surface expression and signaling of endogenous alpha 2-adrenergic receptors and muscarinic acetylcholine receptors in primary neurons, as well as in the transport of specific receptor subtypes to dendritic and postsynaptic locations. Additionally, Rab43's actions are cell-specific and directed by direct interaction, implying multiple delivery routes for different GPCRs in neurons.