GluN2B influences the progression of status epilepticus by modulating calcium ion homeostasis through its interaction with CaMKIIα

TL;DR

This study shows that GluN2B and CaMKIIα interact to disrupt calcium balance in the brain during seizures, potentially offering new targets for treating status epilepticus.

Contribution

The novel contribution is identifying how GluN2B binding to CaMKIIα disrupts calcium homeostasis, influencing the progression of status epilepticus.

Findings

GluN2B binding to CaMKIIα reduces phosphorylation at T286, affecting calcium homeostasis.

Inhibiting GluN2B with ifenprodil counteracts calcium influx and modulates p-CaMKIIα expression.

The interaction between GluN2B and CaMKIIα disrupts the excitation-inhibition balance in the central nervous system.

Abstract

Status epilepticus (SE) is a neurological emergency characterized by prolonged, unresolved epileptic seizures, often resulting in adverse outcomes. Conventional pharmaceuticals are not universally effective in terminating epileptic seizures; therefore, identifying novel targets for seizure cessation and the prevention of SE is crucial. This study aimed to assess the expression levels and interactions of the N-methyl-D-aspartate receptor (NMDAR) subunit GluN2B and CaMKIIα following epileptic convulsions and to explore their potential mechanisms of action.

This study utilized Western blotting to evaluate the protein expression levels of CaMKIIα, p-CaMKIIα, and GluN2B in the hippocampus of mice subjected to kainic acid-induced SE. Immunofluorescence colocalization analysis and co-immunoprecipitation were utilized to investigate the interaction between GluN2B and CaMKIIα in the hippocampus. Additionally, flow cytometry was employed to measure intracellular calcium ion levels.

Compared to the sham operation group, the intracellular calcium ion concentration in the hippocampus of SE mice was elevated, whereas the expression of p-CaMKIIα was markedly reduced. The levels of CaMKIIα and GluN2B remained unchanged, and the immune complex of GluN2B and CaMKIIα in the SE group exhibited a significant increase. The GluN2B inhibitor ifenprodil was found to prolong the latency of epileptic seizures, counteract calcium influx, and modulate the expression of p-CaMKIIα, as well as the immune complex levels of GluN2B and CaMKIIα. These findings suggest that the interaction between GluN2B and CaMKIIα may be critical in the pathophysiological processes of SE, influencing the levels of p-CaMKIIα and calcium ion homeostasis.

The reduction in CaMKIIα phosphorylation levels depends on the NMDAR pathway. When GluN2B binds to CaMKIIα, it may occupy the autophosphorylation site of CaMKIIα (T286 binding site), thereby affecting its autophosphorylation. This results in decreased phosphorylation levels, disruption of NMDAR-dependent calcium homeostasis, and alteration of the excitation/inhibition balance.

After GluN2B binds with CaMKIIa, GluN2B occupies the CaMKIIa autophosphorylation site at threonine 286 (T286), affecting CaMKIIa autophosphorylation, reducing phosphorylation levels, and disrupting NMDAR-dependent calcium ion homeostasis, thereby disrupting the excitation-inhibition balance in the central nervous system and influencing the onset and progression of SE.

After GluN2B binds with CaMKIIa, GluN2B occupies the CaMKIIa autophosphorylation site at threonine 286 (T286), affecting CaMKIIa autophosphorylation, reducing phosphorylation levels, and disrupting NMDAR-dependent calcium ion homeostasis, thereby disrupting the excitation-inhibition balance in the central nervous system and influencing the onset and progression of SE.

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