TY - JOUR
T1 - Distinct mechanisms regulate GABA(A) receptor and gephyrin clustering at perisomatic and axo-axonic synapses on CA1 pyramidal cells
AU - Panzanelli, Patrizia
AU - Gunn, Benjamin G.
AU - Schlatter, Monika C.
AU - Benke, Dietmar
AU - Tyagarajan, Shiva K.
AU - Scheiffele, Peter
AU - Belelli, Delia
AU - Lambert, Jeremy J.
AU - Rudolph, Uwe
AU - Fritschy, Jean-Marc
PY - 2011/10/15
Y1 - 2011/10/15
N2 - Pyramidal cells express various GABA(A) receptor (GABA(A)R) subtypes, possibly to match inputs from functionally distinct interneurons targeting specific subcellular domains. Postsynaptic anchoring of GABA(A)Rs is ensured by a complex interplay between the scaffolding protein gephyrin, neuroligin-2 and collybistin. Direct interactions between these proteins and GABA(A)R subunits might contribute to synapse-specific distribution of GABA(A)R subtypes. In addition, the dystrophin-glycoprotein complex, mainly localized at perisomatic synapses, regulates GABA(A)R postsynaptic clustering at these sites. Here, we investigated how the functional and molecular organization of GABAergic synapses in CA1 pyramidal neurons is altered in mice lacking the GABA(A)R alpha 2 subunit (alpha 2-KO). We report a marked, layer-specific loss of postsynaptic gephyrin and neuroligin-2 clusters, without changes in GABAergic presynaptic terminals. Whole-cell voltage-clamp recordings in slices from alpha 2-KO mice show a 40% decrease in GABAergic mIPSC frequency, with unchanged amplitude and kinetics. Applying low/high concentrations of zolpidem to discriminate between alpha 1- and alpha 2/alpha 3-GABA(A)Rs demonstrates that residual mIPSCs in alpha 2-KO mice are mediated by alpha 1-GABA(A)Rs. Immunofluorescence analysis reveals maintenance of alpha 1-GABA(A)R and neuroligin-2 clusters, but not gephyrin clusters, in perisomatic synapses of mutant mice, along with a complete loss of these three markers on the axon initial segment. This striking subcellular difference correlates with the preservation of dystrophin clusters, colocalized with neuroligin-2 and alpha 1-GABA(A)Rs on pyramidal cell bodies of mutant mice. Dystrophin was not detected on the axon initial segment in either genotype. Collectively, these findings reveal synapse-specific anchoring of GABA(A)Rs at postsynaptic sites and suggest that the dystrophin-glycoprotein complex contributes to stabilize alpha 1-GABA(A)R and neuroligin-2, but not gephyrin, in perisomatic postsynaptic densities.
AB - Pyramidal cells express various GABA(A) receptor (GABA(A)R) subtypes, possibly to match inputs from functionally distinct interneurons targeting specific subcellular domains. Postsynaptic anchoring of GABA(A)Rs is ensured by a complex interplay between the scaffolding protein gephyrin, neuroligin-2 and collybistin. Direct interactions between these proteins and GABA(A)R subunits might contribute to synapse-specific distribution of GABA(A)R subtypes. In addition, the dystrophin-glycoprotein complex, mainly localized at perisomatic synapses, regulates GABA(A)R postsynaptic clustering at these sites. Here, we investigated how the functional and molecular organization of GABAergic synapses in CA1 pyramidal neurons is altered in mice lacking the GABA(A)R alpha 2 subunit (alpha 2-KO). We report a marked, layer-specific loss of postsynaptic gephyrin and neuroligin-2 clusters, without changes in GABAergic presynaptic terminals. Whole-cell voltage-clamp recordings in slices from alpha 2-KO mice show a 40% decrease in GABAergic mIPSC frequency, with unchanged amplitude and kinetics. Applying low/high concentrations of zolpidem to discriminate between alpha 1- and alpha 2/alpha 3-GABA(A)Rs demonstrates that residual mIPSCs in alpha 2-KO mice are mediated by alpha 1-GABA(A)Rs. Immunofluorescence analysis reveals maintenance of alpha 1-GABA(A)R and neuroligin-2 clusters, but not gephyrin clusters, in perisomatic synapses of mutant mice, along with a complete loss of these three markers on the axon initial segment. This striking subcellular difference correlates with the preservation of dystrophin clusters, colocalized with neuroligin-2 and alpha 1-GABA(A)Rs on pyramidal cell bodies of mutant mice. Dystrophin was not detected on the axon initial segment in either genotype. Collectively, these findings reveal synapse-specific anchoring of GABA(A)Rs at postsynaptic sites and suggest that the dystrophin-glycoprotein complex contributes to stabilize alpha 1-GABA(A)R and neuroligin-2, but not gephyrin, in perisomatic postsynaptic densities.
KW - INITIAL SEGMENT
KW - INHIBITORY SYNAPSES
KW - GABAERGIC SYNAPSES
KW - A-RECEPTORS
KW - GABA(A)-RECEPTOR SUBTYPES
KW - GLYCOPROTEIN COMPLEX
KW - HIPPOCAMPAL-NEURONS
KW - MOUSE HIPPOCAMPAL
KW - PURKINJE-CELLS
KW - RAT-BRAIN
U2 - 10.1113/jphysiol.2011.216028
DO - 10.1113/jphysiol.2011.216028
M3 - Article
C2 - 21825022
SN - 0022-3751
VL - 589
SP - 4959
EP - 4980
JO - Journal of Physiology
JF - Journal of Physiology
IS - 20
ER -