Neuroligin-2 accelerates GABAergic synapse maturation in cerebellar granule cells (original) (raw)
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Developmental Changes of GABA Synaptic Transient in Cerebellar Granule Cells
Molecular Pharmacology, 2005
The time course of synaptic currents is largely determined by the microscopic gating of the postsynaptic receptors and the temporal profile of the synaptic neurotransmitter concentration. Although several lines of evidence indicate that developmental changes of GABAergic synaptic current time course are clearly correlated with a switch in postsynaptic receptors, much less is known about the modification of GABA release during development. To address this issue, we studied the sensitivity of miniature inhibitory postsynaptic currents (mIPSCs) to a quickly dissociating competitive antagonist, 1,2,5,6-tetrahydropyridine-4-yl)methylphosphinic acid (TPMPA), in neurons cultured for 6 to 8 days in vitro (DIV) ("young") and for 12 to 14 DIV ("old"). mIPSCs recorded in young neurons were significantly more resistant to the block by TPMPA. This observation was interpreted as a consequence of a more efficient displacement
The Journal of Neuroscience, 2001
Developmental changes in miniature IPSC (mIPSC) kinetics have been demonstrated previously in cerebellar neurons in rodents. We report that these kinetic changes in mice are determined primarily by developmental changes in GABA A receptor subunit expression. mIPSCs were studied by whole-cell recordings in cerebellar slices, prepared from postnatal day 11 (P11) and P35 mice. Similar to reports in granule neurons, wild-type cerebellar stellate neuron mIPSCs at P11 had slow decay kinetics, whereas P35 mIPSCs decayed five times faster. When mIPSCs in cerebellar stellate neurons were compared between wild-type (ϩ/ϩ) and GABA A receptor ␣1 subunitdeficient (Ϫ/Ϫ) littermates at P35, we observed dramatically slower mIPSC decay rates in Ϫ/Ϫ animals. We took advantage of the greater potency of imidazopyridines for GABA current potentiation with ␣1 subunit-containing receptors to characterize the relative contribution of ␣1 subunits in native receptors on inhibitory synapses of cerebellar granule neurons. Zolpideminduced prolongation of mIPSC decay was variable among distinct cells, but it increased during development in wild-type mice. Similarly, Zolpidem prolongation of mIPSC decay rate was significantly greater in adult ϩ/ϩ mice than in knockouts. We propose that an increased ␣1 subunit assembly in postsynaptic receptors of cerebellar inhibitory synapses is responsible for the fast inhibitory synaptic currents that are normally observed during postnatal development.
The Journal of Neuroscience : The Official Journal of the Society for Neuroscience
Developmental changes in miniature IPSC (mIPSC) kinetics have been demonstrated previously in cerebellar neurons in rodents. We report that these kinetic changes in mice are determined primarily by developmental changes in GABA A receptor subunit expression. mIPSCs were studied by whole-cell recordings in cerebellar slices, prepared from postnatal day 11 (P11) and P35 mice. Similar to reports in granule neurons, wild-type cerebellar stellate neuron mIPSCs at P11 had slow decay kinetics, whereas P35 mIPSCs decayed five times faster. When mIPSCs in cerebellar stellate neurons were compared between wild-type (ϩ/ϩ) and GABA A receptor ␣1 subunitdeficient (Ϫ/Ϫ) littermates at P35, we observed dramatically slower mIPSC decay rates in Ϫ/Ϫ animals. We took advantage of the greater potency of imidazopyridines for GABA current potentiation with ␣1 subunit-containing receptors to characterize the relative contribution of ␣1 subunits in native receptors on inhibitory synapses of cerebellar granule neurons. Zolpideminduced prolongation of mIPSC decay was variable among distinct cells, but it increased during development in wild-type mice. Similarly, Zolpidem prolongation of mIPSC decay rate was significantly greater in adult ϩ/ϩ mice than in knockouts. We propose that an increased ␣1 subunit assembly in postsynaptic receptors of cerebellar inhibitory synapses is responsible for the fast inhibitory synaptic currents that are normally observed during postnatal development.
Journal of Neurophysiology, 2005
There is a large variation in structurally and functionally different GABAA receptor subtypes. The expression pattern of GABAA receptor subunits is highly regulated, both temporarily and spatially. Especially during development, profound changes in subunit expression have been described. In most brain areas, the GABAA receptor α1 subunit replaces the α2 and/or α3 subunit as major α subunit. This is accompanied by a marked decrease in the open time of GABAA receptors and hence in the duration of postsynaptic responses. We describe here the development of GABAergic, synaptic transmission in mice lacking the α1 subunit. We show that α1 is to a large extent—but not entirely—responsible for the relatively short duration of postsynaptic responses in the developing and the mature brain. However, α1 already affects GABAergic transmission in the neonatal cerebral cortex when it is only sparsely expressed. It appears that the α1 −/− mice do not show a large reduction in GABAergic synapses but...
Carolina Digital Repository (University of North Carolina at Chapel Hill), 2001
Developmental changes in miniature IPSC (mIPSC) kinetics have been demonstrated previously in cerebellar neurons in rodents. We report that these kinetic changes in mice are determined primarily by developmental changes in GABA A receptor subunit expression. mIPSCs were studied by whole-cell recordings in cerebellar slices, prepared from postnatal day 11 (P11) and P35 mice. Similar to reports in granule neurons, wild-type cerebellar stellate neuron mIPSCs at P11 had slow decay kinetics, whereas P35 mIPSCs decayed five times faster. When mIPSCs in cerebellar stellate neurons were compared between wild-type (ϩ/ϩ) and GABA A receptor ␣1 subunitdeficient (Ϫ/Ϫ) littermates at P35, we observed dramatically slower mIPSC decay rates in Ϫ/Ϫ animals. We took advantage of the greater potency of imidazopyridines for GABA current potentiation with ␣1 subunit-containing receptors to characterize the relative contribution of ␣1 subunits in native receptors on inhibitory synapses of cerebellar granule neurons. Zolpideminduced prolongation of mIPSC decay was variable among distinct cells, but it increased during development in wild-type mice. Similarly, Zolpidem prolongation of mIPSC decay rate was significantly greater in adult ϩ/ϩ mice than in knockouts. We propose that an increased ␣1 subunit assembly in postsynaptic receptors of cerebellar inhibitory synapses is responsible for the fast inhibitory synaptic currents that are normally observed during postnatal development.
GABA A receptors can initiate the formation of functional inhibitory GABAergic synapses
European Journal of Neuroscience, 2013
The mechanisms that underlie the selection of an inhibitory GABAergic axon's postsynaptic targets and the formation of the first contacts are currently unknown. To determine whether expression of GABA A receptors (GABA A Rs) themselvesthe essential functional postsynaptic components of GABAergic synapsescan be sufficient to initiate formation of synaptic contacts, a novel co-culture system was devised. In this system, the presynaptic GABAergic axons originated from embryonic rat basal ganglia medium spiny neurones, whereas their most prevalent postsynaptic targets, i.e. a1/b2/c2-GABA A Rs, were expressed constitutively in a stably transfected human embryonic kidney 293 (HEK293) cell line. The first synapse-like contacts in these co-cultures were detected by colocalization of presynaptic and postsynaptic markers within 2 h. The number of contacts reached a plateau at 24 h. These contacts were stable, as assessed by live cell imaging; they were active, as determined by uptake of a fluorescently labelled synaptotagmin vesicle-luminal domain-specific antibody; and they supported spontaneous and action potential-driven postsynaptic GABAergic currents. Ultrastructural analysis confirmed the presence of characteristics typical of active synapses. Synapse formation was not observed with control or N-methyl-D-aspartate receptor-expressing HEK293 cells. A prominent increase in synapse formation and strength was observed when neuroligin-2 was co-expressed with GABA A Rs, suggesting a cooperative relationship between these proteins. Thus, in addition to fulfilling an essential functional role, postsynaptic GABA A Rs can promote the adhesion of inhibitory axons and the development of functional synapses.
Synapse formation and clustering of neuroligin-2 in the absence of GABAA receptors
Proceedings of the National Academy of Sciences, 2008
GABAergic synapses are crucial for brain function, but the mechanisms underlying inhibitory synaptogenesis are unclear. Here, we show that postnatal Purkinje cells (PCs) of GABAA␣1 knockout (KO) mice express transiently the ␣3 subunit, leading to the assembly of functional GABAA receptors and initial normal formation of inhibitory synapses, that are retained until adulthood. Subsequently, down-regulation of the ␣3 subunit causes a complete loss of GABAergic postsynaptic currents, resulting in a decreased rate of inhibitory synaptogenesis and formation of mismatched synapses between GABAergic axons and PC spines. Notably, the postsynaptic adhesion molecule neuroligin-2 (NL2) is correctly targeted to inhibitory synapses lacking GABAA receptors and the scaffold molecule gephyrin, but is absent from mismatched synapses, despite innervation by GABAergic axons. Our data indicate that GABAA receptors are dispensable for synapse formation and maintenance and for targeting NL2 to inhibitory synapses. However, GABAergic signaling appears to be crucial for activity-dependent regulation of synapse density during neuronal maturation.
Expression of Distinct Subunits of GABAA Receptor Regulates Inhibitory Synaptic Strength
Journal of Neurophysiology, 2004
Expression of distinct ␣ subunits of GABA A receptor regulates inhibitory synaptic strength. . Distinct ␣ subunit subtypes in the molecular assembly of GABA A receptors are a critical determinant of the functional properties of inhibitory synapses and their modulation by a range of pharmacological agents. We investigated the contribution of these subunits to the developmental changes of inhibitory synapses in cerebellar granule neurons in primary cultures from wild-type and ␣1 subunit Ϫ/Ϫ mice. The decay time of miniature inhibitory postsynaptic currents (mIPSCs) halved between 6 days in vitro (DIV6) and DIV12. This was paralleled by the decrease of ␣2 and ␣3 subunits, the increase of ␣1 and ␣6 subunits expression at synapses, and changes in the action of selective ␣ subunit modulators. A small but significant shortening of mIPSCs was observed with development in cells from Ϫ/Ϫ mice together with a decrease in the expression of ␣3 subunit. In contrast, the expression of ␣2 subunit at inhibitory synapses in Ϫ/Ϫ cells was significantly higher than in ϩ/ϩ cells at DIV11-12. ␣5 subunit was not detected, and increased sensitivity to a selective ␣4/␣6 subunit agonist suggests increased expression of extrasynaptic receptors in Ϫ/Ϫ mice. 2/3 subunit expression and loreclezole sensitivity increased with development in ϩ/ϩ but not in Ϫ/Ϫ cells, supporting the preferential association of the ␣1 with the 2 subunit. Synaptic charge transfer strongly decreased with development but was not different between cells in the ϩ/ϩ and Ϫ/Ϫ groups until DIV11-12. Our results uncover a pattern of sequential expression of ␣ subunits underlying the changes in functional efficacy of GABAergic networks with development. RA. Effects of ␥2S subunit incorporation on GABA A receptor macroscopic kinetics. Neuropharmacology 44: 1003-1012, 2003. Bollan K, King D, Robertson LA, Brown K, Taylor PM, Moss SJ, and Connolly CN. GABA A receptor composition is determined by distinct assembly signals within ␣ and  Subunits. J Biol Chem 278: 4747-4755, 2003. Brickley SG, Cull-Candy SG, and Farrant M. Development of a tonic form of synaptic inhibition in rat cerebellar granule cells resulting from persistent activation of GABA A receptors. J Physiol 497: 753-759, 1996. Brickley SG, Revilla V, Cull-Candy SG, Wisden W, and Farrant M. Adaptive regulation of neuronal excitability by a voltage-independent potassium conductance. Nature 409: 88 -92, 2001. Brown N, Kerby J, Bonnert TP, Whiting PJ, and Wafford KA. Pharmacological characterization of a novel cell line expressing human ␣43␦ GABA A receptors. Br J Pharmacol 136: 965-974, 2002. Brunig I, Scotti E, Sidler C, and Fritschy JM. Intact sorting, targeting, and clustering of GABA A receptor subtypes in hippocampal neurons in vitro. Wenthold RJ, Bredt DS, and Nicoll RA. Stargazing regulates synaptic targeting of AMPA receptors by two distinct mechanisms. Nature 408: 936 -943, 2000. Christie SB, Miralles CP, and De Blas AL GAB Aergic innervation organizes synaptic and extrasynaptic GABA A receptor clustering in cultured hippocampal neurons. J Neurosci 22: 684 -697, 2002. Ebert B, Thompson SA, Saounatsou K, McKernan R, Krogsgaard-Larsen P, and Wafford KA. Differences in agonist/antagonist binding affinity and receptor transduction using recombinant human GABA A receptors. Mol Pharmacol 52: 1150 -1156, 1997. Farrant M and Brickley SG. Properties of GABA A receptor-mediated transmission at newly formed Golgi-granule cell synapses in the cerebellum. Neuropharmacology 44: 181-189, 2003. Farrant M, Wisden W, Cull-Candy S, and Brickley SG. Absence of tonic GABA A mediated conductance in cerebellar granule cells of ␣6 Ϫ/Ϫ mice. Soc Neurosci Abstr 25: 246, 1999. Fisher JL, Hinkle DJ, and Macdonald RL. Loreclezole inhibition of recombinant ␣11␥2L GABA A receptor single channel currents. Neuropharmacology 39: 235-245, 2000. Fritschy JM, Paysan J, and Mohler H. Switch in the expression of rat GABA A receptor subtypes during postnatal development: an immunohistochemical study. J Neurosci 9: 5302-5324, 1994. Gallo V, Kingsbury A, Balazs R, and Jorgensen OS. The role of depolarization in the survival and differentiation of cerebellar granule cells in culture. J Neurosci 7: 2203-2213, 1987. Gao B and Fritschy JM. Cerebellar granule cells in vitro recapitulate the in vivo pattern of GABA A -receptor subunit expression. Brain Res Dev Brain Res 88: 1-16, 1995. Gingrich KJ, Roberts WA, and Kass RS. Dependence of the GABA A receptor gating kinetics on the ␣-subunit isoform: implications for structurefunction relations and synaptic transmission. J Physiol 489: 529 -543, 1995. Hamann M, Rossi DJ, and Attwell D. Tonic and spillover inhibition of granule cells control information flow through cerebellar cortex. Neuron 33: 625-633, 2002. Kaneda M, Farrant M, and Cull-Candy SG. Whole-cell and single-channel currents activated by GABA and glycine in granule cells of the rat cerebellum.
Plasticity of rat central inhibitory synapses through GABA metabolism
The Journal of Physiology, 2001
The brain adapts to experience by changing synaptic efficacy. Extensively studied mechanisms of plasticity include changes in the probability of transmitter release and in postsynaptic responsiveness. However, evidence from aminergic synapses indicates that the biochemistry of neurotransmitters provides an additional tool to alter synaptic strength. For example, dopaminergic transmission can be boosted by the precursor L-DOPA, which enhances the transmitter content of individual vesicles and counteracts Parkinson's disease.