PTEN Is Required for The Anti-Epileptic Effects of AMPA Receptor Antagonists in Chronic Epileptic Rats

Abstract

α-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR) is one of the ligand-gated ion channels for glutamate, which is an important player in the generation and spread of seizures. The efficacy of AMPAR functionality is regulated by the trafficking, synaptic targeting, and phosphorylation. Paradoxically, AMPAR expression and its phosphorylation level are decreased in the epileptic hippocampus. Therefore, the roles of AMPAR in seizure onset and neuronal hyperexcitability in ictogenesis remain to be elucidated. In the present study, we found that AMPAR antagonists (perampanel and GYKI 52466) decreased glutamate ionotropic receptor AMPA type subunit 1 (GRIA1) surface expression in the epileptic rat hippocampus. They also upregulated phosphatase and tensin homolog deleted on chromosome 10 (PTEN) expression and restored to basal levels the upregulated phosphoinositide 3-kinase (PI3K)/AKT1 phosphorylations. Dipotassium bisperoxovanadium(pic) dihydrate (BpV(pic), a PTEN inhibitor) co-treatment abolished the anti-epileptic effects of perampanel and GYKI 52466. Therefore, our findings suggest that PTEN may be required for the anti-epileptic effects of AMPAR antagonists.

Src/CK2/PTEN-Mediated GluN2B and CREB Dephosphorylations Regulate the Responsiveness to AMPA Receptor Antagonists in Chronic Epilepsy Rats

“…Considering the role of CREB in GRIA surface expression [ 47 ], it is plausible that PTEN-mediated CREB dephosphorylation may be relevant to the downregulation of GRIA1 induced by AMPAR antagonists. Consistent with our previous study [ 35 ], total GRIA1 protein level in the epileptic hippocampus was 0.71 ± 0.02-fold of control level ( t (12) = 9.3, p < 0.001 vs. control animals, Student t -test; Figure 7 A,B, Figure S6 ), which was further reduced to 0.54 ± 0.03 and 0.58 ± 0.03-fold of control level in responders by perampanel and GYKI 52466, respectively ( F (2,17) = 12.7, p < 0.001 vs. vehicle, one-way ANOVA; Figure 7 A,B, Figure S6 ). GRIA1 surface expression in the epileptic hippocampus was 0.87 ± 0.02-fold of control level ( t (12) = 4.9, p < 0.001 vs. control animals, Student t -test; Figure 7 A,C, Figure S6 ), which was also decreased to 0.54 ± 0.04 and 0.62 ± 0.04-fold of control level in responders by perampanel and GYKI 52466, respectively ( F (2,17) = 25.7, p < 0.001 vs. vehicle, one-way ANOVA; Figure 7 A,C, Figure S6 ).…”

“…GluN2B Y1472 site is dephosphorylated by PTEN [ 37 ]. Recently, we have reported that PTEN expression level in the epileptic hippocampus is lower than that in the control, and the anti-epileptic effects of AMPAR antagonists require the upregulations of its expression in responders [ 35 ]. However, we have not explored the effects of AMPAR antagonists on PTEN phosphoryaltion level in both responders and non-responders.…”

“…Immunofluorescent studies revealed that PTEN intensity was reduced to 0.56 ± 0.02-fold of control level in the epileptic hippocampus ( t (12) = 3.2, p = 0.008 vs. control animals, Student t -test; Figure 3 E,F), due to massive neuronal death [ 35 , 39 ]. Perampanel and GYKI 52,466 up-regulated PTEN intensity to 0.93 ± 0.06 and 0.92 ± 0.05-fold of control level in responders, respectively (F (2,17) = 6.18, p = 0.01 vs. vehicle, one-way ANOVA; Figure 3 E,F).…”

“…In a previous study [ 35 ], we have reported that AMPAR antagonists decrease GRIA1 surface expression in the epileptic rat hippocampus, which is abrogated by dipotassium bisperoxovanadium(pic) dihydrate (BpV(pic), a PTEN inhibitor). Considering the role of CREB in GRIA surface expression [ 47 ], it is plausible that PTEN-mediated CREB dephosphorylation may be relevant to the downregulation of GRIA1 induced by AMPAR antagonists.…”

“…Thus, it is likely that AMPAR antagonists may be more effective to inhibit spontaneous seizure activity than NMDAR antagonists. Furthermore, AMPAR antagonists (perampanel and GYKI 52,466) decrease GRIA1 surface expression in the epileptic rat hippocampus, which requires the restoring expression/activity of phosphatase and tensin homolog deleted on chromosome ten (PTEN) that drives depression of AMPAR-mediated synaptic responses following NMDAR activation [ 35 , 36 ]. Since PTEN performs GluN2B Y1472 dephosphorylation [ 37 ] and perampanel ameliorates NMDAR-mediated neuronal damage induced by ischemia [ 38 ], it is postulated that AMPAR antagonism affects NMDAR functions by regulating PTEN-mediated GluN2B Y1472 dephosphorylation, which is elusive.…”