E3 ubiquitin ligase Nedd4‐2 exerts neuroprotective effects during endoplasmic reticulum stress

Abstract

The neural precursor cell expressed developmentally down‐regulated protein 4‐like (Nedd4‐2) is an E3 ubiquitin ligase critical for neurodevelopment and homeostasis of neural circuit excitability. While dysregulation of Nedd4‐2 has been linked to elevated seizure susceptibility through impaired ubiquitination of multiple direct substrates, it remains largely unclear whether Nedd4‐2 interconnects other cellular pathways that affect neuronal activity and seizure susceptibility. Here, we first showed that Nedd4‐2 associates with the endoplasmic reticulum (ER) and regulates the expression of multiple ER‐resident proteins. Furthermore, utilizing Nedd4‐2 conditional knockout mice, we showed that Nedd4‐2 is required for the maintenance of spontaneous neural activity and excitatory synapses following the induction of ER stress. When analyzing activation of the canonical pathways of ER stress response, we found that Nedd4‐2 is required for phosphorylation of eIF2α. While phosphorylation of eIF2α has been shown to reduce seizure susceptibility, attempts to facilitate phosphorylation of eIF2α in Nedd4‐2 conditional knockout mice failed to produce such a beneficial function, suggesting a role for Nedd4‐2 in integrating the ER stress response to modulate seizure susceptibility. Altogether, our study demonstrates neuroprotective functions of Nedd4‐2 during ER stress in neurons and could provide insight into neurological diseases in which the expression or activity of Nedd4‐2 is impaired.

Nedd4-2 Haploinsufficiency in Mice Impairs the Ubiquitination of Rer1 and Increases the Susceptibility to Endoplasmic Reticulum Stress and Seizures

“…NEDD4-2 seemed to take part in both UPR machineries: degradation of unfolded proteins through autophagy ( Wang et al, 2016 ) and translational suppression through association with ribosomal proteins ( Eagleman et al, 2021 ). NEDD4-2 was recently reported to integrate the ER stress response to modulate seizure susceptibility ( Lodes et al, 2022 ). We also found the changes in ER protein processing pathway in the proteomic analysis of Nedd4-2 +/− mice with increased seizure susceptibility ( Liu et al, 2021 ).…”

“…ER stress caused could upregulate hepatic Nedd4-2 to induce an autophagic response to clear unfolded proteins ( Wang et al, 2016 ). Recently, neuronal Nedd4-2 was found to elicit ER stress-associated translational suppression through interaction with ribosomal proteins and to modulate seizure susceptibility by integrating the ER stress responses ( Eagleman et al, 2021 ; Lodes et al, 2022 ). These studies indicated a protective role of Nedd4-2 in relieving ER stress and seizures besides direct ubiquitination of neuroactive substrates.…”

Hyperfunction of post-synaptic density protein 95 promotes seizure response in early-stage aβ pathology

“…Lentiviral transduction was performed on DIV 9 (Origene; PSD-95 lentiviral particle #RC215178L4V; control lentiviral particle #PS100093V). For the synapse counting experiment, coverslips were prepared as described previously (Lodes et al, 2022 ). Briefly, cells were washed with phosphate-buffered saline (PBS) once, fixed with fixation buffer (4% paraformaldehyde and 4% sucrose in PBS) for 15 min, and then permeabilized with permeabilization buffer (0.2% Triton X-100 in PBS) for 10 min.…”

Amyloid beta induces Fmr1‐dependent translational suppression and hyposynchrony of neural activity via phosphorylation of eIF2α and eEF2

“…G* power was used to perform power analysis. Expected effect sizes were based on our previously published studies (Eagleman et al, 2021; Lodes et al, 2021). Sample sizes for western blot, MEA recording, and immunocytochemistry were equal or greater than the suggested size of 4, 6, and 11, respectively, for a power of 0.8 and a Type I error (alpha) of 0.05.…”