Sevoflurane alters α5β3GABAA receptor trafficking via calcium/calmodulin-dependent protein kinase II-dependent β3 subunit phosphorylation to produce cognitive impairment in aged mice

BACKGROUND: Sevoflurane increases surface expression of α5 subunit-containing γ-aminobutyric acid type A receptors (GABAAR-α5) and tonic currents in the hippocampus, contributing to postoperative memory decline. We investigated sevoflurane modulation of the phosphorylation of the β3 subunit which co-assembles with α5 subunits following Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) activation to alter receptor trafficking and exacerbate cognitive dysfunction. METHODS: Aged C57BL/6J mice and primary hippocampal neurones were exposed to 4 vol% sevoflurane for 2 h (Sev group). Cultured neurones were transfected with a phospho-null β3 subunit (S408/409A) generated by site-directed mutagenesis. Immunoblot analysis, immunofluorescence, Ca²⁺ imaging, whole-cell patch-clamp electrophysiological recording, pharmacological interventions, and behavioural tests were used. RESULTS: Sevoflurane triggered CaMKII-mediated phosphorylation at β3-S408/409, suppressing receptor internalisation and increasing surface accumulation of α5β3GABAARs (Sev vs control; P<0.0001). The β3-S408/409A double mutation abolished the enhanced surface expression of α5β3GABAARs (Sev+β3-S408/409A vs Sev+NC; P=0.0022). CaMKII inhibition with small molecule inhibitor KN-93 normalised surface upregulation of α5β3GABAARs (Sev+KN-93 vs Sev+vehicle; P<0.0001), attenuated enhanced tonic current (Sev+KN-93 vs Sev+vehicle; P=0.0027), and rescued contextual memory deficits (Sev+KN-93: 33.5% [7.3%] freezing vs Sev+vehicle: 19.3% [4.4%]; P=0.0139) induced by sevoflurane. CONCLUSIONS: Sevoflurane disrupts α5β3GABAARs trafficking through CaMKII/β3 S408/409 phosphorylation, identifying a potential therapeutic strategy for postoperative cognitive impairment.