Gq protein alpha subunits G alpha q and G alpha 11 are localized at postsynaptic extra-junctional membrane of cerebellar Purkinje cells and hippocampal pyramidal cells
J. Tanaka et al., Gq protein alpha subunits G alpha q and G alpha 11 are localized at postsynaptic extra-junctional membrane of cerebellar Purkinje cells and hippocampal pyramidal cells, EUR J NEURO, 12(3), 2000, pp. 781-792
Following cell surface receptor activation, the alpha subunit of the Gq sub
class of GTP-binding proteins activates the phosphoinositide signalling pat
hway. Here we examined the expression and localization of Gq protein alpha
subunits in the adult mouse brain by in situ hybridization and immunohistoc
hemistry. Of the four members of the Gq protein alpha subunits, G alpha q a
nd G alpha 11 were transcribed predominantly in the brain. The highest tran
scriptional level of G alpha q was observed in cerebellar Purkinje cells (P
Cs) and hippocampal pyramidal cells, while that of G alpha 11 was noted in
hippocampal pyramidal cells. Antibody against the C-terminal peptide common
to G alpha q and G alpha 11 strongly labelled the cerebellar molecular lay
er and hippocampal neuropil layers. In these regions, immunogold preferenti
ally labelled the cytoplasmic face of postsynaptic cell membrane of PCs and
pyramidal cells. Immunoparticles were distributed along the extra-junction
al cell membrane of spines, dendrites and somata, but were almost excluded
from the junctional membrane. By double immunofluorescence, G alpha q/G alp
ha 11 was extensively colocalized with metabotropic glutamate receptor mGlu
R1 alpha in dendritic spines of PCs and with mGluR5 in those of hippocampal
pyramidal cells. Together with concentrated localization of mGluR1 alpha a
nd mGluR5 in a peri-junctional annulus on PC and pyramidal cell synapses (B
aude et al. 1993, Neuron, 11, 771-787; Lujan et al. 1996, Eur. J. Neurosci.
, 8, 1488-1500), the present molecular-anatomical findings suggest that per
i-junctional stimulation of the group I metabotropic glutamate receptors is
mediated by G alpha q and/or G alpha 11, leading to the activation of the
intracellular effector, phospholipase C beta.