PSD95 Suppresses Dendritic Arbor Development in Mature Hippocampal Neurons by Occluding the Clustering of NR2B-NMDA Receptors

Abstract

Considerable evidence indicates that the NMDA receptor (NMDAR) subunits NR2A and NR2B are critical mediators of synaptic plasticity and dendritogenesis; however, how they differentially regulate these processes is unclear. Here we investigate the roles of the NR2A and NR2B subunits, and of their scaffolding proteins PSD-95 and SAP102, in remodeling the dendritic architecture of developing hippocampal neurons (2–25 DIV). Analysis of the dendritic architecture and the temporal and spatial expression patterns of the NMDARs and anchoring proteins in immature cultures revealed a strong positive correlation between synaptic expression of the NR2B subunit and dendritogenesis. With maturation, the pruning of dendritic branches was paralleled by a strong reduction in overall and synaptic expression of NR2B, and a significant elevation in synaptic expression of NR2A and PSD95. Using constructs that alter the synaptic composition, we found that either over-expression of NR2B or knock-down of PSD95 by shRNA-PSD95 augmented dendritogenesis in immature neurons. Reactivation of dendritogenesis could also be achieved in mature cultured neurons, but required both manipulations simultaneously, and was accompanied by increased dendritic clustering of NR2B. Our results indicate that the developmental increase in synaptic expression of PSD95 obstructs the synaptic clustering of NR2B-NMDARs, and thereby restricts reactivation of dendritic branching. Experiments with shRNA-PSD95 and chimeric NR2A/NR2B constructs further revealed that C-terminus of the NR2B subunit (tail) was sufficient to induce robust dendritic branching in mature hippocampal neurons, and suggest that the NR2B tail is important in recruiting calcium-dependent signaling proteins and scaffolding proteins necessary for dendritogenesis.

Neonatal Irradiation Leads to Persistent Proteome Alterations Involved in Synaptic Plasticity in the Mouse Hippocampus and Cortex

“…59 The increase of PDS-95 expression is likely to restrict the synaptic clustering of glutamatergic receptors, and thereby reduce the level of dendritic branching. 60 This corroborates with our suggestion for an altered balance of actin polymerisation / depolymerisation process that may persistently affect axonal outgrowth and dendritic spine formation. 61 In general, the molecular alterations in the Rac1-Cofilin pathway and the level of PSD-95 correlate well with our previous data showing persistent downregulation of Rac1 but increased expression of miR-132, miR-134 and total cofilin in irradiated NMRI mice.…”

Ligand-induced Homotypic and Heterotypic Clustering of Apolipoprotein E Receptor 2

“…Receptor clustering is dependent on many aspects, such as ligand affinity, ligand dissociation, the size of ligands, and the concentration of coactivators (63)(64)(65)(66). In the case of the B cell receptor and T cell receptor clusters, the mobility of the ligand also affects the clustering of these receptors (67,68).…”

A Subset of Autism-Associated Genes Regulate the Structural Stability of Neurons

“…The composition of GluN2 subunits are developmentally regulated and critically determine the synaptic properties (Laurie and Seeburg, 1994; Sheng et al, 1994; Li et al, 1998). The GluN2B subunit expresses early during development gradually being replaced by GluN2A indicating its role in the formation of neuronal circuitry (Sheng et al, 1994; Li et al, 1998; Bustos et al, 2014). Overexpression or knockdown of GluN2B alters dendrite arborization in neurons both in vivo and in vitro (Ewald et al, 2008; Espinosa et al, 2009; Sepulveda et al, 2010; Bustos et al, 2014).…”

“…The GluN2B subunit expresses early during development gradually being replaced by GluN2A indicating its role in the formation of neuronal circuitry (Sheng et al, 1994; Li et al, 1998; Bustos et al, 2014). Overexpression or knockdown of GluN2B alters dendrite arborization in neurons both in vivo and in vitro (Ewald et al, 2008; Espinosa et al, 2009; Sepulveda et al, 2010; Bustos et al, 2014). GluN2B is also required for the formation of dendritic spines, maturation of synapses, and the proper molecular compositions of several postsynaptic proteins (Akashi et al, 2009; Espinosa et al, 2009; Brigman et al, 2010; Kelsch et al, 2012).…”