Inhibitory Synapse Dynamics: Coordinated Presynaptic and Postsynaptic Mobility and the Major Contribution of Recycled Vesicles to New Synapse Formation

摘要: Dynamics of GABAergic synaptic components have been studied previously over milliseconds to minutes, revealing mobility postsynaptic scaffolds and receptors. Here we image inhibitory synapses containing fluorescently tagged scaffold Gephyrin, together with presynaptic vesicular GABA transporter (VGAT) or GABAA receptor γ2 subunit (GABAARγ2), seconds days in cultured rat hippocampal neurons, modes synapse formation remodeling. Entire were mobile, translocating rapidly within a confined region exhibiting greater nonstochastic motion multihour periods. Presynaptic moved unison, maintaining close apposition while distances several micrometers. An observed flux the density puncta partially resulted from apparent merging splitting preexisting clusters. De novo was observed, marked by appearance stably apposed Gephyrin VGAT clusters at sites lacking either component. Coclustering GABAARγ2 supports identification such new as synapses. Nascent occurred gradual accumulation hours, clustering preceding that GABAARγ2. Comparing labeling active uptake luminal domain antibody post hoc immunocytochemistry indicated recycling vesicles boutons significantly contribute vesicle pools majority Although formed primarily on dendrite shafts, some also dendritic protrusions, without interconversion. Altogether, long-term imaging reveals complex dynamics perpetual remodeling implications for mechanisms assembly integration.