Subcellular compartment-specific molecular diversity of pre- and post-synaptic GABA-activated GIRK channels in Purkinje cells.
Activation of G protein-gated inwardly-rectifying K(+) (GIRK or Kir3) channels by metabotropic gamma-aminobutyric acid (B) (GABA(B)) receptors is an essential signalling pathway controlling neuronal excitability and synaptic transmission in the brain. To investigate the relationship between GIRK channel subunits and GABA(B) 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 GABA(B) 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 GABA(B) 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 GABA(B) 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 GABA(B) 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.
Fernández-Alacid
Laura
L
Departamento de Ciencias Médicas, CRIB-Facultad de Medicina, Universidad Castilla-La Mancha, Albacete, Spain.
Aguado
Carolina
C
Ciruela
Francisco
F
Martín
Ricardo
R
Colón
José
J
Cabañero
María José
MJ
Gassmann
Martin
M
Watanabe
Masahiko
M
Shigemoto
Ryuichi
R
Wickman
Kevin
K
Bettler
Bernhard
B
Sánchez-Prieto
José
J
Luján
Rafael
R
D000818:Animals; D002451:Cell Compartmentation / Q000187:drug effects / Q000502:physiology; D002525:Cerebellar Cortex / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D003712:Dendrites / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D005260:Female; D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism*; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D016253:Microscopy, Immunoelectron; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology; D021122:Protein Subunits / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D011689:Purkinje Cells / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D018080:Receptors, GABA-B / Q000235:genetics*; D013570:Synaptic Membranes / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D013574:Synaptosomes / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D051676:G Protein-Coupled Inwardly-Rectifying Potassium Channels; D021122:Protein Subunits; D018080:Receptors, GABA-B; D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid