Subcellular compartment-specific molecular diversity of pre- and post-synaptic GABAB-activated GIRK channels in Purkinje cells Journal Article


Author(s): Fernández-Alacid, Laura; Aguado, Carolina; Ciruela, Francisco; Martín, Ricardo J; Colón, José; Cabañero, María José; Gassmann, Martin; Watanabe, Masahiko; Shigemoto, Ryuichi; Wickman, Kevin D; Bettler, Bernhard; Sánchez-Prieto, José; Luján, Rafael
Article Title: Subcellular compartment-specific molecular diversity of pre- and post-synaptic GABAB-activated GIRK channels in Purkinje cells
Affiliation
Abstract: Activation of G protein-gated inwardly-rectifying K+ (GIRK or Kir3) channels by metabotropic gamma-aminobutyric acid (B) (GABAB) receptors is an essential signalling pathway controlling neuronal excitability and synaptic transmission in the brain. To investigate the relationship between GIRK channel subunits and GABAB receptors in cerebellar Purkinje cells at post- and pre-synaptic sites, we used biochemical, functional and immunohistochemical techniques. Co-immunoprecipitation analysis demonstrated that GIRK subunits are co-assembled with GABAB receptors in the cerebellum. Immunoelectron microscopy showed that the subunit composition of GIRK channels in Purkinje cell spines is compartment-dependent. Thus, at extrasynaptic sites GIRK channels are formed by GIRK1/GIRK2/GIRK3, post-synaptic densities contain GIRK2/GIRK3 and dendritic shafts contain GIRK1/GIRK3. The post-synaptic association of GIRK subunits with GABAB receptors in Purkinje cells is supported by the subcellular regulation of the ion channel and the receptor in mutant mice. At pre-synaptic sites, GIRK channels localized to parallel fibre terminals are formed by GIRK1/GIRK2/GIRK3 and co-localize with GABAB receptors. Consistent with this morphological evidence we demonstrate their functional interaction at axon terminals in the cerebellum by showing that GIRK channels play a role in the inhibition of glutamate release by GABAB receptors. The association of GIRK channels and GABA B receptors with excitatory synapses at both post- and pre-synaptic sites indicates their intimate involvement in the modulation of glutamatergic neurotransmission in the cerebellum.
Keywords: Immunohistochemistry; Potassium Channels; Cerebellum; Electron microscopy; Glutamate release; Subunit composition
Journal Title: Journal of Neurochemistry
Volume: 110
Issue 4
ISSN: 1471-4159
Publisher: Wiley  
Date Published: 2009-08-01
Start Page: 1363
End Page: 1376
DOI: 10.1111/j.1471-4159.2009.06229.x
Open access: no