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Activation-dependent plasticity of polarized GPCR distribution on the neuronal surface Free
Anne C. Simon1, Claude Loverdo2, Anne-Lise Gaffuri1, Michel Urbanski3, Delphine Ladarre1, Damien Carrel1, Isabelle Rivals4, Christophe Leterrier1,5, Olivier Benichou2, Pascal Dournaud6, Bela Szabo3, Raphael Voituriez2, and Zsolt Lenkei1,*
1Laboratoire de Neurobiologie, CNRS UMR7637, ESPCI-ParisTech, 10 Rue Vauquelin, Paris 75005, France
2Laboratoire de Physique Théorique de la Matière Condensée – CNRS-UMR7600 – Université Pierre et Marie Curie, 4 Place Jussieu, Paris 75005, France
3Institute of Experimental and Clinical Pharmacology and Toxicology – Albert-Ludwigs University, Albertstrasse 25, Freiburg 79104, Germany
4Equipe de Statistique Appliquée, ESPCI-ParisTech, 10 Rue Vauquelin, Paris 75005, France
5Present address: CRN2M, CNRS – Aix-Marseille Université UMR 7286, Marseille F-13916, France
6INSERM U676, Hôpital Robert-Debré, 48 Boulevard Sérurier, Paris 75019, France
*Correspondence to:Zsolt Lenkei, E-mail: zsolt.lenkei@espci.fr
J Mol Cell Biol, Volume 5, Issue 4, August 2013, 250-265,  https://doi.org/10.1093/jmcb/mjt014
Keyword: targeting, transcytosis, endocytosis, constitutive internalization, diffusion

Directionality of information flow through neuronal networks is sustained at cellular level by polarized neurons. However, specific targeting or anchoring motifs responsible for polarized distribution on the neuronal surface have only been identified for a few neuronal G-protein-coupled receptors (GPCRs). Here, through mutational and pharmacological modifications of the conformational state of two model GPCRs, the axonal CB1R cannabinoid and the somatodendritic SSTR2 somatostatin receptors, we show important conformation-dependent variations in polarized distribution. The underlying mechanisms include lower efficiency of conformation-dependent GPCR endocytosis in axons, compared with dendrites, particularly at moderate activation levels, as well as endocytosis-dependent transcytotic delivery of GPCRs from the somatodendritic domain to distal axonal portions, shown by using compartmentalized microfluidic devices. Kinetic modeling predicted that GPCR distribution polarity is highly regulated by steady-state endocytosis, which is conformation dependent and is able to regulate the relative amount of GPCRs targeted to axons and that axonally polarized distribution is an intermediary phenotype that appears at moderate basal activation levels. Indeed, we experimentally show that gradual changes in basal activation-dependent endocytosis lead to highly correlated shifts of polarized GPCR distribution on the neuronal surface, which can even result in a fully reversed polarized distribution of naturally somatodendritic or axonal GPCRs. In conclusion, polarized distribution of neuronal GPCRs may have a pharmacologically controllable component, which, in the absence of dominant targeting motifs, could even represent the principal regulator of sub-neuronal distribution. Consequently, chronic modifications of basal GPCR activation by therapeutic or abused drugs may lead to previously unanticipated changes in brain function through perturbation of polarized GPCR distribution on the neuronal surface.