Nascent Proteome Remodeling following Homeostatic Scaling at Hippocampal Synapses

Abstract

SummaryHomeostatic scaling adjusts the strength of synaptic connections up or down in response to large changes in input. To identify the landscape of proteomic changes that contribute to opposing forms of homeostatic plasticity, we examined the plasticity-induced changes in the newly synthesized proteome. Cultured rat hippocampal neurons underwent homeostatic up-scaling or down-scaling. We used BONCAT (bio-orthogonal non-canonical amino acid tagging) to metabolically label, capture, and identify newly synthesized proteins, detecting and analyzing 5,940 newly synthesized proteins using mass spectrometry and label-free quantitation. Neither up- nor down-scaling produced changes in the number of different proteins translated. Rather, up- and down-scaling elicited opposing translational regulation of several molecular pathways, producing targeted adjustments in the proteome. We discovered ∼300 differentially regulated proteins involved in neurite outgrowth, axon guidance, filopodia assembly, excitatory synapses, and glutamate receptor complexes. We also identified differentially regulated proteins that are associated with multiple diseases, including schizophrenia, epilepsy, and Parkinson’s disease.

Nanoscale Structural Plasticity of the Active Zone Matrix Modulates Presynaptic Function

“…In contrast to a previous study reporting inactivity-induced decreases in Bsn levels in cortical neurons (Lazarevic et al., 2011), we found no evidence of such a decrease in hippocampal neurons (Glebov et al., 2016); furthermore, Bsn synthesis rate is independent of activity manipulation (Schanzenbächer et al., 2016), suggesting that activity-dependent regulation of the hippocampal AZ structure may differ from that in the cortex. We therefore used STORM to visualize the distribution of Bsn, Ca v 2.1, and RIM following activity blockade.…”

“…Chronic blockade of network activity results in a decrease in the area of the Bsn clusters and a corresponding increase in Bsn NND, without any major changes in the overall AZ morphology or Bsn levels. These results agree with the previously published data in hippocampal neurons (Glebov et al., 2016, Schanzenbächer et al., 2016) but are at odds with another study in cortical neurons (Lazarevic et al., 2011). The reason for this discrepancy is not clear but may be due to the intrinsic differences between cell types.…”

Activity-Induced Regulation of Synaptic Strength through the Chromatin Reader L3mbtl1

“…More than 10 genes, including Arc, Homer1a, and polo-like kinase 2 (Plk2), display altered expression levels upon an increase in neuronal activity and are critical for the expression of homeostatic synaptic downscaling (Table S1). Importantly, the inhibitors of transcription and translation dysregulate homeostatic synaptic plasticity (Ibata et al, 2008; Schanzenbacher et al, 2016). These results clearly illustrate the critical role of activity-dependent transcriptional and translational machineries in homeostatic synaptic scaling.…”

Dynamic Control of Dendritic mRNA Expression by CNOT7 Regulates Synaptic Efficacy and Higher Cognitive Function

“…Some evidence suggests that a reduction of CNOT7 takes place with other types of stimulation in cultured neurons (Schanzenbacher et al, 2016) and even during learning and memory in living animals (Cho et al, 2015). Although it is clear from our data that CNOT7 is rapidly destroyed upon LTP induction, reduced CNOT7 synthesis may also occur at this time.…”