N-Cadherin Transsynaptically Regulates Short-Term Plasticity at Glutamatergic Synapses in Embryonic Stem Cell-Derived Neurons

Abstract

The cell adhesion molecule N-cadherin has been proposed to regulate synapse formation in mammalian central neurons. This is based on its synaptic localization enabling alignment of presynaptic and postsynaptic specializations by an adhesion mechanism. However, a potential role of N-cadherin in regulating synaptic transmission has remained elusive. In this paper, a functional analysis of N-cadherin knock-out synapses was enabled by in vitro neuronal differentiation of mouse embryonic stem cells circumventing the early embryonic lethality of mice genetically null for N-cadherin. In our in vitro system, initial synapse formation was not altered in the absence of N-cadherin, which might be attributable to compensatory mechanisms. Here, we demonstrate that N-cadherin is required for regulating presynaptic function at glutamatergic synapses. An impairment in the availability of vesicles for exocytosis became apparent selectively during high activity. Short-term plasticity was strongly altered with synaptic depression enhanced in the absence of N-cadherin. Most intriguingly, facilitation was converted to depression under specific stimulation conditions. This indicates an important role of N-cadherin in the control of short-term plasticity.To analyze, whether N-cadherin regulates presynaptic function by a transsynaptic mechanism, we studied chimeric cultures consisting of wild-type neocortical neurons and ES cell-derived neurons. With N-cadherin absent only postsynaptically, we observed a similar increase in short-term synaptic depression as found in its complete absence. This indicates a retrograde control of short-term plasticity by N-cadherin. In summary, our results revealed an unexpected involvement of a synaptic adhesion molecule in the regulation of short-term plasticity at glutamatergic synapses.

Essential cooperation of N-cadherin and neuroligin-1 in the transsynaptic control of vesicle accumulation

“…We investigated presynaptic vesicle accumulation in cultured N-cadherin knockout neurons differentiated from homozygous N-cadherin knockout ES cells (21,23; N-cad −/− ). The growth of axons and dendrites was not altered in N-cad −/− neurons ( Fig.…”

“…We studied the effects of neuroligin-1 on release probability by analyzing the progressive block of evoked NMDA EPSCs by MK-801 (20 μM). We used cultured cortical neurons at 12-14 DIV, because NMDA EPSCs in ES cell-derived neurons exhibit only very small amplitudes (21). With N-cadherin function impaired by N-cadΔE coexpression, the enhancing effect of neuroligin-1 expression on release probability was blocked (Fig.…”

“…In addition to its important postsynaptic roles (4,(16)(17)(18), N-cadherin has been suggested to be involved in the formation of presynaptic vesicle clusters (4,16,19,20). However, these findings could not yet be confirmed in N-cadherin knockout neurons (21,22), and expression of N-cadherin in nonneuronal cells does not induce clustering of synaptic vesicles in contacting axons (3,9). This observation emphasizes that the molecular mechanisms involved in the control of vesicle accumulation by N-cadherin are rather incompletely understood.…”

β-Catenin regulates excitatory postsynaptic strength at hippocampal synapses

“…Upon losing ␤-catenin, the reduction of functional synaptic AMPARs could bias synapses to form thin and elongated rather than mushroom-shaped spines. A recent study that examined a role specifically for N-cadherin in synaptic transmission using knockout neurons did not find a change in mEPSC amplitude (22). It is therefore possible that other classical cadherins, whose activity is compromised by ␤-catenin deletion, may also play a role in regulating quantal size.…”

“…These observations suggest that the cadherin-catenin complex could potentially regulate aspects of synapse function beyond contributing to synapse assembly in developing neurons. Accordingly, impairing the adhesive activity of cadherins by deletion of ␤-catenin or N-cadherin reduces the number of reserve pool synaptic vesicles at the presynaptic terminal, resulting in enhanced synaptic depression during repetitive stimulation (21,22). Moreover, overexpressing an N-cadherin mutant lacking the extracellular domain or ␤-catenin mutants with an altered phosphorylation site alters spine morphology and synaptic efficacy (23-26).…”