Differential association of GABAB receptors with their effector ion channels in Purkinje cells

Luján, Rafael and Aguado, Carolina and Ciruela, Francisco and Cózar, Javier and Kleindienst, David and de la Ossa, Luis and Bettler, Bernhard and Wickman, Kevin and Watanabe, Masahiko and Shigemoto, Ryuichi and Fukazawa, Yugo (2018) Differential association of GABAB receptors with their effector ion channels in Purkinje cells. Brain Structure and Function, 223 (3). pp. 1565-1587. ISSN 1863-2661

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Official URL: http://dx.doi.org/10.1007/s00429-017-1568-y

Abstract

Metabotropic GABAB receptors mediate slow inhibitory effects presynaptically and postsynaptically through the modulation of different effector signalling pathways. Here, we analysed the distribution of GABAB receptors using highly sensitive SDS-digested freeze-fracture replica labelling in mouse cerebellar Purkinje cells. Immunoreactivity for GABAB1 was observed on presynaptic and, more abundantly, on postsynaptic compartments, showing both scattered and clustered distribution patterns. Quantitative analysis of immunoparticles revealed a somato-dendritic gradient, with the density of immunoparticles increasing 26-fold from somata to dendritic spines. To understand the spatial relationship of GABAB receptors with two key effector ion channels, the G protein-gated inwardly rectifying K+ (GIRK/Kir3) channel and the voltage-dependent Ca2+ channel, biochemical and immunohistochemical approaches were performed. Co-immunoprecipitation analysis demonstrated that GABAB receptors co-assembled with GIRK and CaV2.1 channels in the cerebellum. Using double-labelling immunoelectron microscopic techniques, co-clustering between GABAB1 and GIRK2 was detected in dendritic spines, whereas they were mainly segregated in the dendritic shafts. In contrast, co-clustering of GABAB1 and CaV2.1 was detected in dendritic shafts but not spines. Presynaptically, although no significant co-clustering of GABAB1 and GIRK2 or CaV2.1 channels was detected, inter-cluster distance for GABAB1 and GIRK2 was significantly smaller in the active zone than in the dendritic shafts, and that for GABAB1 and CaV2.1 was significantly smaller in the active zone than in the dendritic shafts and spines. Thus, GABAB receptors are associated with GIRK and CaV2.1 channels in different subcellular compartments. These data provide a better framework for understanding the different roles played by GABAB receptors and their effector ion channels in the cerebellar network.

Item Type: Article
DOI: 10.1007/s00429-017-1568-y
Uncontrolled Keywords: Potassium Channels, Calcium Channels, Quantification, Cerebellum, Synapses, Electron microscopy, GABAB receptors, Active zone, Parallel fibre, Freeze-fracture replica immunolabelling, Purkinje cells
Subjects: 500 Science > 570 Life sciences; biology > 571 Physiology
Research Group: Shigemoto Group
SWORD Depositor: Sword Import User
Depositing User: Sword Import User
Date Deposited: 19 Apr 2018 09:56
Last Modified: 19 Apr 2018 09:56
URI: https://repository.ist.ac.at/id/eprint/1013

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